Grantee Research Project Results

2001 Progress Report: An Integrative Aquatic Ecosystem Indicator

EPA Grant Number: R826591
Title: 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, 2000 through June 30, 2001
Project Amount: $888,661
RFA: Ecological Indicators (1998) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration

Objective:

In this project, we establish a relationship between the dissolved and particulate sources of carbon (C), nitrogen (N), and phosphorus (P) in lake water and tributary sources with watershed land use and forest cover. Our goal is to integrate watershed, lake, and pelagic zooplankton assemblages in a multi-tier ecological indicator for monitoring lake integrity. Complex species assemblages are aggregated into simple consumer guilds that reflect relative N and P intracellular requirements of species. Element supply ratios correlate to a variety of potential risks to lake ecosystem function such as loss of the cool-water refuge, bioaccumulation of toxins, algal turbidity, acidification, and UV/B toxicity. These risks are associated with zooplankton assemblage structure along a gradient from high to low lake water N:P ratios. Specific objectives of the project include:

(1) Evaluate metrics based on the C, N, and P supply of the total dissolved plus seston fraction of lake water as indicators of the character of lake zooplankton assemblage.

(2) 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, 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.

(3) 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.

(4) 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 like 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.

(5) Conduct a thorough analysis of the sensitivity of zooplankton metrics using the spatially extensive data set in this study and from the existing lake data sets. 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.

(6) Develop a hierarchical, ecological-indicator analysis tool designed to aid resource managers in assessment, monitoring, and prediction of aquatic ecosystem integrity, sustainability, and associated ecosystem risks.

Progress Summary:

(Objectives 1-2) In our three field seasons, we conducted 138 lake visits, including 24 revisits, and sampled 158 tributaries in Adirondack Mountain and Saint Lawrence Valley Regions of New York, Vermont, and New Hampshire. We also have established preliminary evidence of direct connections between conditions in the lake watershed and lake water carbon, nitrogen, and phosphorus supply. 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 functional groups as a function of the source and decomposition history of the terrestrial organic matter. A measure of the carboxylic and phenolic group content of dissolved organic matter can therefore be used as an indicator of different sources of DOM in a lake system. 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, DON, and DOP) and dissolved carbon and nutrient supplies to lake water. In support of this watershed-lake connection, temporal average lake water chemistry is significantly correlated to temporal average tributary water chemistry indicators across the wide range of lake and watershed types in our sample.

We are developing a zooplankton body size indicator that helps to explain variation in Secchi depth visibility and should be a useful tool for lake management applications. 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. Hence, lakes with small-bodied grazers reflect a potential disruption in predatory game fish control on the forage base. The indicator also is remarkably consistent across most of our time series lakes in the 2001 survey.

(Objective 2) Experimental Evaluation. In 1998, we conducted experiments in 1,000 L cattle tanks to evaluate taxonomic and body size responses of zooplankton to additions of nitrogen, phosphorus, and fish. Nutrients had striking effects on taxonomic structure of the assemblages: phosphorus stimulated the abundance of cladocerans and rotifers, while nitrogen increased the abundance of copepod nauplii, cyclopoid copepodites, and rotifers. Fish reduced body sizes of crustacean zooplankton independent of taxonomic grouping. Populations of microzooplankton like 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 nitrogen-to-phosphorus ratio in the algal food.

(Objectives 2, 4) 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 that 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 nitrogen and phosphorus concentrations (i.e., decreasing N:P ratios). The analysis of field populations generally corroborated the results from the experiment?fish and the nitrogen-to-phosphorus 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 will continue this analytical approach with our more detailed data set, which includes the nutrient concentrations within major size fractions of lake water particles of algae and detritus.

(Objective 3) The landscape characterization task involves both field and GIS-analysis components. During fall 1999, 10 forested tributary riparian zone locations were visited for extensive 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 nitrogen 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 1070. 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.

(Objective 5) Sensitivity analysis of zooplankton population and richness indicators was undertaken using data from 365 lakes provided by the EPA's Environmental Monitoring and Assessment Program (EMAP) (Stemberger, et al., 2001). Sensitivity (ability of zooplankton indicators to detect lake-to-lake differences) increased when spatial scale of the study region was reduced to natural subregions like 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 difference. Therefore, this group would be especially useful for 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 lake water 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 by winter 2002, and we will begin analysis, interpretation, and manuscript preparation during the remaining funding period and beyond.

Journal Articles on this Report : 4 Displayed | Download in RIS Format

Publications Views

Other project views:	All 27 publications	12 publications in selected types	All 11 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	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
Journal Article	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
Journal Article	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
Journal Article	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, EMAP, modeling, GIS, northeast., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Water, Ecological Indicators, Air Deposition, Ecosystem Protection, Ecology, Watersheds, Environmental Chemistry, Ecosystem/Assessment/Indicators, exploratory research environmental biology, Geology, Ecological Effects - Environmental Exposure & Risk, Hydrology, Nutrients, Drinking Water, Water & Watershed, bioavailability, EMAP, integrative indicators, landscape characterization, ecological effects, carbon storage, lake ecosystem, algae, aquatic ecosystem, environmental monitoring, risk assessment, ecosystem indicators, phosphorus, atmospheric deposition, terrestrial, ecological exposure, other - risk assessment, land use, nitrogen, zooplankton, algal growth, chemical transport, aquatic ecosystems, multi-level indicators, nutrient transport, carbon cycling

Progress and Final Reports:

Original Abstract

1999 Progress Report

2000 Progress Report

2002 Progress Report

Final Report