Phytoplankton growth is influenced by the presence of nutrients N (nitrogen) and P (phosphor). Each region has a specific N/P ratio, due to the influence of anthropogenic inputs. This study aimed to assess the response of phytoplankton chlorophyll-a (Chl-a) biomass due to differences in N/P ratio by the influence of river flow in the north coast of Java; Jobokuto Bay (Jepara), the coastal waters of Semarang and the front of the Cisadane river. N-nutrients were analyzed in the form of N-NO3 (nitrate), and N-NH4+ (ammonium ions), and orthophosphate ions (P-PO42-). Nutrient analysis was spectrometric, using the reduction methods (nitrate), ammonium (indophenolblue), and phosphate (molybdenum-blue). Test for site differences using Kruskall-Wallis, followed by a posthoc test. The results showed that Semarang waters had a lower N/P (Stoichiometric) ratio than Jepara and Cisadane, which can be used to predict that P nutrient input is higher than N. This high P input impacts microalgal development (chlorophyll-a). In addition, we also found Semarang waters to have higher speciation of inorganic N in the form of ammonium, which is one of the drivers of eutrophication in these waters. The use of a ratio of N/P is very important in estimating the eutrophication process and can be used to estimate the dominance of nutrients entering the water due to anthropogenic activities in the upstream area.
Microplastics (MPs) are discovered in various places even encroaching on marine protected areas (MPA). The aim of this research is to investigate the occurrences of MPs pollutant in MPA and non-MPA in Karimunjawa National Park (KNP). The results showed that MPs from sea surface water were higher in MPA than non-MPA with range as 47.89–106.20 items/L, dominated by fragment, 1–50 µm size, black color and HDPE, LDPE, PP, Nylon, PVC, ABS, and PET in polymer types. It induced since it supplied from it surrounding, specifically the south of MPA, whereas there have been cottage constructions generating many marine debris. These findings indicate that occurrence of MPs still dominantly influenced from anthropogenic activity. However, the hydrodynamic and MPs characteristic as well play an important role in MPs distributions.
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