Research Report
Seagrass bed as a Carbon Sink in Ranong Biosphere Reserve and Trang-Haad
Chao Mai Marine National Park; an important role of seagrass.
By
Anchana Prathep
2012 MAB Young Scientists Award
Thailand
Submitted to
Man Bioshere (MAB) Program, UNESCO
Prince of Songkla Unviersity, Thailand
Seagrass bed as a carbon sink, an assessment from Thailand
Summary
This is a detailed study of the location and the amount of carbon stored in both
the healthy (80% coverage) and unhealthy habitats (20% coverage) in the seagrass
beds in the Ranong Biosphere Reserve (RBR) and Trang Haad Chao Mai Marine
National Park (HCM). We examined the % carbon content of a rich diversity of
seagrass species, compared the above and below ground plant parts and the carbon
content in the sediments according to the grain sizes > or < 63μm. The results showed
that there were differences between the above and below ground tissues, between
study sites, among species and between coverages (P<0.05). The healthy seagrass bed
had a greater carbon content. The sediment fractions were also different at different
study sites and also those associated with different species (P<0.05). Most sediments
were composed of particles greater than 63μm. The % carbon was greater in the
sediment with particle size less than 63μm. The total amount of carbon stored in live
seagrasses at RBR is estimated to be 6.08 Mg and at HCM, 335.16 Mg. A larger scale
estimate of carbon stored in the seagrass ecosystems in Thailand is needed and could
help guide the conservation and management of this important but understudied
ecosystem.
Introduction
The increase of CO2 from anthropomorphic carbon gas emissions is known to
cause climate change, which greatly influences all aspects of life. Increase in
temperature, acidification in the oceans and unpredictable weather are common
phenomenon associated with climate change. Thus, understanding the carbon cycle
and how much carbon is stored in various ecosystems is very important to help slow
down climate change or global warming.
Recent studies have pointed out that coastal ecosystems such as seagrasses,
mangroves and salt marshes store carbon in a reserve now referred to as “Blue
carbon” (Nellemann et al.2009; Laoffoley and Grimsditch, 2009; Mcleod et al., 2011;
Fourqurean et al, 2012; Pendleton et al., 2012). These ecosystems have potentials for
carbon storage greater than tropical forests. For example, seagrasses store 40 times
greater carbon than the tropical forests, up to 83 gCm-2y-1 (Duarte et al., 2005;
Kennedy and BjÖrk, 2009). The ecosystem services value of seagrass is also high, at
approximately 19,000 USD/ha/year, which is almost 10 times greater than that of the
Seagrass bed as a carbon sink, an assessment from Thailand
tropical forest. Estimates are that seagrasses store as much as 3 times more than the
highly productive coral reef ecosystem (Cotanza et al., l977). Seagrass ecosystems
are closely tied to the livelihoods of local fishermen in developing countries in SE
Asia and Africa, where they are common and abundant. The hotspot of biodiversity of
seagrass is in SE Asia, where a high of 15 species has been recorded (Short et al.,
2007). Thailand has 12 species with now another new record, Halophila major, under
review (Tuntriprapas et al., in submission).
Seagrass beds are a threatened habitat especially in developing countries
where extensive coastal developments of land reclamation for industry or tourism
and aquaculture. Compared to coral reefs or mangroves the understanding and public
awareness of seagrasses is limited (Orth et al., 2006). The decline of seagrass
worldwide is very dramatic with an annual average loss of about 3,370 km2 at a rate
of 27 km2 /year (Waycott et al., 2009). These data represent the situation in the USA,
Europe and Australia, where law enforcement, conservation and public awareness are
maintained better than in developing countries where we can assume there is greater
loss in the other regions of the world.
The Blue Carbon Initiative (www.thebluecarboninitiative.org) is an
international group funded by various conservation agencies, dedicated to a better
understanding of the roles of seagrass, mangroves and salt marshes as carbon sinks.
The studies are ongoing and there is a close association between the scientists and
policy makers. We adopted the idea of “blue carbon” and attempt to estimate the
carbon content in the seagrass beds in Ranong Biosphere Reserve and Trang Haad
Chao Mai Natianal Park in Southern Thailand. We hope that our studies promote
further research and prove the importance of their conservation in Thailand and
surrounding regions.
Materials and Methods
Study sites
The seagrass bed surveys were carried out from February to July 2013 in 1) the
Ranong Biosphere Reserve (RBR) and 2) Trang Haad Chao Mai National Park
(HCM) on the Andaman sea, Southern Thailand (Fig. 1) . The purpose of the project
Seagrass bed as a carbon sink, an assessment from Thailand
was to assess seagrass species diversity and the area of the seagrass beds in relations
to carbon storage. RBR is in a sheltered bay close to a mangrove forest (Fig. 2), while
HCM is in front of a more exposed beach (Fig. 3). The areas of the seagrass beds
were estimated using GPS and the maps indicate the specific sites for the field
surveys.
Figure 1 The Google Earth map of the study area at Ranong Biosphere Reserve
(RBR) and Trang Haad Chao Mai National Park (HCM), located on the Andaman sea,
Indian Ocean
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 2 The seagrass bed associated with the mangrove forest at Ranong Biosphere
Reserve (RBR)
Figure 3 The seagrass bed at Trang Haad Chao Mai National Park (HCM) next to the
sandy beach.
Seagrass bed as a carbon sink, an assessment from Thailand
Plants and sediment collection and analyses
To understand the differences between the healthy (80% coverage) and
unhealthy (20% coverage) seagrass beds, 3 repetitions of random samples were
removed within 20 cm X 20 cm quadrats (Fig. 4).
Figure 4 Assessment of coverage using 20 cm X 20 cm quadrat in a bed with 20%
coverage of Cymodocea serrulata at RBR.
Also, to understand the differences in carbon storage of each species, every
seagrass species was collected. The seagrass plants were then separated out into 4
parts: leaf, sheath, rhizome and root (Fig. 5). Each part was then thoroughly cleaned
and dried at 60 °C until constant weight was obtained, to provide the dry biomass.
The biomass was then divided into 2 groups: the above ground biomass and the below
ground biomass (Fig. 6). Plants were then prepared for % carbon content analyses
using a CHN Analyzer (CHNS-O Analyzer, CE Instruments Flash EA 112 Series,
Thermo Quest, Italy) at Prince of Songkla University Central Equipment Laboratory,
Prince of Songkla University, Thailand.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 5 Plants were separated into 4 parts: leaf, sheath, rhizome and root; and
presented into above and below ground biomass. Th= Thalassia hemprichii,
Ea=Enhalus acoriodes, Cr=Cymodecea rotundata and Ho=Halophila ovalis
Since it was previously reported by Kennedy et al., (2010) that there was a
high percentage of carbon in the sediments, sediment was also collected and sent for
% carbon content examination. Three repetitions of plastic cores 7 cm in diameter
(Fig. 7) of sediment in the healthy and unhealthy seagrass beds were taken from 30
cm depth, packed in plastic bags and brought back to the laboratory. Sediments were
cleaned and dried at 60°C until constant weight was obtained. The sediments were
then sieved using sediment shakers (Retsch A5 200 digit, Germany) to estimate the
grain sizes. Particles were separated according to a series of >2 mm, 1-2 mm, 1-0.25
mm, 0.25-0.5 mm, 125-250 μm, 63-125 μm and <63 μm. They were weighed and the
proportion of each grain size was calculated. Sediments were grouped into 2 size
classes: >63 μm and < 63 μm for further % carbon content analysis (Fig. 8).
To estimate the carbon storage at each study site, the % carbon found from
plants and sediments were used to calculate the seagrass area of each site.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 6. The experimental design of sample collections. All seagrass species were
divided into leaf, sheath, rhizome and root except Halophila ovalis (Ho), which is no
sheath.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 7. The 7 cm diameter plastic core for sediment sampling.
Statistical analyses
Three-way ANOVAs were employed to test of the effects of sites, species and
coverage, on the above and below grounds biomass (g/m2); % elemental carbon
above and below ground; carbon content above and below ground (Mg/ha); sediment
grain sizes and % carbon in the sediment. When necessary, data were transformed to
meet the assumptions of the parametric test. Statistical results were presented based
on the transformed analyses, but for clarity graphical output was based on the
untransformed means. Non-parametric analyses (Kruskal-Wallis) were employed if
data did not meet the assumptions.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 8. The experimental design of sample collections. Sediment particles were
separated using the grain size shakers and grouped later into > 63μm and < 63μm size
classes.
Results
1. Seagrass diversity and the area of the beds
There were differences in species diversity and areas between RBR and
HCM. At RBR the only seagrass species were Cymodocea serrulata and Halodule
uninervis. The seven species found at HCM were Cymodocea rotundata, C. serrulata,
Thalassia hemprichii, Enhalus acoroides, Syringodium isoetifolium, Halodule
uninervis, Halophila ovalis. (Figs. 9-15). The estimated area at RBR was 79 ha and at
HCM 882 ha (Figs.16 and 17).
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 9. Enhalus acoroides (L.f.) Royle, the largest seagrass in the Indo- Pacific
region.
Figure 10. Thalassia hemprichii (Ehrenb.) Asch & Magnus , the second largest
seagrass species in the region, provides habitat and food for sea turtles.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 11. Cymodocea rotundata Asch. & Schweinf., a medium-sized species,
common in the region.
Figure 12. Cymodocea serrulata (R.Br.) Asch. & Magnus, similar to C. rotundata but
with serrated tips on the leaves.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 13. Syringodium isoetifolium (Asch.) Dandy, the only cylindrical leaved
species in this region, commonly found at the lower intertidal to subtidal regions.
Figure 14. Halodule uninervis (Forssk.) Boiss, mostly found at lower intertidal to
subtidal.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 15. Halophila ovalis (R.Br.) Hook.f., a common species in this region. It is
well known as a dugong food.
Figure 16. The Google earth map of the study area, circled in red, at RBR.
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 17. The Google earth map of the study area ,circled in red, at HCM.
2. Seagrass biomass, sediment grain size and % carbon
There were significant differences between the above and below ground
biomass between sites, species, coverage and their interactions (Table 1). HCM had a
greater biomass than RBR. Since it is the largest tropical species, Enhalus acroides,
(it reaches 1.5 + m in height), had greater above and below ground biomass. The
highest above ground biomass was found in the healthy E. acroides stand at 200 g/m2
(Fig. 18A). The smallest species, Halodule uninervis, provided the smallest biomass
(Fig. 18B). A similar pattern was also observed in the below ground plant parts: the
larger plants had a larger below ground biomass reflecting their coarse, tough
rhizomes. The highest average below ground biomass was 419 g/m2, while the
smallest average below ground biomass was only 1.0 g/m2 found in the C. serrulata
stand with 20 % coverage (Figs. 18A,B).
Seagrass bed as a carbon sink, an assessment from Thailand
There was a significant difference in % carbon of above ground plant material
between species and with coverage (Table 1). The healthy populations had greater %
carbon than the unhealthy. The highest average elemental carbon was measured in the
healthy stands of Cymodocea serrulata at 37.40%. The smallest was 31.12 % in an
Enhalus acoriodes unhealthy bed (Figs. 19A, B).
There were significant differences in carbon production between above and
below ground among sites, species and coverage (Table 1). The healthy seagrass had
greater carbon production than the unhealthy seagrass. The highest above ground
production at RBR was 67.44 g/m2in the healthy Enhalus bed and the smallest was a
mere 0.67 g/m2 in the unhealthy Halodule bed (Fig. 20A). The below ground
production, however, was over 2 times greater at 151.16 g/m2 (Fig. 20B), representing
a more significant amount of carbon storage.
There were significant differences in sediment grain size among sites, species
and coverage (Table 2). The coverage itself, however, did not influence the sedimenttrapped fractions within the seagrass bed. Most of the trapped sediment size was > 63
μm, mostly between 63-125 μm. RBR had clearly different sediment fractions
compared to HCM (Fig. 21). Larger sediment sizes were found at RBR. Fine clays
were also present. There were a few bivalves observed within the bed. The
proportion of < 63 μm particles at RBR was significantly greater than at HCM. The
Thalassia hemprichii bed at HCM had a larger fractions than in other beds.
There were significant differences in % carbon content in sediment among
sites, species and coverage (Table 2). The < 63 μm sediment had much greater %
carbon. RBR had much greater % carbon than the HCM (Fig. 22). The greatest
average % carbon at 4.66% in the sediment was found in the Halodule uninervis bed
at HCM.
The living plant carbon storage is approximately 6.08 Mg C at RBR and
335.16 Mg C at HCM. These estimates do not include the additional source in soil
carbon.
Seagrass bed as a carbon sink, an assessment from Thailand
(A)
(B)
Figure 18. (A) Average above ground biomass and (B) below ground biomass at 20%
and 80% coverages at HCM and RBR, n=3, error bar = SE; Th=Thalassia hemprichii,
Ea=Enhalus acoriodes, Ho=Halophila ovalis, Cr=Cymodocea rotundata,
Cs=Cymodocea serrulata, Si =Syringodium isoetifolium, Hu= =Halodule uninervis.
Seagrass bed as a carbon sink, an assessment from Thailand
(A)
(B)
Figure 19. (A)The average % carbon element in the above ground biomass and (B)
the % carbon in the below ground biomass at 20% and 80% coverages at HCM and
RBR, n=3, error bar = SE; Th=Thalassia hemprichii, Ea=Enhalus acoriodes,
Ho=Halophila ovalis, Cr=Cymodocea rotundata, Cs=Cymodocea serrulata, Si
=Syringodium isoetifolium, Hu= =Halodule uninervis.
Seagrass bed as a carbon sink, an assessment from Thailand
(A)
(B)
Figure 20. (A) The average above ground areal carbon production and (B) The below
ground areal carbon production at 20% and 80% coverages HCM and RBR, n=3,
error bar = SE; Th=Thalassia hemprichii, Ea=Enhalus acoriodes, Ho=Halophila
ovalis, Cr=Cymodocea rotundata, Cs=Cymodocea serrulata, Si =Syringodium
isoetifolium, Hu= =Halodule uninervis.
Seagrass bed as a carbon sink, an assessment from Thailand
Table 1. The summary of the mean ± (SE) of above and below ground, % carbon and carbon content HCM and RBR; * is P <0.05 and ** is P
<0.01
HCM
Th
Parameters
20%
2
Above ground biomass (g/m )
Below ground biomass (g/m2)
Carbon element in above ground (%)
Carbon element in below ground (%)
Above ground carbon (Mg/ha)
Below ground carbon (Mg/ha)
Ea
80%
20%
Ho
80%
20%
RBR
Cr
80%
20%
Cs
80%
20%
Si
80%
20%
Hu
80%
20%
Cs
20%
Site
Species
Cover
20%
F or Chisquare
F or Chisquare
F or Chisquare
5.371 *
80%
35.71
70.34
59.85
200.72
3.4
10.90
10.0
38.12
3.3
10.95
4.05
30.8
0.67
4.74
16.68
1.87
(2.03)
(12.70)
(9.51)
(20.79)
(1.15)
(0.43)
(3.70)
(21.84)
(0.57)
(0.68)
(0.56)
(4.80)
(0.18)
(0.43)
(2.26)
(0.59)
105.88
153.60
128.28
419.08
3.9
6.45
25.0
59.74
1.0
12.78
1.56
16.5
4.26
12.81
26.82
4.31
(6.91)
(22.43)
(48.85)
(22.56)
(0.05)
(0.33)
(9.31)
(25.68)
(0.33)
(4.28)
(0.39)
(4.55)
(2.01)
(1.96)
(4.70)
(1.18)
34.44
33.85
31.12
33.31
33.89
32.46
35.64
35.23
36.82
37.40
33.78
33.66
36.04
36.41
34.57
36.90
(0.50)
(1.01)
(1.23)
(1.52)
(2.50)
(1.20)
(0.52)
(1.25)
(0.41)
(0.37)
(0.63)
(0.36)
(0.20)
(0.61)
(0.50)
(1.12)
34.13
34.67
34.21
36.09
28.44
33.45
33.52
35.42
36.57
36.58
35.43
33.52
33.03
34.43
33.55
35.25
(0.10)
(0.85)
(0.63)
(0.25)
(1.83)
(8.89)
(1.33)
(0.87)
(0.28)
(0.10)
(0.42)
(0.95)
(0.33)
(0.35)
(0.71)
(1.39)
0.123
0.239
0.187
0.674
0.011
0.035
0.036
0.137
0.012
0.041
0.014
0.104
0.014
0.017
0.057
0.007
(0.009)
(0.046)
(0.032)
(0.096)
(0.004)
(0.003)
(0.014)
(0.078)
(0.002)
(0.002)
(0.002)
(0.016)
(0.007)
(0.002)
(0.007)
(0.002)
0.361
0.536
0.442
1.512
0.011
0.021
0.086
0.216
0.004
0.047
0.006
0.056
0.014
0.044
0.090
0.016
(0.023)
(0.091)
(0.169)
(0.072)
(0.001)
(0.006)
(0.034)
(0.097)
(0.001)
(0.016)
(0.001)
(0.017)
(0.007)
(0.007)
(0.017)
(0.005)
Seagrass bed as a carbon sink, an assessment from Thailand
Species x Cover Site x Species xCover
Hu
F or Chi-square
F or Chi-square
63.507 ** 20.335 **
49.076 **
43.185 **
0.859
90.290 ** 11.194 *
64.135 **
55.621 **
3.158
21.966 *
3.485
26.298 *
31.531 *
7.740
0.529
0.156
14.147
25.398
5.097 *
43.886 ** 20.336 **
35.332 **
31.079 **
0.637
90.323 ** 11.686 *
65.299 **
56.536 **
Table 2. The summary of the mean ± (SE) of sediment grain sizes and % carbon element in sediment at HCM and RBR; * is P <0.05 and ** is
P <0.01
HCM
Th
Parameters
Sediment grain size
< 63µm (%)
Ea
Ho
RBR
Cr
Cs
Si
Cs
Hu
Site
Species
Cover
Species x Cover Site x Species x Cover
F or Chisquare
F or Chisquare
F or Chisquare
F or Chi-square
F or Chi-square
0.001
14.583
44.660 **
3.426
34.930 **
44.704 **
0.577
39.485 **
48.143 **
0.243
33.003 **
47.572 **
Hu
20%
80%
20%
80%
20%
80%
20%
80%
20%
80%
20%
80%
20%
20%
80%
20%
0.75
0.83
0.66
1.15
0.58
0.75
0.41
0.33
0.14
0.33
0.16
0.24
0.11
6.34
7.35
7.96 36.322 ** 13.499 *
(0.40) (0.37) (0.26) (0.40) (0.36) (0.22) (0.08) (0.22) (0.02) (0.06) (0.02) (0.08) (0.03) (2.30) (2.37) (2.04)
Sediment grain size
> 63µm (%)
99.25
99.17
99.34
98.85
99.42
99.25
99.59
99.67
99.86
99.67
99.84
99.76
99.89
93.66
92.65
92.04 36.322 ** 33.294 **
(0.40) (0.37) (0.26) (0.40) (0.36) (0.22) (0.08) (0.22) (0.02) (0.06) (0.02) (0.08) (0.03) (2.30) (2.37) (2.04)
Carbon in Sediment grain size
< 63µm (%)
0.73
1.34
1.19
0.85
0.98
1.03
0.72
0.44
0.87
2.20
1.11
1.28
4.66
3.65
3.23
3.63 25.998 ** 37.036 **
(0.25) (0.19) (0.38) (0.22) (0.05) (0.09) (0.10) (0.12) (0.05) (0.11) (0.29) (0.17) (0.12) (0.22) (0.41) (0.15)
Carbon in Sediment grain size
> 63µm (%)
0.23
0.27
0.20
0.20
0.19
0.21
0.17
0.15
0.18
0.24
0.18
0.22
1.34
2.77
2.52
2.48 36.363 ** 31.971 **
(0.04) (0.02) (0.02) (0.02) (0.01) (0.01) (0.03) (0.02) (0.02) (0.03) (0.03) (0.02) (0.14) (0.17) (0.15) (0.21)
Seagrass bed as a carbon sink, an assessment from Thailand
Figure 21. The proportion of sediment grain sizes of soil at 20% and 80% coverages
at HCM and RBR, n=3, error bar = SE; Th=Thalassia hemprichi, Ea=Enhalus
acoriodes, Ho=Halophila ovalis, Cr=Cymodocea rotundata, Cs=Cymodocea
serrulata, Si =Syringodium isoetifolium, Hu= =Halodulae uninervis.
Figure 22. The percent elemental carbon in the soil at 20% and 80% coverages at
HCM and RBR, n=3, error bar = SE; Th=Thalassia hemprichii, Ea=Enhalus
acoriodes, Ho=Halophila ovalis, Cr=Cymodocea rotundata, Cs=Cymodocea
serrulata, Si =Syringodium isoetifolium, Hu= =Halodule uninervis.
Seagrass bed as a carbon sink, an assessment from Thailand
Discussion
The average above and below ground biomass measured in our study was
much less than reported by Durate and Chiscano (1999). The Thalassia hemprichii
above and below ground biomass, for example, was 20% and 40% less than
previously reported. The Halophila ovalis the above ground biomass presented
only12.5% and the below ground was only 25%, also less. Enhalus acoriodes was the
only species in which the biomass was higher than reported by Durate and Chiscano
(1999). Therefore, it is possible that E. acoroides is resistant to change and that our
seagrass beds have become less healthy over the last 20 years.
The overall biomass at RBR was greater than at HCM which may be
correlated with the fact that RBR is much more pristine and less disturbed by human
activities. We rarely observed human activities at RBR during our field collections,
but we often found shell collectors trampling on the seagrasses during our field work
at HCM. There is more coastal development and tourism at the HCM sites. The
decline of biomass could be a result from anthropogenic activities: coastal
developments increase the sediment loading and more broadly the increase of
temperature due to global climate change. Further investigations are needed to clarify
what the major threats to the decrease of seagrass biomass at these sties are.
There is little variation in % carbon content among seagrass leaves worldwide.
According to Duarte (1999) the average (± SE) carbon was 33.6 ± 0.31 % DW,
similar to the measurements in our studies in which the highest % carbon content was
found in Cymodocea serrulata. The below ground % carbon content showed no
differences from one species to another. The lowest % carbon content was the below
ground tissue of Halophila ovalis, 28.44 ± 1.83 % DW from the unhealthy stand. H.
ovalis has a different rhizome and root structure from other seagrasses. Its thin
rhizomes are anchored shallower in the sediments. The plants are younger compared
to the other species. In a Bolinao, The Philippines, study the PI was 2.2 leaves/day
(Vermaat et al., 1995). The plants grow faster and expand their meadows rapidly,
which even if it does not allow them to accumulate much carbon promotes
productivity. They produced 165.9 leaves/shoot/ year, while the E. acoriodes
produced only 11.5 leaves/shoot/year. The longevity of H. ovalis was less, only 27 ±
Seagrass bed as a carbon sink, an assessment from Thailand
4.2 day compared to 787 ± 125 days of E. acoriodes, suggesting a very high turn
over rate. H.ovalis, thus, is less of a carbon sink than other seagrass species.
The carbon content of above and below ground biomass of living seagrasses
parallels their above and below ground biomass. The below ground biomass stored 2
times carbon/ha than the above ground. It ranged between 0.011 – 1.512 Mg/ha to
0.007-0.674 Mg/ha respectively. E. acoroides contributed the greatest living carbon
storage due to its high biomass. Thus, the healthy and dense seagrass beds are
important and contribute to the greatest storage of carbon in the seagrass ecosystems.
The fine sediment < 63 μm was significant greater at RBR due to the location
near the mangrove forests by the enclosed bay, which allows the fine sediment to
settle rather than being washed away at the open coasts as at HCM. The greater
proportion of >63 μm in RBR might also be caused by filtering bivalves in the beds.
Such beds are well known habitats for animals. We observed various fishes, crabs,
shrimp and sea cucumbers at our collection sites.
Fine clay, < 63 μm, has a greater % carbon content than the larger sized
sediments. According to Fourqurean et al (2012), the average Corg of seagrass soils
was 1.4%, ranging between 0-48.2. Our sediment % carbon at RBR ranged between
2.48-3.65 and at HCM ranged between 0.15-4.66 %. Halodule uninervis soils
provided a high % carbon at both sites. This might be because plants materials were
buried. H. uninervis has fine long, narrow leaves, which normally lie close onto the
substrate when the tide is out. Plants are easily buried by the sediment when there is
high sediment loading from a terrestrial system or if broken off and buried. It is clear
that further investigations are important to better understand the carbon reserves that
buried materials provide.
Acknowledgements
I am grateful for the 2012 MAB Young Scientists Award, MAB Program,
UNESCO for support. The Cluster and Program management Office, National
Science and Technology Development Agency of Thailand provided assistance for
the extensive dataset used in this report. I am grateful for Seaweed and Seagrass
Research Unit, Excellence Centre for Biodiversity Peninsular Thailand, Department
of Biology, Faculty of Science, Prince of Songkla University for extensive help
Seagrass bed as a carbon sink, an assessment from Thailand
throughout the field and laboratory studies. Piyalap Tuntiprapas provided invaluable
help with data analyses and discussion. Prof. Larry B. Liddle helped improve the
English.
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