374
1
Introduction
Mangrove ecosystems around river mouths or in
inner bay areas play important roles in island and
coral reef ecosystems, forming a bridge for the
transportation of organic materials and nutrients
between terrestrial and/or riverine areas and
coastal ecosystems such as coral reefs, sea grass
beds, and tidal fl ats. Mangroves also contribute to
the maintenance of biological communities in the
coastal zone, as animals in these coastal ecosystems use the organic materials transported from
terrestrial regions via river systems and plants
utilize the nutrients.
“Ecosystem services” is a relatively recent
term, proposed by Ehrlich and Ehrlich in 1981 ,
although the concept of nature’s providing benefi ts
to humans is long standing. The widely accepted
defi nition of “ecosystem services” is the benefi ts
provided by ecosystems to humans. As part of the
current intensive debate about ecosystem services
(e.g., Costanza et al. 1997 ), mangrove ecosystems
have been a topic of discussion. Many papers list
mangrove ecosystem services with information on
their economic valuation (Bennett and Reynolds
1993 ; Tam and Wong 1999 ; Sathirathai and Barbier
2001 ; Gunawardena and Rowen 2005 ; Hussain
and Badola 2008 ; Albert et al. 2012 ; Brander et al.
2012 ). When these services are discussed with reference to those of coral reefs and other ecosystems,
the importance of mangroves must be clarifi ed,
and the integrated management of island and coral
reef ecosystems could be improved by further consideration of ecosystem connectivity.
In the tropical and subtropical regions where
mangrove forests occur, people have traditionally
collected mangrove crabs and other fi shery products and enjoyed leisure activities among mangrove forests. Conversely, mangrove areas
worldwide have been targets for development
activities such as the construction of shrimp
ponds and reclamation. Ecosystem services must
be understood if we are to ensure the sustainable
use of such environments. This paper examines
mangrove ecosystem services in Palau.
2
Study Area and Methods
A case study was conducted in Palau. Babeldaob
Island, the biggest in Palau, is surrounded by
coral reefs, and mangroves are very abundant
around the river mouth area (Fig. 1 ). Mangroves
are found along 80 % of the coastline of the
island, and the remaining 20 % comprises
beaches and reefs. The island has 4,025 ha of
mangroves.
On Babeldaob Island, mangrove forests are
distributed over several hundred meters from riverbanks to inland areas 1 km upstream from estuaries. Along the seafront, Sonneratia alba and
Rhizophora mucronata are common, whereas R.
mucronata and R. apiculata dominate estuarine
regions. Xylocarpus granatum can be observed
farther inland (upstream), and Nypa fruticans can
be found along riverbanks.
To clarify the role of mangroves in the island
coral reef ecosystems of Palau, a reference survey of mangrove ecosystem services was conducted. Then, a study of the distribution of
organic materials around a river mouth area was
made.
Three survey stations, Ngiwal, Ngaremeduu,
and Airai, were selected. At each station, we visited the river area, river mouth area, and coastal
zone in a small boat and collected suspended
materials using 2-liter plastic bottles. The water
was fi ltered through a GF glass fi lter, and the
sediments were rinsed with diluted water, dried,
and weighed. Sediments scooped directly from
the bottom were kept in 200-ml glass bottles.
After the removal of salt, all samples were dried
and weighed. Then, 0.1 N HCl treatment was
applied to obtain information on the CaCO 3 content of each sample.
The organic matter contents of these samples
were measured using a CN analyzer, and stable
isotope analyses were performed using methods
described by Shilla et al. ( 2011 ). In this preliminary report, the results at Ngiwal area, the central
part of east coast of Babeldaob Island (N7°31′50″,
E134°36′42″), are shown (Fig. 1 ).
M. Tsuchiya et al.
1
Introduction
Mangrove ecosystems around river mouths or in
inner bay areas play important roles in island and
coral reef ecosystems, forming a bridge for the
transportation of organic materials and nutrients
between terrestrial and/or riverine areas and
coastal ecosystems such as coral reefs, sea grass
beds, and tidal fl ats. Mangroves also contribute to
the maintenance of biological communities in the
coastal zone, as animals in these coastal ecosystems use the organic materials transported from
terrestrial regions via river systems and plants
utilize the nutrients.
“Ecosystem services” is a relatively recent
term, proposed by Ehrlich and Ehrlich in 1981 ,
although the concept of nature’s providing benefi ts
to humans is long standing. The widely accepted
defi nition of “ecosystem services” is the benefi ts
provided by ecosystems to humans. As part of the
current intensive debate about ecosystem services
(e.g., Costanza et al. 1997 ), mangrove ecosystems
have been a topic of discussion. Many papers list
mangrove ecosystem services with information on
their economic valuation (Bennett and Reynolds
1993 ; Tam and Wong 1999 ; Sathirathai and Barbier
2001 ; Gunawardena and Rowen 2005 ; Hussain
and Badola 2008 ; Albert et al. 2012 ; Brander et al.
2012 ). When these services are discussed with reference to those of coral reefs and other ecosystems,
the importance of mangroves must be clarifi ed,
and the integrated management of island and coral
reef ecosystems could be improved by further consideration of ecosystem connectivity.
In the tropical and subtropical regions where
mangrove forests occur, people have traditionally
collected mangrove crabs and other fi shery products and enjoyed leisure activities among mangrove forests. Conversely, mangrove areas
worldwide have been targets for development
activities such as the construction of shrimp
ponds and reclamation. Ecosystem services must
be understood if we are to ensure the sustainable
use of such environments. This paper examines
mangrove ecosystem services in Palau.
2
Study Area and Methods
A case study was conducted in Palau. Babeldaob
Island, the biggest in Palau, is surrounded by
coral reefs, and mangroves are very abundant
around the river mouth area (Fig. 1 ). Mangroves
are found along 80 % of the coastline of the
island, and the remaining 20 % comprises
beaches and reefs. The island has 4,025 ha of
mangroves.
On Babeldaob Island, mangrove forests are
distributed over several hundred meters from riverbanks to inland areas 1 km upstream from estuaries. Along the seafront, Sonneratia alba and
Rhizophora mucronata are common, whereas R.
mucronata and R. apiculata dominate estuarine
regions. Xylocarpus granatum can be observed
farther inland (upstream), and Nypa fruticans can
be found along riverbanks.
To clarify the role of mangroves in the island
coral reef ecosystems of Palau, a reference survey of mangrove ecosystem services was conducted. Then, a study of the distribution of
organic materials around a river mouth area was
made.
Three survey stations, Ngiwal, Ngaremeduu,
and Airai, were selected. At each station, we visited the river area, river mouth area, and coastal
zone in a small boat and collected suspended
materials using 2-liter plastic bottles. The water
was fi ltered through a GF glass fi lter, and the
sediments were rinsed with diluted water, dried,
and weighed. Sediments scooped directly from
the bottom were kept in 200-ml glass bottles.
After the removal of salt, all samples were dried
and weighed. Then, 0.1 N HCl treatment was
applied to obtain information on the CaCO 3 content of each sample.
The organic matter contents of these samples
were measured using a CN analyzer, and stable
isotope analyses were performed using methods
described by Shilla et al. ( 2011 ). In this preliminary report, the results at Ngiwal area, the central
part of east coast of Babeldaob Island (N7°31′50″,
E134°36′42″), are shown (Fig. 1 ).
M. Tsuchiya et al.