PARENT SESSION
Session #9: Ecological forecasting - Ecosystem management based on predictive science. Organized by: J. E. Fauth and D. Scavia.
Tuesday, August 7, 2001. Madison Ballroom B
Catastrophic Ecological Decline of Carysfort Reef, Key Largo, Florida 1974-2000.
Dustan, Phillip1, Dobson, Eric1, 1
ABSTRACT- Remote sensing offers the potential to observe the responses of coral reef ecosystems to perturbations on a geographical scale not previously accessible. However, coral reef environments are optically, spatially, and temporally complex environments which present difficult challenges for extracting information concerning the ecology of coral reef communities. This work explores using satellite imagery to detect change in coral reef communities in the Florida Keys. The coral reefs of the Florida Keys are in catastrophic decline from nested multiple stressors including direct and indirect anthropogenic impacts across local to global scales. The Florida Reef Tract is at the downstream end in the hydrology of South Florida and subject to the effects of environmental impacts cascading through multiple ecosystems. Between 1974 and 1982 cover and diversity on Carysfort Reef, Key Largo, increased in the shallow areas of the reef while the deeper, fore-reef terrace suffered significant loss. Coral bleaching events and diseases increased in the mid-1980's and by 1999, coral cover had decreased to below 5% in both shallow and deep deeper habitat zones. Similar ecological degradation has occurred on many reefs throughout the Florida Keys, including Molasses Reef, Looe Key, and Sand Key. Carysfort, however, is the only reef where this long-term change has been documented with quantitative line transect studies. A time series of Landsat Thematic Mapper imagery was assembled from 1982 to 1996 for Key Largo, Florida. We compared the data to known changes in the reef ecosystem of Carysfort Reef and terrestrial sample sites. Changes in image brightness and spectral band ratios were suggestive of shifts from coral-to algal-dominated community structure that have occurred since 1975. An analysis of pixel-scale variation through time, termed temporal texture, revealed that the shallow reef areas are the most variable in regions of the reef that have experienced significant ecological decline.
KEY WORDS: Coral reef , remote sensing, temporal texture, Carysfort Reef