In 1998, DO levels remained fairly high for most of the summer at Shelltown. Oxygen levels increase when the bloom is occurring, as the photosynthetic phytoplankton produce oxygen. After nutrients run out and the bloom has run its course, the algae are consumed by decomposers, which use dissolved oxygen as part of the decomposition process. This indicates that the water of the Pocomoke River near Shelltown maintained oxygen levels high enough to support fish and other aquatic life for nearly the whole summer. It follows that as the water temperature increases over the summer, the amount of oxygen that can be dissolved in water decreases, meaning that the same amount of dissolved oxygen will yield a higher saturation percentage.
Daily fluctuations are visible in the oxygen levels, especially during the summer months.
As the water warms up during the daytime, it can hold less oxygen, and the increased temperatures are ideal physical conditions for algal growth. Since phytoplankton are photosynthetic, they produce oxygen during periods of sunlight, increasing the dissolved oxygen levels in the water column. During the night time, these algae use up oxygen through the process of respiration, decreasing dissolved oxygen levels in the water column. Back to top Salinity levels are a result of a few separate factors. Generally, salinity increases as a river or water body nears the ocean.