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FY 2002 ABSTRACTS
LINKING LAKES WITH THE LANDSCAPE: THE FATE OF TERRESTRIAL
ORGANIC MATTER IN PLANKTONIC FOOD WEBS
Principal Investigators: Dr.
Kathryn L. Cottingham, Dr.
Jay T. Lennon, Dartmouth College
Descriptors: lakes, dissolved organic matter, food webs, zooplankton,
fish, carbon, nitrogen, phosphorus, stoichiometry
Problem and Research Objectives:
In this proposal, we evaluate how terrestrially-derived dissolved
organic matter (DOM) influences the functioning of lake ecosystems.
Terrestrially-derived DOM is commonly the largest pool of carbon
in lakes (Wetzel 1992) . As such, terrestrial DOM represents a major
source of potential energy for aquatic food webs that may subsidize
higher trophic levels (including zooplankton and fish) and determine
whether lake ecosystems act as sources or sinks of CO 2 (Cole et
al. 2000) . Terrestrial DOM can also influence how lake ecosystems
respond to disturbance (Williamson et al. 1999) by attenuating
light, reducing UV transmittance and pH, and diminishing the toxicity
of pesticides and metals for aquatic biota (e.g., Jones 1992b) .
Moreover, DOM can be a major concern for municipal water supplies
because it forms carcinogenic trihalomethanes during water purification
processes (cf. Williamson et al. 1999) .
Inputs of terrestrial DOM to aquatic ecosystems may be particularly
important for managing New Hampshire (NH) watersheds. The median
concentration of DOM for lakes in the New Hampshire region (7 mg/L)
is substantially higher than the median concentration of DOM recorded
for lakes in North America and Europe (4 mg/L; Nürnberg and
Shaw 1998 ; Kalff 2001) . Therefore, NH lakes may be more tightly
linked to their surrounding watersheds than lakes in other ecoregions.
As such, NH lakes may be more vulnerable to changes in land cover,
hydrology or climate - factors known to alter inputs of terrestrial
DOM to lake ecosystems (Engstrom 1987 ; McDowell and Asbury 1994
; Gergel et al. 1999 ; Neff and Asner 2001) . This raises
some important questions: How might changing DOM inputs from land
affect the structure and function of NH lake ecosystems? Does terrestrial
DOM subsidize the diets of zooplankton and fish? Will changes in
land use alter fish abundance or productivity? We propose to address
these questions using laboratory experiments, simulation models,
and field surveys of NH lakes.
The results from our study should advance our basic understanding
of how terrestrially-derived material is used in lakes, and aid in
decision making regarding land use activities such as agriculture,
shoreline development, forestry, and wetland delineation. We will
first conduct laboratory-based studies to assess how terrestrial
DOM quantity and quality influence the production and growth efficiency
of pelagic bacteria. These two processes ultimately dictate how much
terrestrial DOM enters lake food webs. We will then incorporate the
laboratory data into a simulation model that will help us predict
the flow of terrestrial carbon in lakes with contrasting food webs
and trophic states. In particular, we will use our model to identify
the conditions under which terrestrial DOM is likely to be energetically
important for higher trophic levels. Finally, we will evaluate model
predictions by using stable isotopes ( d 13 C) to quantify the incorporation
of terrestrially-derived carbon into zooplankton and planktivorous
fish in approximately 60 New Hampshire lakes. This survey will (1)
reveal the extent to which lake organisms rely on terrestrially organic
matter and (2) provide an important complement to data that has been
collected in these lakes by other NH limnologists (including Jim
Haney at the University of New Hampshire and Carol Folt and Rich
Stemberger from Dartmouth College). Results of all aspects of the
project will be presented at national meetings and in peer-reviewed
publications. For example, preliminary results from the simulation
model will be presented in a special session on terrestrial-aquatic
linkages that JTL has organized for the American Society of Limnology
and Oceanography (ASLO) meeting in Vancouver, British Columbia, in
June 2002.
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DYNAMICS OF GROUNDWATER INFLOWS TO THE LAMPREY RIVER, NH
Principal Investigators: Dr. J. Matthew
Davis, University of New Hampshire
Descriptors: low-flow, baseflow, groundwater, surface water,
water resources, water quality
Problem and Research Objectives:
During late summer months, stream flow in the Lamprey River is largely
from groundwater sources. The proposed research will investigate
how the different hydrogeologic regions within the watershed control
the dynamics of river baseflow during periods of reduced flow.
This research will be completed using data from the U.S. Geological
Survey, New Hampshire Department of Environmental Services (NHDES),
and the National Oceanic and Atmospheric Administration (NOAA), field
measurements on selected study sites, and a combination of groundwater/surface
water models to analyze and quantify groundwater inputs to the Lamprey
River. The Lamprey River Watershed is an important component of the
water resources of the seacoast region of New Hampshire and is similar
in climatology and hydrogeology to many watersheds in New England.
The Lamprey serves as a water supply for municipalities including
Deerfield, Raymond, Epping, and Newmarket, as well as serving as
an auxiliary water supply for Durham and the University of New Hampshire.
Current activities within the watershed, including a proposed bottled
water plant near Northwood, may result in changes to the aquifer
system. Forecasting and potentially mediating late summer low flow
conditions in the Lamprey (and other similar rivers in the region)
are critical to effectively managing these resources.
In addition to the Lamprey's importance as a water resource, an
11.5-mile stretch of the Lamprey River from Newmarket to Lee was
declared a National Wild and Scenic River. With this declaration,
several restrictions were initiated, including policies against new
dam and water transfers; water quality; channel alterations; new
solid-waste facilities; and protected in-stream flows. These restrictions
protect both the stream and surrounding ecology from future effects
of population growth in the region. An important factor in protecting
stream ecology is the dynamics of the river during reduced flows.
During reduced flow periods, a large percentage of surface water
flow is derived from groundwater inputs (Perkins and Sophocleous,
1999; Harvey and Bencala, 1993; Cey et al., 1998). However, little
research has been conducted to quantify inputs to the Lamprey River
discharge from sources such as stratified drift aquifers, bedrock
aquifers, and springs. Previous work on low flow systems in New England
(Dingman and Lawlor, 1995; Risley, 1994; Barnes, 1986; and Kliever,
1996) have focused on the statistical methods of determining low
flows rather than the source of water during these periods. The proposed
research is unique in that the primary goal will be to understand
and quantify sources of water during reduced flows rather than estimating
the magnitude and frequency of low flow periods.
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CHARACTERIZATION OF GROUNDWATER DISCHARGE TO HAMPTON HARBOR
Principal Investigators: Dr.
Thomas Ballestero, Dr. Robert Roseen, University of New Hampshire
Descriptors: thermal infrared, groundwater discharge, nutrients,
pollution, coastal management, coastal, estuary
Problem and Research Objectives:
Contamination of coastal waters from groundwater discharge is a
considerable problem that historically is very difficult to quantify.
Coastal Managers across the nation recognize nutrient enrichment
as one of the most serious problems in coastal areas. In estuarine
environments such as these, nitrogen is the main contaminant of concern.
Previous efforts have focused on dissolved inorganic nitrogen (DIN)
and potentially missed dissolved organic nitrogen (DON). DON and
DIN may be necessary to evaluate total nitrogen loading. Analyses
for dissolved organic carbon (DOC) will also help ascertain the potential
for DON. Recent research within the Great Bay Estuarine System indicates
that groundwater discharge to the bay is extensive and in many cases
carries a significant DIN load. This is consistent with other researchers
that have identified groundwater inflow to coastal areas as a very
significant fraction of the total fresh water flow to coastal waters,
and in some cases even exceeding contamination from surface waters.
Perhaps more importantly, this nitrate-rich groundwater may be the
dominant freshwater source to an estuary during the low flow summer
months when oxygen-depletion is most critical. Oxygen-depleted waters
have been observed in some of the tributaries of the Great Bay Estuary.
Oxygen-depleting substances and nutrients are the leading stressors
upon estuarine ecosystems, as reported by the USEPA.
The funds requested will support further breadth of analysis of
nitrogen contamination. Specifically, the requested funds address
dissolved organic nitrogen and dissolved organic carbon to complement
existing efforts analyzing dissolved inorganic nitrogen. The combination
of DON and DIN should enable a clearer understanding of the total
nitrogen loading. Furthermore, the proposed research will further
test and evaluate a developing methodology for assessing estuarine
contaminant loading from groundwater. Contaminant loading estimates
are an integral part of effective resource management. Unregulated
non-point sources, such as groundwater, are difficult to estimate,
as they are typically not monitored. These estimates are the foundation
of current regulatory approaches including the determination of Total
Maximum Annual Loads. In order for coastal managers to protect and
preserve coastal areas, an accurate assessment of contaminant sources
is needed including knowledge of the magnitude and water quality
characteristics of ground water flowing into the coastal system.
Thus, effective management, mitigation strategies, and development
of Best Management Plans requires a thorough understanding of the
issues and processes that affect an ecosystem.
Recent research in thermal infrared imagery coupled with field verification
has been shown to be an effective and affordable means to assess
groundwater discharge. A direct assessment of groundwater discharge
to coastal waters may be more reliable than conventional methods
in that it evaluates the groundwater at the point of discharge into
surface waters. Comparative means rely upon forecasting to predict
the flow and the rate of transport. Errors in subsurface characterization,
non-point source load budgets, as well as potential unknown contaminant
sources will contribute to errors in loading and discharge estimates.
Many of these errors may be unavoidable due to limited budgets that
restrict thorough site characterizations. However, thermal infrared
imagery obviates the need to address the upgradient factors as point-of-discharge
observations inherently include these influences. Only after contamination
has been observed and mitigation is chosen is it necessary to address
these issues of land use impacts.
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EFFECTS OF LAND USE ON WATER QUALITY IN A CHANGING LANDSCAPE
Principal Investigators: Dr. Jeffrey
Schloss, Dr. William McDowell, University
of New Hampshire
Descriptors: lake, stream, water quality, nutrients, land use
Problem and Research Objectives:
The waters of New Hampshire represent a valuable water resource
contributing to the state's economic base through recreation, tourism,
and real estate revenues. Some lakes and rivers serve as current
or potential water supplies. For most residents (as indicated by
boating and fishing registrations) our waters help to insure a high
quality of life. As documented in the 2000 Census, New Hampshire
currently leads all of the New England states in the rate of new
development and redevelopment. The long-term consequences of the
resulting pressure and demands on the state's precious water resources
remain unknown. Of particular concern is the response of our waters
to increasing non-point source pollutant loadings due to watershed
development and land use activities. While in-depth watershed nutrient
budget measurements and modeling have been attempted on a small number
of watersheds scattered throughout the state, these studies represent
only short-term examinations of non-point source pollution nutrient
loading. Only a longer-term monitoring program conducted through
differing weather years can adequately document the cumulative effects
of land use change, quantify the effectiveness of a watershed management
program, or assess the accuracy of a specific model of water quality
at the landscape scale.
The proposed investigation would allow for the improvement of predictive
models used for watershed planning and management. The benefits of
this would include 1) assisting watershed stewardship education efforts
throughout the state and region; 2) providing existing watershed-based
programs like the EPA Basins Model Initiative, the statewide Unified
Watershed Assessment Initiative (under the federal Clean Water Action
Program) as well as regional initiatives (US EPA Region 1 and NE
states) data needed to develop total maximum daily loading criteria
(TMDLs) and nutrient criteria for lakes, rivers and streams; and
3) complementing ongoing efforts to predict receiving water response
to nutrient loading for source water protection planning. New data
generated by this project will be included in our submissions to
EPA's new STORET and will be used use in a collaborative, web-based
water quality data distribution project between UNH and the NH Department
of Environmental Services.
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