11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 19: Biogeochemical Cycles in Coral Reef Environments
19-1
Nutritional Exchange in The Anemonefish/anemone Symbiosis: Photosynthetically-
Fixed Carbon Is Translocated To Host Fish
Ann CLEVELAND* 1 , Alan VERDE 1 , Raymond LEE 2
1 Corning School of Ocean Studies, Maine Maritime Academy, Castine, ME, 2 School of
Biological Sciences, Washington State University, Pullman, WA
The relationship between anemones and anemonefish is an oft-cited and endearing
example of a mutualistic symbiosis. Current research on mutualistic symbioses suggests
these relationships are more commonplace and have greater import at the ecosystem level
on nutrient dynamics and evolutionary processes than previously thought. Our research
examines the flow of nutrients between resident anemonefishes Amphiprion clarkii and
A. perideraion and their host anemone Heteractis crispa; this study provides the first
direct evidence of nutritional transfer from zooxanthellae to resident fish. Specifically
we traced 1) the flow of photosynthetically-fixed carbon from zooxanthellae to resident
fish and 2) the flow of ingested carbon and nitrogen from anemones to resident fish. In
the photosynthetic study, anemones were incubated in seawater with 13CO2; in the
carbon/nnitrogen study, anemones were fed pellets containing both 13C and 15N. After
isotopic exposures, anemones were transferred to individual aquaria equipped with
running seawater and paired with a resident fish. Prior to placing each fish in an
aquarium and at 2, 4, 8, 16, and 24 hr after exposure to labeled anemones, the epidermis
of each fish was wiped with GFC filters; after a 12 d exposure to the labeled anemones,
tissue samples were collected from each fish. Filters and fish tissues were analyzed for
13C and 15N using a mass spectrometer. 13C was detected in the filters at the 2 hr
timepoint and both 13C and 15N were present in fish tissue samples. Although isotopic
label is transferred directly from anemone to fish epidermis via direct contact, the only
mechanism for the fish tissues to accumulate the labels is by ingestion. The data suggest
that fish are directly ingesting zooxanthellae expelled by the anemone and that
photosynthetically-fixed carbon may be an important supplement to anemonefishes.
19-2
Continuous Measurements Of Productivity Over An Algal Reef Flat Using A
Modified Eulerian Approach
James FALTER* 1 , Ryan LOWE 2 , Marlin ATKINSON 1 , Stephen MONISMITH 3 ,
Daniel SCHAR 1
1 Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI, 2 School of
Environmental Systems Engineering, University of Western Australia, Perth, Australia,
3 Civil and Environmental Engineering, Stanford University, Stanford, CA
We made continuous measurements of the flux of dissolved oxygen over an algaldominated
reef flat community on the Kaneohe Bay Barrier Reef, Hawaii as a proxy for
the instantaneous net community production (NP) of organic carbon. Fluxes were
calculated from measurements of dissolved oxygen and current profiles taken from
moored oxygen sensors and acoustic Doppler current profilers (ADCPs) located at points
defining the vertices of a triangular control volume 250 m in length on each side. We
also used conventional Lagrangian methods of estimating NP by following drifters and
dye patches. Comparison with conventional Lagrangian methods of estimating NP were
excellent when tracking water with dye patches, however, the use of surface drogues
over-predicted NP. Continuous measurement of daily integrated Production (P) and
integrated community Respiration (R) reveal that R varies with P on short time scales in
response to changing light conditions; thus indicating the predominance of autotrophic
respiration in this plant-dominated reef community. At seasonal time scales, P and R are
well matched in late fall and winter, however, P:R become significantly greater than 1 in
summer. In addition, light utilization efficiencies were significantly greater in summer
than late fall.
19-3
Nitrogen Dynamics on a Post-bleaching Reef
Glen HOLMES* 1 , Ron JOHNSTONE 1
1 The University of Queensland, St Lucia, Australia
Understanding the dynamics of coral reef nutrients, particularly nitrogen, following a coral
mortality event is imperative for the prediction of further possible changes on the impacted reef
as well as for the identification of potential management interventions. This is particularly
pertinent in view of the continued trend towards the increased frequency and geographic extent
of coral mortality events. This study investigated the dynamics of nitrogen associated with
microbial communities that develop on coral skeletons following bleaching induced mortality
using both the acetylene reduction and isotopic nitrogen techniques. The results show that
nitrogen fixation activity increases dramatically in the initial three months following coral
mortality with fixation rates as much as an order of magnitude higher than those observed on
hard substrate material throughout the study sites. Rates of ethylene conversion up to 705
µmol.m-2.hr-1 were observed on Montastrea faveolata skeletons while nitrogen fixation rates
using 15N of up to 144 µmol N2.m-2.hr-1 were observed on Acropora aspera skeletons. These
rates are higher than previously reported for coral reefs. Nitrogen fixation activity was found to
be influenced by environmental parameters such as nutrient loading and light levels. The
results also suggest that the microbes persisting from the pre-bleached coral may influence the
dynamics of the microbial community developing on the newly dead coral skeletons. The
observed rates of nitrogen fixation following bleaching induced coral mortality may potentially
be sufficient to singularly direct an affected ecosystem towards a phase change from a coral to
algal dominance.
19-4
Nitrogen Fixation in Coral Reef Environments
Beatriz CASARETO* 1,2 , Loic CHARPY 3 , Marie Jose LANGLADE 4 , Yoshimi SUZUKI 1
1 Graduate School of Science and Technology, Shizuoka University, Shizuoka, Japan,
2 Laboratory of Aquatic Science, Tokyo, Japan, 3 IRD, CENTRE D fOCEANOLOGIE DE
MARSEILLE, Marseille, France, 4 IRD CENTRE D fOCEANOLOGIE DE MARSEILLE,
Marseille, France
Coral reefs are sites of high nitrogen fixation activity. Marine cyanobacteria are major
contributors of nitrogen fixation in coral reefs. In coral reefs cyanobacteria can be found in very
diverse environments: in the water column, in the sandy bottom, on coral gravels as endolithic
and epilithic forms, or forming microbial mats. The high diversity of cyanobacteria in coral
reefs shows their adaptative capacity to live in these nutrient limited environments. The purpose
of the present research is to evaluate N2 fixation rates in different environments of the coral
reefs and their contribution to the primary production of the total ecosystem. Two different
fringing coral reef sites were studied: Sesoko at Okinawa, Japan and La Reunion at the Indian
Ocean. N2 fixation and primary production rates were measured using 13C and 15N fixation
techniques. Time series incubations were done in order to asses N2 fixation during the night
(dark period) and day time. Measurements were done in sandy bottom, coral gravels and
cyanobacteria mats. N2 fixation in sandy bottom varied from 2 to 8 µmol N/mg Chl-a with 2.5
to 12% contribution to the primary production. In coral gravels it ranged from 0.5 to 12 µmol
N/mg Chl-a with 6 to 26% contribution to primary production, while in cyanobacteria mats it
varied between 9 to 240 µmol N/mg Chl-a with contributions of 5 to 21% to the primary
production. Differences in N2 fixation rates between daytime and nighttime were found in all
the studied environments. Moreover the presence of both heterocystous possessing and nonheterocystous
possessing cyanobacteria indicates that N2 fixation and primary production were
separated in time (day and night) and space (presence of heterocystous) due to oxygen
sensitivity of the nitrogenase enzyme.
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