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STRESS RESPONSE MODEL FOR THE TROPICAL SEAGRASS THALASSIA TESTUDINUM: THE INTERACTIONS OF LIGHT, TEMPERATURE, SEDIMENTATION AND GEOCHEMISTRY
Citation:
Eldridge, P M., J E. Kaldy, AND A. B. Burd. STRESS RESPONSE MODEL FOR THE TROPICAL SEAGRASS THALASSIA TESTUDINUM: THE INTERACTIONS OF LIGHT, TEMPERATURE, SEDIMENTATION AND GEOCHEMISTRY. ESTUARIES. Estuarine Research Federation, Port Republic, MD, 27(6):923-937, (2004).
Description:
Our modeling objective was to better define the relationship between a tropical seagrass and water-column and sediment stressors (i.e., light, organic and particle sedimentation, sediment nutrients and sulfides). The model was developed and optimized for sediments in Thalassia testudinum seagrass beds of Lower Laguna Madre, Texas, USA and is composed of a plant sub-model and a sediment diagenetic sub-model. Simulations were developed for a natural stressor (harmful algal bloom, Aureoumbra lagunensis) and an anthropogenic stressor (dredging event). The harmful algal bloom (HAB) was of limited duration and the simulations showed no effect of the algal bloom on biomass trends but did suggest that sediment sulfides could inhibit growth if the bloom duration and intensity were greater. To examine this hypothesis we ran a simulation using data collected during a sustained 4 yr bloom in Upper Laguna Madre (ULM). Simulations suggested that light attenuation by the HAB would cause a small reduction in T. testudinum biomass, while input of organic matter from the bloom could promote development of a sediment geochemical environment toxic to T. testudinum leading to a major reduction in biomass. The dredging event resulted in sedimentation of a layer of organically rich material and reduction of canopy light for a period of months. The simulations suggested that the seagrass could have recovered from the effects of light but residual effects of high sulfides in the sediments would make the region uninhabitable for seagrasses for up to 2.5 years. These modeling exercises illustrate that both natural and anthropogenic stressors can result in seagrass losses by radically altering the sedimentary geochemical environment.