A Baseline Measure of ree and T astropod G 25(1)-Art. 1(1-12).pdf Four sites were sampled in Sungai

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  • Tropical Life Sciences Research, 25(1), 1–12, 2014

    © Penerbit Universiti Sains Malaysia, 2014

    A Baseline Measure of Tree and Gastropod Biodiversity in Replanted and Natural Mangrove Stands in Malaysia: Langkawi Island and Sungai Merbok 1Brenda Hookham, 2Aileen Tan Shau-Hwai, 3Benoit Dayrat and 1William Hintz∗ 1Department of Biology, University of Victoria, PO Box 3020 STN CSC, Victoria, BC, V8W 3N5, Canada 2School of Biological Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia 3School of Natural Sciences, University of California, Merced, 5200 North Lake Rd, Merced, CA 95343, USA Abstrak: Kepelbagaian pokok bakau dan gastropod yang berkaitan telah dikaji di dua kawasan bakau di pantai barat Semenanjung Malaysia: Pulau Langkawi dan Sungai Merbok. Kawasan bakau yang disampel di Pulau Langkawi baru dibalak dan ditanam semula, manakala kawasan yang disampel di Sungai Merbok adalah sebahagian daripada rizab semula jadi yang dilindungi. Kepelbagaian bakau dan gastropod dinilai dalam empat tapak kajian bersaiz 50 m2 (10 × 5 m) bagi setiap kawasan. Nilai kekayaan spesies (S), Indeks Shannon (H’) dan indeks evenness (J’) dikira bagi setiap tapak kajian, dan nilai min S, H’ dan J’ dikira bagi setiap kawasan. Keputusan menunjukkan nilai S, H’ dan J’ bagi pokok dan gastropod dari kesemua kawasan kajian dari kedua-dua tapak adalah rendah. Untuk Pulau Langkawi, nilai min S, H’ dan J’ bagi pokok bakau adalah S = 2.00±0, H = 0.44±0.17 dan J’ = 0.44±0.17; nilai min bagi gastropod adalah S = 4.00±1.63, H’ = 0.96±0.41 dan J’ = 0.49±0.06. Di Sungai Merbok, nilai min S, H’ dan J’ bagi pokok bakau adalah S = 1.33±0.58, H’ = 0.22±0.39 dan J’ = 0.22±0.39; nilai min bagi gastropod adalah S = 4.75±2.22, H’ = 1.23±0.63 dan J’ = 0.55±0.12. Kajian ini menekankan keperluan ukuran kajian asas biodiversiti diadakan untuk ekosistem bakau untuk mengesan impak gangguan antropogenik dan sebagai panduan untuk usaha-usaha pengurusan dan pemulihan ekosistem bakau. Keywords: Biodiversiti Bakau, Biodiversiti Gastropod, Biodiversiti Pokok, Biologi Pemulihan Abstract: The diversities of mangrove trees and of their associated gastropods were assessed for two mangrove regions on the west coast of Peninsular Malaysia: Langkawi Island and Sungai Merbok. The mangrove area sampled on Langkawi Island was recently logged and replanted, whereas the area sampled in Sungai Merbok was part of a protected nature reserve. Mangrove and gastropod diversity were assessed in four 50 m2 (10 × 5 m) sites per region. The species richness (S), Shannon Index (H’) and Evenness Index (J’) were calculated for each site, and the mean S, H’ and J’ values were calculated for each region. We report low tree and gastropod S, H’ and J’ values in all sites from both regions. For Langkawi Island, the mean S, H’ and J’ values for mangrove trees were S = 2.00±0, H’ = 0.44±0.17 and J’ = 0.44±0.17; the mean S, H’ and J’ values for gastropods were S = 4.00±1.63, H’ = 0.96±0.41 and J’ = 0.49±0.06. In Sungai Merbok, the mean S, H’ and J’ values for mangrove trees were S = 1.33±0.58, H’ = 0.22±0.39 and J’ = 0.22±0.39; the mean S, H’ and J’ values for gastropods were S = 4.75±2.22, H’ = 1.23±0.63 and J’ = 0.55±0.12. This study emphasises the need for baseline biodiversity measures to be established in mangrove ecosystems to track the impacts of anthropogenic disturbances and to inform management and restoration efforts. ∗Corresponding author: whintz@uvic.ca


  • Brenda Hookham et al.


    Keywords: Mangrove Biodiversity, Gastropod Biodiversity, Tree Biodiversity, Restoration Biology INTRODUCTION Mangroves are found globally in tropical and subtropical regions at the confluence of marine and terrestrial environments and support a unique ecosystem of considerable importance (FAO 2007; Alongi 2002; Tomlinson 1986). As the net primary production from mangrove flora far exceeds the ecosystem requirements, mangroves can function as both carbon sinks and carbon sources for the surrounding marine ecosystems (Cannicci et al. 2009; Duke et al. 2007; Duarte & Cebrian 1996). This highly productive ecosystem supports a wide range of animals, including molluscs (e.g. gastropods, bivalves), arthropods (e.g. crustaceans), fish, birds, reptiles (e.g. crocodiles), amphibians and mammals (FAO 2007; Ashton & Macintosh 2002). Mangroves function as breeding and nursery areas for shrimp, crabs and marine fish and have been found to positively influence the biomass of fish (including commercially important species) on neighbouring coral reefs (Mumby et al. 2004; Ashton & Macintosh 2002).

    Mangroves also provide ecosystem services with substantial economic value with respect to waste treatment (e.g. pollution control, detoxification), disturbance regulation (e.g. storm protection, flood control), and, to a lesser extent, food production, habitat (e.g. nurseries for commercially important species) and raw materials (Costanza et al. 1997). Globally, the estimated worth of mangrove services is US$ 180,895,923,000 (Alongi 2002 based on values in Costanza et al. 1997). Nevertheless, current practices suggest that the consequences of mangrove loss are not well appreciated (Duke et al. 2007). Mangroves are being rapidly destroyed worldwide due to urban and industrial coastal development, overexploitation of mangrove resources, aquaculture (especially shrimp ponds) and agriculture (Amin et al. 2009; Duke et al. 2007; Ashton et al. 2003; Alongi 2002; Ashton & Macintosh 2002).

    The Indo-West Pacific has the largest combined mangrove area in the world and boasts the highest biodiversity, particularly in South East Asia (Sandilyan & Kathiresan 2012). Malaysia is second only to Indonesia in the size and biodiversity of its mangrove areas (FAO 2007). During the past 25 years, extensive mangrove loss has occurred in Malaysia (≈109000 ha), and significant replanting programmes are required to remedy this loss (FAO 2007). The current sustainably managed mangroves or replanted mangroves are often monoculture stands of economically valuable species, e.g. Rhizophora spp. (Walton et al. 2007; Bosire et al. 2006; Alongi 2002; Ashton & Macintosh 2002; Ellison 2000). The possible deleterious effects of monoculture stands on the associated faunal communities have not been properly addressed in restoration projects (Bosire et al. 2008). A measure of success for replanting programmes is mangrove biodiversity, i.e., the replanted stands should ideally resemble natural stands.

    The aim of this study was to provide an initial, baseline measure of tree and gastropod biodiversity in two Malaysian mangrove areas: Langkawi Island

  • Biodiversity in Mangroves of Langkawi and Merbok


    and Sungai Merbok. The sites sampled on Langkawi Island were actively logged and replanted, whereas the sites sampled in Sungai Merbok represented a natural stand. The species richness, diversity and evenness of tree species were assessed for both regions to determine if the replanted stands maintained the same level of diversity found in the natural stands. Furthermore, the species richness, diversity and evenness of gastropods were assessed in both regions to determine if faunal communities could become re-established in replanted stands and if the community of gastropods would resemble the communities found in natural stands. MATERIALS AND METHODS Description of Regions and Study Sites Region 1: Langkawi Island The Langkawi Archipelago lies west of Peninsular Malaysia in the Andaman Sea near the Malaysian-Thai border. The archipelago consists of 99 islands at high tide and 104 islands at low tide; sampling was conducted on Langkawi Island, the largest and most densely populated of the islands (Jahal et al. 2009). Langkawi Island is one of Malaysia’s principal tourist attractions and is, therefore, developing rapidly. Coastal development has converted much of the original mangrove area to agricultural lands, aquaculture ponds, mariculture, commercial and residential areas, and jetties that support the increase in boating activity. Furthermore, in areas not designated as Permanent Forest Areas, the local communities on Langkawi Island actively use mangroves for timber. Private use of mangroves for timber is prevalent even in areas designated as Forest Reserves or Permanent Forest Reserves (Shahbudin et al. 2012). Langkawi Island sites Four sites were sampled on Langkawi Island (L1–L4; Fig. 1A–C). The mangrove areas sampled on Langkawi Island, Tanjung Rhu and Kilim, were both exposed to heavy boat traffic associated with tourist activities and were actively logged and replanted. Perhaps the most striking feature of the Langkawi Island sites was the density of the Rhizophora sp. stands. The tight spacing of trees indicates that they had been actively planted, as mature stands are less dense due to self- thinning (Alongi 2002). The trees were logged in all sites visited and then replanted on a continuing basis. The age of the trees, based on trunk diameter and tree height, was estimated to be approximately 5–10 years (Benoit Dayrat pers. comm.). In this study, the sites from Langkawi Island represented replanted stands. Region 2: Sungai Merbok The mangrove area surrounding the Sungai Merbok estuary is located in the state of Kedah in the Northwestern region of Peninsular Malaysia (Somerfield et al. 1998). Thi