A comparison by size class and volume of detritus versus phytoplankton in Chesapeake Bay

Abstract

Relative numbers and sizes of detritus vs. phytoplankton particles were determined by visual counting over a period of 17 months at a mid-bay station in a temperate estuary. Detritus averaged 76.6% of total particle numbers, the phytoplankton 23.4%. Seasonal variation in detritus numbers was minimal as compared to the strong summer pulse of the phytoplankton. Detritus numbers were concentrated in the smallest size category (64.7% at 2–5 μm) as were the phytoplankton (55.6% at 2.5 μm). Detritus particles also overshadow the phytoplankton in total volume present, representing 65.7% of total yearly volume, the remaining 34.3% of total volume representing live cells. The peak of detritus volume determined by visual counts is at the high end (20–35 + μm), whereas phytoplankton volume peaks at mid ranges (5 +–20 μm). Phytoplankton occurrence and abundance, and the per cent of phytoplankton volume contributed by each taxonomic class, are also recorded.