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Ostracods and foraminifera are excellent indicators of environmental change and can act as proxies for the presence of seagrass meadows. These proxies have been under-utilized in vulnerable coastal ecosystems in South-east Asia, and the fundamental habitat and environmental parameters required for such application in environmental monitoring have not yet been established. We investigated the habitat preferences of ostracods and foraminiferal species in seagrass and non-seagrass habitats within Sungai Pulai Estuary (Johor, Malaysia), a system currently undergoing major coastal changes. Samples consisted of surficial and downcore sediments collected from two seagrass meadows and a non-seagrass habitat. Multivariate analysis determined the variations in spatial and depth distribution of the meiofauna. Species dominance, abundance and distribution varied between sites, whereas diversity and community structure varied with sediment depth. We found fewer ostracod individuals (N = 1133) than foraminifera (N = 7242). Ostracods were more species-diverse (H′ = 3.34) in the non-vegetated area compared with seagrass areas (H′ = 2.74), whereas foraminifera species were most diverse (H′ = 3.60) in seagrass areas. Opportunistic species, such as Loxoconcha lilljeborgii, Asterorotalia pulchella, Murrayinella globosa, Ammonia tepida and Elphidium neosimplex dominated the meiofaunal assemblages. The presence of Nummulitidae and Paracyprididae in downcore samples provided information related to rare species and families. Salinity, organic matter and percentage of sand explained much of the meiofaunal distribution. Our findings provide new insight into the factors influencing the presence and distribution of ostracods and foraminifera in the estuary, comprising baseline information for understanding the vulnerability of such habitats to anthropogenic changes.

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Macroalgae (seaweeds) are a major contributor in emitting very short-lived (VSL) bromocarbons into the atmosphere especially in tropical countries with high primary productivity such as Malaysia. Abiotic factors such as light intensities and chlorophyll a concentrations can influence the production of bromocarbons emitted by seaweeds, however, not many studies have systematically quantified their influence on the release rates of VSL bromocarbons. Hence, to measure this, we used a seaweed culture system mimicking a natural environment to study the release rate of VSL bromocarbons (CH 2 Br 2 , CHBr 3 and CHBr 2 Cl) for several red, brown and green seaweeds (Gracilaria changii, Ulva reticulata, Caulerpa racemosa var. macrophysa, Kappaphycus alvarezii, Sargassum binderi, Sargassum siliquosum, and Padina australis. The production of VSL bromocarbons showed a diurnal cycle with halocarbon concentrations increasing to a maximum level at mid-day (1738 pmolL -1 ) and decreasing when light intensity and SST decreased. The production of VSL bromocarbons of seaweeds kept in the sunlight is five times higher than the production of aquaculture tanks placed in dark environments indicating the occurrence of photochemical production. The average photochemical rate for VSL bromocarbons from aquaculture tank experiments ranges from 1 to 137 pmol per g -1 FW -1 h -1 . This makes the red seaweeds (Gracilaria changii) as the highest. Likewise, bromoperoxide (BPO) extracted from all seaweeds also showed the highest activity in red seaweed followed by brown and green seaweed.