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Thesis - NSU Access Only
M.S. Marine Biology
Richard E. Dodge
High latitude reef communities consisting of typical Caribbean fauna of variable composition and density exist on four parallel ridges at varying depths along the Broward County (FL, USA) coast. At least two of these ridges, at 7-13m and 15-30m depth, are drowned early Holocene coral reefs of 5 ky and 7 ky uncorrected radiocarbon age, respectively. Previous work has shown that the present reef communities growing on these ridges can be detected and mapped using acoustic remote sensing and has suggested that different benthic assemblages may exist between each of these reefs. In this study, in situ community data was taken in four corridors on each reef using fifty-meter line-intercept transects. Multidimensional scaling analyses of the in situ community data show distinct differences in benthic community structure across several spatial gradients within the county. This clustering agrees well with an acoustic data set, taken in the same four corridors along the Broward County coast. Analysis of diversity statistics revealed that whereas species diversity (H’) was consistent throughout the county, species richness (d) and eveness (J’) increased along a north-south gradient. Total scleractinian cover was generally low in all areas (<6% mean cover), and also increased along a north-south gradient in the reef communities closest to shore (ridge complex communities). Percent scleractinian coral cover on all other reef communities (inner, middle, and outer reefs) was consistent throughout the county with Montastrea cavernosa being dominant over the M. annularis complex, which is the more typically dominant reef builder in Caribbean systems. Notably absent from the scleractinian fauna of this area was the major Caribbean reef-builder Acropora palmata. A rich alcyonacean fauna (12 genera) was present on all reefs in the county, and typically was the faunal group with highest cover (~20% mean cover countywide) and most important in terms of determining community structure. Although 2-year average water temperature never fell below 21 degrees C, which is within generally accepted limits for reef building, scleractinia were small in size and though not directly investigated, no observable evidence for late Holocene reef building exists. Habitat maps produced from this study show evidence for the unevenly distributed existence of at least six different community types within Broward County: Type 1: shallow, sponge-dominated community; Type 2: shallow, stony- and soft coral-dominated community; Type 3: shallow, zoanthid and soft coral-dominated community; Type 4: soft coral-dominated community; Type 5: zoanthid and macroalgae-dominated community; Type 6: Macroalgae, massive sponge, and soft coral-dominated community.
Ryan P. Moyer. 2003. Macrobenthic Spatial Patterns and Community Structure on the Broward County, Florida (USA) Reefs.. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, Oceanographic Center. (288)