Elsevier

Journal of Sea Research

Volume 176, October 2021, 102113
Journal of Sea Research

Carbon stock of disturbed and undisturbed mangrove ecosystems in Klang Straits, Malaysia

https://doi.org/10.1016/j.seares.2021.102113Get rights and content

Highlights

  • Ecosystem carbon stock in mangrove environment can be influenced by its land use status.

  • Soil organic carbon in undisturbed mangrove forest can contribute to the majority of the ecosystem carbon stock, regardless of the vegetation stands.

  • Isotope data revealed that the mangrove leaf and suspended particulate organic matter in the sea water are the sources of soil organic matter.

Abstract

Ecosystem carbon stocks were compared in three island mangrove forests, subjected to different anthropogenic stresses, close to Port Klang in Selangor State on the west coast of Peninsular Malaysia. Carbon stocks in living biomass, litter, deadwood and soil were quantified, and the carbon isotopic signature in mangrove soils was also measured, to estimate their carbon source. We hypothesize that carbon stock would be more readily available in undisturbed mangroves. The results indicated that, in general, soil organic carbon pool comprised the majority of the ecosystem carbon stock, while dead organic matter made a negligible contribution. The highest ecosystem carbon stock was measured in the permanent undisturbed mangrove reserve on Pulau Klang. Carbon isotope data revealed that disturbed mangroves in Pulau Ketam had a more enriched δ13C signature of soil samples compared to the other two sites. The soil organic carbon in Pulau Ketam was mostly derived from mangrove materials (92.8%). The results suggested that the organic carbon accumulated in the soils was not only regulated by the burial of mangrove-derived organic carbon, but also the site conditions.

Introduction

Mangrove forest has a unique setting, occupying the margin between land and sea, in mostly sheltered tropical and subtropical coastlines. It is a crucial coastal ecosystem, providing important coastal and marine resources for economic and social benefits. It also offers environmental services and critical ecological functions (Bosire et al., 2008; Walters et al., 2008) by protecting inland areas from unpredictable disasters such as typhoons and tsunamis. In addition, mangroves act not only as breeding and rearing habitats for many species of fish and shellfish, but also as a source of valuable products including wood, thatch, medicines, dyes and seafood (Kauffman and Donato, 2012). Mangrove forest can also act as a biofilter, including for heavy metal pollution (Usman et al., 2013).

It is very important to note that mangrove forests are carbon-rich ecosystems that are able to mitigate climate change because they sequestrate a substantial amount of organic carbon (OC) (Mcleod et al., 2011; Siikamäki and Sanchirico, 2012). The global mean carbon stock in mangrove forests is higher than any other forest types, such as tropical forest, temperate forest, boreal forest and tropical savannas (Kauffman and Donato, 2012). The organic carbon is mainly stored in living biomass (above-ground and below-ground biomass) and in soil in the mangrove forests.

Mangrove forests can easily lose organic carbon if they are disturbed, for example changed into another landuse (Kauffman and Donato, 2012; Hamilton and Casey, 2016). Annually, mangrove deforestation releases more than 0.02 Pg carbon per year, which is around 2–10% of carbon release from deforestation in tropical areas, even though mangrove forest accounts for only 1% of the tropical forest area globally (Donato et al., 2012). Despite the many recognized ecosystem services of mangrove forests, the mangrove area has declined globally, between 0.16% and 0.39% per year (Hamilton and Casey, 2016). The majority of contemporary mangrove loss occurs in Southeast Asia, at an annual rate between 3.58% and 8.08% (Hamilton and Casey, 2016), largely due to conversion to shrimp and fish aquaculture, rice, oil palm plantations and urban development. More than 114,000 ha of mangrove forests (2.5%) have been converted to aquaculture ponds, rice or oil palm fields from 2000 to 2012 (Richard and Friess, 2016). A recent study estimated that Malaysia now possesses a total of 629,038 ha of mangrove forest, having lost 0.13% per year of mangrove area since 1990 (Omar et al., 2019). Because of the critical roles of mangroves in global carbon sequestration and providing other ecosystem services, and their vulnerability to land use changes, it is important to estimate the carbon stocks in mangrove ecosystems so as to support climate change mitigation strategies and policies (Adame et al., 2015).

Biomass also determines the potential of carbon sequestration depending on the type of forest, maturity age, species distribution and soil conditions (Alongi, 2012). Generally, the carbon sequestration potential increases with plant size and age (Alongi, 2011; Alongi, 2012). Mangroves ecosystems sequester carbon at mean rate of 1110 to 1363 gC m−2 yr−1 globally with 70% of the carbon captured ending up as biomass (Bouillon et al., 2008; Alongi, 2014). Because of this, it is very crucial to determine the carbon stock and its potential sequestration in mangrove ecosystems, in view of the fast changing land use and anthropogenic activities in this region.

Mangrove materials are generally the major source of the carbon that accumulates in the associated soils (Kristensen et al., 2008; Adame and Fry, 2016). However, in mangrove forests located in river- and tide-dominated areas, the relative contribution of allochthonous (terrestrial or marine) organic matter may be higher (Jennerjahn and Ittekkot, 2002). The isotopic signature of soil organic carbon is widely used to detect the sources of the carbon (Stevenson et al., 2005). The more depleted soil δ13C value reflects more mangrove-derived OC accumulated in the mangrove soils (Chen et al., 2018a). The terrestrial nutrient inputs have been found to increase benthic metabolism and nitrogen dynamics, and decrease the burial/storage rate of OC in soils (Molnar et al., 2013; Suarez-Abelenda et al., 2014). These suggested that the anthorpogenic distubances could also regulate the carbon sequestration capacity of a mangrove ecosystem.

Selangor state is the most populated and developed state in Malaysia, with the most economic activities including industries, agriculture, port and residentials. The mangroves of Selangor are found mostly around the mouths of major rivers such as Selangor River, Langat River and Klang River, as well as along beaches and around islands in Klang district. As one of the states in the country with the largest remaining mangroves, the potential for carbon sequestration in Selangor's mangrove ecosystem is of key importance.

The Straits of Malacca is one of the busiest waterways in the world, with many human activities including shipping, transportation, oil and gas, as well as many industries along its coasts. The Klang Islands consist of seven islands, once covered by pure mangrove forest, in the Straits of Malacca. Because of their proximity to the urban and industrial areas of Port Klang, some of these mangrove areas have been heavily affected by anthropogenic activities. For instance, on Telok Gong and Pulau Ketam, part of the mangrove area has been disturbed and reclaimed for industrial area and human settlements. However, some mangrove areas in Klang are under legal protection as undisturbed forest reserves, such as on Pulau Kelang. Thus, this project aims to identify how anthropogenic activities are affecting the remaining areas of the Klang Islands Mangrove Forest in terms of ecosystem carbon storage potential. We hypothesize that human disturbance will reduce the carbon stock potential especially in the soil pool.

Section snippets

Study area

The Klang Straits Islands Mangrove Forest, consisting of seven major islands, is located between two estuaries, the Klang River Estuary and the Langat River Estuary. Both rivers flow into the Straits of Malacca, forming a Klang Delta and Klang Strait. This group of islands is the largest mangrove ecosystem in the state of Selangor. The samplings were conducted within the Klang Islands Mangrove Forest (Fig. 1), which is located in the state of Selangor, on the west coast of Peninsular Malaysia.

Tree carbon stock

Table 2 shows that Teluk Gong had highest total (both above-ground and below-ground combined) tree carbon (89.18 ± 67.46 Mg C ha−1), followed by Pulau Klang (68.79 ± 43.26 Mg C ha−1) and Pulau Ketam (65.68 ± 19.43 Mg C ha−1), even though the number of tree in Telok Gong was reportedly the lowest (n = 174) among sampling (Zakaria et al., 2018). This was due to it having larger size trees compared to the other two sites, with patches of forest reserve within the intensely human impacted area. The

Conclusion

Large mangrove areas like Klang Straits would certainly contribute to large emissions when perturbed, shown in this study where disturbed areas have reduced their carbon stocks. Since the large proportion of carbon is stored in the soil, it is imperative to clearly understand the impact of land use changes as they can contribute to significantly higher carbon emissions and thus contributes to increment of global warming.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The study was supported by University of Malaya, Malaysia (RP019D-16SUS). We thank Forestry Department of Peninsular Malaysia and Selangor State Forestry Department for the permission and assistance during fieldwork campaigns, staff and students of the Institute of Biological Sciences, University of Malaya. We acknowledged Third Institute of Oceanography, Xiamen China for conducting isotope analysis, Institute of Biological Science and Mr. L P Renshaw for English editing service.

References (47)

  • B.A. Stevenson et al.

    The stable carbon isotope composition of soil organic carbon and pedogenic carbonates along a bioclimatic gradient in the Palouse region, Washington state, USA

    Geoderm

    (2005)
  • M. Suarez-Abelenda et al.

    The effect of nutrient-rich effluents from shrimp farming on mangrove soil carbon storage and geochemistry under semi-arid climate conditions in northern Brazil

    Geoderma

    (2014)
  • Adel R.A. Usman et al.

    Heavy metal contamination in sediments and mangroves from the coast of Red Sea: Avicennia marina as potential metal bioaccumulator

    Ecotoxicol. Environ. Saf.

    (2013)
  • B.B. Walters et al.

    Ethnobiology, socio-economics and management of mangrove forests: a review

    Aquat. Bot.

    (2008)
  • M.F. Adame et al.

    Source and stability of soil carbon in mangrove and freshwater wetlands of the Mexican Pacific coast

    Wetl. Ecol. Manag.

    (2016)
  • M.F. Adame et al.

    Carbon stocks and soil sequestration rates of tropical riverine wetlands

    Biogeosciences

    (2015)
  • D.M. Alongi

    The Energetics of Mangrove Forests

    (2009)
  • D.M. Alongi

    Carbon sequestration in mangrove forests

    Carbon Manag.

    (2012)
  • D.M. Alongi

    Carbon cycling and storage in mangrove forests

    Annu. Rev. Mar. Sci.

    (2014)
  • C.A. Black

    Methods of Soil Analysis. Part 1. American Society of Agronomy (No 9)

    (1965)
  • S. Bouillon et al.

    Sources of organic carbon in mangrove sediments: variability and possible ecological implications

    Hydrobiologia

    (2003)
  • S. Bouillon

    Mangrove production and carbon sinks: a revision of global budget estimates

    Glob. Biogeochem. Cycles

    (2008)
  • J.K. Brown et al.

    Handbook for inventorying surface fuels and biomass in the interior West

  • Cited by (16)

    View all citing articles on Scopus
    View full text