IDENTIFICATION OF INFLUENCE OF THE RISK FACTORS TO ALGAL BLOOM IN FRESH WATER RESERVOIRS USING MULTINOMIAL LOGISTICS REGRESSION

Harmful algal blooms are the increasing rapidly in most of the water courses around the world and in Canada. There is still no explanation about its occurrence and growth. HABs are a serious issue in freshwater reservoirs, marine water around the world. HABs are not a new thing to the fertile regions of world (Carmichael and An [5]). However, climate change and increased environmental pollution has brought a big rise in its growth, and it is mostly affecting small lakes, drinking water reservoirs, ponds, rivers and oceans as well around the globe (Backer et al. [2]). Rise in temperature and other nutrients (e.g. pH, dissolved oxygen etc.) are key risk factors, causing the quick growth of algal blooms. In this paper we used deterministic statistical approach to simulate the growth of harmful algae under environmental factors that can lead to bloom pattern in water reservoirs of Moncton city (Canada) with the collected data over the period of four years 2016-2019. Temperature, total phosphorus (TP), dissolved oxygen, pH are the risk factors which are affecting the growth of algal bloom in fresh waters. Descriptive and inferential statistics were used to explore the risk factors which are DO, TP and temperature colimits primary productivity in lakes of the response variable Chlorophyll-a (Chl-a). Our data was categorized under eutrophication index of fresh water (Nguyen-Quang et al. [15]). Odds ratio and 95% confidence interval were computed by using MLR model. The results showed that multinomial odds ratio, confidence interval and significant value for total phosphorus of chlorophyll over reference category are 0.996 and (0.969-1.023) and 0.761, for DO are 1.325 and (1.194-1.470) and 0.00 and for temperature 0.900 and (0.857-0.945) and 0.00 respectively. Also multinomial odds ratio, 95% confidence interval and significant value for total phosphorus of high risk category of chlorophyll over reference category are 0.932 and (0.874-0.994) and 0.033, for DO are 1.042 and (0.930-1.168) and (0.481) and for temperature 1.033 and (0.980-1.089) and (0.222) respectively. According to results the independent variables DO and temperature plays significant role for outcome variable Chl-a at medium risk category over reference category and the independent variable TP shows significant role for outcome variable chlorophyll at high risk category over reference category. High activity is recorded in the growth of Chlorophyll-a with the increase of TP and temperature and dissolved oxygen (DO) influence the response variable much. Significant developments were seen under High TP and temperature and DO.