Data from: Examining marine assemblages across an inverse salinity gradient

Salinity gradients and fluctuations can create a natural ecological
filter, with few species tolerating salinity above 50 practical salinity
units (PSU). We investigated how an inverse salinity gradient affected
marine community diversity and composition in Shark Bay, a remote
hypersaline coastal embayment in Western Australia. We used 16S(fish),
18S, and 16S(Bacteria) eDNA metabarcoding assays to analyse genetic
sequences collected from 220 surface water samples and 216 benthic roller
samples. The 44 survey sites transcended a salinity gradient of 40.1 PSU
in the Eastern Gulf to 76.0 PSU in Hamelin Pool. 24,011,345 eDNA
sequencing reads were detected from 5,575 operational taxonomic units
(OTUs). The number of Families and OTUs, and OTUs within key Phyla, all
decreased with increasing salinity, the most dramatic changes occurring
over a narrow salinity range (50 - 60 PSU). However, the relative
proportion of Families from each Phyla contributing to the total
assemblage within each salinity range remained relatively stable. Key
processes may therefore be maintained across the salinity gradient,
although redundancy and resilience are compromised as diversity declines
and the taxonomic composition of the communities change. Although primary
producers such as cyanobacteria, seagrass and the bivalve mollusc Fragum
spp. were under-represented within our data set, this may be due to a
limitation of the eDNA methods used rather than their lack of presence
within the ecosystem. Even with these limitations, eDNA has proven a
useful tool for examining the whole marine assemblage across an inverse
salinity gradient in a remote area at a broad taxonomic level.