Changes in the distribution and density of Florida Bay macrophytes: 1995-2004

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
J. Brooke Landry (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Michael Durako

Abstract: Benthic macrophyte cover and distribution data have been collected in ten basins within Florida Bay since 1995 as part of the Florida Bay Fisheries Habitat Assessment Program (FHAP). A weighted average for the most prevalent macrophytes during each sampling event since spring 1995 was calculated. Results indicate that the three most common seagrasses observed in Florida Bay, Thalassia testudinum, Halodule wrightii, and Syringodium filiforme, have increased in distribution since 1995. Halodule wrightii and Syringodium filiforme exhibited an increase in both frequency and cover at the bay-scale, an occurrence driven by their dramatic increases in the western-most FHAP study basins: Johnson and Rabbit Key Basins. Acetabularia, Batophora, Halimeda, and Penicillus also exhibited increases in both frequency and cover since spring 1995. The drift Rhodophytes increased in density and distribution between spring 1995 and spring 1998, but did not increase further after that time. Batophora proved to be the most ubiquitous macroalgae throughout Florida Bay and Acetabularia and the drift Rhodophytes showed the strongest seasonal fluctuations, as they were both much more abundant and widespread during spring samplings. Spearman rank order correlation analysis of the Braun-Blanquet cover data showed that Thalassia was generally negatively correlated to all other macrophytes, while Halodule, Halophila, and Syringodium were positively correlated to one another on most occasions. These seagrasses fluctuated between positive and negative correlations with the macroalgae, and as a group, the macroalgae were positively correlated with one another on most occasions, although exceptions did apply. Non-metric multidimensional scaling was used to create ordination plots of the ~ 315 sample stations. Density overlays were used in conjunction with these ordination plots, and together these showed that total seagrass cover and total macroalgal cover were generally mutually exclusive. Spearman rank order correlation analysis was further used to determine if this spatial separation of the two macrophyte groups was statistically significant at the bay-scale, and it was found that 11 of the 18 bi-annual sampling events yielded a statistically significant negative correlation between total seagrass cover and total macroalgae cover. Canonical Correspondence Analysis (CCA) was used to determine which, if any, of the environmental/physical variables, collected as part of the FHAP data set, had a significant effect on macrophyte distribution within Florida Bay. Significance of these effects was determined using Monte Carlo Permutation Tests. CCA showed that depth and visibility were the initial driving forces in macrophyte distribution. During fall 2000, however, a spike in salinity was observed and by spring 2001 this became the most significant variable affecting macrophyte distribution, and it remained so, along with depth, throughout the duration of FHAP.

Additional Information

Publication
Thesis
A Thesis submitted to the University of North Carolina Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Aquatic biology--Florida--Florida Bay, Aquatic plants--Florida--Florida Bay, Seagrasses--Florida--Florida Bay--Geographical distribution
Subjects
Aquatic biology -- Florida -- Florida Bay
Aquatic plants -- Florida -- Florida Bay
Seagrasses -- Florida -- Florida Bay -- Geographical distribution