Picoplankton carbon flux in Chesapeake Bay

Abstract

Examines phototrophic and heterotrophic picoplankton (P- and H-PICO, respectively) and on the flow of carbon from phytoplankton to H-PICO. Annual cycles in the biomass and productivity of both picoplankton trophic levels exhibit winter-spring minima and summer maxima but do not appear to be directly coupled in terms of carbon flow from P- to H-PICO. H-PICO exceeds P-PICO during spring when picoplankton productivity is low, and P-PICO exceeds H-PICO during summer when productivity is high. P-PICO productivity and biomass increase rapidly each year to an early summer peak (20% of total phytoplankton productivity on average) immediately following the collapse of the spring diatom bloom. H-PICO productivity and the abundance of bacterioplankton (the predominant group of H-PICO) increase slowly to a late summer peak (equivalent to 16% of phytoplankton productivity on average). Recently released phytoplankton exudates are a major source of dissolved organic carbon with H-PICO taking up an average of 54% during spring and 83% during summer. Variations in H-PICO are closely coupled to the release of DOC, most of which is produced by phytoplankton >2 μm. New nutrient input to the Bay appears to be coupled to H-PICO productivity via increases in the productivity and DOC release of phytoplankton >2 μm in size. -from Authors