Portfolio Effects in Nearshore Primary Producers and Their Relation to
AbstractEcosystem functions can be amplified or dampened by species responses to
biotic and abiotic factors in the environment. In a group of marine
primary producers, consisting of phytoplankton and kelp species, we
tested for the features indicating Jensen's Inequality and synchronous
or asynchronous dynamics that would indicate a Portfolio Effect.
Nonlinearities that would drive an effect through Jensen's Inequality
were weak and the relationship between environmental drivers and species
fluctuations were often highly variable. Asynchrony dominated the
multi-species assemblage, providing evidence of Portfolio Effects. The
two canopy kelp species, however, showed temporal and spatial synchrony.
Canopy kelp species had strong spatial autocorrelation up to 50 km.
Spatial synchrony occurred over almost 300 km, with increased strength
in spatial synchrony in two recent decades compared to the early 1990s.
This potential Moran Effect, where an environmental variable generates
large-scale biological synchrony, may increase the vulnerability of kelp
populations into the future.