Grantee Research Project Results
2002 Progress Report: An Integrative Aquatic Ecosystem Indicator
EPA Grant Number: R826591Title: An Integrative Aquatic Ecosystem Indicator
Investigators: Stemberger, Richard S. , Miller, Eric K.
Institution: Dartmouth College
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1998 through June 30, 2003
Project Period Covered by this Report: October 1, 2001 through June 30, 2002
Project Amount: $888,661
RFA: Ecological Indicators (1998) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
The objectives of this research project are to:
- Evaluate metrics based on the carbon (C), nitrogen (N), and phosphorus (P)
supply of the total dissolved plus seston fraction of lake water as indicators
of the character of lake zooplankton assemblage.
- Establish the relationship between water transparency and zooplankton body
size and assemblage structure with suspended particulate matter (algae and
particulate carbon in size range available as food for zooplankton).
- Establish the strength of the relationship between the relative C, N, and
P supply from the watershed to the C, N, and P supply to the lake. We will
test the hypothesis that N:P, C:N, and C:P ratios in lake water and watershed
C, N, P supply to lakes are significantly influenced by landscape factors
related to human land use activity, forest ecosystem composition, and regional
air pollution gradients.
- Conduct a landscape characterization analysis of features in the lake-watershed
basins that in conjunction with concurrent watershed-associated stream and
groundwater measurements, will be used to develop proxy measures for expected
relative C, N, P supply conditions for lake water.
- Establish zooplankton assemblage-derived variables that reflect risks to
ecosystem function, structure, or human health as a function of the elemental
supply gradient. These risks include food web simplification reflected by
assemblage-derived structural indices such as chain length and linkages, the
availability of oxic cold-water habitat, algal turbidity, UV/B and aluminum
toxicity, and bioaccumulation and transfer efficiency of toxins.
- Conduct a thorough analysis of the sensitivity of zooplankton metrics using the spatially extensive dataset in this study and from the existing lake datasets. These analyses will establish statistical confidence and power to detect change for measures of lake integrity. We expect to demonstrate that the proposed relative C, N, P supply indicator can provide a simple, inexpensive and practical approach to evaluating aquatic ecosystem integrity within the context of the terrestrial environment.
We have established relationships between the dissolved and particulate forms of C, N, and P in 59 northeastern lakes with zooplankton assemblage structure, lake tributary inputs and watershed land use and forest cover characteristics which provides the basis for a multitier indicator for monitoring lake integrity. Complex species assemblages are aggregated into simple consumer guilds that represent body size and biomass attributes of the assemblage. Grazing efficiency of zooplankton on suspended particles in the size range of 0.2-40 µm, such as bacteria, detritus, and algae depends on body size and species composition. These consumer groups also broadly reflect the relative N and P intracellular requirements of species. Grazing efficiency is a key factor controlling water transparency in lakes; hence, identifying key zooplankton indicators that are strong drivers of water transparency is important in understanding variation and trends in lake trophic condition as measured in typical volunteer lake monitoring programs. Furthermore, element supply ratios correlate to a variety of potential risks to lake ecosystem function, such as the loss of the cool-water refuge, bioaccumulation of toxins, algal turbidity, acidification and UV/B toxicity. These risks also are associated with zooplankton assemblage structure along a gradient from high to low lakewater N:P ratios.
Progress Summary:
In our three field seasons, we conducted experiments for 59 lakes, and sampled 158 tributaries in Adirondack Mountain and Saint Lawrence Valley Regions of New York, Vermont, and New Hampshire, for a total 138 lake visits. We also have established good evidence for the direct connection between conditions in the lake watershed and lakewater, C, N, and P supply in tributary streams and receiving lake basins. Dissolved organic matter (DOM) produced in soils such as humic and fulvic acids have a much higher proportion of carbon contained in carboxylic and phenolic group structures than does the dissolved organic carbon (DOC) excreted by aquatic biota. There also is variation in the proportion of DOC present in these chemical groups that reflects the source and decomposition history of the terrestrial organic matter. A measure of the carboxylic and phenolic group content of DOM can therefore be used as an indicator of different sources of DOM in lake ecosystems. In our sample, this indicator is highly correlated between lake water and associated tributary streams. This provides us with good evidence of a direct connection between watershed release of DOM (containing DOC, dissolved organic nitrogen, (DON), dissolved organic phosphorus (DOP), and dissolved carbon and nutrient supplies to lake water. In support of this watershed-lake connection, temporal average lakewater chemistry is significantly correlated to temporal average tributary water chemistry indicators across the wide range of lake and watershed types in our sample.
We developed a zooplankton body size indicator that helps to explain variation in Secchi depth visibility and should be a useful tool for lake management applications. We show that zooplankton size is as important or more important in determining lakewater transparency as commonly measured indicators, such as phytoplankton measured as chlorophyll a, total phosphorus, and water color. Species composition and body size are driven by the intensity of predation by forage fish. Large zooplankton are more efficient at grazing algae than are small-bodied species. Assemblages dominated by small-bodied species reflect systems where game fish populations do not control populations of small forage fish species. Consequently, light transmission decreases in lakes because algae can grow under reduced grazing pressure by small species. We also show that body is remarkably consistent as a predictor of transparency across the majority of our time series collected primarily on six lakes in the 2001 survey.
Experimental Evaluation. In 1998, we performed experiments in 1,000 L cattle tanks to evaluate the taxonomic and body size responses of zooplankton to additions of N, P, and fish. Nutrients had striking effects on taxonomic structure of the assemblages: P stimulated the abundance of cladocerans and rotifers while N increased the abundance of copepod nauplii, cyclopoid copepodites, and rotifers. Fish reduced body sizes of crustacean zooplankton independent of taxonomic grouping. Populations of microzooplankton such as copepod nauplii, cyclopoid copepodites, small cladocerans, and rotifers also increased significantly with fish. Observed taxonomic responses to nutrient additions are consistent with mineral limitation on growth rates presumably mediated through the N:P ratio in the algal food.
Empirical Evaluation. We evaluated zooplankton assemblages of northeastern U.S. lakes with respect to 17 environmental factors, including those tested in the above experiment. The results of this analysis identified a major gradient which contrasted low N:P ratio taxa (small cladocerans, cyclopoid copepodites, nauplii, and rotifers) with high N:P ratio taxa (calanoid copepods). The primary explanatory variable was chlorophyll a, which was positively and significantly correlated to N and P concentrations (i.e., decreasing N:P ratios). The analysis of field populations generally corroborated the results from the experiment fish and the N:P ratio were significant factors, but subordinate to chlorophyll a, total dissolved aluminum, pH, and DOC. The results from the experiment and analysis of natural assemblages support nutrients and their supply ratios as significant factors controlling broad taxonomic structure in lakes. The analysis also provides strong statistical correspondence among zooplankton metrics with risk factors such as aluminum toxicity and low pH.
We continue this analytical approach with our more detailed data set that includes the nutrient concentrations within major size fractions of lake water particles of algae and detritus.
The landscape characterization task involves both field and geographical information systems (GIS)-analysis components. During fall 1999, we visited 10 forested tributary riparian zone locations to examine field characterizations that included vegetation survey, leaf-litter sampling, and soil characterization and sampling. Preliminary results indicate significant variation in soluble, transportable (measured by incubation and extraction) N and P in soils as a function of dominant forest species. Soils occupied by forest species adapted to low N environments (e.g., red spruce) had higher transportable (soluble + extractable) P, while soils occupied by some deciduous species (e.g., American beech) had higher transportable N and lower P. This produced a range of N:P ratios of readily transportable materials in soil from 79 to 1,070. Our observations are consistent with expectations, based on the relative nutrient demand of different forest species. These results support the idea that variation in forest composition and forest nutrient cycling is partially responsible for landscape scale variation in N and P supply to aquatic systems. We have continued to develop the foundation data layers (topographic factors, land cover, forest type, soils, hydrology, climate, and atmospheric deposition) of a regional GIS that will be used for characterization of the study watersheds. The generation of watershed and riparian zone overlays for our study systems is in progress and should be completed over the next few months.
Sensitivity analysis of zooplankton population and richness indicators was conducted using data from 365 lakes provided by the U.S. Environmental Monitoring and Assessment Program (EMAP) (Stemberger, et al., 2001). Sensitivity (ability of zooplankton indicators for detecting lake-to-lake differences) increased when spatial scale of the entire study region was classified according to natural subregions such as the Adirondack Mountains, coastal/urban zone, New England uplands, and Hudson-Mohawk Valleys/lake plains. Calanoid copepods were the most sensitive indicators, having up to 95 percent of their variance attributed to lake-to-lake differences. Therefore, this group would be especially useful for use in regional monitoring. Rotifers, cyclopoid copepods, small cladocerans, and minor zooplankton groups had low sensitivity irrespective of spatial scale. This suggests that other environmental factors must be evaluated in partitioning the data such as lakewater nutrients and watershed influences. However, this analysis also demonstrates that zooplankton are about on par with other biological indicators that have typically been used in monitoring programs such as benthos, fish, fossil diatoms, and aviafauna.
Future Activities:
We will have our database completed in winter 2002 and we will continue analysis, interpretation, and manuscript preparation over the remaining funding period and beyond.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 27 publications | 12 publications in selected types | All 11 journal articles |
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Type | Citation | ||
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Chen CY, Stemberger RS, Klaue B, Blum JD, Pickhardt PC, Folt CL. Accumulation of heavy metals in food web components across a gradient of lakes. Limnology and Oceanography 2000;45(7):1525-1536. |
R826591 (1999) R826591 (2000) R826591 (2001) R826591 (2002) |
not available |
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Evans CA, Miller EK, Friedland AJ. Effect of nitrogen and light on nutrient concentrations and associated physiological responses in birch and fir seedlings. Plant and Soil 2001;236(2):197-207. |
R826591 (2001) R826591 (2002) |
not available |
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Stemberger RS, Miller EK. A zooplankton- N:P-ratio indicator for lakes. Environmental Monitoring and Assessment 1998;51(1-2):29-51. |
R826591 (1999) R826591 (2000) R826591 (2001) R826591 (2002) R826591 (Final) |
not available |
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Stemberger RS, Larsen DP, Kincaid TM. Sensitivity of zooplankton for regional lake monitoring. Canadian Journal of Fisheries and Aquatic Sciences 2001;58(11):2222-2232. |
R826591 (2001) R826591 (2002) R826591 (Final) |
not available |
Supplemental Keywords:
air, water, watersheds, limnology, ecology, ecological effects, ecosystem, indicators, aquatic, terrestrial, Environmental Monitoring and Assessment Program, EMAP, modeling, geographic information systems, GIS, Northeast, algae, detritus., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Nutrients, Ecology, Hydrology, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Air Deposition, Drinking Water, Geology, Watersheds, Ecological Indicators, nutrient transport, aquatic ecosystem, environmental monitoring, nutrient supply, ecological effects, ecological exposure, risk assessment, EMAP, carbon cycling, algae, multi-level indicators, bioavailability, other - risk assessment, algal growth, chemical transport, ecosystem indicators, terrestrial, aquatic ecosystems, phosphorus, carbon storage, integrative indicators, lake ecosystem, landscape characterization, land use, nitrogen, atmospheric depositionProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.