Potential effects of sediment contaminants on diatom assemblages in coastal lagoons of New Jersey and New York States

•A correlation between diatom assemblage composition and contaminants was found.•Abundance of small centric diatoms in surface sediments increased with pollution.•Most benthic diatoms declined with pollution, but a few benefitted from it.•Planktonic diatoms are getting more abundant with time.

Sediment samples from the coastal lagoons and estuaries of New York and New Jersey were used to investigate the influence of contaminants on diatom assemblages. Multivariate analyses demonstrated correspondence between composition of diatom assemblages and concentrations of several metals and total PAH. The effects of the individual contaminants were difficult to disentangle because of the considerable correlations between their concentrations. The most conspicuous trend was the increase in the relative abundance of small centric planktonic diatoms in response to contamination and the corresponding decrease in the benthic flora. The high relative abundance of planktonic species on contaminated sediments apparently resulted not so much from their tolerance to pollution, but from the paucity of benthic species. A comparison of the assemblages on the surface and at the depth of approximately 8-10 cm revealed a statistically significant temporal change in community composition towards planktonic diatoms.