Gracilaria red algae are notable for their economic importance as agrophytes, sold as salad vegetable, and used as the base for selected food and nonalcoholic beverages. A wild population of Gracilaria exists in coastal areas of Sarawak, Malaysian Borneo, but there is only limited knowledge on species diversity and its abundance leaving the untapped economic potential of this resource. This study was carried out to determine diversity of wild Gracilaria populations in Lawas, Santubong, and Asajaya, Sarawak, using the combination of morphological character examination and 5′ region of the mitochondrial cytochrome c oxidase 1 (CO1-5P) gene analysis. Identification of the species using morphological characters revealed three species, namely, Gracilaria changii, G. blodgettii, and G. arcuata, had been collected from the sampling sites. However, based on 672 bp CO1-5P gene sequence analysis, all the three species were identified as G. blodgettii; besides, low genetic divergence values (0.17%–0.34%) were scored between samples in this study with the same species in GenBank. In the phylogenetic trees, all samples in this study group together with other G. blodgettii have high bootstrap values; thus, this species is monophyletic. This study implies that species identification of Gracilaria and other seagrass taxa which have a phenotypic plasticity problem should include the CO1-5P gene analysis as it is a reliable gene marker for species diversity assessment.
Red seaweed Gracilaria sp. is known as ‘Janggut Duyong’ by the local people of Sarawak. This macroalgae iswell-distributed in both temperate and tropical seawaters. Gracilaria sp. could be processed to produce agar forindustrial purposes whereas some people consumed it directly and become part of their daily diet. In terms ofecology, Gracilaria sp. is one of primary producer in the seawater and its presence can form habitats to supportother aquatic organisms. Despite its socio-economic and ecological importance, little is known about Gracilariasp. in Sarawak. Hence, this study is designed to: (i) determine the diversity and abundance of Gracilaria in cageculture of Lawas, Sarawak (ii) assess the water quality of the cage culture area where Gracilaria is found and(iii) determine other aquatic organisms that found within Gracilaria population. Three field samplings had beenconducted from October 2013 to November 2014 at cage culture areas of Awat-Awat Village, Lawas, Sarawak.Only single species of Gracilaria was found namely Gracilaria arcuata. Besides G. arcuata, Acanthophora sp.and Padina sp. were also found but in small patches. In addition, five different groups of aquatic invertebrateswere observed namely tunicates, bivalves, polychaetes, small crabs and brittle stars. The selected water qualityparameters namely temperature, pH, dissolved oxygen, salinity, turbidity, total suspended solid, orthophosphate,silicate and chlorophyll a were significantly different (p= 0.000) during all the three field samplings except fornitrite (p= 0.588). However, the values recorded were within normal range of standard water quality for tropicalestuarine area. Since healthy population of Gracilaria could be easily found here, therefore this area has thepotential for future seaweed aquaculture.
The sergestid shrimp (Acetes spp.) shows the annual peak season from February to April. This krill-like shrimp, locally known as ‘bubok’, is one of the commercially important fisheries in Miri, Sarawak, Malaysian Borneo. Previous researchers had reported patchy data on the environmental factors and Acetes distribution in Miri-Bintulu adjacent areas. Moreover, insufficient analysis has led to the inability to conduct sustainable management strategies for Acetes fisheries. Therefore, this study is designed to explore the mathematical model usage to understand the interaction between selected water quality parameters and zooplankton assemblages with the Acetes population in the coastal water of Miri. Selected temporal biotic and abiotic data were collected using standard methods and later subjected to mathematical time series analysis called the Granger causality test. The results show bi-directional Granger causality between the abundance of Acetes and dissolved oxygen (DO). Interaction between other water quality parameters (temperature, salinity, turbidity, pH, TSS and Chlorophyll a) with the abundance of Acetes has also emerged. The number of zooplankton in the water column, namely Centropages, Euterpina, Oithona rigida, and Oncaea shows a significant causality towards the abundance of Acetes. The findings imply that complex interaction between biotic and abiotic factors exists during the bloom of Acetes in Miri; thus, relevant agencies should step up measures to ensure sustainable management of the coastal areas where Acetes bloom occurs.
Evidences have shown that coastal water as habitat that support various flora and fauna as well as nursery ground which highlight the importance of water quality monitoring that act as basis for productivity of fisheries. Therefore, the objective of this study is to analyse the temporal and spatial variations of selected water quality parameters in sergestid shrimp’s habitat along the coastal water of Miri, Sarawak. Nine water quality parameters namely dissolved oxygen (DO), temperature, turbidity, pH, salinity, chlorophyll a (chl a), total suspended solid (TSS), nitrate (NO3-) and orthophosphate (PO43-) were measured in four stations along Miri coastal water. The variation explained by the principal component analysis had a total variance of 55.95%. The PC1 shows that the waters in July 2017, September 2017, October 2017, December 2017 and January 2018 were characterized with high turbidity and TSS as well as low temperature and salinity. In contrast, stations in November 2017, March 2018 and April 2018 had warmer and clear water with high salinity reading, whereby blooms of sergestid shrimps were observed in March and April 2018. The PC2 result shows that in May 2017 and June 2017, coastal waters were characterized with low pH reading. Overall, the water quality parameters measured in all stations were close to the standard value of Class E of Malaysian Marine Water Quality Standards (MMWQS).
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