Conclusions
The essence of using functional traits is to characterize organisms by
properties that capture essential aspects of diversity, rather than to
analyse individual species. In the current paper, we have used traits to
determine how the zooplankton community is associated with environmental
gradients in a highly eutrophicated gulf. The benefit of looking into
traits have revealed systematic changes in the current community – the
long-term decrease of copepods, increase of rotifers and dominance
shift. On the other hand, the proportion of simpler organisms have
increased in spring, whereas the proportion of more complex organisms
have increased in late summer. Salinity did not have a clear effect on
our functional traits, which could be due to the fairly small
fluctuations in the Baltic Sea salinity. Neither oxygen concentrations
affected traits significantly, which may depend on the fact that oxygen
was fairly stable in the used time series; planktonic organisms are also
very much able to move away from hypoxic areas. Our data also suggest
that organisms of low complexity will benefit from the climate-induced
warming of the environment, whereas salinity and oxygen levels seem to
have minor effect on the planktonic community in the Baltic Sea, here
exemplified by Gulf of Riga basin.