01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0062 |
| Title of Abstract | How do eddies influence zooplankton communities in the Southwest Indian Ocean? |
| Authors | Jenny Huggett*, Margaux Noyon, Samantha Ockhuis, Ashrenee Govender, Johan Groeneveld, Tamaryn Morris |
| Organisation | Oceans and Coasts, DFFE |
| Address | 10 Gibson Road, Kenilworth Cape Town, Western Cape, South Africa Pincode: 7708 E-mail: jenny.huggett@gmail.com |
| Country | South Africa |
| Presentation | Oral |
| Abstract | Zooplankton communities globally are strongly influenced by temperature and food availability. On a local scale, these patterns may be moderated by oceanic features such as upwelling and mesoscale eddies. Here, we review three case studies of how eddies influence zooplankton biomass and diversity in the Southwest Indian Ocean ⿿ in the Mozambique Channel, off southern Madagascar, and off the Agulhas Bank. Mesoscale eddies that propagate southwards in the Mozambique Channel play a fundamental role in shaping the pelagic ecosystem through the concentration, enhanced growth and redistribution of zooplankton communities. Zooplankton assemblages in anticyclonic and cyclonic eddies showed a high degree of taxonomic homogeneity, but biovolume was on average 55% greater in cyclonic (cold-core) eddies than in anticyclonic (warm-core) eddies during four cruises from 2007-2010. This was likely due to upwelling in the cyclonic eddies enhancing nutrient concentrations, primary production and food availability, and hence increased zooplankton production. Interaction of large anticyclonic eddies with the shelf can also lead to entrainment and advection of shelf biomass, supplementing offshore feeding conditions for higher trophic-level predators. DNA barcoding of meroplankton within a cyclonic eddy off the southern shelf of Madagascar in 2013 indicated dominance by taxa of coastal origin, supporting the ⿿suitcase hypothesis that planktonic organisms are entrained within eddies as they propagate south-westwards of the Madagascan shelf. Higher abundance of dinoflagellates within the eddy compared to the shelf suggests this community was enhanced through upwelling in the eddy core. Lastly, DNA metabarcoding of zooplankton within a cyclonic eddy off the Agulhas Bank in 2022 indicated that species trapped within the eddy were transported southwards from the Western Indian Ocean within the Agulhas Current and were also entrained from the Agulhas Bank. |
| Are you part of IIOE-2 endorsed project | yes |
| Endorsed Project Number | IIOE2-EP04, IIOE2-EP26, IIOE2-EP57 |
| Keywords | SWIO, mesoscale eddies, zooplankton biomass and diversity, DNA barcoding and metabarcoding, connectivity |
| For Awards | no |