Coastal lagoons are key components of land-ocean fringe ecosystems in view of their ubiquity and the important ecological roles they play, such as the provision of food and shelter for many organisms, the filtration of land-derived nutrients and the prevention of shoreline erosion. On September 16th 2004, Hurricane Ivan, a category 3 storm, landed on the NorthWestern Floridian Peninsula around Pensacola Bay. The storm generated substantial damage, including the loss of human lives and much destruction of houses, roads and water and electrical facilities. Over the past four years, the PIs have been studying extensively the ecology of three coastal lagoons located in the area most affected by the Hurricane. Hence, the passage of the Hurricane through the PIs study sites, in conjunction with the pre-hurricane extensive date set compiled for the sites, sets up an unprecedented natural experiment to examine the impacts of hurricanes on the ecology of these important coastal environments. Indeed, little is known as to how hurricanes may affect coastal lagoons and the important services they offer to the ecosystem, in contrast with the several existing studies of hurricane impacts on coral reefs, estuaries and marsh or mangrove communities.
The focus on coastal lagoons is not the only novel aspect of this proposal. The PIs also expect that Hurricane Ivan will have a rather positive effect on the ecological attributes of coastal lagoons, which would counter the often negative effects that have been reported for estuaries, coral reefs and marsh/mangrove communities. The two arguments invoked to expect positive effects on coastal lagoons are as follows. First, coastal lagoons, in view of their convoluted and protected morphology, frequently have a restricted fetch (i.e. area of open water through which the wind can build up shear on the bottom). Hence, the intensity of shear imposed by the Hurricane on the benthic plants (seagrasses and macroalgae) of a lagoon would be inherently limited by the lagoon morphology and, likely, rather entail a positive effect by pruning old parts and tissues and rejuvenating the plants. Second, coastal lagoons have generally low to moderate flushing rates due to the absence of riverine inputs (as it happens, for instance, in estuaries) and the presence of a rather constrained opening into coastal waters. Thus, the nutrients imported into coastal lagoons from surrounding land as storm-driven flooding recedes would remain in the lagoons long enough for efficient uptake by benthic vegetation. The growth of benthic plants in coastal lagoons is often limited by nutrient availability and, thus, increased nutrient loading in combination with ample opportunity for uptake would represent another positive effect of Hurricane Ivan on those plants. Since benthic plants are the dominant producers in coastal lagoons and key players in the ecology of those environments, we hypothesize that Hurricane Ivan, through stimulating the growth and health of benthic plants, will also promote the ecological attributes of coastal lagoons. In particular the PIs hypothesize that, after the passage of Hurricane Ivan, the coastal lagoons studied will have increased primary production, offer higher and enhanced levels of shelter to organisms (and thus have higher levels of macrofauna in the benthic meadows) and filter and store larger quantities of land-derived nutrients.
The extensive baseline of data obtained for the three lagoons studied over the past four years allows the PIs to unequivocally test their hypotheses by simply comparing the pre-hurricane baseline with corresponding measurements obtained after the Hurricane. The research will provide training opportunities for two graduate students. The Mississippi-Alabama Sea Grant Consortium and the EPA-founded Alabama Center for Estuarine Studies are also supporting this project.
