Predicting marine eutrophication: the yield of chlorophyll from nitrogen in Scottish coastal waters

Abstract

There is perceived to be a problem of eutrophication in European marine coastal waters and hence a need to predict the response in terms of enhanced biomass of phytoplankton resulting from the input of anthropogenic nitrogen. This response was investigated indirectly by studying the relationship between nitrate and phytoplankton chlorophyll concentrations in waters of the Scottish west coast. Two-thirds of the 60 data sets analysed gave significant inverse regressions of chlorophyll on nitrate concentration. This result is explained by interpreting synoptic data as representing variation in time, with nitrate decreasing as a result of its assimilation by phytoplankton and conversion into chlorophyll-containing biomass Thus the absolute value of the slope of each significant regression estimates the yield (g) of chlorophyll from nitrate and, indeed, from any form of nitrogen assimilable by microalgae. The median value for q was 1.05 mg chl (mm01 N ) -' ; the range from 0.25 to 4.4 encompassed 95 % of values. Some, but not all, of the variation in q could be explained by error in individual estimates due to chemical-analytical and sampling errors or to inhomogeneities in each sampled phytoplankton population. The remaining variation in q included a seasonal trend, which might have resulted from changes in phytoplankton species composition, nutrient limitation status, or the balance between autotrophic and heterotrophic partitioning of nitrogen. It is suggested that an appropriate value of q can be used to predict the potential maximum increase in phytoplankton which would result from a given anthropogenic nitrogen discharge. The sensitivity of such predictions to error in determination of q is discussed, and the values obtained for q compared with observations in algal culture and mesocosms.

Establishing boundary classes for the classification of UK marine waters using phytoplankton communities

“…Other common indices or attributes of the phytoplankton population that have been used in ecological assessments include bulk measurements of biomass and abundance (OSPAR, 2003;CSTT, 1994CSTT, , 1997, taxon diversity (Karydis and Tsirtsis, 1996), seasonal succession (Hallegraeff and Reid, 1986;Belin et al, 1995;Gailhard et al, 2002) and indicator species (Edwards et al, 2001;Paerl et al, 2003). Phytoplankton biomass has typically been used as indicators of nutrient enrichment (CSTT, 1997;Malcolm et al, 2002;Gowen et al, 1992;Painting et al, 2005). Phytoplankton biomass is a direct measurement of the phytoplankton abundance and in UK waters, it should reflect low numbers in the winter, high spring concentrations, and variable, periodic summer and autumnal blooms.…”

Phytoplankton ecology of Sechelt Inlet, a fjord system on the British Columbia coast. II. Potentially harmful species

“…Chlorophyll exhibited an inverse correlation with nitrate but the relationship was not linear as found by Gowen et al (1992) for the Scottish west coast sea lochs. Our system experienced much greater ranges in chlorophyll (0 to 50 vs 0 to 8 pg 1-l) and nitrate (0 to 30 vs 0 to 4.5 PM) than the Scottish system.…”

Mussels and Yachts in Loch Fyne, Scotland: a Case Study of the Science-Policy Interface

“…The microplankton model parameterizes the coupled dynamics of pelagic microalgae (phytoplankton) as a single entity that includes pelagic protozoa and bacteria (Tett and Wilson 2000). Its main state variable is chlorophyll, which is linked to N and P depletion through a yield coefficient q (Gowen et al 1992). …”

“…The meeting's composition determined how the modeling output was presented and discussed, because there was no tension such as might have http://www.ecologyandsociety.org/vol17/iss3/art16/ (Portilla et al 2009) for Loch Creran. ‡ all other microplankton parameters were calculated from the two adjustable parameters:the 'heterotroph fraction', η (Tett and Wilson 2000), and the chlorophyll yield q (Gowen et al 1992), and the equations and constants given by Portilla et al (2009). § POC = Particulate Organic Carbon.…”