Abstract
Human activities on coastal watersheds provide the major sources of nutrients entering shallow coastal ecosystems. Nutrient loadings from watersheds are the most widespread factor that alters structure and function of receiving aquatic ecosystems. To investigate this coupling of land to marine systems, we are studying a series of subwatersheds of Waquoit Bay that differ in degree of urbanization and hence are exposed to widely different nutrient loading rates. The subwatersheds differ in the number of septic tanks and the relative acreage of forests. In the area of our study, groundwater is the major mechanism that transports nutrients to coastal waters. Although there is some attenuation of nutrient concentrations within the aquifer or at the sediment-water interface, in urbanized areas there are significant increases in the nutrient content of groundwater arriving at the shore’s edge. The groundwater seeps or flows through the sediment-water boundary, and sufficient groundwater-borne nutrients (nitrogen in particular) traverse the sediment-water boundary to cause significant changes in the aquatic ecosystem. These loading-dependent alterations include increased nutrients in water, greater primary production by phytoplankton, and increased macroaglal biomass and growth (mediated by a suite of physiological responses to abundance of nutrients). The increased macroalgal biomass dominates the bay ecosystem through second- or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events. The increases in seaweeds have decreased the areas covered by eelgrass habitats. The change in habitat type, plus the increased frequency of anoxic events, change the composition of the benthic fauna. The data make evident the importance of bottom-up control in shallow coastal food webs. The coupling of land to sea by groundwater-borne nutrient transport is mediated by a complex series of steps; the cascade of processes make it unlikely to find a one-to-one relation between land use and conditions in the aquatic ecosystem. Study of the process and synthesis by appropriate models may provide a way to deal with the complexities of the coupling.
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Literature Cited
Caezan, M. C., E. M. Thurman, andR. L. Smith. 1987. The role of cation exchange in the transport of ammonium and nitrate in a sewage-contaminated aquifer, p. B53-B58.In Toxic Waste and Groundwater Contamination Program, 3rd Technical Meeting. United States Geological Survey, Boston, Massachusetts.
Costa, J. E. 1988. Distribution, production, and historical changes in abundance of eelgrass (Zostera marina) in southeastern Massachusetts. Ph.D. Thesis. Boston University, 352 p.
Costa, J. F., B. L. Howes, A. E. Giblin, and I. Valiela. In press. Monitoring nitrogen and indicators of nitrogen to support management action in Buzzards Bay.In D. H. McKenzie, D. E. Hylact, and V. J. McDonald (eds.), Ecological Indicators. Volume I. Elsevier Press, London.
Culliton, T. J., C. M. Blackwell, D. G. Remer, T. R. Goodspeed, andM. A. Warren. 1989. Selected characteristics in coastal states. 1980–2000. NOAA’s Coastal Trends Series: Report I. National Oceanic and Atmospheric Administration, Strategic Assessment Branch. Rockville, Maryland. 15 p.
Curley, J. R., R. P. Lawton, J. M. Hicket, andJ. D. Fiske. 1971. A study of the marine resources of the Waquoit Bay-Eel Pond Estuary. Department of Marine Fisheries, Sandwich Massachusetts. 40 p.
Dennison, W. C. andR. S. Alberte. 1985. Role of daily light period in the depth distribution of photosynthetic response ofZostera marina (eelgrass).Marine Ecology Progress Series 25: 51–61.
Freeze, R. A. andJ. A. Cherry. 1979. Groundwater. Prentice-Hall. Englewood Cliffs, New Jersey. 604 p.
Frimpter, M. H., J. J. Donohoe, andM. V. Rapacz. 1988. A mass balance nitrate model for predicting the effects of land use on groundwater quality in municipal wellhead protection areas. Cape Cod Aquifer Management Project. United States Geological Survey, Marlboro, Massachusetts. 54 p.
Groffman, P. M. andJ. M. Tiedje. 1989. Denitrification in North Temperate forest soils: Spatial and temporal patterns and the landscape level and seasonal sinks.Soil Biology Biochemistry 21:613–620.
Kelly, J. R. andS. A. Levin, 1986. A comparison of aquatic and terrestrial nutrient cycling and production processes in natural ecosystems, with reference to ecological concepts of relevance to some waste disposal issues, p. 165–203.In G. Kullenberg (ed.), The Role of the Oceans as a Waste Disposal Option. NATO Advanced Research Workshop Series D. Reidel Publishing Company, Dordrecht.
Kipp, K. L. 1987. Preliminary one-dimensional simulation of ammonium and nitrate in the Cape Cod sewage plume, p. B43-B44.In Toxic Waste and Groundwater Contamination Program, 3rd Technical Meeting. United States Geological Survey, Boston, Massachusetts.
Nixon, S. W., C. A. Oviatt, J. Frithsen, andB. Sullivan. 1986. Nutrients and the productivity of estuarine and coastal marine ecosystems.Journal of the Limnological Society of South Africa 12:43–71.
Nixon, S. W. 1988. Physical energy inputs and the comparative ecology of lake and marine ecosystems.Limnology and Oceanography 33(pt. 2):1005–1025.
Persky, J. H. 1986. The relation of ground-water quality to housing density, Cape Cod, Massachusetts. U.S.G.S. Water-Resources Investigations Report 86-4093, Boston, Massachusetts. 29 p.
Pickett, S. T. A. 1988. Space for time substitution as an alternative to long-term studies, p. 110–135.In G. E. Likens (ed.), Long-Term Studies in Ecology. Springer-Verlag, New York.
Seitzinger, S. P. 1988. Denitrification in freshwater and coastal marine ecosystems: Ecological and geochemical significance.Limnology and Oceanography 30:702–724.
Seitzinger, S. P. andS. W. Nixon. 1985. Eutrophication and rate of denitrification and N2O production in coastal marine sediments.Limnology and Oceanography 30:1332–1339.
Smith, R. L. andJ. H. Duff. 1988. Denitrification in a sand and gravel aquifer.Applied Environmental Microbiology 54:1071–1078.
Valiela, I. 1991. Ecology of water columns, p. 29–56.In R. S. K. Barnes and K. H. Mann (eds.), Fundamentals of Aquatic Ecology. Blackwell, Oxford.
Valiela, I. andJ. Costa. 1988. Eutrophication of Buttermilk Bay, a Cape Cod coastal embayment: Concentrations of nutrients and watershed nutrient budgets.Environmental Management 12:539–551.
Valiela, I., J. Teal, S. Volkmann, D. Shafer, andE. Carpenter. 1978. Nutrient and particulate fluxes in a salt marsh ecosystem: Tidal exchanges and inputs by precipitation and groundwater.Limnology and Oceanography 23:798–812.
Valiela, I., J. Costa, K. Foreman, J. M. Teal, B. Howes, andD. Aubrey. 1990. Transport of groundwater-borne nutrients from watersheds and their effects on coastal waters.Biogeochemistry 10:177–197.
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We dedicate this paper to our friend and colleague, the late William E. Odum of the University of Virginia.
Work reported here is part of the Waquoit Bay Land Margin Ecosystems Research project, funded by the National Science Foundation, the United States Environmental Protection Agency, and the National Oceanic and Atmospheric Administration. The work was carried out in the Waquoit Bay National Estuarine Research Reserve, and we thank its executive director, Christine Gault, for her cooperation.
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Valiela, I., Foreman, K., LaMontagne, M. et al. Couplings of watersheds and coastal waters: Sources and consequences of nutrient enrichment in Waquoit Bay, Massachusetts. Estuaries 15, 443–457 (1992). https://doi.org/10.2307/1352389
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DOI: https://doi.org/10.2307/1352389