11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 19: Biogeochemical Cycles in Coral Reef Environments
19.790
Carbonate Gain And Loss: Comparing Carbonate Production With Parrotfish And
Urchin Bioerosion On A Protected Reef In Hawaii
Ling ONG* 1 , Kim HOLLAND 2,3
1 University of Hawaii at Manoa, Honolulu, HI, 2 Hawaii Institute of Marine Biology,
Kaneohe, HI, 3 Hawaii Institute of Marine Biology, Kaneohe
Parrotfishes and urchins can be significant bioeroders and sediment producers on coral
reefs but little has been done to quantify this in Hawaii. Parrotfish and urchins bioerode
the carbonate structure of the reef while grazing, and the ingested carbonate is defecated
as sediment. The 41 ha study site, Hanauma Bay, Oahu, Hawaii is a marine protected
area where harvesting has been prohibited since 1967. The parrotfish and urchin sizes and
densities present are assumed to be natural. Bioerosion rates between parrotfishes and
urchins are compared and the overall grazer (parrotfish and urchins) bioerosion rate is
also examined relative to the gross carbonate production rate for the different reef zones.
Overall, parrotfish bioerosion rates in Hanauma Bay are 4 - 9 times urchin bioerosion
rates in all the examined reef zones. Grazer bioerosion exceeds gross carbonate
production on the reef flat, is nearly equal on the fore reef and significant positive
carbonate accretion only occurs on the reef shelf. Of the four bioeroding parrotfish
species present, over 70% of parrotfish bioerosion is by large individuals (> 45 cm FL) of
just one species, S. rubroviolaceus. The overall parrotfish sediment production rate in
Hanauma Bay (1.36 kg.m-2.yr-1) exceeds the total sediment production rate in
neighboring Kailua Bay (0.9 kg.m-2.yr-1) where parrotfishes are reportedly absent.
Thus, large parrotfish species are potentially ecologically important as bioeroders and
sediment producers on reefs in Hawaii. A slot limit, where parrotfish smaller than the size
at first reproduction and those larger than 45 cm are protected, is suggested as a fisheries
management strategy to preserve biomass and maintain ecological function.
19.791
Macroalgal Tissue Nutrients As Indicators Of Nitrogen And Phosphorus Status in
The Florida Keys
Dennis HANISAK* 1
1 Harbor Branch Oceanographic Institute, Fort Pierce, FL
This study used the tremendous biochemical and ecological diversity of macroalgae to
assess nitrogen and phosphorus availability at a broad, ecosystem-level scale in the
Florida Keys and nearby waters. Spatial variation in tissue nutrients (carbon = C,
nitrogen = N, phosphorus = P) of dominant macroalgae were assessed, both as ratios and
absolute values, along 12 inshore-offshore transects in the Florida Keys and at 10 stations
in nearby Florida Bay. The resulting detailed analysis demonstrated spatial and temporal
patterns in macroalgal tissue nutrients. The transect data revealed no universal inshoreoffshore
patterns in tissue nutrients and no obvious “hotspots” of nutrient enrichment.
Similarly, when data were compared among segments, there was no universal
geographical pattern in tissue nutrients for all species. The most striking result was that
the N and P status of macroalgae in Florida Bay was significantly different than other
locations. Macroalgae collected from Florida Bay generally had higher N and lower P
levels than algae collected elsewhere. The most common inshore-offshore pattern was
higher %N and lower %P availability inshore; however, limited inshore-offshore
differences in N:P ratio suggests that both nutrients were generally readily available in
proportional amounts required by the various species. Most species in this study had
higher %N, and to a lesser extent, higher %P and %C in March than in July. Based on
the published literature on other species of macroalgae, it appears that N and P are
generally available in sufficient quantities that most macroalgal growth is not limited by
either nutrient.
19.792
Diel Nitrogen Dynamics On A Florida Keys Coral Reef: Temporal Variability in Din
Transformations By The Barrel Sponge xestospongia Muta.
Patrick GIBSON* 1 , Christopher MARTENS 1 , Niels LINDQUIST 2 , James HENCH 3 , Howard
MENDLOVITZ 1 , Brian POPP 4 , Joseph BOYER 5
1 Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC,
2 Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC,
3 Environmental Fluid Mechanics Laboratory, Stanford University, Stanford, CA, 4 Department
of Geology and Geophysics, University of Hawaii, Honolulu, HI, 5 Southeast Environmental
Research Center, Florida International University, Miami, FL
The common barrel sponge, Xestospongia muta, is a dominant animal on Florida Keys reefs. X.
muta hosts biogeochemical processes that can drive or mediate changes in ecosystem structure
and function. Fluxes of dissolved inorganic nitrogen (DIN) resulting from X. muta pumping
and respiration were examined with high temporal resolution utilizing the Aquarius underwater
research habitat at Conch Reef off Key Largo during two missions in September and October
2007. Hourly samples of ambient and sponge excurrent water were simultaneously collected by
automated underwater sampling units. Over 300 paired samples were analyzed in order to
quantify the net fluxes of nitrate, nitrite, ammonium, and total DIN. This approach generated
information about the inherent fine scale variability of ambient DIN concentration and
speciation in the surrounding reef environment as well as the effect of sponge biogeochemical
transformations on the nitrogen pool. Initial results suggest the occurrence of significant
temporal variability in net DIN fluxes to the reef water column. Ambient DIN concentrations
increased by an average of ~50% after being pumped through the sponge, however diel
excurrent water DIN concentrations varied by at least five fold. The DIN flux is principally
nitrate as a result of microbial nitrification occurring within X. muta tissues. Variability in the
diel respiration cycle of the barrel sponges could impact the rates and/or mechanisms of N
transformations. Considering the impressive pumping capacity of X. muta and other reef
sponges, temporal changes in the flux of DIN from sponge processing could have important
implications for the nutrient budgets and ecosystem dynamics coral reef ecosystems wherever
sponges are abundant.
19.793
Effect Of Coastal Water Nutrient Enrichment On Macroalgal Communities Over The
Southern Martinique Reef
Helene LEGRAND* 1 , Yann ROUSSEAU 2 , Brian LAPOINTE 3 , Philippe LENFANT 4 , René
GALZIN 4 , Jean-Philippe MARECHAL 2
1 Observatoire du Milieu Marin Martiniquais, FORT DE FRANCE, Martinique, 2 Observatoire
du Milieu Marin Martiniquais, Fort de France, Martinique, 3 Harbor Branch Oceanographic
Institution, Ft Pierce, FL, 4 EPHE - Université Perpignan, Perpignan, France
Coral reefs of Martinique have undergone an excessive growth of macroalgae over the past two
decades, leading to a decrease in coral cover and health status. Increasing urbanization,
agricultural and industrial activities over the South coast of Martinique have raised land-based
nutrients discharges.
In this study we used macrophytes ä15N signatures to point out the influence of anthropogenic
nutrient enrichment on macroalgal communities’ development.
Field experiments were conducted at 10 stations located along the Southern reef of Martinique.
Seven sites were chosen close to anthropogenic nutrient discharges and 3 offshore sites were
selected as reference sites.
Three macroalgae indicator species were collected at each site and two depths to assess spatial
variability among shallow subtidal (5m) and mid-depht (25-30m) waters. Dried tissues were
used for stable nitrogen isotope (ä15N) analysis. Water-column dissolved inorganic nitrogen
(DIN), soluble reactive phosphorus (SRP) and chlorophyll a were measured. The sampling was
performed during the wet and dry season for seasonality changes in N source availability.
We expect that concentrations of dissolved inorganic nitrogen, soluble reactive phosphorus, and
chlorophyll a increase at sites directly impacted by sewage discharges (outfalls, rivers, bays…).
The offshore reference sites should be more nutrient limited than the nearshore ones. We
assume that macroalgae in nearshore waters have elevated ä15N values characteristic of sewage
enrichment and agriculture fertilizers. Furthermore ä15N values are presumed to be
significantly highest over shallow reefs compare to deep water.
These results will suggest that regional-scale agricultural runoff from the mainland as well as
local sewage discharges from urbanization and economic activities are both significant nitrogen
sources supporting eutrophication and macroalgal invasion in coral reef communities.
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