Reconciling observed and modelled phytoplankton dynamics in a major lowland UK river, the Thames

This study aims to elucidate the key mechanisms controlling phytoplankton growth and decay within the Thames basin through the application of a modified version of an established river-algal model and comparison with observed stream water chlorophyll-a concentrations. The River Thames showed a distinct simulated phytoplankton seasonality and behaviour having high spring, moderate summer and low autumn chlorophyll-a concentrations. Three main sections were identified along the River Thames with different phytoplankton abundance and seasonality: (i) low chlorophyll-a concentrations from source to Newbridge; (ii) steep concentration increase between Newbridge and Sutton; and (iii) high concentrations with a moderate increase in concentration from Sutton to the end of the study area (Maidenhead). However, local hydrologic (e.g. locks) and other conditions (e.g. radiation, water depth, grazer dynamics, etc.) affected the simulated growth and losses. The model achieved good simulation results during both calibration and testing through a range of hydrological and nutrient conditions. Simulated phytoplankton growth was controlled predominantly by residence time, but during medium–low flow periods available light, water temperature and herbivorous grazing defined algal community development. These results challenge the perceived importance of in-stream nutrient concentrations as the perceived primary control on phytoplankton growth and death.

[1]  Louis Legendre,et al.  Hierarchical control of phytoplankton succession by physical factors , 1984 .

[2]  S. Jørgensen.  Handbook of Ecological Parameters and Ecotoxicology , 1991 .

[3]  Erik Jeppesen,et al.  Trophic structure, species richness and biodiversity in Danish lakes: changes along a phosphorus gradient , 2000 .

[4]  C D Collins,et al.  Coefficients for Use in the U. S. Army Corps of Engineers Reservoir Model, CE-QUAL-R1. , 1983 .

[5]  S. Bartell,et al.  An ecosystem model for assessing ecological risks in Québec rivers, lakes, and reservoirs , 1999 .

[6]  N. Broughton,et al.  An investigation into the growth of 0‐group roach, (Rutilus rutilus L.) with special reference to temperature , 1978 .

[7]  T. J. Lack,et al.  Primary production and respiration of the phytoplankton of the Rivers Thames and Kennet at Reading , 1971 .

[8]  Tim Sellers,et al.  Phytoplankton production in a large, regulated river: A modeling and mass balance assessment , 2003 .

[9]  C. Neal,et al.  Sewage effluent clean-up reduces phosphorus but not phytoplankton in lowland chalk stream (River Kennet, UK) impacted by water mixing from adjacent canal. , 2010, The Science of the total environment.

[10]  A. Mackey,et al.  The prediction of water temperatures in chalk streams from air temperatures , 1991, Hydrobiologia.

[11]  F. Schöll,et al.  Modelling the Chlorophyll a Content of the River Rhine - Interrelation between Riverine Algal Production and Population Biomass of Grazers, Rotifers and the Zebra Mussel, Dreissena polymorpha , 2002 .

[12]  M. Bowes,et al.  How green is my river? A new paradigm of eutrophication in rivers. , 2006, The Science of the total environment.

[13]  A. Howard,et al.  Modelling the growth and movement of cyanobacteria in river systems. , 2006, The Science of the total environment.

[14]  G. Minshall,et al.  The River Continuum Concept , 1980 .

[15]  Jean-Marc Thebault,et al.  A model of phytoplankton development in the Lot River (France).: Simulations of scenarios , 1999 .

[16]  David Atkinson,et al.  Predicting marine phytoplankton maximum growth rates from temperature: Improving on the Eppley curve using quantile regression , 2008 .

[17]  C. Neal,et al.  Chlorophyll-a in the rivers of eastern England. , 2006, The Science of the total environment.

[18]  B. Whitton,et al.  The strategic significance of wastewater sources to pollutant phosphorus levels in English rivers and to environmental management for rural, agricultural and urban catchments. , 2010, The Science of the total environment.

[19]  A. Wade,et al.  Modelling fixed plant and algal dynamics in rivers: an application to the River Frome , 2010 .

[20]  A. E. Irish,et al.  The ecological basis for simulating phytoplankton responses to environmental change (PROTECH) , 2001 .

[21]  A. Pinder,et al.  Modelling phytoplankton dynamics in the River Swale, an upland river in NE England , 1998 .

[22]  A. Cloot,et al.  Modelling algal blooms in the middle vaal river: A site specific approach , 1997 .

[23]  D. Lawrence,et al.  Fine sediment delivery and transfer in lowland catchments: modelling suspended sediment concentrations in response to hydrological forcing , 2007 .

[24]  Richard A. Park,et al.  AQUATOX: Modeling environmental fate and ecological effects in aquatic ecosystems ☆ , 2008 .

[25]  R. S. Booth,et al.  A Production Model for Myriophyllum spicatum L. , 1975 .

[26]  Roger I. Jones,et al.  Factors Controlling Phytoplankton Production and Succession in a Highly Eutrophic Lake (Kinnego Bay, Lough Neagh): II. Phytoplankton Production and Its Chief Determinants , 1977 .

[27]  J. Talling.  PHOTOSYNTHETIC CHARACTERISTICS OF SOME FRESHWATER PLANKTON DIATOMS IN RELATION TO UNDERWATER RADIATION , 1957 .

[28]  G. K. Morse,et al.  The relation between phosphorus and eutrophication in the Thames catchment, UK , 1999 .

[29]  E. J. Wilson,et al.  A semi-distributed ntegrated itrogen model for multiple source assessment in tchments (INCA): Part I — model structure and process equations , 1998 .

[30]  David P. Hamilton,et al.  Modelling the impact of zooplankton grazing on phytoplankton biomass during a dinoflagellate bloom in the Swan River Estuary, Western Australia , 2001 .

[31]  Colin S. Reynolds,et al.  The ecology of freshwater phytoplankton , 1984 .

[32]  Heather M. Bragg,et al.  Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon , 2007 .

[33]  R. Horner,et al.  Stream periphyton response to grazing and changes in phosphorus concentration , 1995, Hydrobiologia.

[34]  S J Ormerod,et al.  Evidence needed to manage freshwater ecosystems in a changing climate: turning adaptation principles into practice. , 2010, The Science of the total environment.

[35]  R. O. Megard.  PHYTOPLANKTON, PHOTOSYNTHESIS, AND PHOSPHORUS IN LAKE MINNETONKA, MINNESOTA1 , 1972 .

[36]  F. Périé,et al.  Calibration, validation and sensitivity analysis of an ecosystem model applied to artificial streams. , 2008, Water research.

[37]  T. J. Lack,et al.  Quantitative studies on the phytoplankton of the Rivers Thames and Kennet at Reading , 1971 .

[38]  J. Coles,et al.  Effect of temperature on photosynthesis‐light response and growth of four phytoplankton species isolated from a tidal freshwater river , 2000 .

[39]  Tsuyoshi Kobayashi,et al.  Grazing by a River Zooplankton Community: Importance of Microzooplankton , 1996 .

[40]  C. Reynolds,et al.  The production, biomass and structure of phytoplankton in large rivers , 1996 .

[41]  S. Sabater,et al.  Longitudinal development of chlorophyll and phytoplankton assemblages in a regulated large river (the Ebro River). , 2008, The Science of the total environment.

[42]  N. Lair,et al.  Spatio-temporal Investigations on the Planktonic Organisms of the Middle Loire (France), During the Low Water Period: Biodiversity and Community Dynamics , 2005, Hydrobiologia.

[43]  Richard J. Williams,et al.  Declines in phosphorus concentration in the upper River Thames (UK): links to sewage effluent cleanup and extended end-member mixing analysis. , 2010, The Science of the total environment.

[44]  G. Hornberger,et al.  Modelling algal behaviour in the river thames , 1984 .

[45]  Jean-Pierre Descy,et al.  USE OF PHYTOPLANKTON IN LARGE RIVER MANAGEMENT , 1998 .

[46]  C. Neal,et al.  Measuring in-stream productivity: the potential of continuous chlorophyll and dissolved oxygen monitoring for assessing the ecological status of surface waters. , 2003, Water science and technology : a journal of the International Association on Water Pollution Research.

[47]  J. Descy,et al.  Grazing by large river zooplankton: a key to summer potamoplankton decline? The case of the Meuse and Moselle rivers in 1994 and 1995 , 1998, Hydrobiologia.

[48]  F. Jones.  The dynamics of suspended algal populations in the lower Wye catchment , 1984 .

[49]  M. Barnett,et al.  Orthophosphate concentrations in the River Thames: reductions in the past decade , 2009 .