Zooplankton in the surf zone and adjacent shallow subtidal waters: Differences in community patterns between close seascapes

GONELLA FM; OSINAGA M.I.; BALEANI C.A.; SULKJE L.M.; CARCEDO M.C.; BLASINA G.E.; FIORI S.M.; MENÉNDEZ M.C.

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Conferencia; The 3rd International Electronic Conference on Diversity; 2024

Multidisciplinary Digital Publishing Institute (MDPI) and Diversity (Journal)

Zooplankton that drift or weakly swim are influenced by water column structure and hydrodynamics. This investigation studied zooplankton communities in the surf zone (SZ) of sandybeaches, characterized by shallow and turbid waters due to wave propagation, and the adjacentshallow subtidal (SSZ), with calmer, deeper waters. This research presents a novel approach byconcurrently studying these communities in both zones. Samples were collected bimonthly for ayear at Monte Hermoso, Argentina (38°59’S, 61°18’W), using a 200 um mesh zooplankton net byhand-trawl in the SZ and from a vessel in the SSZ. We analyzed species richness, Shannon andSimpson's diversity, -diversity, taxonomic composition, and spatial variability in abundancebetween zones. No differences were found between zones in richness, but Shannon andSimpson's diversity werehigher in the SZ. -diversity reflected species turnover (Bsim =0.294,Bnes=0.0982), with approximately 40% taxonomic dissimilarity (Bsor=0.392) throughout the year.We identified 55 taxa in 15 major groups. Copepoda, Mollusca, Annelida, and Chordata accountedfor over 90% of total zooplankton abundance. The results revealed abundance differences, withtotal abundances in SZ greater than SSZ (p menor 0 .001; SZ=2708ind.m ³; SSZ=134ind.m ³), drivenpredominantly by copepods (p menor 0.001; =0.96). These differences were reflected in copepodcomposition, with Acartia tonsa predominating in the SZ, while Paracalanus parvus dominated theSSZ. Both species exhibited similar seasonal patterns, peaking in warmer months for A. tonsa andin winter for P. parvus. In the SSZ, we registered more neritic taxa (e.g., Chaetognatha, Cnidaria,Ctenophora), whereas in the SZ we found more larval stages of benthic organisms from nearbypopulations (e.g., Echinodermata, Mollusca, Spionidae, Decapoda) and benthic organisms likeCumacea and Amphipoda. The coexistence of estuarine and neritic species highlights theinterconnectedness of coastal habitats and provides insights for future ecological studies.