http://www.everglades.org/articles/special-report-pg1.html
University of Miami.
Florida Bay and the Florida Keys are at the downstream end of the Kissimmee River-Lake Okeechobee-Everglades watershed. Their ecological health depends on what happens upstream. Within the past 20 years, a number of ecological changes have occurred in South Florida coastal waters. In Florida Bay, large algal blooms have developed and persisted, large areas of seagrass and sponges have died off, and major changes have occurred in fish populations. In the Florida Keys, macroalgae have overgrown many coral reefs, coral diseases appear to be spreading, and many corals have died. Many of these changes are classical indicators of nutrient eutrophication.
The dominant hypothesis for explaining many of the changes, however, is that reduced water flow into Florida Bay from the Everglades led to hypersaline conditions, which then led to massive seagrass dieoff. This hypothesis further proposes that the seagrass dieoff and subsequent organic decomposition and sediment resuspension released nutrients which then generated the algal blooms. This hypothesis has been used as a rationale for pumping more fresh water into Florida Bay as part of a large scale alteration of water management in South Florida. The hypothesis is a reasonable one to begin with, but an examination of the data available leads to serious doubts about the validity of the hypothesis and the predicted ecological consequences of pumping more freshwater into Florida Bay.
CONCLUSIONS:
The dominant hypothesis for explaining many of the ecological changes that have occurred in Florida Bay in the past 2 decades is that reduced flow into Florida Bay from the Everglades led to hypersaline conditions, which then led to massive seagrass die-off. This hypothesis further proposes that the seagrass dieoff and subsequent organic decomposition and sediment resuspension released nutrients which then generated algal blooms. The data, however, show that hypersaline conditions cannot explain either the spatial or temporal distribution of seagrass dieoff in Florida Bay. Furthermore, seagrass dieoff cannot explain the spatial or temporal distribution of nutrients and algal blooms in Florida Bay.
It is hypothesized that the large algal blooms in Florida Bay are the result of nitrogen-rich waters in eastern Florida Bay meeting phosphorus-rich waters in western Florida Bay. Nutrient bioassays confirm that phosphorus is the limiting nutrient in the east and nitrogen is the limiting nutrient in the west, as predicted by the spatial distribution of N:P ratios.
It is hypothesized that much of the P comes from Miocene phosphorite deposits by way of Peace River erosion and subsequent coastal current transport along the southwest coast, and by way of groundwater through phosphorite-rich quartz sand deposits underneath certain areas of the coastal waters. It is argued that this P source has not changed significantly over the past few decades. It appears that much of the N comes from freshwater runoff from agricultural lands through the Everglades. It is argued that changes in water management practices in the past two decades have led to an increase in N inputs to eastern Florida Bay. Mixing of this water from the east with the P-rich water from the west has led to the large algal blooms that have developed in northcentral Florida Bay, altering the entire ecosystem. Some of this enriched water is transported to the middle and lower Florida Keys, where it may be adversely affecting the coral reefs and other oligotrophic ecosystems there.
In conclusion, it is hypothesized that if more freshwater from the Everglades-agricultural system is pumped into Florida Bay, as proposed (United States Army Corps of Engineers and South Florida Water Management District, 1999), the algal blooms will increase and the ecological problems of Florida Bay will get worse, not better. It is also hypothesized that if more passages along the Florida Keys between Florida Bay and the coral reefs are opened up, as proposed, the coral reefs will experience lower water quality.