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As had been noticed by many crossing the Bay Bridge , the surface water in the Bay at the end of April was greenish in appearance . Boat wakes are often visible as dark lines, as the passing boats bring up the more clear deeper water. Water temperatures at Sandy Point had been much cooler than normal in April, setting a new record at 46 degrees- a full 4 degrees cooler than the previous record, and only one degree warmer than the water had been in January. Towards the end of the second week in April, over two inches of rain fell in parts of the Susquehanna Valley . The runoff from this event was evident in the turbidity spike detected on April 16 at the Havre de Grace real-time monitoring station. By the next day, the station at the mouth of the Sassafras at Betterton was in the plume of this runoff, and 5 days later the nutrients in this runoff, combined with the warming temperatures and sunshine, triggered the algae bloom now visible under the bay bridge, and detected by the elevated levels of Chlorophyll a at the Sandy Point station (figure 1 and 2).
Figure 1. Turbidity and Chlorophyll measurements from April rain event
Figure 2. Turbidity Plume as seen on April 21, 2007 As part of Maryland Department of Natural Resource's routine sampling program, water samples were collected on April 23rd from Sandy Point . The Diatom Cyclotella (297,180 cells/mL) and green algae Quadricoccus euryhalinicus (24,765 cells/mL) were probably the two species creating the color in those areas. These two species are commonly found in Chesapeake Bay waters. The Department will continue to monitor this and other blooms, and all information will be posted at MDDNR's Eyes on the Bay website.
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