Diatoms as indicators of environmental health on Korean islands

Diatoms are highly sensitive to perturbations in their environment and are thus useful as bioindicators for anthropogenic impacts such as pollution. However, there is no consensus about what aspects of diatom populations to measure (e.g., diversity, physiology, or morphology) and efficient and reliable survey protocols are lacking. Here, we evaluated the ecological status of diatom communities using both traditional and relatively novel methods on two islands (Deokjeok island and Daeijak island) affected by anthropogenic activities due to extensive agricultural practices and exploitation and that are under consideration for representative touristic sites in South Korea. Dissolved concentrations of metals and metalloid (As, Cu, Cr, Cd, Ni, Hg, Pb, and Zn) were below the ecological screening and toxicity reference values in water fractions but were above these values for sediment, particularly at one island, Deokjeok. The tested methods were generally consistent in finding little evidence for disruption of diatom communities, with dominance by Navicula and Gyrosigma, relatively high diversity, and typical abundance of lipid bodies and morphological deformities. However, analysis of lipid bodies and morphological deformities suggested greater potential anthropogenic disturbance at one site in Deokjeok. Future planning is required to ensure the maintenance of the near-pristine environments present on these islands.