Ongoing activities

Deep reef ecosystems of the Indian Ocean: the big unknown

Paris Stefanoudis1,2, Nico Fassbender2, Kaveh Samimi-Namin1,2, Jerome Harlay3, Denise Swnaborn1, Sheena Talma1,4, Lucy Woodall1,2

1University of Oxford, UK, 2Nekton Foundation, UK, 3University of Seychelles, 4Ministry of Environment, Energy and Climate Change, Seychelles

Indian Ocean coral reef ecosystems are one of the least explored, least funded and least protected reefs worldwide. The Nekton-led 'First Descent: Seychelles' expedition in 2019 sought to address that gap by exploring coral reef habitats in seven remote coral atolls across the Exclusive Economic Area of Seychelles. A combination of divers, submersibles and remotely operated vehicles were deployed between 10-350m to investigate the biodiversity and connectivity patterns of benthic and fish communities across depth and location. Preliminary results indicate distinct biological groupings across depth, corresponding to a shallow, mesophotic, and rariphotic coral reef zones. There was great variability of reef health between location related to unique local conditions (e.g. topography, current regime) as well as management and protection status of each coral atoll. Since the majority of reefs in the Indian Ocean, including those of Seychelles, have never been systematically explored beyond SCUBA depth (i.e. >30m) before, it is expected that the resulting datasets from this expedition will provide important baseline information on the status of deep reef ecosystems across the region, which will be of value to existing, ongoing and future marine spatial planning exercises of Large Ocean States.

The findings of this work were disseminated during the 14th International Coral Reef Symposium in Bremen, Germany. A peer-reviewed publication from this work are expected in late 2020/early 2021.

Surface Zooplankton Communities from Bermuda

Molly Rivers1, Paris V Stefanoudis1, Lucy C. Woodall1,2

1Nekton Foundation, UK, 2University of Oxford

We sampled the topmost surface layer (0‒0.5 m) with a single Neuston frame system (SEA-GEAR; mouth opening 0.5 m2, net mesh size: 300 μm) in several locations in the NW Atlantic (Bermuda, the Gully region on the Scotian Shelf, Kelvin Seamount, Gulf Stream Frontal Area). Data has been collected, and currently, we are performing statistical analysis. The results of this work will are planned to be published in 2020. Below, you can see some representative fish larvae found in our samples.

Day and Night Zooplankton Community Variation in the Tropics

Zooplankton form a trophic link between primary producers and higher trophic levels, and exert significant influence on the vertical transport of carbon through the water column (‘biological carbon pump’). Using a Neuston Net we sampled surface mesozooplankton communities (i.e. >0.3 mm) from seven remote coral atolls in Seychelles during the day and night. Copepods consistently dominated samples, irrespective of time of collection. Other groups such as fish larvae were more common in night samples, indicating substantial vertical migration for this group. Below, you can see visualise some of those community differences between day and night samples.

The collected samples are currently being processed and first results of this work are expected by May-June 2020. An accompanying peer-reviewed publication will be published in late 2020 / early 2021.

Zooplankton communities from the SW Indian Ocean

Molly Rivers1, Paris V Stefanoudis1, Lucy C. Woodall1,2

1Nekton Foundation, UK, 2University of Oxford

We used a Hydrobios MultiNet MiDi zooplankton sampler (mouth opening 0.25 m2, net mesh size: 180 µm) to sample the water column at 5 pre-defined depths in the Southwest Indian Ocean. These depths correlate to the Florescence Maximum (F-Max) with two above (0-50; 50–100 m), one within (100–150 m) and two below the F-Max (150–200; 200–250 m). The zooplankton assemblages at each depth are currently being processed and analysis is expected to finish by the end of 2018.