Long-Term Changes in the Sediment Chemistry of a Large Shallow Subtropical Lake

ABSTRACT

Nitrogen (N) and phosphorus (P) content and selected physico-chemical properties of Lake Okeechobee sediments were measured in 1988 and 1998. Based on these measurements, sediments were classified as mud, littoral, peat, sand or rock. Although some minor redistribution has occurred over the previous decade, mud sediments of Lake Okeechobee essentially occupy the same total area. Total surface sediment N and P showed little overall change in the ten-year period. However, lake-wide spatial patterns indicate some localized decreases of total P content in the littoral and northern regions of the lake. Porewater dissolved reactive P showed significant increases at most sites, suggesting that the surface sediments are losing their ability to absorb soluble P. Nutrient management practices in the drainage basin did not lead to decreased levels of N and P in the sediments of the lake.

Key Words:

• phosphorus
• water quality
• internal load
• eutrophication