Conclusion
We have investigated diatom distribution in South Korean coastal waters
in winter finding four major ecoregions (YS, SS, SES, and NES). In the
YS ecoregion, the selected indicator species were characterized as
tychoplanktonic and euryhaline diatoms indicating that the region had
uniform water column mixing with freshwater inputs. In the SS ecoregion,
the dominance of chain-forming diatoms was considered to be a response
to the turbulence caused by an uneven coastline and strong tidal flows
and by the Tsushima Warm Current. In the SES ecoregion, having
stalk-forming diatoms such as Licmophora and Achnanthes as
indicator species was thought to be associated with a simpler coastline
with the strong Tsushima Warm Current limiting the distribution of
planktonic species in this region. In the NES ecoregion, the Liman Cold
Current was considered to be the main factor influencing diatom
distribution as our analysis showed that cold-water species such asCorethron criphilum and Porosira glacialiswere its indicator species.
Although the influence of physical, chemical, and biological factors on
diatom distribution was not investigated in this study, the diatom-based
biogeographical groupings and their indicators species have reflected
some factors that can influence the spatial distribution of diatoms in
South Korean coastal waters, in winter.