Assessing phytoplankton distribution and water quality in constructed wetlands during dry and wet periods: A Case Study in USM Engineering Campus

Constructed wetlands (CW) are built to improve water quality while serving as an alternative sustainable habitat for aquatic life. In Malaysia, CWs are designed according to the guideline for Urban Stormwater Management Manual for Malaysia (MSMA 2 nd Edition) 2012. This study shall evaluate the performance of constructed wetland design as stipulated by MSMA through assessment of water quality and phytoplankton growth, which acts as a biodiversity indicator. A 5-month sampling period with phytoplankton abundance in a constructed wetland was correlated with the selected water quality index (WQI) parameters comprising dissolved oxygen (DO), ammoniacal oxygen (AN), chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solid (TSS), and pH. The constructed wetland consists of three main zones, namely the forebay, macrophytes and micropool zones. The highest WQI value was obtained from the micropool zone with a range of 78.98-85.45 (82.71±3.35) while the lowest WQI value was collected from the macrophytes zone with a range of 68.13-77.96 (73.25±3.42). A total of 15 phytoplankton species from 5 different algal phyla were identified in the constructed wetland. Phytoplankton distribution was high in the macrophytes zone (521 cell m - 3) during dry season due to high nutrient concentration as opposed to the other zones. The phytoplankton distribution was found to be closely associated with DO, AN, TSS and total phosphorus. At the same time, the macrophyte zone design also affects the distribution of phytoplankton.