Long-term shifts in trait composition
The significance of long-term variability was judged from the deviance
explained by the GAM curves. Only the coastal community in August did
not change over time, when judging from the GAM fit on A1 and A2 as a
function of year (Figs. 3c, g). In all other cases (open gulf in August,
and both open and coastal areas in May), pronounced long-term
variability occurred both in A1 (mostly reflecting the feeding type) and
A2 (mostly reflecting the complexity).
Most conspicuous trends in functional composition were the shift towards
negative values of A1 indicating a shift from filtering organisms to
mixed feeders and predators in the open sea late summer communities
during the 1980s to early 2000 (August: Fig. 3d), although this trend
reversed in early 2000 simultaneously with a shift towards more complex
organisms (until 2000). Also in both areas in May (Figs. 3a, b), the
long term trend was towards increasing share of mixed or predatory
feeding type.
Significant long-term variability was also evident in A2 values. In the
spring communities (May), the prominent long-term shift in complexity
was towards higher share of simpler organisms (Figs. 3e, f). In August,
the functional composition of both coastal and open area communities
remained almost unchanged.