DNA-based taxonomy of a mangrove-associated community of fishes in Southeast Asia

The Merbok Estuary comprises one of the largest remaining mangrove forests in Peninsular Malaysia. Its value is significant as it provides important services to local and global communities. It also offers a unique opportunity to study the structure and functioning of mangrove ecosystems. However, its biodiversity is still partially inventoried, limiting its research value. A recent checklist based on morphological examination, reported 138 fish species residing, frequenting or subject to entering the Merbok Estuary. In this work, we reassessed the fish diversity of the Merbok Estuary by DNA barcoding 350 specimens assignable to 134 species initially identified based on morphology. Our results consistently revealed the presence of 139 Molecular Operational Taxonomic Units (MOTUs). 123 of them are congruent with morphology-based species delimitation (one species = one MOTU). In two cases, two morphological species share the same MOTU (two species = one MOTU), while we unveiled cryptic diversity (i.e. COI-based genetic variability > 2%) within seven other species (one species = two MOTUs), calling for further taxonomic investigations. This study provides a comprehensive core-list of fish taxa in Merbok Estuary, demonstrating the advantages of combining morphological and molecular evidence to describe diverse but still poorly studied tropical fish communities. It also delivers a large DNA reference collection for brackish fishes occurring in this region which will facilitate further biodiversity-oriented research studies and management activities.

Assessing fish diversity of Merbok Estuary and adjacent marine waters by DNA taxonomy: towards building comprehensive DNA barcode reference library

The Merbok Estuary comprises one of the largest remaining mangrove forests in Peninsular Malaysia. Its value is significant as it provides both direct and indirect services to local and global communities. It also offers a unique opportunity to study the structure and functioning of mangrove ecosystems. However, its biodiversity is still partially described, limiting its research value. Recent inventories based on morphological examination, documented 138 fish species residing, frequenting or subject to entering the Merbok Estuary. Using a molecular approach, we assessed the fish diversity of the Merbok Estuary and its adjacent waters in DNA barcoding 350 specimens assignable to 135 species initially identified based on morphology. Our results revealed the presence of 140 MOTUs, 130 of them are congruent with morphology-based species delimitation. In two cases, barcodes did not permit to differentiate between two morphotypes while they unveiled cryptic diversity within six other species, calling for further taxonomic investigations. This study provides a comprehensive core-list of fish taxa in Merbok Estuary, demonstrating the advantages of combining morphological and molecular evidence to describe diverse but still poorly studied tropical fish communities. It also delivers a large DNA reference collection for brackish fishes occurring in this region which will facilitate further biodiversity-oriented research studies and management activities.

Factor influencing the spatio-tempoaral distribution of zooplankton biomass in the Merbok estuary, Malaysia

Spatial and temporal distribution of zooplankton biomass in the Merbok estuary were studied. Zooplankton samples were collected monthly from January to December 2011 at six sampling stations along the river stretch by using 0.13 m diameter plankton net (150 ?m mesh size) in horizontal towing. Average zooplankton biomass ranged from 0.1143 to 1.8217 g dry wt.m-3. The maximum and minimum zooplankton biomass recorded in February and October 2011, respectively. The highest zooplankton biomass was found at Station 6 (downstream) and the lowest in Station 1 (upstream). Zooplankton biomass varied from upstream to downstream. Kruskal-Wallis H test showed that distribution of zooplankton biomass among the sampling months was significantly different (p < 0.05). Spearman’s rank correlation analysis revealed significant correlation among zooplankton biomass, chl a concentration and nutrients (p < 0·01).Bangladesh J. Zool. 44(1): 147-152, 2016

Effects of Water Quality Parameters on Abundance and Biomass of Zooplankton in Merbok Estuary Malaysia

Influence of water quality parameters on zooplankton abundance and biomass in the Merbok estuary Malaysia were investigated. Twenty four hours sampling were conducted at station 1, 3 and 5 from 12th November (spring tide) to 3rd December (neap tide) 2011 on weekly interval. Results showed that water quality parameters varied with the following ranges: conductivity (10.00-315.00?S-1cm), transparency (25.50-154.00 cm), light intensity (53.5-1959.00 lux), TSS (20-70 mg-1L), BOD (0.25-3.46 mg-1L) and chl a (0.1-1.46 ?g-1L). The highest zooplankton abundance was found at Station 5 (176×103) and (230×103) ind-3m and the lowest was at station 1(5.3×103) and (3.4 ×103) ind-3m during spring and neap tide. Zooplankton biomass varied from 0.04 to 0.096 gm-3m. Spearman’s rank correlation analysis results showed that there was a correlation among zooplankton abundance and conductivity, transparency, TSS, BOD, and biomass except chl and light intensity. Mann-Whitney U test result showed that water quality parameters, zooplankton abundance and zooplankton biomass were significantly different between spring and neap tides.J. Environ. Sci. & Natural Resources, 9(1): 117-122 2016

Variation of Food items in the Stomach Contents of two Mullets, Chelon subviridis and Valamugil buchanani, from Merbok Estuary, Kedah, Malaysia

This study was conducted in Merbok estuary, Kedah, Malaysia during January to December 2011 to assess monthly and seasonal variation in food items in the stomach of Chelon subviridis and Valamugil buchanani. A total of 341 fish samples (225 for Chelon subviridis and 116 for Valamugil buchanani) were collected from upper zone (Lalang and Sameling Rivers) of Merbok estuary. Among the stomach contents plant materials, diatom, cyanobacteria and detritus were the main food items in both fish species. In both fishes the highest numbers of food items were found in the month of November. Chelon subviridis consumed plant materials 65.84% by number and 8.55% by frequency of occurrence in the dry season whereas 66.25% by number and 9.73% by frequency of occurrence in the wet season. On the other hand, Valamugil buchanani consumed plant materials 59.54% by number and 12.28% by frequency of occurrence in the dry season whereas 72.89% by number and 11.96% by frequency of occurrence in the wet season respectively. Monthly variations of diatom as food item between C. subviridis and V. buchanani were found to be statistically significant (p<0.05). Both of the fish species consumed more food (by numerical method) in wet season than dry season.Bangladesh J. Zool. 43(2): 213-220, 2015

Population dynamics of zooplankton in Merbok estuary, Kedah, Malaysia in relation to some water quality parameters

In the present investigation, Station 5 located in the downstream of the Merbok estuary showed higher density of zooplankton (132 × 103 ind/m3) but it was lowest (83 × 103 ind/m3) was at Station 2 (upstream). The highest and lowest zooplankton density was observed in May and November, respectively. Twenty groups of zooplankton were recorded and copepod was the dominant group at all sampling stations during the sampling period. Months and stations were statistically significant (Kruskal-Wallis H test; p < 0.05) factors that affect the density of zooplankton, temperature, salinity and nutrients. Mann-Whitney U test showed that temperature, NO2 and zooplankton density were significantly different between seasons (p < 0.01). Significant correlation among zooplankton density, chl a concentration and nutrients (p < 0?01) were observed.Dhaka Univ. J. Biol. Sci. 25(1): 47-55, 2016

Effects of Tidal Events on the Water Quality in the Merbok Estuary, Kedah, Malaysia

This study was carried out to observe effects of tidal events on the water quality parameters at Merbok estuary, Kedah, Malaysia. Twenty four hours sampling were conducted at Station 1, 2 and 3 from 12th November (spring tide) to 3rd December (neap tide) 2011 on weekly interval. Results showed that water quality parameters varied with the following ranges: temperature (26.10 - 30.7°C), pH (6.29 - 7.22), dissolved oxygen (0.65 - 5.48 mgL-1), salinity (0.50 – 35PSU), nitrate (0.037 - 0.647mgL-1), nitrite (0.09 - 0.36 mgL-1), ammonia – N (0.03 - 3.05 mgL-1), phosphate (0.03 - 0.10mgL-1). Kruskal Wallis H test showed that water quality parameters were significantly different among sampling stations (p<0.01). Mann-Whitney U test result showed that water quality parameters were significantly different between spring and neap tides (p<0.01) except temperature and nitrate. Parameters such as temperature, salinity, nitrate, ammonia – N and phosphate recorded higher in spring tide while, DO, pH and nitrite were higher in neap tide.J. Environ. Sci. & Natural Resources, 8(2): 15-19 2015

Analysis of stomach contents in green back mullet, Chelon subviridis from Merbok Estuary, Malaysia

not availableBangladesh J. Zool. 43(1): 153-156, 2015

Limnology of Merbok estuary, Kedah, Malaysia

Water quality in three different stations of Merbok estuary was investigated limnologically from October, 2010 to September, 2011. Water temperature, transparency and total suspended solids (TSS) varied from 27.45 - 30.450C, 7.5 - 120 cm and 10 -140 mg/l, respectively. Dissolved Oxygen (DO) concentration ranged from 1.22-10.8 mg/l, while salinity ranged from 3.5-35.00 ppt. pH and conductivity ranged from 6.35 - 8.25 and 40 - 380 ?S/cm, respectively. Kruskal Wallis H test shows that water quality parameters were significantly different among the sampling months and stations (p<0.05). This study revealed that DO, salinity, conductivity and transparency were higher in wet season and TSS was higher in dry season. On the other hand, temperature and pH did not follow any seasonal trends.Bangladesh J. Zool. 41(1): 13-19, 2013