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Abstract

1. The Chagos Archipelago was designated a no-take marine protected area (MPA) in 2010; it covers 550 000 km 2 , with more than 60 000 km 2 shallow limestone platform and reefs. This has doubled the global cover of such MPAs. 2. It contains 25–50% of the Indian Ocean reef area remaining in excellent condition, as well as the world's largest contiguous undamaged reef area. It has suffered from warming episodes, but after the most severe mortality event of 1998, coral cover was restored after 10 years.

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... This study was conducted in the Chagos Archipelago, Indian Ocean (5° 50′ S, 72° 00′ E). Importantly, these coral reefs are isolated from the majority of direct human stressors, such as fishing and poor water quality 21,22,46 , which enabled us to investigate BEF relationships in a relatively pristine, high-diversity system. At the same time, even these remote reefs are prone to some of the same stressors that affect nearly all locations worldwide, namely climate change and invasive species. ...
... Instead, we compared the same reefs before versus after the heatwave under the assumption that any observed temporal changes were primarily caused by the heatwave. This assumption is reasonable given the extreme temperature anomalies in the region that occurred during this time period 23,47 , along with the isolation of the study region from other stressors 21,22,46 . The presence of invasive rats did not modify the extent of coral bleaching on these reefs 24 , so these two stressors were treated as independent. ...
... [56][57][58][59][60][61][62] . We used a sea surface temperature of 28 °C, which is the typical mean sea surface temperature throughout the study region 46 . Importantly, differences in primary productivity explain almost no variability in K max at a global scale, but at smaller spatial scales, differences in resource availability among sites probably have a greater influence 41 . ...
Article
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Positive relationships between biodiversity and ecosystem functioning (BEF) highlight the importance of conserving biodiversity to maintain key ecosystem functions and associated services. Although natural systems are rapidly losing biodiversity due to numerous human-caused stressors, our understanding of how multiple stressors influence BEF relationships comes largely from small, experimental studies. Here, using remote assemblages of coral reef fishes, we demonstrate strong, non-saturating relationships of biodiversity with two ecosystem functions: biomass and productivity. These positive relationships were robust both to an extreme heatwave that triggered coral bleaching and to invasive rats which disrupt nutrient subsidies from native seabirds. Despite having only minor effects on BEF relationships, both stressors still decreased ecosystem functioning via other pathways. The extreme heatwave reduced biodiversity, which, due to the strong BEF relationships, ultimately diminished both ecosystem functions. Conversely, the loss of cross-system nutrient subsidies directly decreased biomass. These results demonstrate multiple ways by which human-caused stressors can reduce ecosystem functioning, despite robust BEF relationships, in natural high-diversity assemblages. Non-saturating relationships of biodiversity with biomass and productivity are shown in remote assemblages of coral reef fishes. These positive relationships were robust to both an extreme heatwave and invasive rats.
... One such area with this potential is the British Indian Ocean Territory (BIOT), surrounding the Chagos Archipelago in the centre of the Indian Ocean ( Figure 1). The waters within the 200 nautical mile (nmi) exclusive economic zone of BIOT were established as an MPA in 2010 and given full protection as a no-take marine reserve to conserve its biodiversity (Sheppard et al., 2012). Prior to reserve establishment, the British Government granted licences for both longline and purse seine fishing of tuna within the exclusive economic zone of BIOT, but not within 12 nmi of the central atolls (Dunne, Polunin, Sand, & Johnson, 2014). ...
... Overall, purse seine fishing in BIOT contributed just 2.73% of the total purse seine catch of tuna in the Indian Ocean between 1993 and 2008 (Dunne et al., 2014). During the creation of the BIOT MPA, it was suggested that the area was potentially large enough to support the recovery of populations of large, highly mobile pelagic species, including tunas and sharks (Koldewey, Curnick, Harding, Harrison, & Gollock, 2010;Sheppard et al., 2012). However, some studies suggested that, owing to its status as neither a significant tuna fishery nor a potential spawning ground, the BIOT MPA would be ineffective at reducing the impacts of the Indian Ocean tropical tuna fisheries (Kaplan et al., 2014), and models suggested that the closure would have a minor impact on the skipjack tuna population within the Indian Ocean because of the migratory nature of these fish (Dueri & Maury, 2013). ...
... Within the waters of BIOT, the Chagos Archipelago consists of five islanded atolls and several more submerged atolls, including the Great Chagos Bank (Sheppard et al., 2012). Bounds of 64-78°E and 1-12°S were set for the study area to encompass BIOT and its surrounding waters as some fishing sets were recorded just outside of the 200 nmi exclusive economic zone. ...
Article
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Recently, several large marine protected areas (MPAs) have been established globally, and it is hoped that they will aid the recovery of populations of highly mobile, large pelagic species. Understanding the distribution of these species within MPAs is key to delivering effective management, but monitoring can be challenging over such vast areas of open ocean. Historical fisheries data, collected prior to MPA establishment, can provide an insight into the past distributions of target species. We investigated the spatial and temporal distribution of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tuna catch using logbook data from the purse seine fishery in the British Indian Ocean Territory from 1996 to 2010, before it was established as an MPA in April 2010. Generalized additive models were used to predict tuna presence and relative abundance from fishing records in relation to temporal and environmental variables. Significant variables included sea salinity, temperature, and water velocity. Predictions from the models identified a distinct hotspot for large yellowfin tuna within the MPA, and areas of high predicted relative abundance of skipjack tuna. We recommend that these areas are used as focal points from which populations can be monitored and investigations into tuna residency time can occur, so that the effectiveness of the MPA in conserving highly mobile pelagic fish can be determined.
... This study was conducted in the remote Chagos Archipelago (British Indian Ocean Territory), located in the central Indian Ocean (5° 50′S, 72° 00′E). The northern atolls have been uninhabited for approximately 40 years and are relatively free from local human stressors with the exception of invasive rats, which still inhabit some islands following their introduction several hundred years ago (Sheppard et al., 2012). On islands where rats were never introduced, there are large populations of seabirds, including 10 internationally recognized important bird areas (Carr, 2011). ...
... On islands where rats were never introduced, there are large populations of seabirds, including 10 internationally recognized important bird areas (Carr, 2011). The region's coral reefs remain some of the most pristine in the world and are characterized by exceptionally high biomass of fishes, including ecologically important herbivores (Graham & McClanahan, 2013;Graham et al., 2017;MacNeil et al., 2015;Sheppard et al., 2012). However, coral bleaching events have affected reefs in the Chagos Archipelago several times in the past few decades. ...
... This assumption is reasonable given the aforementioned temperature anomalies and evidence of coral bleaching in the Chagos Archipelago during this time (Sheppard et al., 2017), as well as the isolation of the study region from other stressors (e.g. fishing; Graham & McClanahan, 2013;Sheppard et al., 2012). ...
Article
Cross‐ecosystem nutrient subsidies play a key role in the structure and dynamics of recipient communities, but human activities are disrupting these links. Because nutrient subsidies may also enhance community stability, the effects of losing these inputs may be exacerbated in the face of increasing climate‐related disturbances. Nutrients from seabirds nesting on oceanic islands enhance the productivity and functioning of adjacent coral reefs, but it is unknown whether these subsidies affect the response of coral reefs to mass bleaching events or whether the benefits of these nutrients persist following bleaching. To answer these questions, we surveyed benthic organisms and fishes around islands with seabirds and nearby islands without seabirds due to the presence of invasive rats. Surveys were conducted in the Chagos Archipelago, Indian Ocean, immediately before the 2015–2016 mass bleaching event and, in 2018, two years following the bleaching event. Regardless of the presence of seabirds, relative coral cover declined by 32%. However, there was a post‐bleaching shift in benthic community structure around islands with seabirds, which did not occur around islands with invasive rats, characterized by increases in two types of calcareous algae (crustose coralline algae [CCA] and Halimeda spp.). All feeding groups of fishes were positively affected by seabirds, but only herbivores and piscivores were unaffected by the bleaching event and sustained the greatest difference in biomass between islands with seabirds versus those with invasive rats. By contrast, corallivores and planktivores, both of which are coral‐dependent, experienced the greatest losses following bleaching. Even though seabird nutrients did not enhance community‐wide resistance to bleaching, they may still promote recovery of these reefs through their positive influence on CCA and herbivorous fishes. More broadly, the maintenance of nutrient subsidies, via strategies including eradication of invasive predators, may be important in shaping the response of ecological communities to global climate change. The response of coral‐reef communities to a major coral‐bleaching event depended on whether reefs were adjacent to islands with seabirds versus islands that lacked seabirds due to the presence of invasive rats. There was a post‐bleaching shift in benthic communities only around islands with seabirds, characterized by an increase in Halimeda and crustose coralline algae (CCA) (a). Overall fish community structure around both island types shifted following the bleaching event, characterized by a loss of planktivores and corallivores (b). However, biomass of key feeding groups, namely herbivores and piscivores, remained higher around islands with seabirds compared to islands with rats.
... The Chagos Archipelago, known formally as the British Indian Ocean Territory, consists of a series of coral atolls and other submarine features located in the central Indian Ocean (Sheppard et al. 2013). The reefs of Chagos are considered among the most remote in the Indian Ocean and some of the healthiest reefs remaining in the region (Sheppard et al. 2012). The comparatively pristine state of reefs in Chagos led to the majority of the British Indian Ocean Territory to be declared an International Union for Conservation of Nature (IUCN) Category I Protected Area in 2010, becoming the largest no-take marine protected area (MPA) in the world at the time. ...
... The comparatively pristine state of reefs in Chagos led to the majority of the British Indian Ocean Territory to be declared an International Union for Conservation of Nature (IUCN) Category I Protected Area in 2010, becoming the largest no-take marine protected area (MPA) in the world at the time. While the inshore fisheries were already largely inactive at the time of designation, the establishment of the MPA caused the discontinuation of an active pelagic longline tuna fishery in the archipelago (Sheppard et al. 2012). ...
... Diego Garcia is the only island with modern infrastructure, making any visits to other atolls challenging and costly. This lack of development, however, means the majority of Chagos reefs have avoided the effects of stressors related to coastal development, such as pollution and sedimentation, which have contributed to coral reef decline in many parts of the world (Sheppard et al. 2012). ...
Chapter
The Chagos Archipelago, located in the central Indian Ocean and officially known as the British Indian Ocean Territory, contains some of the most remote reefs in the Indian Ocean. The Chagos Archipelago is comprised of a series of atolls, including the largest atoll in the world, the Great Chagos Bank. Records from surveys of mesophotic coral ecosystems (MCEs; reefs 30–150 m depth) in Chagos stretch back to 1905, with more extensive work conducted in the 1970s and post-2010. Coral and fish communities vary considerably with depth and among habitat types. Coral cover generally declines with increased depth across the shallow reef to MCE depth gradient, though in several locations close to 100% scleractinian coral cover has been observed on MCEs. Consistent with earlier studies, we identify five coral species as indicative of Chagos MCEs. Recently collected fish community data are analyzed to illustrate, for the first time, patterns in reef fish species richness, abundance, biomass, and trophic groups across a shallow to upper-MCE depth gradient (0–60 m). Fish species richness, abundance, and biomass declined with increased depth, while richness, abundance, and trophic group patterns were also influenced by habitat type (seaward versus lagoonal reef). To date, the vast majority of MCE research in Chagos has focused on upper mesophotic depths. We recommend future work consider the full MCE depth range within the Chagos Archipelago.
... Bottom right legend showing instrument configurations of the long thermistor string (red dot/pin) and subsurface ADCP moorings (yellow dot/pin) deployed 182 m apart anchored at a depth of 66 m. Z is the height above the seabed Garcia Atoll; Sheppard et al., 2012). Due to the lack of human influence, such as coastal development and anthropogenic pollution, the region is considered virtually pristine (Readman et al., 2013). ...
... Due to the lack of human influence, such as coastal development and anthropogenic pollution, the region is considered virtually pristine (Readman et al., 2013). Owing to the region's unique marine environment, a no-take marine protected area (MPA), which encompasses the entire exclusive economic zone (EEZ; 640,000 km 2 ) except for a 3 nm exclusion around the boundary of Diego Garcia Atoll, was established in 2010 (Sheppard et al., 2012). The archipelago supports a subpopulation of M. alfredi which is largely undocumented due to the remoteness of the location and strict protective measures; as is the region's physical oceanographic environment . ...
Article
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Globally, reef manta rays (Mobula alfredi) are in decline and are particularly vulnerable to exploitation and disturbance at aggregation sites. Here, passive acoustic telemetry and a suite of advanced oceanographic technologies were used for the first time to investigate the fine-scale (5-min) influence of oceanographic drivers on the visitation patterns of 19 tagged M. alfredi to a feeding aggregation site at Egmont Atoll in the Chagos Archipelago. Boosted regression trees indicate that tag detection probability increased with the intrusion of cold-water bores propagating up the atoll slope through the narrow lagoon inlet during flood tide, potentially transporting zooplankton from the thermocline. Tag detection probability also increased with warmer near-surface temperature close to low tide, with near-surface currents flowing offshore, and with high levels of backscatter (a proxy of zooplankton biomass). These combinations of processes support the proposition that zooplankton carried from the thermocline into the lagoon during the flood may be pumped back out through the narrow inlet during an ebb tide. These conditions provide temporally limited feeding opportunities for M. alfredi, which are tied on the tides. Results also provide some evidence of the presence of Langmuir Circulation, which transports and concentrates zooplankton, and may partly explain why M. alfredi occasionally remained at the feeding location for longer than that two hours. Identification of these correlations provides unique insight into the dynamic synthesis of fine-scale oceanographic processes which are likely to influence the foraging ecology of M. alfredi at Egmont Atoll, and elsewhere throughout their range.
... The MPA includes a range of habitats with deep oceanic areas surrounding the shallow reef environments and reef islands of the Chagos Archipelago. Its recognition as an important site for conservation (reviewed previously by Sheppard et al. 2012) has helped drive a concerted programme of ongoing studies to understand the outcomes of the MPA's creation and its importance for the species and ecosystems it hosts. At the same time, the legality of this MPA has been challenged (Appleby 2015;United Nations 2019). ...
... Data collected following the major coral bleaching event of 1998 showed that despite its geographically isolated position, the Chagos Archipelago was not immune from widespread coral mortality, which extended to depths of > 40 m in some locations (Sheppard et al. 2012). However, most of the reefs recovered quickly and by 2012 coral cover on reefs in the BIOT MPA averaged 40-50% (Fig. 3a, d), with juvenile coral densities of 20-60 colonies m −2 ( Fig. 3b) (Sheppard et al. 2017;Sheppard and Sheppard 2019). ...
Article
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Given the recent trend towards establishing very large marine protected areas (MPAs) and the high potential of these to contribute to global conservation targets, we review outcomes of the last decade of marine conservation research in the British Indian Ocean Territory (BIOT), one of the largest MPAs in the world. The BIOT MPA consists of the atolls of the Chagos Archipelago, interspersed with and surrounded by deep oceanic waters. Islands around the atoll rims serve as nesting grounds for sea birds. Extensive and diverse shallow and mesophotic reef habitats provide essential habitat and feeding grounds for all marine life, and the absence of local human impacts may improve recovery after coral bleaching events. Census data have shown recent increases in the abundance of sea turtles, high numbers of nesting seabirds and high fish abundance, at least some of which is linked to the lack of recent harvesting. For example, across the archipelago the annual number of green turtle clutches (Chelonia mydas) is ~ 20,500 and increasing and the number of seabirds is ~ 1 million. Animal tracking studies have shown that some taxa breed and/or forage consistently within the MPA (e.g. some reef fishes, elasmobranchs and seabirds), suggesting the MPA has the potential to provide long-term protection. In contrast, post-nesting green turtles travel up to 4000 km to distant foraging sites, so the protected beaches in the Chagos Archipelago provide a nesting sanctuary for individuals that forage across an ocean basin and several geopolitical borders. Surveys using divers and underwater video systems show high habitat diversity and abundant marine life on all trophic levels. For example, coral cover can be as high as 40-50%. Ecological studies are shedding light on how remote ecosystems function, connect to each other and respond to climate-driven stressors compared to other locations that are more locally impacted. However, important threats to this MPA have been identified, particularly global heating events, and Illegal, Unreported and Unregulated (IUU) fishing activity, which considerably impact both reef and pelagic fishes.
... Chagos is situated in a region characterized by monsoon climate (Sheppard et al., 2012). The austral summer is the wet season, with the Northeast monsoon lasting form October to February (Pfeiffer et al., 2004). ...
... The SCTR is believed to play a major role in the climate variability of this region on different timescales (e.g. Hermes & Reason, 2008;Vialard et al., 2009) with very strong air-sea interaction due to open 75 ocean upwelling combined with relatively warm SST (Sheppard et al., 2012). ...
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Abstract. The dominant modes of climate variability on interannual timescales in the tropical Indian Ocean are the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole. El Niño events have occurred more frequently during recent decades and it has been suggested that an asymmetric ENSO teleconnection (warming during El Niño events is stronger than cooling during La Niña events) caused the pronounced warming of the western Indian Ocean. In this study, we test this hypothesis using coral Sr / Ca records from the central Indian Ocean (Chagos Archipelago) to reconstruct past sea surface temperatures (SST) in time windows from the Maunder Minimum to the present. Three sub-fossil massive Porites corals were dated to the 17–18th century (one sample) and 19–20th century (two samples), and were compared with a published, modern coral Sr / Ca record from the same site. All corals were sub-sampled at a monthly resolution for Sr / Ca measurements, which were measured using a simultaneous ICP-OES. All four coral records show typical ENSO periodicities, suggesting that the ENSO-SST teleconnection in the central Indian Ocean was stationary since the 17th century. To determine the symmetry of ENSO events, we compiled composite records of positive and negative ENSO-driven SST anomaly events. We find similar magnitudes of warm and cold anomalies indicating a symmetric ENSO response in the tropical Indian Ocean. This suggests that ENSO is not the main driver of central Indian Ocean warming.
... The BIOT MPA comprises a large archipelago of atoll-based reefs and submerged banks in the central Indian Ocean. The MPA is a designated no-take marine reserve of approximately 640 000 km 2 which includes all of the atolls and waters of the BIOT exclusive economic zone (EEZ), with the exception of a small recreational fishery in the atoll of Diego Garcia (Sheppard et al. 2012). There are currently no human inhabitants within the archipelago, aside from those associated with the military base on Diego Garcia. ...
... Seasonality in manta oc currence has previously been associated with both monsoonal cycles and their consequent effects on oceanographic conditions and productivity (Anderson et al. 2011, Setyawan et al. 2018, Peel et al. 2019b) as well as manta reproductive cycles (Marshall et al. 2011). As climate observations in the BIOT region are extremely sparse (Sheppard et al. 2012) and we lacked the metadata to assess the reproductive status of tagged mantas, it is difficult to disentangle these effects in the present study. It is worth noting, however, that the tuna purse-seine fishery catch historically peaked in BIOT waters in December and January (Mees et al. 2009, Dunn & Curnick 2019, suggesting high primary productivity in the water column at this time. ...
Article
Mobulid populations are declining on a global scale as a result of both targeted fisheries and indirect anthropogenic threats. In order to implement effective conservation strategies for species of this taxa, it is crucial that movement patterns at a range of spatiotemporal scales are defined. To gain insight into such patterns, we deployed a combination of acoustic (n = 21) and satellite (n = 12) tags on reef manta rays Mobula alfredi in the British Indian Ocean Territory Marine Protected Area (BIOT MPA) annually from 2013 through 2016. An extensive array of acoustic receivers (n = 52) were deployed across the archipelago to record the movements of mantas throughout the MPA. Data revealed large individual variation in horizontal movement patterns, ranging from high local site fidelity (<10 km) for up to 3 yr, to large-scale regional movements (>200 km) around the entire MPA. Depth time-series data recorded vertical movement patterns consistent with other epipelagic elasmobranch species, including oscillatory diving and deep dives to greater than 500 m. Though no individuals were directly recorded departing the MPA throughout the study, the gaps in detections and estimated travel speeds documented here indicate that movement of individuals outside of the BIOT MPA cannot be discounted. Collectively, our data suggests that, with effective enforcement, the current size of the BIOT MPA is providing substantial protection to its reef manta ray population. Characterization of movement patterns across ontogenetic classes, however, is required to fully characterize the spatial ecology of this species and ensure protection across all cohorts of the population.
... The BIOT MPA comprises a large archipelago of atoll-based reefs and submerged banks in the central Indian Ocean. The MPA is a designated no-take marine reserve of approximately 640 000 km 2 which includes all of the atolls and waters of the BIOT exclusive economic zone (EEZ), with the exception of a small recreational fishery in the atoll of Diego Garcia (Sheppard et al. 2012). There are currently no human inhabitants within the archipelago, aside from those associated with the military base on Diego Garcia. ...
... Seasonality in manta oc currence has previously been associated with both monsoonal cycles and their consequent effects on oceanographic conditions and productivity (Anderson et al. 2011, Setyawan et al. 2018, Peel et al. 2019b) as well as manta reproductive cycles (Marshall et al. 2011). As climate observations in the BIOT region are extremely sparse (Sheppard et al. 2012) and we lacked the metadata to assess the reproductive status of tagged mantas, it is difficult to disentangle these effects in the present study. It is worth noting, however, that the tuna purse-seine fishery catch historically peaked in BIOT waters in December and January (Mees et al. 2009, Dunn & Curnick 2019, suggesting high primary productivity in the water column at this time. ...
... Worldwide, there are seven extant species of marine turtles that inhabit nearly all oceans and occupy broad geographical ranges (Wallace et al. 2010a). Populations nesting on beaches and feeding on waters of the African continent are globally significant with representative numbers of leatherbacks in Gabon (Fossette et al. 2008), loggerheads in Oman (Rees et al. 2010) and Cape Verde (Marco et al. 2011), greens in Guinea Bissau (Catry et al. 2002 and hawksbills in the Seychelles (Sheppard et al. 2012) and the Chagos Archipelago (Mortimer 1984;Sheppard et al. 2012). Five species of marine turtles nest in Mozambique: greens, hawksbills, leatherbacks, loggerheads and olive ridleys (Louro et al. 2006). ...
... Worldwide, there are seven extant species of marine turtles that inhabit nearly all oceans and occupy broad geographical ranges (Wallace et al. 2010a). Populations nesting on beaches and feeding on waters of the African continent are globally significant with representative numbers of leatherbacks in Gabon (Fossette et al. 2008), loggerheads in Oman (Rees et al. 2010) and Cape Verde (Marco et al. 2011), greens in Guinea Bissau (Catry et al. 2002 and hawksbills in the Seychelles (Sheppard et al. 2012) and the Chagos Archipelago (Mortimer 1984;Sheppard et al. 2012). Five species of marine turtles nest in Mozambique: greens, hawksbills, leatherbacks, loggerheads and olive ridleys (Louro et al. 2006). ...
... This was followed by well-protected, moderate protection and fished areas that were categorised as lightly, moderately, and heavily populated, respectively (Table 1). Highly protected areas were located in remote areas with very low human population and also showed relatively high compliance with no-take zone (NTZ) management rules (Sheppard et al., 2012), therefore the reef system was considered as a remote highly protected area. ...
... Planktivorous fish rely on allochthonous planktonic food materials including pelagic zooplankton, and are more abundant in exposed reef areas, where suspended food levels are high (McLachlan and Defeo, 2017). The high biomass in highly protected areas in this study may have been driven by the high abundance of pelagic zooplankton resulting from upwelling along the Seychelles-Chagos ridge (Sheppard et al., 2012). Significant inter-atoll differences in planktivores have been reported in these areas and such localised processes coupled with fishing effects are important in understanding the dynamics in abundance of planktivorous fishes. ...
Article
Understanding how Marine Protected Areas (MPAs) improve conservation outcomes across anthropogenic pressures can improve the benefits derived from them. Effects of protection for coral reefs in the western and central Indian Ocean were assessed using size-spectra analysis of fish and the relationships of trophic group biomass with human population density. Length-spectra relationships quantifying the relative abundance of small and large fish (slope) and overall productivity of the system (intercept) showed inconsistent patterns with MPA protection. The results suggest that both the slopes and intercepts were significantly higher in highly and well-protected MPAs. This indicates that effective MPAs are more productive and support higher abundances of smaller fish, relative to moderately protected MPAs. Trophic group biomass spanning piscivores and herbivores, decreased with increasing human density implying restoration of fish functional structure is needed. This would require addressing fisher needs and supporting effective MPA management to secure ecosystem benefits for coastal communities.
... These islands are fewer and smaller than those of the Maldives or Laccadive Archipelagos. Like atoll islands globally, the Chagos Islands are low lying (only 2-5 m above sea level) and are typical coral cays constructed of limestone with underlying freshwater lenses sustained by rainfall (Graham et al., 2009;Sheppard et al., 2012;Purkis et al., 2016a). Of the 21 Chagos islands considered by this study, including 20 islands on Peros Banhos and 1 island on Diego Garcia, only the one atop Diego Garcia Atoll is inhabited. ...
... The Chagos climate is tropical and moderated by the trade winds (Eisenhauer et al., 1999). Until very recently, the archipelago's reefs were noteworthy for their health and vitality, in no small part aided by the 2010 declaration of the Chagos Marine Protected Area, which, at the time, was the world's largest Sheppard et al., 2012). By virtue of coral bleaching, however, the Chagos reefs have suffered gravely in the last five years (Sheppard et al., 2017(Sheppard et al., , 2020. ...
Article
This study calls upon recently discovered aerial photographs for two atolls in the Indian Ocean Chagos Archipelago. Pairing these vintage data with modern satellite imagery allows the coastline dynamics of a suite of islands to be quantified over a 36-to-50-yr. period. Peros Banhos represents one of the few atolls globally where natural island dynamics can be appraised; withstanding just one of its 35 islands, this atoll has never been settled by humans. By contrast, Diego Garcia has undergone pronounced anthropogenic change in the last fifty years. Statistics bring new insights to the persistence of these atoll islands under the contemporary conditions of sea level rise. Key findings include: (i) Coastlines facing the prevailing trade winds retreat through time, while those in leeward positions expand; (ii) coastline expansion and retreat are in balance such that total land area of all the considered islands is virtually static over the last 50 years; and, (iii) small islands (<20 ha) are substantially more dynamic than large ones. The stretches of the Diego Garcia coastline in close vicinity to human modification are more likely to suffer erosion than those situated far from human activity, and also substantially more likely to erode, than those of the uninhabited islands of Peros Banhos. A comparison between the behavior of a broad portfolio of islands spanning the Indian and Pacific Oceans emphasizes local factors such as wind direction, to be better determinants of coastline dynamics than global factors, such as the rate of eustatic sea-level rise. In aggregate, our data suggest that atoll islands are likely to persist in the face of accelerating sea-level rise over the next decades, but their high rate of coastline dynamics will challenge human habitability.
... The Chagos archipelago is a remote oceanic atoll system situated in the centre of the Indian Ocean (Figure 1). The archipelago is comprised of 58 small islands, sitting on a limestone platform surrounded by coral reefs, submerged banks, and deep-water ecosystems (Sheppard et al. 2012). In 2010, the archipelago and surrounding waters of the British Indian Ocean Territory (BIOT) were designated by the United Kingdom as a strict no-take marineprotected area, encompassing a total area of 640,000 km 2 . ...
... The remote and protected nature of this archipelago may provide some explanation to these multiple sightings of co-operative hunting, with the lack of human disturbance potentially allowing natural behaviours to be observed more readily, consistent with other studies of differing fish 'flight'/predation behaviour from this reef system (Sheppard et al. 2012;Januchowski-Hartley et al. 2015), and from other isolated oceanic atolls (Sazima et al. 2007;Quimbayo et al. 2014) or highly protected areas (Pereira et al. 2011;Unsworth and Cullen-Unsworth 2012). ...
Article
Inter-specific hunting associations can occur across a range of marine species to facilitate prey capture through co-operative behaviour. Here we describe multiple transient cross-phyla associations between day octopus (Octopus cyanea) and three fish species, including peacock grouper (Cephalopholis argus), brown-marbled grouper (Epinephelus fuscoguttatus), and gold-saddle goatfish (Parupeneus cyclostomus), in the isolated reef system of the Chagos archipelago. Observations of such hunting associations are rare, and no similar observations have been recorded for this region. The remoteness of this study site may provide some explanation for these multiple sightings, allowing natural behaviours to occur undisturbed. However, given no previous sightings of such behaviour, the limitation of available food resources following two recent mass coral mortality episodes, may have necessitated the formation of these rare/novel hunting interactions. Intensified prey scarcity and increasingly degraded habitat structure following more frequent disturbance events may therefore lead to such indirect environmentally mediated behavioural responses becoming increasingly prevalent in reef-dwelling species.
... The only resident human population in the BIOT MPA is based on Diego Garcia, in the south east of the MPA, where approximately 3,000 individuals support a joint United Kingdom-United States military base. Its remote location and low population density means that the MPA is relatively free from local anthropogenic effects (Sheppard et al., 2012) and therefore boasts a relatively high reef fish biomass and abundance of top predators . However, the MPA has been targeted by illegal, unreported and unregulated fishing (IUU) (IOTC-2015-WPEB11-48), predominantly by vessels from India and Sri Lanka fishing for sharks (Graham et al., 2010), a problem that continues to be a significant management concern (Ferretti et al., 2018;Tickler et al., 2019). ...
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Marine protected areas (MPAs) have become an increasingly important tool to protect and conserve marine resources. However, there remains much debate about how effective MPAs are, especially in terms of their ability to protect mobile marine species such as teleost and chondrichthyan fishes.We used satellite and acoustic tags to assess the ability of a large oceanic MPA, the British Indian Ocean Territory MPA (BIOT MPA), to protect seven species of pelagic and reef-associated teleost and chondrichthyan fishes. We satellite-tagged 26 animals from six species (Blue Marlin, Reef Mantas, Sailfish, Silky Sharks, Silvertip Sharks, and Yellowfin Tuna), producing 2,735 days of movement data. We also acoustically tagged 121 sharks from two species (Grey Reef and Silvertip Sharks), which were monitored for up to 40 months across a large acoustic receiver array spanning the MPA. We found that the activity spaces of all satellitetagged animals, including pelagic species, were much smaller than the area of the BIOT MPA, even taking into account errors associated with position estimates. Estimates of space use of acoustically tagged sharks, based on dynamic Brownian Bridge Movement Models (dBBMM), were also much smaller than the size of the MPA. However, we found important limitations when using dBBMM and demonstrate its sensitivity to both study duration and array design. We found that Grey Reef Sharks should be monitored for at least 1 year and Silvertip Sharks for 2 years before their activity space can be effectively estimated. We also demonstrate the potentially important role that intraspecific variability in spatial ecology may play in influencing the ability of MPAs to effectively protect populations of mobile species. Overall, our results suggest that, with effective enforcement, MPAs on the scale of the BIOT MPA potentially offer protection to a variety of pelagic and reef species with a range of spatial ecologies. We suggest that animals need to be tagged across seasons, years, and ontogenetic stages, in order to fully characterize their spatial ecology, which is fundamental to developing and implementing effective MPAs to conserve the full life history of target species.
... Protecting biodiversity and increasing productivity Halpern and Warner, 2002Mumby et al. 2007Russ and Alcala, 1996Lester et al. 2009 Lack of proper resources, planning, or enforcement mechanisms Bruner et al. 2004Byers and Noonburg, 2007Guidetti et al. 2008McCay and Jones, 2011McClanahan et al. 2006Rife et al. 2013Rojas-Bracho et al. 2006 Providing Ecosystem Services Potts et al. 2014Leenhardt et al. 2015Xu et al. 2017 Increasing ecologic resilience Babcock et al. 2010White et al. 2012 Increasing recreational and tourism opportunities Taylor and Buckenham, 2003Weiant and Aswani, 2006Hayes et al. 2015 Tourism Harriott et al. 1997 Enhacing of fisheries Gell and Roberts, 2003Harrison et al. 2012Moland et al. 2013 Negative impacts on fisheries Caveen et al. 2014 Cost Balmford et al. 2003 Costs and/or legal context Lowry et al. 2009McCrea-Strub et al. 2011 Supporting health, social or cultural values Aswani and Furusawa, 2007Cinner et al. 2005Gjertsen, 2005Pollnac et al. 2010 Social constraints Bennett and Dearden, 2014Himes, 2007Mascia et al. 2010West et al. 2006 Protecting specific habitats, species or functional groups Fish, Russ and Alcala, 1996 Megafauna, Penguins, Pichegru et al. 2010Sharks, Knip et al. 2012Dolphins, Pérez-Jorge et al. 2015Seabirds, Maxwell et al. 2016 Coral reefs, Mcclanahan et al. 2007 Habitats, Fraschetti et al. 2013 Disadvantages of very large marine protected areas and/or rush to achieve percentage targets Agardy et al. 2011De Santo, 2013Devillers et al. 2015Jones and De Santo, 2016Sheppard et al. 2012Singleton and Roberts, 2014Wood, 2011 Despite some ongoing debate on conservation needs and priorities, MPAs have materialized as a mainstream management tool for promoting long-term conservation and sustainable use of marine resources (Halpern and Warner, 2002), and symbolize a key task for different EU coastal, marine and biodiversity policies. Still, the progress towards protecting coastal and marine areas has been much slower than their terrestrial equivalent ( Fig. 1.1, Watson et al. 2014). ...
... The rapid rate of climate change will make acclimatization, or compensatory physiological changes to a new environment, a potentially important factor in the short-term survival of reefs (Edmunds & Gates 2008), as reefs will likely experience significant bleaching events on a yearly basis by 2050 . Acclimatization could be achieved through shifts in the symbiont community at the individual colony scale after thermal stress (Buddemeier & Fautin 1993, McClanahan 2000, Loya et al. 2001, Edmunds & Gates 2008, Jones et al. 2008, Sheppard et al. 2012, Baker et al. 2013, Cunning et al. 2015. However, symbiont shifting in corals in response to thermal stress is not shared universally, sparking a debate about the capabilities of corals themselves to acclimatize to increases in seawater temperatures (Hoegh-Guldberg 1999, Coles & Brown 2003, Edmunds & Gates 2008, van Hooidonk et al. 2013. ...
... Regional-scale coral reef mapping from remote sensing has a role to play in the widening portfolio of intervention measures that are being mobilized against the reef crisis. Of these measures, the establishment of large-scale marine protected areas (MPAs) has been particularly effective (Sheppard et al. 2012;Toonen et al. 2013;Wilhelm et al. 2014). The Big Ocean Network (https://bigoceanmanagers. org-accessed 10/25/2018) provides a rule of thumb as to what constitutes 'large scale,' with their 17 member sites ranging in size from approximately 150,000 sq. ...
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With compelling evidence that half the world’s coral reefs have been lost over the last four decades, there is urgent motivation to understand where reefs are located and their health. Without such basic baseline information, it is challenging to mount a response to the reef crisis on the global scale at which it is occurring. To combat this lack of baseline data, the Khaled bin Sultan Living Oceans Foundation embarked on a 10-yr survey of a broad selection of Earth’s remotest reef sites—the Global Reef Expedition. This paper focuses on one output of this expedition, which is meter-resolution seafloor habitat and bathymetry maps developed from DigitalGlobe satellite imagery and calibrated by field observations. Distributed on an equatorial transect across 11 countries, these maps cover 65,000 sq. km of shallow-water reef-dominated habitat. The study represents an order of magnitude greater area than has been mapped previously at high resolution. We present a workflow demonstrating that DigitalGlobe imagery can be processed to useful products for reef conservation at regional to global scale. We further emphasize that the performance of our mapping workflow does not deteriorate with increasing size of the site mapped. Whereas our workflow can produce regional-scale benthic habitat maps for the morphologically diverse reefs of the Pacific and Indian oceans, as well as the more depauperate reefs of the Atlantic, accuracies are substantially higher for the former than the latter. It is our hope that the map products delivered to the community by the Living Oceans Foundation will be utilized for conservation and act to catalyze new initiatives to chart the status of coral reefs globally.
... While coastal, benthic MPAs have been shown to generate positive outcomes on average, there remains substantial uncertainty over the feasibility of pelagic MPAs to achieve these and other ecological objectives (Botsford et al. 2003, Hilborn et al. 2004a, b, Kaiser 2005, Le Quesne and Codling 2009, Davies et al. 2012, Graham et al. 2012, Hazen et al. 2013. Despite these uncertainties, over the past decade there has been a proliferation of large-scale MPAs that either include or are exclusively pelagic habitat in which pelagic fishing is restricted (Fernandes et al. 2005, Sheppard et al. 2012, Gannon et al. 2017. These pelagic MPAs support progress toward achieving the area-based goal of Aichi Biodiversity Target 11-also adopted as Sustainable Development Goal (SDG) target 14.5 -which calls for 10% of coastal and marine areas by 2020 to be conserved through ecologically representative and well-connected systems of MPAs and other effective area-based conservation approaches (CBD 2011, UNGA 2015a, Rice et al. 2018. ...
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There has been a recent proliferation of large-scale marine protected areas (MPAs) containing pelagic habitats. These contribute substantially towards meeting the area-based goal of Aichi Biodiversity Target 11 and to managing pelagic ecosystem pressures, including fishing. We assessed theoretical and empirical evidence for the achievement of ecological objectives by static and dynamic spatial management of pelagic fisheries. Exceptionally few studies have assessed ecological responses to MPAs that constrain pelagic fisheries, leaving substantial uncertainty over their efficacy. Assessments have provided a limited basis for causal inferences, and have not evaluated whether other management tools would be more effective. Pelagic MPAs have relatively high promise to mitigate fisheries bycatch of species of conservation concern with ‘slow’ life history traits and that form temporally and spatially predictable hotspots, and for some species, to protect habitats important for critical life history stages. It would be challenging to design MPAs to maintain absolute biomass levels of target stocks near targets and above limits: MPAs would need to be extensive to account for broad and variable distributions, and account for catch risk outside of the MPA, including from displaced fishing effort and fishing-the-line. For non-overexploited stocks, which is the status of most target pelagic species and their prey, there would likely be little response in absolute stock biomass to an MPA. While pelagic MPAs have a higher promise of increasing target stocks’ local abundance, evidence with a robust basis for inferring causality is needed. Reducing fishing mortality of prey species might not affect the biomass of their pelagic predators because prey species experience light fishing pressure and because there may be a weak correlation between the absolute abundance of forage fish and their predators. There is an especially limited basis for predicting the effects of MPAs on fisheries-induced evolution (FIE) in pelagic species. We describe how pelagic MPAs could be designed to achieve five ecological objectives without causing cross-taxa conflicts and exacerbating FIE. To fill substantial gaps in knowledge, we prescribe counterfactual-based modeling of time series data of standardized catch records to infer causation in assessments of ecological responses to pelagic MPAs.
... Failure to secure governance as a means to cooperative management can undermine conservation intentions. As an extreme example, the legality of the Chagos Archipelago MPA is now in question despite it's scientific credentials (the area recovered within 10 years from the 1998 coral bleaching event to boast 20-50% of the Indian ocean reef area remaining in excellent condition (Sheppard et al., 2012)). ...
... All the coral diseases recorded during this study have been previously reported at other localities across the Indian Ocean, including Reunion and Mayotte (Séré et al., 2015b), the Chagos Archipelago (Sheppard et al., 2012), Republic of Maldives (Onton et al., 2011), South India (Thinesh et al., 2009(Thinesh et al., , 2011, and generally within the Indo-Pacific region (Willis et al., 2004;Raymundo et al., 2005;Aeby et al., 2006). The average disease prevalence at Sodwana Bay was higher than that found at Mayotte (2.7%; Séré et al., 2015a) and at other Indian Ocean localities such as Ningaloo Reef in Australia (2.3%; Onton et al., 2011) and the Maldives (< 2%; Montano et al., 2012). ...
Article
Coral communities are found at high latitude on the East Coast subtropical reefs of South Africa. They are biodiverse, economically important, and afforded World Heritage Site status in the iSimangaliso Wetland Park where some are subjected to recreational use. While the Park's unique coral reefs have, to date, suffered little bleaching from climate change, they are susceptible to the phenomenon and provide a natural laboratory for the study of its effects at high latitude. This review covers recent advances in the regional oceanography; coral community dynamics and the underpinning reef processes, including minor bleaching events; the incidence of coral disease; and coral genetic connectivity. The effects of human activity (SCUBA diving, recreational fishing, pesticide use) were assessed, as well as the nursery benefits of Acropora austera, a coral which provides the reefs with much structure and is vulnerable to damage and climate change. The reefs were valued in terms of human use as well as services such as sediment generation and retention. The results have provided valuable information on relatively pristine, high-latitude reefs, their socioeconomic benefits, and the anticipated effects of climate change.
... The Chagos Archipelago (Fig. 1) is located within the central Indian Ocean and hosts the world's second largest no-take Marine Protected Area (MPA). It is considered a 'hotspot' of marine biodioversity and abundance, with coral reef fish abundance an order of magnitude higher than other areas of the Indian Ocean (Sheppard et al., 2012). Within a largely oligotrophic ocean (Morel et al., 2010), the archipelago is readily visible in remotely sensed images of chlorophyll-a (Fig. 1b), suggestive of local processes sustaining higher levels of primary production than those observed in the surrounding ocean. ...
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Oceanographic observations were made with a subsurface oceanographic mooring over the summit and flanks of two neighbouring seamounts in the tropical Indian Ocean to identify processes that may be responsible for the aggregation of silvertip sharks (Carcharhinus albimarginatus) in the deep water drop-off surrounding the summits. The seamounts, which are in the Chagos Archipelago in the British Indian Ocean Territories, are narrow in horizontal extent (<10 km), have steeply sloping (>15°) sides that rise from depths of >600 m, and flat summits at a depth of 70 m. They are subjected to forcing at subinertial, basin-scales and local scales that include a mixed tidal regime and storm-generated near inertial waves. At the drop-off, at a depth of between 70 – 100 m, isotherms oscillate at both diurnal and semidiurnal frequencies with amplitudes of ∼20-30 m. The waves of tidal origin are accompanied by short period (∼5 minutes) internal waves with amplitudes O(10 m) and frequencies close to the local buoyancy frequency, N, within the thermocline which is the maximum frequency possible for freely propagating internal waves. The tidal oscillations result from internal lee waves with 30 m vertical wavelength generated by the prevailing currents over the supercritical seamount flanks, whereby the bottom slope is greater than the internal tide wave slope. The ‘near-N’ waves are due to enhanced shear associated with the hydraulic jumps that form from the lee waves due to the abrupt transition from steeply sloping sides to a relatively flat summit. The jumps manifest themselves as bottom-trapped bores that propagate up the slope towards the summit. Further observations over the summit reveal that the bores subsequently flush the summits with cold water with tidal periodicity. The bores, which have long wave phase speeds more than double that of the bore particle velocities, are characterised by intense vertical velocities (>0.1 m s-1) and inferred local resuspension but relatively little turbulence based on temperature overturns. Our results strongly implicate lee waves as the dynamic mechanism of leading order importance to the previously observed accumulation of biomass adjacent to the supercritical slopes that are commonplace throughout the archipelago. We propose that further investigation should identify the spatiotemporal correlation between internal wave activity and fish schooling around the summit, and whether such schooling attracts predators.
... As such, day was designated from 0700 to 1900 and night from 1900 to 0700 following sunrise and sunset times obtained from https://www.timeanddate.com. The MPA experiences distinct Indian Ocean wet and dry seasons with wet season running from October to March, and dry season from April to September (64). Seasonal variability is often greater than monthly variability in tropical ocean systems (65,66), and, therefore we deemed season a more biologically relevant driver of shark movement. ...
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Background There are now a wide array of field and laboratory techniques available for gaining insight into the movement and behaviour of sharks. Although acoustic telemetry may lack the fine-scale resolution of satellite telemetry, the low cost and longer battery life make it a powerful tool for investigating elasmobranch behaviour. Here, in the absence of satellite tracking data, we develop a novel approach to analysing acoustic telemetry data, using detection gaps to infer movement patterns to and from monitored reef habitats, to investigate spatial and temporal segregation between two sympatric shark species in a large remote MPA. Methods A total of 102 grey reef and 76 silvertip sharks were fitted with long-term acoustic transmitters and tracked inside a large acoustic array of reef-based receivers in the British Indian Ocean Territory MPA, between 2014 and 2018. From the resulting dataset (768,081 movements), movements between receivers and recursive loops to the same receiver were identified. Using the durations of inter-receiver movements (i.e. detection gaps), individual behaviours were classified into ‘restricted’ or ‘wider ranging’ movements. Drivers of these movements were identified using network analysis, generalised linear mixed models and multi-model inference starting from an a priori set of explanatory variables. Results In general, silvertip sharks were more likely to undertake ‘wider ranging’ movements than grey reef sharks. ‘Wider ranging’ movements were more common at night compared to during the day, and during the wet season compared to the dry season. In addition, the difference in ‘wider ranging’ movements between the two species increased at night. These results suggest spatial segregation and temporal segregation of movements between grey reef and silvertip sharks in the region. Conclusions We present a novel analysis of detection gaps from acoustic telemetry data to infer differential movement patterns and describe how species organise in space and time. Furthermore, this approach shows that acoustic telemetry gap analysis can be used for comparative studies, or combined, with other research techniques to better understand the functional role of sharks in reef ecosystems, moving towards more informed strategies for the conservation and management of the marine environment.
... The British Indian Ocean Territory (BIOT) is a region of the Indian Ocean encompassing a variety of undersea features, including the flat shallow banks of the Chagos Archipelago, and the high slopes of the Chagos-Laccadive ridge, and depths beyond 5000 m [19]. The area could be home to as many as 86 seamounts, based on estimates from an automated seamount-recognition algorithm applied to version 6 of the SRTM30 PLUS global bathymetry grid [11]. ...
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Seamounts are important marine habitats that are hotspots of species diversity. Relatively shallow peaks, increased productivity and offshore locations make seamounts vulnerable to human impact and difficult to protect. Present estimates of seamount numbers vary from anywhere between 10,000 to more than 60,000. Seamount locations can be estimated by extracting large, cone-like features from bathymetry grids (based on criteria of size and shape). These predicted seamounts are a useful reference for marine researchers and can help direct exploratory surveys. However, these predictions are dependent on the quality of the surveys underpinning the bathymetry. Historically, quality has been patchy, but is improving as mapping efforts step up towards the target of complete seabed coverage by 2030. This study presents an update of seamount predictions based on SRTM30 PLUS global bathymetry version 11 and examines a potential source of error in these predictions. This update was prompted by a seamount survey in the British Indian Ocean Territory in 2016, where locations of two putative seamounts were visited. These ‘seamounts’ were targeted based on previous predictions, but these features were not detected during echosounder surveys. An examination of UK hydrographic office navigational (Admiralty) charts for the area showed that the summits of these putative features had soundings reporting ‘no bottom detected at this depth’ where ‘this depth’ was similar to the seabed reported from the bathymetry grids: we suspect that these features likely resulted from an initial misreading of the charts. We show that 15 ‘phantom seamount’ features, derived from a misinterpretation of no bottom sounding data, persist in current global bathymetry grids and updated seamount predictions. Overall, we predict 37,889 seamounts, an increase of 4437 from the previous predictions derived from an older global bathymetry grid (SRTM30 PLUS v6). This increase is due to greater detail in newer bathymetry grids as acoustic mapping of the seabed expands. The new seamount predictions are available at https://doi.pangaea.de/10.1594/PANGAEA.921688.
... Notwithstanding these apparent anomalies, in October 2011, the BIOT Director of Fisheries reported that: "We take the management of recreational fishing seriously and discuss regularly with the US ways to keep standards high" and that "We are satisfied from the available reports of the (Koldewey et al., 2010b) and a subsequent review by Sheppard et al. (2012b) similarly makes almost no mention of recreational fishing. A recent examination of the coral reef fish biomass and trophic structure in the Chagos is the first to analyse the possible effects of recreational fishing at Diego Garcia, assessing reef fish biomass at 18 sites in the northern atolls and the Great Chagos Bank in 2010 and comparing these to 6 reef sites on the seaward reefs of Diego Garcia during 2012. ...
... Chagos is situated in a region characterized by a monsoon climate (Sheppard et al., 2012). The northeast monsoon in austral summer is the wet season, and it lasts from October to February (Pfeiffer et al., 2004). ...
Article
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The dominant modes of climate variability on interannual timescales in the tropical Indian Ocean are the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole. El Niño events have occurred more frequently during recent decades, and it has been suggested that an asymmetric ENSO teleconnection (warming during El Niño events is stronger than cooling during La Niña events) caused the pronounced warming of the western Indian Ocean. In this study, we test this hypothesis using coral Sr∕Ca records from the central Indian Ocean (Chagos Archipelago) to reconstruct past sea surface temperatures (SSTs) in time windows from the mid-Little Ice Age (1675–1716) to the present. Three sub-fossil massive Porites corals were dated to the 17–18th century (one coral) and the 19–20th century (two corals). Their records were compared with a published modern coral Sr∕Ca record from the same site. All corals were subsampled at a monthly resolution for Sr∕Ca measurements, which were measured using a simultaneous inductively coupled plasma optical emission spectrometer (ICP-OES). Wavelet coherence analysis shows that interannual variability in the four coral records is driven by ENSO, suggesting that the ENSO–SST teleconnection in the central Indian Ocean has been stationary since the 17th century. To determine the symmetry of El Niño and La Niña events, we compiled composite records of positive and negative ENSO-driven SST anomaly events. We find similar magnitudes of warm and cold anomalies, indicating a symmetric ENSO response in the tropical Indian Ocean. This suggests that ENSO is not the main driver of central Indian Ocean warming.
... This study was conducted in the remote northern atolls of the Chagos Archipelago, Indian Ocean. Due to its status as a large (550,000 km 2 ) marine protected area and its relative isolation, there is no fishing allowed or other direct human influences in the study atolls [27][28][29] . The Chagos Archipelago is also home to eighteen species of breeding seabirds, many of which are present in globally-significant numbers, leading to the designation of several Important Bird and Biodiversity Areas (IBAs) within the archipelago 30 . ...
Article
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By improving resource quality, cross-ecosystem nutrient subsidies may boost demographic rates of consumers in recipient ecosystems, which in turn can affect population and community dynamics. However, empirical studies on how nutrient subsidies simultaneously affect multiple demographic rates are lacking, in part because humans have disrupted the majority of these natural flows. Here, we compare the demographics of a sex-changing parrotfish (Chlorurus sordidus) between reefs where cross-ecosystem nutrients provided by seabirds are available versus nearby reefs where invasive, predatory rats have removed seabird populations. For this functionally important species, we found evidence for a trade-off between investing in growth and fecundity, with parrotfish around rat-free islands with many seabirds exhibiting 35% faster growth, but 21% lower size-based fecundity, than those around rat-infested islands with few seabirds. Although there were no concurrent differences in population-level density or biomass, overall mean body size was 16% larger around rat-free islands. Because the functional significance of parrotfish as grazers and bioeroders increases non-linearly with size, the increased growth rates and body sizes around rat-free islands likely contributes to higher ecosystem function on coral reefs that receive natural nutrient subsidies. More broadly, these results demonstrate additional benefits, and potential trade-offs, of restoring natural nutrient pathways for recipient ecosystems.
... Both process-level analysis and observed macroscale variations suggest that transfer efficiency increased due to fishing exploitation in the last half of the 20th century and will decline with increasing temperatures due to climate change [79]. Globally, fishing exploitation has tended to target large and long-living species leading to declines in abundance compared to smaller species with faster life histories, affecting transfer efficiency [98][99][100][101]. These fishing-induced changes in species assemblages may have contributed to the past observed increase in transfer efficiency [79]. ...
Article
Transfer efficiency is the proportion of energy passed between nodes in food webs. It is an emergent, unitless property that is difficult to measure, and responds dynamically to environmental and ecosystem changes. Because the consequences of changes in transfer efficiency compound through ecosystems, slight variations can have large effects on food availability for top predators. Here, we review the processes controlling transfer efficiency, approaches to estimate it, and known variations across ocean biomes. Both process-level analysis and observed macroscale variations suggest that ecosystem-scale transfer efficiency is highly variable, impacted by fishing, and will decline with climate change. It is important that we more fully resolve the processes controlling transfer efficiency in models to effectively anticipate changes in marine ecosystems and fisheries resources.
... The Chagos Archipelago consists of seven atolls and more than 50 small islands. It is regarded as one of the richest marine ecosystems of the world with outstanding ecological values [16]. In particular, the Chagos Conservation Trust (2009) describes the archipelago as, "the most pristine tropical marine environment surviving on the planet" [17] (p. 7). Figure 1 shows the location of the Chagos Archipelago. ...
Article
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Between the late 1960s and the early 1970s, the British government forcibly removed about 15,000 Chagossians from the Chagos Archipelago. Current legislation based on the declaration of the Chagos-Marine Protected Area (MPA) plays a crucial role in preventing the Chagossians from returning to their homeland. In this particular case study, the article aims to analyze discourses related to the establishment of the Chagos-MPA using an environmental justice framework, to consider the implications for international social work practice. Materials from court rulings, official government reports, and academic/journalist publications on the MPA, as well as from seven semi-structured interviews with key informants from three Chagossian communities based in Mauritius, Seychelles, and the United Kingdom were analyzed using ATLAS-ti 8.4 software. The main findings of the deductive critical discourse analysis are discussed concerning substantive, distributive, and procedural environmental justice for the Chagossian community (This term is used for referring different Chagossian communities from Mauritius, Seychelles, and the United Kingdom as a single homogenous group). This article calls for international social work interventions through transnational alliances between international organizations in challenging the socio-political forces that are having deleterious impacts upon the marginalized and disenfranchised populations and their biophysical environment.
... If damaged by mechanical action, such as from dFAD grounding, it may take years for underlying coral or seagrass to recover (Davies et al. 2017). The reefs of the Chagos Archipelago are regionally significant (Sheppard et al. 2012). They support reef fish biomass 6 times greater than elsewhere in region (Graham et al. 2013) and act as a source of biological diversity for overexploited sites farther west (Sheppard et al. 2013). ...
Article
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Mapping and predicting the potential risk of fishing activities to large marine protected areas (MPAs), where management capacity is low, but fish biomass may be globally important, is vital to prioritize enforcement and maximize conservation benefits. Using Lagrangian particle modelling we determine the potential transit of drifting fish aggregating devices (dFADs) entering a large MPA around the Chagos Archipelago in the central Indian Ocean: (i) to quantify the risk of dFADs beaching on the archipelago's reefs and atolls, and (ii) determine the potential for dFADs to pass through the MPA, accumulate biomass and export it outside of the MPA boundary. We find over a third (37.51%) of dFADs would pose a risk (beaching or transiting >14 days), 17.70% pose a moderate risk (beaching or transiting >30 days), while 13.11% pose a high risk (beaching or transiting >40 days). Importantly, modelled dFADs deployed on east and west of the perimeter were more likely to beach and undertake long transiting times (i.e., high risk). The Great Chagos Bank, the largest atoll in the archipelago, was the most likely site to be impacted by dFADs beaching. Overall, understanding the interactions between static MPAs and drifting fishing gears is vital in developing suitable management plans to support enforcement of MPA boundaries and the health and sustainability of their associated biomass. Article impact statement: Left unchecked, drifting fish aggregation devices could reduce the efficacy of static marine protected areas. This article is protected by copyright. All rights reserved
... Located in the Central Indian Ocean, it comprises the islands and atolls of the Chagos Archipelago and since 1973 there has been no resident population, although ∼3,000 individuals support a joint UK and US military base located on the largest island, Diego Garcia (Hays et al., 2020). The MPA is considered of global conservation importance and contains a wealth of biodiversity, including highly vulnerable and endemic marine species (Koldewey et al., 2010;Sheppard et al., 2012). Designated in April 2010, it is a strictly no-take MPA, with no commercial fishing permitted. ...
Article
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Area coverage of large-scale marine protected areas (MPAs) (LSMPAs, > 100,000 km2) is rapidly increasing globally. Their effectiveness largely depends on successful detection and management of non-compliance. However, for LSMPAs this can be difficult due to their large size, often remote locations and a lack of understanding of the social drivers of non-compliance. Taking a case-study approach, we review current knowledge of illegal fishing within the British Indian Ocean Territory (BIOT) LSMPA. Data stemming from enforcement reports (2010–20), and from fieldwork in fishing communities (2018–19) were combined to explore and characterise drivers of non-compliance. Enforcement data included vessel investigation reports (n = 188), transcripts of arrests (20) and catch seizures (58). Fieldwork data included fisher interviews (95) and focus groups (12), conducted in two communities in Sri Lanka previously associated with non-compliance in BIOT LSMPA. From 2010 to 2020, there were 126 vessels suspected of non-compliance, 76% of which were Sri Lankan. The majority of non-compliant vessels targeted sharks (97%), catching an estimated 14,340 individuals during the study period. Sri Lankan vessels were primarily registered to one district (77%) and 85% operated from just two ports within the fieldwork sites. Social Network Analysis (SNA) showed that 66% of non-compliant vessels were linked by social ties, including sharing crew members, compared with only 34% of compliant vessels. Thematic analysis of qualitative data suggested that perceptions of higher populations of sharks and social ties between vessels may both be important drivers. We discuss our findings within a global context to identify potential solutions for LSMPA management.
... The Chagos Archipelago is situated 500 km south of the Maldives and is a group of 55 islands, submerged banks (Sheppard et al., 2012), and 73 seamounts (Yesson et al., 2020). Extending out to the full EEZ, the BIOT MPA covers 640,000 km 2 of ocean, with the vast majority being deep oceanic water with maximum depths of over 5,000 m. ...
Article
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Silky sharks (Carcharhinus falciformis) represent a major component of global shark catch, both directly and as bycatch, and populations are declining as a result. An improved understanding of their movement ecology is needed to support conservation efforts. We deployed satellite and acoustic tags (2013-2018) and analyzed historical fisheries records (1997-2009), to investigate the spatial ecology of silky sharks in the central Indian Ocean and a large Marine Protected Area (MPA; 640,000 km 2) around the Chagos Archipelago. We observed high fidelity to the MPA, and a sustained diurnal association with a seamount complex, with individuals moving off at night and returning at sunrise. Yet, we also observed large-scale divergent movements in two satellite tagged individuals and documented the furthest recorded displacement distance for a satellite tagged silky shark to date, with one individual moving from the MPA to the Kenyan coast-a displacement distance of 3,549 km (track distance ∼4,782 km). Silky sharks undertook diel vertical migrations and oscillatory diving behavior, spending > 99% of their time in the top 100 m, and diving to depths of greater than 300 m, overlapping directly with typical deployments of purse seine and longline sets in the Indian Ocean. One individual was recorded to a depth of 1,112 m, the deepest recorded silky shark dive to date. Individuals spent 96% of their time at liberty within water temperatures between 24 and 30 • C. Historic fisheries data revealed that silky sharks were a major component of the shark community around the archipelago, representing 13.69% of all sharks caught by longlines before the fishery closed in 2010. Over half (55.88%) of all individuals caught by longlines and purse seiners were juveniles. The large proportion of juveniles, coupled with the high site fidelity and residence observed in some individuals, suggests that the MPA could provide Frontiers in Marine Science | www.frontiersin.org 1 December 2020 | Volume 7 | Article 596619 Curnick et al. Spatial Ecology of Silky Sharks considerable conservation benefits for silky sharks, particularly during early life-history stages. However, their high mobility potential necessitates that large MPAs need to be considered in conjunction with fisheries regulations and conservation measures in adjacent EEZs and in areas beyond national jurisdiction.
... nddate.com. The MPA experiences distinct Indian Ocean wet and dry seasons with wet season running from October to March and dry season from April to September (Sheppard et al., 2012). Seasonal variability is often greater than monthly variability in tropical ocean systems (Huang & Kinter III, 2002;Servain et al., 1985), and therefore, we deemed season a more biologically relevant driver of shark movement. ...
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• A wide array of technologies are available for gaining insight into the movement of wild aquatic animals. Although acoustic telemetry can lack the fine‐scale spatial resolution of some satellite tracking technologies, the substantially longer battery life can yield important long‐term data on individual behavior and movement for low per‐unit cost. Typically, however, receiver arrays are designed to maximize spatial coverage at the cost of positional accuracy leading to potentially longer detection gaps as individuals move out of range between monitored locations. This is particularly true when these technologies are deployed to monitor species in hard‐to‐access locations. • Here, we develop a novel approach to analyzing acoustic telemetry data, using the timing and duration of gaps between animal detections to infer different behaviors. Using the durations between detections at the same and different receiver locations (i.e., detection gaps), we classify behaviors into “restricted” or potential wider “out‐of‐range” movements synonymous with longer distance dispersal. We apply this method to investigate spatial and temporal segregation of inferred movement patterns in two sympatric species of reef shark within a large, remote, marine protected area (MPA). Response variables were generated using network analysis, and drivers of these movements were identified using generalized linear mixed models and multimodel inference. • Species, diel period, and season were significant predictors of “out‐of‐range” movements. Silvertip sharks were overall more likely to undertake “out‐of‐range” movements, compared with gray reef sharks, indicating spatial segregation, and corroborating previous stable isotope work between these two species. High individual variability in “out‐of‐range” movements in both species was also identified. • We present a novel gap analysis of telemetry data to help infer differential movement and space use patterns where acoustic coverage is imperfect and other tracking methods are impractical at scale. In remote locations, inference may be the best available tool and this approach shows that acoustic telemetry gap analysis can be used for comparative studies in fish ecology, or combined with other research techniques to better understand functional mechanisms driving behavior.
... Herbivorous fishes have a significant role in reducing algal standing stock in the coral ecosystem (McManus & Polsenberg, 2004), and the population of herbivorous fishes consequence of influence in algal cover after the loss of corals (Rongo & van Woesik, 2013;Sheppard, Ateweberhan, Bowen, et al., 2012;Wilson, Graham, Pratchett, et al., 2006). There is an interesting hypothesis in interaction from coral, algae, and herbivorous fishes. ...
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The herbivorous fishes have been considered as a critical functional group and have capability maintaining coral reef resilience and avoiding coral-algal phase-shifts. The present condition shown, almost in tropical reef location, alga has dominated coral, even in the small outer island. The requirement to conduct comprehensive basic research in studying the patterns and composition of herbivorous fish, especially on the small outer islands. Twelve coral reef sites in eastern Indonesia (Liki Islands) and western Indonesia (Natuna Island) used as a research location for comparing the structure patterns of herbivorous fish communities (diversity, density, and body size) using the Underwater Visual Census (UVC) method. There was different pattern of herbivorous fishes families in Liki Island and Natuna Islands, where Acanthuridae is dominant in eastern Indonesia (Liki Islands), including Ctenochaetus striatus (41,00 ± 11,72 se) individuals/350m2, A. maculiceps (23,33 ± 13,61 se) individuals/350m2, Naso hexacanthus (18,67 ± 6,34 se) individuals/350m2 while Scaridae is dominant in western Indonesia (Natuna island), including Scarus rivulatus (31,67 ± 10,61 se) individuals/350m2, Chlorurus sordidus (30,00 ± 8,52 se) individuals/350m2 and Scarus quoyi (19,00 ± 9,73 se) individuals/350m2. Based on herbivore fishes composition Liki Island has a higher density and biomass compared to Natuna Island.Keywords: herbivore, fish, coral, small outer island, Indonesia
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Climate change is altering the biogeochemical conditions of the ocean, leading to the emergence of novel environmental conditions that may drastically affect the performance of very large marine protected areas (VLMPAs) (area > 100,000 km²). Given the prominent role that VLMPAs play in ocean conservation, determining when and where novel conditions will emerge within VLMPAs is vital for ensuring a healthy ocean in the future. Here, using a non-parametric approach to detect novelty, we show that 60%–87% of the ocean and 76%–97% of VLMPAs are expected to contain novel conditions across multiple biogeochemical variables by 2100, with novel conditions in pH emerging by 2030. With most VLMPAs expected to contain environmental conditions unlike those currently within their boundaries, and given the likelihood of any of these climate futures unfolding, present-day management will need to consider alterations to current and future VLMPA design and use.
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We present the first mitochondrial genomes from Chagos Archipelago, Indian Ocean, of three putative species of reef forming Acropora (Acropora aff. tenuis, Acropora aff. cytherea and Acropora aff. orbicularis). The circular genome consists respectively of 18,334 bp, 18,353 bp and 18,584 bp. All mitochondrial genomes recovered comprise 13 protein-coding genes, two transfer RNA genes and two ribosomal RNA genes, with an overall GC content ranging from 37.9% to 38.0%. These new genomic data contribute to our increased understanding of genus Acropora and its species boundaries, ultimately aiding species monitoring and conservation efforts.
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Here we present coral Sr/Ca data of biweekly resolution from three modern coral cores drilled from living Porites corals from two different reef settings at Chagos (tropical Indian Ocean). Chagos lies at the eastern margin of the Seychelles-Chagos thermocline ridge and features open ocean upwelling. In situ temperatures have been recorded by temperature loggers since 2006. High-resolution satellite temperatures closely track the logger data. Two cores were collected from a patch reef in the lagoon of Peros Banhos, a site characterized by high mean temperatures and low-temperature variability. An open ocean core was collected at the outer reef slope of Diego Garcia, which experiences larger temperature fluctuations related to open ocean upwelling. The open ocean core shows clear seasonal cycles in Sr/Ca that closely track the satellite temperatures. The Sr/Ca records from the two lagoon corals show good reproducibility. Between 2007 and 2010, Sr/Ca tracks satellite temperatures. However, between 2003 and 2006 the Sr/Ca curves are almost flat and annual coral growth rates are low. During these years, warm sea surface temperatures and coral bleaching have been observed at Chagos. It is likely that the observed reduction in coral growth rates is a response to prolonged warming events, adding to the growing evidence that seemingly healthy and surviving corals are affected by thermal stress. Further, the high correlation between the Sr/Ca records of the two lagoon cores suggests that this effect is not limited to single coral colonies but may affect the entire reef setting.
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We conducted soil surveys on two islands in the Peros Banhos and Salomon atolls of the northern Chagos Archipelago, Indian Ocean. We found muted but consistent topographic and soil zonation from the ocean shores to the lagoons. The main elements of the zonation are: berms of coral boulders and rubble along the heads of the ocean-side beaches; rubble-strewn soils inland of the berm; and pale sands with shallower topsoils and few coral clasts on slight rises and declivities over the rest of the islands. The ocean-side rubbly soils have interstitial coarse sand and are the most fertile on the islands, with dense tangled stands of unmanaged coconuts, profuse litter, and deep humic topsoils. Topsoils are shallower and less humic in the pale sands inland. Sand size decreases from ocean to lagoon, but increases with depth in most profiles. Water tables are often <2 m deep, and many soils have faint pale brownish mottling in the lower subsoils. There is a low tabular outcrop of bare Holocene coral sandstone on one of the islands. It is incised by shallow grikes that are partly infilled with silty muck, as are some small depressions in the central parts of both islands. The pedogenic environment appears to be dynamic, with storm surges depositing fresh sand, eroding coastlines, and infilling inter-island channels. Some soils have buried humic topsoils, stone layers, sand size inversions, and slight changes in sand colour, which are attributed to polycyclic pedogenesis. Some topsoils have elevated levels of total Zn, which is thought to be derived from long distance volcanic ash. Our data indicate that the soils are of low nutrient fertility. Total N and available P do not attain the strikingly eutric levels found in some atoll soils. The low fertility is attributed to the predation of seabirds by inadvertently introduced black rats. This precludes soil enrichment with marine-derived nutrients by guano deposition.
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Biological invasions pose a threat to nearly every ecosystem worldwide.1,2 Although eradication programs can successfully eliminate invasive species and enhance native biodiversity, especially on islands,3 the effects of eradication on cross-ecosystem processes are unknown. On islands where rats were never introduced, seabirds transfer nutrients from pelagic to terrestrial and nearshore marine habitats, which in turn enhance the productivity, biomass, and functioning of recipient ecosystems.4-6 Here, we test whether rat eradication restores seabird populations, their nutrient subsidies, and some of their associated benefits for ecosystem function to tropical islands and adjacent coral reefs. By comparing islands with different rat invasion histories, we found a clear hierarchy whereby seabird biomass, seabird-driven nitrogen inputs, and the incorporation of seabird-derived nutrients into terrestrial and marine food chains were highest on islands where rats were never introduced, intermediate on islands where rats were eradicated 4-16 years earlier, and lowest on islands with invasive rats still present. Seabird-derived nutrients diminished from land to sea and with increasing distance to rat-eradicated islands, but extended at least 300 m from shore. Although rat eradication enhanced seabird-derived nutrients in soil, leaves, marine algae, and herbivorous reef fish, reef fish growth was similar around rat-eradicated and rat-infested islands. Given that the loss of nutrient subsidies is of global concern,7 that removal of invasive species restores previously lost nutrient pathways over relatively short timescales is promising. However, the full return of cross-ecosystem nutrient subsidies and all of their associated demographic benefits may take multiple decades.
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Seabirds are one of the most threatened avian taxa and are hence a high conservation priority. Managing seabirds is challenging, requiring conservation actions at sea (e.g. Marine Protected Areas - MPAs) and on land (e.g. protection of breeding sites). Important Bird and Biodiversity Areas (IBAs) have been successfully used to identify sites of global importance for the conservation of bird populations, including breeding seabirds. The challenge of identifying suitable IBAs for tropical seabirds is exacerbated by high levels of dispersal, aseasonal and asynchronous breeding. The western Indian Ocean supports ~19 million breeding seabirds of 30 species, making it one of the most significant tropical seabird assemblages in the world. Within this is the British Indian Ocean Territory (BIOT), encompassing 55 islands of the Chagos Archipelago, which supports 18 species of breeding seabird and one of the world’s largest no-take MPAs. Between January and March in 1975 and 1996, eight and 45 islands respectively were surveyed for seabirds and the data used to designate 10 islands as IBAs. A further two were proposed following an expedition to 26 islands in February/March 2006. Due to the historic and restricted temporal and spatial nature of these surveys, the current IBA recommendations may not accurately represent the archipelago’s present seabird status and distribution. To update estimates of the BIOT breeding seabird assemblage and reassess the current IBA recommendations, we used seabird census data collected in every month except September from every island, gathered during 2008–2018. The maximum number of breeding seabirds for a nominal year was 281,596 pairs of 18 species, with three species making up 96%: Sooty Tern Onychoprion fuscatus - 70%, Lesser Noddy Anous tenuirostris - 18% and Red-footed Booby Sula sula - 8%. Phenology was a complex species-specific mix of synchronous and asynchronous breeding, as well as seasonal and aseasonal breeding. Nine of the 10 designated IBAs and the two proposed IBAs qualified for IBA status based on breeding seabirds. However, not every IBA qualified each year because Sooty Terns periodically abandoned breeding islands and Tropical Shearwater Puffinus bailloni breeding numbers dropped below IBA qualifying criteria in some years. Further, one survey per year does not always capture the periodic breeding of some tropical seabirds. We propose therefore, that IBAs in BIOT are better designated at the island cluster level rather than by specific island and require two surveys six months apart per year. This work highlights the merits of long-term, systematic, versus incidental surveys for breeding tropical seabirds and the subsequent associated designation of IBAs.
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Studying scleractinian coral bleaching and recovery dynamics in remote, isolated reef systems offers an opportunity to examine impacts of global reef stressors in the absence of local human threats. Reefs in the Chagos Archipelago, central Indian Ocean, suffered severe bleaching and mortality in 2015 following a 7.5 maximum degree heating weeks (DHWs) thermal anomaly, causing a 60% coral cover decrease from 30% cover in 2012 to 12% in April 2016. Mortality was taxon specific, with Porites becoming the dominant coral genus post-bleaching because of an 86% decline in Acropora from 14 to 2% cover. Spatial heterogeneity in Acropora mortality across the Archipelago was significantly negatively correlated with variation in DHWs and with chlorophyll-a concentrations. In 2016, a 17.6 maximum DHWs thermal anomaly caused further damage, with 68% of remaining corals bleaching in May 2016, and coral cover further declining by 29% at Peros Banhos Atoll (northern Chagos Archipelago) from 14% in March 2016 to 10% in April 2017. We therefore document back-to-back coral bleaching and mortality events for two successive years in the remote central Indian Ocean. Our results indicate lower coral mortality in 2016 than 2015 despite a more severe thermal anomaly event in 2016. This could be caused by increased thermal resistance and resilience within corals surviving the 2015 thermal anomaly; however, high bleaching prevalence in 2016 suggests there remained a high sensitivity to bleaching. Similar coral mortality and community change were seen in the Chagos Archipelago following the 1998 global bleaching event, from which recovery took 10 yr. This relatively rapid recovery suggests high reef resiliency and indicates that the Archipelago’s lack of local disturbances will increase the probability that the reefs will again recover over time. However, as the return time between thermal anomaly events becomes shorter, this ability to recover will become increasingly compromised.
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Within atolls, deep water channels exert significant control over local hydrodynamic conditions; which are important drivers of planktonic distributions. To examine planktonic responses to oceanography, this study tested the effect of proximity and exposure to deep oceanic flushing through these channels on water properties and planktonic assemblages across four atolls (Diego Garcia, Salomon, Egmont, and Peros Banhos) in the British Indian Ocean Territory Marine Reserve. As this is the largest, most isolated and sparsely inhabited atoll complex in the world, it provides the perfect experimental conditions to test the effect of oceanic flushing without confounding factors related to anthropogenic development. Results are discussed in the context of ecosystem functioning. A total of 30 planktonic taxa and 19,539 individuals were identified and counted. Abundance was significantly different between atolls and significantly greater within inner regions in all atolls except southeast Egmont. Planktonic assemblage composition significantly differed between atolls and between inner and outer stations; exhibiting higher similarity between outer stations. Within outer stations of Diego Garcia, Peros Banhos, and Egmont, evidence suggesting oceanic flushing of cold, saline, and dense water was observed, however a longer time series is required to conclusively demonstrate tidal forcing of this water through deep water channels. Planktonic variability between inner and outer atoll regions demonstrates that broad comparisons between oceanic and lagoon regions fail to capture the complex spatial dynamics and hydrodynamic interactions within atolls. Better comprehension of these distributional patterns is imperative to monitor ecosystem health and functioning, particularly due to increasing global anthropogenic pressures related to climate change. The extensive coral bleaching described in this paper highlights this concern.
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The last decade has seen a noticeable advance in ocean protection through the creation of several LSMPAs which are largely driven by Aichi Target 11 under CBD. This paper uses the "Ocean grabbing framework" to assess the process preceding the announcement of a LSMPA in Rapa Nui, its rejection, the reformulation of the process and the ultimately successful establishment of a Multiple Uses Marine Protected Area (MUMPA). The assessment focused on: a) the quality of governance, b) the effects on livelihoods and human security, and 3) the potentially interlinked social and ecological impacts. The rejection of the initial LSMPA process was associated with lack of transparency, inadequate participatory processes, and lack of accountable decisionmaking all of which could have had adverse social and ecological outcomes and turned the LSMPA into an "ocean grab". Factors that contributed were associated to inappropriate use of financing, political lobbying and pressure exerted by a NGO that tried to deploy its agenda disconnected from local indigenous interests. In a major turning point stemming from the vigorous local rejection of the initial LSMPA, a bottomup process led by a local institution (CODEIPA) and other Rapanui organizations, coordinated with the Chilean Government, resulted in an unprecedented participatory process ending in the creation of the largest MPA in the Americas, that will be comanaged by Rapanui people and the Chilean Government. It is hoped that the results of this analysis can contribute to the development of good practices in marine conservation worldwide, maximizing marine conservation outcomes and avoiding undesirable social and ecological impacts.
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Bourjon P., Fricke R. 2019. First record of the lattice soldierfish, Myripristis violacea (Actinopterygii: Holocentriformes: Holocentridae), from Reunion Island (south-western Indian Ocean). Acta Ichthyol. Piscat. 49 (4): 415-420. Abstract. The lattice soldierfish, Myripristis violacea Bleeker, 1851, is recorded for the first time from Reunion Island. An aggregation of 12 individuals was observed and photographed on 12 January 2019 and later on the L'Hermitage reef, located on the west coast of the island. Examination of high-resolution photographs of the largest of these individuals shows that its external morphological characteristics agree well with those reported in the description of the species provided by the last revision of the genus. Studies on regional connectivity make it likely that the Reunion Island population of M. violacea originates from the northern Seychelles Island or Chagos Archipelago via stepping-stone populations. Our observations extend the known distribution of the species to the southernmost island of the Mascarene Archipelago, and extend its known depth range.
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Chagos avifauna in relation to the Indian sub-continent
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Over the past few decades, partitioning of the surface ocean into ecologically-meaningful spatial domains has been approached using a range of data types, with the aim of improving our understanding of open ocean processes, supporting marine management decisions and constraining coupled ocean-biogeochemical models. The simplest partitioning method, which could provide low-latency information for managers at low cost, remains a purely optical classification based on ocean colour remote sensing. The question is whether such a simple approach has value. Here, the efficacy of optical classifications in constraining physical variables that modulate the epipelagic environment is tested for the tropical Indian Ocean, with a focus on the Chagos marine protected area (MPA). Using remote sensing data, it was found that optical classes corresponded to distinctive ranges of wind speed, wind stress curl, sea surface temperature, sea surface slope, sea surface height anomaly and geostrophic currents (Kruskal-Wallis and post-hoc Tukey honestly significantly different tests, α = 0.01). Between-class differences were significant for a set of sub-domains that resolved zonal and meridional gradients across the MPA and Seychelles-Chagos Thermocline Ridge, whereas between-domain differences were only significant for the north-south gradient (PERMANOVA, α = 0.01). A preliminary test of between-class differences in surface CO2 concentrations from the Orbiting Carbon Observatory-2 demonstrated a small decrease in mean pCO2 with increasing chlorophyll (chl), from 418 to 398 ppm. Simple optical class maps therefore provide an overview of growth conditions, the spatial distribution of resources - from which habitat fragmentation metrics can be calculated, and carbon sequestration potential. Within the 17 year study period, biotic variables were found to have decreased at up to 0.025%a-1 for all optical classes, which is slower than reported elsewhere (Mann-Kendall-Sen regression, α = 0.01). Within the MPA, positive Indian Ocean Dipole conditions and negative Southern Oscillation Indices were weakly associated with decreasing chl, fluorescence line height (FLH), eddy kinetic energy, easterly wind stress and wind stress curl, and with increasing FLH/chl, sea surface temperature, SSH gradients and northerly wind stress, consistent with reduced surface mixing and increased stratification. The optical partitioning scheme described here can be applied in Google Earth Engine to support management decisions at daily or monthly scales, and potential applications are discussed.
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Large, remote marine protected areas (MPAs) containing both reef and pelagic habitats, have been shown to offer considerable refuge to populations of reef‐associated sharks. Many large MPAs are, however, impacted by illegal fishing activity conducted by unlicensed vessels. While enforcement of these reserves is often expensive, it would likely benefit from the integration of ecological data on the mobile animals they are designed to protect. Consequently, shark populations in some protected areas continue to decline, as they remain a prime target for illegal fishers. To understand shark movements and their vulnerability to illegal fishing, three years of acoustic tracking data, from 101 reef‐associated sharks, were analysed as movement networks to explore the predictability of movement patterns and identify key movement corridors within the British Indian Ocean Territory (BIOT) MPA. We examined how space use and connectivity overlap with spatially‐explicit risk of illegal fishing, through data obtained from the management consultancy enforcing the MPA. Using individual‐based models, the movement networks of two sympatric shark species were efficiently predicted with distance‐decay functions (>95% movements accurately predicted). Model outliers were used to highlight the locations with unexpectedly high movement rates where MPA enforcement patrols might most efficiently mitigate predator removal. Activity space estimates and network metrics illustrate that silvertip sharks were more dynamic, less resident and link larger components of the MPA than grey reef sharks. However, we show that this behaviour potentially enhances their exposure to illegal fishing activity. Synthesis and applications. Marine protected area (MPA) enforcement strategies are often limited by resources. The British Indian Ocean Territory MPA, one of the world’s largest ‘no take’ MPAs, has a single patrol vessel to enforce 640,000 km2 of open ocean, atoll and reef ecosystems. We argue that to optimise the patrol vessel search strategy and thus enhance their protective capacity, ecological data on the space use and movements of desirable species, such as large‐bodied reef predators, must be incorporated into management plans. Here, we use electronic tracking data to evaluate how shark movement dynamics influence species mortality trajectories in exploited reef ecosystems. In doing so we discuss how network analyses of such data might be applied for protected area enforcement.
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The status of the Chagos Island remains a subject of struggle in international relations pitting the United Kingdom and, by extension, the U.S. against the indigenous people of the Chagos who were forcibly displaced and exiled in order to accommodate a U.S. military base involved in evil conflicts in the lands of the Orient. Mauritius joined this struggle on the basis that the islands were separated from Mauritius by the British on the eve of independence in 1968. The Chagosians have for decades insisted on their right to self-determination and their right to return to the land of their ancestors, taking their battles to the streets of London and international courts. In spite of the growing support for their cause around the world and although they have scored some victories in courts and at the United Nations, their dreams remain deferred as the U.K. and the U.S. refuse to act justly and fairly. This is a classic case of neocolonial continuities that haunt post-colonial Africa, rendering independence meaningless for injustice anywhere in Africa is injustice against the whole of Africa. This paper suggests that the use of a decolonial lens of analysis infused with African anti-colonial perspectives enables us to understand the fundamental problems facing the Chagosians and to think of more permanent solutions to this quagmire.
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The pelagic ecosystem is the ocean's largest by volume and of major importance for food provision and carbon cycling. The high fish species diversity common in the tropics presents a major challenge for biomass estimation using fisheries acoustics, the traditional approach for evaluating mid-water bio-mass. Converting echo intensities to biomass density requires information on species identity and size, which are typically obtained by lethal means, and thus unsuitable in the portion of the ocean that is 'no take'. To improve conservation and ecosystem based management, we present a procedure for determining fish biomass density, using data on species identity, relative abundance, and lengths obtained from stereo baited remote underwater video systems (stereo-BRUVS) to inform the scaling of echosounder survey data (at 38 kHz). We apply the procedure in the British Indian Ocean Territory marine protected area, using acoustic data from 3025 km of survey transects and 546 BRUVS deployments recording relative abundance and size of 12,335 individual fish. Using a Generalised Additive Model of biomass density (GAM, adjR 2 = 0.61) we predict, on the basis of oceanographic conditions and bathymetry, that the top 200 m pelagic ecosystem in the Chagos Archipelago, some 118,324 km 2 , held 3.84 (2.66, 5.62, 95% CI), 33.09 (23.41, 47.35) and 4.08 (3.1, 5.44) million tonnes of fish in November 2012, January 2015, and February 2016, respectively. Our non-extractive procedure yields ecologically credible patterns in biomass across multiple temporal (hours and years) and spatial (metres and kilometres) scales, and marks an improvement on the use of echo intensity alone as a biomass proxy. High seasonal and interannual variability has implication for pelagic fish monitoring.
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Globally, climatic and anthropogenic forcings are causing the catastrophic decline of coral reef ecosystems, which sustain a plethora of marine life and support the livelihoods of several millions of people. Lakshadweep- Maldives-Chagos archipelago (LMC) forms one of the largest chains of atoll systems in the world, and due to remoteness from the mainland, its islands boast a unique set of flora and fauna. The coral reefs of these tropical islands are highly vulnerable to stressors such as climate change, overfishing, monsoon runoff, and ocean acidification. To understand and manage these sensitive ecosystems, knowledge about the existing coral cover and distribution patterns are essential. In the present study, habitat modelling of the two corals Acropora muricata (Linnaeus, 1758) and Porites lutea (Milne Edwards & Haime, 1851) were carried out using the Maximum Entropy (MaxEnt) model to predict the probability of occurrence using remotely sensed environmental variables as predictors. The average test AUC values of 0.980 and 0.974, respectively, for A. muricata and P. lutea as estimated by MaxEnt shows that the model performance for both the species is outstanding. The average uncertainty (standard deviation) was about 0.012 and 0.021 respectively. It is found that the bathymetry is the variable having the highest contribution followed by Calcite and Phosphate for the distribution of both the species. The results of this study throw light on the probable occurrence of coral reefs in many of the hitherto unknown areas, especially the submerged banks and seamounts in the region. Much of these areas are less explored and have strategic positional advantages in increasing the ecosystem connectivity of the region. Furthermore, the relationship between coral distribution and the environmental variables as predicted by this study will be valuable in future conservation activities and designing marine protected areas.
Technical Report
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http://www.fao.org/docrep/012/i1116e/i1116e00.htm
Technical Report
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Individually, climate change and invasive species present two of the greatest threats to biodiversity and the provision of valuable ecosystem services. Combined, the complexity of their interactions dramatically increases, and evidence is rapidly growing on how climate change is compounding the already devastating effects of invasive species. Climate change impacts, including warming temperatures and changes in CO2 concentrations, are likely to increase opportunities for invasive alien species because of their adaptability to disturbance and to a broader range of biogeographic conditions. The impacts of those invasive species may be more severe as they increase both in numbers and extent, and as they compete for diminishing resources such as freshwater. Warmer air and water temperatures may also facilitate movement of species along previously inaccessible pathways of spread, both natural and human-made. Targeted at policy-makers, responsible for developing climate mitigation and adaption strategies that address issues like conservation, ecosystem services, agriculture and sustainable livelihoods, the report focuses on the primary linkages between invasive species and climate change, as well as the secondary and tertiary interactions of their corresponding impacts. Building on a review of existing scientific and conservation literature, the report identifies significant gaps and questions about the intersection of these two major drivers of change. Included case studies highlight key relationships and questions related to invasive species, climate change and the role of ecosystem-based adaptation. Finally, a series of recommendations are intended to provide guidance on the best ways to integrate invasive species prevention and management into the consideration of climate change responses across a range of sectors.
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The typical tidal range in the west and north-west areas of the Northern Territory, Australia, is 8 m. Four sheltered marinas with double lock gates have been developed to date from the Darwin Harbour estuary, or dug from the shoreline, to provide regulated environments with no tidal range. These sheltered marinas are novel environments and provide habitat islands for colonisation by invasive alien marine species. In March 1999, a fouling mussel, Mytilopsis sp., closely related to the freshwater zebra mussel, Dreissena polymorpha, was discovered in one of the marinas at densities up to 23,650/m 2 . It had reached those densities in less than six months. We describe the colonisation of this and other marinas by the mussel, and the approaches taken to quarantine and eventually eradicate it. Lastly, we discuss the features that may have led to the invasion and present actions that are being taken to reduce the risk of future invasions.
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The 1996 Chagos Expedition provided the first opportunity to study the archipelago's lichen flora. Seventeen of the 55 islands were ecologically investigated, some in more detail than others, and lists and representative collections of lichens have been assembled for many of them. In all, 67 taxa have been recorded, 52 to specific level. Although the islands have a low biodiversity for cryptogamic plants, as would be expected in terms of their relatively young age, remoteness and small terrestrial surface areas, those taxa that are present are often found in abundance and play significant ecological roles. There is a good correlation between total lichen biodiversity and island size, despite the fact that Cocos nucifera is such an important substratum for cryptogamic plants and its presence on all islands studied provides a consistently high associated species count. Comparisons of lichen floras for ten island and coastal tropical areas show good correlations (based on the Sörensen Coefficient) within the Indian Ocean as would be expected, but poorer correlations exist within and between Pacific Ocean and neotropical floras. Ranked correlations between Chagos and other floras are in the sequence Maldives > Laing Island > Aldabra > Tuamotu > Pitcairn > N.Mariana & Belize > Guadeloupe > Cook. When coefficients are calculated using only the Physciaceae, different correlations and sequences are derived, but the affinities of the Indian Ocean islands remain strong. However, although the lichen flora of Chagos is characteristic for an Indian Ocean, it is dominated by pantropical species.
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The goldrim surgeonfish ( also known as the whitecheek surgeonfish in the aquarium trade), Acanthurus nigricans ( Linnaeus), is a common and widespread member of tropical reef fish communities throughout the Pacific Ocean. It has been reported at low densities at Cocos ( Keeling) and Christmas Islands in the eastern Indian Ocean. Named nigricans for its characteristically dark body color, the species usually inhabits shallow depths on the outer reef crest just below the surge zone, but has been observed as deep as 67 m ( Chave and Mundy, 1994). The species feeds on filamentous algae ( Randall, 2001). In this paper I report the first occurrence of Acanthurus nigricans in the central Indian Ocean ( Chagos Archipelago) and provide information on its biogeography and hybridization with A. leucosternon Bennett.
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Seamounts and knolls are ‘undersea mountains’, the former rising more than 1000m from the seafloor. These features provide important habitats for aquatic predators, demersal deep-sea fish and benthic invertebrates. However most seamounts have not been surveyed and their numbers and locations are not well known. Previous efforts to locate and quantify seamounts have used relatively coarse bathymetry grids. Here we use global bathymetric data at 30 arc-sec resolution to identify seamounts and knolls. We identify 33,452 seamounts and 138,412 knolls, representing the largest global set of identified seamounts and knolls to date. We compare estimated seamount numbers, locations, and depths with validation sets of seamount data from New Zealand and Azores. This comparison indicates the method we apply finds 94% of seamounts, but may overestimate seamount numbers along ridges and in areas where faulting and seafloor spreading creates highly complex topography. The seamounts and knolls identified herein are significantly geographically biased towards areas surveyed with ship-based soundings. As only 6.5% of the ocean floor has been surveyed with soundings it is likely that new seamounts will be uncovered as surveying improves. Seamount habitats constitute approximately 4.7% of the ocean floor, whilst knolls cover 16.3%. Regional distribution of these features is examined, and we find a disproportionate number of productive knolls, with a summit depth of
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Global marine zoogeography and evolution.