ENVIRONMENTAL MONITORING AT THE HUDSON RIVER
NATIONAL ESTUARINE RESEARCH RESERVE

June 15, 2005 — The Hudson River is a prime example of ecological restoration, thanks in part to the Hudson River National Estuarine Research Reserve. Two centuries of filling wetlands, altering shorelines, dumping sewage and industrial wastes had put tremendous stress on the Hudson, but 25 years of restoration and regulation have helped the river come back to life. While many problems persist, the river's wildlife — fish, birds, reptiles, shellfish and other invertebrates — are, however slowly, coming back.

Home to more than 200 species of fish, the river serves as a nursery ground for such important fish as sturgeon, striped bass and American shad. It also supports a corresponding abundance of other river-dependant wildlife, especially birds.

The river is profoundly influenced by the ocean’s tides for over half its length, creating an estuary that stretches 153 miles and includes a wide range of wetland habitats. The HRNERR sites reflect this diversity, from the brackish marshes of Piermont to the slightly brackish wetlands of Iona Island, and the freshwater tidal mudflats and marshes of Tivoli Bays and Stockport Flats.

Life of all kinds is found throughout the estuary: in tidal marshes, sand and mud flats, river shallows and in deep, open waters. These aquatic habitats are closely linked, and each plays an important role in the river ecosystem. The health of this ecosystem depends on maintaining both these habitats and good water quality throughout the estuary.

Recent research conducted at the HRNERR has provided information on freshwater and brackish tidal wetland ecology, estuarine food webs, tributary streams and non-point source pollution, wetland hydrology and water budgets, historical pollutant distributions and exotic species.

Since its designation by NOAA in 1982, the HRNERR has sought to promote responsible management of the natural resources in this estuary through research, long-term monitoring, education and training. The HRNERR is administered by the New York State Department of Environmental Conservation in cooperation with four other state agencies. The HRNERR's headquarters at Bard College Field Station on Tivoli South Bay houses laboratories, a library, herbarium, bunkrooms, boats and field gear for researchers working in the estuary. The National Estuarine Research Reserve System provides a solid foundation for the long-term research and monitoring of the HRNERR and 25 other estuarine reserves around the coastal United States and territories.

In the years since its designation, the HRNERR research and monitoring programs have steadily enhanced our knowledge and understanding of this estuary. Baseline conditions on marsh and tributary water quality and habitats have been established and long-term changes in the estuarine environment have been identified. The HRNERR’s comprehensive environmental monitoring program includes the collection of physical, chemical and biological data with sampling frequencies ranging from 30-minutes (water quality) to five-years (aquatic habitat distribution).

Reserve Site Descriptions
The estuary extends 153 miles upriver from the southern end of Manhattan Island to the federal dam at Troy, N.Y. To capture the diversity of estuarine habitats, it was necessary to designate four component sites located over the middle 100 miles of the estuary. These four sites encompass over 5,000 acres of submerged shallows, brackish and freshwater wetlands, freshwater tidal swamp and forested uplands. From north to south they are: Stockport Flats in Columbia County, Tivoli Bays in Dutchess County, and Iona Island and Piermont Marsh in Rockland County, respectively.

The two northern sites, Stockport Flats and the Tivoli Bays, are entirely composed of freshwater tidal habitats. Iona Island and Piermont Marsh are composites of brackish emergent marsh, shallows and intertidal mudflats. (Click NOAA image to the right for larger view of a map showing the four Hudson River National Estuarine Research Reserve site locations. Please credit “NOAA.”)

Reserve Estuarine Water Quality Monitoring Program
In order to identify long-term trends (years to decades) and short-term variability (daily, weekly and seasonally) in estuarine and tributary water quality, the HRNERR established a water quality monitoring program in 1991. This program, supported through the Estuarine Reserves Division of NOAA, includes two components: 1) a Long-term Water Quality Monitoring Program and 2) the NERRS System-wide Monitoring Program.

• Long-term Water Quality Monitoring Program: This component of the water quality monitoring program is designed to help distinguish between natural variability and human-induced changes in water quality by monitoring the physical and chemical variables of the surface waters entering and leaving the four reserve component sites. Once a month, HRNERR staff analyze both the tidal waters exchanged with the marshes and that entering the reserve via five tributaries. The variables measured include: water temperature, salinity, conductivity, dissolved oxygen, pH, chlorides, sulfate, dissolved inorganic nutrients (nitrate and phosphate) and suspended sediments. Since 1991, no trends in nitrate and phosphate concentrations have been observed, but there has been a significant decline in sulfate. The most striking trend identified is the increase in chlorides at four of the five tributaries flowing into the reserve over the past decade. This trend also has been observed in other watersheds in the Hudson Valley. Chlorides come from a variety of sources including road deicers, water softeners and sewage treatment (both municipal and on-site septic), but more research is needed to further identify the cause of this trend.
• NERRS System-wide Monitoring Program at the HRNEER: The NERRS System-wide Monitoring Program was established in 1995 to track short-term variability and long-term changes in estuarine waters and habitats to understand how human activities and natural events can change ecosystems. HRNERR staff have implemented the SWMP at the Tivoli Bays with four electronic YSI® 6600 data loggers deployed at both Tivoli North and South Bays, the Saw Kill and Stony Creek. Surface water samples are collected monthly at these sites and analyzed for suspended sediments, dissolved inorganic nutrients and chlorophyll-A. Once a month from April through November, samples are collected every 2.5 hours over a 30-hour sampling period at Tivoli South Bay to determine the temporal variability of water quality due to tides and time of day. All data collected under the NERRS SWMP are available from the NERRS Central Data Management Office at the Baruch Marine Field Lab in Georgetown, S.C. Currently, HRNERR staff are using these data to calculate dissolved nutrient budgets in the Tivoli Bays to determine the functional role wetlands play in removing nutrients from the Hudson River.

Aquatic Habitat Inventories
This estuarine habitat has been dramatically altered over the past 150 years. Many miles of dikes have been constructed to direct river flow energy, much of the shallow water habitat that once existed has either been dredged or filled, and railroad corridors were constructed along the river. These alterations have resulted in more than one third of the river being filled between Hudson and Troy — with additional losses throughout the remainder of the river.

Working in partnership with the NYS DEC Hudson River Estuary Program, the HRNERR is helping to map all remaining inter-tidal and submerged habitats in the estuary. The approach is to inventory the habitats, document the rate and direction of change, characterize ecological functions of the habitats and to assess the potential for restoration and enhancement. The reserve is helping to accomplished this through three projects, the: 1) Tidal Wetland Plant Community Inventory; 2) Submerged Aquatic Vegetation Inventory and Trends and 3) Benthic Mapping Project.

• Reserve Tidal Wetland Plant Community Inventory: The reserve has established an inventory of the marsh plant communities occurring at its four sites from 1991 and 1997 using aerial photography. The inventories were conducted on a large scale (1:1,200 or 1 inches = 200 feet) so that fine-scale mapping of plant communities would detect changes in plant community coverage. Results to date indicate the continued rapid expansion of common reed at all reserve sites. The HRNERR will continue to acquire the imagery every three to five years and will repeat the inventory as needed.
• Submerged Aquatic Vegetation Inventory, Trends and Functional Assessment: In an effort to better understand impacts on and change to the estuary’s SAV, representatives from state government and academic institutions teamed up to: 1) inventory the SAV and Eurasian water chestnut using remote sensing techniques; 2) determine the ecological functions SAV provide to the Hudson River Estuary and 3) conduct an outreach program to target resource users and coastal resource managers. The spatial extent of the SAV and Eurasian water chestnut makes up roughly eight percent of total river surface area with the SAV being three times as abundant (4,453 acres) as the exotic Eurasian water chestnut (1,421 acres). The results of the ecological studies clearly indicate the SAV contribute significantly to dissolved oxygen levels in the freshwater tidal portion of the estuary and provide valuable habitat for both fish and macroinvertebrates. Working with volunteers from local kayak organizations, the team hopes to gather additional fine scale data to detect short-term changes. This information will be used to enhance the remote sensing program data, which is collected only every five years.
• Benthic Mapping Project: In 1998 the reserve, working in partnership with Hudson River Estuary Program and several academic institutions, began mapping the submerged lands of the Hudson River Estuary. This is being accomplished using a suite of geophysical tools including multibeam swath sonar, sidescan sonar and subbottom profiling using CHIRP sonar and ground-penetrating radar. The geophysical data have been supplemented with sediment profile imagery and sediment sampling including cores and grabs in an attempt to link geophysical properties with biological function. Products developed from these data include acoustic images and interpretive digital maps (See image above right). The latter include maps of anthropogenic features, recently deposited fine-grained sediments, sediment grain size, bedforms, depositional and erosional areas in the estuary and river bottom morphology. The ultimate goal of this program is to better understand how the bottom of the river provides habitat for the living organisms found there. (Click NOAA image above right for a larger view of sands waved discovered on the bottom of the HRNERR using multibeam bathymetry. These sand waves are dynamic river bottom features and reach a height of three meters. Please credit “NOAA.”)

Getting the Message Out through Education and Training Programs
The information the HRNERR is gathering through its water quality monitoring and habitat inventory programs are being transferred to many audiences through the development of K-12 and adult training programs. Data gathered through the SWMP and reserve water quality monitoring programs are being used to develop a web-based curriculum for fifth grade science teachers. The increasing trends in chloride concentrations provided the foundation for a regional workshop to identify the sources and trends in salt concentration in freshwater systems. Results from the SAV Project are being transferred to a number of Hudson River audiences (including resource management, recreational boating and non-governmental environmental organizations) and has been the basis for increasing the level of protection placed on SAV for all in-river construction and recreation projects.

Relevant Web Sites
Hudson River National Estuarine Research Reserve

NOAA’S NATIONAL ESTUARINE RESEARCH RESERVES: PROTECTING THE NATION’S ESTUARIES

NOAA Oceans and Coasts Service

Media Contact:
Glenda Powell, NOAA Oceans and Coasts Service, (301) 713-3066 ext. 191 or Ben Sherman, NOAA Ocean Service, (301) 713-3066 ext. 178