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Using the Benthic Studies

Using Benthic Mapper




Using the Benthic Studies

Benthic Mapper's data and interpretive maps provide a unique body of detailed information about the Hudson River and its resources. Benthic Mapper does update some data gathered in earlier years, but most of the information it displays is new. Both the data and interpretive displays are valuable in numerous ways for understanding and preserving the river.

Benthic mapping data products have important implications for several areas, including habitat management, sediment and contaminant transport prediction, oil spill response, navigation, preservation of historic resources, law enforcement, and change prediction.

Updated Depth Measurements Help Assess Changes in the River

The bathymetric data set collected as part of the benthic mapping project is by far the most reliable description of water depths in the estuary today. Most of the data used to generate the navigational charts of the estuary were collected in the 1930s. Comparing recent data with older data provides a way to assess how the estuary has changed over time.

Habitat Management is Prime Application

Habitat Management is the most immediate application of Benthic Mapper. Anglers and fisheries scientists are interested in the variability of the submerged landscape. Different parts of the estuary floor may be used by fish to fulfill different needs. For instance, the large sediment waves found between Kingston and Saugerties may provide refuge for fish during the winter months. With low water temperatures of winter rendering the fish effectively dormant, the troughs of these sediment waves might be sheltering lethargic fish from currents that could wash them out of the estuary.

Sediment Measurements Help Understand Biota

The distribution of invertebrate animals and other food for fish on the estuary sediments depends, among other things, on the type of sediment at a given place on the estuary floor: soft muddy sediments will support different invertebrates from those found on sandy sediments or hard rock. A map that shows hard and soft sediments will reveal areas that feed fish populations in different ways.

Generally, a hard or sandy bottom is represented by darker (more reflective) areas on the sidescan sonar displays. The hardness and stability of the sediments may have a direct influence on the distribution of invertebrate animals on the estuary floor. Areas where sediments are being moved by river currents are not likely to be good homes for many bottom dwelling animals, though other bottom-dwelling animals may prefer areas where swift currents bring food to them. Our maps of sediment wave fields indicate areas where sediment is in motion along the river floor.

To check the accuracy of acoustic methods to map sediment type, DEC fisheries personnel have begun a sampling program that will show whether blue crabs prefer to live on hard or soft sediment. In that program, sediment found on crab traps will be collected to see if that sediment corresponds with the sediment type mapped by acoustic methods.

Predicting Contaminant Transport

Maps of areas where sediment is being eroded from or deposited to the estuary floor indicate how the river floor is changing with time. These maps also help us map movement of sediment through the estuary. To the extent that many contaminants in the estuary are associated with sediments, we can use maps of sediment transport to map contaminant transport.

In shallow waters, maps of sediment types can aid in development of contingency plans for oil and other hazardous material spill response in different parts of the river.

Treasures Revealed?

Acoustic data collected as part of the benthic mapping project has revealed a number of shipwrecks on the estuary floor, some of which may have significant historic value. As possible historic treasures, these deposits are protected by New York State law. The New York State Historic Preservation Act of 1980 states, "The legislature determines that the historical, archeological, architectural and cultural heritage of the state is among the most important environmental assets of the state and that it should be preserved." Locating shipwrecks is a first step in developing a management plan to evaluate and preserve such treasures.


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