Foraminiferal and Geochemical Evidence of Environmental Change in Response to Aquaculture in the Setiu Estuarine-Lagoonal System Terengganu Malaysia

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)
Hanna Thornberg (Creator)
East Carolina University (ECU )
Web Site:
Stephen Culver

Abstract: In many coastal communities aquaculture is an important part of the local economy though fish and shrimp farms may threaten habitats in these coastal systems. Aquaculture was introduced to the Setiu estuarine-lagoonal system (SEL) in Terengganu Malaysia in the mid-1970s. As fish farm densities increase and the mangroves are cleared excess nutrients and fish waste are supplied to the water column and sediments below. In order for the aquaculture industry in Terengganu Malaysia to be successful estuarine-lagoonal environmental health should be monitored. Analyses of foraminiferal assemblages sedimentological analyses and δ13C δ15N and C:N ratios are used here to determine how aquaculture in the SEL affects benthic communities sources of organic matter and grain size and sediment composition.  Three cores were collected beneath fish cage sites two (S43 and S40) from the northern lagoon region and one (S9A) from the southern estuary region. Cores S43 and S40 contain both calcareous and agglutinated foraminifera though calcareous are dominant. Agglutinated specimens increase in abundance near the top of S43 and S40 which is likely in response to an increase in organic matter.. Ammonia aff. A. aoteana and Ammobaculites exiguus are the most abundant species in the middle and upper sections of S43 and Ammonia aff. A. aoteana and Rosalina globularis are the most abundant in the bottom of S43. Ammonia aff. A aoteana is most abundant throughout all of S40. Core S9A contains only agglutinated foraminifera with Trochammina amnicola Ammotium directum and Miliammina fusca as the most abundant species. The percent of live specimens is relatively low in all three cores. The densities of dead foraminifera at S43 and S40 are extremely high at the onset of aquaculture and near the surface of S40 where the amount of organic matter is less. These high densities are attributed to a baffling effect created by the fish cages as tidal currents push sediments north in the lagoon.  δ13C and δ15N signatures in the sediments beneath fish cages do not show trends through time and are similar to signatures of terrestrial sources including mangroves. Percent carbon percent nitrogen and percent mud increase through time throughout S43 and S40 though patterns reverse in core S40. The reversal of patterns in core S40 is possibly related to the closure of a southern inlet in 2003. Throughout S9A these same measurements first increase through time but then decrease probably corresponding to the abandonment of fish farms.  In summary aquaculture has affected organic matter content sediment characteristics and foraminiferal distributions in the SEL. However rapid return to pre-aquaculture conditions after the abandonment of S9A and a slower return to pre-aquaculture conditions in S40 likely as a result of tidal flushing suggest that environmental health of the SEL is not particularly compromised by the current scale of floating fish cage aquaculture. 

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Date: 2013
Geology, Aquaculture, Foraminifera, Geochemistry, Malaysia

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