Investigating factors driving phytoplankton growth and grazing loss rates in waters around Peninsular Malaysia

In tropical waters where temperatures are relatively stable,we investigated whether the relationship between phytoplankton growth and grazing loss rate across diff erent habitats around Peninsular Malaysia can be attributed to its eutrophication states.We measured phytoplankton growth(μ)and grazing loss(g)rates in waters off Bachok Marine Research Station(BMRS),located northeast of Peninsular Malaysia.Chlorophyll-a(chl-a)concentration ranged from 2.90 to 15.78μg/L and was dominated by nanoand micro-phytoplankton(>2μm in size).Using the Landry and Hassett dilution method,μat BMRS ranged from 1.02 to 1.58/d whereas g varied from 0.07 to 0.88/d.Grazing accounted for 35%of the primary production at BMRS.A systematic review of available data in waters around Peninsular Malaysia,revealed howμfl uctuated over a wide range(0.01–1.80/d)and correlated with chl a distribution(R 2=0.181,P<0.001).However,the relationship was only signifi cant at<9μg/L chl a for mesotrophic waters and<16μg/L chl a for eutrophic waters.In contrast,g ranged from 0.00 to 1.01/d,and correlated withμat all locations.The g/μslope ranged from 19%to 84%,and was generally similar for waters around Peninsular Malaysia.However,all the g/μslopes had a positive y-intercept except for BMRS,and this seemed to suggest the availability of alternative prey supporting grazing at the other stations.

Antibiotic residues from aquaculture farms and their ecological risks in Southeast Asia:a case study from Malaysia

Background and Objectives:One major source of antibiotic contamination in the sea is from aquaculture.We monitored the concentration of commonly used antibiotic classes and antibiotic resistance genes(tet(M),sul1,sul2 and sul3)in aquaculture farms in Peninsular Malaysia.Methods:Antibiotic residues and resistance genes were quantified using high-performance liquid chromatography and real-time PCR respectively.Risk quotients in European technical guidance document on risk assessment was used to assess the potential environmental risk.Results:We detected 23 antibiotics with tetracyclines,sulfonamides and quinolones were the most frequently detected classes,indicating a wide distribution of antibiotics in Malaysian aquaculture farms.The dendrogram and heatmap revealed three groups of antibiotic concentration patterns but with no differences in the types of antibiotics usage among aquaculture farms.The ARGs(10^(−3)copies/16S)were detected in>90%of the sites except for sul3.Ciprofloxacin,enrofloxacin,norfloxacin and lincomycin posed risks to cyanobacteria and algae in Kelantan,Perak and Pahang.Conclusion:Relative to Asian aquaculture farms,the residues detected here were at low or moderate levels except for quinolones.This study will be useful to develop effective management of aquaculture wastewater in order to mitigate antibiotic pollution and transmission of ARGs to humans through the food chain.