Potential applications of an empirical phytoplankton production model to shallow water ecosystems

Abstract

An existing empirical model for predicting estuarine phytoplankton net production on the basis of chlorophyll a standing crop ( B), optical depth ( Z p), and surface irradiance ( I o) has been adapted for application to shallow water systems (referred to as the BZ p I o model). The original model has proven to be a good predictor of phytoplankton production in estuarine systems where depth exceeds the photic zone. It had yet to be tested in shallow estuarine systems where the photic zone exceeds water depth. The model is relatively simple, with chlorophyll a, light extinction, and daily surface irradiance as its only inputs. Based on existing phytoplankton α and P max data, upon which one of the original BZ p I o models was produced, production across depth was integrated at two irradiance extremes, and related to a third-order polynomial correction formulation ( Z cor). Due to the tendency for production to be measured via O 2 incubations in shallow systems, this correction term has not yet been tested against 14C data. O 2 incubations really measure net community production, not net phytoplankton production, and therefore significant variability is introduced. Other factors that may increase variability in this model include measurements and estimates of water column light extinction and depth distribution.