Anthropogenic disturbance of aquatic biodiversity and water quality of an urban river in Penang, Malaysia

Malaysia's rapid economic and demographic development have placed negative pressure on its water supplies and the quality of the Juru River, which is close to the nation's capital and its major source of water. Healthy aquatic ecosystems are supported by physicochemical properties and biological diversity. This study evaluated the anthropogenic impacts on aquatic biodiversity, especially plankton, fish, and macrobenthos, as well as the water quality of the Juru River in the Penang area. Aquatic biodiversity and river water parameters were collected from ten sampling stations along the Juru River. Seven variables were used to assess the physicochemical environment: pH, temperature, total suspended solids (TSS), salinity, dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand. At each sampling station, the total number of plankton, fish, and macrobenthic taxa were counted and analyzed. The relationships between the physicochemical parameters and aquatic biodiversity were investigated with biotypological analysis, principal component analysis, hierarchical cluster analysis, and linear regression analysis. These analyses showed that the richness and diversity indices were generally influenced by salinity, temperature, TSS, BOD, and pH. The data obtained in this study supported the bioindicator concept. The findings, as they related to scientifically informed conservation, could serve as a model for Juru River management, as well as for river management throughout Malaysia and other tropical Asian countries.

Evaluating eDNA and eRNA metabarcoding for aquatic biodiversity assessment: From bacteria to vertebrates

The monitoring and management of aquatic ecosystems depend on precise estimates of biodiversity.Metabarcoding analyses of environmental nucleic acids(eNAs),including environmental DNA(eDNA)and environmental RNA(eRNA),have garnered attention for their cost-effective and non-invasive biomonitoring capabilities.However,the accuracy of biodiversity estimates obtained through eNAs can vary among different organismal groups.Here we evaluate the performance of eDNA and eRNA metabarcoding across nine organismal groups,ranging from bacteria to terrestrial vertebrates,in three crosssections of the Yangtze River,China.We observe robust complementarity between eDNA and eRNA data.The relative detectability of eNAs was notably influenced by major taxonomic groups and organismal sizes,with eDNA providing more robust signals for larger organisms.Both eDNA and eRNA exhibited similar cross-sectional and longitudinal patterns.However,the detectability of larger organisms declined in eRNA metabarcoding,possibly due to differential RNA release and decay among different organismal groups or sizes.While underscoring the potential of eDNA and eRNA in large river biomonitoring,we emphasize the need for differential interpretation of eDNA versus eRNA data.This highlights the importance of careful method selection and interpretation in biomonitoring studies.

Interdependence between Natural Habitats and Ricefields for Rice Pest Management in the Agusan Marsh Floodplain

This paper describes how aquatic insect diversity in major natural habitats of Agusan marsh relates with nearby ricefields to determine the interdependence between them for sustainable rice production through natural pest control and for conservation of aquatic fauna in the marsh. Sampling for one year including two cropping seasons of rice production was conducted in various natural habitats of the marsh and in the adjoining rice fields. Both the natural habitats and rice fields were characterized in relation to determining habitat suitability for aquatic insects. The sedge-dominated swamp had the highest diversity among the natural habitats, while the fern-dominated swamp had the lowest. In the adjacent ricefields, diversity was similarly highest in the site near the sedge-dominated swamp, while the lowest was in the ricefields adjoining the Sago forest. Species composition of aquatic insects among the habitats differed between the wet and dry seasons. However, similarity patterns exist between natural habitats and rice fields. The closer similarity in species composition between natural habitats and ricefields indicates habitat connectivity which is an important consideration in planning and effective pest management and ecologically sound rice farming in the marsh.