Possible causes of temporal fluctuations in primary production of the microphytobenthos in the Danish Wadden Sea

Abstract

Short-term changes of the benthic primary production on a tidal sandflat were investigated during low tide and correlated with fluctuations in environmental parameters (light, temperature, salinity and pH) and the possible causal relations were tested in laboratory experiments. There was an almost linear relationship between temperature and photosynthetic rate up to the optimum temperature (20°C in May and 30°C in September). Maximum photosyn-thesis occurred at salinities between 15 and 30‰ S and decreased to 37% at a salinity of 50‰ S. Increase in temperature (18.7° to 22.6°C in May, 8.2° to 18.3°C in September) correlated with photosynthesis during the first h of the low tide period (in May and September), whereas increased salinity (30 to 50‰ S in May and 30 to 48‰ S in September) and possibly also high pH values (up to pH 9.3) correlated negatively with photosynthetic rate during the last part of the period.