The maximum quantum yield of phylopiankton photosynthesis in situ

Light-limited photosynthetic carbon incorportion is expected to be directly proportional to the scalar quantum irradiance. The proportionality constant is φ $kc¯$ , where φ _m is the maximum quantum yield (mol C Einstein ⁻¹ absorbed) and $kc¯$ is the mean spectral absorption coefficient (m ² mg ⁻¹ chl a ). Recent efforts to evaluate φ $kc¯$ of in situ phytoplankton photosynthesis are variously flawed. Lack of evidence of proportionality and lack of correction of cosine to scalar irradiance are common deficiencies. Most data, as we interpret them, indicate φ $kc¯$ values in the range 0.0003 – 0.0006 mol C m ² Einstein1 abs mg1 chl a . New determinations in lrondequoit Bay, New York, lie in this range. Most estimates of $kc¯$ at depth have been about 0.010 m ² mg ⁻¹ chl a . Similar values are being obtained for total particulates from lrondequoit Bay; whether detritus contributes significantly is not yet known. Published data, in our view, all point to values of m in situ in the range 0.03−0.07 mol C Einstein ⁻¹ abs. Published values >0.10 are almost certainly due to imprecision or systematic error.