Study of Seagrass Beds at Grand Bay National Estuarine Research Reserve

Author(s): Nica, C.; Cho, H.

Submerged aquatic vegetation (SAV), a unique group of flowering plants that have adapted to live fully underwater, is a valuable resource and indicator of aquatic habitat quality. Coastal SAV beds perform a number of irreplaceable ecological functions in chemical cycling and physical modification of the water column and sediments. They also provide food and shelter for commercial, recreational, and ecologically important organisms. The cumulative effects of alteration of natural habitats and decline in coastal environmental quality are causing a decline of coastal SAV. In Mississippi Sound, seagrass beds have reportedly declined >50% since the 1969 Hurricane Camille. In addition, the more significant declines occurred in stable, climax community seagrasses such as Turtlegrass (Thalassia testudinum K.D. Koenig) and Manateegrass (Syringodium filiforme Kutzing), which have resulted in the increased relative abundance of opportunistic, pioneer species such as Wigeongrass (Ruppia maritime L.) and Shoalgrass (Halodule wrightii Aschers) in estuaries and along barrier islands of the northern Gulf of Mexico. Temporal changes in their distribution and abundance indirectly reflect changes in the habitat quality and environmental health status. In this study we are presenting data on seagrass community dynamics by following patterns of biomass allocation at three sites at Grand Bay National Estuarine Research Reserve (NERR), Mississippi. Other pertinent water quality parameters—turbidity, [chlorophyll a], dissolved color, dissolved oxygen, pH, salinity, temperature, sediment, nutrients, and water level were monitored or obtained from the NERR monitoring data. Total biomass and root to shoot ratio were significantly different among the sites, with species composition (R. maritime dominant or Ruppia-Halodule mixed beds) being the most important explanatory variable. The general seasonal pattern showed that the biomass began to increase in April, and peaked in May-June, then decreased in September as Rupppia senesces. Our results suggest that fresh water regime due to precipitation and predominant wind direction might be one of the environmental factors contributing to the spatial difference.

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Technical Sessions

Session I Sedimentation
Session II Weather/Climate
Session III Coastal Resources
Session IV Surface Water Management
Session V Wetlands
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