Deep reef ecosystems of the Western Indian Ocean: addressing the great unknown

Indian Ocean coral reef ecosystems are some of the least explored, least funded and least protected worldwide. "First Descent: Indian Ocean" represents a series of research expeditions undertaken by Nekton between 2018-2022 in partnership with Governments in the Indian Ocean region to contribute to establishing a baseline of marine life and catalyse 30% protection by 2030. Two recent expeditions, the 2018 WILDOCEANS/ACEP Comoros Mesophotic Biodiversity Expedition (led by WILDTRUST), and the 2019 First Descent: Seychelles (led by Nekton Foundation) systematically surveyed deeper reef ecosystems in those areas, resulting in collections of biological meterial and underwater footage. In August 2019, taxonomic experts from across the globe, attended a workshop in order to identify the collected material and provide a first snapshot of the diversity of the surveyed habitats. Part of the workshop also focused on providing taxonomic training to host nation scientists and early career researchers. This document is a report on the proceedings and some of the first outcomes of this workshop. ‡,§ §,| ‡,¶ ‡,§ © Stefanoudis P et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Date and place
The taxonomic workshop was held at the National Research Foundation, South African Institute of Aquatic Biodiversity (NRF-SAIAB) in Grahamstown between the 1st to the 9th of August 2019.

List of participants
The workshop was divided in 2 parts: • Part 1 (01.08.2019 -05.08.2019) was attended by taxonomic experts only, who worked together in order to identify the collected biological specimens, and process the associated underwater footage. • Part 2 (06.08.2019 -09.08.2019) also included host nation scientists and earlycareer researchers, who were trained in the identification of the major groupings represented in the collected samples and imagery.
A total of 28 people from 10 different countries were directly or indirectly involved with the workshop, with diverse affiliations ranging from Universities and Research Institutes, to Governmental Departments and Non-Governmental Organisations.
Sixteen were taxonomic experts covering all major benthic groups. Six of those physcially attended the workshop and provided hands-on training sessions and lectures, five joined remotely to give online lectures, and a further five were involved with identification of specimens post-workshop.
Finally, a total of nine individuals from Seychelles, Comoros and South Africa joined for the training session.
For a full list of participants see Table 1.

Background
The Indian Ocean is among the least known (http://www.obis.org), least funded (<2% of all financial commitments at Our Oceans 2018 was aimed for the Indian Ocean) and least protected water mass ( http://www.mpatlas.org), with its coastal population highly reliant on seafood harvests (e.g. Obura et al. 2017). Global threats from the consequences of climate change (e.g. increased storm intensity and increased frequency and severity of coral bleaching events), and local effects of human activities (e.g. fishing, pollution) are evident and cumulative (e.g. Hoegh-Guldberg et al. 2014, Breitburg et al. 2018Watson et al. 2012, highlighting the need for a better understanding and management of Indian Ocean marine ecosystems. Most of the past and present reef surveys and monitoring efforts in the Indian Ocean have been focusing on shallow-waters (≤30 m), leaving adjacent, deeper mesophotic (30-150 m) habitats understudied (Pyle and Copus 2019). Much less is known about species connectivity between the mesophotic zone and those that inhabit deeper reef habitats, such as those located in the rariphotic zone (150-300m). If we are to sustainably manage and conserve those deeper reef habitats to help ensure they thrive and provide a full range of ecosystem services, it is imperative to know what lives there.
Nekton Foundation launched "First Descent: Indian Ocean", a series of research expeditions to take place between 2018-2022 in order to contribute to establishing a baseline of marine life in the Indian Ocean and address the issues raised above. In 2018, Nekton successfully collaborated with other research organisations (WildTrust) to conduct field resarch in Comoros, and in 2019 completed its first major research expedition in Seychelles, working with, and on behalf of the Government of Seychelles.
During 48 days the First Descent expedition collected hundreds of biological samples from depths between 10-250 m. The real challenge, however, was still ahead: the processing, statistical analysis, and interpretation of the collected marine data. Taxonomic workshops represent invaluable tools to expedite this process. These events represent a unique opportunity to bring together participating scientists and taxonomic experts across the globe, in order to accelerate the taxonomic identification and analysis. At the same time, if designed appropriately, they can also provide training to early career researchers from the world's best experts, thus ensuring that taxonomic knowledge and expertise is passed on to the next generation of marine scientists.

Aims of the workshop
The aims of the workshop were two-fold: 1.
To accelerate the assessment of the deeper reef biodiversity of the Western Indian Ocean (WIO) fauna and flora, by examining biological specimens and underwater footage collected during the 2019 First Descent: Seychelles expedition. Additional specimens collected in the Comoros Archipelago during the 2018 WILDOCEANS/ ACEP Comoros Mesophotic Biodiversity Expedition (led by WILDTRUST) were also included to better understand community similarities between those neigbouring regions.

2.
Provide training to host nation scientists and early career researchers on mesophotic and deeper benthic organisms, including corals, sponges and other invertebrates, which will help contribute towards creating a legacy for long-term research and effective science-based ocean management for marine biodiversity.

Agenda
During the first part of the workshop, the majority of activities took place in a laboratory setting in order to facilitate the identification of collected specimens by the taxonomists. During the training part, it was a mixture of lectures introducing the trainees to the major benthic taxonomic groups typical in reef habitats, followed by hands-on practical sessions with representative samples from some of these groups (see Fig. 1). Other events included a safari trip, and post-workshop social gatherings, which gave the participants the opportunity to get to know each other better and network. A full list of the activities that took place can be found on the workshop's agenda in Table 2.

Key outcomes and discussions
During the workshop, we identified at total of 632 biological samples from the Seychelles expedition, including subsamples of larger organisms taken for post-workshop molecular and scanning electron microscopy work. These included (in decreasing order): 189 sponges, 99 octocorals, 67 brittle stars, 52 crabs, 36 hydroids, 19 sea urchins, 17 shrimps, 14 crinoids, 12 gastropods, 10 red algae, 9 sea stars, 9 polychaetes, 8 green algae, 7 bryozoans, 6 bivalves. The remaining 78 was a combination of other taxonomic groups and fin clips of fish, the latter to be used to facilitate an additional study led by one of the participants.
The respective numbers for the Comoros survey were 44 biological samples: 20 octocorals, 7 sponges, 3 crinoids and 14 belonging to other groups.
We also reviewed hundreds of taxa in their natural environment by examining the rich underwater footage collected from both research expeditions.
As a result of the participating experts it was possible, in just two weeks, to gain first impressions of the diversity of Seychellois and Comorian reefs. This task would have taken months, or in some cases it would have not been possible at all, if it was tackled by a few individuals or one institution alone. Initial results, revealed numerous genera and species of sponges and corals, many of which represented new records for Seychelles and Comoros and in some cases for the whole of the Indian Ocean, as well as significant depth range extensions, thus improving our knowledge of the biogeography for the region. Interestingly, taxonomic experts thought they found potentially dozens of new species, both from shallow and deeper waters, indicating that reefs in the WIO are still poorly known. Additional, more detailed taxonomic work will be required to confirm those initial beliefs in the coming months.
Through the lectures and practical laboratory sessions, host nation scientists and early career researchers were able to obtain a holistic understanding of the different benthic groups present in reef ecosystems, and the multitude of steps required to make accurate identifications. Participants learnt, that identification of physical samples is a timeconsuming, yet necessary process, which typically involves the use of stereo-and light microscopes along with identification guides, but in many cases requires additional steps such as comparisons with type specimens in museum collections, or the use of scanning electron microscopy and DNA sequencing. For those dealing with identifications of specimens from underwater imagery and videos, it became clear that identification is often made to the lowest taxonomic level possible, which depending on the taxon might be to genus or family level. Furthermore, matching the commonly observed organisms in marine footage with physically collected samples, can enhance the taxonomic robustness of a study.

Conclusions
Overall, throughout the industrious nine days at NRF-SAIAB, we were able to enhance our taxonomic knowledge of the WIO reef fauna and provide networking opportunities and potentially foster new collaborations between scientists from the region. The provided training and knowledge exchange opportunities for host nation scientists and early career researchers, will hopefully prove useful in the coming years.

Hosting institution
National Research Foundation, South African Institute of Aquatic Biodiversity

Ethics and security
All biological specimens processed during the workshop had appropriate permits in place, issued by the Government of Seychelles.
No CITES listed specimens were used.

Conflicts of interest
We have no conflict of interest to report.