RECOVER MAP 3.4.3.5 Lake Okeechobee Benthic Macroinvertebrates

Benthic macroinvertebrates play an important role in the Lake Okeechobee ecosystem. They provide food resources for fish, contribute to sediment nutrient recycling, and can serve as sensitive indicators of water quality (Jonasson 1969, Brinkhurst 1965, Warren et al. 1995).
Given these overall MAP goals, the evaluation of benthic invertebrate communities of the Lake Okeechobee pelagic region was implemented with the following objectives:
1. Sample Lake Okeechobee sublittoral zone benthic invertebrate communities in three
areally dominant habitat zones (mud, sand, peat) twice annually for a three year period,
duplicating the timing, locations, and methods of Warren et al. (1995).

2. Use results from sampling to evaluate the pelagic region benthic invertebrate
community structure, thereby establishing a baseline for future evaluation and
comparison. Elements of community structure to be documented include: taxonomic
composition, taxa richness, absolute abundance, relative abundance, diversity
(Shannon’s equation, as per Krebs 1999), and evenness (as per Pielou 1977).

3. Compare current (2005-08) pelagic region benthic invertebrate community structure
with corresponding structural elements of the 1987-96 study period. Based upon these
comparisons, identify changes in invertebrate community structure and speculate on
the implications to future invertebrate community health as well as the overall health
of the Lake Okeechobee ecosystem.

4. Relate results from the study to CERP hypotheses and apply conclusions to the
adaptive management process.

The intent of maintaining continuity with the methods and sampling sites utilized during the 1987-1996 FWC sublittoral zone evaluation (Warren 1991, Warren et al. 1995) was to supplement the pre-CERP implementation baseline (2005-2008 study) with additional data collected over a longer term and over a broader range of environmental conditions.

Benthic macroinvertebrate communities of the Lake Okeechobee pelagic zone were sampled by the Florida Fish and Wildlife Conservation Commission (FWC) on a quarterly (February, May, August, November) basis in 1987-1988 and then semi-annually (January and July) through 1996. Since 1996, invertebrate communities have been sampled intermittenly, with the last collection occurring in June 2000. Sampling was conducted at 18 fixed sites, with six sites each in mud (northern and mid-lake), sand (western), and peat (southern) habitat zones. Three pseudo-replicate samples were collected at each of the 18 sites during every sampling event, yielding 18 samples per habitat zone and a total of 54 samples. Samples were collected with a petite ponar dredge.