Theses and Dissertations

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Defense Date

9-2010

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

Charles G. Messing

Second Advisor

David S. Gilliam

Third Advisor

Janie Wulff

Abstract

Sponges are major macrofaunal components of coral reef ecosystems, often outnumbering corals in richness, abundance and coverage. Although reefs along southeastern Florida have exhibited substantial deterioration over the last few decades and are currently under intensive scrutiny, most investigations have omitted sponges. This study focuses on reef sponge assemblages along Broward County, Florida, from 2002 through 2006 and examines changes in sponge assemblage composition, areal coverage and abundance over time. The photographic database derives from an ongoing study of stony and soft coral coverage carried out by the Nova Southeastern University (Nova Southeastern University) and includes twenty-five 20 x 2-m transects. Forty images covering 1 m2 each were taken per transect (two rows of 20) via scuba. Sponges were identified and their areal coverage measured in a total of 5,000 images using Coral Point Count with Excel extensions (CPCe) software. Data includes species counts, minimum and maximum coverage by species, transect and year, as well as total and average areal coverage by transect and year. Dominant species include Spirastrella coccinea, Niphates erecta, Amphimedon compressa and encrusting species. Comparisons among transects and years were carried out using Primer software. Stations on the Middle and Outer Reef tracts cluster together separately from those of the inshore Ridge Complex stations in all factors analyzed (areal coverage, composition, abundance). Values for the Ridge Complex stations (plus a single Inner Reef site) are much more variable than those for the Middle and Outer Reefs. Univariate analyses (ANOVA, Linear regressions) of areal coverage,richness and abundance over time reveal no temporal trends with one exception; sponge abundance on Outer Reef stations showed a significant decline over the study period. During 2005, multiple transects were affected by hurricanes Katrina, Wilma and Rita, which damaged or removed some sponges and buried others. The more common species, such as branching species appear to have recovered more rapidly, but species such as Xestospongia muta have survived the storms and maintained both numbers and coverage. Tracking of selected individual sponges in five quadrats over the study period revealed that some species (e.g., Xestospongia muta, Cliona delitrix) remained for the entire period, while some others (e.g., Niphates erecta, N. digitalis, Amphimedon compressa, Iotrochota birotulata) either appeared or disappeared between yearly images, or exhibited substantial growth (Ircinia strobilina).

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