Optical and hydrographic consequences of freshwater runoff during spring phytoplankton growth in a Scottish fjord

McKee, David and Cunningham, Alex and Jones, K. (2002) Optical and hydrographic consequences of freshwater runoff during spring phytoplankton growth in a Scottish fjord. Journal of Plankton Research, 24 (11). pp. 1163-1171. ISSN 0142-7873

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Abstract

A combination of in situ measurements and radiative transfer modelling were used to study optical conditions in the inner basin of Loch Etive, a Scottish fjord, in March and April 2000. The basin was strongly stratified with three layers separated by marked pycnoclines. The surface layer averaged 5 m in depth and was heavily stained with coloured dissolved organic matter (CDOM) which reduced the euphotic depth to between 7 and 10 m. Approximately 20% of the photosynthetically available radiation (PAR) in the water column was absorbed by phytoplankton, 44% by CDOM and 36% by sea water. Detectable concentrations of the major inorganic nutrients (nitrate, phosphate and silicate) occurred at all depths, but significant phytoplankton populations (averaging 6 mg chlorophyll a m-3) were found only in the reduced-salinity surface layer. The freshwater input therefore acted both as a source of buoyancy which promoted phytoplankton growth near the surface and as an attenuator of visible light which inhibited growth deeper in the water column.

ORCID iDs

McKee, David ORCID logoORCID: https://orcid.org/0000-0001-8023-5923, Cunningham, Alex and Jones, K.;
CORE (COnnecting REpositories)