11th ICRS Abstract book - Nova Southeastern University

1.3
Environmental Effects On Back-Reef Sponge Distribution in The Florida Keys
(Usa)
Jeremy WEISZ* 1 , Mark BUTLER IV 1
1 Dept. of Biological Sciences, Old Dominion University, Norfolk, VA
Sponges are an abundant and conspicuous feature of back-reef hard-bottom environments
in the Florida Keys (USA), where they often dominate the sessile animal biomass,
provide shelter to other animals, and significantly alter planktonic communities and
biogeochemical cycles through their filtering activities. Although predation and
competition influence sponge community structure on coral reefs, these interactions
cannot explain the distribution of sponges found in Florida’s back-reef environments.
Environmental conditions in these habitats are influenced by water management
strategies in the freshwater marshes of the Everglades, climatic conditions (e.g.,
temperature, rainfall, wind), and coastal oceanography. As a consequence, salinity,
nutrients, and plankton concentrations all vary dramatically. We therefore examined the
implications of water quality on back-reef sponge community structure in two ways.
First, in laboratory experiments we tested the tolerance of five prominent sponge species
to salinities ranging from 15 psu to 45 psu during summer and winter temperatures. We
then compared data on sponge distributions at 32 sites throughout the Florida Keys with
water quality data from a water quality monitoring network (SERC) using canonical
correspondence analysis (CCA). The mesocosm experiments showed that the golfball
sponge, Cinachyra sp., tolerated the full range of salinities, whereas the other four
species died at salinities above and below 35 psu at summer temperatures, and most died
at salinities < 30 psu at winter temperatures. The CCA showed that some species, such
as Ircinia variablis and Cinachyra sp., are “weedy” species, able to grow in most
habitats, whereas others, such as Spongia graminea and Spongia barbara, are less
tolerant of variable salinities and nutrient concentrations. These analyses suggest that
local and global environmental changes will significantly impact the species distribution
of sponges, with potentially drastic impacts on reef and other nearshore benthic
communities in the Florida Keys.
1.4
Classifying Coralline Rubble Beaches in The British Virgin Islands
Shannon GORE* 1 , J. A. G. COOPER 2
1 Conservation & Fisheries, Government of the British Virgin Islands, Cruz Bay, Virgin
Islands (U.S.), 2 School of Environmental Sciences, University of Ulster, Coleraine,
United Kingdom
More than 100 beaches in the British Virgin Islands (BVI) are composed of coarse coral
reef rubble (coralline rubble). Descriptions of similar beaches elsewhere in the Caribbean
and Pacific focus on their deposition during storm or tsunami events in which coralline
rubble is transported onshore to create ridges, and over time, ridge complexes.
Observations in the BVI indicate that coralline rubble beaches occur in a variety of
settings and vary in morphology and composition. In this paper a preliminary
classification scheme is presented based on the attributes of 50 coralline rubble beaches
in the BVI.
Methods involved mapping the distribution of coralline rubble beaches throughout the
BVI and as describing the following six factors that potentially influence the morphology
of these beaches: 1) Clast size of coral debris (smaller Porites ssp. vs. larger Diplora ssp.
and A palmata); 2) Orientation of the beach to offshore reef types (fringing, patch,
barrier); 3) Offshore bathymetry (steep beachface vs. carbonate platform); 4) Prevailing
wave approach direction (onshore vs. longshore); 5) Amount of accommodation space
available (behind and adjacent to the beach)); 6) type of barrier (single, prograded,
overwash, etc). Multivariate statistics were then used to classify each beach and
determine the importance of each of the variables on coralline rubble beach form.
Poster Mini-Symposium 1: Lessons from the Past
1.5
Results Of Long-Term Bioersion Study, Belize Patch Reefs
Halard LESCINSKY* 1 , Maxwell HILL 1 , Ann HOEDT 1
1 Life and Earth Sciences, Otterbein College, Westerville, OH
Bioerosion rates of branching corals were tracked for up to 8 years on patch reefs in central
Belize using natural and experimental substrates. Bleaching induced mortality in 1998
provided the start of a natural experiment in which Acropora cervicornis and Agaricia
tenuifolia skeletons were collected at 1-2 year intervals for 8 years. In addition, experimental
substrates (conch shells) deployed along a depth gradient (1-15m) were retrieved at 1, 3, and 5
year intervals. Macroboring bioerosion rates were initially highly linear (8%/yr), and inversely
related to depth. After 3 years macroboring bioerosion slowed and all substrates tended
towards a maximum bioerosion intensity of approximately 35%. This threshold value may
reflect the maximum gallery density for Cliona or the collapse and disappearance of more
highly bored substrates. Over the same intervals, substrates were widely encrusted by coralline
algae and there was little loss of corallite surface topography suggesting that scraping
bioerosion was negligible on branching corals and rubble. These results highlight the
importance of boring over grazing for some reef habitats, and for some types of substrates.
While previous studies, primarily in the Pacific, have proposed that grazing bioerosion is
generally an order of magnitude or more greater than macroboring, this is probably not the case
for branching corals and carbonate rubble, two of the most rapidly produced substrates on the
reef. It is also possible that Caribbean bioerosion differs significantly from Pacific bioerosion
because of the loss of grazing Diadema, and the absence of the deepest excavating parrotfish.
1.6
Reef Sedimentation Patterns, Southwestern Shelf of Puerto Rico
Raquel HERNANDEZ* 1 , Clark SHERMAN 1 , Ernesto WEIL 1
1 University of Puerto Rico at Mayaguez, Lajas, Puerto Rico
Effects of terrigenous sedimentation are considered a serious threat to Puerto Rico’s coral reefs.
This study assesses: 1) the composition of sediments accumulating at reef sites; 2) the spatial
extent to which terrigenous materials are reaching the reefs off of La Parguera’s coast; 3) the
spatial variability of sediment composition, size and sedimentation rates at La Parguera; and 4)
the temporal variability of sediment composition, size and sedimentation rates at La Parguera.
Sediment traps were deployed at 9 sites from inner shelf to shelf edge. Mineralogy was
determined by X-Ray diffraction. Bulk carbon composition was determined by carbon
coulometry, specifying: relative weight percent calcium carbonate (in situ production), relative
weight percent organic material, and relative weight percent other material. Environmental
factors influencing sedimentation are addressed, such as precipitation, wind speed, and passage
of tropical storms.
X-ray diffraction analyses indicate that sediments consist primarily of magnesian calcite and
aragonite, both produced in situ, as well as smaller quantities of clay minerals and quartz, i.e.
terrigenous origin. Analyses of total sediment weight (April 2006 - April 2007) show a similar
temporal pattern at all sites where June, July and August have the highest sedimentation rates.
Carbon composition analyses indicate a consistently higher percentage of terrigenous material
in the fine fraction (