Physiological tests and bioassays: aids or superfluities to the diagnosis of phytoplankton nutrient limitation? A comparative study in the Broads and the Meres of England

Abstract

Relationships between phytoplankton growth and supplies of phosphorus and nitrogen have been variously investigated in three lakes in two contrasted English lake areas using physiological nutrient indices (alkaline phosphatase activity, phosphorus debt, surplus phosphorus, phosphorus uptake kinetics, dark ammonium uptake, ammonium uptake kinetics, stimulation of "%C uptake, and batch bioassay) and by inspection of water chemistry. None of the lakes was significantly affected by wastewater effluent but all lay in agricultural catchments. Physiological indices and water chemistry suggested limitation of phytoplankton biomass mostly by phosphorus, and to some extent by nitrogen in summer in North Ormesby Broad, by nitrogen in summer and to some extent by phosphorus in Lily Broad and by nitrogen in White Mere. Indices did not always accord with one another, though were not severely misleading. They added little to conclusions that could be drawn from water chemistry alone. Reasons for the differential relative importance of nitrogen and phosphorus in the two lake areas are discussed. The paradigm of phosphorus limitation, though unchallenged in upland waters and those on poorly weathered rocks, may be less relevant in lowland lakes.

Birds as eutrophicating agents: a nutrient budget for a small lake in a protected area

“…There are instances also of eutrophication by intensive stock farming and sewage effluent in the area (Moss et al, 1994) but these sources may be absent yet very high TP concentrations (of the order of mg P l -1 ) found (Moss et al, 1997). In such lakes, bioassays suggest that the phytoplankton is nitrogen limited (Hameed et al, 1999;James et al, 2003). Brown Moss is not such a lake and might be expected to have much more conventional phosphorus concentrations.…”

Nitrate availability and hydrophyte species richness in shallow lakes

“…Nitrogen, however, may be lost through denitrification within plant beds (Weisner et al. , 1994; Eriksson & Weisner, 1999) and algal populations in plant‐dominated shallow lakes are often found to be grazer‐ or nitrogen‐limited in summer (Moss, McGowan & Carvalho, 1994; Hameed et al. , 1999; Meijer et al.…”

Benthic nutrient fluxes in a eutrophic, polymictic lake

“…Studies of lake nutrient cycling, particularly in the Northern Hemisphere, emphasise P release because of its impact on phytoplankton production (e.g., Kleeberg & Kozerski, 1997;Søndergaard et al, 2003). However, N can also limit or co-limit phytoplankton growth (White et al, 1986;Philips et al, 1997;Hameed et al, 1999), and may be as common as P limitation (Elser et al, 1990). Quantification of sediment N and P fluxes and their contribution to the total nutrient load is therefore important in eutrophic lakes and is a prerequisite to targeted nutrient management and lake restoration programmes.…”