Md. Khurshid Alam Bhuiyan

Cu, Zn, Fe, and Mn in mangrove ecosystems (sediment, water, oyster, and macroalgae) of Sarawak, Malaysia

Trace metals from industrial effluents discharged into Malaysian mangrove ecosystems, in Sarawak in particular, are of growing concern. Concentrations of trace metals (copper, manganese, iron, and zinc) were determined in sediment, surface water, pore water, green and red filamentous macroalgae (Chaetomorpha sp. and Bostrychia sp., respectively) and the rock oyster Saccostrea cucullata from three estuarine mangrove habitats in Sarawak (Kuala Nyalau, Bakam, and Miri), Malaysia. Trace metal concentrations detected in sediment of these mangrove ecosystems (except for Zn concentration in K. Nyalau) were considerably higher than those specified in USEPA sediment quality guidelines. Sediment trace metal concentrations differed significantly (pxa0 xa0Mnxa0>xa0Znxa0>xa0Cu, Fexa0>xa0Znxa0>xa0Mnxa0>xa0...

Temporal distribution of water characteristics in the Miri estuary, east Malaysia

AbstractThis baseline study was carried out to investigate the physicochemical factors such as pH, salinity, temperature, turbidity, total dissolved solids (TDS), total suspended solids and dissolved oxygen (DO), as well as nutrient (nitrate, phosphate, ammonium) concentrations and the level of heavy metals (Fe, Zn, Cu, Mn) in the surface water of the Miri estuary at four sampling times based on the four seasons of Malaysia. Results indicated marked temporal differences in each of the water characteristics measured (except ammonium), where DO level (mean: 3.6xa0mg/L) was found in a concern level. The principle component analysis (PCA) was applied to the hydrological and hydrochemical data set of the Miri estuary; results indicated that principle component 1 and principle component 2 explained 61.78 and 18.69%, respectively, of the total variance in the data set. Besides, results of PCA also indicated that the factors for water characteristics variations were mainly related to TDS, salinity, and Fe. The data...

Distribution of Trace Metals in Channel Sediment: a Case Study in South Atlantic Coast of Spain

Recently, Sancti Petri channel on the southwestern (SW) part of Iberian Peninsula has been experiencing urban, industrial, and vehicular expansion. Until recently, there have been only few published reports documenting the pattern of metal accumulation in this estuarine sediment. In the present study, trace metals such as Cu, Zn, Ni, Mn, Pb, Co, Cd, As, and Hg concentrations were analyzed from 69 sediment samples collected from 23 sampling sites of the Santi Petri channel. The magnitude of trace metal accumulation found as the following trend: Mn > Zn > Cu > Pb > Ni > Co > As > Cd > Hg. Spatial distribution pattern demonstrated overall decreasing trend of trace metal from Cadiz Bay mouth to the open ocean mouth, clearly correlative to the presence of anthropogenic inputs. Results of the principle component analysis (PCA) revealed that sediment metal chemistry of Sancti Petri channel is mainly regulated by the concentrations of Pb, Cu, Zn, and Ni; possible sources of those were from vehicular-related emissions. Pollution load index (PLI) and geo-accumulation index (Igeo) indicated overall low values. The study will stimulate improvement of our understanding regarding the pattern of accumulation of metals in the coastal sediments, and the recorded values of metals in the present study can be used as suitable reference for future studies.

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.

Decay of Rhizophora apiculata (Blume) and Xylocarpus granatum (Koenig) detrital sources in the Sarawak Mangrove, Malaysia

Decaying mangrove detritus plays a significant role in nutrient cycling and fueling in both the forests and aquatic habitats where the detritus stems from estuarine and coastal food webs. Detrital decay rates partly depend on the type of detritus, but most studies have thus far focused on leaf litter decay and decomposition, whereas other detrital sources (except for roots) have largely been ignored. We compare the decay rates of Rhizophora apiculata and Xylocarpus granatum non-leafy detritus (flowers, propagules, stipules, and twigs) with mangrove leaf litter in field studies, using litter bags during the dry and the wet seasons in the tropical mangrove forest of Sibuti, Sarawak, Malaysia. We observed higher microbial decay rates of stipules, flowers, propagules, and twigs for both the R. apiculata and X. granatumduring the wet months. By contrast, leaf decay rates were higher during the dry months. Decay rates depended on the lignin content of the detrital sources of both species, both during dry and wet months. Accordingly, the half-life (T0.5) and 95% lifespan (T0.95) of non-leaf materials (flowers, propagules, stipules and twigs) for both species were remarkably longer than those of leaf litter. Slowly decaying non-leafy detritus may play a significant role in nutrient and carbon cycling over longer time, when leaf litter is either being decomposing rapidly and/or being washed away by tidal flush and river runoff. Hence, non-leafy (flowers, propagules, stipules and twigs) detritus should be taken into account when budgeting organic matter turnover in mangroves.

Seasonal distribution of phytoplankton community in a subtropical estuary of the south-eastern coast of Bangladesh

AbstractPhytoplankton are the basic component of the aquatic food chain. To date phytoplankton communities from the coastal waters of Bangladesh have received only little scientific attention. Consequently, the abundance and community composition of phytoplankton and their relationship with some abiotic factors were studied during December 2014 to August 2015 in the Reju Khal estuary of the south-eastern coast of Bangladesh. Marked seasonal differences were observed for all of the measured abiotic factors. The density of the phytoplankton cells ranged between 9408 and 21,964 cellsxa0L−1 and had significant differences among seasons. Over all seasonal samples, 27 genera were identified of which Biddulphia was found to be the most contributory one (13.6%) followed by Coscino discus (7.9%) and Nostoc (7.8%). Marked seasonal differences in the community structure of phytoplankton were confirmed by the multivariate analyses. Further, phytoplankton populations had strong positive correlations with pH, salinity, t...

Inter-linkage among some physico-chemical and biological factors in the tropical mangrove estuary

AbstractThe interaction between abiotic and biotic parameters in an ecosystem usually shows health and functioning of the system. Thus, some physico-chemical parameters, phytoplankton abundance, chlorophyll a and primary production of the mangrove estuary in Sarawak, Malaysia were extensively investigated from January 2013 to December 2013 in order to establish the inter-linkage among them. The Pearson correlation coefficient revealed a significant relation between atmospheric and water temperatures (rxa0=xa00.692). Similarly, surface water temperature showed a significant positive correlation with salinity (rxa0=xa00.744), TDS (rxa0=xa00.708) and conductivity (rxa0=xa00.776). The light extinction coefficient (LEC, K) changed negatively in relation to TDS (rxa0=xa0–0.623), conductivity (rxa0=xa0–0.644) and surface water temperature (rxa0=xa0–0.766). Ammonium showed a negative correlation with rainfall (rxa0=xa0–0.620) but a positive correlation with salinity (rxa0=xa00.600). The biological variable such as phytoplankton abundance was found ...

Size frequency and length–weight relationships of three semi-tropical cephalopods, Indian squid Photololigo duvaucelii, needle cuttlefish Sepia aculeata, and spineless cuttlefish Sepiella inermis from the coastal waters of Bangladesh, Bay of Bengal

AbstractSize frequency and length–weight relationships (LWRs) for three cephalopods, Indian squid Photololigo duvaucelii, needle cuttlefish Sepia aculeata, and spineless cuttlefish Sepiella inermis were studied. Specimens were caught from the coastal waters of Bangladesh (Moheshkhali Channel and Sonadia Island) using both trawl and marine set bag nets. The maximum dorsal mantle length for the Indian squid, needle cuttlefish, and spineless cuttlefish was recorded to be 228, 135, and 82xa0mm, respectively. The estimated growth coefficient b was 1.377 for Indian squid, 2.504 for needle cuttlefish, and 1.979 for spineless cuttlefish. The growth coefficient for these three species indicated hypoallometric growth from this region. No information has been published regarding size frequency and LWRs for these three cephalopods from the coastal waters of Bangladesh. The results of this study will be useful for the management and conservation of squid fisheries from the Bay of Bengal.

Proximate Chemical Composition of Sea Grapes Caulerpa racemosa (J. Agardh,1873) Collected from a Sub-Tropical Coast

Background: Nutritional fact study has prime importance to make the species edible and commercially viable to the consumers. Proximate chemical composition and amino acid profile were investigated to understand the nutritional value and protein quality of an edible algae Caulerpa racemosa. Methods: Samples were collected randomly by hand from the intertidal zone of the sub-tropical coastal Island St. Martin’s Island from February 2013 to May 2014. Samples were preserved using standard methods for chemical analysis. Proximate composition was determined using standard methods, Kjeldahl method for protein, Soxhlet method for crude lipid, H2SO4 (0.3 N) and NaOH (0.5 N) for dietary fibre, muffle furnace method for moisture content, ion-exchange chromatography for amino acid and statistical package used for validating the data. Results: The result of the study reveals that C. racemosa contains higher amount of proteins (19.72±0.77%), crude lipid (7.65±1.19%) and fibre (11.51±1.32%) compared to other green and brown algae. The higher concentration of aspartic acid (12.7±0.2%) and glutamic acid (9.2±0.7%) were observed in C. racemosa, while histidine (2.6±0.7%), methionine (1.4±0.4%) and tyrosine (3.8±0.2%) were the limiting amino acids. Lysine (6.6±0.2%), leusine (6.9±0.6%), glycine (6.5±0.4%), arginine (6.4±0.3%), alanine (7.6±0.6%) and threonine (6.2±0.5%) were obtained at a higher percentage of total amino acids. Conclusion: This study suggests that C. racemosa could be potentially used as a nutritious and functional food item for human consumption. Further studies on this edible species should be focused on fatty acid composition, vitamins, non-starch polysaccharide constituents, trace elements and sensory perceptions in order to depict safer and versatile utilization.