WATER COLUMN PRODUCTIVITY ATTRIBUTABLE TO DISPLACED BENTHIC DIATOMS IN WELL-MIXED SHALLOW ESTUARIES

We attempted to determine the extent to which benthic diatoms contribute to water column primary productivity in shallow-water estuaries and to elucidate the primary mechanisms responsible for suspending the diatoms. A perliminary study conducted in Mugu Lagoon, California indicated that productivity of ocean water entering the lagoon during flood tides was often several orders of magnitude less than that of the same water mass about 3 h later. Benthic pennate diatoms displaced from the sediments into the water column accounted for the increase. A more detailed study was conducted in Barataria Estuary, Louisiana where, for one month, daily measurements were made of benthic and water column productivity and several other environmental variables. During the month, the relationship between water column and benthic primary productivity varied from strongly negative to weakly negative to positive. K-systems analysis indicated that factors comprised of wave height, meteorological tides, astronomical tides, and benthic productivity and standing crop accounted for the full range of variation in water column productivity. Benthic pennate diatoms, represented an average of 74% of the diatom taxa in water column samples. We conclude that the primary productivity of well-mixed shallow estuarine waters is often greatly aumented by displaced benthic algae.