Recommended Conferences

International Conference on Climate Change Global Warming

Berlin, Germany
Related Subjects
 

Nutrient inputs from the watershed and coastal eutrophication in the Florida Keys

Author(s): Lapointe BE, Clark MW

Abstract

Widespread use of septic tanks in the Florida Keys increase the nutrient concentrations of limestone groundwaters that discharge into shallow nearshore waters, resulting in coastal eutrophication. This study characterizes watershed nutrient inputs, transformations, and effects along a land-sea gradient stratified into four ecosystems that occur with increasing distance from land: manmade canal systems (receiving waters of nutrient inputs), seagrass meadows, patch reefs, and offshore bank reefs. Soluble reactive phosphorus (SRP), the primary limiting nutrient, was significantly elevated in canal systems compared to the other ecosystems, while dissolved inorganic nitrogen (DIN; NH4 + and NO3 −) a secondary limiting nutrient, was elevated both in canal systems and seagrass meadows. SRP and NH4 + concentrations decreased to low concentrations within approximately 1 km and 3 km from land, respectively. DIN and SRP accounted for their greatest contribution (up to 30%) of total N and P pools in canals, compared to dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) that dominated (up to 68%) the total N and P pools at the offshore bank reefs. Particulate N and P fractions were also elevated (up to 48%) in canals and nearshore seagrass meadows, indicating rapid biological uptake of DIN and SRP into organic particles. Chlorophylla and turbidity were also elevated in canal systems and seagrass meadows; chlorophylla was maximal during summer when maximum watershed nutrient input occurs, whereas turbidity was maximal during winter due to seasonally maximum wind conditions and sediment resuspension. DO was negatively correlated with NH4 + and SRP; hypoxia (DO<2.5 mg l−1) frequently occurred in nutrient-enriched canal systems and seagrass meadows, especially during the warm summer months. These findings correlate with recent (<5 years) observations of increasing algal blooms, seagrass epiphytization and die-off, and loss of coral cover on patch and bank reef ecosystems, suggesting that nearshore waters of the Florida Keys have entered a stage of critical eutrophication.

Similar Articles

Connectivity of marine populations: Open or Closed? Science 287: 857-859

Author(s): Cowen RK, Lwiza K, Sponaugle S, Paris C, Olson D

Ecotoxicology of tropical marine ecosystems

Author(s): Peters EC, Gassman NJ, Firman JC, Richmond RH, Power EA

Review of agricultural pollution in the Caribbean with particular emphasis on small island developing states

Author(s): Rawlins BG, Ferguson AJ, Chilton PJ, Arthurton RS, Rees JG

A flow-through system for exposure of seagrass to pollutants

Author(s): Walsh GE, Hansen DL, Lawrence DA

Effect of pesticides on photosynthetic and respiration of marine macrophytes

Author(s): Ramachandran S, Rajendran N, Nandakumar R, Venugopalan VK