Trait-Based Approaches Reveal that Deeper Reef Ecosystems in the Western Indian Ocean are Functionally Distinct

Stefanoudis, Paris V.; Fassbender, Nico; Samimi-Namin, Kaveh; Adam, Pierre-André; Ebrahim, Ameer; Harlay, Jerome; Koester, Anna; Samoilys, Melita; Sims, Helena; Swanborn, D. J. B.; Talma, Sheena; Winter, Sara; Woodall, Lucy C.

doi:10.2139/ssrn.4121008

Cited by 3 publications

(8 citation statements)

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“…An increase in sponge cover and biomass along the depth gradient has been previously described in both the Caribbean Sea and the Pacific Ocean (Lesser & Slattery, 2011;. In addition, two recent studies in Bermuda and Seychelles investigated every benthic taxon encountered along the depth gradient (15-300 m and 9-351 m, respectively), revealing similar benthic taxa distribution with depth compared to the present study (Stefanoudis et al, 2019(Stefanoudis et al, , 2022. Indeed, they observed limited species overlap between the depth bands, driven by differences in benthic assemblages: the great majority of scleractinian corals were observed shallower than 30 m, in both studies; antipatharians were not observed above 60 m in Seychelles and 90 m in Bermuda and octocorals were mainly observed from 60 m in Seychelles and with numerous depth-specialists in Bermuda (Stefanoudis et al, 2019(Stefanoudis et al, , 2022.…”

Section: Discussionsupporting

confidence: 84%

“…This study represents the first extensive survey of mesophotic coral ecosystems along the entire depth gradient in the Chagos Archipelago. Distinct benthic communities were recorded, from 15 to 160 m (Figure 5), similar to those reported for the benthos in the Western Indian Ocean (Stefanoudis et al, 2022). Broadly, the benthic communities surveyed at Egmont Atoll are separated as follows:…”

Section: Discussionsupporting

confidence: 73%

“…Thus, it can be assumed that a comparable area of seabed was surveyed within each transect and depth zone. Substratum categories were selected using similar categories as detailed in Stefanoudis et al (2019Stefanoudis et al ( , 2022: boulders (rocks ≥256 mm), bedrock/hard bottom, coral rubble (64 to 256 mm), coral gravel (2 to 64 mm), sand (0.06252 mm), sediment veneer and epibenthic mat/turf. Live coral and live sponge categories were categorised as bedrock, to avoid double counting, as bedrock was the substratum where corals and sponges were attached to Goode et al (2021).…”

Section: Biological Datamentioning

confidence: 99%

“…While some studies have observed similar scleractinian coral genera throughout the depth gradient displaying less bleaching susceptibility at depth or being less affected by surface disturbances (Pérez-Rosales et al, 2021), there is growing evidence that the DRRH may not hold globally (Godefroid et al, 2022). Indeed, several studies observed distinct communities between shallow and deeper habitats, for both benthic (Hoarau et al, 2021;Lesser et al, 2019;Stefanoudis et al, 2019Stefanoudis et al, , 2022 and pelagic (Rocha et al, 2018;Stefanoudis et al, 2022) organisms. In addition, some of the few species with distributions that span from shallow down to mesophotic depths demonstrated lower reproductivity (Shlesinger et al, 2018), slower growth rates (Groves et al, 2018), or were not genetically connected between depth bands (Bongaerts et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Light and temperature drive the distribution of mesophotic benthic communities in the Central Indian Ocean

Diaz,

Howell,

Robinson

et al. 2023

Diversity and Distributions

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AimResearch on mesophotic coral ecosystems (MCEs) has increased exponentially in recent decades, and the significance of this ecosystem has been recognised both in terms of biodiversity and distribution. However, this research has mostly focussed on corals and is globally sporadic, with the Indian Ocean remaining largely unexplored and overall MCEs under protected. Hence, baseline data on MCE benthic communities is lacking, but nonetheless essential for developing adequate management strategies. Here, we assess the variation in diversity and community structure of MCEs along the depth gradient and among sites in the Indian Ocean and the environmental parameters that are potentially driving these differences.LocationEgmont Atoll, Chagos Archipelago, central Indian Ocean.Time PeriodPresent.Major Taxa StudiedMarine benthic invertebrates, plants.MethodsUsing a remotely operated vehicle, we collected video transects between 15 and 160 m. We analysed the diversity and composition of benthic communities and used DistLM analysis to determine the environmental drivers of the community structure over the depth gradient and between sites.ResultsWe observed distinct benthic communities along the depth gradient, with a strong community break observed at ~60 m. We also identified a clear zonation of the benthic taxa with depth. This zonation was primarily driven by downward irradiance and temperature, with additional environmental processes playing a minor role in structuring the benthic communities.Main ConclusionsWe show that MCEs in the Chagos Archipelago are distinct communities, and their distribution is driven primarily by irradiance and temperature. Our results highlight the variability in benthic community structure of MCEs, both along the depth gradient and at local geographical scales for the study region. This study showcases the uniqueness of MCEs and will aid in predicting their distribution, potential refugia for shallow reefs, and in developing evidence‐based protection for MCEs, to maintain overall marine biodiversity.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionsupporting

confidence: 73%

Section: Biological Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Light and temperature drive the distribution of mesophotic benthic communities in the Central Indian Ocean

Diaz,

Howell,

Robinson

et al. 2023

Diversity and Distributions

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“…Regional symposia and meetings between these stakeholders should be conducted regularly to break through silos. As deep-reef exploration is costly, much of the existing deep-reef knowledge in the WIO stems from international collaborations (Osuka et al, 2021;Stefanoudis et al, 2022). Therefore, it is important to ensure that parties of international research ventures work together to jointly frame the research agenda, co-conduct fieldwork, and collaborate post-fieldwork for the data analysis, interpretation, and dissemination of results (Recommendation 5; Action 8).…”

Section: Theme 2: Information Collectionmentioning

confidence: 99%

Stakeholder‐derived recommendations and actions to support deep‐reef conservation in the Western Indian Ocean

Stefanoudis

Talma

Fassbender

et al. 2022

Conservation Letters.

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Deep reefs below 30 m provide essential ecosystem services for ocean health and human well‐being such as food security and climate change resilience. Yet, deep reefs remain poorly researched and largely unprotected, including in the Western Indian Ocean (WIO). Here, we assessed current conservation approaches in the WIO focusing on deep reefs, using a combination of online surveys and semi‐structured interviews. Results indicated that deep‐reef data are sparse and commonly stemming from non‐peer‐reviewed or non‐publicly available sources, and are often not used to inform conservation of WIO marine protected areas. Based on those findings, we co‐developed a framework with WIO stakeholders comprising recommendations linked to specific actions to be undertaken by regional actors to improve the capacity of the region to collect and share deep‐reef information. We hope this framework will enhance deep‐reef stewardship and management throughout the WIO and thus aid sustainable blue economic growth in the region.

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Diverse and ecologically unique mesophotic coral ecosystems in the central Indian Ocean

Diaz,

Howell,

Hosegood

et al. 2024

Coral Reefs

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Research on Mesophotic Coral Ecosystems (MCEs; 30–150 m) has grown exponentially in the last few decades, highlighting their rich diversity and extensive distribution. However, they are still largely underexplored compared to shallow-water coral reefs and frequently remain under-protected and under-represented in marine spatial planning. One reason for the imbalance between the high ecological value of MCEs and the limited levels of protection may be that baseline data on MCEs are largely missing to date, yet are crucial to provide evidence-based information for management actions. Here, we present data on the alpha and beta diversity of the benthic communities within MCEs in the Chagos Archipelago, Indian Ocean. Using imagery collected from Remotely Operated Vehicle surveys, benthic invertebrate megafauna were surveyed along the entire depth gradient from shallow to lower mesophotic depths (15–160 m). The diversity of the benthic communities decreased with increasing depth, from shallow water to the lower mesophotic zone. Nevertheless, the deepest parts of MCEs in the Archipelago displayed higher species richness values than several other shallow subtropical regions. In addition, the benthic communities showed high dissimilarity along the depth gradient, indicating that the key driver of community composition change with depth is species turnover (species replacement), revealing the uniqueness of MCEs. This study presents novel findings on MCEs in the central Indian Ocean, demonstrating that they host a high and unique benthic diversity, and highlighting the need to protect these ecosystems to preserve the overall biodiversity of coral reefs.

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Trait-Based Approaches Reveal that Deeper Reef Ecosystems in the Western Indian Ocean are Functionally Distinct

Cited by 3 publications

References 35 publications

Light and temperature drive the distribution of mesophotic benthic communities in the Central Indian Ocean

Light and temperature drive the distribution of mesophotic benthic communities in the Central Indian Ocean

Stakeholder‐derived recommendations and actions to support deep‐reef conservation in the Western Indian Ocean

Diverse and ecologically unique mesophotic coral ecosystems in the central Indian Ocean

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