ESTIMATES OF PHYTOPLANKTON BIOMASS IN THE CHESAPEAKE BAY FROM AIRCRAFT REMOTE-SENSING OF CHLOROPHYLL CONCENTRATIONS, 1989-92

Aircraft remote sensing of surface chlorophyll concentrations with NAS A's Ocean Data Acquisition System (ODAS) was used to determine the sea sonal and interannual dynamics of phytoplankton biomass in the Chesape ake Bay from 1989 to 1992. Flights were conducted at a frequency of 1- 2 per week from late winter through early fall, and were scheduled to coincide with shipboard sampling as weather permitted. The primary sou rces of in situ data for developing and validating biomass algorithms were monitoring cruises sponsored by the Chesapeake Bay Program (CBP) and the NSF-sponsored Land Margin Ecosystem Research (LMER) program of the University of Maryland. The general approach was to recover estim ates of biomass from the relationship of surface chlorophyll to the co ncentration of vertically-integrated chlorophyll weighted bathymetrica lly. The seasonally and annually specific relations used to estimate b iomass were then applied to ODAS estimates of surface chlorophyll for each of >90 flights to produce a time series of total phytoplankton bi omass (in metric tons of chlorophyll) for the Chesapeake Bay. Estimate s of algal biomass averaged approximately 500 metric tons, with maximu m values of 1400 metric tons in spring 1990. These values are in agree ment with estimates computed from the integrated vertical profiles of the CBP database using a 3D interpolator model. The total biomass of p hytoplankton during the spring bloom of 1990 was significantly higher than in 1989, 1991, and 1992. The causes of these interannual differen ces are discussed in terms of variations in Susquehanna River flow and nutrient loading to the estuary.