Johor Strait Research Articles

ASSESSMENT OF HEAVY METAL ACCUMULATION IN THE STRAITS OF JOHOR: A COMPREHENSIVE STUDY ON WATER, SEDIMENT, AND AQUATIC ORGANISMS

The purpose of this study was to evaluate the Johor Straits' marine water quality in the vicinity of Kampung Pasir Putih. Aquatic life and aquaculture operations are at risk due to the negative consequences of land use changes and increased discharge of household, agricultural, and industrial waste, as the investigation found. The distribution and concentration levels of heavy metals (Zn, Cu, Cd, and Pb) in crabs, mussels, and sediment samples were particularly investigated in this study. For Zn, Cu, Cd, and Pb, the corresponding mean concentration values in the entire body of the crabs and mussels were 60.4 to 256.5 mg/g, 21.8 to 50.3 mg/g, 1.6 to 4.5 mg/g, and 8.2 to 23.7 mg/g dry weight. Zn and Cu continuously had greater concentrations than the other elements, although the distribution patterns of these metals differed between sampling stations. The average amounts of heavy metals in the sediment samples ranged from 17.7 to 147.1 mg/g, 17.7 to 155 mg/g, 2.4 to 5.3 mg/g, and 9.8 to 14.5 mg/g dry weight for zinc, copper, lead, and mercury, in that order. The study showed that when development increases, water quality decreases and marine organisms accumulate more heavy metals. The range of dissolved oxygen (DO) concentrations, varying from 1.36 to 6.71 mg/L, exhibited a correlation with the accumulation of heavy metals.

The Macrobenthos Diversity and Dominance in Johor Straits, Malaysia

The Macrobenthos Diversity and Dominance in Johor Straits, Malaysia

Progress in Research on Microplastic Prevalence in Tropical Coastal Environments: A Case Study of the Johor and Singapore Straits

Microplastics are contaminants in marine ecosystems, posing great threats to biota and human health. In this work, we provide an overview of the progress made in understanding microplastic prevalence in tropical coastal environments, focusing on the Johor and the Singapore Straits as a case study. We examine the sources, distribution, transport, and ecological impact of microplastic pollution in this region through a systematic review. All papers relating to marine microplastics in Singapore’s sand and benthic sediments, seawater, and marine biota were used for analysis, from 2004 to 2023. In addition, we discuss the influence of envi-ronmental factors such as coastal morphology and anthropogenic activities on patterns of microplastic accumulation. We emphasize that microplastic pollution is more prevalent along the eutrophic Johor Strait compared to the Singapore Strait due to hydrological conditions. Rainfall is also a key factor that influences mi-croplastic abundance during the monsoon seasons. Furthermore, the bacterial and plankton assemblages of organisms on microplastic surfaces are diverse, with eutrophic waters enhancing the diversity of organisms on microplastic surfaces. Novel harmful cyanobacteria and bloom species of phytoplankton were also found on microplastic surfaces. By synthesizing existing research findings and highlighting regional characteristics, this paper contributes to ongoing efforts to mitigate microplastic pollution in tropical regions.

Distribution of nutrients and dissolved organic matter in a eutrophic equatorial estuary: the Johor River and the East Johor Strait

Abstract. Estuaries have strong physicochemical gradients that lead to complex variability and often high rates of biogeochemical processes, and they are also often impacted by humans. Yet, our understanding of estuarine biogeochemistry remains skewed towards temperate latitudes. We examined seasonal and spatial variability in dissolved organic matter (DOM) and nutrients along a partly eutrophic, agricultural–urban estuary system in Southeast Asia: the Johor River and the East Johor Strait. Dissolved organic carbon (DOC) and coloured DOM (CDOM) showed non-conservative mixing, indicating significant DOM inputs along the estuary. The CDOM spectral slopes and CDOM : DOC ratios suggest that terrigenous, soil-derived DOM dominates along the Johor River, while phytoplankton production and microbial recycling are important DOM sources in the Johor Strait. CDOM properties were not unambiguous source indicators in the eutrophic Johor Strait, which is likely due to heterotrophic CDOM production. Nitrate concentrations showed conservative mixing, while nitrite concentrations peaked at intermediate salinities of 10–25. Ammonium concentrations decreased with salinity in the Johor River but increased up to 50 µmol L−1 in the Johor Strait, often dominating the dissolved inorganic nitrogen (DIN) pool. Phosphate concentrations were low (<0.5 µmol L−1) throughout the Johor River but increased in the Johor Strait, where DIN : phosphate ratios were typically ≥ 16 : 1. This suggests that the Johor Strait may experience phosphorus limitation and that internal recycling is likely important for maintaining high nutrient concentrations in the Johor Strait. Overall, our results indicate that the Johor River and Johor Strait are clearly not part of the same estuarine mixing continuum and that nutrient recycling processes must be quantified to understand nutrient dynamics in the Johor Strait. Moreover, our results highlight the need for better techniques for DOM source tracing in eutrophic estuaries.

A synopsis of the Tanaidacea (Crustacea: Peracarida) of Singapore, with a review of tanaidacean diversity in Southeast Asia and the South China Sea

In the first comprehensive taxonomic study of the tanaidacean fauna of Singapore, a total of 23 species belonging to two suborders, three superfamilies, 13 families and 22 genera were identified from approximately 2,400 specimens, including 11 species that are possibly new to science. This material was collected from various localities in Singapore waters, from the intertidal zone to subtidal habitats up to 91 m in depth. Many species exhibited a narrow bathymetric distribution and strong affiliation to certain habitats or microhabitats such as mudflats, coral reefs, and barnacle shells on rocky shores. The Singapore Strait yielded 20 tanaidacean species, almost thrice the number of species (7) present in the Johor Straits. Three species were confined to the brackish waters in the inner parts of the Johor Straits and Sungei Pandan. Furthermore, a total of 153 tanaidacean species has now been recorded from Southeast Asia and the South China Sea. The presence of the family Numbakullidae in this region is also documented for the first time.

Microplastic contamination in the sediment of the Johor Strait Estuary, Malaysia

The issue of microplastics has garnered significant attention in light of their potential environmental hazards and possible health effects on higher trophic organisms and humans. However, the available information is restricted and knowledge about the interaction between microplastics in aquatic sediments and the microplastic-related impacts of aquaculture activities, and this area has not yet been adequately researched. This research looks at the occurrence and properties of microplastics in the bed sediment from Perna veridis aquaculture activity areas, in the Strait of Johor, Malaysia. Bed sediments were collected in replicates from five sampling sites using a box corer (Wildco). The extracted organic matter was digested with 30% hydrogen peroxide (H2O2) before being separated using NaCl and ZnCl solutions. The inspection of plastic debris was conducted via a Stereomicroscope (HSZ-600) at magnifications ranging from 40x to 45x and considered according to morphology, size, and colour. Microplastic polymers were validated using Attenuated Total Reflection Fourier Transferred Infra-Red (ATR-FTIR) spectroscopy. The sediment samples exhibited a varying range of microplastic abundance, with values ranging from 29 to 60 particles/kg.d.w. Microplastics within the size range of 101-500μm (63%) predominated in all samples collected, with fragments (79%) and fibres (18%) being the main morphologies of MPs found. The dominant particles found in the sediment were polypropylene (PP) and polyamide. The findings suggest that aquaculture practises may have an impact on the presence of microplastics (MPs) in bottom sediment, as these locations are well-known aquaculture areas for Perna veridis.

A comparative eco toxicological study of heavy metal concentrations in mussels collected in 2004 from the western and eastern coastal waters in the straits of Johore

The concentrations of Cu, Cd, Zn, Pb, Ni and Fe in the different soft tissues of Perna viridis from the west and east coast of The Straits of Johore (SOJ) were determined. Crystalline style (CS) recorded higher accumulation of Cu (west: 58.2 mg/kg dry weight; east: 56.0 mg/kg dry weight), Cd (west: 9.45 mg/kg dry weight; east: 3.93 mg/kg dry weight), Pb (west: 49.5 mg/kg dry weight; east: 7.07 mg/kg dry weight) and Ni (west: 40.0 mg/kg dry weight; east: 20.2 mg/kg dry weight) than those other soft tissues. Byssus meanwhile recorded high levels of Zn (west: 173 mg/kg dry weight; east: 193 mg/kg dry weight) and Fe (west: 3213 mg/kg dry weight; east: 1221 mg/kg dry weight). By comparing the accumulation of heavy metal concentrations in all the eight tissues, CS and byssus recorded the highest accumulation of heavy metals among all tissues, followed by other tissues namely foot, gill, gonad, mantel, muscle and remainder, which recorded relatively low level on heavy metal concentrations. Generally, the soft tissues recorded higher heavy metal concentrations on the east coast than on the west coast of the SOJ. This indicated a high bioavailability and contamination of the potentially toxic heavy metals on the east coast which was due to various human activities.

Heavy metal speciation in surface sediments and their impact on the bioaccumulation of green mussels (Perna viridis) from the eastern part of the Straits of Johor, Malaysia

Heavy metal speciation in surface sediments and their impact on the bioaccumulation of green mussels (Perna viridis) from the eastern part of the Straits of Johor, Malaysia

The Johor–Singapore Causeway: Celebrating and conceptualising its centenary

The Johor–Singapore Causeway was inaugurated on 28 June 1924. With this, Singapore became physically connected to the Malay Peninsula via a 1,056-metre-long raised track across the Johor Strait. Since then, this understated piece of infrastructure has come to underpin many aspects of life in Singapore and Malaysia. Before the COVID-19 pandemic, an estimated 300,000 people crossed between Malaysia and Singapore via the Causeway every day, making it one of the busiest border crossings in the world, and perhaps the busiest of all in Southeast Asia. The reasons for this transborder travel included daily commutes for work, access to education and health services, as well as shopping and leisure. In addition, people crossed the Causeway to then use either Singapore or Johor as a gateway to destinations further afield. While the pandemic curtailed almost all cross-border movement of people, as of early 2023 trips across the Causeway were approaching their pre-COVID-19 levels.

The assessment of shoreline changes along the Johor Strait using Sentinel-1 synthetic aperture radar imagery and GIS

ABSTRACT This paper presents a robust approach for shoreline detection using the K-Means clustering and the Digital Shoreline Analysis System developed by the United States Geological Survey. The shoreline changes along the Johor Straits of Malaysia are assessed by using the multi-temporal Sentinel-1 Synthetic Aperture Radar images from 2018 to 2022. This area is known to be important for both socioeconomic activities. The retrieved shorelines are found reliable with a good accuracy of 1.4 m when validating against the Global Positioning System rapid static survey. This merits finding a robust approach that goes beyond the normal practice in Malaysia where manual digitization is usually exercised. The rate of change is calculated by using the end point rate (EPR) for providing a short-term (annual) rate of change while using the linear regression rate (LRR) for providing a long-term (5 year) rate of change. Based on the EPR, the mean annual changes are approximately 10 m/yr for erosion and up to 9.83 m/yr for accretion; meanwhile, the mean of 5-year changes based on the LRR is 62% and 37% for erosion and accretion, respectively. This study reveals that 10 out of 12 sites along Johor Strait are categorized as ‘high’ erosion, two locations are categorized as ‘medium’ erosion and none are as ‘low’ erosion.

Frequent pulse disturbances shape resistance and resilience in tropical marine microbial communities

The Johor Strait separates the island of Singapore from Peninsular Malaysia. A 1-kilometer causeway built in the early 1920s in the middle of the strait effectively blocks water flowing to/from either side, resulting in low water turnover rates and build-up of nutrients in the inner Strait. We have previously shown that short-term rather than seasonal environmental changes influence microbial community composition in the Johor Strait. Here, we present a temporally-intensive study that uncovers the factors keeping the microbial populations in check. We sampled the surface water at four sites in the inner Eastern Johor Strait every other day for two months, while measuring various water quality parameters, and analysed 16S amplicon sequences and flow-cytometric counts. We discovered that microbial community succession revolves around a common stable state resulting from frequent pulse disturbances. Among these, sporadic riverine freshwater input and regular tidal currents influence bottom-up controls including the availability of the limiting nutrient nitrogen and its biological release in readily available forms. From the top-down, marine viruses and predatory bacteria limit the proliferation of microbes in the water. Harmful algal blooms, which have been observed historically in these waters, may occur only when there are simultaneous gaps in the top-down and bottom-up controls. This study gains insight into complex interactions between multiple factors contributing to a low-resistance but high-resilience microbial community and speculate about rare events that could lead to the occurrence of an algal bloom.

Lower Health Risks of Potentially Toxic Metals after Transplantation of Aquacultural Farmed Mussels from a Polluted Site to Unpolluted Sites: A Biomonitoring Study in the Straits of Johore.

The present field-based study aimed to determine the levels of six potentially toxic metals (PTM)s (Cd, Cu, Fe, Ni, Pb, and Zn determined using a flame atomic-absorption spectrophotometer) using transplanted green-lipped mussel Perna viridis from a polluted site at Kampung Pasir Puteh (KPP) to unpolluted sites at Kampung Sungai Melayu (KSM) and Sungai Belungkor (SB) in the Johore Straits (SOJ), and to estimate the human health risks of the PTMs after the depuration periods. Interestingly, after 10 weeks of depuration in the two unpolluted sites, there were 55.6-88.4% and 51.3-91.7% reductions of the six PTMs after transplantation from KPP to SB and KSM, respectively. Lower risks of health assessments were recorded and judged on the present findings of significantly (p < 0.05) lower levels of safety guidelines, significantly (p < 0.05) lower values of target hazard quotient, and significantly (p < 0.05) lower values of estimated weekly intake, of all the six PTMs after 10 weeks of depuration of the transplanted polluted mussels to the two unpolluted sites in the SOJ. Thus, further reducing the noncarcinogenic risks of the PTMs to the consumers. From an aquacultural point of view, this depuration technique can be recommended to reduce the health risks of PTMs to mussel consumers.

A brief overview of the issues faced by Harmful Algal Blooms along Johor straits

Urbanization of coastal areas worldwide has increased due to an increase in the global population. The production of sustainable aquaculture is greatly impacted by a surge of this urbanization. In certain countries, particularly for individuals with more limited space in metropolitan areas, such as along Johor’s coastal area, aquaculture might well be a good strategy to maintain food availability (continuous production plus high-quality meals). Consequently, the adoption of aquaculture along the Johor’s coastal area has lead to Harmful Algal Blooms (HAB). This paper examines the evolution of the aquaculture industry of Malaysian Johor coastal areas in relation to HABs. In addition to HABs, the aforementioned metropolitan regions confront diverse economic and geographical obstacles when attempting to increase their aquaculture production sustainably. Those problems are therefore addressed using a variety of operations as well as surveillance techniques in this brief overview. Lockdowns and border prohibitions caused by the continuous COVID-19 infection have had a global impact. These logistical difficulties in the seafood industry have increased dependency on imported supplies. It is suggested that international decision- making, supervision, and knowledge exchange can successfully solve the challenges urbanized areas have in ensuring sustainable food security through the evolution within the aquaculture sector.

Molecular Detection of the Harmful Raphidophyte Chattonella subsalsa Biecheler by Whole-Cell Fluorescence in-situ Hybridisation Assay.

Species of the genus Chattonella (Raphidophyceae) are a group of marine protists that are commonly found in coastal waters. Some are known as harmful microalgae that form noxious blooms and cause massive fish mortality in finfish aquaculture. In Malaysia, blooms of Chattonella have been recorded since the 1980s in the Johor Strait. In this study, two strains of Chattonella were established from the strait, and morphological examination revealed characteristics resembling Chattonella subsalsa. The molecular characterization further confirmed the species' identity as C. subsalsa. To precisely detect the cells of C. subsalsa in the environment, a whole-cell fluorescence in-situ hybridisation (FISH) assay was developed. The species-specific oligonucleotide probes were designed in silico based on the nucleotide sequences of the large subunit (LSU) and internal transcribed spacer 2 (ITS2) of the ribosomal DNA (rDNA). The best candidate signature regions in the LSU-rRNA and ITS2-rDNA were selected based on hybridisation efficiency and probe parameters. The probes were synthesised as biotinylated probes and tested by tyramide signal amplification with FISH (FISH-TSA). The results showed the specificity of the probes toward the target cells. FISH-TSA has been proven to be a potential tool in the detection of harmful algae in the environment and could be applied to the harmful algal monitoring program.

Byssus of Green-Lipped Mussel Perna viridis as a Biomonitoring Biopolymer for Zinc Pollution in Coastal Waters.

The present study aimed to confirm the use of the byssus (BYS) of the green-lipped mussel Perna viridis as a biomonitoring biopolymer for zinc (Zn) by comparing it to copper (Cu) and cadmium (Cd) pollution in coastal waters under experimental field conditions, based on the transplantation of caged mussels between polluted and unpolluted sites in the Straits of Johore (SOJ). Four important evidential points were found in the present study. First, the 34 field-collected populations with BYS/total soft tissue (TST) ratios > 1 indicated that the BYS was a more sensitive, concentrative, and accumulative biopolymer for the three metals than TST. Significant (p < 0.05) and positive correlations between BYS and TST in terms of the levels of the three metals were observed. Second, the data obtained in the present study were well-supported by the interspecific comparison, which indicated that the BYS of P. viridis was a significantly better biomonitoring biopolymer for the identification of coastal areas exposed to Zn, Cd, and Cu pollution and played the role of an excretion route of metal wastes. Third, the higher positive correlation coefficients for the metals between the BYS sedimentary geochemical fractions than the TST sedimentary geochemical fractions indicated that the BYS was more reflective of metal bioavailability and contamination in coastal waters. Fourth, and most importantly, the field-based cage transplantation study clearly indicated the accumulation and elimination of the three metals by the BYS in both polluted and unpolluted sites in the Straits of Johore. In sum, the BYS of P. viridis was confirmed as a better biopolymer than TST for Zn, as well as Cd and Cu, bioavailability and contamination in tropical coastal waters.

Spatial and Temporal Assessment of Marine Water Quality using Statistical Approaches

The study was carried out to determine the classes and parameters that influence the water quality in the Straits of Johor using the Marine Water Quality Index (MWQI) method and the multi-variable statistical analysis, namely Principal Component Analysis (PCA). The MWQI method classifies the data sets according to four classes of contaminated, medium, good and very good classes. The data were studied from 2016 to 2017 according to two monsoon seasons - the northeast and southwest monsoons. The results for both seasons were compared to find out the difference. The results of the PCA analysis show the relationships between the parameters studied and determine which parameters are responsible for changing water quality standards. The results of the MWQI method reveals that all stations except WQ14 is in class 3 which is moderated while only WQ14 is in class 4 (contaminated). In terms of monsoon, the results of the analysis at the southwest monsoon station found that 25 out of 35 data were in class 3 while the other 10 were in class 4. In addition, MWQI analysis on the northeast monsoon found that 34 out of 35 data were in class 3 and only one was in class 4. These results show that the water quality in the northeast monsoon is better than in the southwest monsoon. The results from the PCA analysis indicates that fecal coliform, total suspended solids and phosphate influence the water quality at the southwest station while the dissolved oxygen and phosphate parameters influence the water quality at the northeast station due to high positive load values. In conclusion, MWQI was able to determine the class of water whilst PCA allowed the identification of types of parameters that affect the water quality. In conclusion, the two above methods can be used to determine pollution levels in water bodies.

Dugongs (Dugong dugon) along hyper-urbanized coastlines

Coastal development and the increased anthropogenic use of sea spaces have rapidly degraded coastal habitats throughout Southeast Asia. We study how these activities impact dugong (Dugong dugon) population(s) along hyper-urbanized coastlines of the Johor and Singapore Straits through literature reviews and field surveys. Our review recovered sixty-nine live observations and carcass observations of dugongs between 1820 and 2021. The eastern Johor Strait is identified as a dugong hotspot. We observed peaks in observations coincident with the Northeast and Southwest monsoons. Distribution patterns of dugong observations were likely driven by a combination of natural and anthropogenic factors such as seasonality in seagrass abundance, tidal cycles, wind patterns and vessel traffic. Our field surveys ascertained active foraging sites along the anthropogenically disturbed Johor Strait and western Singapore Strait. Evident from our study is the importance of reef-associated seagrass meadows as refugia for foraging dugongs along areas of high anthropogenic use. This study provides an ecological baseline for dugong research along the Johor and Singapore Straits—within the data-poor western Malay Archipelago—, and aids in the design of sustainable management strategies and conservation programs for dugongs along areas where urbanization is commonplace.

Diversity of &lt;i&gt;Heterocapsa&lt;/i&gt; (Dinophyceae) and the algal bloom event in the mariculture areas of Johor Strait, Malaysia

In November 2020, a high biomass multi-species algal bloom caused heavy water discoloration in the fish and mussel farm areas of the Johor Strait, Malaysia. A total of 19 microalgal taxa were identified from the plankton samples collected during the bloom event. Eleven genera were diatoms, and eight genera were dinophytes. The microalgal composition was dominated by the diatom Guinardia sp., with an average cell density of 1.7×106 cells L−1, making up 65–80% of the phytoplankton composition. Concomitantly, high densities of the dinophytes Heterocapsa minima (3.8–5.3×105 cells L−1) and Karlodinium spp. (3.5–6.6×103 cells L−1) were found. This is the first record of the occurrence of H. minima in Malaysian waters. Detailed morphological observations of H. minima based on scanning electron microscopy are presented in this study. To have a better insight into the Heterocapsa species assemblages in the Johor Strait, the diversity of Heterocapsa species assemblages along the strait was investigated based on a metabarcoding approach. Environmental DNA collected between 2018 and 2019 was used for high throughput amplicon sequencing targeting the small subunit (SSU) ribosomal RNA gene marker. The metabarcoding analysis detected three rare Heterocapsa species in the waters, H. niei, H. rotundata, and H. steinii. The results showed that Heterocapsa species assemblages varied temporally across the strait, with higher species diversity and amplicon sequence variant (ASV) read abundances detected in the Eastern Johor Strait. Although no fish/shellfish kills were sighted during the 2020 bloom event, the presence of harmful microalgal species, such as Heterocapsa minima and Karlodinium spp., urged the need for a comprehensive HAB monitoring program in the Strait to safeguard the aquaculture industry in the areas.

Coastal land-use mapping along Johore Straits using Sentinel 1-SAR data with maximizing parameterization of machine learning classification

In tropical regions, cloud cover accounts for a major obstacle to detect the coastal land-use while adopting remote sensing technology. The advent of the latest Sentinel-1 C-band synthetic aperture radar (SAR) satellite provides advantages to collect data in all-weathered conditions. In this study, Sentinel-1 images are processed using Lee filter and GLCM-Mean texture analysis in order to enhance the classification results. Several sets of parameters have been tested and these resulted in the optimum overall accuracy by Neural Network with 79.00% in 2015 and 68.29% in 2019. In contrast, Support Vector Machine classifiers obtained overall accuracies of 77.44% and 71.26% in 2015 and 2019 respectively. The results were accessed and it is found that Support Vector Machine outperforms the Neural Network classifier in discriminating data with high heterogeneity properties. Besides, Support Vector Machine has more consistent results in parameter testing compared to Neural Network.

Spatial-temporal variability of microphytoplankton assemblages including harmful microalgae in a tropical semi-enclosed strait (Johor Strait, Malaysia)

Harmful algal blooms (HABs) were not new to the tropical semi-enclosed Johor Strait, with incident records that could trace back to the 1980s. HAB monitoring in the area, often, is reactive, focusing only on HAB taxa previously causing problems but neglecting potential emerging HABs. To develop datasets on HABs that can better inform and improve management practices, monitoring should expand to sample whole microphytoplankton communities. In this study, microphytoplankton community structure across the Strait was investigated. Abundances of microphytoplankton and a suite of in situ water parameters of temperatures, salinity, pH, dissolved oxygen levels, macronutrients, and chlorophyll-a contents were collected at ten sites across the Strait at monthly intervals from January 2017 to December 2018. A total of 48 genera (51 taxa) microphytoplankton were identified microscopically. Diatom was the most diverse group (32 genera), followed by dinophyte (15 genera). Bloom-forming species included diatoms Chaetoceros, Coscinodiscus, Eucampia, Pseudo-nitzschia, Rhizosolenia, Skeletonema, Thalassiosira, and dinophytes Blixaea quinquecornis and Scrippsiella. Diatom taxa that exhibit high in situ growth rates were predominant in the low-nutrient marine-influenced environment. Bloom-forming taxa including HAB taxa were found dominant in the environment with high nutrient levels and mesohaline, salinity-stratified conditions. This study provides valuable baseline data that could assist in monitoring and prediction of HABs in the Johor Strait and could be of reference to other similar tropical coastal systems.