Page 6 - ZooplanktonReadMe

Zooplankton Food Web

Using these long-term zooplankton biomass
data, along with multi-year phytoplankton
biomass estimates, we constructed three
food web models for the plankton
community in the SoG using Ecopath
(https://ecopath.org/). Each model provides
a steady-state, but seasonally-varying,
mass balance in one of three seasons in the
SoG: spring, summer, and winter. Our
models describe the plankton community
using fifteen functional groups, with
variations in biomass, diet, and growth and
consumption rates. These functional groups
include heterotrophic bacteria,
phytoplankton, mixotrophic
microzooplankton, and mesozooplankton.

The models indicate that the planktonic
component of the food web in the Strait of
Georgia spans 3 trophic levels. All
mesozooplankton have lower trophic levels
in the spring than the other two seasons,
indicative of the shift to more herbivorous
activity in this season. After the spring bloom, microzooplankton increase in dominance and
zooplankton diets shift to reflect this change in food availability, increasing their trophic
position.

These taxonomically diverse, seasonal models give insights into how energy pathways and
trophic interactions within the plankton community vary between the seasons. These structural
changes within the plankton food web throughout a year have implications for higher trophic
levels, including the seasonal availability and quality of food for plankivorous fish. Further, they
can be applied to nutrient cycling, detrital sinking, and contaminant bioaccumulation through
the food web.