Basic HTML Version
International Journal of Marine Science 2014, Vol.4, No.1, 1-15
http://ijms.sophiapublisher.com
1
Research Article Open Access
The Nutrient and Carbon Dynamics that Mutually Benefit Coral and
Seagrass in Mixed Habitats under the Influence of Groundwater at Bise Coral
Reef, Okinawa, Japan
Tomihiko Higuchi
1,4
, Kimberly K. Takagi
2,5
, Kana Matoba
2
, Syusei Kobayashi
1
, Ryota Tsurumi
1
, Seiji Arakaki
2,6
,
Yoshikatsu Nakano
3
, Hiroyuki Fujimura
1
, Tamotsu Oomori
1
, Makoto Tsuchiya
1
1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
2. Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
3. Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa 905-0227, Japan
4. Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Surugaku, Shizuoka, 422-8529, Japan
5. Department of Marine Science, University of Georgia, 325 Sanford Drive, Athens, Georgia, 30602, USA
6. Amakusa Marine Biological Laboratory, Kyushu University, 2231 Tomioka, Reihoku, Amakusa, Kumamoto 863-2507, Japan
Corresponding author email:
dthiguc@ipc.shizuoka.ac.jp
;
fujimura@sci.u-ryukyu.ac.jp
International Journal of Marine Science, 2014, Vol.4, No.1 doi: 10.5376/ijms.2014.04.0001
Received: 27 Oct., 2013
Accepted: 29 Nov., 2013
Published: 04 Jan., 2014
Copyright
©
2014 Higuchi et al, This is an open access article published under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Higuchi et al, 2014, The Nutrient and Carbon Dynamics that Mutually Benefit Coral and Seagrass in Mixed Habitats under the Influence of Groundwater at
Bise Coral Reef, Okinawa, Japan, International Journal of Marine Science, Vol.4, No.1 1
-
15 (doi: 10.5376/ijms.2014.04.0001)
Abstract
The coral species,
Montipora digitata
and seagrass,
Thalassia hemprichii
, co-inhabit the southern portion of the reef moat
in Bise, Okinawa, Japan. To elucidate the biogeochemical relationship between coral and seagrass in mixed communities of the coral
reef ecosystem, the carbon metabolisms and the inorganic nitrogen flux rates were estimated in various reef habitats. We used benthic
chambers to investigate sandy, seagrass, coral-seagrass mixed communities, coral, and acorn worm habitats. Relatively high
concentrations of nitrate and nitrite ions (NO
x
) were observed in all habitats due to coastal groundwater inflow. The uptake rate
constant of NO
x
was the highest in the coral-seagrass habitat and was significantly different from the rate constant in the seagrass
habitat, indicating that seagrass benefits from co-inhabitation with coral. Dissolution of CaCO
3
was observed in the seagrass and
coral-seagrass communities. This decline in basal coral carbonate substrate may contribute to increased fragmentation and dispersal
of the coral habitat. On a biogeochemical scale, the coral-seagrass relationship benefits the seagrass in terms of NO
x
availability and
benefits the coral in terms of carbonate dissolution, increasing fragmentation, and furthering habitat development.
Keywords
Carbon metabolism; Inorganic nitrogen flux; Coral-seagrass mixed community; Coral reef; Benthic chamber
1 Introduction
The biogeochemical dynamics between coral and
seagrass ecosystems are important components of
ecosystem
management.
Understanding
these
dynamics is especially important
in coastal areas
where increasing populations threaten the economic
services these ecosystems provide. In order to
understand broad-scale ecosystem function, recent
management concerns have addressed the importance
of functional group dynamics (Bellwood et al., 2004).
Naeem (1998) stated that in order for ecosystems to
resist “failure” after a disturbance event, species
richness within functional groups is critical in
maintaining ecosystem stability and reliability. For
example, coral reefs serve as physical buffers for
oceanic currents and waves, creating, over geologic
time, a suitable environment for seagrass beds. In
addition to these physical interactions, there are
several biological and biogeochemical interactions
between these interconnected ecosystems (Moberg
and Folke, 1999). Seagrass beds interrupt freshwater
discharge, are sinks for organic and inorganic
materials as well as pollutants, and can generate an
environment with the appropriate nutrient levels that
promotes the growth of coral reefs (Miyajima et al.,
2001; Umezawa et al., 2002).
If seagrass and coral in mixed habitats establish
mutually symbiotic functional groups, it is possible
that the presence of both can create an ecosystem that
is more resilient to disturbance. However until recently,
research has generally focused on the nutrient and
carbon dynamics within these two ecosystems
separately (Badgely et al. 2006, Grover et al., 2003;
Marbà et al., 2006; Ohde and van Woesik, 1999;
Tenore, 1988), and while few, if any, have addressed