Skip to main content
Log in

Decadal Changes in Water Quality and Net Productivity of a Shallow Danish Estuary Following Significant Nutrient Reductions

  • Published:
Estuaries and Coasts Aims and scope Submit manuscript

Abstract

We utilized an extensive data set (1977–2013) from a water quality monitoring program to investigate the recovery of a Danish estuary following large reductions in total phosphorus (TP) and total nitrogen (TN) loading. Monthly rates of net transport and biogeochemical transformation of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) were computed in two basins of the estuary using a box model approach, and oxygen-based rates of net ecosystem production (NEP) were determined. Since 1990, nutrient loading was reduced by 58 % for nitrogen and 80 % for phosphorus, causing significant decreases in DIN (60 %) and DIP (85 %) concentrations. Reductions in nutrient loadings and concentrations reduced annual chlorophyll levels by 50 % in the inner estuary and improved Secchi depth by approximately 1 m during the same period, particularly in the summer period. In the outer, deeper region of the estuary trends in water quality was less evident. Improvements in the inner estuary were strongly coupled to declines in DIN. Thresholds of DIN and DIP concentrations limiting phytoplankton growth indicated that both regions of the estuary were nitrogen limited. NEP rates indicated the development of more net autotrophic conditions over time that were likely associated with higher benthic primary production stimulated by improved light conditions. Box model computations revealed a modest reduction in summer net production of DIP over time, despite the persistence of elevated fluxes for several years after external loads were reduced. Since the mid-1990s, nutrient loading and transformation were stable while nutrient concentrations continued to decline and water quality improved in the inner estuary. The oligotrophication trajectory involved an initial fast transformation and modest retention of nutrients followed by a gradual decline in the rate of improvement towards a new stable condition.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11

Similar content being viewed by others

References

  • Beman, J.M., K.R. Arrigo, and P.A. Matson. 2005. Agricultural runoff fuels large phytoplankton blooms in vulnerable areas of the ocean. Nature 434: 211–214.

    Article  Google Scholar 

  • Borum, J., and K. Sand-Jensen. 1996. Is total primary production in shallow coastal marine waters stimulated by nitrogen loading? Oikos 76: 406–410.

    Article  Google Scholar 

  • Bricker, S.B., B. Longstaff, W. Dennison, A. Jones, K. Boicourt, C. Wicks, and J. Woerner. 2008. Effects of nutrient enrichment in the nation’s estuaries: A decade of change. Harmful Algae 8: 21–32.

    Article  CAS  Google Scholar 

  • Calbert, A., and M.R. Landry. 2004. Phytoplankton growth, microzooplankton grazing, and carbon cycling in marine systems. Limnology and Oceanography 49: 51–57.

    Article  Google Scholar 

  • Carstensen, J., D.J. Conley, J.H. Andersen, and G. Ærtebjerg. 2006. Coastal eutrophication and trend reversal: A Danish case study. Limnology and Oceanography 51: 398–408.

    Article  Google Scholar 

  • Carstensen, J., M. Sánchez-Camacho, C.M. Duarte, D. Krause-Jensen, and N. Marbà. 2011. Connecting the dots: Responses of coastal ecosystems to changing nutrient concentrations. Environmental Science and Technology 45: 9122–9132.

    Article  CAS  Google Scholar 

  • Cloern, J.E. 2001. Our evolving conceptual model of the coastal eutrophication problem. Marine Ecology Progress Series 210: 223–253.

    Article  CAS  Google Scholar 

  • Clarke, A., S. Juggins, and D. Conley. 2003. A 150-year reconstruction of the history of coastal eutrophication in Roskilde Fjord, Denmark. Marine Pollution Bulletin 46(12): 1615–1618.

    Article  CAS  Google Scholar 

  • Conley, D.J., H. Kaas, F. Møhlenberg, B. Rasmussen, and J. Windolf. 2000. Characteristics of Danish estuaries. Estuaries 23: 820–837.

    Article  CAS  Google Scholar 

  • Cowan, J.L.W., and W.R. Boynton. 1996. Sediment-water oxygen and nutrient exchanges along the longitudinal axis of Chesapeake Bay: Seasonal patterns, controlling factors and ecological significance. Estuaries 19: 562–580.

    Article  CAS  Google Scholar 

  • Crossland, C.J., H.H. Kremer, H.J. Lindeboom, J.I. Marshall-Crossland, and M.D.L. Tissier. 2005. Coastal fluxes in the anthropocene—The land-ocean interactions in the coastal zone project of the international geosphere-biosphere programme. Berlin: Springer.

    Google Scholar 

  • Dahl, K., Ærtebjerg, G., Jensen, J.N., Nielsen, T.G., Lisbjerg, D., Krause-Jensen, D., and Christensen, P.B. 1995. Marine areas—Inlets, coasts and open sea. Faglig rapport fra DMU, nr 142 (In Danish).

  • Dalsgaard, T. 2003. Benthic primary production and nutrient cycling in sediments with benthic microalgae and transient accumulation of macroalgae. Limnology and Oceanography 48: 2138–2150.

    Article  CAS  Google Scholar 

  • Danish Standards Association. 1975. Determination of nitrogen content after oxidation by peroxodisulphate. Copenhagen: DS 221.

    Google Scholar 

  • Danish Standards Association. 1985. Water analysis—Total phosphor–photometric method. Copenhagen: DS292.

    Google Scholar 

  • Danish Standards Association. 1986. Water analysis – Chlorophyll a – photometric method. Copenhagen: DS2201.

  • Dettmann, E.H. 2001. Effect of water residence time on annual export and denitrification of nitrogen in estuaries: A model analysis. Estuaries 24: 481–490.

    Article  CAS  Google Scholar 

  • Downing, J.A. 1997. Marine nitrogen: Phosphorus stoichiometry and the global N:P cycle. Biogeochemistry 37: 237–252.

    Article  Google Scholar 

  • Duarte, C.M., A. Borja, J. Carstensen, M. Elliott, D. Krause-Jensen, and N. Marba. 2015. Paradigms in the recovery of estuarine and coastal ecosystems. Estuaries and Coasts 38: 1202–1212.

    Article  Google Scholar 

  • Duarte, C.M., D.J. Conley, J. Carstensen, and M. Sanchez-Camacho. 2009. Return to Neverland: Shifting baselines affect eutrophication restoration targets. Estuaries and Coasts 32: 29–36.

    Article  CAS  Google Scholar 

  • Eyre, B.D., and L.J. McKee. 2002. Carbon, nitrogen, and phosphorus budgets for a shallow subtropical coastal embayment (Moreton Bay, Australia). Limnology and Oceanography 47: 1043–1055.

    Article  CAS  Google Scholar 

  • Ferguson, A.J.P., and B.D. Eyre. 2010. Carbon and nitrogen cycling in a shallow productive sub-tropical coastal embayment (Western Moreton Bay, Australia): The importance of pelagic–benthic coupling. Ecosystems 13: 1127–1144.

    Article  CAS  Google Scholar 

  • Fourqurean, F.W., G.A. Kendrick, L.S. Collins, R.M. Chambers, and M.A. Vanderklift. 2012. Carbon, nitrogen and phosphorus storage in subtropical seagrass meadows: examples from Florida Bay and Shark Bay. Marine and Freshwater Research 63: 967–983.

  • Geertz-Hansen, O., K. Sand-Jensen, D.F. Hansen, and A. Christiansen. 1993. Growth and grazing control of abundance of the marine macroalga, Ulva lactuca L. in a eutrophic Danish estuary. Aquatic Botany 46: 101–109.

    Article  Google Scholar 

  • Greening, H., and A. Janicki. 2006. Toward reversal of eutrophic conditions in a subtropical estuary: Water quality and seagrass response to nitrogen loading reductions in Tampa Bay, Florida, USA. Environmental Management 38: 163–178.

    Article  Google Scholar 

  • Hagy, J.D., L.P. Sanford, and W.R. Boynton. 2000. Estimation of net physical transport and hydraulic residence times for a coastal plain estuary using box models. Estuaries 23: 328–340.

    Article  Google Scholar 

  • Hagy, J.D., W.R. Boynton, and D.A. Jasinski. 2005. Modelling phytoplankton deposition to Chesapeake Bay sediments during winter-spring: Interannual variability in relation to river flow. Estuarine, Coastal and Shelf Science 62: 25–40.

    Article  CAS  Google Scholar 

  • Heisler, J., P.M. Glibert, J.M. Burkholder, D.M. Anderson, W. Cochlan, W.C. Dennison, Q. Dortch, C.J. Gobler, C.A. Heil, E. Humphries, A. Lewitus, R. Magnien, H.G. Marshall, K. Sellner, D.A. Stockwell, D.K. Stoecker, and M. Suddleson. 2008. Eutrophication and harmful algal blooms: A scientific consensus. Harmful Algae 8: 3–13.

    Article  CAS  Google Scholar 

  • HELCOM. 2010. Ecosystem health of the Baltic sea, HELCOM initial holistic assessment. Baltic sea environmental. Proceedings. 122:63 pp.

  • Jähne, B., O. Münnich, R. Bösinger, A. Dutzi, W. Huber, and P. Libner. 1987. On the parameters influencing air-water gas exchange. Journal of Geophysical Research 92: 1937–1949.

    Article  Google Scholar 

  • Josefson, A., and B. Rasmussen. 2000. Nutrient retention by benthic macrofaunal biomass of Danish estuaries: Importance of nutrient load and residence time. Estuarine, Coastal and Shelf Science 50: 205–216.

    Article  CAS  Google Scholar 

  • Kaas, H., and S. Markager. 1998. Technical guidelines for marine monitoring. Denmark: National Environmental Research Institute.

    Google Scholar 

  • Kamp-Nielsen, L. 1992. Benithic-pelagic coupling of nutrient metabolism along an estuarine eutrophication gradient. Hydrobiologia 235: 457–470.

    Article  Google Scholar 

  • Kemp, W.M., J.M. Testa, D.J. Conley, D. Gilbert, and J.D. Hagy. 2009. Temporal responses of coastal hypoxia to nutrient loading and physical controls. Biogeosciences 6: 2985–3008.

    Article  CAS  Google Scholar 

  • Kemp, W.M., and W.R. Boynton. 1992. Benthic–pelagic interactions: Nutrient and oxygen dynamics. In Oxygen dynamics in Chesapeake Bay: A synthesis of research, eds. D. Smith, M. Leffler, and G. Mackiernan, 149–221. College Park: Maryland Sea Grant Publications.

    Google Scholar 

  • Kemp, W.M., E.M. Smith, M. Marvin-Dipasquale, and W.R. Boynton. 1997. Organic carbon balance and net ecosystem metabolism in Chesapeake Bay. Marine Ecology Progress Series 150: 229–248.

    Article  CAS  Google Scholar 

  • Kemp, W.M., P. Sampou, J. Caffrey, M. Mayer, K. Henriksen, and W.R. Boynton. 1990. Ammonium recycling versus denitrification in Chesapeake Bay sediments. Limnology and Oceanography 35: 1545–1563.

    Article  CAS  Google Scholar 

  • Klausmeier, C.A., E. Litchman, T. Daufresne, and S.A. Levin. 2004. Optimal nitrogen-to-phosphorus stoichiometry of phytoplankton. Nature 429: 171–174.

    Article  CAS  Google Scholar 

  • Krause-Jensen, D., S. Markager, and T. Dalsgaard. 2012. Benthic and pelagic primary production in different nutrient regimes. Estuaries and Coasts 35: 527–545.

    Article  CAS  Google Scholar 

  • Kronvang, B., E. Jeppesen, D.J. Conley, M. Søndergaard, S.E. Larsen, N.B. Ovesen, and J. Carstensen. 2005. Nutrient pressures and ecological responses to nutrient loading reductions in Danish streams, lakes and coastal waters. Journal of Hydrology 304: 274–288.

    Article  CAS  Google Scholar 

  • Kronvang, B., H.E. Andersen, C. Borgesen, T. Dalgaard, S.E. Larsen, J. Bøgestrand, and G. Blicher-Mathiasen. 2008. Effects of policy measures implemented in Denmark on nitrogen pollution of the aquatic environment. Environmental Science & Policy 11: 144–152.

  • Larsen, J., C. Mohn, and K. Timmerman. 2013. A novel model approach to bridge the gap between box models and classic 3D models in estuarine systems. Ecological Modeling 266: 19–29.

  • Mayer, M.S., L. Shaffner, and W.M. Kemp. 1995. Nitrification potentials of benthic macrofaunal tubes and burrow walls: Effects of sediment NH4 + and animal irrigation behavior. Marine Ecology Progress Series 121: 157–169.

    Article  CAS  Google Scholar 

  • McGlathery, K.J., K. Sundbäck, and I.C. Anderson. 2007. Eutrophication in shallow coastal bays and lagoons: The role of plants in the coastal filter. Marine Ecology Progress Series 348: 1–18.

    Article  CAS  Google Scholar 

  • McGlathery, K.J., L.K. Reynolds, L.W. Cole, R.J. Orth, S.R. Marion, and A. Schwarzschild. 2012. Recovery trajectories during state change from bare sediment to eelgrass dominance. Marine Ecology Progress Series 448: 209–221.

    Article  Google Scholar 

  • Mørk, E.T., L. Sørensen, B. Jensen, and M.K. Sejr. 2014. Air-sea CO2 gas transfer velocity in a shallow estuary. Boundary-Layer Meteorology 151: 119–138.

    Article  Google Scholar 

  • Nixon, S.W. 1995. Coastal marine eutrophication—A definition, social causes, and future concerns. Ophelia 41: 199–219.

    Article  Google Scholar 

  • Nixon, S.W., S. Granger, B.A. Buckley, M. Lamont, and B. Rowell. 2004. A one hundred and seventeen year coastal water temperature record from Woods Hole, Massachusetts. Estuaries and Coasts 27: 397–404.

    Article  Google Scholar 

  • Nixon, S.W., R.W. Fulweiler, B.A. Buckley, S.L. Granger, B.L. Nowicki, and K.M. Henry. 2009. The impact of changing climate on phenology, productivity, and benthic-pelagic coupling in Narragansett Bay. Estuarine, Coastal and Shelf Science 82: 1–18.

    Article  CAS  Google Scholar 

  • Novotny, V., and H. Olem. 1994. Water quality: Prevention, identification and management of diffuse pollution, 1092 pp. New York: Wiley.

  • Officer, C.B. 1980. Box models revisited. In Estuarine and wetland processes, eds. P. Hamilton, and R.B. Macdonald, 65–114. New York: Plenum Press.

    Chapter  Google Scholar 

  • Paerl, H.W. 1988. Nuisance phytoplankton blooms in coastal, estuarine, and inland waters. Limnology and Oceanography 33: 823–847.

    CAS  Google Scholar 

  • Pedersen, T.M., K. Sand-Jensen, S. Markager, and S.L. Nielsen. 2014. Optical changes in a eutrophic estuary during reduced nutrient loadings. Estuaries and Coasts 37: 880–892.

    Article  CAS  Google Scholar 

  • Preston, B.L. 2004. Observed winter warming of the Chesapeake Bay estuary (1949-2002): Implications for ecosystem management. Environmental Management 34: 125–139.

    Article  Google Scholar 

  • Pritchard, D.W. 1969. Dispersion and flushing of pollutants in estuaries. Journal of Hydraulics Division, ASCE 95: 115–124.

    Google Scholar 

  • Riemann, B., J. Carstensen, K. Dahl, H. Fossing, J.W. Hansen, H.H. Jakobsen, A. Josefson, D. Krause-Jensen, S. Markager, P.A. Stæhr, K. Timmermann, and J. Windolf. 2016. Recovery of Danish coastal ecosystems after reductions in nutrient loading: trends and time lags. Estuaries and Coasts 39: 82–97.

    Article  CAS  Google Scholar 

  • Riisgård, H.U., P.B. Christensen, N.J. Olesen, et al. 1995. Biological structure in a shallow cove (Kertinge Nor, Denmark) control by benthic nutrient fluxes and suspension-feeding ascidians and jellyfish. Ophelia 41: 329–344.

    Article  Google Scholar 

  • Ryther, J.H., and W.M. Dunstan. 1971. Nitrogen, phosphorus, and eutrophication in coastal marine environment. Science 171: 1008–1013.

    Article  CAS  Google Scholar 

  • Sand-Jensen, K., and J. Borum. 1991. Interactions among phytoplankton, periphyton, and macrophytes in temperate freshwaters and estuaries. Aquatic Botany 41: 137–175.

    Article  Google Scholar 

  • Skamarock, W.C., Klemp, J.B., Dudhia, J., Gill, D.O., Barker, D.M., Wang, W., and Powers, J.G. 2005. A description of the advanced research WRF version 2. NCAR Tech Notes-468+STR.

  • Smith, S.V., J.T. Hollibaugh, S.J. Dollar, and S. Vink. 1991. Tomales Bay metabolism—C-N-P stoichiometry and ecosystem heterotrophy at the land sea interface. Estuarine, Coastal and Shelf Science 33: 223–257.

    Article  CAS  Google Scholar 

  • Smith, S.V., D.P. Swaney, L. Talaue-McManus, J.D. Bartley, P.T. Sandhei, C.J. McLaughlin, V.C. Dupra, C.J. Crossland, R.W. Buddemeier, B.A. Maxwell, and F. Wulff. 2003. Humans, hydrology, and the distribution of inorganic nutrient loading to the ocean. Bioscience 53: 235–245.

    Article  Google Scholar 

  • Staehr, P.A., and J. Borum. 2011. Seasonal acclimation in metabolism reduces light requirements of eelgrass (Zostera marina). Journal of Experimental Marine Biology and Ecology 407: 139–146.

    Article  Google Scholar 

  • Staehr, P.A., J.M. Testa, W.M. Kemp, J.J. Cole, K. Sand-Jensen, and S.V. Smith. 2012. The metabolism of aquatic ecosystems: History, applications, and future challenges. Aquatic Sciences 74: 15–29.

    Article  Google Scholar 

  • Strickland, J.D.H., and T.R. Parsons. 1972. A practical handbook of seawater analysis. Bulletin Fisheries Research Board of Canada 167: 1–310.

    Google Scholar 

  • Stumm, W., and J.J. Morgan. 1996. Aquatic chemistry, 1022 p. New York: Wiley. P.

  • Taylor, D.I., C.A. Oviatt, and D.G. Borkman. 2011. Non-linear responses of a coastal aquatic ecosystem to large decreases in nutrient and organic loadings. Estuaries and Coasts 34: 745–757.

    Article  CAS  Google Scholar 

  • Testa, J.M., and W.M. Kemp. 2008. Regional, seasonal, and inter-annual variability of biogeochemical processes and physical transport in a partially stratified estuary: A box-modeling analysis. Marine Ecology Progress Series 356: 63–79.

    Article  CAS  Google Scholar 

  • Testa, J., W.M. Kemp, W.R. Boynton, and J.D. Hagy. 2008. Long-term changes in water quality and productivity in the Patuxent River estuary: 1985 to 2003. Estuaries and Coasts 31: 1021–1037.

    Article  CAS  Google Scholar 

  • Testa, J.M., D.C. Brady, D.M. Di Toro, W.R. Boynton, and W.M. Kemp. 2013. Sediment flux modeling: nitrogen, phosphorus and silica cycles. Estuarine, Coastal and Shelf Science 131: 245–263.

    Article  CAS  Google Scholar 

  • Trolle, D., P.A. Staehr, T.A. Davidson, R. Bjerring, T.L. Lauridsen, M. Søndergaard, and E. Jeppesen. 2012. Seasonal dynamics of CO2 flux across the surface of shallow temperate lakes. Ecosystems 15: 336–347.

    Article  CAS  Google Scholar 

  • Tucker, J., A.E. Giblin, C.S. Hopkinson, S.W. Kelsey, and B.L. Howes. 2014. Response of benthic metabolism and nutrient cycling to reductions in wastewater loading to Boston Harbor, USA. Estuarine, Coastal and Shelf Science 151: 54–68.

    Article  CAS  Google Scholar 

  • van der Heide, T., E.H. van Nes, M.M. van Katwijk, H. Olff, and A.J.P. Smolders. 2011. Positive feedbacks in seagrass ecosystems—Evidence from large-scale empirical data. PloS One 6: e16504. doi:10.1371/journal.pone.0016504.

    Article  Google Scholar 

  • Weiss, R.F. 1970. Solubility of nitrogen, oxygen and argon in water and seawater. Deep-Sea Research 17: 721–735.

    CAS  Google Scholar 

  • Wetzel, R.G. 1990. Land-water interfaces: Metabolic and limnological regulators. Edgardo Baldi memorial lecture. Verhandlungen—Internationale Vereinigung Limnologie 24: 6–24.

    Google Scholar 

  • Yoon, W.B., and R. Benner. 1992. Denitrification and oxygen consumption in sediments of two South Texas estuaries. Marine Ecology Progress Series 90: 157–167.

    Article  CAS  Google Scholar 

  • Yvon-Durocher, G., A. Cescatti, P. del Giorgio, J.M. Gasol, J.M. Montoya, J. Pumpanen, P.A. Staehr, M. Trimmer, G. Woodward, and A.P. Allen. 2012. Renconciling differences in the temperature-dependence of ecosystem respiration across time scales and ecosystem types. Nature 487: 472–476.

    Article  CAS  Google Scholar 

Download references

Acknowledgments

This work was supported by the COCOA project funded under the BONUS program “Viable ecosystems” and partially from the United States National Science Foundation grants DEB1353766 and CBET1360415. This is contribution # 5197 from the University of Maryland Center for Environmental Science. We would like to thank Jesper Christensen and Camilla Greels from Institute of Enviromental Sciences Aarhus University, for assisting with the wind modeling, and Janus Larsen, Department of Bioscience, Aarhus University, for setting up a hydrodynamic model for comparison with box model computations of salt fluxes.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Peter A. Staehr.

Additional information

Communicated by Craig Tobias

Electronic supplementary material

ESM 1

(DOCX 235 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Staehr, P.A., Testa, J. & Carstensen, J. Decadal Changes in Water Quality and Net Productivity of a Shallow Danish Estuary Following Significant Nutrient Reductions. Estuaries and Coasts 40, 63–79 (2017). https://doi.org/10.1007/s12237-016-0117-x

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s12237-016-0117-x

Keywords

Navigation