BBG21-01

Room:304

Time:May 27 09:00-09:20

The role of coral mucus in the material cycle in reef ecosystems
NAKAJIMA, Ryota1∗
1

Department of Marine Biodiversity Research, JAMSTEC

It is well known that corals release transparent and mucoid organic matter (coral mucus) to the ambient seawater. This
mucus release is important for various physiological functions of corals such as defense against stress, particle trap and cellular
metabolic regulation. Coral mucus is mainly composed of carbohydrates, proteins and lipids, of which most are dissolved
organic matter and thus utilized by heterotrophic bacteria and incorporated into the microbial loop. A fraction of the mucus, with
its high molecular weight and sticky properties, captures large amounts of particulate organic matter in the seawater, forming
large organic aggregates which are efficiently assimilated into higher trophic levels. Thus, coral mucus is incorporated into reeforganisms in a variety of processes and functions as an important organic energy source in reef systems. This paper reviews some
types of mucus forms, chemical composition and production rates of mucus, and the contribution of mucus to material recycling
and heterotrophs from biogeochemical and ecological perspectives and the possible loss of reef biogeochemical processes andfunctions by ecosystem degradation due to global climate change and anthropogenic impact.
Keywords: Scleractinian corals, mucus, zooxanthellae, bacterial degradation, particle trap, trophic structure

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BBG21-02

Room:304

Time:May 27 09:20-09:35

Reef environmental changes under anthropogenic influences: sediment cores beneath thereclaimed areas of Naha City
FUJITA, Kazuhiko1∗ ; HONGO, Chuki1 ; KAWASAKI, Yuko1 ; MINEI, Shogo1 ; SASAKI, Toru1
1Fac. Sci. Univ. Ryukyus

Coral reef ecosystems are now being threatened by global environmental changes and human impacts. However, it is stillargued that when and how increasing human populations historically affect coral reef ecosystems. This is because limited
studies have been conducted on long-term environmental and ecological changes in coral reefs. In this study, we examined
the geochemistry and micropaleontology of sediment cores drilled from the reclaimed areas of Naha City (Okinawa Prefecture,
Japan), where pristine coral reefs had been reclaimed. 10-m deep cores with a recovery of >90% were obtained from six sites incoastal reclaimed areas of Naha City. In order to determine the timing and impacts of anthropogenic influences (e.g., terrigenous
inputs and human activity), major elements ratio (e.g,, SiO2/CaO) was measured by EDX (XRF), and mineral compositions(quartz/carbonates) were determined by XRD. To reveal long-term reef environmental changes, grain-size compositions, and thetaxonomic composition and abundance of foraminiferal assemblages were analyzed. Results showed that Holocene sedimentswith several meters in thickness cover the Pleistocene limestone (the Ryukyu Group), and are overlain by landfill sediments
and soils. The Holocene cores consist mainly of bioclastic carbonate sand and mud with in situ corals and coral gravels, andincreasingly contain terrigenous siliciclasts in the upper part of cores. Radiocarbon ages of fossil in situ corals and molluscs
indicate that coral reefs developed at least 7-6 ka in offshore areas, and at ca. 5-4 ka in inshore areas, and that some cores
may record historical changes in terrigenous sediment inputs into coral reef environments, starting from periods of Gusuku and
Ryukyu Kingdom.

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BBG21-03

Room:304

Time:May 27 09:35-09:50

Linkage between the declines in Porites coral skeletal growth and a land improvement
project on Ishigaki Island, Japan.
SOWA, Kohki1∗ ; WATANABE, Tsuyoshi2 ; YAMANO, Hiroya3 ; HAYASHI, Seiji3
1

Department of Chemistry, Faculty of Science, Toho University, 2 Faculty of Science, Hokkaido University, 3 National Institutefor Environmental Studies
Recent anthropogenic pollution has adversely impacted the physiology of reef-building corals. However, insufficient empirical
data on the relationship between coral skeletal growth (calcification rate and skeletal density) and the degree of anthropogenic
pollution are available. We conducted an analysis of Porites coral growth (N = 6) in the Shiraho Reef at the mouth of the Todoroki River on Ishigaki Island, Japan, over the 52 years from 1958 to 2009. Declines in calcification and skeletal density withno obvious sign of growth cessation or disease occurred in the 1970s-1980s, which coincided with the start of the public land
improvement project on Ishigaki Island. The median calcification and skeletal density values were lower after the 1970s-1980s
than those before the 1970s-1980s, and these differences were correlated with the degree and type of land use and development.
Thus, the nutrient/sediment loads from the Todoroki River, which were related to the degree and type of land use and development, resulted in decreased calcification and skeletal density in the coral. The coral growth after the 1970s-1980s was not related
to thermal stress. After the 1970s-1980s, the relationship between coral growth and environmental factors changed, which suggested that the coral physiological responses observed in the 1970s-1980s were related to the land improvement project.
Keywords: coral calcification, coral skeletal density, land improvement project

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BBG21-04

Room:304

Time:May 27 09:50-10:05

Local Ocean Acidification Caused by Mariculture Activities in Coastal Areas of Bolinao,
Northwestern Philippine
WATANABE, Atsushi1∗ ; MIYAJIMA, Toshihiro2 ; KURIHARA, Haruko3 ; MCGLONE, Maria lourdes s.d.4 ;HERRERA, Eugene5 ; NADAOKA, Kazuo1
1

Tokyo Institute of Technology, 2 AORI, University of Tokyo, 3 Faculty of Science, University of the Ryukyus, 4 Marine Science
Institute, University of the Philippines-Diliman, 5 College of Engineering, University of the Philippines-Diliman, Philippines
Ocean acidification (OA) due to anthropogenic CO2 emissions is a dominant driver of long-term changes in carbonate chemistry such as pH and pCO2 in the open ocean. However in coastal areas, local and regional drivers interact with the anthropogenic
CO2 emissions and cause complex changes in seawater pH. High productivity in coastal ecosystems itself changes pH. Due toincrease in coastal populations, increasing utilization of coastal areas for mariculture activities can be anticipated and the degradation of environment due to such activities are of concern. However, the relationship between such degradation and local OA
has not been well documented so far. Here we examined possible impacts of extensive mariculture activities and ecosystemproductivity in Bolinao, Northwestern Philippine, on seawater pH and other carbonate parameters.
We conducted temporal, 24-hr measurements of pH, pCO2 , etc. at the aquaculture and reef sites in Bolinao in March 2011 (dryseason) and September 2011 (wet season). The aquaculture site is located in the narrow channel where hundreds of mariculture
structures can be found. The reef site is located in the shallow Seagrass meadow which faces the open ocean. We also conductedspatial measurements of pH, pCO2 , etc. around the same sites in September 2012 (wet season) and March 2013 (dry season).
To see the longer trend, we deployed pH loggers at aquaculture and reef sites in the surface from March 7 to May 21, 2014 (atthe aquaculture site until May 4 because of the sensor breakage) in the dry season and from September 28 to December 6, 2014
in the wet season. In Bolinao area, salinity during dry season is kept at 33 PSU or so and does not differ so much from the open
ocean, while salinity during wet season decreases to 20 PSU or lower in all areas in the surface.
The snapshot measurements showed that at the reef site pH (pCO2 ) was increased (decreased) significantly compared to theoffshore values both in dry and wet seasons, whereas at the aquaculture site pH (pCO2 ) was unchanged or decreased (increased)
depending on the time. The long-term pH data also showed that the aquaculture site had lower pH compared to the offshore level,sometimes reaching as low as 7.5, while the reef site had higher pH sometimes reaching above 8.5 in the daytime. The daily pH
variations at the aquaculture site was typically 0.2-0.3 unit, while those at the reef site was 0.5 or more. From these results, weconclude that the aquaculture site exhibits pronounced OA due to local influence from the mariculture activities, and the reef site
has buffers against OA mainly caused by high primary productivity of seagrasses in the area.
Keywords: Ocean acidification, pH, Mariculture, Seagrass meadow

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BBG21-05

Room:304

Time:May 27 10:05-10:20

Reef-scale modeling system for evaluating and predicting coral responses to future environmental changes
NAKAMURA, Takashi1∗ ; NADAOKA, Kazuo1 ; WATANABE, Atsushi1 ; YAMAMOTO, Takahiro1
1

Tokyo Institute of Technology

Coral reefs exhibit significant spatiotemporal variations in temperature, CO2 system parameters (dissolved inorganic carbon,
total alkalinity, pH, CaCO3 saturation state, etc.), flow field, etc. Therefore it is difficult to regard any coral incubation experiments as those simulating actual environmental conditions, because many experiments are conducted under steady or graduallychanging environmental conditions. Reconstruction of reef environments by numerical hydrodynamic simulations is getting
close to practical use level with the developments in computer simulation technology (e.g., Watanabe et al. 2013). Developmentof a sophisticated coral-response model coupled with a reef-scale hydrodynamic model is an effective approach for evaluating
and predicting reef responses to the changes in various environmental conditions. For this purpose, we recently developed a coral
polyp model (Nakamura et al. 2013), which can well reconstruct the coral responses to ocean acidification, flow conditions andothers. We then incorporated it into a reef-scale model based on a 3D hydrodynamic model (ROMS) following the Carbonate
System Dynamics (CSD) model (Watanabe et al. 2013). The developed model system was applied to the Shiraho fringing reef,
Ishigaki Island, Japan, and it was confirmed that the model system well reconstructed the spatiotemporal variations of the reef
environmental parameters. According to IPCC (2013), pCO2 will reach at ca. 935 µatm and sea-level will rise to ca. 0.45-0.82
cm for late 21st century if we select the RCP8.5 scenario. Therefore we analyzed four different scenarios: (1) present condition,(2) high pCO2 (˜935 µatm) condition, (3) high sea-level condition (63 cm higher than present), and (4) high pCO2 and highsea-level condition. The simulation result of high-pCO2 condition indicated that the coral calcification rate will decrease to ca.
75% from the present condition. When the sea-level will be 63 cm higher than the present condition, the calcification will increase to ca. 107% because both the mass exchange between the corals and their ambient sea water and that between inside andoutside of the reef will be enhanced due to higher flow condition. When both pCO2 increase and sea-level rise will occur, thecalcification rate will decrease to ca. 77%. This rate is lower than the present condition but it keeps higher than the case only withhigh-pCO2 effect. The results imply that comprehensive evaluation of concurrent multiple environmental effects is important for
future predictions.
Keywords: coral polyp model, reef scale, numerical simulation, ocean acidification, sea-level rise

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BBG21-06

Room:304

Time:May 27 10:20-10:40

Deterioration of tropical coastal ecosystems by multiple human impacts: the effects throughseascape connectivity
NAKAOKA, Masahiro1∗
1

Akkeshi Marine Station, Field Science Center for Northern Biosphere, Hokkaido University

Coastal ecosystems in tropical regions consist of major seascapes such as coral reefs, seagrass beds and mangrove, which
occur in mosaic patterns. Diversity and connectivity of these seascapes have great effects on ecosystem functions and servicesof coastal area. The present paper aims to review some important effects of seascape connectivity in tropical coastal areas, basedon our recent studies conducted in Okinawa, Thailand and the Philippines. I also preview how climate changes and other typesof human-induced threats affect coastal ecosystems via changes in connectivity among different components of seascapes, andfinally consider effective conservation and adaptation strategies against degradation of coastal ecosystems.
Interrelationships among different seascape/landscape components have been most investigated on the aspects of material andnutrient flows among these habitats using biogeochemical techniques such as stable isotope analyses. For example, it has been
pointed out that major carbon and nitrogen sources for organisms in seagrass beds and coral reefs often come from mangrove
and/or upper basins. Furthermore, the broad-scale studies comparing several seagrass beds facing different areas of watershedrevealed that biodiversity and ecosystem functions of seagrass beds are highly affected by the amount and patterns of terrestrial
input from river basins.
Another important aspect of seascape connectivity has been highlighted by the studies investigating multiple habitat uses byanimals in coastal areas, especially by large-sized animals such as fish, birds and mammals which are highly mobile. Fish census
survey revealed that major reef fish species which are commercially important generally change their habitats ontogeneticallyfrom mangrove, seagrass beds to coral reefs. In addition, acoustic telemetry studies which continuously monitor behavior oflarge-sized fish showed that they migrate frequently between seagrass beds and coral reefs on a daily basis. Although thesehigher-level consumer contribute relatively low in terms of energy and material flows in coastal ecosystems, they sometimes
changes abundance and diversity of seascape-forming organisms by strong top-down effects. Its quantitative evaluation, however, remain to be conducted in future studies.
Global climate changes and other local human-induced stresses negatively affect ecosystem functions derived by such seascapeconnectivity. The most serious, but less studies problems are the interacting effects of multiple stressors which operate in a synergistic way and cause nonlinear, unpredictable changes in coastal ecosystems. For example, shallow coastal seascapes such as
mangrove and intertidal seagrass beds are heavily affected by the interacting effects of sea level rise and coastal development(constructions of dikes, ports, resort hotels, etc.). Similarly, sea use conversion from mangrove to shrimp ponds leads to loss of
disaster prevention functions of coastal areas, which become more vulnerable to severe disturbance by typhoons intensified withclimate changes.
To solve these problems on multiple, non-linear impacts of human-induced threats, it is primarily important to carry out conservation of coastal areas with healthy combination of seascape components. For example, to set a marine protected area (MPA),
it becomes more effective to place one to include mangrove, seagrass beds and coral reefs in conjugation rather than separately.
For the restoration of lost habitats, arrangement and interactions of different seascape components should also be taken into
account. Poor restoration practices, such as planting mangroves in healthy seagrass beds, should be avoided through consultant
with stakeholders and scientists.

Keywords: coastal ecosystem, seascape, ecosystem connecivity, biodiversity, climate change, human impact

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BBG21-P01

Room:Convention Hall

Time:May 27 18:15-19:30

Diversity index of coral distributions and its relation to physical variables in Amitori Bay,
Iriomote Island, Japan.
SHIMOKAWA, Shinya1∗ ; MUKARAMI, Tomokazu1 ; UKAI, Akiyuki2 ; KOHNO, Hiroyoshi3 ; MIZUTANI, Akira3 ;NAKASE, Kouta2
1

NIED, 2 Penta-Ocean Construction. Co. Ltd., 3 Tokai Univerisity

The relationship between coral distributions and physical variables was investigated in Amitori Bay, Iriomote Island, Japan.
Amitori Bay is located in the northwest region of Iriomote Island, Japan. Broad areas of coral have developed in the bay, and theirlife forms, coverages, sizes, and species vary depending on their locations. In addition, Amitori Bay has no access roads, and thebay perimeter is uninhabited. Thus, this small bay, with its variety of environments and lack of human impact, is considered to
be one of the most suitable areas for studying the relationship between coral distribution and physical variables.
Field observations were conducted to obtain data on coral distributions, sea temperature, sea salinity, wind speed, and river flowrate [Shimokawa et al., 2014]. Ocean and wave model numerical simulations and soil particle tracking analysis were conductedto obtain the spatial and temporal distributions of wave height and the numbers of soil particles with the observed physical data.
Our results showed that the life forms and sizes of corals significantly varied depending on their locations in the bay, because thephysical variables differed significantly among these locations.
From the results of the above observations and simulations, we calculated diversity index of coral distributions and its relation
to physical variables. The diversity index, DI [Shannon, 1948; MacArthur and MacArthur, 1961, Clark & Warwick, 2001, McCune and Grace, 2002] is defined asDI=-∑ ci log2 ci,
where ci is the ratio of i-th type coverage to total coverage. DI is a quantitative measure for the degree in which a dataset
includes different types and is related closely to entropy concept in Thermodynamics. The value of DI increases when both thenumber of types and the evenness increase. For a given number of types, the value of DI is maximized when all types are equallyabundant.
The results show that Averages of diversity index of the coral types at the mouth and inner parts of the bay are lower than
average of the whole region, but average of diversity index at the intermediate part of the bay with the intermediate physicaldisturbances is higher than it. This seems to support the intermediate disturbance hypothesis demonstrated by Connell [1978]
which states species diversity in local area is maximized when environmental disturbances is neither too weak not too strong.
References:
Clarke, K. R. and R. M. Warwick (2001), Changes in marine communities: an approach to statistical analysis and interpretation, 2nd ed., PRIMER-E, Plymouth, pp. 176.
Connell, J. H. (1978), Diversity in Tropical Rain Forests and Coral Reefs, Science, 199, 1302-1310.
MacArthur, R. H. and J. W. MacArthur (1961), On bird species diversity, Ecology, 42, 594-598.
McCune, B. and J. B. Grace. (2002), Analysis of Ecological Communities, MjM Software Design, Oregon, pp.300.
Shannon, C. E. (1948), A mathematical theory of communication. The Bell System Technical Journal, 27, 379-423 and 623656.
Shimokawa S., T. Murakami, A. Ukai, H. Kohno, A. Mizutani and K. Nakase, 2014, Relationship between coral distributions and physical variables in Amitori Bay, Iriomote Island, Japan, J. Geophys. Res.: Oceans, 119, 8336-8356 (doi:
10.1002/2014JC010307).

Keywords: Coral, Diveristy index, Wave height, Soil particle, Intermediate disturbance hypothesis

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BBG21-P02

Room:Convention Hall

Time:May 27 18:15-19:30

Variation in the oxygen isotope ratio of dissolved orthophosphate induced by uptake process by hermatypic corals
FERRERA, Charissa M.1 ; WATANABE, Atsushi1 ; NADAOKA, Kazuo1 ; UMEZAWA, Yu3 ; MORIMOTO, Naoko2 ;NAKAMURA, Takashi1 ; MIYAJIMA, Toshihiro2∗
1

Tokyo Institute of Technology, 2 AORI, University of Tokyo, 3 Faculty of Fisheries, Nagasaki Univ.

The oxygen isotope ratio (δ 18 O) of dissolved orthophosphate (PO4 3− ) has been recognized as a promising tool to evaluate thecontributions of both external sources and internal recycling of phosphorus (P) to the P budget in natural aquatic ecosystems.
However, coexistence of many biological processes that can significantly alter the phosphate δ 18 O (δ 18 Op ) in a given system
often complicates quantitative interpretation of this parameter. To use the information of δ 18 Op effectively in biogeochemical
researches, we have to know both the magnitudes of oxygen isotope effect and the reaction kinetics of major biological processes
that take part in the P cycle of the concerned ecosystem. In this study, we conducted a model incubation experiment using
natural hermatypic corals to evaluate the influence of uptake process of PO4 3− by corals on the δ 18 Op . Live coral samples(Porites cylindrica , Heliopora coerulea , Acropora digitifera ) were collected from coral reefs around Ishigaki Island (Okinawa)
and Bolinao (northern Luzon), acclimatized in incubation aquaria for a few days, and then incubated for 3 to 5 days under natural light conditions with elevated concentrations of NO3 − and PO4 3− . Subsamples of seawater were regularly collected andanalyzed for the concentration and the δ 18 O of PO4 3− . PO4 3− was usually taken up by corals linearly with incubation time,
and the uptake rate apparently depended on temperature. Difference in the uptake rate between coral species was not significant.
The δ 18 Op was initially approx. 3 ‰ lower than the equilibrium value with regard to oxygen-isotope exchange with ambient
seawater. In a few cases, the δ 18 Op remained unchanged during the incubation even though uptake proceeded. In the othercases, however, the δ 18 Op gradually increased with time, and in some cases became even higher than the equilibrium value
at the end of incubation. This observation suggests that kinetic isotope fractionation rather than simple equilibration operated
during the uptake of PO4 3− by corals and influenced the δ 18 Op . The magnitude of isotope effect associated with uptake seemed
to depend on coral species, being the largest with A. digitifera and the smallest with H. coerulea . In natural environments where
the concentration of PO4 3− is much lower than the incubation conditions we used, PO4 3− is presumably turned over much fasterand the δ 18 Op is easily altered by corals and other major primary producers. This fact may limit the advantage of the δ 18 Op as
an indicator of external PO4 3− sources.
Keywords: Phosphate, Isotope effect, Stable isotopes of oxygen, Hermatypic coral, Coastal marine ecosystem

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BBG21-P03

Room:Convention Hall

Time:May 27 18:15-19:30

Holocene sea-level record from a drilled core at land reclamation on reef crest in Okinawa
IslandHONGO, Chuki1∗ ; FUJITA, Kazuhiko1 ; KAWASAKI, Yuko1 ; MINEI, Shogo1 ; SASAKI, Toru1
1

Dept. Physics & Earth Sciences, University of the Ryukyus

Holocene sea level records provide the opportunity to understand reef formation history, mangrove development, and settlement by ancient people. Especially, the mid-Holocene sea-level record is important to accurate forecast coastal response to
sea-level change in the near future because the amplitude of sea-level rise is similar to that of future sea-level rise. However, themagnitude and timing of Holocene sea-level records display great variability, inflecting ice sheet uploading and the redistribution of water masses in the global ocean, and glacio-isostatic and hydro-isostatic effects. Therefore, the local sea-level record
is fundamental to a geological evidence for understanding the above topics. In the present study, we analyzed a drilled coreand five radiocarbon ages at land reclamation on reef crest in Okinawa Island, Ryukyu Islands. Analyses of corals (Isopora
sp. and Goniastrea reriformis ) enable the reconstruction of a sea-level curve because these species are distributed in a shallow
water depth. The Holocene sea-level curve reconstructed based on the drill core data reveals a sea-level rise until ca. 7000 cal.
years BP. A mid-Holocene highstand occurred at 6760 cal. years BP, at a level of 2.7 m above the present mean sea level. The
reconstructed mid-Holocene highstand is characterized by one of highest and oldest records in the Ryukyu Islands. The findingreflects the hydro-isostatic effect in response to size and volume of islands because Okinawa Island is the biggest island in the
Ryukyu Islands.

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