Polychaete (Annelida) diversity in the impacted Berg River Estuary, South Africa

Abstract Although Ramsar-listed, the Berg River estuary (South Africa) is anthropogenically impacted and severely understudied. Four studies conducted between the 1950s and 2000s found that polychaetous annelids in the estuary are represented predominantly by capitellid, spionid and nereidid species. This study provides an updated taxonomic inventory of polychaetous annelids in this estuary, with COI, cytb and 16S DNA sequence data to facilitate future molecular-based biodiversity studies. 3840 specimens (16 species from seven families) were collected from 9 sites from the mouth of the estuary to 15 km upriver; Spionidae was the most species-rich, followed by Nereididae, with remaining families represented by one or two species each. Richness decreased further from the estuary mouth with only Capitella sp. and Prionospio cf. sexoculata present throughout. Capitella sp. contributed 70% to 100% of individuals collected at sites near urban and industrial areas, suggesting widespread pollution. Nereididae were abundant in less saline waters, while Boccardia spp. were abundant at the mouth only. Bayesian analyses of sequences generated for abundant and widespread taxa in the Berg River Estuary retrieved eight well-supported groupings confirming morphological identifications, with the detection of multiple lineages for Boccardia pseudonatrix , Simplisetia cf. erythraeensis and P . cf. sexoculata from several locations globally. Multiple Barcoding Identification Numbers for Capitella sp. and Orbinia angrapequenes contradict Bayesian analyses, suggesting species-complexes for these taxa too. All taxa therefore require revision locally and globally.