Publication Abstract

Production and its fate in two coastalregions of the Irish Sea: the influence of anthropogenic nutrients

R.J. Gowen, D.K. Mills, M. Trimmer and D.B. Nedwell

Fluvialand sewage loading of N and P to Liverpool Bay (England) elevated winter con-centrationsof dissolved inorganic N (29.2 pM) and P (1.7 pM) and molar ratios of N:P (1'3.0) and N:Si(6.0) compared to Irish coastal waters (9.5 pM N, 0.8 uM P; N:P 12.0 N:Si 1.9). At theenriched site in Liverpool Bay, enhanced spring production (up to 3165.8 mg C m^-'d^-1) summer production (471.8 to 971.5 mg C m^-2 d^-1)and biomass (4.1 to 13.6 mg chorophyll m^-1) was dominated bydiatoms. Annual production at this site was estimated as 182 g C m^-' comparedto 97 g C m^-2 at the Irish coastal sta-tion. Enrichment and shifts in nutrientratios did not favour flagellate growth compared to growth of diatoms in Liverpool Bay.Low amounts of sediment phytopigments (9.2 to 26 mg m^-2), lowconcen-trations of pore water Si (mean, 9.8 uM), and a negligible summer benthic efflux ofSi (1.0 µmol m'² h^-1) suggested little phytodetritalinput to sediments in Liverpool Bay and that summer diatom pro-duction required anallochthonous supply of Si. At the Irish coastal station, coupling between benthic andwater-column processes ensured that benthic efflux of Si was sufficient to support thebulk of summer diatom production. Water-column recycling of N was an order of magnitudegreater than sediment recycling of N at both coastal sites.

Reference:

R.J. Gowen, D.K. Mills, M. Trimmer and D.B. Nedwell, 2000. Production and its fate in twocoastal regions of the Irish Sea: the influence of anthropogenic nutrients. Marine EcologyProgress Series, 208: 51-64.