Monitoring the effects of an ephemeral macroalgal bloom on water quality and sediment chemistry in a shallow coastal lagoon.
Hardison, Amber*,1, Anderson, Iris1, Canuel, Elizabeth1, 1 Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA, USA
ABSTRACT- Shallow coastal bay ecosystems such as those along the Delmarva Peninsula, USA are particularly vulnerable to changes in coastal zone activities that result in accelerated nutrient delivery rates. A major function of coastal bays, facilitated primarily by the benthic autotrophs, is their ability to remove, transform, and retain nutrients, thereby buffering the immediate effects of external nutrient loading. Eutrophication in coastal bays is often accompanied by increased occurrences of bloom-forming macroalgae, often associated with the loss of seagrass and other vascular plants. What is currently unknown is the effect of these blooms on nutrient cycling and retention within these systems. The objective of this work was to determine the seasonal effects of macroalgal blooms on water quality and sediment chemistry in Hog Island Bay, a coastal lagoon located along the Delmarva Peninsula within the Virginia Coastal Reserve, a Long-Term Ecological Research Site. From May through October 2004, monthly monitoring of water and sediment chemistry was performed at locations where macroalgal blooms have previously been observed. In addition, lipid biomarker analyses were used to identify the sources of organic matter to the sediments throughout the monitoring period. Our results suggest that the seasonal variation in macroalgal abundance did correspond to temporal changes in both water column and sediment physiochemical parameters, thus supporting the potential for short-lived macroalgal blooms to affect nutrient cycling dynamics within coastal bays. It is essential that we understand the changes in nutrient cycling that correspond to eutrophication-induced shifts in ecological structure in order to better describe and predict the consequences of enhanced nutrient loading to these shallow ecosystems.
Key words: macroalgae, coastal lagoon, lipid biomarkers
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