Diversity of gelatinous zooplankton (Cnidaria, Ctenophora, Chaetognatha and Tunicata) from a subtropical estuarine system, southeast Brazil

We surveyed the gelatinous zooplankton (Cnidaria, Ctenophora, Chaetognatha, Tunicata) fauna from the Cananeia-Iguape Coastal System (CICS; São Paulo, Brazil; ~ 25°S). This area includes a natural reserve formed by the Atlantic Rain Forest and mangroves, having a high biological productivity and being recognized as a wildlife sanctuary. We analyzed 164 plankton samples collected between January 2012 and January 2013, along with visual records of living and stranded large (>2 cm) gelatinous zooplankton. More than 29,000 organisms were studied, which combined with literature totaled 16 orders, 40 families and 56 species: two cubomedusae, five scyphomedusae, two siphonophores, 34 hydromedusae, two ctenophores, five chaetognaths, three appendicularians and three thaliaceans. Twenty-seven species are new records for the CICS, six species for the state of São Paulo, and Tiaricodon sp. is newly recorded for the Brazilian coast and is described in details. Most of the species from CICS (37 spp.; 66%) are meroplanktonic, whereas the most abundant taxa are holoplanktonic (>95% of all gelatinous). Meroplanktonic taxa tended to be more species rich in brackish-waters (salinity 20–30) with most species occurring in one or two seasons, particularly during summer and/or autumn, while holoplanktonic species tended to occur throughout the year, and to be more species-rich in more saline waters (>30). These observations indicate different strategies of estuarine occupation driven by life cycle. Our results underscore the high diversity of meroplanktonic gelatinous organisms from subtropical estuaries and emphasize the need for comprehensive sampling surveys in such ecosystems, which are mostly understudied worldwide.