Effects of Aquatic Physicochemical Parameters Variation on the Phytoplankton Abundance and Diversity in the Babon River, (Semarang, Central Java, Indonesia)

The Babon River is an integral component of Semarang City's drainage system, which is heavily impacted by the influx of waste, leading to elevated water temperatures caused by global warming and decreased pH levels due to acid rain. The two main environmental factors that affect phytoplankton growth and productivity are temperature and nutrient availability. Nutrients can change the balance of the natural food webs of aquatic ecosystems. Meanwhile, metals are toxic and can accumulate in biota tissues. This study examined how nutrients, pH, temperature, and heavy metals in water affected the diversity and abundance of phytoplankton. Water samples and phytoplankton were collected from 7 observation stations representing the upstream, middle, and downstream rivers. Observations at each station were made 3 times in the months of April-May, June-July, and August-September. Temperature and pH were measured in situ with the HORIBA Water Checker. Analysis of nitrate, phosphate, and heavy metals was carried out with an AAS. The results showed that the dominant phytoplankton in the Babon Rivers consisted of Bacillariophyceae, Chlorophyceae, and Cyanophyceae. There is no diversity against all independent variables (temperature, pH, nitrate, phosphate, Cd, Total Cr, Pb concentrations) and dependent variables (number of genera, abundance, and diversity index of phytoplankton) due to the sampling station's location. However, sampling time caused diversity in nitrate, phosphate, Cd, Total Cr, and Pb concentrations, the sampling location effect was more dominant than sampling time, so the results showed that all independent variables did not contribute significantly to the dependent variables.