The Effect of Physico–chemical Parameters on Cochlodinium polykrikoides Abundance in Sepangar and Likas Bays, Sabah
Encik Weliyadi and Ann Anton
Faculty of Fisheries and Marine science, Borneo University of Tarakan, Amal lama Street. No.1. Tarakan City, North Borneo. Indonesia
Unit for Harmful Algal Bloom Studies (UHABS), Borneo Marine Research Institute (BMRI), Universiti Malaysia Sabah, Locked Bag No. 2073, 88999 Kota Kinabalu Sabah, Malaysia
A study on the effects of physical (temperature) and chemical parameters (salinity, pH, nitrate, total ammonia, nitrite and phosphate) on the occurrences of Cochlodinium polykrikoides was carried out in the coastal area of Sepangar and Likas bays off Kota Kinabalu, Sabah. The objectives of this study were to determine the temporal and spatial variations of C. polykrikoides cell abundance, to determine the physical and chemical parameters of the coastal water, and to establish the correlation between C. polykrikoides bloom occurrences and physico-chemical parameters in the coastal water of Sepangar and Likas Bays in order to determine causal factors. Sampling was conducted between December 2007 to August 2008. Eight sampling locations were chosen: four stations (1 to 4) were located in the bays (Likas and Sepangar Bays) and four stations (5 to 8) situated at the river mouth (Inanam-Likas and Menggatal rivers). Physical and chemical parameters of seawater were measured at stations 1 to 4. Phytoplankton samples of C. polykrikoides were taken only at stations 1 to 4. Meanwhile, stations 5 to 8 were choosed to measure the Nitrogen (N) and Phosphorus (P) loading. The results of the study showed that the maximum cell density of C. polykrikoides was observed on the 2nd week of February 2008 at Station 2, with a value of 1.3 x 107 cells L-1. The highest peak of C. polykrikoides was recorded during the northeast monsoon (NEM) at station 2. High cell densities of C. polykrikoides were mostly observed at Stations 2, 3 and 4, which are situated near the Kota Kinabalu coastline. Statistical analyses using Spearman Correlation Tests revealed that there was no correlation between temperature (r2=-0.45, p>0.05), salinity (r2=-0.34, p>0.05), pH (r2=0.03, p>0.05) on the occurrences of C. polykrikoides in this study. Temperature, salinity and pH of seawater showed similar ranges either during bloom or non-bloom period. Blooms of C. polykrikoides were observed at temperature, salinity and pH ranges of 25.7–31.4 oC, 29.6–32.8 psu and 7.7–9.1, respectively. During non bloom periods of C. polykrikoides, the temperature, salinity and pH ranges recorded were 28.5–31.9oC, 29.6–33.0 psu and 7.9–9.2, respectively. Meanwhile, there was a positive correlation between the concentration of nitrate (r2=0.798, p<0.05), and phosphate (r2=0.743, p<0.05) on C. polykrikoides cells densities. However, no correlation was observed between Nitrite (r2=-0.26, P>0.05) and total ammonia (r2=0.344 p>0.05) on cells densities of C. polykrikoides. The fluctuation of chemical parameters of nitrate and phosphate were influenced by the rainfall and also the freshwater outflow from Menggatal and Inanam-Likas rivers. Both rivers transported high P and N loading to the bays stations. Nitrate and phosphate concentration were found higher at stations near Kota Kinabalu coastline (2, 3 and 4) compared to the offshore station (Station 1). Rainfall may have triggered N and P loading in Menggatal and Inanam-Likas Rivers, resulting in the bays stations receiving nutrients from both rivers and subsequently causing blooms of C. polykrikoides.
Keywords: harmful algal blooms, nutrients, C. polykrikoides, eutrophication
The picture above shows the nitrate+nitrite analysis process by using reduction column in the laboratory.