Trends in functional group richness and trait
composition
The simplest approach to defining functional diversity is thefunctional group richness (FGR). To calculate the FGR for the
samples, species were divided into basic functional groups .
Functional groups were defined by combining higher level taxonomic
classification (mostly Class) with the feeding mode. The prominent
groups Cladocera and Copepoda were further classified into ‘large’ and
‘small’. Values of a relatively simple set of functional traits was
assigned to more frequently encountered zooplankton taxa (species or
higher) in order to analyse the shifts in functional composition of
communities in further detail (Table 1).
Table 1 . Functional traits used in this paper, and organization
of trait table. Trait values are shown for 10 most frequent taxa in Gulf
of Riga. “Complexity” is a four-level proxy for the complexity
(body size, reproduction) of the organism: ‘1’ – rotifers; ‘2’ –
cladocerans, ‘3’ – copepods; ‘4’ – other (more complex) organisms
(e.g. Polychaeta, Meroplankton, Mollusca). Filtering and predation: 1 =
yes, 0 = no.