Content uploaded by Adrian C Stier
Author content
All content in this area was uploaded by Adrian C Stier on Mar 25, 2014
Content may be subject to copyright.
A preview of the PDF is not available
Predators alter community organization of coral reef cryptofauna and reduce abundance of coral mutualists
Abstract and Figures
Coral reefs are the most diverse marine systems in the world, yet our understanding of the processes that maintain such extraordinary diversity remains limited and taxonomically biased toward the most conspicuous species. Cryptofauna that live deeply embedded within the interstitial spaces of coral reefs make up the majority of reef diversity, and many of these species provide important protective services to their coral hosts. However, we know very little about the processes governing the diversity and composition of these less conspicuous but functionally important species. Here, we experimentally quantify the role of predation in driving the community organization of small fishes and decapods that live embedded within Pocillopora eydouxi, a structurally complex, reef-building coral found widely across the Indo-Pacific. We use surveys to describe the natural distribution of predators, and then, factorially manipulate two focal predator species to quantify the independent and combined effects of predator density and identity on P. eydouxi-dwelling cryptofauna. Predators reduced abundance (34 %), species richness (20 %), and modified species composition. Rarefaction revealed that observed reductions in species richness were primarily driven by changes in abundance. Additionally, the two predator species uniquely affected the beta diversity and composition of the prey assemblage. Predators reduced the abundance and modified the composition of a number of mutualist fishes and decapods, whose benefit to the coral is known to be both diversity- and density-dependent. We predict that the density and identity of predators present within P. eydouxi may substantially alter coral performance in the face of an increased frequency and intensity of natural and anthropogenic stressors.
Content may be subject to copyright.
... Because most hawkfishes are strictly associated with branched coral (e.g. Pocillopora spp.) and their movement is restricted to the coral branches, these predators live in close proximity to coral-associated invertebrates that comprised their main prey (Stier and Leray 2014). Mesopredators such as hawkfishes that feed upon small cryptic species, may modify the composition and abundance of cryptic fauna and key mutualistic coral species, which can have significant effects on coral reef food webs (Stier and Leray 2014;Leray et al. 2015;Coker et al. 2015). ...
... Pocillopora spp.) and their movement is restricted to the coral branches, these predators live in close proximity to coral-associated invertebrates that comprised their main prey (Stier and Leray 2014). Mesopredators such as hawkfishes that feed upon small cryptic species, may modify the composition and abundance of cryptic fauna and key mutualistic coral species, which can have significant effects on coral reef food webs (Stier and Leray 2014;Leray et al. 2015;Coker et al. 2015). Cryptic invertebrates are known to perform a variety of functions including positive (e.g., promote survival and growth of corals, protecting corals against corallivores) or negative (e.g., parasites of corals, feed upon coral polyps) interactions with corals (Stella et al. 2011;Leray et al. 2015). ...
Hawkfishes are small demersal reef predators. Although their association with the coral substrate has been widely documented for some species, information regarding their feeding habits is limited, especially in the Eastern Tropical Pacific (ETP). We characterized the diet of the coral hawkfish Cirrhitichthys oxycephalus in Isla Gorgona (ETP) by visually analyzing its gut contents and calculating its trophic niche breadth. Crustaceans were the most important (relative importance: 73%) and frequent prey found in 89% of the stomachs analyzed. Among crustaceans , copepods were the most abundant prey, suggesting that C. oxycephalus in Isla Gorgona has a specialized diet. In terms of biomass, decapods represented the highest contribution to the diet. Other prey items included micro-molluscs and fish. This study highlights the strong trophic link between coral-dwelling reef fish and mobile invertebrates that comprise the coral reef cryptic fauna, and therefore, the indirect benefit that live coral cover has for this species.
... Within-rubble competition and predation may have been alleviated allowing small individuals the chance to proliferate. Competition and predation within rubble seem critical in shaping lower trophic level outcomes, as found for coralassociated taxa (Stier & Leray, 2014). Why this would exclusively benefit harpacticoids is unclear unless they are the preferred food of cryptic predators, which may be the case for some cryptobenthic fishes (Brandl et al., 2018. ...
Abstract Patterns of movement of marine species can reflect strategies of reproduction and dispersal, species' interactions, trophodynamics, and susceptibility to change, and thus critically inform how we manage populations and ecosystems. On coral reefs, the density and diversity of metazoan taxa are greatest in dead coral and rubble, which are suggested to fuel food webs from the bottom up. Yet, biomass and secondary productivity in rubble is predominantly available in some of the smallest individuals, limiting how accessible this energy is to higher trophic levels. We address the bioavailability of motile coral reef cryptofauna based on small‐scale patterns of emigration in rubble. We deployed modified RUbble Biodiversity Samplers (RUBS) and emergence traps in a shallow rubble patch at Heron Island, Great Barrier Reef, to detect community‐level differences in the directional influx of motile cryptofauna under five habitat accessibility regimes. The mean density (0.13–4.5 ind cm−3) and biomass (0.14–5.2 mg cm−3) of cryptofauna were high and varied depending on microhabitat accessibility. Emergent zooplankton represented a distinct community (dominated by the Appendicularia and Calanoida) with the lowest density and biomass, indicating constraints on nocturnal resource availability. Mean cryptofauna density and biomass were greatest when interstitial access within rubble was blocked, driven by the rapid proliferation of small harpacticoid copepods from the rubble surface, leading to trophic simplification. Individuals with high biomass (e.g., decapods, gobies, and echinoderms) were greatest when interstitial access within rubble was unrestricted. Treatments with a closed rubble surface did not differ from those completely open, suggesting that top‐down predation does not diminish rubble‐derived resources. Our results show that conspecific cues and species' interactions (e.g., competition and predation) within rubble are most critical in shaping ecological outcomes within the cryptobiome. These findings have implications for prey accessibility through trophic and community size structuring in rubble, which may become increasingly relevant as benthic reef complexity shifts in the Anthropocene.
... Most of the cryptofauna species living on dead coral rubbles have obligate, highly productive and opportunistic characters (Takada et al 2016;van Tienderen & van der Meij 2016). These organisms commonly had a high diversity in the habitats determined by the living and dead corals (Enochs & Manzello 2012;Kramer et al 2014;Malik et al 2018;Plaisance et al 2009;Stier & Leray 2014). ...
Coral reefs are widely known as essential ecosystems that hold various marine organisms, including various crypto-organisms. Cryptofauna, which live among the interstices of coral reefs, significantly escalates the coral reef biodiversity. The complexity of the reef-building corals' niche could shape the shrimp community structure. This research aims to examine the shrimp diversity and to analyze the shrimp communities on different coral growth structures in Tidung Island, Seribu Islands. The dead coral heads were collected using the timed swim method and the cryptofauna was collected by shattering the dead coral heads. Each species of cryptofauna was photographed and identified. The shrimp community structure was calculated using the multivariate statistic. A total of 165 obligate coral-dwelling shrimps specimens of 30 species belonging to seven families were found. During this study, most of the organisms discovered were from the Alpheidae and Hippolytidae families, who contributed to the relative abundance with up to 34.55 and 30.91%, respectively. The multivariate analysis using non-Metric Dimensional Scaling (nMDS) highlighted three clustering habitat locations between the study sites and the coral growth forms, based on the shrimp abundance. Alpheus pasificus predominantly contributed to the community of the arborescent coral type (in the Tidung Besar coastal zone) and to the corymbose coral type (in the Tidung Kecil coastal zone). Local environmental conditions, such as the food resources, predation threat and coral presence (hosting an associate fauna) are presumed to be important factors affecting the coral-dwelling shrimps.
... Coral reefs are hotspots of mutualistic and facilitative interactions [8][9][10][11]. Reef-building corals, for example, foster numerous interactions with obligate coral-dwelling invertebrates (e.g. Trapezia spp. ...
Mutualisms play a critical role in ecological communities; however, the importance and prevalence of mutualistic associations can be modified by external stressors. On coral reefs, elevated sediment deposition can be a major stressor reducing the health of corals and reef resilience. Here, we investigated the influence of severe sedimentation on the mutualistic relationship between small damselfishes (Pomacentrus moluccensis and Dascyllus aruanus) and their coral host (Pocillopora damicornis). In an aquarium experiment, corals were exposed to sedimentation rates of approximately 100 mg cm-2 d-1, with and without fishes present, to test whether: (i) fishes influence the accumulation of sediments on coral hosts, and (ii) fishes moderate partial colony mortality and/or coral tissue condition. Colonies with fishes accumulated much less sediment compared with colonies without fishes, and this effect was strongest for colonies with D. aruanus (fivefold less sediment than controls) as opposed to P. moluccensis (twofold less sediment than controls). Colonies with symbiont fishes also had up to 10-fold less sediment-induced partial mortality, as well as higher chlorophyll and protein concentrations. These results demonstrate that fish mutualisms vary in the strength of their benefits, and indicate that some mutualistic or facilitative interactions might become more important for species health and resilience at high-stress levels.
Multispecies mutualisms are embedded in a network of interactions that include predation, yet the effects of predation on mutualism function have not been well integrated into mutualism theory. Where predators have been considered, the common prediction is that predators reduce mutualist abundance and, as a consequence, decrease service provision. Here, we use a mathematical model of a predatory fish that consumes two competing coral mutualists to show that predators can also have indirect positive effects on hosts when they preferentially consume competitively dominant mutualists that are also lower in quality. In these cases, predation reverses the outcome of competition, allowing the higher quality mutualist to dominate and enhancing host performance. The direction and strength of predator effects depend on asymmetries in mutualist competition, service provision, and predation vulnerability. Our findings suggest that when the strength of predation shifts (e.g., due to exploitative harvest of top predators, introduction of new species, or range shifts in response to climate change), mutualist communities will exhibit dynamic responses with nonmonotonic effects on host service provision.
The local diversity and global richness of coral reef fishes, along with the diversity manifested in their morphology, behaviour and ecology, provides fascinating and diverse opportunities for study. Reflecting the very latest research in a broad and ever-growing field, this comprehensive guide is a must-read for anyone interested in the ecology of fishes on coral reefs. Featuring contributions from leaders in the field, the 36 chapters cover the full spectrum of current research. They are presented in five parts, considering coral reef fishes in the context of ecology; patterns and processes; human intervention and impacts; conservation; and past and current debates. Beautifully illustrated in full-colour, this book is designed to summarise and help build upon current knowledge and to facilitate further research. It is an ideal resource for those new to the field as well as for experienced researchers.
The local diversity and global richness of coral reef fishes, along with the diversity manifested in their morphology, behaviour and ecology, provides fascinating and diverse opportunities for study. Reflecting the very latest research in a broad and ever-growing field, this comprehensive guide is a must-read for anyone interested in the ecology of fishes on coral reefs. Featuring contributions from leaders in the field, the 36 chapters cover the full spectrum of current research. They are presented in five parts, considering coral reef fishes in the context of ecology; patterns and processes; human intervention and impacts; conservation; and past and current debates. Beautifully illustrated in full-colour, this book is designed to summarise and help build upon current knowledge and to facilitate further research. It is an ideal resource for those new to the field as well as for experienced researchers.
The local diversity and global richness of coral reef fishes, along with the diversity manifested in their morphology, behaviour and ecology, provides fascinating and diverse opportunities for study. Reflecting the very latest research in a broad and ever-growing field, this comprehensive guide is a must-read for anyone interested in the ecology of fishes on coral reefs. Featuring contributions from leaders in the field, the 36 chapters cover the full spectrum of current research. They are presented in five parts, considering coral reef fishes in the context of ecology; patterns and processes; human intervention and impacts; conservation; and past and current debates. Beautifully illustrated in full-colour, this book is designed to summarise and help build upon current knowledge and to facilitate further research. It is an ideal resource for those new to the field as well as for experienced researchers.
The need for comprehensive and effective coral restoration projects, as part of a broader conservation management strategy, is accelerating in the face of coral reef ecosystem decline. This study aims to expand the currently limited knowledge base for restoration techniques in the Maldives by testing the performance of mid-water rope nurseries in a lagoon and a reef habitat. We examined whether different coral farming habitats impacted fragment survival, health and growth of two coral genera and how the occurrence of mutualistic fauna, predation and disease influenced coral rearing success. Two nurseries were stocked with a total of 448 Pocillopora verrucosa and 96 Acropora spp. fragments, divided into different groups (four Pocillopora groups: lagoon nursery at 5 m; reef nursery at 5, 10 and 15 m; two Acropora groups: lagoon nursery at 5 m and reef nursery at 5 m). Eight fragment replicates from the same donor colony (Pocillopora genets: N = 14, Acropora genets N = 6) were used in each group and monitored for one year. Our results show that fragment survival was high in both farming habitats (>90%), with P. verrucosa surviving significantly better in the lagoon and Acropora spp. surviving and growing significantly faster in the reef nursery. P. verrucosa growth rates were similar between reef and lagoon habitat. Different rearing depths in the reef nursery had no impact on the survival of P. verrucosa but coral growth decreased considerably with depth, reducing fragments' ecological volume augmentation and growth rates by almost half from 5 to 15 m depth. Further, higher fish predation rates on fragments were recorded on the reef, which did not impact overall nursery performance. Mutualistic fauna, which correlated positively with fragment survival, was more frequently observed in the lagoon nursery. The occurrence of disease was noted in both habitats, even though implications for fragment health were more severe in the lagoon. Overall, our study demonstrates that lagoon and reef nurseries are suitable for rearing large numbers of coral fragments for transplantation. Nevertheless, we recommend considering the specific environmental conditions of the farming habitat, in particular water quality and year-round accessibility, in each case and to adjust the coral farming strategy accordingly. We hope that this novel research encourages the increased application of mid-water rope nurseries for 'coral gardening' to advance coral reef recovery and climate resilience in the Maldives.
The local diversity and global richness of coral reef fishes, along with the diversity manifested in their morphology, behaviour and ecology, provides fascinating and diverse opportunities for study. Reflecting the very latest research in a broad and ever-growing field, this comprehensive guide is a must-read for anyone interested in the ecology of fishes on coral reefs. Featuring contributions from leaders in the field, the 36 chapters cover the full spectrum of current research. They are presented in five parts, considering coral reef fishes in the context of ecology; patterns and processes; human intervention and impacts; conservation; and past and current debates. Beautifully illustrated in full-colour, this book is designed to summarise and help build upon current knowledge and to facilitate further research. It is an ideal resource for those new to the field as well as for experienced researchers.
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coralassociated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their contribution to reef resilience and their conservation needs. © R. N. Gibson, R. J. A. Atkinson, J. D. M. Gordon, I. P. Smith and D. J. Hughes, Editors Taylor & Francis. All rights reserved.
Pocilloporid corals in possession of obligate crustacean symbionts (xanthid crabs and alpheid shrimp) demonstrated a higher rate of survival than corals divested of their crustacean symbionts. The course of coral death in colonies without crustaceans involved polyp restriction, formation of a septic diaphanous film over the affected branches, disintegration of the polypal layer and massive tissue exfoliation within 4 days. Crude mucus production by corals was significantly greater (19%) in colonies with crustaceans than without. Coral skeletal growth (branch elongation) was also greater (21%) in colonies with crustaceans than without, but at a marginally insignificant level. The sheltering and feeding activities of crustacean symbionts produced local damage to host corals (destruction of polyps and coenosarc, and skeletal abrasion), but these sites were usually repaired and caused no apparent lasting effects. Crustacean symbionts apparently increase coral vitality by assisting their host in shedding contaminants, microorganisms, larval stages and other setting organisms. -Author
Various physical and biological factors affecting coral community structure were investigated by direct observation and periodic censusing (supplemented with laboratory observations and experiments) on three coral reefs off the Pacific coast of Panama from 1970 to 1975. The physical environment has a strong control over coral growth at shallow depth; physical factors are also important subtidally (light, sediment transport). However, paralleling the pattern on temperate shores, biological processes (competition, predation, bioturbation, mutualism) assume an increasing influence on community structure in deeper and more diverse reef assemblages. Coral zonation is marked on these biologically simple and small reefs; the following assemblages are recognized: drying reef flat--live coral cover moderate, species diversity low; reef crest and upper reef slope--highest cover, lowest diversity; lower reef slope and reef base--cover moderate to low, diversity highest. Coral populations in the different zones, though spatially close, are affected by unique sets of conditions. Recurrent extreme tidal exposures devastate reef flat corals (Pocillopora mortality = 40%-60%). The mortality rate of pocilloporid corals is higher than for other corals; this has a diversifying effect on the reef flat assemblage. Acanthaster normally feeds in deep reef zones and numerically its major prey are the predominant pocilloporid corals (most often small colonies and broken branches). Electivity indices and prey choice experiments indicate that less abundant, nonbranching corals are preferred over Pocillopora. Large, branching pocilloporid colonies harbor crustacean symbionts (Trapezia and Alpheus) which can repulse Acanthaster and therefore protect this group of corals. Experimental removal of the symbionts results in a shift of prey preference from nonbranching corals towards the branching pocilloporids. Crustacean symbionts were present in all large Pocillopora colonies sampled, but the density of Trapezia in colonies on the reef flat was about twice that in colonies from deep zones where Acanthaster forages. Further, small pocilloporid colonies and fragments contained relatively few (and a high proportion of juvenile) symbionts. The variety of preferred coral prey present along the seaward reef flanks and the relatively low abundance of Pocillopora in this habitat are considered important factors affecting the distribution of Acanthaster. In addition, a continuous live cover of pocilloporid corals, which Acanthaster avoids, can protect reef zones (e.g., the reef flat) or preferred prey species from attack. The selective destruction of nonpocilloporid corals by Acanthaster tends to lower both live coral cover and species diversity (H'). This trend is evident on the Uva Island study reef where a significant decline in coral cover (47%-18%) and H' (1.06-0.58) occurred over a 4-mo period.