Asterionella japonica      Polykrikos kofoidi      Thalassionema nitzschiodes      Gyrodinium uncatenum       Prorocentrum micans

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Bay Bridge



MD Mid Bay - Choptank

Bluegreen Algae Trends in the Potomac during Low Flow and High Flow Years

Phytoplankton (algae) communities reflect existing nutrient levels. An over abundance of nutrients often results in dense algae blooms. These blooms reduce light penetration thereby reducing the chance that beneficial submerged aquatic vegatation will grow. Oxygen levels are also impacted. Extremely dense algal blooms send oxygen levels skyrocketing on sunny days while the algae are photosynthesizing. At night or on cloudy days their large numbers can use up all the oxygen from the water column leaving aquatic animals (fish) to suffocate. In lesser densities algal blooms burden the system when they die. The decomposition of their dead cells can use all the oxygen available in the bottom waters. Excess nutrients also alter the structure of the phytoplankton community. Just as weeds can take over a garden tolerant (bluegreens) or opportunistic species (pigmented flagellates) can dominate. This alteration of the algal community can cause several problems. An excess of bluegreen algae in the water column can cause a green latex paint appearance to the water surface (Potomac-Indianhead). An over abundance of pigmented flagellates can impart a coffee color to the water (Mahogany Tide). This problem is more common in small tidal creeks (Patapsco drainage) from late spring to late summer.  The graphs generated for these sites will show how the phytoplankton community in the Bay and tributaries change from one month to the next not only in the number of algae present but also in the general kind of algal groups present. By comparing the graphs you can track the changing algal community. The data graphed is mostly from surface grab samples, although bottom samples for phytoplankton are collected for two stations (Chesapeake Bay-Cedar Pt. and Chesapeake Bay-Sandy Pt.). This is also graphed.

This page was created by Walter L. Butler any comments or suggestions should be forwarded to Email address

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