In the U.S., the situation mirrors that of the rest of the world. People utilize coastal regions for many reasons--food, transportation, living space, recreation, and waste disposal, just to name a few. In many instances, their utilization has generated pressures so great that the dynamics of particular coastal regions have actually been altered. For example, many regions have seen living resource production severely impacted not just by overfishing but also by activities such as agriculture or construction and development. Still, the key issue is not that the coastal dynamics have been modified; the question is whether or not the modification leads to a state which is both stable and ecologically desirable.
For instance, imagine that a coastal region is covered by a mangrove forest. A forest such as this is believed to provide a rich environment for the nurture and growth of marine organisms. In fact, estimates suggest that as much as three quarters of harvestable living marine resources depend on coastal and estuarine areas in one way or another. For some people, this state provides commercial, recreational, and (perhaps) aesthetic value. Now suppose that the mangrove forest is replaced by a high-rise development. For different people, this new state provides commercial, recreational, and (perhaps) aesthetic value. Both states may be equally stable and each state is desirable to some, but conflict is inevitable.
These conflicting demands must be resolved in a manner that optimizes the value of the coastal regions for all. However, a balance can only be achieved if the processes that operate within the coastal system are thoroughly understood. AOML is involved in five programs whose goals are to increase the understanding of the workings of coastal regions in the United States: South Florida Ecosystem Restoration Prediction and Modeling, South Atlantic Bight Recruitment Experiment, Nutrient Enhanced Coastal Ocean Productivity, Southeast Florida Outfalls Experiments, and Port of Miami Dredging Disposal Project. The first three focus on direct impacts to living marine resources, while the last two address the discharge of material into the coastal ocean.
South Florida Ecosystem Restoration Prediction and Modeling conducts research on Florida Bay which is a triangularly shaped body of water covering about 2200 km2. Almost all of the Bay lies within either the Everglades National Park or the Florida Keys National Marine Sanctuary. More than 200 small islands or "keys" occur in the Bay, many of which are rimmed with mangroves and have interior, irregularly flooded, "flats" with calcareous blue-green algal mats. The Bay is generally shallow but there are numerous relatively deeper water basins or "lakes." The Bay is often excessively salty, and it has been characterized by clear waters until recently. Lush seagrass meadows cover a mosaic of shallow water banks. Hardbottom habitats in southwestern Florida Bay support sponge and hard and soft coral communities. Florida Bay is a principal inshore nursery for the offshore Tortugas pink shrimp fishery; it also provides critical habitat for juvenile spiny lobster, stone crab, and commercially important finfish species. The Bay is not only the site of an extensive sportfishery, it is also important as a nursery area for many recreationally important finfish in the Florida Keys National Marine Sanctuary. The Bay supports numerous protected species including the bottlenosed dolphin, several species of sea turtles, manatees, and the American crocodile.
There are many indications that the environmental health of Florida Bay has deteriorated. Seagrass dieoffs have been widely publicized. Declining catches of many commercial and recreational species suggest a decline in recruitment. In the last few years, unusual phytoplankton blooms have been reported across much of the western Bay and into the Florida Keys. These blooms are believed to contribute to the dieoff of loggerhead sponge, thereby impacting spiny lobster recruitment. Most recently, the deterioration of mangroves, interior to and along the edge of mangrove islands within the Bay, has been reported. While the causes of the various problems and the relationships between them are not well understood, there is no question that, like the sawgrass habitat of the Everglades, the Florida Bay coastal marine ecosystem is at risk.
Since 1994, AOML has guided and contributed to a multi-agency investigation of the scientific issues associated with the environmental problems of Florida Bay. Biological, physical, geochemical, and meteorological studies are underway. These include:
SABRE (South Atlantic Bight Recruitment Experiment) seeks to understand the processes governing recruitment variability in populations of Atlantic menhaden. Atlantic menhaden is the most abundant and economically important finfish in the South Atlantic Bight. It is also the primary forage base for many game fishes in the region. Although it has been the subject of considerable study, still information about the impact of environmental variability upon the success of this estuarine-dependent species is lacking. Its life history is typical of many commercially important fish along the U.S. east and Gulf coasts and is divided into distinct phases: offshore spawning, onshore transport, inlet ingress, estuarine development, inlet egress, and migration. Since these phases are geographically as well as temporally separated, the birthdate distribution of survivors can be used to pinpoint the phases most critical to recruitment success.
AOML investigators have been centrally involved with SABRE since its inception in 1991. A collaboration with University of California at San Diego and Bedford Institute of Oceanography has developed a semi-automated continuous sampling system. This system is being used on the outer continental shelf of the South Atlantic Bight to conduct routine egg surveys during the winter spawning. For the first time ever, the detection of egg concentrations has identified the precise sites of spawning activity. The sites, which appear to recur just south of the Cape Lookout shoals, have been observed in three successive sampling years.
NECOP (Nutrient Enhanced Coastal Ocean Productivity), a program beginning in 1990 and concluding in 1996, concentrated on understanding the effects of excess nutrients delivered to the coastal ocean by runoff from the Mississippi River drainage basin. This basin drains about 41% of the continental U.S. Excess nutrients have been implicated as a primary factor in the degradation of coastal waters because nutrient loadings from land-based anthropogenic pollution sources can greatly enhance primary productivity. On the Louisiana inner shelf, retrospective analyses conducted by AOML, in collaboration with the University of Miami and Florida Institute of Technology, have linked nutrient enhanced primary productivity to the subsequent development of seasonal hypoxic conditions in bottom waters on the inner shelf. AOML and the Louisiana Universities Marine Consortium also discovered that, due to zooplankton grazing on primary production and nutrient recycling, hypoxia occurs downstream from the sites of nutrient input.
The central goal of NECOP was to develop the capability to predict the impact that nutrient control strategies may have on the productivity of the shelf, and to determine the probability of coastal hypoxia development. Many of the scientific investigations directed toward this goal were reported in
SEFLOE (Southeast Florida Outfall Experiment) involves AOML with six municipal sewage treatment plants in southeast Florida. Every day, these plants collectively discharge hundreds of millions of gallons of treated sewage effluent into regions approximately a mile offshore--nearby the Florida Current. Until the beginning of SEFLOE in 1988, little was known about the initial dilution and mixing characteristics of the discharged wastewater. This dearth of scientific and practical knowledge created conflicts between those who wrote regulations (both state and federal) and those who must abide by them (municipal utilities). To allay this lack, a multi-year program to measure chemical, biological, and physical oceanographic data was initiated. The central result showed that worst-case dilution and mixing conditions occur when the Florida Current is not present at the effluent sites. The data from SEFLOE are now being used as the factual basis for the formation of efficient operating procedures and effective regulations for discharge. The
Another study, (The Port of Miami Dredging Project), concerns the disposal of dredged material in the coastal zone. This material originates from a major expansion of the Port of Miami. Every day, approximately 20,000 cubic yards of material are generated and must be transported to the designated disposal site a few miles off the coast and within a mile of an extensive coral reef--a reef which is under both state and federal jurisdiction. AOML, in conjunction with the Rosenstiel School of the University of Miami, has designed and built a system that allows oceanographic conditions at the disposal site to be monitored in near-real-time. These observations facilitate decisions to allow discharge only under conditions which permit no dredged material to reach the reef. Discharge is permitted whenever the westerly component of current is less than 12 cm/sec; this threshold was agreed upon by the U.S. Army Corps of Engineers, the U.S. Environmental Protection Agency, and the Florida Department of Environmental Protection in consultation with AOML and the Rosenstiel School. The method may well serve as a nation-wide prototype for many port dredging projects in the future.
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