The Relationship among Dissolved Inorganic Phosphate, Particulate Inorganic Phosphate, and Chlorophyll-a in Different Seasons in the Coastal Seas of Semarang and Jepara

The speciation of particulate inorganic phosphate (PIP) in waters is still rarely studied, unlike the dissolved inorganic phosphate (DIP) which is often used in the assessment of the water quality parameters and their effect on the presence of chlorophyll a. This research aimed at determinig the relationship between DIP and PIP and its effect on the concentration of chlorophyll-a. This research was conducted in the waters of Semarang and Jepara, in different seasons (Rainy and dry). Speciation from PIP was obtained through an extraction process using 1 M HCL and continued with phosphate analysis using the molybdenum blue method, as in the DIP analysis. The linear model was used to find an equation and determine the variables that affect chlorophyll a. Our results showed that the distribution patterns of DIP, PIP and Chlorophyll-a have different patterns in the two study areas and different seasons. The concentration of DIP is always high in the Semarang waters, and is followed by a high chlorophyll-a response. A different pattern was found in the Jepara waters, where the chlorophyll-a response is high in the east monsoon. The relationship of Chl-a to DIP was very significant in the west season in the waters of Semarang and the Jepara region in the east season (p < 0.05). The relationship of chlorophyll a to DIP in the Semarang and Jepara waters produced an equation, Chl a = -56.565 + 76.672 (DIP) with a coefficient of determination R² = 0.478, at a significant level (p) = 0.004 and Chl a = -25.844 + 68.827 (DIP) with value of R² = 0.421 at a significance level of p = 0.007, respectively.