Grantee Research Project Results
1999 Progress Report: Anthropogenic Pollutant Effects on Aquatic Ecosystems Impacts of Atmospheric Nitrogen Deposition on Phytoplankton Dynamics and Eutrophication
EPA Grant Number: R825243Title: Anthropogenic Pollutant Effects on Aquatic Ecosystems Impacts of Atmospheric Nitrogen Deposition on Phytoplankton Dynamics and Eutrophication
Investigators:
Institution: University of North Carolina at Chapel Hill , Rutgers University - New Brunswick , Mote Marine Laboratory
Current Institution: University of North Carolina at Chapel Hill , Rutgers University - New Brunswick
EPA Project Officer: Chung, Serena
Project Period: October 1, 1996 through September 30, 1999
Project Period Covered by this Report: October 1, 1998 through September 30, 1999
Project Amount: $382,789
RFA: Air Quality (1996) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Water Quality , Air
Objective:
The main objective of this research has been to evaluate ecosystem sensitivity to pollutant stress by examining phytoplankton community responses to atmospherically derived nitrogen compounds. The experimental approach involved the quantification of the impacts of N sources having DIN (NO3-, NH4+) and DON (urea) compositions representative of atmospheric new N inputs on phytoplankton primary productivity, photophysiology, and biodiversity in representative N-limited riverine and estuarine waters. The experimental design consists of five separate components: (1) biweekly sampling of chemical/biological conditions in the Neuse River; (2) collection of wet and dry atmospheric deposition at the University of North Carolina, Institute of Marine Sciences (UNC-IMS) on an event basis; (3) short-term bioassays to quantify phytoplankton responses to different AND sources; (4) mesocosm bioassays to examine longer-term changes in phytoplankton community structure following nutrient manipulations; and (5) photophysiological responses of phytoplankton when exposed to different AND sources under variable light conditions. Drs. Paerl and Pinckney directed components 1 through 4. Drs. Millie, Schofield, and Kirkpatrick conducted the photophysiological experiments (component 5). All experiments were performed at the UNC-IMS and the Neuse River. The IMS is located in Morehead City, NC, and is in close proximity to the Neuse River.Progress Summary:
The findings for Year 3 are summarized below.- Biweekly river sampling of physical, chemical, and biological parameters was conducted at 17 locations in Year 3 to characterize short (weeks) to long-term (annual) changes in environmental variables and their effects on natural phytoplankton communities. Although our sampling interval is biweekly, the North Carolina Department of the Environment and Natural Resources?Division of Water Quality (DENR-DWQ) and the Weyerhaeuser Company sample on alternating weeks. Data from this collaborative effort are transferred to IMS after collection via the Internet. Further details of our findings can be viewed at: www.marine.unc.edu/neuse/ modmon/homepage.html. Our overall results show a high degree of temporal and spatial variability in chemical, physical, and biological parameters measured in this estuary.
- We continued sampling in Year 3 for measurement of wet deposition (rain/snow) at sites in the Neuse watershed. The material has been characterized chemically for nitrate, ammonium, and Total Kjeldahl Nitrogen (TKN) on a weekly basis. Weekly collections have been completed according to the National Atmospheric Deposition Program (NADP) protocol at three locations in the Neuse River Basin, including a near-estuarine site at the U.S. Forest Service Croatan National Forest headquarters near New Bern, Lenoir Community College near Kinston, and an N.C. State Highway Patrol site near Goldsboro. We recently established a collection site near Cedar Island, NC. These stations are complemented by the NADP NC-41 location in Wake County. The DIN/DON concentrations in rainfall have been analyzed on a continuous basis for 2 years from the three established locations. Weekly depositional fluxes are highly variable, but are significantly higher in the spring and summer months. This pattern is not driven by precipitation patterns and may be driven by seasonal changes in N source emissions as well as the direction of dominant air-flow patterns and fronts passing over the research area. Typically, continental rainfall exhibits elevated DIN and DON concentrations while oceanic fronts contain the lowest concentrations (as well as total deposition rates) of both N forms (Paerl, et al., 1999).
- Short-term (2 days) nutrient addition bioassays were used to assess the impacts of DIN/DON components (nitrate, ammonium, and urea) on phytoplankton community structure (i.e., species composition and abundance) and function (i.e., productivity). Phytoplankton growth and productivity were N-limited during much of the study period, but the potential existed for co-limitation by phosphorus when ambient N concentrations were high and by light when incident irradiance was low. Nitrogen additions generally resulted in an increase in diatom biomass and a decrease in cyanobacteria biomass, but there were no consistent shifts in composition due to different forms of N, i.e, there were no consistent significant differences between effects of nitrate versus ammonium versus urea (Harrington, 1999).
- Mesocosm bioassays were conducted to examine longer-term (up to 6 days) changes in phytoplankton community structure following nutrient manipulations. We conducted two series of mesocosm experiments. Experiments in Series 1 were conducted in November 1997, February 1998, June 1998, and December 1998. Series 2 was conducted in March 1999, May 1999, August 1999, and November 1999. During each series, we addressed photophysiological and community structural responses to manipulations of both nutrients and light. All mesocosm experiments incorporated a two-factor (mixing, nutrient addition) experimental design using 66 liter mesocosm tanks. Natural phytoplankton communities were collected from a mesohaline station in the estuary. Results from Series 1 show that the relative effects of nutrient additions and water column mixing on phytoplankton community structure and function at this site varied between experiments. Overall, we found no significant effect of N form (nitrate versus ammonium) on phytoplankton community structure and function in any experiment. All nutrient additions significantly increased total community biomass (as measured by chlorophyll a) in the June 1998 experiment only, indicating that the community was N-limited at this time. The increase in total biomass was due to increases in the contributions of chlorophytes and diatoms to the community. In all experiments, significant differences were found between mixed and static incubations. In November 1997, the absolute and relative contribution of diatoms to total community biomass and rates of primary productivity were significantly higher in mixed incubations than in tanks left static. In the June 1998 experiment, static tanks had significantly higher absolute and relative contributions of cyanobacteria to overall community biomass than tanks that were mixed. In December, static incubations showed significantly higher absolute and relative abundances of cryptophytes than mixed tanks. We conclude that temporal variability in the effects of nutrient additions, temporal variations in water column structure, and the potential limiting or co-limiting effects of light are all important determinants of phytoplankton community structure and function and should be considered in estuarine nutrient management plans (Richardson, et al., 1999). The results of the Series 2 mesocosm experiments are still being analyzed. We examined responses of Neuse phytoplankton communities to various forms of N (nitrate, ammonium, and urea) under irradiance conditions that were more representative of those of a turbid estuary than experiments in Series 1.
- Photophysiological responses were examined during both series of mesocosm experiments. We determined the synergistic interactions of light and nutrients on the maximum quantum yield of stable charge separation at photosystem II (Fv/Fm) for natural phytoplankton communities collected from the Neuse River Estuary. A full suite of pigmentation, absorption, total carbon fixation, and Fv/Fm data were collected. Results of Series 1 show that both mixing and nutrient treatments were found to be statistically significant (p = .05), with the addition of nitrogen resulting in a 40 percent increase in Fv/Fm values within 24 hours. No significant differences were observed between additions of the different forms of nitrogen (i.e., nitrate versus ammonium). Additional preliminary data suggest that nutrient addition enhanced carbon fixation. This supports previous work suggesting that the Neuse River is nitrogen limited. Strong diurnal trends in Fv/Fm exhibited an inverse relationship to instantaneous light. Collected data suggest the large diurnal variability reflected physiological responses to bright light. Accordingly, chlorophyll-specific spectral absorption and pigmentation data indicated acclimation to high light conditions.
During the mesocosm study of May 1999, we deployed the self-contained
underwater photosynthesis apparatus (SUPA) in the mesocosm pond at the IMS to
collect high time resolution measures of photosynthetic responses to vertical
mixing. Samples from the experimental treatment, including additions of nitrate,
ammonium, and phosphorus (NAP), were compared to the control (no nutrient
additions). Dissolved oxygen, pH, temperature, and spectral irradiance in each
sample were recorded every minute during the day on May 5 and 7. During each of
those days, the sample chambers were lowered and raised through the pond (0.5 m)
on an approximate 1-hour cycle to simulate water column mixing. These time
series, when converted to rates of oxygen production and carbon uptake, allow
examination of the effects of eutrophication on the average rates of net
productivity during the day as well as on the short-period responses to mixing
through potential light stress. Analyses thus far indicate that the NAP-enriched
phytoplankton community achieves higher net productivity than the control
community at all levels in the water column. The NAP community also was able to
recover more quickly from light stress experienced when mixing placed it at the
surface of the water column. Completion of these analyses and synthesis with
results from the mesocosm experiments will help provide some physiological basis for the eutrophication effects detected.
Journal Articles on this Report : 9 Displayed | Download in RIS Format
| Other project views: | All 63 publications | 19 publications in selected types | All 16 journal articles |
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Bergmann T, Richardson TL, Paerl HW, Pinckney JL, Schofield O. Synergy of light and nutrients on the photosynthetic efficiency of phytoplankton populations from the Neuse River Estuary, North Carolina. Journal of Plankton Research 2002;24(9):923-933. |
R825243 (1999) R825243 (Final) |
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Borsuk ME, Stow CA, Luettich Jr. RA, Paerl HW, Pinckney JL. Modelling oxygen dynamics in an intermittently stratified estuary: estimation of process rates using field data. Estuarine, Coastal and Shelf Science 2001;52(1):33-49. |
R825243 (1999) R825243 (Final) R826938 (2001) R826938 (Final) R827957 (Final) |
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Paerl HW, Willey JD, Go M, Peierls BL, Pinckney JL, Fogel ML. Rainfall stimulation of primary production in western Atlantic Ocean waters: roles of different nitrogen sources and co-limiting nutrients. Marine Ecology Progress Series 1999;176:205-214. |
R825243 (1999) R825243 (Final) |
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Paerl HW, Whitall DR. Anthropogenically-derived atmospheric nitrogen deposition, marine eutrophication and harmful algal bloom expansion: is there a link? Ambio 1999;28(4):307-311. |
R825243 (1999) R825243 (Final) |
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Paerl HW, Pinckney, JL, Fear JM, Peierls BL. Fish kills and bottom-water hypoxia in the Neuse River and Estuary: reply to Burkholder et al. Marine Ecology Progress Series 1999;186:307-309. |
R825243 (1999) R825243 (Final) |
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Pinckney JL, Paerl HW, Harrington MB. Responses of the phytoplankton community growth rate to nutrient pulses in variable estuarine environments. Journal of Phycology 1999;35(6):1455-1463. |
R825243 (1999) R825243 (Final) |
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Pinckney JL, Paerl HW, Haugen E, Tester PA. Responses of phytoplankton and Pfiesteria-like dinoflagellate zoospores to nutrient enrichment in the Neuse River Estuary, North Carolina, USA. Marine Ecology Progress Series 2000;192:65-78. |
R825243 (1999) R825243 (Final) |
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Richardson TL, Pinckney JL, Paerl HW. Responses of estuarine phytoplankton communities to nitrogen form and mixing using microcosm bioassays. Estuaries and Coasts 2001;24(6):828-839. |
R825243 (1999) R825243 (Final) R826938 (Final) |
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Schofield O, Gryzmski J, Bissett WP, Kirkpatrick GJ, Millie DF, Moline M, Roesler CS. Optical monitoring and forecasting systems for harmful algal blooms: possibility or pipe dream? Journal of Phycology 1999;35(6):1477-1496. |
R825243 (1999) R825243 (Final) R827085 (2000) R827085 (2001) R827085 (Final) |
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Supplemental Keywords:
watersheds, precipitation, bioavailability, indicators, stress, ecology, modeling, Mid-Atlantic, North Carolina, agriculture., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Nutrients, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Atmospheric Sciences, Ecological Risk Assessment, Watersheds, Ecological Indicators, anthropogenic processes, atmospheric processes, nutrient transport, aquatic ecosystem, ecological exposure, anthropogenic stress, eutrophication, precipitation, biodiversity, nutrient sensitive ecosystems, atmospheric nitrogen deposition, ADN compounds, atmospheric nitrogen deposits, phytoplankton dynamics, nutrient stress, aquatic ecosystems, North Carolina (NC), rainfallRelevant Websites:
http://www.marine.unc.edu/
Progress 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.