Flow-through Microcosms for Simulation of Marine Ecosystems: Changes in Biota and Oxygen Production of Semi-Tropical Benthic Communities in Response to Nutrient Enrichments

摘要

An experiment was accomplished to determine the effects of elevated levels of dissolved inorganic N and P on semi-tropical marine communities. Two groups of microcosms consisting of unshaded 500-L flow -through tanks colinized by naturally-recruited shallow benthic communities were used. One group of tanks was supplied with seawater. The other tank group received water from eutrophic Kaneohe Bay. Phosphate levels in one tank at HIMB and in two tanks at NOSC were increased by 8 micrograms-at/L above ambient by continuous addition of KH2PO4 solution. Ammonium levels were similarly enriched in one tank at HIMB and in two tanks at NOSC by addition of HN4Cl solution. After two months of nutrient enrichment, fouling panel scrapings form all enriched treatments showed substantial increases in biomass and phytopigment content when compared with controls. At NOSC, algal genera in control microcosms were dominated about equally by blue-green algae and diatoms, whereas blue-green algae and green algae dominated in the PO4 and NH4 treatments, respectively. Mean midday O2 production during the enrichment phase was 46% higher in both NOSe enriched microcosms as compared to controls. Efficient retention of P land elevated post-enrichment biomass seen in the P-enriched microcosms indicates that termination of sewage input into semi-tropical estuaries may not result in rapid alteration of there benthic communities.