Species Diversity, Distribution and Seasonal Abundance in Mangrove Associated Molluscs along the Karachi Coast, Pakistan

Journal of Bioresource Management Volume 2 | Issue 3 Article 2 October 2015 Species Diversity, Distribution and Seasonal Abundance in Mangrove Associated Molluscs along the Karachi Coast, Pakistan Zia Ullah Abdul Wali Khan University, Mardan, Pakistan Itrat Zehra University of Karachi, Pakistan Muhammad Asif Gondal Comsats Institute of Information Technology, Islamabad, Pakistan, Follow this and additional works at: https://corescholar.libraries.wright.edu/jbm Part of the Biodiversity Commons, and the Biology Commons Recommended Citation Ullah, Z., Zehra, I., & Gondal, M. A. (2015). Species Diversity, Distribution and Seasonal Abundance in Mangrove Associated Molluscs along the Karachi Coast, Pakistan, Journal of Bioresource Management, 2 (3). DOI: 10.35691/JBM.5102.0027 This Article is brought to you for free and open access by CORE Scholar. It has been accepted for inclusion in Journal of Bioresource Management by an authorized editor of CORE Scholar. For more information, please contact . Ziaullah et al.,: Species Diversity, Distribution, Seasonal Abundance In Mangrove Associated Molluscs J. Bioresource Manage. (2015) 2(3): 9-22. SPECIES DIVERSITY, DISTRIBUTION AND SEASONAL ABUNDANCE IN MANGROVE ASSOCIATED MOLLUSCS ALONG THE KARACHI COAST, PAKISTAN Ziaullah1, Itrat Zehra2, Muhammad Asif Gondal*3 1 Department of Tourism and Hospitality, Abdul Wali Khan University, Mardan, Pakistan. Centre of Excellence in Marine Biology, University of Karachi, Karachi, Pakistan 3 Department of Biosciences, Comsats Institute of Information Technology, Park Road, Islamabad, Pakistan * Email: 2 ABSTRACT Mangrove or Mangal vegetation are typical wetland ecosystems found in coastal deposits of mud and silt throughout the tropics and some distance into the sub-tropical latitude. Species diversity, distribution, seasonal abundance in population and behavioral responses of mangrove associated molluscs (gastropods and bivalves) were investigated in two mangal areas: Sandspit and Korangi, along the Karachi coast of Pakistan. For sampling, a fixed route was followed throughout the study period and the samples were collected and observations were made from HTZ to LTZ. Fourteen species of molluscs (5 Prosobranchia; 6 Pulmonata; 1 Opisthobranchia and 2 Lamellibranchia) belonging to ten families were recorded. Family Ellobiidae, Potamididae, and Onchididae were found extensively distributed in both sites. All the recorded species are belonging to the epifaunal mode of life. Analysis of the data shows that ten of the recorded species are common to both sites, while four are exclusively found at the Korangi site. Seven of the representative species are exclusively mangrove associated; five are common to mangrove and non-mangrove areas, while two are non-mangrove dwellers. The low species diversity can be attributed either to the study techniques, a small number of study sites or possibly to the geographical locations of the study sites. Seasonal variations were noticed in species diversity and density distribution, indicating higher values in summer and autumn and lower in spring and winter. Keywords: Mangroves, Molluscs, Karachi, Pakistan, Wetland ecosystem. INTRODUCTION Mangrove or Mangal vegetation are typical wetland ecosystems found in coastal deposits of mud and silt throughout the tropics and some distance into the subtropical latitude. The best suitable area for their growth is the sea-land interface, where the saline water mixes with fresh water. In Pakistan, the mangrove plant is locally known as “Timer”. These forests cover about 617,470 hectare in the Indus delta (Vistro, 1999). These wetlands provide both hatching as well as nursery grounds for a large number of commercially important fish and shell fish species. The intricate root systems of mangrove plants provide a habitat for a number of benthic organisms like algae, molluscs, polychaetes, crabs, bryozoans, etc., which all require a hard substratum for anchoring while they filter feed and help to impede water flow, thereby enhancing the deposition of sediment in areas where it is already occurring. 9 Ziaullah et al.,: Species Diversity, Distribution, Seasonal Abundance In Mangrove Associated Molluscs J. Bioresource Manage. (2015) 2(3): 9-22. In the mangrove ecosystem, few animals feed directly on the living trees; however, the deposit in the sediments from mangal leaves, stem, flowers, etc., gradually decompose due to the physical and microbial action, which makes up the basis of the detritus food web (Day, 1975; Evink, 1975). Marine invertebrates are considered an important link between the initial detritus at the bases of the food web and the terminal consumers (Coull et al., 1995). The information regarding the role of invertebrates in the mangrove ecosystem are quite scanty, however. Molluscs and crustaceans are important components of the ecosystem (Jiang and Li, 1995; Wells, 1983, 1990; Milward, 1982; Redfield, 1982). Muddy sands to sands and beachrock are the predominating benthic habitats. The important ecosystem engineers are the oyster Saccostrea cucullata, which forms decimeter- to meter-scale bioherms in the lower intertidal, the ocypodid crab Dotilla sulcata, which reaches highest abundances on the tidal flat, some tens of meters from the low-tide line, and the callianassid decapod Paratrypaea bouvieri, which is very abundant in the subtidal (Zuschin and Ebner, 2015). The herbivorous molluscs play the role of primary consumers in the trophic levels of the mangrove ecosystem, being the grazer or suspension feeders. These gastropods and bivalves are exposed to large numbers of predators, some of whom depend entirely upon these molluscs for their survival. Malacophagous predators include fish, birds and mammals and the molluscs thus play an important role in the complex food web of the mangrove ecosystem (Chaudhuri and Chaudhury, 1994). Keeping in view the immense value of molluscs in the mangrove ecosystem, a number of studies have been performed throughout the world on the ecological relationships of mangroves and molluscs (Suresh et al., 2012; Venkatesan et al., 2010; Kesavan et al., 2009; Shanmugam and Vairamani, 2009; Dey 2006; Ingole et al., 2002; Pereira et al., 2002; George 1995; Jiang and Li 1995; Britton, and McMahon, 1990; Das and Roy 1989; Peckol et al., 1989; Little 1989; Fairweather 1988; Price et al., 1987; Reid 1986; Gao and Li 1985; Shokita et al., 1985; Mandal and Misra, 1985; Centraet et al., 1983; Morton and Morton 1983; Takenouchi 1983; Wells 1983, 1984, 1985, 1986 and 1990; Chambers 1980; Yipp 1982; Petraitis 1982;). At the regional level, the mangrove flora received due attention and is therefore well documented. On the contrary, the mangrove fauna, particularly the molluscan fauna, is not paid due attention and is therefore poorly known. An increase of species density and diversity in the Post monsoon season was highest at 2 locations of Pondicherry mangroves whereas lowest was obse (...truncated)