A particular estuary shows periodic changes in the coloration of water. During the summer, water in the estuary appears greener than in winter. What can be the cause of this cyclic change in water color? A. The change in color is because by the change in tides that promotes the growth of algae. B. The change in color is caused by the decreases the growth of phytoplankton during winter. C. The change in color is caused by the decrease in water salinity due to more fresh water flowing during winter. D. The change in color is caused by an increase in oxygen due to the drop in temperature during winter.