Photosynthesis patterns in Chesapeake Bay phytoplankton: short- and long-term responses of P-l curve parameters to light

Abstract

Pigment concentrations and photosynthetic rates of phytoplankton in Chesapeake Bay were examined to determine short-and long-term responses to light. Samples were collected horizontally along a turbidity gradient and vertically relative to the depths of the pycnocline and photic zone. This approach provided phytoplankton assemblages that were exposed to light differing in both ~ntensity and time-scale of change. Photosynthesis-irradiance (P-I) curves and the parameters aB and PmB were assayed at light intensities and wavelength bands that occur in situ. Short-term (minutes to hours) changes in light elicited responses in the distribution of aB and PmB coordinate pairs along a single line. Long-term (days to weeks) differences in light elicited a change in the relation of a* to PmB, manifested as a shifted slope of the linear correlation of these parameters. Photosynthetic efficiencies were similar in light sources of narrow ('blue-green' or 'orange') and broad spectra ('white'), indicating the successful harvesting of light of these spectral qualities by photosynthetic pigments in resident phytoplankton. This similarity in photosynthetic efficiency represents a long-term response that may depend on floral composition and differences In pigmentation. Concentrations and ratios of photosynthetic pigments revealed seasonal and spatial differences in floral composition of phytoplankton in Chesapeake Bay. The presence of chrysophytes, diatoms, and dinoflagellates was indicated by low molar ratios of chl a and c during spring and summer, while the abundance of cyanobacteria (bluegreen algae) was documented by high a:b and a:c ratios in autumn. These findings have implications for the use of P-I curve parameters in diagnosing photoadaptive responses by phytoplankton and for the seasonal abundance of cyanobacteria possibly associated with eutrophication of Chesapeake Bay.

Autotrophic picoplankton dynamics in a Chesapeake Bay sub-estuary

“…P, , , values in this study (Fig. 6b: 1.66 to 11.68 for the > 3 pm autotrophs and 1.05 to 6.90 for the < 3 pm autotrophs) are well within values reported in the literature for natural populations of phytoplankton in the Chesapeake Bay , Harding et al 1985. This study found statistically significantly lower P, , values for the picoplankton fraction than the larger plankton and other fractionation studies have reported this same occurrence (Takahashi & Bienfang 1983, Putt & Prezelin 1985, Cole et al 1986).…”

“…Based on literature values (Harding et al 1985, Glover et al 1985a, it was presumed that 293 pE m-2 s -1 represents saturating light intensity for both fractions and that chlorophyll-specific uptake rates at this intensity represented P,,, (Fig. 6).…”

Phytoplankton photosynthesis, productivity, and species composition in a eutrophic estuary: comparison of bloom and non-bloom assemblages

“…(6) provides a physiological basis for the correlation between aB and PmB frequently observed (e.g. Harding et al 1985). Such a correlation was observed here (Fig.…”

Temporal and spatial variability of photosynthetic parameters and community respiration in Long Island Sound

“…Maximum estimates of P B m and α B in LIS, converted to units of carbon for comparison with 14 C, are 1.5 and 3 times the maximum measured in some other produc- tive systems such as the Chesapeake and Delaware Bays (Harding et al 1985(Harding et al , 1986 , even after removal of weakly fitted P-I curves and exclusion of out- ) was within the same order of magnitude as theory, but still higher. High measurements of α B have also been observed in other studies , Malone & Neale 1981, Kelly & Doering 1997 contrasts with that reported in diel (MacCaull & Platt 1977, Prézelin & Sweeney 1977, daily (Cote & Platt 1983) and seasonal ) P-I studies, where range factors of α B were similar to or less than P B m .…”