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Integrating connectivity science and spatial conservation management of coral reefs in north-west Australia
Abstract
The geographically isolated, environmentally unique and biologically diverse coral reefs of north-west Australia are under threat from climate change and other localised human impacts. Similar to many other regions around the world, effective mitigation of these threats through ecosystem-based marine spatial planning is currently constrained by a lack of knowledge of the extent and direction of dispersal of eggs, larvae, recruits, juveniles or adults among the coral reefs (termed population connectivity). Here, we present the outcomes of a series of consultations between Marine Protected Area planners, managers and scientists aimed at facilitating the integration of this connectivity knowledge into effective management guidelines and policy in north-west Australia. Through this process, we first synthesised current knowledge of population connectivity in the fields of oceanography, larval biology and population genetics, and then identified and answered to the best of our ability the most useful questions for the spatial planning of Marine Protected Area networks. Key findings indicate that these systems are likely ecologically independent for many coral reef organisms, with hard corals exhibiting the most localised dispersal of species studied so far. Thus, given that hard corals are also the habitat forming species, and that more widely dispersing species such as fish are likely less vulnerable to small scale disturbance, we propose that no-take areas that facilitate resilience of hard coral populations should maximise biodiversity more generally. This means no-take areas that are large enough to encompass routine dispersal distances of corals (10–20 km), and are spaced at similar distances, will not only maintain self-replenishment, but also aid recovery after disturbance through connectivity between no-take areas. The results can be applied in a regional and wider context, and provide a valuable template for transfer of scientific knowledge into effective policy.
... In the same way, models can help in spotting valuable reefs presenting properties that would facilitate the recovery of disturbed areas (Hock et al., 2017). In recent years, a large literature has therefore been produced on methods to incorporate connectivity in the design of MPAs and marine reserves (e.g., Almany et al., 2009;Beger et al., 2010b;Kininmonth et al., 2011;Underwood et al., 2013;Magris et al., 2014;Andrello et al., 2015;Schill et al., 2015;Jonsson et al., 2016;Magris et al., 2016;Álvarez-Romero et al., 2018). Some conservation planning softwares, such as the widely-used Marxan 1 , can now explicitly take multi-species connectivity into account (Daigle et al., 2020), in complement of other parameters (e.g., habitat quality and diversity, species richness and conservation goals, underlying threats, risks of being impacted by catastrophic events) Schill et al., 2015;Magris et al., 2016). ...
... Following disturbances, the exchange of coral larvae between reefs plays a crucial role in repopulating damaged reefs Underwood et al., 2013;Beyer et al., 2018). Because adult corals are physically attached to their home reef, the pelagic larval phase is indeed the only moment when an exchange can occur between any two reefs. ...
... Understanding how and where those larvae disperse is essential to apprehend the dynamics and resilience of coral reefs . However, even if the GBR already benefits from vast protected zones, current Marine Protected Areas (MPA) only partially take connectivity estimates into account Kininmonth et al., 2011;Underwood et al., 2013;Magris et al., 2014). The integration of connectivity estimates in management planning is however not trivial. ...
The Great Barrier Reefs (GBR) is a treasure of biodiversity, with an immense ecological, economical and iconic value. However, this unique ecosystem is facing many threats, and is particularly suffering from global change. Management measures are therefore more than ever required to protect and restore the reefs. By reproducing both the ocean circulation and dispersal processes, biophysical models can help to inform and support such management measures. However, model outputs always come with a certain level of uncertainty, potentially impeding their reliability. Among others, the spatial resolution of ocean circulation models can affect the overall quality of their outputs. In this thesis, we use the 2D version of the multiscale coastal ocean model SLIM to assess the effect of spatial resolution on the whole modelling sequence. We hence compare the outputs of various model setups with five resolutions ranging from 250 m to 4 km. While the tidal signal is similar for all resolutions, strong discrepancies appear for simulated current velocities, especially over reefs and in their close vicinity. This in turn affects the dispersal pattern of virtual particles, leading to significant cumulative differences over multiple weeks. In a second stage, we also show that coral connectivity indicators inferred from larvae dispersal simulations vary with the resolution of the model. We hence underline the importance of using a resolution fine enough to represent the processes of interest when using models to support reef management. As a last step, we evaluate the footprint of sediments that would be released from a coal mine project adjacent to the GBR. We demonstrate that fine sediments could have far-reaching impacts on seagrass meadows, a dugong sanctuary, and important turtle nesting beaches. Throughout the thesis, we underline how processes happening at a small-scale influence in turn those happening at larger scales in coral reef environments.
... In marine systems, monitoring changes in connectivity and genetic diversity among local populations at different spatio-temporal scales are central to assessing their vulnerability to a warming planet (Kleypas et al., 2016;Oscar, 2017;Veron et al., 2009). For this reason, it is critical to integrate genetic data into conservation planning and protected area management (Gaitán-Espitia & Hobday, 2021; Underwood et al., 2013). ...
... Seascape genomic studies seek to investigate how (a)biotic factors such as environmental and biological parameters, as well as demographic processes are associated with genetic variation to identify potential drivers of population structure in the marine realm (Balkenhol et al., 2017;Riginos et al., 2016;Selmoni et al., 2020). Seascape analyses have revealed the role of the environment in shaping patterns of larval dispersal and coral population connectivity (Riginos et al., 2016;Riginos & Liggins, 2013;Selkoe et al., 2016;Thomas et al., 2015;Treml et al., 2012;Underwood et al., 2020Underwood et al., , 2009Underwood et al., , 2013. Geneenvironment association analyses (GEAs) provide a means to explore the influence of the physical environment on the genetic structure of populations (Duruz et al., 2019;Rellstab et al., 2015;Selmoni et al., 2020). ...
... In Western Australia, large-scale population connectivity studies have combined genotype data with environmental variables into integrated seascape analyses (Thomas et al., 2017(Thomas et al., , 2020Underwood, 2009;Underwood et al., 2017Underwood et al., , 2020Underwood et al., , 2018Underwood et al., , 2007Underwood et al., , 2006Underwood et al., , 2013. However, no study has explored how genetic structure patterns in these populations translate to climate change vulnerability. ...
Anthropogenic climate change has caused widespread loss of species biodiversity and ecosystem productivity across the globe, particularly on tropical coral reefs. Predicting the future vulnerability of reef‐building corals, the foundation species of coral reef ecosystems, is crucial for cost‐effective conservation planning in the Anthropocene. In this study, we combine regional population genetic connectivity and seascape analyses to explore patterns of genetic offset (the mismatch of gene‐environmental associations under future climate conditions) in Acropora digitifera across 12 degrees of latitude in Western Australia. Our data revealed a pattern of restricted gene flow and limited genetic connectivity among geographically distant reef systems. Environmental association analyses identified a suite of loci strongly associated with the regional temperature variation. These loci helped forecast future genetic offset in gradient forest and generalised dissimilarity models. These analyses predicted pronounced differences in the response of different reef systems in Western Australia to rising temperatures. Under the most optimistic future warming scenario (RCP 2.6), we predicted a general pattern of increasing genetic offset with latitude. Under the extreme climate scenario (RCP 8.5 in 2090‐2100), coral populations at the Ningaloo World Heritage Area were predicted to experience a higher mismatch between current allele frequencies and those required to cope with local environmental change, compared to populations in the inshore Kimberley region. The study suggests complex and spatially heterogeneous patterns of climate‐change vulnerability in coral populations across Western Australia, reinforcing the notion that regionally tailored conservation efforts will be most effective at managing coral reef resilience into the future.
... In the only study to investigate connectivity across the continental shelf in the Pilbara, Rosser (2016) found some evidence genetic divergence between offshore islands and the coast, although this study was based on one sampling site at each location only. In addition to these studies, Underwood et al. (2013) found evidence of genetic differentiation between Ningaloo and Dampier Archipelago, and Whitaker (2004) reported genetic divergences over short distances (between 6.5 and 155 km) along the Ningaloo coastline in two species of Acropora using allozyme electrophoresis. The south-west-flowing Holloway Current, which flows along the edge of the continental shelf and leads into the Leeuwin Current at Ningaloo (Feng et al. 2016), may likely lead to more connectivity alongshore at the continental edge from the Montebello Islands to Ningaloo. ...
... The currents on the shelf in the Pilbara are influenced by intra-seasonal oscillation, short-term wind and tidal variability, are more cyclical (Feng et al. 2016) and therefore may limit connectivity. Limited dispersal between these locations provides a greater opportunity for genetic divergences and local adaptation, as well as reduced genetic diversity due to genetic drift (Slatkin 1987), and indeed, A. tenuis in Dampier Archipelago had the lowest genetic diversity across NWA (Underwood et al. 2013). If the population structure is driven by demographic boom-and-bust cycles that characterise previously studied susceptible corals such as pocilloporids (Thomas et al. 2017) and acroporids (Underwood 2009;Underwood et al. 2009Underwood et al. , 2013Rosser 2016) rather than true oceanographic resistance, then these patterns are unlikely to be replicated across other taxa. ...
... Limited dispersal between these locations provides a greater opportunity for genetic divergences and local adaptation, as well as reduced genetic diversity due to genetic drift (Slatkin 1987), and indeed, A. tenuis in Dampier Archipelago had the lowest genetic diversity across NWA (Underwood et al. 2013). If the population structure is driven by demographic boom-and-bust cycles that characterise previously studied susceptible corals such as pocilloporids (Thomas et al. 2017) and acroporids (Underwood 2009;Underwood et al. 2009Underwood et al. , 2013Rosser 2016) rather than true oceanographic resistance, then these patterns are unlikely to be replicated across other taxa. The first goal of this study was to improve understanding of genetic connectivity in this region, using microsatellite markers, by increasing the sampling resolution and focusing on a stress-tolerant species Cyphastrea microphthalma. ...
Genetic diversity and connectivity are key factors in determining a population’s resilience to future disturbance. This is especially relevant to corals, which are in global decline due to increasing frequency and strength of thermal anomalies and severe tropical cyclones. While many studies have investigated genetic diversity and population structure in corals, they focused on species being removed at the greatest rate from coral reefs, acroporids and pocilloporids, and it is unclear whether the patterns observed in these species reflects those found in more resilient species. Here, we use microsatellite markers and two Lagrangian models with differing resolutions, to investigate population structure in a stress-tolerant coral survivor Cyphastrea microphthalma, Family Merulinidae, along the north-western Australian coastline. We found evidence of four genetic clusters with some level of admixture among them. However, while there was evidence of population structure within the intensively sampled Pilbara region, the patterns of connectivity differed to those reported previously. WA populations of C. microphthalma were also characterised by lower levels of genetic diversity at higher latitudes. High- and moderate-resolution Lagrangian models did not significantly predict regional-scale genetic connectivity across the Pilbara and Ningaloo (500 km). Although the high-resolution model explained an order of magnitude more genetic variation, suggesting model resolution and resolving coastal processes are important. Over broad spatial scales (nearly 2000 km), all moderate-resolution model particle release durations significantly predicted the genetic differentiation, although over-water distance best-predicted the genetic distance across this spatial scale. This study improves the understanding of connectivity in this region by focusing on a stress-tolerant species incorporating a spatially more intensive sampling effort than previous coral studies. It also shows that further development of Lagrangian models is required, such as inclusion of multi-generational stepwise models and larval behaviour, to improve predictions of connectivity for this coral species in this region.
... Due to the complex oceanography between Indonesia and north-western Australia, the potential oceanographic drivers of dispersal and associated dispersal patterns in this region are not yet clear (Underwood et al., 2013). Nonetheless, the large network of reefs and shoals between Indonesia and north-western Australia are thought to act as dispersal 'stepping-stones' for species with longer propagule precompetency periods or those with long-term active dispersal capabilities (Underwood et al., 2013). ...
... Due to the complex oceanography between Indonesia and north-western Australia, the potential oceanographic drivers of dispersal and associated dispersal patterns in this region are not yet clear (Underwood et al., 2013). Nonetheless, the large network of reefs and shoals between Indonesia and north-western Australia are thought to act as dispersal 'stepping-stones' for species with longer propagule precompetency periods or those with long-term active dispersal capabilities (Underwood et al., 2013). However, the large expanse of ocean, and the complex circulation patterns in this region, may act as dispersal barriers for species with limited active dispersal capacities and short propagule precompetency periods, such as corals. ...
... Therefore, species and populations that already have limited dispersal opportunities will be more affected by weakening ocean currents than those which are less restricted by present-day dispersal barriers (Sorte, 2013). Evidence suggests that dispersal facilitated by the ITF and the Leeuwin Current predominantly occurs via a series of 'stepping-stones' from reef to reef over multiple generations (Knittweis et al., 2009;Underwood et al., 2013). As weaker currents take longer to transport propagules from an upstream to a downstream location, the weakening of the ITF and Leeuwin Current is likely to decrease the geographical distance that can be successfully traversed within the propagule pre-competency period (Underwood, 2009). ...
Aim: The dispersal and distribution patterns of many marine organisms are driven by oceanographic conditions, which are influenced by global climate. Climate-driven oceanographic changes are thus likely to result in biogeographical changes. We assess how recent and predicted oceanographic changes affect the dispersal capacities and distributions of ecologically important (especially habitat-forming) marine organisms. Location: We include studies from tropical, temperate and sub-polar regions to draw globally relevant conclusions. Methods: We review biogeographical, biological and oceanographic studies to critically evaluate emerging trends in biogeographical responses to climate-driven oceanographic changes, and predict how future changes will affect marine ecosystems. Results: Many oceanic dispersal pathways are being altered by climate change. These changes will affect marine ecosystems by differentially affecting the replenishment potential and connectivity of key habitat-forming species. In particular, the length of propagule pre-competency periods, propagule behaviour and the geographical distance between areas of suitable habitat will be critical in determining how oceanographic changes affect the pattern and success of dispersal events, including the likelihood of species experiencing poleward range shifts in response to a warming climate. Main conclusions: Future climate-driven oceanographic changes are likely to strengthen or weaken different oceanic dispersal pathways, which will either increase or decrease the potential for dispersal and connectivity in various marine taxa according to the interaction between the local oceanographic, geographical and taxon-specific biological factors. A key focus for future work should be the development of fine-scale near-shore ocean circulation models that can be used to assess the dispersal response of key marine taxa under various marine climate change scenarios.
... The high percentage of the live coral cover at this core zone has also supported the spillover function to the other zones. This condition further supports the role of the core zone as a larvae source as it allows connectivity to occur, considering that the ability to repair (resilience) from coral reef within a region depends on the connectivity efficiency between coral reef in that conservation area (Underwood et al., 2013). The low percentage level of coral cover at the utilization zone (Figure 4.) is expected to recover in the years to come, and new coral recruitment could be derived from the other zones that have good level of coral cover percentage. ...
... Hence, this shows us that the locations with low percentage of coral cover are not always followed by low rate of coral recruitment abundance, De Leon et al. (2013) also suggested that the locations with low percentage of coral cover are not always run out of larvae supply. Those zones might likely obtain their larvae supplies from the other zones, considering that the transport of larvae could occur from one location to the other through ocean currents (Underwood et al., 2013). ...
The continuity of coral reef ecosystem highly depends on the new coral larvae recruitment process. Hence, the information regarding distribution, the abundance of corals, and its relation to other variables are highly important in that ecosystem management. Research was conducted at nine stations represented each zone at the conservation area of Kapoposang Marine Tourism Park (TWP Kapoposang). This research aims at seeking for spatial variations of the abundance of coral recruitment at three primary zones monitored (core zone, sustainable fishing zone and utilization zone) and we further identified its relations with spatial variation of herbivorous fishes abundance and coral cover’s condition at those zones. The coral recruitment observation employed transect quadrat sampling method with size of 1x1 meter and 10 times repetition at a similar depth, and the coral recruitment abundance measurement in natural habitat based on the amounts of juvenile corals has been defined as coral colony with size of ≤10 cm. Overall, this research has found 534 coral juveniles consisted of 19 genera and 7 families, and the average of juvenile coral density stood at 5.34±4.45 SE.m-2. The coral reef recruitment category at TWP Kapoposang could be classified as high and its abundance spatial distribution showed no significant differences between each zone, as well as not influenced by either herbivorous fish abundance variable or the percentage of live coral cover.
... At present, the extent of physical and ecological connectivity among WA reefs is unknown, but as the majority of coral larvae generally settle within one week of spawning [14,15], Underwood et al. [16] hypothesised that coral systems in north-west Australia will be primarily replenished each generation by recruits that are produced locally, with coral dispersal distances ranging from~10 km to~50 km. This has also been observed along the eastern seaboard (e.g. between the Great Barrier Reef and higher latitude reefs like Lord Howe Island) where evidence of local recruitment has been observed [17,18]. ...
... Moreover, the basic Lagrangian simulations used did not allow for particle dilution or mortality, which has been shown to reduce larval (simulated particle) movement by up to 9-fold [35]. Entrapment and early settlement on natal or nearby reefs [16,36], mortality, predation and dilution prevent much long distance larval transport [37], and the ecological likelihood of external recruitment from sources beyond 50 km is expected to be limited [38]. Studies using genetic, oceanographic, or modelling techniques to infer coral dispersal distances have found that larvae routinely disperse 10s of kms, with dispersal >50-100s of kms generally restricted to occasional genetic connections (see summary in Jones et al. 2009). ...
In 2011 the first recorded bleaching event for the high latitude Houtman Abrolhos Islands (HAI) coral communities was documented. This bleaching event highlighted the question of whether a supply of 'heat tolerant' coral recruits from the tropical north would be sufficient to provide a level of resistance for these reefs to future warming events. Using Lagrangian modelling we showed that due to its regional isolation, large-scale larval input from potential tropical northern source populations to the HAI is unlikely, despite the southward flowing Leeuwin current. Successful recruitment to artificial substrates was recorded following the bleaching event. However, this was negligible (0.4 ± 0.1 recruits per tile) compared to 2013 post impact recruitment (128.8 ± 15.8 recruits per tile). Our data therefore provides preliminary evidence suggesting that the connectivity of the HAI with coral communities in the north is limited, and population maintenance and recovery is likely driven primarily by self-recruitment. Given the low thermal tolerance of the HAI coral communities, the dominance of Acropora, and the apparent reliance on self-recruitment, an increased frequency of thermally anomalous conditions at the HAI (such as experienced in 2011) has the potential to reduce the long-term stability of the HAI coral populations and species that depend upon them.
... 28! influencing connectivity and dispersal patterns (Munday et al., 2009a, e.g. Kendall et al., 2013, Underwood et al., 2013. However, we predict that coral reef fish larvae at high latitudes are likely to grow faster and settle earlier with small increases in ocean temperature (as predicted by existing models), but at lower latitudes the thermal optimum may be exceeded with global warming leading to slower growth and extended larval duration. ...
... Recent studies have used the results of this meta-analysis to predict that PLDs will be reduced and larval survival will increase in a warming ocean, consequently, influencing connectivity and dispersal patterns (Munday et al., 2009a, e.g. Kendall et al., 2013, Underwood et al., 2013. Predictions of increased larval survival and shorter PLDs may be inaccurate, especially for tropical species, if they do not account for the shape of the thermal reaction norm in PLD above the range of natural variation and incorporate the possible effects of reduced food supply (Steinacher et al., 2010). ...
... Similarly, identification and mapping of habitats and of the connectivity of the landscape matrix for a given species are critical components for the conservation of populations and species (Underwood et al., 2013). In turn, the degree to which a landscape facilitates or limits movement of individuals between habitats is tightly linked with individual gene flow (Schoville et al., 2012). ...
We apply an environmental domains approach to identify environmentally heterogeneous characteristics defining a landscape matrix. We built environmental layers for national, regional, and local scales, considering the different scales studies can have. We used a numerical classification of explicit spatial layers and performed a multivariate classification. Based on the domains obtained, we mapped the landscape’s climatic heterogeneity and identified a comprehensive set of environmental variables that defined the landscape matrix at each scale. We specifically tested our approach for its suitability to define a sampling strategy for a landscape genetics study, using as focal species the rodent Heteromys pictus. Namely, from the domains obtained at the local scale, we selected sampling localities that comprised the broadest habitat heterogeneity, which we corroborated in the field. The landscape matrix thus generated was used with genetic data previously obtained for H. pictus. Our approach allowed identification of environmental variables significantly associated with dispersal (gene flow) of H. pictus individuals in their natural habitat. We demonstrate its adequacy to efficiently determine sampling localities —or landscape sites— that encompass the highest environmental heterogeneity, in explored and unexplored landscapes, enabling rapid identification of localities and their environmental characteristics where in situ information is scarce.
... Habitat formers such as corals, seagrass and algae which support high biodiversity through their structure and food provision were least represented in this analysis with fish contributing to over 50% of the observations, a similar finding identified from the synthesis of Keyse et al. (2014) which only focused on animals. Future research should target these habitat forming species considering they are a key focus of management and conservation measures, especially in the face of rapidly changing environment (Underwood et al., 2013;Bulleri et al., 2018;Babcock et al., 2019). Genetic structure data were available for most ecoregions, although it was not evenly distributed (Keyse et al., 2014), and a number of areas either had no samples or were poorly represented e.g. ...
The spatial genetic structure of marine organisms is related to dispersal and life-history traits, historical processes, current oceanographic connectivity and habitat features. Here, we assessed the relative importance of these factors for the genetic structure of a broad range of marine species in the Indo Australian Archipelago (IAA). We collated published data on 99 marine species from eight taxonomic groups (ascidians, fishes, molluscs, crustaceans, echinoderms, corals, reptiles, and marine plants) and used generalized linear models (GLMs) to estimate the best predictors of genetic structure. Genetic structure was characterized by FST and the number of genetic clusters over the study area. Predictors tested were: the type of genetic markers; the number of marine ecoregions which are a proxy for habitat variation, historical processes and oceanographic features; species dispersal-related traits (i.e., pelagic larval duration-PLD, adult life habit, reproductive strategy, and egg type); and geographic distance separating populations. The genetic structure of marine species across the IAA was best predicted by traits related to dispersal of larvae or propagules and the mobility of adults; and the number of marine ecoregions sampled not distance was also an important predictor, especially in sedentary and free-swimming species. Our findings highlighted the importance of these key traits to help guide decision-making in spatial management and conservation. There were still many gaps in our understanding of genetic structure, both spatially and within certain taxa, and we recommended future genetic studies focus on habitat-forming taxa and sample sites that are representatively nested in each ecoregion within a marine province or a marine realm, over the spatial extent of the IAA.
... Regardless of the mechanism, the links between recruitment and adult abundance over different spatial scales suggests high rates of larval retention within the Dampier Archipelago during our study period. These findings are supported by connectivity models for the region, which found high rates of larval retention within the Dampier Archipelago most years (dispersal distances <10 km) (Kool and Nichol 2015;Feng et al., 2016;Boschetti et al., 2020), and genetic studies which found generally low levels of genetic similarity between corals in the Dampier Archipelago and those located 130 km to the southwest at Ningaloo Reef (Underwood et al., 2013;Evans et al., 2018). ...
Understanding ecological processes that shape contemporary and future communities facilitates knowledge-based environmental management. In marine ecosystems, one of the most important processes is the supply of new recruits into a population. Here, we investigated spatiotemporal variability in coral recruitment at 15 reefs throughout the Dampier Archipelago, north-western Australia between 2015 and 2017 and identified the best environmental predictors for coral recruitment patterns over this period. Large differences in recruitment were observed among years with the average density of recruits increasing by 375% from 0.017 recruits cm⁻² in 2015 to 0.059 recruits cm⁻² in 2017. Despite differences in recruitment among years, the rank order of coral recruit density among reefs remained similar among years, suggesting that spatial variation in recruitment within the Dampier Archipelago is partly deterministic and predictable. The density of coral recruits was best explained by percent cover of live corals at both local (within 5m) and meso-scales (within 15km), water turbidity and an oceanographic model that predicted larval dispersal. The highest density of coral recruits (∼0.13 recruits cm⁻² or 37 recruits per tile) occurred on reefs within sub-regions (15 km) with greater than 35% coral cover, low to moderate turbidity (KD490 < 0.2) and moderate to high modelled predictions of larval dispersal. Our results demonstrate that broad-scale larval dispersal models, when combined with local metrics of percent hard coral cover and water turbidity, can reliably predict the relative abundance of coral recruits over large geographical areas and thus can identify hotspots of recruit abundance and potential recovery following environmental disturbances; information that is essential for effective management of coral reefs.
... Knowledge of larval connectivity is fundamental to spatial planning for coral reef conservation because it is a key ecological driver of population replenishment and recovery after disturbance (Cowen & Sponaugle, 2009). There is currently limited knowledge of metapopulation dynamics of most reefs and species, and even less understanding of how to integrate connectivity information into ecosystem management (Magris et al., 2014;Underwood, Wilson, Ludgerus, & Evans, 2013). Because genetic divergence among individuals and populations accumulates over multiple generations through genetic drift and differential selection when inter-breeding is restricted, spatial analysis of genetic structure is a pivotal method for measuring connectivity (Hedgecock, Barber, & Edmands, 2007). ...
Management strategies designed to conserve coral reefs threatened by climate
change need to incorporate knowledge of the spatial distribution of inter- and intraspecific
genetic diversity. We characterized patterns of genetic diversity and connectivity
using single nucleotide polymorphisms (SNPs) in two reef-building corals
to explore the eco-evolutionary processes that sustain populations in north-west
Australia. Our sampling focused on the unique reefs of the Kimberley; we collected
the broadcast spawning coral Acropora aspera (n = 534) and the brooding coral Isopora
brueggemanni (n = 612) across inter-archipelago (tens to hundreds of kilometres), inter-
reef (kilometres to tens of kilometres) and within-reef (tens of metres to a few
kilometres) scales. Initial analysis of A. aspera identified four highly divergent lineages
that were co-occurring but morphologically similar. Subsequent population analyses
focused on the most abundant and widespread lineage, Acropora asp-c. Although
the overall level of geographic subdivision was greater in the brooder than in the
spawner, fundamental similarities in patterns of genetic structure were evident. Most
notably, limits to gene flow were observed at scales <35 kilometres. Further, we observed
four discrete clusters and a semi-permeable barrier to dispersal that were geographically
consistent between species. Finally, sites experiencing bigger tides were
more connected to the metapopulation and had greater gene diversity than those
experiencing smaller tides. Our data indicate that the inshore reefs of the Kimberley
are genetically isolated from neighbouring oceanic bioregions, but occasional dispersal
between inshore archipelagos is important for the redistribution of evolutionarily
important genetic diversity. Additionally, these results suggest that networks of
marine reserves that effectively protect reefs from local pressures should be spaced
within a few tens of kilometres to conserve the existing patterns of demographic and
genetic connectivity.
... Knowledge of larval connectivity is fundamental to spatial planning for coral reef conservation because it is a key ecological driver of population replenishment and recovery after disturbance (Cowen & Sponaugle, 2009). There is currently limited knowledge of metapopulation dynamics of most reefs and species, and even less understanding of how to integrate connectivity information into ecosystem management (Magris et al., 2014;Underwood, Wilson, Ludgerus, & Evans, 2013). Because genetic divergence among individuals and populations accumulates over multiple generations through genetic drift and differential selection when inter-breeding is restricted, spatial analysis of genetic structure is a pivotal method for measuring connectivity (Hedgecock, Barber, & Edmands, 2007). ...
Abstract Management strategies designed to conserve coral reefs threatened by climate change need to incorporate knowledge of the spatial distribution of inter‐ and intra‐specific genetic diversity. We characterized patterns of genetic diversity and connectivity using single nucleotide polymorphisms (SNPs) in two reef‐building corals to explore the eco‐evolutionary processes that sustain populations in north‐west Australia. Our sampling focused on the unique reefs of the Kimberley; we collected the broadcast spawning coral Acropora aspera (n = 534) and the brooding coral Isopora brueggemanni (n = 612) across inter‐archipelago (tens to hundreds of kilometres), inter‐reef (kilometres to tens of kilometres) and within‐reef (tens of metres to a few kilometres) scales. Initial analysis of A. aspera identified four highly divergent lineages that were co‐occurring but morphologically similar. Subsequent population analyses focused on the most abundant and widespread lineage, Acropora asp‐c. Although the overall level of geographic subdivision was greater in the brooder than in the spawner, fundamental similarities in patterns of genetic structure were evident. Most notably, limits to gene flow were observed at scales
... Carbonate sands, also referred to as calcareous sediments, are commonly used for coastal engineering in regions such as the West Australia Continental Platform (Underwood et al. 2013), South China Sea (Wang et al. 2011(Wang et al. , 2017, and Bass Strait (Murff 1987). Carbonate sand can be crushed more easily than quartz and silica sands due to the nature of their internal pores (Coop et al. 2004;Yu 2017;Xiao et al. 2019b). ...
Time-dependent deformation of crushable soils attributable to particle breakage could dominate the postconstruction stability of high rockfill dams and pile foundations. The evolutionary trends of the volumetric strain, particle size distribution (PSD) and particle breakage of carbonate sands with 10% fines content for various loading durations and vertical stress levels are investigated by performing a series of one-dimensional compression tests. Loading durations ranging from 1 to 10,000 minutes, vertical stress levels ranging from 200 to 3,200 kPa and fines content percentages ranging from 0 to 20% are considered. The results indicate that the increased loading duration in the initial stage has a significant effect on the volumetric strain; however, as the loading duration increases, this effect gradually decreases. In addition, the PSD curve shifts upward as the loading duration increases, indicating that the amount of particle breakage increases accordingly. Both the loading duration and the vertical stress can induce PSD changes in carbonate sands. Empirical equations are proposed to describe the relationship between the relative particle breakage index and the loading duration as well as the relationship between the relative particle breakage index and the vertical stress.
... The current patterns can have a major effect on the direction and distance of larval travel from released until settlement on an appropriate substrate (Gleason and Hofmann 2011). It has been noted that flows play an essential role in maintaining connectivity between coral reef populations (Botsford et al. 2009;Underwood et al. 2013). The distribution of larvae is also influenced by the time of release and the duration of the pelagic phase (Cowen and Sponaugle 2009), as well as the characteristics of the sink or the settlement area (Tay et al. 2012). ...
Umar W, Tassakka ACMAR, Jompa J. 2019. High genetic connectivity in a scleractinian coral (Lobophyllia corymbosa) around Sulawesi, Indonesia. Biodiversitas 20: 3484-3492. The life cycle of scleractinian corals begins with a pelagic larval phase subject to the influence of currents, with the potential to disperse propagules over vast geographical distances. We investigated the mitochondrial COI genome to investigate genetic population structure and potential biophysical barriers (in particular water mass movements) that could affect connectivity between populations in the seas around Sulawesi, in the Indonesian Coral Triangle. Lobophyllia corymbosa was selected as representative of corals with a broadcast spawning reproductive strategy and relatively long Pelagic Larval Dispersal (PLD) period. Analysis of mtDNA sequences from 103 colonies collected at depths of 3 to 10 meters in 4 locations (Manado, Toli-Toli, Spermonde, and Wakatobi) resulted in FST = 0.00632, indicating no genetic isolation or significant differentiation. The tendency towards genetic homogeneity across the entire population indicates that gene flow has been maintained, most likely through widespread dispersal of propagules within the study area. The dominant surface flow directions recorded during the reproductive period of this species provide support for this gene flow model, as the currents could enable dispersal and recruitment patterns maintaining connectivity between L. corymbosa populations around Sulawesi.
... To inform management initiatives over much larger spatial and temporal scales, mapping of coral reef distributions should include regions suitable for reef formation into the next century, considering projected changes in disturbance regimes, substrata availability, ocean temperatures, acidity and available light (Greenstein and Pandolfi 2008;Edmunds et al. 2014;Muir et al. 2015;Anthony 2016;van Woesik and Cacciapaglia 2018;Wall et al. 2018). Studies of larval connectivity should also consider the much larger distances over which larvae can occasionally disperse and recruit over decadal time steps, to inform initiatives aiding the exchange of larvae and genotypes across regions of WA (Underwood et al. 2013;Magris et al. 2014;Edmunds et al. 2018). Connectivity patterns along WA's coastline are driven primarily by the southerly flow of major currents along the northwest shelf to North West Cape at Ningaloo Reef and then onto the subtropical and temperate reefs in the Leeuwin Current (Domingues et al. 2007;Pattiaratchi 2007;D'Adamo et al. 2009;Feng et al. 2016). ...
Western Australia’s coral reefs have largely escaped the chronic pressures affecting other reefs around the world, but are regularly affected by seasonal storms and cyclones, and increasingly by heat stress and coral bleaching. Reef systems north of 18°S have been impacted by heat stress and coral bleaching during strong El Niño phases and those further south during strong La Niña phases. Cumulative heat stress and the extent of bleaching throughout the northern reefs in 2016 were higher than at any other time on record. To assess the changing regime of disturbance to reef systems across Western Australia (WA), we linked their site-specific exposure to damaging waves and heat stress since 1990 with mean changes in coral cover. Since 2010, there has been a noticeable increase in heat stress and coral bleaching across WA. Over half the reef systems have been severely impacted by coral bleaching since 2010, which was further compounded by cyclones at some reefs. For most (75%) reef systems with long-term data (5–26 yrs), mean coral cover is currently at (or near) the lowest on record and a full recovery is unlikely if disturbances continue to intensify with climate change. However, some reefs have not yet experienced severe bleaching and their coral cover has remained relatively stable or increased in recent years. Additionally, within all reef systems the condition of communities and their exposure to disturbances varied spatially. Identifying the communities least susceptible to future disturbances and linking them through networks of protected areas, based on patterns of larval connectivity, are important research and management priorities in coming years while the causes of climate change are addressed.
... Carbonate sands, which are widely distributed in coral reefs and seashores in regions such as the South China Sea [11,75], Red Sea [56], West Australia Continental Platform [71], and Bass Strait [50] are commonly used for road embankments and airport runways in offshore geotechnical engineering. Crushed carbonate sands led to an unexpected free fall of the pile during pile driving for the Lavan petroleum platform of Iran in 1986 [2]. ...
Quasi-static and dynamic compression tests are conducted on carbonate sand using a Material Testing System and a modified split Hopkinson pressure bar, respectively. The particle size distributions (PSDs) of carbonate sand before and after loading are measured via laser diffractometry. The stress–strain curves demonstrate that the carbonate sand investigated in this study exhibits strain rate effects. The stress–strain curves show slightly different features for quasi-static and dynamic loading conditions. The particle breakage extent, which is quantified from the PSDs of the samples before and after loading, is investigated at different stress levels and input energy values. The breakage efficiency under the quasi-static loading condition is higher than that under the dynamic loading condition. As a result, the particle breakage extent is higher under the quasi-static loading condition than under the dynamic loading condition at the same stress level. Furthermore, the particle breakage modes are highly dependent on stress. The breakage modes under the dynamic loading condition change from attrition and abrasion at low stress levels, resulting in the appearance of plateaus in the grading curves, to fracture at high stress levels, resulting in the disappearance of plateaus in the grading curves.
Graphical abstract
... The remote coral atolls in the tropical north-east Indian Ocean of northwest Australia are physically isolated from other coral reefs by hundreds of kilometres of generally slow-moving open oceanic water ( Fig. 1), suggesting the strong potential for reproductive isolation and consequent local genetic diversification. Evidence from two hard corals and a coral reef fish support this expectation, indicating significant genetic differences among atolls (Underwood et al., 2009;Underwood et al., 2012;Underwood et al., 2013). Although many of the marine species of invertebrates, fish and corals present in these offshore waters have a broad Indo-West Pacific distribution, studies have demonstrated considerable divergence from congeneric populations further north and east (Horne et al., 2011;Imron et al., 2007;Otwoma and Kochzius, 2016;Underwood et al., 2018;Veilleux et al., 2010) The coral reefs of northwest Australia are regarded as a major centre of coral biodiversity (Wilson, 2013), but little is known about the evolutionary forces that have shaped the biodiversity of most taxa on these atolls. ...
Coral reef health and biodiversity is under threat worldwide due to rapid climate change. However, much of the inter- and intra-specific diversity of coral reefs are undescribed even in well studied taxa such as fish. Delimiting previously unrecognised diversity is important for understanding the processes that generate and sustain biodiversity in coral reef ecosystems and informing strategies for their conservation and management. Many taxa that inhabit geographically isolated coral reefs rely on self-recruitment for population persistence, providing the opportunity for the evolution of unique genetic lineages through divergent selection and reproductive isolation. Many such lineages in corals and fish are morphologically similar or indistinguishable. Here, we report the discovery and characterisation of cryptic lineages of the Wolf Cardinalfish, Cheilodipterus artus, from the coral atolls of northwest Australia using multiple molecular markers from mitochondrial (CO1 and D-loop) and nuclear (microsatellites) DNA. Concordant results from all markers identified two highly divergent lineages that are morphologically cryptic and reproductively isolated. These lineages co-occurred at daytime resting sites, but the relative abundance of each lineage was strongly correlated with wave exposure. It appears, therefore, that fish from each lineage are better adapted to different microhabitats. Such cryptic and ecologically based diversity appears to be common in these atolls and may well aid resilience of these systems. Our results also highlight that underwater surveys based on visual identification clearly underestimate biodiversity, and that a taxonomic revision of the Cheilodipterus genus is necessary.
... As a next step beyond ensuring that the relevant questions are asked, it is important that the products of the research are distilled and communicated to management agencies, industry and other stakeholders to ensure that informed decisions are made (Underwood et al. 2013). Having good relationships between external scientists and management agencies is critical to ensuring that relevant and new knowledge is readily available to managers for uptake. ...
Given limited funding and increasing pressures on our natural resources it is becoming ever more critical that science be directed at improving our understanding and management of priority issues. This relies on dialogue and alignment between researchers and managers to ensure that appropriate questions are asked and the answers incorporated in robust and transparent decision-making processes which should include relevant evidence-based science. We used a prioritisation framework as a tool to bring managers and scientists together to discuss and agree on current priorities for research on marine mammals in Western Australia, including posing relevant questions. Eight species were identified as high priorities for fundamental research, including three dolphin species (Australian humpback, snubfin and common dolphin), three baleen whale species (Antarctic and pygmy blue and dwarf minke whale), the Australian sea lion and the dugong. The pressures we evaluated resulted in a priority need for research to better understand and mitigate impacts across a range of species, including noise pollution from shipping and vessel activity, climate change and fishing by-catch. Scientists and managers agreed on a set of topics and associated research questions for the high-priority species that would best inform ongoing conservation and management of marine mammals in Western Australia and that would have broad applicability nationally and globally. We provide an example of how these priorities can be used to develop a research program with targeted funding. Overall, this process has demonstrated the value of bringing scientists and managers together with a tool that allows them to jointly determine priorities and research questions.
... One well recognised approach to improve information flow and knowledge transfer among academics and resource managers is through the co-production of knowledge, whereby managers actively participate in scientific research programs (e.g. Ceccarelli et al. 2011;Hoey et al. 2011;Underwood et al. 2013). Under this approach, decision-makers are actively engaged in research programs from the outset, ensuring that the information requirements of both groups are discussed and jointly understood before the execution of a study. ...
Integration of scientific information into the decision-making process for the management of marine resources remains a significant challenge, with the inaccessibility of primary scientific literature to environmental practitioners identified as a key limiting factor. Here, we quantify the use of primary scientific literature in environmental management plans, and explore potential barriers to the efficient integration of such scientific information into the decision-making process. Through a case study of coral dominated Marine Protected Areas (MPAs) spanning three countries (Australia, Kenya and Belize), we find that primary scientific literature represents only 14% of information cited in management plans. Such a low proportion is likely to be symptomatic of several issues regarding the accessibility of primary scientific literature to MPA managers, such as: 1. Long publication times for articles (average 40.2 ± 1.8 months); 2. Subscription-only access (up to 56% of articles behind paywalls); and/or 3. Poor articulation of management implications (only 19% of articles provided clear outcomes relevant to management). Such impediments can undermine the adaptive governance of MPAs, so we suggest improvements to knowledge transfer among scientists and managers via a diversity of approaches including knowledge brokers, boundary organisations, knowledge co-production and management-orientated summaries in research articles.
... More than 800 neritic teleost species are known from the Kimberley shelf (Fox and Beckley, 2005) and a high diversity of coastal and coral reef-associated species inhabit near-shore waters (Travers et al., 2010). Information gaps for the Kimberley relate to the reproductive patterns (e.g., spawning areas, timing) of key teleost species as well as larval dispersal pathways in coastal, shelf and oceanic waters (Brewer et al., 2007;Underwood et al., 2013) though inferences can be made from a recent oceanographic modelling study examining dispersal of coral larvae on the north-west shelf (Feng et al., 2016). ...
In the eastern Indian Ocean, the Kimberley region off north-western Australia is characterised by a wide continental shelf, complex coastal topography and very large tides (>10 m). Diversity of fishes is high although little is known about the distribution of their larvae in this dynamic region. This study investigated spatial variation in ichthyoplankton assemblages along four coastal-oceanic transects and related the results to tidal cycles and other environmental variables. Larvae representing 92 neritic and 21 mesopelagic teleost families were collected; this far exceeds the diversity described for other comparable tropical continental shelf and oceanic systems. Distinct ichthyoplankton assemblages characterised inner shelf (Engraulidae and Gobiidae were dominant families), outer shelf / slope (mixed neritic and mesopelagic taxa) and oceanic waters (mesopelagic taxa, particularly Myctophidae, Gonostomatidae and Phosichthyidae), and were correlated with changes in environmental variables (water depth, seawater density, mixed layer depth and zooplankton). The spring-neap tidal cycle and subsequent tides (same stations sampled 12 h apart) had no significant influence on larval fish assemblages. Coastal waters were delineated by a density front and larval fish assemblages were significantly different from offshore assemblages. This study provides new insights into the pelagic ecosystem in the tropical eastern Indian Ocean and contributes to the understanding of the role of environmental variables and physical forcing in the structuring of larval fish assemblages.
... These reefs play an integral role in sustaining deep-water ecosystem diversity (Campbell et al. 2010) providing vital habitat for commercially important fish stocks (Foley et al. 2009) and included within both the Natura 2000 and OSPAR networks of MPAs. Furthermore, although these reefs occur beyond the immediate action area of the SIMCelt project, their sensitivity to anthropogenic impacts (Rogers 1999;Mormede and Davies 2001) and protected status under the EU Habitats Directive they are an important consideration for the MSP process and provide a regionally important example of the requirement for plans to consider the potential "far-field" impacts of intensified maritime activity on sensitive and ecologically significant habitat (Underwood et al. 2013). ...
The purpose of this report is to initiate an investigation into the challenges and opportunities
associated with the implementation of Maritime Spatial Planning (MSP) in transboundary areas of the Celtic
Seas. As a foundation of understanding, this document provides an overview of the territiorial boundaries
and key environmental characteristics of the region; major maritime activities; key sectoral and socioeconomic
trends and pressures and relevant European policy and legislation with a bearing on MSP and
transboundary working. The report also aims to give relevant insight on pre-existing cross-border
stakeholder fora providing a basis for continued cooperation and engagement on maritime issues and a
summary of previous transboundary maritime spatial planning initiatives for the Celtic Seas region.
... Similarly, the size and timing of management actions such as fishing closures would have different consequences for recovery in each species. Given the importance placed on conservation of ecosystem engineers in managing marine ecosystems more broadly 68,69 then clearly any measures that capture the breadth of life histories and connectivity for these two corals will undoubtedly have consequences for the persistence of a broad suite of seamount species. ...
Ecological processes in the deep sea are poorly understood due to the logistical constraints of sampling thousands of metres below the ocean’s surface and remote from most land masses. Under such circumstances, genetic data provides unparalleled insight into biological and ecological relationships. We use microsatellite DNA to compare the population structure, reproductive mode and dispersal capacity in two deep sea corals from seamounts in the Southern Ocean. The solitary coral Desmophyllum dianthus has widespread dispersal consistent with its global distribution and resilience to disturbance. In contrast, for the matrix-forming colonial coral Solenosmilia variabilis asexual reproduction is important and the dispersal of sexually produced larvae is negligible, resulting in isolated populations. Interestingly, despite the recognised impacts of fishing on seamount communities, genetic diversity on fished and unfished seamounts was similar for both species, suggesting that evolutionary resilience remains despite reductions in biomass. Our results provide empirical evidence that a group of seamounts can function either as isolated islands or stepping stones for dispersal for different taxa. Furthermore different strategies will be required to protect the two sympatric corals and consequently the recently declared marine reserves in this region may function as a network for D. dianthus, but not for S. variabilis.
... The reproductive output is the first of several processes for determining connectivity among populations (Cowen and Sponaugle 2009;Treml et al. 2012), whereas the likelihood of larval subsidy to adjacent (un)protected areas is low or insignificant if the reproductive output is low (or null). Although the opposite is not necessarily true, we argue that single-and multispecies RHs, either defined by spawning biomass or potential fecundity, are potentially good larval sources that, in addition to adult movement, may contribute to replenish and sustain natal and neighboring areas and populations (Underwood et al. 2013). Such source habitats are the "keys" to persisting, viable fish populations (Figueira and Crowder 2006). ...
Postsettlement spillover from marine protected areas (MPAs) can support adjacent fished populations and has been subject of many scientific studies. The larval subsidy effect, on the contrary, is more challenging to study and less demonstrated, although it, arguably, provides key benefits for fisheries. We modeled and predicted the spatial distribution of fish spawning biomass and fecundity across a temperate insular MPA network (Azores archipelago, Northeast Atlantic) and identified potential single- and multispecies reproductive habitats (RHs) in shallow reefs. Reproductive strategies or skewed sex ratios influenced spatial patterns of potential spawning biomass and fecundity. Predicted multispecies RHs covered 5%–20% of the studied reef habitat. Given their potentially high reproductive output, we argue that such sites should be considered in marine conservation planning to increase chances of achieving fisheries and conservation benefits. Spatial patterns of the reproductive output may function as sur...
... In the southern Pilbara, a closer proximity to oceanic waters appears to be an important positive driver of high fish diversity (Hutchins et al., 1996; Hutchins, 2001). Whilst coastal coral reefs of the Pilbara are adapted to high levels of natural disturbance (cyclones, tidal currents; Gilmour et al., 2006), corals can be vulnerable to additional anthropogenic disturbances due to limited demographic and genetic replenishment (Underwood et al., 2013). That is, they rely on their own genetic diversity to adapt to environmental change. ...
... That leaves a fairly wide range of choices: there is controversy about whether single large reserves are more effective than several smaller ones of the same total area, whether edge effects diminish their efficacy, and whether closely spaced reserves are more effective than distantly spaced ones (Mous-114 A. Moustakas: A quantitative conservation conflict attempt takas and . It is acknowledged that dispersal is a key factor in designing MPAs (Coleman, 2013;Underwood et al., 2013). The reasons behind dispersal being a key factor (Lewis et al., 2013) are that (i) MPAs should be large enough so that adults can stay long enough inside them, but how large is large enough is clearly related to dispersal potential; (ii) MPAs should be close enough so that larvae can move between them, but how close is close enough is also related to dispersal potential. ...
Protected areas are an important conservation measure. However, there are controversial findings regarding whether closed areas are beneficial for species and habitat conservation as well as landings. Species dispersal is acknowledged as a key factor for the design and impacts of closed areas. A series of agent based models using random diffusion to model fish dispersal were run before and after habitat protection. All results were normalised without the protected habitat in each scenario to detect the relative difference after closing an area, all else being equal. Results show that landings of species with short dispersal ranges will take longer to reach the levels of pre Marine Protected Areas (MPAs) establishment than landings of species with long dispersal ranges. Further the establishment of an MPA generates a higher relative population source within the MPA for species with low dispersal abilities than for species with high dispersal abilities. Results derived here show that there exists a win-win feasible scenario that maximises both fish biomass as well as fish catches.
... Criteria for assessing connectivity include rules to achieve contiguous reserve systems, contiguous areas of distribution for the focal species, or approaches where spatial criteria are incorporated in the objective function to be optimized (Alagador et al., 2012). Often the lack of data available makes it difficult to enforce or monitor the success of specific conservation measures related to the transportation infrastructure (Underwood, Wilson, Ludgerus, & Evans, 2013). ...
Our study focuses on the position of protected areas in relation to the transport infrastructure planning and their specific requirements (fragmentation, artificial edge effects, buffer zones, etc.). The presence of transport infrastructure in protected areas is discouraged by the European Union legislation and although their avoidance should be easy, there are numerous cases in which knowledge of the protected areas lacked from the transport infrastructure planning. Our chapter presents the theoretical aspects of integrating protected areas with transportation infrastructures and the main software and methodologies which can be used in the planning process exemplified with case studies. The multitude of challenges found in transportation and conservation planning requires complex decision support systems (DSS), such are the tools based on Geographical Information Systems (GIS) we showcased in this chapter.
... Including decision-makers in research programs in this manner ensures that decision-makers develop a strong understanding of the research content, as well as developing a strong sense of ownership in the research, which they can then communicate more broadly within their organisation, raising the awareness of others. Indeed, numerous examples of co-produced marine science already exist (e.g. e Ceccarelli et al., 2011; Dale and Armitage, 2011; Hoey et al., 2011; Underwood et al., 2013; Van der Molen et al., 2015), demonstrating increased awareness among scientists regarding the importance of including decisionmakers in research programs. Furthermore, widespread efforts to encourage and facilitate the co-production of knowledge among marine decision-makers and scientists are already underway, for example, through collaborative identification of knowledge needs by scientists and managers (e.g. e Wilson et al., 2010; Beger et al., 2011; Cvitanovic et al., 2013). ...
The science-based management of natural resources requires knowledge exchange between scientists and environmental decision-makers, however, this exchange remains a significant challenge. Rather, evidence suggests that decision-makers rely on individual experience or other secondary sources of knowledge in isolation from scientific evidence when formulating decisions, potentially compromising the effectiveness of their decisions. As a result a new field of research broadly characterised as ‘knowledge exchange’ has emerged, focused largely on identifying and overcoming the barriers to knowledge exchange among scientists and decision-makers. More recently knowledge exchange research has also begun to explore the relationship between science and decision-making specifically in relation to marine ecosystems and resources. The aim of this paper is to review the literature in relation to knowledge exchange for natural resource management, with a focus on recent evidence in relation to the management of marine resources. This review identifies critical barriers inhibiting knowledge exchange among marine scientists and decisions-makers, such as the inaccessibility of science to decision-makers as well as institutional barriers that limit the extent to which scientists and decision-makers can prioritise knowledge exchange activities. Options for overcoming these barriers, such as novel approaches to knowledge exchange (e.g. – knowledge co-production, knowledge brokers and boundary organisations) and the enabling environments and institutional reforms needed to complement efforts to improve knowledge exchange, are also identified. This review concludes by articulating the gaps in our understanding of knowledge exchange, to help guide future research in this field and improve the sustainable management of marine resources.
... Habitat-forming (structural) organisms play a fundamental ecological role, as they act as ecosystem engineers and significantly increase the levels of biodiversity of the associated communities [5,6]. In order to improve MPAs design and effectiveness in protecting biodiversity, the importance of including habitat-forming species in marine conservation planning has been recently underlined [7,8]. ...
The integration of ecological and evolutionary data is highly valuable for conservation planning. However, it has been rarely used in the marine realm, where the adequate design of marine protected areas (MPAs) is urgently needed. Here, we examined the interacting processes underlying the patterns of genetic structure and demographic strucuture of a highly vulnerable Mediterranean habitat-forming species (i.e. Paramuricea clavata (Risso, 1826)), with particular emphasis on the processes of contemporary dispersal, genetic drift, and col-onization of a new population. Isolation by distance and genetic discontinuities were found, and three genetic clusters were detected; each submitted to variations in the relative impact of drift and gene flow. No founder effect was found in the new population. The interplay of ecology and evolution revealed that drift is strongly impacting the smallest, most isolated populations, where partial mortality of individuals was highest. Moreover, the eco-evolutionary analyses entailed important conservation implications for P. clavata. Our study supports the inclusion of habitat-forming organisms in the design of MPAs and highlights the need to account for genetic drift in the development of MPAs. Moreover, it reinforces the importance of integrating genetic and demographic data in marine conservation.
... Recent studies have used the results of this meta-analysis to predict that PLDs will be reduced and larval survival will increase in a warming ocean, influencing connectivity and dispersal patterns (e.g. Munday et al. 2009, Kendall et al. 2013, Underwood et al. 2013). Our findings have new implications for predicting the consequences of global change on marine species. ...
Latitudinal gradients in water temperature may be useful for predicting the likely responses of marine species to global warming. The ranges of coral reef fishes extend into the warmest oceanic waters on the planet, but the comparative life-history traits across their full latitudinal range are unknown. Here, we examined differences in early life-history traits of 2 coral reef fishes, the damselfish Pomacentrus moluccensis and the wrasse Halichoeres melanurus, among 8 locations across 21° of latitude, from northern Papua New Guinea (2.3°S) to the southern Great Barrier Reef (23.3°S). Water temperature during larval development ranged between 25.6 and 29.8°C among sites, with the warmest sites closest to the equator. Recently settled juveniles were collected and otolith microstructure was analysed to estimate pelagic larval duration (PLD), daily growth, and size at settlement. Latitudinal comparisons revealed a non-linear relationship between temperature and each of PLD, larval growth and size at settlement. PLD declined with increasing temperature up to approx. 28 to 29°C, above which it stabilised in P. moluccensis and increased in H. melanurus. Larval growth increased with increasing temperature up to approx. 28 to 29°C before stabilising in P. moluccensis and decreasing in H. melanurus. Size at settlement tended to be highest at mid-latitudes, but overall declined with increasing temperature above 28.5°C in both species. These results indicate that the thermal optima for growth and development is reached or surpassed at low latitudes, such that populations at these latitudes may be particularly vulnerable to global warming.
... Several novel methods of knowledge transfer have been identified in the literature to improve information flow among academics and managers. These include the coproduction of knowledge, whereby environmental practitioners actively participate in scientific research programs, allowing them to develop a comprehensive understanding of the research content (Ceccarelli et al. 2011, Hoey et al. 2011, Underwood et al. 2013. Another increasingly recognized approach to improve information flow among academics and environmental practitioners is through the use of knowledge brokers or bridging organizations, i.e., intermediaries that aim to develop relationships and networks with, among, and between producers and users of knowledge, to facilitate the exchange of knowledge throughout this network (Michaels 2009, Meyer 2010, Crona and Parker 2012. ...
The rapid development of adaptation as a mainstream strategy for managing the risks of climate change has led to the emergence of a broad range of adaptation policies and management strategies globally. However, the success of such policies or management interventions depends on the effective integration of new scientific research into the decision-making process. Ineffective communication between scientists and environmental decision makers represents one of the key barriers limiting the integration of science into the decision-making process in many areas of natural resource management. This can be overcome by understanding the perceptions of end users, so as to identify knowledge gaps and develop improved and targeted strategies for communication and engagement. We assessed what one group of environmental decision makers, Australian marine protected area (MPA) managers, viewed as the major risks associated with climate change, and their perceptions regarding the role, importance, and achievability of adaptation for managing these risks. We also assessed what these managers perceived as the role of science in managing the risks from climate change, and identified the factors that increased their trust in scientific information. We do so by quantitatively surveying 30 MPA managers across 3 Australian management agencies. We found that although MPA managers have a very strong awareness of the range and severity of risks posed by climate change, their understanding of adaptation as an option for managing these risks is less comprehensive. We also found that although MPA managers view science as a critical source of information for informing the decision-making process, it should be considered in context with other knowledge types such as community and cultural knowledge, and be impartial, evidence based, and pragmatic in outlining policy and management recommendations that are realistically achievable.
... This research has focused primarily on moving beyond the current knowledge-deficit model of communication and knowledge transfer, whereby scientists as the primary producers of knowledge are solely accountable for making new information available to decisionmakers, to contemporary approaches emphasising the need for the two-way exchange of information [42,51,8]. As a result several new approaches to knowledge exchange have been advocated, such as the co-production of knowledge, whereby decision-makers actively participate in scientific research programs (e.g.- [7,14,50]), and the use of knowledge brokers or boundary organisations [36,35,10]. ...
... One well recognised approach to improve information flow and knowledge transfer among academics and resource managers is through the co-production of knowledge, whereby managers actively participate in scientific research programs (e.g. Ceccarelli et al. 2011;Hoey et al. 2011;Underwood et al. 2013). Under this approach, decision-makers are actively engaged in research programs from the outset, ensuring that the information requirements of both groups are discussed and jointly understood before the execution of a study. ...
The integration of scientific information into the decision-making process for the management of marine resources remains a significant challenge, with the inaccessibility of primary scientific literature to environmental practitioners identified as a key limiting factor. Here, we quantify the use of primary scientific literature in environmental management plans, and explore potential barriers to the efficient integration of such scientific information into the decision-making process. Through a case study of coral dominated Marine Protected Areas (MPAs) spanning three countries (Australia, Kenya and Belize), we find that primary scientific literature represents only 14% of information cited in management plans. Such a low proportion is likely to be symptomatic of several issues regarding the accessibility of primary scientific literature to MPA managers, such as: 1. Long publication times for articles (average 40.2 ± 1.8 months); 2. Subscription-only access (up to 56% of articles behind paywalls); and/or 3. Poor articulation of management implications (only 19% of articles provided clear outcomes relevant to management). Such impediments can undermine the adaptive governance of MPAs, so we suggest improvements to knowledge transfer among scientists and managers via a diversity of approaches including knowledge brokers, boundary organisations, knowledge co-production and management-orientated summaries in research articles.
... The southward flowing Holloway Current merges into the Leeuwin Current at 22°S, which stretches over 5500 km, meandering southward along the continental shelf from the North West Cape down to the Great Australian Bite (Batteen & Miller 2009). Although there is little evidence supporting the role of these currents in the transport of coral larvae (Underwood et al. 2013) and associated Symbiodinium (Silverstein et al. 2011), the currents have been identified as primary features that link tropical fish fauna with higher latitude locations (Hutchins & Pearce 1994;Caputi et al. 1996;Beckley et al. 2009;Watson & Harvey 2009;Pearce et al. 2011). Based on the similarities between sampling regions, these currents are likely to be a main mechanism that connects Symbiodinium communities of the tropical north with the temperate south regions of Western Australia. ...
Scleractinian corals have demonstrated the ability to shuffle their endosymbiotic dinoflagellate communities (genus Symbiodinium) during periods of acute environmental stress. This has been proposed as a mechanism of acclimation, which would be increased by a diverse and flexible association with Symbiodinium. Conventional molecular techniques used to evaluate Symbiodinium diversity are unable to identify genetic lineages present at background levels below 10%. Next generation sequencing (NGS) offers a solution to this problem and can resolve microorganism diversity at much finer scales. Here we apply NGS to evaluate Symbiodinium diversity and host specificity in Acropora corals from contrasting regions of Western Australia. The application of 454 pyrosequencing allowed for detection of Symbiodinium operational taxonomic units (OTUs) occurring at frequencies as low as 0.001%, offering a 10000-fold increase in sensitivity compared to traditional methods. All coral species from both regions were overwhelmingly dominated by a single clade C OTU (accounting for 98% of all recovered sequences). Only 8.5% of colonies associated with multiple clades (clades C and D, or C and G), suggesting a high level of symbiont specificity in Acropora assemblages in Western Australia. While only 40% of the OTUs were shared between regions, the dominance of a single OTU resulted in no significant difference in Symbiodinium community structure, demonstrating that the coral-algal symbiosis can remain stable across more than 15 degrees of latitude and a range of sea surface temperature profiles. This study validates the use of NGS platforms as tools for providing fine-scale estimates of Symbiodinium diversity and can offer critical insight into the flexibility of the coral-algal symbiosis.
An understanding of larval dispersal and connectivity in corals provides valuable insight into the processes of population maintenance and replenishment and is vital for effective management. Here, we used a genotyping by sequencing approach to explore patterns of genetic connectivity in two species of coral with different reproductive modes (brooding and broadcast spawning) at the Rowley Shoals in northwest Australia. Our data revealed strikingly different patterns of genetic structure in the two species. High levels of genetic subdivision in the brooding coral I. brueggemanni was consistent with extensive self-recruitment and restricted connectivity. In contrast, the broadcast spawning coral A. digitifera formed a single panmictic population with extensive gene flow. Our results highlight the wide variation in metapopulation connectivity that exists among corals and support the well-established link between reproductive mode and population genetic structure in the marine environment.
Our study focuses on the position of protected areas in relation to the transport infrastructure planning and their specific requirements (fragmentation, artificial edge effects, buffer zones, etc.). The presence of transport infrastructure in protected areas is discouraged by the European Union legislation and although their avoidance should be easy, there are numerous cases in which knowledge of the protected areas lacked from the transport infrastructure planning. Our chapter presents the theoretical aspects of integrating protected areas with transportation infrastructures and the main software and methodologies which can be used in the planning process exemplified with case studies. The multitude of challenges found in transportation and conservation planning requires complex decision support systems (DSS), such are the tools based on Geographical Information Systems (GIS) we showcased in this chapter.
The predominance of self‐recruitment in many reef‐building corals has fundamental and complex consequences for their genetic diversity, population persistence and responses to climate change. Knowledge of genetic structure over local scales needs to be placed within a broad spatial context, and also integrated with genetic monitoring through time to disentangle these consequences. Here, we examined patterns of genetic diversity over multiple spatio‐temporal scales across tropical Australia in the ubiquitous brooding coral, Seriatopora hystrix. We also analysed complimentary environmental and demographic data to elucidate the seascape drivers of these patterns. Large genetic differences was detected between the east versus west coasts of Australia. In northwest Australia, geographic differentiation dominated genetic structure over multiple scales. However, three sympatric lineages were detected at the largest offshore reef system (Scott Reef). Similar to the differences observed among putative species in eastern Australia, these lineages were associated with different levels of wave exposure. Local genetic structure within the Scott Reef system was relatively stable over ten years, but temporal differences were observed that reflected small but important genetic changes over a few generations during recovery after severe bleaching. These results highlight the importance of self‐recruitment together with occasional longer distance connectivity for the persistence of a metapopulation across spatially and temporally variable environments. Our multidimensional research provides a foundation for further long‐term genetic monitoring to inform conservation strategies and highlights that sampling scales, ecological effects and cryptic diversity are important considerations to develop realistic understanding of the evolutionary resilience of corals.
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Patterns of hard coral cover and benthic composition were assessed at seven sites around Barrow Island in the Pilbara region of Western Australia between 2008 and 2013. While the per cent hard coral cover around Barrow Island was relatively stable between 2009 and 2012, there was a 69.3 % proportional change in hard coral cover between 2012 and 2013. Concomitant with this decline, Principle Coordinates Analysis showed a shift towards turf/coralline algae and there was a reduction in the proportion of the Acroporidae and a relative increase in the proportion of the Poritidae at most sites. During early 2013, sea surface temperatures around Barrow Island rose above seasonal averages, reaching 7.4 °C-weeks (degree heating weeks) from late February 2013 to mid-April 2013, and the decline in hard coral cover and shifts in benthic composition appear to be related to mortality associated with a coral bleaching event in early 2013.
This chapter examines the literature on the ‘barriers’ to the use of evidence in environmental policy. I identify the ways in which policy theories can provide a more sophisticated account of the gap between scientific evidence and (a) the identification of environmental problems, and (b) meaningful policy responses. I add case study discussions to give more depth to abstract discussions: a comparison between tobacco control and climate change policies; and analysis of the current debate on ‘fracking’ which raises practical concerns regarding the use of evidence in issues involving an unpredictable mix of high salience, scientific uncertainty, policy ambiguity, multi-level governance, and public protest.
This paper reviews the northern sources of the Leeuwin Current and related circulation on the North West Shelf, north of where it consolidates into its well-known poleward boundary current structure off North West Cape, Australia. This review finds that relatively warm, low salinity waters enter the Indonesian-Australian Basin through two major remote northern sources. One is tropical Pacific Ocean water emanating from the South East Asian seas via the Lombok, Ombai and Timor Straits. The other is tropical northwest Indian Ocean water via the South Java Current within the 5-10° S zone off the Sumatra and Java coasts. At the broadest scales, both sources undergo circuitous routes and associated evaporation and cooling before entering the head of the Leeuwin Current off North West Cape. It is largely unresolved as to how close to the North West Shelf coast the Leeuwin Current's source waters flow. However, earlier oceanographie studies, supported by more recently collected data presented in this paper, indicate that at least during the low wind conditions of the Southern Hemisphere autumn, a reasonably well-defined, southwestward coastal flow occurs along the shelf and shelf break. An explanation previously suggested is that this current is driven by the steric height gradient produced by local surface heating, and we propose here to name it the Holloway Current in honour of the late Dr Peter Holloway.
Background / Purpose:
The declining health of marine ecosystems around the world suggests that the current structure of sectoral governance is inadequate to successfully sustain human uses of the ocean and support healthy coastal and ocean ecosystems. One possible solution to this problem is ecosystem-based marine spatial planning (EB-MSP), which aims to maintain sustainable uses, healthy ecosystems, and the delivery of ecosystem services. In order to achieve these goals, EB-MSP must be based on specific, measureable ecological principles that articulate scientifically recognized attributes of healthy, functioning ecosystems that can be incorporated into a decision-making framework.
Main conclusion:
We present recommendations based on a synthesis of previously suggested principles, along with recommendations generated by a group of twenty marine scientists with diverse backgrounds and perspectives on MSP. The four ecological principles – maintaining or restoring (1) native species diversity, (2) habitat diversity and heterogeneity, (3) key species, and (4) connectivity - must form the foundation of any ecosystem based planning efforts. When applied in concert with social, economic, and governance principles, these ecological principles can help to inform the most suitable areas of the ocean for human activities in order to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure resilient economic and social communities.
For close to a century, recruitment of larvae to a local population has been widely accepted as a primary determinant of marine population dynamics. However, progress in elucidating the causes of recruitment variability has been greatly impeded by our ignorance of the sources of recruits. Although it is often assumed that recruitment is independent of local reproduction, there is increasing circumstantial evidence that physical and behavioural mechanisms could facilitate larval retention near source populations. To develop a direct method for reconstructing the dispersal history of recruiting larvae, we put forward the hypothesis that differences in nutrient and trace-element concentrations between coastal and open oceans could result in quantifiable differences in growth rate and elemental composition between larvae developing in coastal waters (locally retained) and larvae developing in open ocean waters (produced in distant locations). Using this method, we show that recruitment to an island population of a widely distributed coral-reef fish may often result from local retention on leeward reefs. This result has implications for fisheries management and marine reserve design, because rates of dispersal between marine populations-and thus recruitment to exploited populations-could be much lower than currently assumed.
Marine ecosystems are traditionally considered to be highly connected, caused by long-distance movements of propagules in an open fluid medium. But this principle is not universal, and populations of many marine organisms have restricted gene-flow, including ones with drifting propagules. Direct tracking of marine free-floating propagules over large distances is virtually impossible, but long-distance dispersal (LDD) can be deduced from their drifting time and transport rates. Alternatively, LDD can be estimated as genetic exchange with the use of allelic frequency data obtained with genetic markers. The present study compares both approaches of LDD estimation for the tropical seagrass Thalassia testudinum. Fruit dispersal potential was measured in Puerto Morelos reef lagoon, Mexico. Between 10 and 15% of the fruits floated to the surface (floating potential <1 to 10 d), with a derived potential dispersal of <1 to 360 km. The remainder of the fruits dehisced in situ followed by limited seed dispersal (<1 to 10 m). Genetic diversity was characterized using 6 microsatellite loci for 16 populations distributed along a 1350 km long stretch of the Mexican coast, revealing a total of 58 alleles. AMOVA showed that only 9.75% of the total variation was accounted for by genetic differences between the populations. Isolation by distance was significant, and revealed a panmictic area of 350 km. The results of both approaches of LDD estimation coincided well and the maximum displacement of the fruits of this marine angiosperm exceeded, by 1 to 2 orders of magnitude, the reported seed dispersal by terrestrial seed plants.
Recent studies have revealed that reef fish larvae have excellent sustained swimming capabilities and considerable potential for modifying their dispersal patterns by active swimming. However, these studies concentrate solely on the late pelagic phase. We examined the development of swimming abilities from hatching through to settlement in 3 reef fish species (Pomacentrus amboinensis, Sphaeramia nematoptera, Amphiprion melanopus). Larval rearing provided larvae at all stages of development. Experiments were conducted in flow chambers designed for measuring the critical and sustained swimming capability of young larvae. In all 3 species, critical swimming ability increased steadily with age, size, relative propulsive area and developmental stage of the larvae. In contrast, sustained swimming ability showed a marked inflection during development. Differences among species throughout development appear to reflect variations in the developmental patterns of the 3 species. Propulsive area was highly correlated with swimming ability and may prove useful for estimating swimming capabilities among species. The results suggest that some species have the potential to actively modify their dispersal patterns from an early age.
Lutjanus carponotatus ranges from the Indian Ocean to northern Australia and Papua New Guinea and is an important species for both commercial and recreational fisheries. Due to its life history characteristics and fishing pressures, L. carponotatus is vulnerable to overfishing and suitable management is essential. This phylogenetic and population genetic study assessed the population genetic structure of L. carponotatus at seven locations in three bioregions in Western Australia (WA) using the mitochondrial DNA control region. Analysis of molecular variance (AMOVA) indicated no genetic differentiation among locations within (øCT=0.051) and among bioregions (øSC=−0.026). Phylogenetic analyses indicated no geographic partitioning within WA, though two distinct lineages were found. Within these two lineages there was no significant spatial partitioning, suggesting a panmictic population that can, under current conditions, be managed as a single stock. WA and Great Barrier Reef (GBR) population genetic data were then combined to determine the broad-scale connectivity between the east and west coast of Australia. L. carponotatus from the GBR did differ significantly (FST=0.64, p=
Numerical models are used to simulate three-dimensional circulation and dispersal of material, such as larvae of marine organisms, on Davies Reef, C Great Barrier Reef. Results indicate order-of-magnitude differences in the residence times of material at different levels in the water column. Residence times are often comparable to the duration of the planktonic larval life of many coral reef species. Results reveal a potential for the maintenance of local populations of various coral reef organisms by self-seeding, and allow reinterpretation of the connectedness of the coral reef ecosystem. -from Authors
The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances.
The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in
high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures.
The success of marine protected areas (MPAs) as fisheries management tools in tropical latitudes has generated interest in their applicability and potential elsewhere. Here we suggest that dispersal and gene flow in marine fish populations (a primary biological consideration for marine reserve design) increases with latitude. For example, north temperate fish species at latitudes between 40° and 45° had about three times greater dispersal potential (planktonic larval duration (PLD), n = 96 species) and genetic homogeneity (FST, n = 100 species) than fish species near equatorial regions. Using the PLD and FST relationships, dispersal increases at a rate of ~8% per degree of latitude north or south of the equator. Therefore tropical MPAs should not serve as direct scalar templates in other regions, but rather should be used as a basis against which higher-latitude MPAs should be scaled. However, a review of 429 existing MPAs indicates that no such changes in reserve size have been implemented with respect to latitude. Fisheries managers must be prepared and willing to implement MPAs at large scales in high latitudes, either as single reserves or in a network, or else we lose the legitimacy of a new and promising management tool for conserving marine biodiversity in cold ocean regions.
'Supply-side' ecology recognizes the potential role that recruitment plays in the local population dynamics of open systems. Apart from the applied fisheries literature, the converse link between adults and the production of cohorts of recruits has received much less attention. We used a hierarchical sampling design to investigate the relationships between adult abundance, fecundity, and rates of larval recruitment by acroporid corals on 33 reefs in five sectors (250-400 km apart) stretching from north to south along the length of the Great Barrier Reef, Australia. Our goal was to quantify patterns of recruitment at multiple scales, and to explore the underlying mechanisms. Specifically, we predicted that large-scale patterns of recruitment could be driven by changes in the abundance of adults and/or their fecundity, i.e., that corals exhibit a stock-recruitment relationship. The amount of recruitment by acroporids in each of two breeding seasons varied by more than 35-fold among the five sectors. Adult density varied only twofold among sectors and was not correlated with recruitment at the sector or reef scale. In contrast, fecundity levels (the proportion of colonies on each reef that contained ripe eggs) varied from 15% to 100%, depending on sector, year, and species. Spatial and temporal variation in the fecundity of each of three common Acropora species explained most of the variation (72%) in recruitment by acroporids, indicating that the production of larvae is a major determinant of levels of recruitment at large scales. Once fecundity was accounted for, none of the other variables we examined (sector, reef area, abundance of adults, or year) contributed significantly to variation in recruitment. The relationship between fecundity and recruitment was nonlinear, i.e., rates of recruitment increased disproportionately when and where the proportion of gravid colonies approached 100%. This pattern is consistent with the hypothesis that enhanced fertilization success and/or predator satiation occurs during mass-spawning events. Furthermore, it implies that small, sublethal changes in fecundity of corals could result in major reductions in recruitment.
The extent of larval dispersal on coral reefs has important implications for the persistence of coral reef metapopulations, their resilience and recovery from an increasing array of threats, and the success of protective measures. This article highlights a recent dramatic increase in research effort and a growing diversity of approaches to the study of larval retention within (self-recruitment) and dispersal among (connectivity) isolated coral reef populations. Historically, researchers were motivated by alternative hypotheses concerning the processes limiting populations and structuring coral reef assemblages, whereas the recent impetus has come largely from the need to incorporate dispersal information into the design of no-take marine protected area (MPA) networks. Although the majority of studies continue to rely on population genetic approaches to make inferences about dispersal, a wide range of techniques are now being employed, from small-scale larval tagging and paternity analyses, to large-scale biophysical circulation models. Multiple approaches are increasingly being applied to cross validate and provide more realistic estimates of larval dispersal. The vast majority of empirical studies have focused on corals and fishes, where evidence for both extremely local scale patterns of self-recruitment and ecologically significant connectivity among reefs at scales of tens of kilometers (and in some cases hundreds of kilometers) is accumulating. Levels of larval retention and the spatial extent of connectivity in both corals and fishes appear to be largely independent of larval duration or reef size, but may be strongly influenced by geographic setting. It is argued that high levels of both self-recruitment and larval import can contribute to the resilience of reef populations and MPA networks, but these benefits will erode in degrading reef environments.
Larval duration of a demersal fish is a product of its genotype, its larval environment and the capacity of the species to delay metamorphosis. Circumstantial evidence has led to the hypothesis that the lower age-limit for settlement is governed by the rate of larval development, while the upper age-limit is determined by the extent to which a delay of metamorphosis is possible. This study examined the capacity of a widely distributed reef fish, the manini Acanthurus triostegus, to extend its larval duration by delaying metamorphosis. Variation in larval duration was examined from 8 samples of manini collected in French Polynesia using crest nets over a 2 yr period. Variation in the overall age at colonisation determined from daily otolith increments was very low (CV 5.5 %) given the pan-Pacific distribution pattern of the species. A field experiment was conducted to determine whether manini could delay metamorphosis. To enable its interpretation, the metamorphosis of the species was characterised morphologically. Metamorphosis involved a loss of transparency, a shortening of fin spines and a migration of the mouth from a terminal to ventral position over a 5 d period. To experimentally examine the capacity of the species to delay metamorphosis manini were caught at night as they colonised a reef and placed in 1 of 2 treatments: benthic cages in the shallow backreef, or fine monofilament cages suspended between 3 and 6 m in a 50 m water column on the outer reef slope. Fish in benthic cages completed metamorphosis within 5 d. In contrast, 24 % of fish in pelagic cages (8 out of 34 fish) remained transparent (although some developed faint stripes) and retained the pelagic body shape. Fish that delayed metamorphosis still deposited a mark on their otoliths indistinguishable in structure from the settlement marks deposited on otoliths of their benthic-caged counterparts and reef-caught juveniles. This is the first experimental evidence that the settling stages of some demersal fish species can delay metamorphosis in the reef environment. As such it supports the conceptual model generally applied to the selective settlement of demersal fishes.
The Nature Conservancy takes a strategic and systematic approach to conservation planning. Ecoregional assessments are used to set goals and identify geographical priorities, and Conservation Action Planning is used to develop strategic plans for conservation areas. This study demonstrates how these planning processes were applied at the seascape scale based on a case study of Kimbe Bay, Papua New Guinea. Conservation Action Planning was used to identify key threats and strategies, and systematic conservation planning (similar to that used for ecoregional assessments) was used to design a network of marine protected areas to be resilient to the threat of climate change. The design was based on an assessment of biodiversity and socio-economic values, and identified 14 Areas of Interest that meet specific conservation goals. A detailed community-based planning process is now underway with local communities that own and manage these areas to refine and implement the marine protected area network.
Understanding the evolutionary processes that have shaped existing patterns of genetic diversity of reef-building corals over broad scales is required to inform long-term conservation planning. Genetic structure and diversity of the mass-spawning hard coral, Acropora tenuis, were assessed with seven DNA microsatellite loci from a series of isolated and discontinuous coastal and offshore reef systems in northwest Australia. Significant subdivision was detected among all sites (FST = 0.062, RST = 0.090), with the majority of this variation due to genetic differentiation among reef systems. In addition, genetic divergence was detected between the coastal and offshore zones that cannot be adequately explained by geographic distance, indicating that transport of larvae between these zones via large-scale oceanic currents is rare even over time frames that account for connectivity over multiple generations. Significant differences in the amount of genetic diversity at each system were also detected, with higher diversity observed on the lower latitude reefs. The implications are that these reef systems of northwest Australia are not only demographically independent, but that they will also have to rely on their own genetic diversity to adapt to environmental change over the next few decades to centuries.
We utilized a spatial and temporal analyses of genetic structure, supplemented with ecological and oceanographic analysis, to assess patterns of population connectivity in a coral reef fish Chromis margaritifer among the unique and remote atolls in the eastern Indian Ocean. A subtle, but significant genetic discontinuity at 10 microsatellite DNA loci was detected between atoll systems corresponding with a low (≤ 1%) probability of advection across the hundreds of kilometers of open ocean that separates them. Thus, although genetic connections between systems are likely maintained by occasional long-distance dispersal of C. margaritifer larvae, ecological population connectivity at this spatial scale appears to be restricted. Further, within one of these atoll systems, significant spatial differentiation among samples was accompanied by a lack of temporal pairwise differentiation between recruit and adult samples, indicating that restrictions to connectivity also occur at a local scale (tens of kilometers). In contrast, a signal of panmixia was detected at the other atoll system studied. Lastly, greater relatedness and reduced genetic diversity within recruit samples was associated with relatively large differences among them, indicating the presence of sweepstakes reproduction whereby a small proportion of adults contributes to recruitment in the next generation. These results are congruent with earlier work on hard corals, suggesting that local production of larvae drives population replenishment in these atoll systems for a range of coral reef species.
Rattray Island, northeast Australia, is 1.5 km long, 300 m wide, and lies in well-mixed water approximately 25 m deep. Its long axis is inclined at about 60° into the direction of the dominant semidiurnal tidal current. The length of the wake in the lee of the island, as documented by aerial photographs and satellite imagery, appears to equal that of the wake behind a flat plate in a two-dimensional flow at a Reynolds number of about 10. However, current metering, drogues measurements, and temperature mapping indicate internal wake velocities much greater than would be consistent with such a simple low Reynolds number model. Further, estimates of the turbulent eddy coefficient suggest an effective Reynolds number more in the vicinity of 103. To reconcile these observational differences and to explain the observed upwelling in the core of the wake, an Ekman pumping model is proposed. It is postulated that the Ekman benthic boundary layer driven by rotation in the wake allows the vertical vorticity introduced into the water at the tip of the island at the point of separation, to be negated by the vorticity of opposite sign introduced at the bottom. Further, it is shown that a large fraction of the kinetic energy of the upstream flow facing the island is used to drive the wake eddies, leading to the conclusions that the trapping of water in the lee of islands greatly increases head losses on continental shelves with numerous islands, coral reefs, and rock outcrops.
Long-term progressive changes of the Leeuwin Current are linked to plate and ocean basin 'geography' and Cenozoic global climates and palaeoceanography. Suggestions of the presence of a proto-Leeuwin Current as early as late Middle to Late Eocene times (c. 35–42 Ma) cannot be verified by the fossil record of the western margin of Australia. "Leeuwin Current style" circulation around Australia was certainly established by the early Oligocene, in response to palaeogeographic changes in the Tasman Strait. This, followed by tectonic reorganisation of the Indonesian Archipelago throughout the Miocene, provided a palaeogeographic setting, which by the Pliocene was essentially that of today. The subsequent history of the Leeuwin Current comprises climatically-induced changes operating over orbital and sub-orbital temporal scales. Specifically, the advent of Pleistocene-style climates, especially over the last 800 000 years, and their associated interglacial – glacial states provide the two end-member climate-ocean states that have characterised Leeuwin Current activity during that time. Indications of the nature of these contrasting states is provided by: (i) the Last Interglacial (c. 125 Ka) during which sea level was higher by some +4 m, and with higher sea surface temperatures (SSTs) clearly indicating a more 'active' Leeuwin Current; and (ii) the Last Glacial Maximum (21 Ka), during which sea level was some 130 m lower than today, resulting in massive shelf extensions along the coast of Western Australia, accompanied by reduced Indonesian Throughflow, lower low latitude SSTs and changes in the Western Pacific Warm Water Pool, and with these changes, possibly reduced Leeuwin Current activity. Sub-orbital scale fluctuations in current strength are driven by global climate change associated with El Niño – La Niña events as well as regional climatic changes driven by volcanism. These forcing mechanisms operate at time scales well within the reach of human experience, and provide important comparative data for predicting the response of the Leeuwin Current to climate change predicted for this century. Studies of the impact of changes in the vigour of the Leeuwin Current on shallow marine communities are in their infancy. Coupling climate models with geological analogues provide important research agenda for predicting the trajectory of future changes to the Leeuwin Current and their impacts on the marine biota of coastal Western Australia.
1] Historical sea level records reveal that a strengthening of the Pacific subtropical cells (STCs) since the early‐1990's has reversed a multi‐decadal weakening tendency. Stronger STCs correspond to a stronger Leeuwin Current in the southeast Indian Ocean (SEIO) and a stronger Indonesian Throughflow, due to dynamic connections of the Pacific and SEIO through equatorial and coastal waveguides. Multi‐decadal trends of the STCs and their influence on the SEIO have confounded the detection of human induced global change signals in the short instrumental records of the two circulation systems.
Understanding the pattern of connectivity among populations is crucial for the development of realistic and spatially explicit population models in marine systems. Here we analysed variation at eight microsatellite loci to assess the genetic structure and to infer patterns of larval dispersal for a brooding coral, Seriatopora hystrix, at an isolated system of reefs in northern Western Australia. Spatial autocorrelation analyses show that populations are locally subdivided, and that the majority of larvae recruit to within 100 m of their natal colony. Further, a combination of F- and R- statistics showed significant differentiation at larger spatial scales (2-60 km) between sites, and this pattern was clearly not associated with distance. However, Bayesian analysis demonstrated that recruitment has been supplemented by less frequent but recent input of larvae from outside the local area; 2-6% of colonies were excluded from the site at which they were sampled. Individual assignments of these migrants to the most likely populations suggest that the majority of migrants were produced at the only site that was not decimated by a recent and catastrophic coral bleaching event. Furthermore, the only site that recovered to prebleaching levels received most of these immigrants. We conclude that the genetic structure of this brooding coral reflects its highly opportunistic life history, in which prolific, philopatric recruitment is occasionally supplemented by exogenously produced larvae.
Mass spawning occurred mainly around the third quarter of the moon on neap, nocturnal, ebb tides. Some 102 species of scleractinian corals from Western Australian Reefs are known to spawn during the austral autumn. A further 44 species were found to contain ripe gonads during the same period and are presumed to participate in the annual coral mass spawning on Western Australian reefs. These records represent 88% of the coral species studied so far or about 46% of the coral species currently described from Western Australia. In Western Australia, coral mass spawning coincides approximately with the annual intensification of the Leeuwin Current, a warm poleward current of tropical origin that flows along the coastline of Western Australia during the austral autumn and winter. This current provides a mechanism for the southward dispersal of planulae and raises the possibility of a unidirectional gene flow between regionally separate coral reefs in Western Australia. Comparisons with the spring coral mass spawnings on the Great Barrier Reef indicate that, apart from the seasonal difference in the timing of spawning, many similarities exist suggesting that the same phenomenon is occurring on both sides of Australia. The different seasonal timing of coral mass spawning on the E and W coasts of Australia is probably the result of an endogenous rhythm reflecting the breeding patterns of ancestral corals as a consequence of selective dispersal of larvae from equatorial regions. -from Author
We examine the hypothesis that reef fish larvae have some direct influence on their own dispersal and ability to recruit to their natal reef by tracking cohorts of bicolor damselfish (Stegastes partitus) from hatching to settlement onto the reef, about 30 d later. We conducted high-resolution sampling during two consecutive years in a small area (15 km x 20 km) off the west coast of Barbados, extending from depths of 0 to 100 m. Observations of discrete stage-specific larval patches of mean size of 29.4 and 13.2 km2 for preflexion (>5-d old) and flexion/postflexion (>5-d old) stages extending ca. 30 m in the vertical indicated that larvae initially dispersing as patches tend to stay in coherent patches throughout their pelagic duration. Highest concentrations of preflexion larvae within a patch were in the upper 20 m, while those of older larvae were always deeper. Downward migration of about 60 m throughout ontogeny within stratified currents represented a retention mechanism for locally spawned larvae. Most of the variability in estimated retention rates between daily cohorts occurred during the earliest stages as a result of the dynamic nature of surface currents experienced by larvae prior to the onset of vertical migration. Differences in residence time between experiments were consistent with observed intermonthly variability in recruitment strength, implying that pelagic processes can explain recruitment rates. These results provide empirical evidence for larval retention of coral reef fishes and stress the role of active behavior in larval transport.
Larval fishes exhibit marked vertical zonation patterns that are important in planktonic predator-prey interactions. This zonation has been related to both proximate physical (e.g., light intensity) and ultimate biological factors (e.g., predator risk, prey availability). We hypothesize that changes in visual sensitivity and feeding performance in larval fishes provide a constraint on depth distributions and that this constraint may represent the major determinant of vertical distribution patterns. To test the generality of the relationship between larval age and visual sensitivity, larvae were obtained from captive breeding adults of seven species (three Apogonidae and four Pomacentridae). The lowest light intensity at which feeding behavior occurred was measured using infrared video techniques with natural prey items. The visual sensitivity of the larvae, measured as initiation of feeding, increased by about 3 orders-of-magnitude during the larval phase. The abilities of the larvae were broadly similar within families, but there were marked differences between families. Pomacentrids were about an order-of-magnitude less light-sensitive than apogonids. Larval apogonids are potentially capable of feeding at a depth of about 100 m in clear tropical waters at 4 mm standard length (SL) and to 200 m at 12 mm SL. The patterns of ontogenetic and phylogenetic differences in light sensitivity are consistent with field observations on the vertical distributions of larvae in these taxa.
Field, laboratory, and numerical results suggest that the free shear
layer behind flow separation points and the internal circulation
generated by rotation in the eddy are important processes in island
wakes in shallow coastal waters.
Gene flow was shown to be limited between western and eastern Caribbean populations of the reef-building coral, Acropora palmata. However, some mixing was detected among populations near Puerto Rico. Our genetic analyses categorize A. palmata samples from the east coast of the Dominican Republic with the western Caribbean population, suggesting a filter to gene flow east of the Dominican Republic. To test the hypothesis of a present day bio-oceanographic filter occurring between Puerto Rico and the Dominican Republic (i.e., in the Mona Passage), we used a Lagrangian stochastic model (LSM) of larval dispersal, coupling coral life history characteristics with physical forcing. The model operated at two spatial scales: Caribbean-wide and focusing on the Mona Passage area. Results from the Caribbean-wide study showed no significant virtual larval exchange between the two populations. The small-scale model indicated that virtual larvae do not readily traverse the Mona Passage during the corals' reproductive season. Larvae released from Mona Island, in the center of the passage, are retained in the lee within topographically steered eddies, which act, together with the larval competency period, as a de facto filter to dispersal. Combined, our findings reveal the location of a seasonal filter to gene flow and its mechanism. Understanding the causes of population differentiation is an ongoing effort in evolutionary biology. The oceanic environment provides few obvious physical barriers that may prevent genetic exchange of pelagic larvae between populations, so it is difficult to understand how popula- tions differentiate. The numeric (how many?) and geo- graphic (over what distance?) scale of larval movements has been at the center of a long-standing debate. Pelagic larval stages may connect geographically distant populations by riding with fast ocean surface currents (Heck and Mccoy
Genetic analyses of marine population structure often find only slight geo- graphic differentiation in species with high dispersal potential. Interpreting the significance of this slight genetic signal has been difficult because even mild genetic structure implies very limited demographic exchange between populations, but slight differentiation could also be due to sampling error. Examination of genetic isolation by distance, in which close populations are more similar than distant ones, has the potential to increase confidence in the significance of slight genetic differentiation. Simulations of one-dimensional stepping stone populations with particular larval dispersal regimes shows that isolation by distance is most obvious when comparing populations separated by 2-5 times the mean larval dispersal distance. Available data on fish and invertebrates can be calibrated with this simulation approach and suggest mean dispersal distances of 25-150 km. Design of marine reserve systems requires an understanding of larval transport in and out of reserves, whether reserves will be self-seeding, whether they will accumulate recruits from surrounding exploited areas, and whether reserve networks can exchange recruits. Direct measurements of mean larval dispersal are needed to understand connectivity in a reserve system, but such measurements are extremely difficult. Genetic patterns of isolation by distance have the potential to add to direct measurement of larval dispersal distance and can help set the appropriate geographic scales on which marine reserve systems will function well.
Behaviour during the pelagic larval stage of coral-reef fishes can strongly influence dispersal, yet little is known of behavioural ontogeny. Speed, orientation and vertical distribution of larvae of 4 coral-reef fishes (Platax teira, Ephippidae; Lutjanus malabaricus, Lutjanidae; Epinephelus coioides, E. fuscoguttatus, Serranidae; 6 to 23 mm) were measured in situ off Taiwan. In E. coioides and E. fuscoguttatus, speed was 2 to 30 cm s(-1) (4 to 19 body lengths s(-1), BL s(-1)), and increased at 1.4 to 2.3 cm s(-1) min(-1), In P. teira and L. malabaricus, speed was 11.2 to 16.6 cm s(-1) (4 to 20 BL s(-1)) across the size range. All but the smallest, slowest larvae had Reynolds numbers > 1000, and so swam in an inertial environment. In Sift speeds were 39 to 87%, of critical speeds, and smaller larvae swain nearer to critical speed than larger larvae. Of the larvae 71 to 90% swam directionally, but neither percentage of directional individuals nor orientation precision increased with size. P. teira swam toward the Southwest (offshore). Epinephelus species undertook ontogenetic changes in orientation. Neither orientation nor ontogenetic changes were found in L. malabaricus. Horizontal swimming can influence dispersal directly. Vertical distribution, which differed an-tong species, can influence dispersal indirectly. P. teira became Surface orientated, ascending 0.8 m per mm increase in length. L. malabaricus descended 0.5 m per mm increase in length. E. coioides ascended 0.4 m per mm increase in length. E, fuscoguttatus preferred greater depths, and lacked ontogenetic changes, The behaviours and their development show these larval reef fishes can influence dispersal in species-specific ways.
Larval settlement rates, genetic structure, and gene flow of broadcast-spawning (Acropora tenuis) and planula-brooding (Stylophora pistillata) corals (Scleractinia) were compared within a 500 km range in the Ryukyu Archipelago. We conducted a laboratory experiment to investigate planula settlement rates, and a broad sampling survey to determine genetic variation in both species in the Archipelago. In the laboratory experiment, the planulae of S. pistillata settled a few hours after release, while those of A. tenuis started to settle at least 4 d after the release of gametes. The survival rates and competency periods of larvae were higher and longer for A. tenuis than for S. pistillata, These results suggest that broader dispersal is more likely for A. tenuis than for S. pistillata. In the population genetic analysis, we measured local (2 stations in a region) and regional (Okinawa, Kerama and Yaeyama) patterns of genetic variation with allozyme electrophoresis. We also inferred the levels of gene flow in the 2 species. In the study area, gene flow (N(e)m) and genetic distance (D) were, respectively, higher and smaller for the spawner A. tenuis (N(e)m = 3.5 to 16.4, D = 0.028 to 0.187) than for the brooder S. pistillata (N(e)m = 0.9 to 1.5, D = 0.026 to 0.309). Therefore, the planulae settlement rates were well in agreement with gene flow. In addition, for both species, N(e)m between the Okinawa and Kerama regions (30 to 150 km apart; N(e)m = 9.4 to 22.5 in A. tenuis and 1.4 to 3.3 in S. pistillata) was higher than that between the Okinawa-Kerama and Yaeyama regions (up to 500 km apart; N(e)m = 3.1 to 9.4 in A. tenuis and 0.5 to 1.4 in S, pistillata). The results suggest that coral populations in the Kerama Island are a major source of the coral planulae needed for the recovery of both brooding and spawning coral communities around the Okinawa Islands, after the mass-bleaching event in 1998.
Principles for designing marine protected area (MPA) networks that address social, economic, and biological criteria are well established in the scientific literature. Climate change represents a new and serious threat to marine ecosystems, but, to date, few studies have specifically considered how to design MPA networks to be resilient to this emerging threat. Here, we compile the best available information on MPA network design and supplement it with specific recommendations for building resilience into these networks. We provide guidance on size, spacing, shape, risk spreading (representation and replication), critical areas, connectivity, and maintaining ecosystem function to help MPA planners and managers design MPA networks that are more robust in the face of climate-change impacts.
Determination of larval dispersal distances and larval origins is a central challenge in contemporary marine ecology. In this work, the larval dispersal problem is discussed from the perspective of oceanography. Following formulation of the advection– diffusion model, the importance of scale is argued. When considering dispersion parameters at the appropriate population scales, advection is usually weaker than initially anticipated (and often used), and diffusion is stronger than typically used in model studies. Focusing attention on coastal populations, the importance of retention zones is described, and the more general existence of a coastal boundary layer is discussed. The coupling of cross-shore and alongshore dispersion results in a nonlinear relation between alongshore dispersal distance and larval planktonic period for dispersion in a sheared flow. Thus, small changes in cross-shore dispersal, whether due to environmental differences or larval behavior result in significant differences in alongshore dispersal. Finally, the interplay between advection and diffusion is explored, showing the importance of adequately representing the diffusive effects that mitigate alongshore advection. In most cases, diffusion acts to prevent ''wash-out'' of a population and allows for more flexibility in the size and spacing of effective marine reserves. Future challenges must bring oceanographers and ecologists together around specific dispersal problems if there is to be a significant improvement in the notable absence of hard data in this field of enquiry.
Life-history parameters were used to estimate the dispersal potential of 1021 marine macroinvertebrates recorded in species lists from 91 sites comprising rocky intertidal, subtidal, kelp forest, sandy beach, and soft-bottom habitats in Washington, Oregon, and California. Mean species richness was significantly greater in the California rocky subtidal habitat. Data on development mode, planktonic larval duration, rafting potential, and adult mobility were compiled, and summaries of the dispersal potentials of taxa within each habitat type were generated and compared. In summary, development mode was known or estimated for 76% of species; larval planktonic duration for 49%; adult mobility for 76%; and rafting potential for 46%. In comparisons of species' life-history traits among habitats, sand-dominated habitats were distinct from rocky habitats. In rocky habitats, ∼42% of species had planktonic feeding larvae, 43% had planktonic nonfeeding larvae, and 15% had nonplanktonic larvae. Sandy intertidal habitats had higher proportions of taxa with nondispersing, nonplanktonic larvae and lower proportions of planktonic feeding and non-feeding larvae than all other sites. Soft-bottom subtidal communities had the highest proportion of taxa with planktonic feeding development and larvae with planktonic lifespans >30 d. Species in soft-bottom subtidal sites, therefore, have the greatest potential for extensive larval dispersal, whereas species in soft-bottom intertidal sites have the least potential for larval dispersal. In these sites with limited larval dispersal potential, there is greater potential for adult dispersal through adult movement and rafting. These differences in the dispersal potential of larvae and adults suggest that the effect of environmental changes and the effectiveness of reserves may differ between habitats. Conservation methods, including the use of marine reserves, must therefore be tailored to the habitat of interest if effective protection of community resources is to be achieved.
Allozyme variation was used to investigate the genetic structure of Lutjanus sebae, Lethrinus nebulosus, Lethrinus choerorynchus, and Epinephelus multinotatus, which are components of a multispecies fishery off north-western Australia. Samples of each species were obtained from five or six localities, over a total distance of 1400-2080 km. Allelic variation was found at 13-16 loci in each species. The consistent picture to emerge was one of little genetic subdivision in all four species, with average values of FST ranging from 0.003 in L. sebae to 0.012 in E. multinotatus. Although there was statistically significant variation in allelic frequencies in three of the species, there were no clear geographical groupings of populations. With the possible exception of clinal variation for aldehyde oxidase in E. multinotatus, all heterogeneity of allelic frequencies was within the range that could easily be due to within-generation effects of selection. Thus, the allozyme data are consistent with the view that there are extensive connections of populations over large distances. The electrophoretic study also confirmed that, contrary to suggestions in the literature, L. nebulosus, L. choerorynchus, and Lethrinus laticaudis are reproductively isolated species.
Observations of the current and wind distributions on the southern part of the Australian North West Shelf between January 1982 and July 1983 are presented. Maps of monthly averages of winds and currents from a variety of locations are presented as well as some time series spanning 19 months of currents and water temperatures from a shelf-slope location and corresponding winds from a coastal station. The main feature of the observations is the strong flow to the south-west parallel to the bathymetry known as the Leeuwin Current. From the observations across the continental shelf, the low-frequency flow is strongest over the shelf break reaching a maximum speed of approximately 0 25 m s-1. The current is strongest between February and June. Reversals of the flow to the north- east are usually weak in strength and of short duration and are associated with strong south-west winds. However, observations of water temperature suggest the north-east currents cause weak upwelling events of cold deep water onto the shelf. The south-east trade winds blow from the south- east between March and August, but are shown to be inefficient in generating longshore currents to the south-west and hence in strengthening the Leeuwin Current.
In October 1987 and March 1988, measurements were taken across the Sahul shelf and the southwestern end of the Timor Strait to the edge of Indonesian waters. The shipboard instrumentation comprised a conductivity-temperature-depth (CTD) rosette, an acoustic Doppler current profiler (ADCP) and a Pegasus dropsonde. Complementary data came from satellite-tracked drifters, continental shelf moorings, and a Nansen bottle survey in 1976. Pegasus and ADCP measurements in the strait suggested a total transport of about 7 Sv toward the Indian Ocean, with about half of this in the upper 350 m. However, transports may at times be higher, because a drifter in July 1983 revealed speeds of 1 ms-1 in the strait, twice those measured on the surveys. Data from moored current meters implied a transport on the shelf of roughly 1 Sv, except in the autumn transitions of the monsoon in 1985 when it exceeded 3 Sv. Water properties measured on the 1987 and 1988 surveys suggested components from the Fores and Banda seas, Indian Ocean Central Water and a high-salinity subsurface plume from evaporation on the inner Sahul shelf.
Allozyme electrophoresis of two corals was used to assess whether populations at Ningaloo Reef, Western Australia are primarily self-seeding or whether recruitment is from a broader geographic pool. Significant genetic subdivision across a range of spatial scales (between 6.5 km and 155 km) was found for both Acropora digitifera and A. aspera, with mean F
ST values of 0.010 and 0.067 respectively. Large departures from Hardy-Weinberg expectations were found for both species. Without exception these were due to deficits of heterozygotes; mean D values were −0.341 for A. digitifera and −0.455 for A. aspera. The magnitude of the deficits was consistent both across loci for all sites and across all sites for each locus. Some loci were found to be in linkage disequilibrium but no consistent pattern was observed. Also, multi-locus genotypic diversity values were generally high (between 0.83 and 1.00) and so departures from equilibria cannot be attributed to asexual reproduction. The most plausible explanation for the patterns observed is restricted gene flow at both the planktonic and gametic stages, with mating between close relatives.
Coral reef fish have considerable larval behavioral capabilities that can lead to success- ful completion of the early pelagic life phase. In particular, vertical migration during ontogeny increases retention near natal reefs and decreases losses due to transport by currents. For those larvae that are not returning home, the relative influence of behavior (biology) and currents (physics) on their arrival pattern among adjacent and distant reefs is not known. Moreover, interactions of the naturally small-scale larval movements with those of larger-scale currents need to be evaluated with regard to the spatial patterns of recruitment. We use an offline Lagrarangian stochastic modeling approach to explore the relative influence of physical (i.e. eddy perturbation, diffusion) and biologi- cal processes (i.e. vertical movement, mortality) on the connectivity of the coral reef fish population in the western Caribbean, a region with complex geomorphology and circulation. This study reveals that the impact of larval behavior extends beyond enhancing the process of self-recruitment by changing population connectivity patterns. Connectivity is significantly influenced by larval vertical movement, survival, and by the eddy field, all controlling arrival patterns near reefs. A sensitivity analysis is done to gauge the robustness of the results by varying the model parameters. We find that particle-tracking models with homogeneous parameterization of the sub-grid motion tend to bias dispersal from and along the reef track, which can be mitigated by using spatially explicit parameters calculated from the Eulerian velocity fields. Finally, larval survival emerges as a key component for connectivity estimates, the study of which poses a great challenge in tropical ecosystems.