Response of algal biomass and macrophyte communities to internal or external nutrient loading.

Nutrient input from internal and external sources could regulate the variability and abundance of algal and macrophytes in freshwater lakes. This study explores the response of algal and macrophyte growth in relation to internal and external nutrient loading. This study was conducted over a 12-month period in a eutrophic shallow urban lake known as Slim River Lake, which located in Perak state, Malaysia. The internal nutrient loading was calculated during five identified dry periods. Meanwhile, external nutrient loading was measured from stormwater runoff after storm events. Algal biomass was measured twice a month, while total macrophyte abundance was measured once in a month. In this lake, internal nutrient loading could contribute up to 7538.33 kg total phosphorus and 42.23 kg total nitrogen during dry periods. Meanwhile, external nutrient loading quantified from the stormwater runoff contributed up to 401,500 kg total phosphorus and 4611.67 kg total nitrogen. The highest monthly mean for algal biomass and total macrophyte abundance was recorded as 60,343.75 cells/mL and 821.50, respectively. Based on the Pearson correlation analysis, algal biomass was significantly correlated with the internal total phosphorus loading (r = 0.54, p < 0.05). In addition, algal biomass also shows an inverse relationship with the external total phosphorus loading (r = - 0.44, p < 0.05). In contrast, total macrophyte abundance was significantly correlated with the external total phosphorus loading (r = 0.50, p < 0.05) and external total nitrogen loading (r = 0.44, p < 0.05). These results suggest that variation of nutrient sources triggers a different response by algal and macrophytes in the study lake. In implications, these findings show that a combination approach in reducing nutrients from sediment and anthropogenic sources is required for potential lake restoration.

Characterization and expression of Xiphophorus maculatus microsatellite Msb069 full sequence in subgenus Poecilia.

Msb069 primer pairs encompassed region is believed to be associated with a quantitative trait loci (QTL) of dorsal fin length in subgenus Poecilia. However, detailed investigation on Msb069 which originated from Xiphophorus on subgenus Poecilia remains unexplored. In this study, full sequence of Msb069 was characterized by sequencing bioinformatics analysis and gene expression. The sequence analysis of Msb069 primer pairs encompassed region on three species of Poecilia revealed higher number of microsatellite tandem repeats in Poecilia latipinna (ATG16) compared to P. sphenops (ATG13-14). There is no notable pattern of ATGtandem repeats discovered in the hybrids. The full sequence of Msb069 is 734 bp in length and showed a 233 bp conserved region between Xiphophorus and Poecilia. BLAST search performed on this sequence revealed no significant similarities. Nonquantitative RT-PCR exhibited the presence of Msb069 transcripts in three different tissues in subgenus Poecilia. Meanwhile, quantitative RTPCR expression on two different tissues showed relatively higher expression of Msb069 transcript in P. latipinna dorsal fin tissues in both male and female fishes, suggesting a repressive function of this transcript with respect to dorsal fin length. However the exact gene expression event of Msb069 is still unknown and requires further investigation.

Preliminary Assessment of Cyanobacteria Diversity and Toxic Potential in Ten Freshwater Lakes in Selangor, Malaysia.

Toxic cyanobacteria blooms are increasing in magnitude and frequency worldwide. However, this issue has not been adequately addressed in Malaysia. Therefore, this study aims to better understand eutrophication levels, cyanobacteria diversity, and microcystin concentrations in ten Malaysian freshwater lakes. The results revealed that most lakes were eutrophic, with total phosphorus and total chlorophyll-a concentrations ranging from 15 to 4270 µg L(-1) and 1.1 to 903.1 µg L(-1), respectively. Cyanobacteria were detected in all lakes, and identified as Microcystis spp., Planktothrix spp., Phormidium spp., Oscillatoria spp., and Lyngbya spp. Microcystis spp. was the most commonly observed and most abundant cyanobacteria recorded. Semi-quantitative microcystin analysis indicated the presence of microcystin in all lakes. These findings illustrate the potential health risk of cyanobacteria in Malaysia freshwater lakes, thus magnifying the importance of cyanobacteria monitoring and management in Malaysian waterways.

Could the presence of larger fractions of non-cyanobacterial species be used as a predictor of microcystin production under variable nutrient regimes?

The occurrence of cyanobacteria and microcystin is highly dynamic in natural environments and poses one of the biggest challenges to water resource management. While a number of drivers are known to be responsible for the occurrence of cyanobacterial blooms, the drivers of microcystin production are not adequately known. This study aims to quantify the effects of the changes in the structures of phytoplankton and cyanobacterial communities on the dynamics of microcystin production under highly variable nutrient concentration. In our study, nutrient variability could explain 64% of the variability in microcystin production. When changes in the fractions of non-cyanobacteria versus cyanobacteria genera were additionally included, 80% of the variability in microcystin production could be explained; under high nutrient concentrations, non-cyanobacterial phytoplankton groups were dominant over cyanobacteria and cyanobacteria produced more toxins. In contrast, changes in the cyanobacterial community structures could only explain a further 4% of the dynamics of microcystin production. As such, the dominance of non-cyanobacterial groups appears to be a useful factor to explain microcystin occurrence in addition to traditionally used factors such as absolute cyanobacterial cell numbers, especially when the nutrient regime is taken into account. This information could help to further refine the risk assessment frameworks which are currently used to manage the risk posed by cyanobacterial blooms.

Development of a new risk-based framework to guide investment in water quality monitoring.

An innovative framework for optimising investments in water quality monitoring has been developed for use by water and environmental agencies. By utilising historical data, investigating the accuracy of monitoring methods and considering the risk tolerance of the management agency, this new methodology calculates optimum water quality monitoring frequencies for individual water bodies. Such information can be applied to water quality constituents of concern in both engineered and natural water bodies and will guide the investment of monitoring resources. Here we present both the development of the framework itself and a proof of concept by applying it to the occurrence of hazardous cyanobacterial blooms in freshwater lakes. This application to existing data demonstrates the robustness of the approach and the capacity of the framework to optimise the allocation of both monitoring and mitigation resources. When applied to cyanobacterial blooms in the Swan Coastal Plain of Western Australia, we determined that optimising the monitoring regime at individual lakes could greatly alter the overall monitoring schedule for the region, rendering it more risk averse without increasing the amount of monitoring resources required. For water resources with high-density temporal data related to constituents of concern, a similar reduction in risk may be observed by applying the framework.

Spatial and temporal variability in the relationship between cyanobacterial biomass and microcystins.

The increasing incidence of toxic cyanobacterial blooms, together with the difficulties to reliably predict cyanobacterial toxin (e.g. microcystins) concentration, has created the need to assess the predictive ability and variability of the cyanobacterial biomass-microcystin relationship, which is currently used to assess the risk to human and ecosystems health. To achieve this aim, we assessed the relationship between cyanobacterial biomass and microcystin concentration on a spatiotemporal scale by quantifying the concentration of cyanobacterial biomass and microcystin in eight lakes over 9 months. On both a temporal and spatial scale, the variability of microcystin concentration exceeded that of cyanobacterial biomass by up to four times. The relationship between cyanobacterial biomass and microcystin was weak and site specific. The variability of cyanobacterial biomass only explained 25 % of the variability in total microcystin concentration and 7 % of the variability of cellular microcystin concentration. Although a significant correlation does not always imply real cause, the results of multiple linear regression analysis suggest that the variability of cyanobacterial biomass and cellular microcystin concentration is influenced by salinity and total phosphorus, respectively. The weak cyanobacterial biomass-microcystin relationship, coupled with the fact that microcystin was present in concentrations exceeding the WHO drinking water guidelines (1 µg L(-1)) in most of the collected samples, emphasizes the high risk of error connected to the traditional indirect microcystin risk assessment method.