An exploration of Lake Ontario’s offshore epibenthic cladoceran community

Abstract

Pelagic cladocerans are relatively well studied within the Great Lakes. However, little is known about cladocerans that more closely interact with benthic substrate. In 2018, 26 sites in Lake Ontario were sampled with benthic grabs to collect meiofauna. The stations ranged in depth from 0.1 to 184 m with sand, silt or hard bottom substrate. Epibenthic cladocerans were recovered from all 12 sites shallower than 20 m, five of eight sites between 20 and 40 m and one (63 m deep) of six sites deeper than 40 m. The density of epibenthic cladocerans were at most 12% of the density of harpacticoid copepods (shallow hard bottom sites). The Lake Ontario epibenthic cladoceran community was represented by 16 species from 8 different genera although one of these species, Illyocryptus cf. sordidus, is likely represented by two cryptic species. The most widespread species was identified as Alona sibirica (Sinev, 2020), a newly described species from Russia formerly of the Alona cf. affinis (Leydig, 1860) species complex. The Great Lakes specimens were 98.3% similar genetically to sequences assigned to A. cf. sibirica. Among substrates, sand had the highest densities (1662 m2 in 0–20 m) and species richness (10) of epibenthic Cladocera. After cladocerans were identified, the cytochrome oxidase I (COI) gene of 37 specimens were successfully sequenced through the Barcode of Life (BOLD). Six specimens were assigned to three previously existing Barcode Identification Numbers (BINs), the remaining 31 specimens were assigned to eight new BINs.