101 / 2023-07-30 15:28:26

Assessment on Sediment Characteristics in Cockle Culture Areas along the Mudflats in Klang Straits, Selangor, Malaysia

blood cockle,particle size,organic carbon,inorganic carbon,heavy metal

Tropical intertidal mudflats are soft bottom habitat that are exposed to air during low tide and submerged during high tide. Due to their high productivity, mudflats are important habitats to migratory birds and various fish, crabs, as well as the macrobenthos communities. In Malaysia, mudflats are usually used for shellfish aquaculture, especially aquaculture of blood cockles Tegillarca granosa. Blood cockles are important aquaculture species, compromising 91 % of bivalve aquaculture production in Malaysia. However, unstable production and mass mortality of blood cockles has been reported throughout the years. Blood cockles are benthic, sessile feeders that are directly influenced by sediment characteristics. The association between the sediment and the cultured blood cockles are however, still poorly understand, hindering comprehensive assessment on the ecosystem management practices related to blood cockle culture. This study aimed to address this existing knowledge gap by assessing the sediment particle size composition, organic and inorganic content, chlorophyll a content and heavy metal content of sediment from blood cockles culture sites. Sediment samples were collected monthly between May 2022 and January 2023 from culture and/or non-culture sites in three areas along Klang Straits namely Kuala Selangor (KS), Assam Jawa (AJ) and Bagan Sungai Buloh (SB). Generally, culture sites had higher bottom water dissolved oxygen (DO) levels, finer and more well sorted sediment particle sizes, low organic matter (OM) and total organic carbon (TOC) but high total inorganic carbon (TIC). The lower organic matter in cultures sites may be due to the greater rate of re-mineralisation process induced by the higher DO of the well mixed water. The higher TIC in culture sites may infer influence of shell fragments and possibly re-mineralisation resulted from bioturbation by the dense blood cockles as well as dredging/thinning activities by fishermen and passing of boats in the culture sites. Heavy metals content for both sediment and cockles showed no significant differences among the sampled sites, and were within the safety level based on various indices (CF, Igeo and EF). The study outcome seeks to contribute baseline information that can be useful to improve ecosystem management of cockle culture