Coastal Waters Of Peninsular Malaysia Research Articles

Effects of Urea Removal on the Stable Isotopes δ13C and δ15N in Rays from the Coastal Waters of Peninsular Malaysia

Highlight Research This is the first stable isotopes study of rays from Malaysian waters Urea extraction significantly enriched the δ15N values (‰) Urea removal is obliged for stable isotope studies on rays Such methodological information is critical for marine research in the region Abstract This is the first reported record of stable isotope values for elasmobranch rays within Malaysian waters, and serves as an important baseline methodological information for future studies investigating stable isotope values in both shark and ray species in the region. This study examined the effects of urea removal on the stable isotopes values of δ13C and δ15N in muscle tissues sampled from several elasmobranch rays species, namely Pastinachus atrus, Rhinoptera javanica, Himantura gerrardi, Himantura uarnak and Aetobatus ocellatus. Individual ray species were collected in July and August of 2018, from the coastal waters of Terengganu State, Malaysia. Urea removal was performed by soaking muscle tissue samples in deionised water for at least 24 hours before being dehydrated. The resulting stable isotope values of these samples were compared to samples that did not undergo the urea removal process. Stable isotope values were individual and species-specific, however, the effect of urea removal was significant for δ15N values but did not significantly affect the δ13C values. We conclude that removing urea from elasmobranch samples before stable isotope analysis is advisable to draw correct conclusions about the animal’s diets.

Seasonal changes in abundance of four Acartia species (Copepoda, Calanoida) in the coastal waters of Peninsular Malaysia; relationship with monsoon transition

The seasonal variation of Acartia copepods from the waters of Peninsular Malaysia was studied via monthly observations at 2 fixed stations on the west coast (Pulau Pinang and Port Dickson) and 2 fixed stations on the east coast (Kijal and Penyabong) from October 2012 to March 2014. In situ temperatures recorded during this period were relatively constant (mean 29.6±0.7°C) at all stations. Salinity measurements were also fairly constant (mean 30.3 ± 1.1 PSU) for all stations during this study except at Penyabong where the salinity during the northeast (NE) monsoon season was significantly lower (p<0.05) (mean 23.2 ± 7.9 PSU) than during the southwest (SW) monsoon season. Concentration of chlorophyll a at Pulau Pinang during the SW monsoon period was significantly higher (p<0.05) (mean 14.6±5.4μg/L) than during the NE monsoon period. Four species of Acartia were identified at all stations: A. amboinensis, A. erythraea, A. pacifica and A. spinicauda. At Kijal, Acartia erythraea population was significantly higher (p<0.05) (mean 695.7 ± 618.4 inds/m3) compared with the other stations. Acartia species composition at Port Dickson was similar to Penyabong, while Kijal was similar to Pulau Pinang. Small-sized species, Acartia pacifica and A. spinicauda were dominant at Port Dickson and Penyabong, while the larger-sized species, Acartia amboinensis and A. erythraea were dominant at Kijal. Generalized additive mixed models (GAMMs) were applied to abundance data to describe the environmental preference associated with population recruitment of these species, and the results identified a relative contrast in environmental envelopes occupied by the larger and smaller-sized species. The large-sized species preferred colder and more saline water while the small-sized species preferred warmer and lower salinity water. The succession and co-occurrence of similar sized species is suggested to be a result of the combined effect of species-specific preference to varying temperature–salinity regimes.

FIRST REPORT OF COCHLODINIUM POLYKRIKOIDES (DINOPHYCEAE), A HARMFUL ALGAL BLOOM (HAB) SPECIES IN THE COASTAL WATERS OF PENINSULAR MALAYSIA

Cochlodinium polykrikoides is known as fish killer. In Malaysia this species has been recorded in Kota Kinabalu, Sabah, Borneo Island. To date, C. polykrikoides has not been recorded in Peninsular Malaysia. This study aims to identify the presence of C. polykrikoides in Peninsular Malaysia particularly in Tanjung Piandang, Kuala Kurau and Kuala Gula located in Perak coastal waters and Straits of Tebrau, Johor. Samplings were carried out for three times at each sampling station. Ten litre of water samples were collected for cell enumeration and identification. For identification, plankton samples were identified under light microscope. Nutrients i.e. nitrate, phosphate and ammonia were determined and physico-chemical parameters (pH, temperature, salinity) were also recorded in-situ. Species was identified as C. polykrikoides based on their morphological characteristics. Result showed that C. polykrikoides was presence in high abundance in both Perak coastal waters and Straits of Tebrau at concentration of 2.5 x 103 cells/L and 4.7 x 103 cells/L, respectively. No significant difference was found between cell abundance at these two locations. pH, salinities and temperatures recorded at both locations range between 7.68 – 7.80, 27.23 – 28.03 psu and 29.32 – 30.90 °C, respectively. There was no significant difference in the physico-chemical parameters (p>0.05) between stations. Regression analysis showed no correlations were between cell abundance and physico-chemical parameters and nutrients. The presence of C. polykrikoides in the coastal waters of Peninsular Malaysia indicates that possible mitigation needs to be given attention by the relevant agencies as this species can bring negative impact to aquaculture industry. Keywords: Cochlodinium polykrikoides; fish-cage; Harmful Algal Bloom; Malaysia; Strait of Malacca

Archaeal community structure in the tropical coastal waters of Peninsular Malaysia

In this study, we used a direct cloning method to explore the archaeal diversity at four locations along the Straits of Malacca. Four 16S rDNA clone libraries were constructed with archaeal specific primers (Arc21F and Arc958R) and, in total, 1,074 randomly selected clones were screened by PCR-restriction fragment length polymorphism analysis using three different restriction enzymes (RsaI, CfoI and DdeI). Good’s coverage suggested that >85 % of archaeal sequence types were obtained in our libraries. The majority of the sequences from Port Dickson and Sungai Muar were affiliated to Euryarchaeota, whereas Port Klang and Kuala Selangor clone libraries were dominated by Thaumarchaeota sequences. Phylogenetic analysis of 16S rDNA sequences showed high archaeal diversity, with a Shannon index ranging from 2.16 to 3.24. Using weighted, non-normalized principal coordinate analysis, the archaeal communities of the four sites were clearly separated from each other. We also showed via canonical correspondence analysis that the distribution of archaeal operational taxonomic units could be related to environmental variables (salinity and chlorophyll a).

Food and feeding habits of the seahorses Hippocampus spinosissimus and Hippocampus trimaculatus (Malaysia)

Two seahorse species, Hippocampus spinosissimus and Hippocampus trimaculatus, sampled in east and west coastal waters of Peninsular Malaysia, fed mostly on crustacean prey; small caridean shrimps and amphipods as adults (both species), and copepods and larval meroplankton as juveniles (for H. trimaculatus only). The similar short relative gut length (~0.4) of both species is consistent with a carnivorous diet. Both species are considered specialists in prey selection, focusing on slow-moving epibenthic, hyperbenthic and canopy-dwelling crustaceans that dwell on the mud-sand seabed, or are associated with seagrass or mangrove areas. In this light, seahorses with their juveniles in shallow waters are vulnerable to coastal reclamation and development.

Long-term and short-term variations of Escherichia coli population structure in tropical coastal waters

In this study, monthly and daily samplings were carried out at Klang, an eutrophic estuary, and at Port Dickson, an oligotrophic coastal water system. Escherichia coli concentration was measured via culture method, and the phylogenetic structure of E. coli population was via Clermont typing. Average E. coli concentration at Klang was higher than Port Dickson (t = 2.97, df = 10, p < 0.05), and daily sampling did not show any apparent temporal variation at both sites. At Klang, salinity was inversely correlated with coliform (R 2 = 0.216, df = 25, p < 0.05), suggesting that river flow was a mode of transport for coliform. Although E. coli concentration was higher at the eutrophic site, E. coli population structure at both Klang and Port Dickson were similar and showed neither long-term nor short-term variations. This study showed the predominance of commensal groups A and B1 in tropical coastal waters of Peninsular Malaysia.

Occurrence and distribution of antifouling biocide Irgarol-1051 in coastal waters of Peninsular Malaysia

Emerging booster biocides contamination raises particular attention in the marine ecosystem health. This study provides the baseline data on the occurrence of Irgarol-1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamiono-s-triazine) in the selected coastal water around Malaysia. The maximum detected concentration of Irgarol was 2021ng/L at Klang West, commercial and cargo port. Coral reef Islands (Redang and Bidong) were relatively less contaminated compared to other coastal areas. The temporal variation revealed that only 1% of 28 stations sampled on November, 2011 was above the environmental risk limit of 24ng/L as suggested by Dutch Authorities, while in January and April, 2012; 46% and 92% of the stations were above the limit respectively. The present findings demonstrate the wide detection of novel antifouling materials Irgarol-1051 which advocates the need for proper monitoring and conservation strategies for the coastal resources.

Trace Metals in Muscle, Liver and Gill Tissues of Marine Fishes from Mersing, Eastern Coast of Peninsular Malaysia: Concentration and Assessment of Human Health Risk

Trace metals (Cu, Zn, Cd and Pb) concentrations in muscles, livers and gills of three important marine fishes, Torpedo Scad (Megalaspis cordyla), Sea Catfish (Arius thalassinus) and Belangeri Croaker (Johnius belangeri) were studied using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The samples were collected from Mersing the eastern coastal waters of Peninsular Malaysia. The estimated ranges of Cu, Zn, Cd and Pb concentrations in the muscles, livers and gills of the three fish species were 1.51-3.48, 17.54-28.34, 0.02-0.12 and 0.12-0.15; 15.8-26.0, 80.58-365.1, 2.32-6.14 and 0.57-1.54; 3.04-5.51, 61.63-259.3, 0.03-0.12 and 0.14-2.03 μg g-1 dry weight, respectively. Metal concentrations in the edible parts of the fish were assessed for human consumption according to the Provisional Tolerable Weekly Intake (PTWI) and Provisional Tolerable Daily Intake (PTDI). Generally, levels of metal in muscles were lower than those in livers and gills. Zinc concentration was found to be the highest among the tested metals in all three species. The estimated weekly and daily intakes for the studied metals were far below the PTWI and PTDI limits. Present study reveals that consumption of these fishes from the study area does not pose a risk to human health.

Heavy Metal Concentration in Fishes from the Coastal Waters of Kapar and Mersing, Malaysia

Although fish is a significant source of protein, they are currently affected by rapid industrialization and mechanized agricultural activities, resulting in increased concentrations of heavy metals in fishes. Concentrations of heavy metals, namely, Cd, Cu, Mn, and Zn, were estimated in the muscle, liver, and gills of two commercially important marine fishes, namely, Arius thalassinus and Johnius belangeri. The fish samples were collected from Kapar and Mersing, which are the west and east coastal waters of Peninsular Malaysia, respectively. The results showed that the muscle had the lowest metal concentrations compared with the liver and gills. Among the estimated heavy metal concentrations, those of Zn and Cd were the highest and the lowest, respectively, for both species in muscle, liver and gills. Moreover, our results indicate that A. thalassinus has higher metal concentrations than J. belangeri in both areas. None of the values in the muscles exceeded the standard guideline values and hence would not pose any health hazard to consumers.

Concentrations of Heavy Metals (Cu, Cd, Zn and Ni) and PAHs in Perna viridis Collected from Seaport and Non-seaport Waters in the Straits of Johore

In this study, the ranges of pollutants found in the soft tissues of Perna viridis collected from Kg. Masai and Kg. Sg. Melayu, both located in the Straits of Johore, were 0.85-1.58 μg/g dry weight (dw) for Cd, 5.52-12.2 μg/g dw for Cu, 5.66-8.93 μg/g dw for Ni and 63.4-72.3 μg/g dw for Zn, and 36.4-244 ng/g dry weight for ∑PAHs. Significantly (p < 0.05) higher concentrations of Cd, Cu, Ni, Zn and ∑PAHs in the mussels were found in the water of a seaport site at Kg. Masai than a non-seaport site at Kg. Sg. Melayu population. The ratios of low molecular weight/high molecular weight hydrocarbons (2.94-3.42) and fluoranthene/pyrene (0.43-0.45) in mussels from both sites indicated the origin of the PAHs to be mainly petrogenic. This study has demonstrated the utility of using the soft tissues of P. viridis as a biomonitor of PAH contamination and bioavailability in the coastal waters of Peninsular Malaysia.

Population Characteristics of A. japonicus from the Kedah Coastal Waters of Peninsular Malaysia

The study was an attempt to examine the size frequency distribution, length-weight relationship and morphometric variation of the Acetes japonicus from four different sides of Kedah coastal waters between March to May 2007 by using SPSS and PRIMER software. The average total length of the females from Batu Lintang and male of Tg. Dawai were the highest with the values of 17.07 and 13.93 mm, respectively. The growth co-efficient (b) values ranged between 2.0 to 4.0, indicating varieties of the growth pattern (negative allometric, isometric and positive allometric) for A. japonicus. The highest correlation of length-length relationship in female and male were found in the population of Kuala Sala. The morphological characteristics showed variation among populations. The highest similarity of morphometric characteristics was between Batu Lintang and Tg. Dawai for all groups (female, male, combined sexes).

Relative Contribution of Viral Lysis and Grazing to Bacterial Mortality in Tropical Coastal Waters of Peninsular Malaysia

We investigated the relative importance of viral lysis and heterotrophic nanoflagellate (HNF) grazing in bacterial mortality as part of a study to understand the microbial loop functioning in tropical waters of Straits of Malacca and South China Sea above the Sunda Shelf. Bacterial abundance ranged from 0.8 × 106 to 2.9 × 106 cells ml-1 and bacterial production ranged from 0.7 × 105 to 4.2 × 105 cells ml-1 hr-1. HNF and viral abundance ranged from 0.6 × 103 to 10.1 × 103 cells ml-1 and 0.3 × 107 to 1.4 × 107 virus particles ml-1, respectively. HNF grazing rates were from 1.1 × 104 to 16.8 × 104 cells ml-1 hr-1, whereas viral lysis rates ranged from 0.7 × 104 to 3.9 × 104 cells ml-1 hr-1. There was predator-prey coupling across the stations with both viral lysis and HNF grazing rates significantly correlated with bacterial production. HNF grazing accounted for 26.1% ± 14.6 of bacterial production, whereas viral lysis was 9.0% ± 3.5 of bacterial production. Bacterial mortality by both HNF and viruses averaged 35.5% ± 13.9, and was outpaced by bacterial production. Other loss factors, such as grazing by ciliates, sedimentation, benthic filter feeders, autolysis, or predatory bacteria, could be important.

Investigating the decay rates of Escherichia coli relative to Vibrio parahemolyticus and Salmonella Typhi in tropical coastal waters

Using the size fractionation method, we measured the decay rates of Escherichia coli, Salmonella Typhi and Vibrio parahaemolyticus in the coastal waters of Peninsular Malaysia. The size fractions were total or unfiltered, <250 μm, <20 μm, <2 μm, <0.7 μm, <0.2 μm and <0.02 μm. We also carried out abiotic (inorganic nutrients) and biotic (bacterial abundance, production and protistan bacterivory) measurements at Port Dickson, Klang and Kuantan. Klang had highest nutrient concentrations whereas both bacterial production and protistan bacterivory rates were highest at Kuantan. We observed signs of protist–bacteria coupling via the following correlations: Protistan bacterivory−Bacterial Production: r = 0.773, df = 11, p < 0.01; Protist−Bacteria: r = 0.586, df = 12, p < 0.05. However none of the bacterial decay rates were correlated with the biotic variables measured. E. coli and Salmonella decay rates were generally higher in the larger fraction (>0.7 μm) than in the smaller fraction (<0.7 μm) suggesting the more important role played by protists. E. coli and Salmonella also decreased in the <0.02 μm fraction and suggested that these non-halophilic bacteria did not survive well in seawater. In contrast, Vibrio grew well in seawater. There was usually an increase in Vibrio after one day incubation. Our results confirmed that decay or loss rates of E. coli did not match that of Vibrio, and also did not correlate with Salmonella decay rates. However E. coli showed persistence where its decay rates were generally lower than Salmonella.

Use of Different Tissues of Perna Viridis as Biomonitors of Polycyclic Aromatic Hydrocarbons (PAHs) in the Coastal Waters of Peninsular Malaysia

For the first time, in May 2007, the distributions of polycyclic aromatic hydrocarbons (PAHs) were studied in the soft tissues (STs) (mantle, gills, foot, gonad, muscle, byssus, and remaining soft tissues) of the green-lipped mussel Perna viridis, collected from eight geographic locations along the coastal waters of peninsular Malaysia. The STs of the mussels collected from the eastern part of the Johore Straits indicated higher bioavailability of and contamination by PAHs than from other areas. The results also indicated a significantly higher concentration of the lower molecular weight (LMW) PAHs in tissues compared to that of the higher molecular weight (HMW) PAHs, perhaps due to the greater bioavailability of the more water-soluble LMW PAHs or related to a partial biotransformation of the higher molecular weight PAHs. The results also suggest that the differences found in the contents of PAHs in various STs of P. viridis were mainly due to differences between individual PAHs volatility and solubility in water, as well as the mechanism of PAH accumulation by mussels. Of the STs in general, the gonad was shown to contain the highest levels of PAHs, but it is not a potential biomonitoring organ because it is highly influenced by spawning conditions. Isomeric PAH ratios were used to differentiate pollution sources.The findings of the study suggest that STs of P. viridis are good biomonitors of the bioavailability and contamination with PAHs in tropical coastal waters.

Interspecific variation of heavy metal concentrations in the different tissues of tropical intertidal gastropods from Malaysia

The present study aims to determine the concentrations of Cd, Cu, Fe, Ni, Pb, and Zn in the different tissues of five species of tropical intertidal gastropods from Malaysia. Each of the species have organs/tissues that highly accumulated certain metals. For Cu, the mantles of Cerithidea obtusa, Pugilina cochlidium, and Murex trapa; and the digestive caeca of Thais sp. and Chicoreus capucinus highly accumulated Cu. The shells of Chi. capucinus and M. trapa, the digestive caeca of P. cochlidium, and the digestive glands of Thais sp. and Chi. capucinus highly accumulated Cd. The tentacles and the digestive caeca of Cer. obtusa and P. cochlidium, respectively, highly accumulated Zn, the digestive glands of Thais sp., Chi. capucinus, and M. trapa also highly accumulated Zn. The shells of most of the gastropods accumulated high levels of Pb and Ni. The opercula of most of the gastropods, besides the digestive glands for Thais sp., accumulated high levels of Fe. The present study on interspecific variations of heavy metals in gastropods provided information on differences of metal distributions in the different tissues, which could be useful in proposing potential tissues as better biomonitoring tools of heavy metal bioavailabilities in the coastal waters of Peninsular Malaysia.

Spatial distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in green mussels (Perna viridis) from coastal areas of Peninsular Malaysia: implications for source identification of perylene

Distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in green mussels (Perna viridis) from various sites in coastal waters of Peninsular Malaysia between August 2004 and January 2007, in order to assess contamination by petroleum hydrocarbons. The range of ∑PAHs detected in mussels was from 766 to 110500 (ng/g lipid wt.). High concentrations of PAHs were found in mussel tissues collected near Penang Bridge. The ratios of methyl phenanthrenes to phenanthrene (∑MP/P ratio) for Penang, Kg. Pasir Puteh and Tebing Runtuh (Johore Straits) were greater than 2, indicating extensive input of petrogenic PAHs. The results indicated that male individuals elevated more considerable concentrations of PAHs in their soft tissues in comparison to female individuals. The results of independent sample T-test showed that there were no significant differences (p > 0.05) between male and female mussels analysed in the Pasir Panjang station. Negative significant correlations (r = −0.890, p < 0.01) and (r = −0.0655, p < 0.05), were found between weight and total of PAHs in female and male species, respectively. This indicated that body weight of each individual was not affected by the PAHs concentrations. The present study proposes the use of soft tissue of Perna viridis as a biomonitor of perylene bioavailability and contamination in coastal waters of Peninsular Malaysia.

Temporal Variation of Bacterial Respiration and Growth Efficiency in Tropical Coastal Waters

We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5 degrees C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 microM, whereas DON ranged from 0 to 32 microM. Bacterial respiration ranged from 0.5 to 3.2 microM O2 h(-1), whereas bacterial production ranged from 0.05 to 0.51 microM C h(-1). Bacterial growth efficiency was calculated as bacterial production/(bacterial production + respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r2 = 0.169, df = 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r2 = 0.137, df = 32, and P = 0.03) and temperature (r2 = 0.113, df = 36, and P = 0.04). Substrate quality was the most important factor (r2 = 0.119, df = 33, and P = 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 microM C h(-1). When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r2 = 0.341, df = 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs.

Isolation and characterization of culturable bacteria from tropical coastal waters

In this study we isolated and characterized some culturable bacteria from tropical coastal waters of Peninsular Malaysia. We obtained between 0.23 and 1.85 × 103 cfu mL–1 in the Zobell 2216E medium, and cultured 0.04% to 0.12% of total bacterial counts. Different bacterial strains were then selected by 16S rDNA RFLP using four restriction enzymes (DdeI, HhaI, RsaI, and Sau3AI), of which HhaI gave the most RFLP patterns. A total of 54 unique strains were obtained and these were identified by their 16S rDNA gene sequence. These bacterial strains could be divided into five classes: 38 strains of γ-Proteobacteria (61.1%); 3 strains of α-Proteobacteria (5.5%); 2 strains of the Cytophaga-Flavobacterium-Bacteroides group (3.7%); 3 strains of high GC, Gram-positive bacteria (5.5%); and 13 strains of low GC, Gram-positive bacteria (24.1%). These isolates have good potential for further biotechnological studies since about 56% of the isolates exhibited amylase activity, whereas 36% and 18% of the isolates had protease and lipase, respectively. Most (&gt;70%) of the isolates also produced poly-ß-hydroxybutyrate.

Contamination Profiles of Antifouling Biocides in Selected Coastal Regions of Malaysia

The concentrations of butyltins (BTs) in sediment from Peninsular Malaysia along the Strait of Malacca and their spatial distribution are discussed. The concentrations of BTs were high in the southern part of Peninsular Malaysia where there is a lot of ship traffic, because trade is prosperous. The concentrations of monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) in sediment from the coastal waters of Peninsular Malaysia were in the range 4.1-242 microg/kg dry weight (dw), 1.1-186 microg/kg dw, and 0.7-228 microg/kg dw, respectively. A higher percentage of TBT was observed in the area where TBT concentrations were high. The concentrations of monophenyltin (MPT), diphenyltin (DPT), and triphenyltin (TPT) were in the range <0.1-121 microg/kg dw, 0.4-27 microg/kg dw, and 0.1-34 microg/kg dw in sediment from Peninsular Malaysia, respectively. MPT was the dominant phenyltin species. MBT, DBT, and TBT in green mussel (Perna viridis) samples were detected in the range 41-102 microg/kg, 3-5 microg/kg, and 8-32 microg/kg, respectively. A tolerable average residue level (TARL) was estimated at 20.4 microg/kg from a tolerable daily intake (TDI) of 0.25 microg TBTO/kg body weight/day. The maximum value of TBT detected in green mussel samples was the value near the TARL. TPTs were not detected in green mussel samples. The concentrations of Diuron and Irgarol 1051 in sediment from Peninsular Malaysia were in the range <0.1-5 microg/kg dw and <0.1-14 microg/kg dw, respectively. High concentrations of these compounds were observed in locations where the concentrations of TBT were high. Sea Nine 211, Dichlofluanid, and Pyrithiones were not detected in sediment. The concentrations of antifouling biocides in Melaka and the Strait of Johor were investigated in detail. BTs were found in similar concentrations among all sampling sites from Melaka, indicating that BT contamination spread off the coast. However, Sea Nine 211, Diuron, and Irgarol 1051 in the sediment from Melaka were high at the mouth of the river. BT concentrations at the Strait of Johor were higher than those in Peninsular Malaysia and Melaka and were high at the narrowest locations with poor flushing of water. The concentrations of antifouling biocides were compared among Malaysia, Thailand, and Vietnam. A higher concentration and wide variations of TBT and TPT in sediment from Malaysia were observed among these countries. The Irgarol 1051 concentrations in sediment from Malaysia were higher than those in Thailand and Vietnam.

Bacterial abundance and production, and their relation to primary production in tropical coastal waters of Peninsular Malaysia

In the present study, the relationship between bacteria and phytoplankton in tropical coastal waters was investigated. The bacterial abundance, bacterial production, chlorophyll a concentration and net primary production were measured at several locations in the coastal waters of Peninsular Malaysia. Chlorophyll a concentration ranged from 0.40 to 32.81 μg L–1, whereas bacterial abundance ranged from 0.1 to 97.5 × 106 cells mL–1. Net primary production ranged from 8.49 to 55.95 μg C L–1 h–1, whereas bacterial production ranged from 0.17 to 70.66 μg C L–1 h–1. In the present study, the carbon conversion factor used to convert bacterial production (cells mL–1 h–1) into carbon units ranged from 10 to 32.8 fg C cell–1, and was estimated from the bacterial size distribution measured at each location. Both phototrophic and heterotrophic biomass (bacteria–chlorophyll a) and activity (bacterial production–net primary production) were significantly correlated, although their correlation coefficients (r2) were relatively low (r2 = 0.188 and r2 = 0.218 respectively). Linear regression analyses provided the following equations to represent the relationship between: bacteria and chlorophyll a (Chl a), log Bacteria = 0.413 log Chl a + 6.057 (P = 0.003); and between bacterial production (BP) and net primary production (NPP), log BP = 0.896 log NPP – 0.394 (P = 0.004), which fitted with published results well. Comparison of annual carbon fluxes confirmed the prevalence of net heterotrophy in these coastal waters, and together with the low correlation coefficients, suggested the role of allochthonous organic matter in supporting heterotrophic activity.