Regional and Environmental Data
For comparison to the field dataset, a regional dataset was created using identifications from OBIS. All bivalve records for Australia were downloaded on 4th May 2020 using the R package robis (Provoost and Bosch, 2020). Data were spatially restricted to only include coastal cells within the latitudinal range of the field sites (16.7 – 37.2 °S). Species names were checked against the World Register of Marine Species using the package worms in R (Holstein, 2018, WoRMS Editorial Board, 2018) in order to remove erroneous species names and synonyms and to check family assignments. Only records with georeferenced collection locality data recorded to 2 decimal places, valid species names, and collection dates after 1980 were included. This resulted in a regional dataset including 7,480 records of 600 species.
For bivalves in our study area, 612 records are recorded on OBIS as “Human Observation”. To avoid potentially erroneous identifications, only records tagged as “Preserved Specimen” were retained for our main analysis. We ran an additional analysis with the observational data included to make comparisons.
Records were pooled into 0.1° cells to approximate the spatial scale of the field data. Cells with fewer than 10 records were omitted to allow for more accurate diversity estimation. To account for the difference in the number of cells between datasets, a subset of the OBIS data was created that only included cells centred on field sites.
Environmental data for the eastern coastline were downloaded from the CSIRO Atlas of Living Seas (Ridgway et al. , 2002), which provides ocean water properties on a 0.5° grid, on 10th May 2020. Variables downloaded were the most recently available ones for mean annual sea surface temperature, mean annual salinity, mean annual dissolved oxygen content, and mean annual nitrate, silicate, and phosphate content.