Distribution Pattern of Dissolved Inorganic Nutrients and Phytoplankton Diversity in River Estuary, Kota Kinabalu Sabah, Malaysia

Nutrients are influenced by anthropogenic activities and consequently change the diversity and density of phytoplankton. The spatial distribution of dissolved inorganic nutrients and phytoplankton diversity and density were determined in river estuary, Kota Kinabalu, Sabah, Malaysia. Samples of water and phytoplankton were collected from six locations of river estuary during the month of May 2019 to October 2019. The highest abundances of 86% diatoms were determined during the study period. This was followed by 13% and 1% of dinoflagellates and Cyanobacteria respectively. The most dominance species of Skeletonema costatum, with density of 1186.69 × 103 cells/L and Thalassiosira sp. (938.01 ×103 cells/L) were recorded from Station 1 (upstream) and Station 5 (mangrove area) respectively. The Chaetoceros sp. (84.25 × 103 cells/L) was the dominated in Station 6 (control site). Station 4 (residential area) accounted the highest diversity of species such as Skeletonema costatum, Thalassiosira sp., Peridinium sp., Gonyaulax sp., and Cylindrotheca sp. with total cell density of 142.98 × 103 cells/L. The high diversity index of 5.2 to 7.09 and evenness index of 1.81 to 2.87 were determined from this river estuary. Very poor relationship was observed with the cell density and dissolved inorganic nutrients, phosphate (R2 = 0.2437), ammonium (R2 = 0.301) and nitrate (R2 = 0.406). The diversity and abundance of phytoplankton in this river estuary not only depend on nutrients, but might be associated with other environmental factors, tidal fluctuations and rate of discharge of nutrient inputs from surrounding areas. This study suggests that long term monitoring not only the nutrients, but discharges and flushing of nutrient during rainfall and tidal fluctuation together with environmental factors should be considered in order to conclude status on the diversity and abundance of phytoplankton in river estuary.

Drivers of coastal bacterioplankton community diversity and structure along a nutrient gradient in the East China Sea

Anthropogenic nutrient discharge poses widespread threats to coastal ecosystems and has increased environmental gradients from coast to sea. Bacterioplankton play crucial roles in coastal biogeochemical cycling, and a variety of factors af fect bacterial community diversity and structure. We used 16 S r RNA gene pyrosequencing to investigate the spatial variation in bacterial community composition(BCC) across five sites on a coast-of fshore gradient in the East China Sea. Overall, bacterial alpha-diversity did not diff er across sites, except that richness and phylogenetic diversity were lower in the of fshore sites, and the highest alpha-diversity was found in the most landward site, with Chl-abeing the main factor. BCCs generally clustered into coastal and of fshore groups. Chl-a explained 12.3% of the variation in BCCs, more than that explained by either the physicochemical(5.7%) or spatial(8.5%) variables. Nutrients(particularly nitrate and phosphate), along with phytoplankton abundance, were more important than other physicochemical factors, co-explaining 20.0% of the variation in BCCs. Additionally, a series of discriminant families(primarily affiliated with Gammaproteobacteria and Alphaproteobacteria), whose relative abundances correlated with Chl-a, DIN, and phosphate concentrations, were identified, implying their potential to indicate phytoplankton blooms and nutrient enrichment in this marine ecosystem. This study provides insight into bacterioplankton response patterns along a coast-of fshore gradient, with phytoplankton abundance increasing in the of fshore sites. Time-series sampling across multiple transects should be performed to determine the seasonal and spatial patterns in bacterial diversity and community structure along this gradient.

Environmental variables affecting the gillnet catches and condition of Labiobarbus festivus and Osteochilus hasseltii in northern Malaysia

The influences of technical factors on the catching efficiencies of gillnets are well understood,but less is known about the importance of environmental factors and how these might concurrently affect target-species condition.Here we address this deficit for two economically important southeast Asian cyprinids(Labiobarbus festivus and Osteochilus hasseltii)during a one-year study at a key fishing location in Lake Kenyir,Malaysia.Three gillnets(each 200 m long,2 m deep and comprising either 38-,51-,or 76-mm mesh)were deployed each month concurrent with sampling of benthic macroinvertebrates and various environmental parameters.Various multivariate analyses(detrended correspondence analysis,redundancy analysis and permutational multivariate analysis of variance)were used to explore potential relationships between the extrinsic variables(mesh size,sampling season,water quality and,based on known prey items,benthic macroinvertebrates)and gillnet catches and the biological condition(growth co-efficient and hepatosomatic index)of the target species.Catches of L.festivus(the most abundant species)were positively influenced by water turbidity without seasonal effects,while their biological condition was positively influenced by benthic macroinvertebrates(mostly Trichoptera)and the concentrations of DO and phosphate,and negatively influenced by water temperature.By comparison,seasonal influences on the catches and biology of O.hasseltii were somewhat size specific with positive and negative effects of the monsoon on small and large fish,respectively.The abundance of phytoplankton also positively affected the catches of O.hasseltii,while their biological condition was positively influenced by water temperature,but negatively influenced by water turbidity.Such species-specific differences were attributed to life histories,and although the more abundant L.festivus might be best sought during any period of turbidity,effort should be focused during the monsoon when individuals have optimal condition(and therefore better flesh quality).In contrast,larger O.hasseltii might be best sought during non-monsoon months concurrent with greater catches and optimal condition.Collecting similar data for other freshwater species both nationally and internationally might facilitate future efforts at fine-tuning gillnet fishing effort.