11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10.299
Coral Growth Processes And Environmental Conditions Around Okinotorishima
Island, Japan
Nobuo MIKAMI 1 , Michio KITANO* 2 , Hidekazu YAMAMOTO 2 , Toshiyuki TAKAO 2 ,
Akiyoshi NAKAYAMA 1 , Wataru ANDO 3
1 National Research Institute of Fisheries Engineering, Kamisu City, Japan, 2 ECOH
Corporation, Taito-ku, Japan, 3 Fisheries Infrastructure Development Center, Chuuou-ku,
Japan
Okinotorishima is the southernmost island of the Japanese territory, approximately 1,740
kilometers south-southwest of Tokyo. The island consists of a lagoon surrounded by
submerged coral reefs, extending 4km east-west and 1.7km north-south. Regarded as a
good fishing ground, the Fisheries Agency of Japan formulated the projects to increase
coral cover around the island. Commencing in 2005, surveys were conducted on five
occasions on the following: coral distribution, coral growth at 17 fixed survey sites, coral
size distribution, coral recruitment, water quality, water temperature and water flow.
The results of the coral distribution showed that coral cover exceeded 30 % in the central
portion of the lagoon. There is knoll topography around the center. From the analysis of
coral growth, growth rates were confirmed to differ by area, being higher in the central
portion.
As for coral recruitment, many colonies were observed in the west part of the lagoon. The
water quality and water temperature were horizontally homogeneous across the lagoon.
From a 60-day consecutive water flow investigation, we were able to obtain the data both
in calm and stormy (e.g. typhoon) conditions. Water motion was simulated using a
numerical model. Under calm sea conditions, the main flow was dominated by a
southwestwardly flow. Under the typhoon conditions, rapid-flow of water entered the
lagoon from all directions with the passage of the storm.
These results suggested that the coral recruitment on Okinotorishima Island was
governed by the water flow in calm sea conditions. It was also estimated that the growth
of corals was influenced by storm surges during typhoons in addition to the topograpy of
the island.
10.300
Physiological Performance Of Giant Clams (Tridacna Maxima, T. Squamosa, T.
Derasa) in A Recirculation System
Andreas KUNZMANN* 1
1 Center for Tropical Marine Ecology (ZMT), Bremen, Germany
Giant clams are effective filter feeders and at the same time autotrophic due to their
symbiosis with zooxanthellae. While juveniles rely on both heterotrophic and autotrophic
feeding, adult clams depend more on excellent light conditions. Clams also play a
potential role for bio-cleaning as additional water treatment module in a closed
recirculation system and are a highly valuable resource for the international aquarium
trade.
Therefore, the importance of auto- and heterotrophy to growth, survival, zooxanthellae
development and nutrient uptake of juvenile giant clams Tridacna maxima and T.
squamosa was investigated. In addition experiments on the photosynthesis, metabolism
and calcification were performed with 5-8 cm specimens of T. maxima and 10-12 cm
specimens of T. derasa in an intermittent flow-through respiration system. Animals were
reared in a recirculation system under different light conditions and different
concentrations of nutrients. Both particulate organic (Tetraselmis algae) and dissolved
inorganic (ammonia and phosphate) food was given.
Results show that light intensity and spectra have a significant effect on survival and
length or weight increase. Nutrient concentrations only seem to play a role, when clams
are kept in optimum light conditions. In this case fertilization with NH4 and PO4 is more
effective than feeding with algae. However, the concentration of zooxanthellae is only
moderately increasing with increasing nutrient concentration. Moreover photosynthesis,
respiration rates and calcification seem to be linked to light conditions but not to
increasing nutrient concentrations. It is concluded that juvenile clams depend more on
autotrophy to satisfy nutritional requirements. The uptake of nutrients is limited and
needs to be tested with larger clams and a variety of nutrient combinations.
10.301
Effects Of Light Availability On in Situ Juvenile Growth Rates Of The Brooding Coral
favia Fragum in Bermuda
Laura STOPPEL* 1 , Gretchen GOODBODY-GRINGLEY 1,2 , Robert WOOLLACOTT 1
1 Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 2 Bermuda
Institute of Ocean Sciences, St. George's, Bermuda
The scleractinian Favia fragum is found in shallow reef environments throughout the Caribbean
and Western Atlantic Ocean. A hermaphroditic brooder, F. fragum develops larvae internally
and planulates during its reproductive season on a monthly basis coupled to the lunar cycle. F.
fragum adults are often found in semi-protected parts of the reef where light is not always most
abundant. Likewise, larvae of F. fragum tend to preferentially settle on the undersides of
substrates where light may be limiting. Growth of juvenile corals, however, is known to be
affected by light availability. In this study we examined the effects of light availability on the
juvenile growth rates of F. fragum in Bermuda. Newly settled metamorphs were placed under
three shade regimes on an inshore patch reef for 37 days. Due to its symbiosis with
photosynthesizing zooxanthellae we expected higher juvenile growth rates under ambient light
conditions, as this would facilitate the most photosynthesis, with growth rates decreasing as
shade increased. Contrary to this hypothesis however, we found significantly higher juvenile
growth rates under moderate levels of shade than under ambient light or heavy shade
conditions. Heavily shaded treatments also experienced the highest degree of mortality. Our
results suggest that although moderate amounts of shade may promote higher growth rates in
juveniles of this species, there is a threshold of minimal light availability below which coral
growth and survival are adversely affected.
10.302
Zooplankton Abundance Much Higher Near the Surface on the 2 m Deep Back Reef of
Moorea, French Polynesia
Alice ALLDREDGE* 1
1 Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa
Barbara, CA
Zooplankton distribution on a broad, 2 m deep backreef exposed to a unidirectional current year
round was examined in Moorea, French Polynesia. Zooplankton, predominantly copepods and
crustacean larvae, were up to 10 times more abundant at 10-20 cm below the surface then at 100
cm below the surface or near the bottom both day and night. Aggregation near the surface
became detectable within 2 m of the well-mixed trough directly behind the reef crest indicating
that zooplankton behavior, rather than greater consumption of plankton near the bottom by
planktivores, generated the distribution. Laboratory studies of zooplankton exposed to
turbulence around corals in a laboratory tank suggest that the zooplankton were not avoiding
increased turbulence near the bottom. Much higher abundance near the surface during the day
and on full moon nights than on new moon nights, suggests that light may be an important cue
causing zooplankton to swim upward. The horizontal flux of zooplankton, as determined by
drift nets, was 4-5 times higher near the surface and much higher than predicted by the slightly
higher flow rate occurring there. Clearly, reef zooplankton are adapted to avoid the higher
predation pressure expected near the bottom from fish, corals, and other planktivores. But these
results also have important implications for the distribution, growth rates, and sizes of
organisms on shallow reefs. A difference in bottom depth or in the height above the bottom of
only a few tens of centimeters may dramatically affect the quantity of zooplankton food
available to corals and other sessile planktivores. Likewise planktivorous fish foraging only
slightly higher in the water column on shallow reefs may reap disproportionately larger
benefits.
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