Physiological Ecology of Enteromorpha clathrata (Roth) Grev. on a Salt Marsh Mudflat

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Abstract
Each spring a bloom of E. clathrata, a green alga, occurs in Richardson Bay, a small embayment in north San Francisco Bay [California, USA], forming an extensive mat on the mudflat surface. Short-term photosynthetic experiments were conducted using manometric techniques to determine the light intensity, temperature and salinity levels that would provide optimum growth for E. clathrata. Optimal growth conditions were found to be a light intensity of 240 .mu.E [Einsteins] m-2 sec-1 or higher; 30.degree. C; and 10.permill. S [salinity]. Estimated net annual primary production was 270 g C m-2. Maximum biomass occurred in May when light and temperature were at their peak. Light and temperature on the mudflat were influenced by the frequency of daytime low tides. Tidal frequency and light intensity also apparently control the elevation at which E. clathrata is found on mudflats. Light intensity was found to affect the chlorophyll concentration in E. clathrata. Reduction in chlorophyll under high light intensities allowed E. clathrata to become more translucent and avoid the damaging effects caused by high irradiance. Increase in chlorophyll content at low light intensities allowed E. clathrata at the bottom of the algal mat to maximize its photosynthetic rate. Since peak light intensities and the largest frequency of daytime low tides were correlated with the bloom, it may be concluded that this is a light-limited system.
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