Habitats and Organisms

Habitats provide shelter, refuge from predators, food resources, spawning and nursery grounds, and facilitate interaction among species. Habitat requirements vary from species to species and often change as the organism develops its life cycle.

Examples of habitat use by species

American eel in seagrass

Blue crab megalops on seagrass

Baltic clam on sand with detritus

Natural estuarine habitats in the Chesapeake Bay include shallow and deep water areas, soft-bottom sediments, sandy beaches, marshes, oyster beds, submerged aquatic vegetation (SAV), emergent vegetation, and forests. Forests along the shoreline are often the interface between terrestrial and aquatic habitats. They act as filters for nutrients such as nitrogen and phosphorus, sediment, and some chemical pollutants. Forests contribute "coarse woody debris" (CWD) to estuarine habitats when tree trunks, limbs and branches fall into the water, creating structure. CWD often functions as a refuge area from predators for many small organisms.

Habitat alteration can occur naturally by weather disturbances, such as tropical storms, hurricanes, drought, intense rainfall and winds. These may affect shoreline configurations; change depths; and add sediment, woody debris and detritus to the estuary. Generally, natural phenomena are sporadic, highly variable, and uncontrollable.

Habitat alteration by man has major impacts in Chesapeake Bay. Natural habitats such as marshes and forests are being fragmented and/or replaced with man-made habitats such as rip-rap, bulkheads, lawns and docks. Nutrient inputs from eutrophication, wastewater plants, agricultural and lawn runoff may cause eutrophication, which results in phytoplankton blooms. These blooms reduce water clarity that blocks sunlight to underwater plants (SAV). As the phytoplankton decompose, bacteria consume them and reduce the level of dissolved oxygen, i.e. hypoxia/anoxia, available to animals. Some phytoplankton are also toxic to vertebrates and invertebrates.

The oyster, Crassostrea virginica, has been decimated by over fishing, fishing gear and the unintentional introduction of parasitic species- MSX ( Haplosporiudium nelsoni ) and Dermo ( Perkinsus marinus ). Our research program measures species responses to these habitat changes.

The Rhode River, with a diverse shoreline of developed and undeveloped areas, is an excellent site for estuarine research. Scientific comparisons of upper bay tributaries such as the Rhode River to lower bay sites such as the York River can also highlight the similarities as well as differences in the sites, including the value of habitat, temperature and salinity. The upper bay has minimal SAV and oyster bed habitats with lower temperature and salinity gradients than the lower bay. These differences can delineate the life history stages such as larval development, feeding behavior, defense mechanisms and spawning of fish and invertebrates that are affected by habitat and latitudinal differences.