Search

Lobster phyllosoma larvae collected during surveys over the continental shelf of eastern South Africa (southwestern Indian Ocean) were analysed to determine the role of the KwaZulu-Natal (KZN) Bight as a pelagic nursery area. Surface waters in the shallow bight and further offshore, between the 20- and 1,000-m depth contours, were sampled with plankton nets in 2018 to 2023. Phyllosomas were absent from 87.9% of 257 tows, with high variability in the remaining tows indicating a patchy distribution with abundance hotspots. Phyllosomas of four scyllarid and three palinurid species were found among 311 captured specimens. The scyllarid Acantharctus ornatus (Holthuis, 1960) was the most abundant, constituting 94.9% of the phyllosomas caught, with all nine larval stages (I–IX) present. Phylogenetic analysis using the COI and 16S rDNA gene markers confirmed that previously undescribed early larval stages in samples belonged to A. ornatus. Most A. ornatus phyllosomas were caught at shallow-bight stations, with catch rates declining steeply to the north and south of the bight and when bottom depth exceeded 100 m. Season and sampling station (nested within cross-shelf transect) were significant variables in explaining phyllosoma abundance. We provide evidence that the KZN Bight serves as a pelagic nursery area for A. ornatus phyllosoma larvae at all developmental stages, but not for other lobster species with known adult populations in the region. [ABSTRACT FROM AUTHOR]

Zooplankton plays an essential role in marine ecosystems as the link between primary producers (phytoplankton) and higher trophic levels in food webs, and as a dynamic pool of recruits for invertebrates and fish. Zooplankton communities are diverse with a patchy distribution at different spatial scales, influenced by oceanographic processes. The continental shelf of eastern South Africa is narrow and exposed to the western‐boundary Agulhas Current, with some shelter against strong directional flow provided by the broader KwaZulu‐Natal Bight, a coastal offset adjacent to an estuary. We compared zooplankton species richness, diversity and relative abundance of key taxa among sheltered and exposed shelf areas using metabarcoding and community analysis, to explore the ecological role of the bight in a highly dynamic ocean region. Metabarcoding recovered higher richness and diversity at a finer resolution than could previously be achieved with traditional microscopy. Of 271 operational taxonomic units (OTUs) recovered through metabarcoding, 63% could be matched with >95% sequence similarity to reference barcodes. OTUs were dominated by malacostracan crustaceans (161 spp.), ray‐finned fishes (45 spp.) and copepods (28 spp.). Species richness, diversity and the relative abundance of key taxa differed between sheltered and exposed shelf areas. Lower species richness in the bight was partly attributed to structurally homogeneous benthic habitats, and an associated reduction of meroplanktonic species originating from local benthic–pelagic exchange. High relative abundance of a ray‐finned fish in the bight, as observed based on fish eggs and read counts, confirmed that the bight is an important fish spawning area. Overall, zooplankton metabarcoding outputs were congruent with findings of previous ecological research using more traditional methods of observation. [ABSTRACT FROM AUTHOR]