Marine & Environmental Sciences Faculty Reports

Document Type

Report

Publication Date

2002

Abstract

A study has been undertaken to monitor Broward County, Florida (southeast Florida) coral communities, reef fish assemblages and sedimentation rates in relation to possible effects from a proposed extensive beach renourishment (restoration) project. Coral communities and reef fish assemblages will be monitored at a total of 23 stations distributed offshore Broward County. This monitoring effort will characterize and quantify populations of scleractinian (stony) corals, octocorallian (gorgonian) corals, sponges, and reef fishes. In addition, sediment traps located at each station will be sampled and analyzed.

This document reports the data collected during the second year of this project. Coral communities and fish assemblages were monitored at each of the 23 sites between September and October 2001. In addition, sedimentation analysis for the January, March, May, July and September 2001 collections were conducted.

For September/October 2001, mean (± 1 S.D.) stony coral density for the 23 sites was 2.62 ± 1.85 colonies/m2. Mean stony coral coverage was 2.39 ± 3.96%. Mean gorgonian density was 7.91 ± 8.01 colonies/m2 and mean sponge density was 14.09 ± 6.93 colonies/m2. First Reef sites had greater mean stony coral coverage but lower gorgonian and sponge density than Second and Third Reef sites. First Reef coral cover was much lower than the Third Reef when the First reef site, FTL4, was removed from the analysis. FTL4 had much greater stony coral cover than the mean cover for the remaining First Reef sites (19.95% compared to 1.45%). Shannon-Weaver Diversity Indices performed on the overall transect data resulted in values of 1.45 ± 0.53 and 1.72 ± 0.44 for cover and number of species respectively. Overall evenness was 0.77 ± 0.14 for number of species and 0.64 ± 0.21 for cover.

There was no significant difference determined between the January/February 2001 site visit data and the September/October 2001 site visit data for mean stony coral density and cover. Mean octocoral density also did not differ significantly between these site visits, but mean sponge density was significantly less in September/October 2001 than in January/February 2001.

Stony coral density, stony coral coverage, gorgonian density and sponge density data collected from the 18 monitoring sites established in 1997 and visited yearly from 1997 to 1999 were analyzed. No significant difference in yearly mean stony coral density, mean stony coral cover and mean gorgonian density was determined. Mean sponge density did show significant differences with 1998 sponge density greater than 1997.

Trends in fish density were similar to those trends identified within the coral community transects. The greatest density of fishes occurs on the Third Reef followed by the First and Second. A difference in richness was seen amongst the three Reefs with the First Reef having the lowest number of species. The differences noted in abundance, density, and richness between the data collected in January/February 2001 and in September/October 2001 confirm previous reports of temporal differences in the fish assemblage offshore Broward County (Spieler 1998).

The First Reef had a statistically higher rate of sedimentation than both the Second and Third Reefs when data from January-September 2001 were pooled. Pooled site data showed that January 2001 and May 2001 samples had the greatest sedimentation rates. The grain size for sites on the Third Reef was significantly smaller than both the First and Second Reefs. When site data were pooled, January 2001 had a significantly larger mean grain size than the other four sampling intervals in 2001.

Data collected and analyses completed during this monitoring project will be used to help evaluate effects from the proposed beach renourishment project.

Report Number

Technical Report DPEP 02-01

Comments

Prepared for the Broward County Board of County Commissioners - Department of Planning and Environmental Protection - Biological Resources Division

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