Drought Impacts on Maryland 
and Chesapeake Bay

Impacts on Plants and Animals in the Chesapeake Bay
The combined effects of low flow and higher salinity have potentially serious implications for living resources. All species of plants and animals are adapted to certain environmental conditions or ranges in conditions. For example, certain species of bay grasses are adapted to saline environments, others to freshwater environments, and still others to zones that transition from saline to fresh. Bay grasses cannot “move” if the salinity in a particular area dramatically changes. When the salinity gets too high or too low for a particular bay grass species, bay grass beds may die off in the affected area. This may result in reduced food supplies for waterfowl, decreased habitat for juvenile crabs and finfish, and increased re-suspension of sediments

This photo shows decreased water levels as a result from the 2002 drought.

Oysters may also be affected by changes in salinity. For example, although areas with salinity less that 5 ppt do not provide good habitat, high salinities encourage the growth of Dermo and MSX, two diseases that kill developing oysters. The February-March bloom of the toxin-producing alga Dinophysis accuminata may also be related to the unusually high salinities that have occurred in the lower Potomac River (see Ragged Point on the Current Conditions web page). A bloom of such magnitude, which has resulted in the closure of shellfish beds to harvesting, had never been observed in the Chesapeake Bay before this occurrence.

The encroachment of high salinity water into typically fresh water areas also limits the amount of spawning habitat for species such as yellow perch (Perca flavescens), white perch (Morone americana), and striped bass (Morone saxatilis). These fish must then move even further upstream into low salinity areas to spawn.

Finally, drought conditions increase water residence times in the tributaries, which can result in large algal blooms because phytoplankton populations have extended periods to grow in nutrient rich waters. When the blooms die off and sink to the bottom waters, bacterial decomposition of the phytoplankton mass consumes oxygen and results in hypoxia. Large areas of low dissolved oxygen further restrict the amount of habitat for aquatic species.

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