Abu Hena Mustafa Kamal

Status of some fishery resources in a tropical mangrove estuary of Sarawak, Malaysia

Abstract This study was carried out to assess the fishery resources of the Sibuti River estuary, Sarawak, Malaysia. Data were collected from the study area for a period of one year in different seasons. The estuary is relatively species-rich and a total of 4675 individuals of 32 families from 60 species of fish (55), crab (four) and shrimp (one) were collected. Coilia dussumieri was the dominant species (22.63%) followed by Nemapteryx caelata (11.85%), Otolithes ruber (7.85%) and Ilisha elongata (5.80%). Marked seasonal variations were found among most of the hydrobiological factors; however, seasonal variations were not significant for the diversity indices such as Shannon–Wiener, Margalef and Evenness. The number of fish taxa caught in different mesh size gill nets was 1 inch (42 species) > 2 inch (36 species) > 4 inch (25 species), suggesting that smaller mesh nets are more suitable for assessing the diversity of fishery resources. SIMPER analysis showed that Coilia dussumieri was the most abundant species in the dry (10.3%) and intermediate (8.1%) seasons, whereas N. caelata was most abundant in the wet season (7.1%). Significant differences (ANOSIM and nMDS) were observed in the species community structure between dry–intermediate and dry–wet seasons; however, species compositions were not significantly different between intermediate and wet seasons. Canonical correspondence analysis (CCA) showed that most of the species assemblages were positively correlated with turbidity and chlorophyll a, followed by phosphate, nitrate and zooplankton density. The findings suggest that the Sibuti mangrove estuary is productive in terms of diversified fishery resources, which are influenced by the hydrobiological factors.

Composition and diversity of plants in Sibuti mangrove forest, Sarawak, Malaysia

Sarawak is endowed with numerous pristine and estuarine mangroves. However, information pertaining to the species composition and diversity of pristine mangroves of Sarawak is scanty. Hence, this study was carried out to assess the plant composition and diversity of Sibuti mangrove forest, Miri, Sarawak to investigate the current status and diversity of vegetation. Nine mangrove plant species were recorded employing the line transect (100–240 m) survey method. Major mangrove species were Rhizophora apiculata, Xylocarpus granatum, and Nypa fruticans. The stand density was recorded as 1938.46 ± 482.24 trees ha−1, 1722.22 ± 254.58 saplings ha−1, and 6222.22 ± 384.90 seedlings ha−1. The mean diameter, height, and basal area for the whole forest stand were 20.83 ± 13.79 cm, 13.53 ± 5.55 m, and 201.83 ± 12.68 m2 ha−1, respectively. The mean diameter of the dominant species R. apiculata was 24.10 ± 13.90 cm, height 15.18 ± 5.09 m, and basal area 176.13 ± 12.73 m2 ha−1. The importance value index (IVI) of R. apiculata was 202.24 followed by 63.85 for X. granatum. Shannon diversity indices (H′), Margalef richness (D), and Peilou evenness (J′) of the forest stand were 1.18, 1.41, and 0.54, respectively. Similarity of species composition showed two major clusters for the whole forest stand. The findings of this study suggest that Sibuti mangrove forest stand is undisturbed and healthy. This forest could be managed and conserved for multi-sectoral uses such as ecotourism, biodiversity, research, and education rather than solely as a wildlife sanctuary.

Trace metal concentrations in salt marsh sediments from Bakkhali River estuary, Cox’s Bazar, Bangladesh

Trace metal concentrations (Cu, Zn, Cadmium (Cd), and Pb) in salt marsh sediments of the Bakkhali River estuary, Cox’s Bazar, were investigated. Sediment samples from four different sites were analyzed for the selected trace metals by atomic absorption spectrophotometer. The mean value of trace metals ranged 27,18–41.76 μg/g for Cu, 93.51–106.38 μg/g for Zn, 0.16–0.36 μg/g for Cd, and 21.28–32.08 μg/g for Pb in this salt marsh bed. In the correlation matrix, Cu positively correlated with clay (r = 0.968, p < 0.05) and silt (r = 0.995, p < 0.01), and Pb positively correlated with clay (r = 0.961, p < 0.05), silt (r = 0.998, p < 0.01), and Cu (r = 0.999, p < 0.01). Negative correlations were also found between Cu and sand (r = −0.999, p < 0.01) and Pb and sand (r = −0,999, p < 0.01). The mean concentrations of trace metals from most of the stations were found slightly higher than the recommended value of unpolluted soil. Our findings indicate that the salt marsh bed in the Bakkhali River estuary accumulates...

Seasonal Variation in the Occurrence and Abundance of Mangrove Macroalgae in a Malaysian Estuary

Abstract Mangrove macroalgae produce substantial proportion of biomass, which contributes to the coastal ecosystems. Relatively less is known for the seasonal variation in the occurrence and biomass of mangrove associated macroalgae. Consequently, mangrove macroalgae epiphytic on the pneumatophores of Avicennia marina (Forsk.) Vierh., were sampled from the Miri estuary of Sarawak during the four seasons of Malaysia namely southwest monsoon, northeast monsoon, and two inter-monsoons to elucidate seasonal variation in the occurrence and biomass production of macroalgae. Over the sample period, 11 species of mangrove macroalgae were identified from 6 genera. Six of these species such as Caloglossa leprieurii (Montagne) J.Agardh, C. adhaerens R.J.King & Puttock, C. stipitata E.Post, C. ogasawaraensis Okamura, Bostrychia kelanensis Grunow and Dictyota sp. were found to be common in each sample time. Considering four seasonal samples, maximum frequency of occurrence was observed for C. ogasawaraensis (66 ± 10%) and maximum biomass was observed for B. kelanensis (248 ± 95 g m-2). Marked seasonal variations were observed in the frequencies of occurrence and the biomass for the most of the dominant macroalgal species. To the best of our knowledge this is the first time to report the seasonal pattern data for occurrence and abundance of macroalgae from the mangrove systems of Malaysia.

Biomass and habitat characteristics of epiphytic macroalgae in the Sibuti mangroves, Sarawak, Malaysia

Mangroves support diverse macroalgal assemblages as epibionts on their roots and tree trunks. These algae provide nutrients to the primary consumers in the aquatic food web and have been reported to be substantial contributors to marine ecosystems. The species diversity, biomass, and habitat characteristics of mangrove macroalgae were investigated at three stations in the Sibuti mangrove estuary, Sarawak, Malaysia, from November 2012 to October 2013. Three groups of macroalgae were recorded and were found to be growing on mangrove prop roots, namely Rhodophyta (Caloglossa ogasawaraensis, Caloglossa adhaerens, Caloglossa stipitata, Bostrychia anomala, and Hypnea sp.), Chlorophyta (Chaetomorpha minima and Chaetomorpha sp.), and Phaeophyta (Dictyota sp.). The biomass of macroalgae was not influenced (p>0.05) by the season in this mangrove forest habitat. The macroalgal species Hypnea sp. contributed the highest biomass at both Station 1 (210.56 mg/cm2) and Station 2 (141.72 mg/cm2), while the highest biomass was contributed by B. anomala (185.89 mg/cm2) at Station 3. This study shows that the species distribution and assemblages of mangrove macroalgae were influenced by environmental parameters such as water nutrients, dissolved solids, and salinity in the estuarine mangrove habitats of Sibuti, Sarawak.

Mangrove Macroalgae as Biomonitors of Heavy Metal Contamination in a Tropical Estuary, Malaysia

Until recently, there have been only few published reports concerning the use of mangrove macroalgae as biomonitors to assess the estuarine metal contamination. Therefore, the present study was an effort to investigate the biomonitoring of metal contamination using mangrove macroalgae in the tropical Miri estuary of Sarawak, Malaysia. The metal concentrations (Cu, Fe, Mn, and Zn) were determined in the surface sediments, estuarine water, and six dominant macroalgae species that epiphytically grow on mangrove pneumatophores. The results showed that the scheme of metal occurrences in estuarine surface water and sediments was Fe > Mn > Zn > Cu and Fe > Zn > Mn > Cu, respectively. Among the studied metals in algal tissues, irrespective of macroalgal species, the concentration of Fe was found to be the highest. Significant positive correlations were found between Cu and Zn in all macroalgal species (except Caloglossa ogasawaraensis and Dictyota sp.), indicating the common origin of those elements. Concentrations of each of the studied metal in algal tissues varied among macroalgal species, probably because of the differences of structure, age, and growth of thallus among macroalgal species. To our knowledge, this is the first comprehensive report describing the biomonitoring of metal contamination using macroalgae from Malaysian mangrove systems.

Assessment of water quality at Kalatoly coast and a Shrimp hatchery, Cox’s bazar

The physico-chemical parameters of water were assessed between Kalatoly coast and a shrimp hatchery to understand the present status of water quality. This study was conducted from January 2008 to June 2008 at Coxs Bazar, Bangladesh. Water samples were collected twice monthly from the Kalatoly coast. Similarly, the ultra violet treated and larval rearing tank water were also collected from a shrimp hatchery situated at Kalatoly. Water temperature, salinity, dissolved oxygen and pH were more or less similar both in sea water and UV treated water but were highly variable in the water collected from larval rearing tank (LRT). The water NO3 N NO2 N, PO4, Fe and total dissolved solids were moderately variable among the sea water, UV treated water and LRT water. Study suggests that the existing hatchery activities are sustainable in the coast of Kalatoly which is greatly influenced by the water quality of adjacent coastal water.

Saltmarsh and seagrass beds on the south-eastern coast of Bangladesh: vegetation characteristics and adjacent fisheries diversity

AbstractSaltmarsh and seagrass communities are coastal macrophytes. These communities perform a number of important ecological functions, one of which is to support substantial fishery resources either as a nursery ground or a refuge from predators. The Bangladesh coast houses saltmarsh and seagrass resources but there has been sparse information on the diversity of fisheries adjacent to these plant communities. Consequently, this study was carried out to obtain information on the shoot density and biomass of the dominant saltmarsh (Porteresia coarctata) and seagrass (Halophila beccarii) species together with the diversity of fisheries adjacent to saltmarsh and seagrass beds on the south eastern coast of Bangladesh. The below-ground biomass of P. coarctata was found to be significantly higher than the above-ground biomass, presumably so as to survive under harsh environmental conditions, for example strong wave exposure. The standing crops and shoot density of the seagrass H. beccarii showed a similar pat...

Phytoplankton in tropical mangrove estuaries: role and interdependency

Mangrove estuaries are claimed to be productive and important breeding grounds for fishery resources. The role of particulate organic matter (POM), especially derived from decomposed litter detritus, is well documented in mangrove estuaries. However, being a primary producer, phytoplankton may play a significant role, which has not been well discussed, in governing the productivity of mangrove estuaries. Based on relevant published literature, this paper focuses on the role of phytoplankton in mangrove estuaries in the tropical coastal region and their interdependency. Analysis reveals that there are two-way interactions between phytoplankton and mangrove estuaries. The POM enriched water in mangrove estuaries acts as an ideal medium for phytoplankton succession. Simultaneously, diversified phytoplankton assemblages play a significant role in the food web of the estuarine mangrove ecosystem. Biomass and diversity of phytoplankton are influenced by nutrient and environmental parameters in mangrove estuaries and, concurrently, phytoplankton play a significant role in fish diversity and primary production in the same system. This review reveals that the inconsistent relationships between mangroves and coastal production could probably be due to the influence of seasonal changes. This paper unveils the latent potential and role of phytoplankton in tropical mangrove estuaries, which could be a source of thought for future research in this arena.

Spatial distribution of radioisotope concentrations in the offshore water and sediment of the Bay of Bengal (Indian Ocean), Bangladesh

Concentrations of natural and fall-out radionuclides in the offshore seawater and sediment from some parts of the Bay of Bengal, Bangladesh, were determined using a coaxial germanium detector. The average activities of 238U, 232Th, 40K and 137Cs were recorded as 31.2±5.8, 51.9±9.4, 686.4±170.5 and 0.5±0.6 Bq kg−1 dry weight, respectively, for sediment, and 4.8±1.2, 5.4±1.2 and 39.1±8.6 Bq L−1 for 238U, 232Th and 40K, respectively, in seawater. The concentration of 137Cs in seawater was below the detection limit. The concentration of sediment 238U was found to be positively correlated with 232Th (, p<0.05) and 40K (r=0.96, p<0.01), while 232Th was positively correlated with 40K (r=0.91, p<0.05). In sediment, the concentration of 238U was negatively correlated (r=−0.86, p<0.05) with sea depth. In the seawater sample, the only significant relationship found was between concentration of 232Th and water depth (r=−0.86, p<0.05). One-factor analysis of variance (ANOVA) showed that the level of radioisotope concentrations of seawater and sediment was highly significant for 238U (F=122, df=11, p=0.01), 232Th (F=143, df=11, p=0.01) and 40K (F=86, df=11, p=0.01). The results showed that the level of radioactivity decreased from coast to open sea. Imminent threat due to radioactivity was not observed in these parts of the Bay of Bengal.