DOI: 10.1594/pangaea.819825
title: Phytoplankton daily production in the Rhode River, Maryland (USA), 1990-2009

description: Parameters in the photosynthesis-irradiance (P-E) relationship of phytoplankton were used to calculate daily production at weekly to bi-weekly intervals for 20 years at 6 stations on the Rhode River, Maryland (USA). The objectives of this work were to determine the patterns and controls on the P-E parameters and primary production of phytoplankton in a shallow eutrophic estuary. Additional measurements that are components of calculated daily rates of primary productivity are given: the light-saturation irradiance, photoperiod, maximal noon incident irradiance, optical depth, dimensionless depth integrals, and a correction for spectral selectivity of light absorption. P-E parameters and chlorophyll a concentrations were given in a related dataset, Gallegos (2012, doi:10.1594/PANGAEA.816494).
description: Water Sampling: Samples for depth-averaged chlorophyll concentration were collected by slowly lowering and raising a Labline™ Teflon™ sampler in less time than required to fill. Samples for P-E parameters, discrete Chla, and species composition were collected by filling the sampler at the Secchi depth. In the journal articles, stations are referenced by their distance from the mouth: Station 1, -1.4 km; Station 2, 0.0 km; Station 3, 2.0 km; Station 4, 3.8 km; Station 5, 4.3 km; Station 6, 5.2 km. Mean total water depths at the stations were: Station 1, 4 m; Station 2, 3.5 m; Station 3, 3 m; Station 4, 1.94 m; Station 5, 1 m; Station 6, 1 m.Calculation of primary production: The daily rate of primary production (P_HT) integrated over water column depth (H) and time (T) was calculated by equation 39 in Platt & Sathyendranath (1993, doi:10.1029/93JC01001) P_HT=Scalar*F0_H*SpectCorr where Scalar is the product Chla*PBmax*D/DAC, where Chla is the depth-averaged concentration of chlorophyll a, PBmax is the light-saturated rate of photosynthesis normalized to Chla, D is the hours of daylight, and DAC is the diffuse attenuation coefficient, which was either measured (MeasDAC) or calculated from Secchi depth (EstDAC). Chla and PBmax are available at doi:10.1594/PANGAEA.816494 . D and DAC are given here.F0_H is the integral of the non-dimensionalized photosynthesis profile, assuming a sinusoidal variation of incident irradiance over the day. F0_H is the integral from the surface to infinite depth minus the integral from the bottom of the water column to infinite depth, F0_inf-FH_inf. The integrals F0_inf and FH_inf are calculated from 5th order polynomial functions of the dimensionless irradiance at the surface (Estarm) and bottom (Estarbot), respectively. Estarm is the ratio of the noontime surface irradiance, E0max, divided by the light saturation parameter, Ek. E0max was either calculated from the measured daily integral of incident irradiance (MeasE0Max) or by the model of Gregg & Carder (1990, doi:10.4319/lo.1990.35.8.1657) (CalcE0Max) when surface irradiance measurements were unavailable. The light saturation parameter, Ek, was calculated as PBmax/alpha (Model 2, exponential P-E model) or 0.759*PBmax/alpha (Model 1, hyperbolic tangent P-E model in doi:10.1594/PANGAEA.816494). Estarbot is the dimensionless irradiance incident at the optical depth of the bottom, calculated as Estarm*exp(-Kd_H). Coefficients in the 5th order polynomial are given in Platt & Sathyendranath (1993, doi:10.1029/93JC01001).SpectCorr is an empirically derived correction for the spectral selectivity of phytoplankton light absorption in this predominantly green-water system, SpectCorr=1/(0.0647*Kd_H-0.0307).
description: Supplement to: Gallegos, Charles L (2014): Long-term variations in primary production in a eutrophic sub-estuary. I. Seasonal and spatial patterns. Marine Ecology Progress Series, 502, 53-67