Statistical analysis on alga blooming in Mikawa Bay, Central Japan using simulation results of hydrodynamic and ecological model

Abstract

The excessive algal bloom and oxygen-depleted water which are frequently observed in Mikawa Bay, have led to the growing public concern. On many marine systems, nutrient has been identified as the pollutant of concern, and is believed to stimulate the excessive alga growth. This study investigated by numerical simulation which factors may regulate the production of chlorophyll-a in the bay. We, therefore, analyze the three years calculated results using statistical method to investigate the relationship between river flow, riverine total nitrogen (TN) inputs, water temperature, bay nutrient concentration and primary productivity. Both hydrodynamic and water quality variables were calculated using a dynamic model which includes hydrodynamic equations and 13 mass conservation equations for chlorophyll-a, dissolved oxygen, etc. The obtained result are as follows:(1) chlorophyll-a has the strongest correlation with TN, and temperature, and additionally with total phosphorus (TP), (2) the flow rate of fresh water from land area was one of the most important factors to regulate TN concentration in the bay.