Impacts of high-nitrate freshwater inputs on macrotidal ecosystems. I. Seasonal evolution of nutrient limitation for the diatom-dominated phytoplankton of the Bay of Brest (France)

Type Article
Date 1997
Language English
Author(s) Del Amo Yolanda1, Le Pape Olivier2, Treguer Paul1, Queguiner Bernard1, Menesguen Alain2, Aminot Alain2
Affiliation(s) 1 : Univ Bretagne Occidentale, Inst Univ Europeen Mer, UMR CNRS 6539 Bioflux, F-29280 Plouzane, France.
2 : IFREMER, Lab Chim & Modelisat Cycles Nat, F-29280 Plouzane, France.
Source Marine Ecology Progress Series (0171-8630) (Inter-research), 1997 , Vol. 161 , P. 213-224
DOI 10.3354/meps161213
WOS© Times Cited 77
Keyword(s) coastal ecosystem, phytoplankton dynamics, macrotidal, nutrient limitation, silicon, eutrophication
Abstract The chemical factors (inorganic nitrogen, phosphate, silicic acid) that potentially or actually control primary production were determined for the Bay of Brest, France, a macrotidal ecosystem submitted to high-nitrate-loaded freshwater inputs (winter nitrate freshwater concentrations >700 mu M, Si:N molar ratio as low as 0.2, i.e. among the lowest ever published). Intensive data collection and observations were carried out from February 1993 to March 1994 to determine the variations of physical [salinity, temperature, photosynthetically active radiation (PAR), freshwater discharges] and chemical (oxygen and nutrients) parameters and their impacts on the phytoplankton cycle (fluorescence, pigments, primary production). With insufficient PAR the winter stocks of nutrients were almost nonutilized and the nitrate excess was exported to the adjacent ocean, due to rapid tidal exchange. By early April, a diatom-dominated spring bloom developed (chlorophyll a maximum = 7.7 mu g l(-1); primary production maximum = 2.34 g C m(-2) d(-1)) under high initial nutrient concentrations. Silicic acid was rapidly exhausted over the whole water column; it is inferred to be the primary limiting factor responsible for the collapse of the spring bloom by mid-May. Successive phytoplankton developments characterized the period of secondary blooms during summer and fall (successive surface chlorophyll a maxima = 3.5, 1.6, 1.8 and 1.0 mu g l(-1); primary production = 1.24, 1.18 and 0.35 g C m(-2) d(-1)). Those secondary blooms developed under lower nutrient concentrations, mostly originating from nutrient recycling. Until August, Si and P most likely limited primary production, whereas the last stage of the productive period in September seemed to be N limited instead, this being a period of total nitrate depletion in almost the whole water column. Si limitation of spring blooms has become a common feature in coastal ecosystems that receive freshwater inputs with Si:N molar ratios <1. The peculiarity of Si Limitation in the Bay of Brest is its extension through the summer period.
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Del Amo Yolanda, Le Pape Olivier, Treguer Paul, Queguiner Bernard, Menesguen Alain, Aminot Alain (1997). Impacts of high-nitrate freshwater inputs on macrotidal ecosystems. I. Seasonal evolution of nutrient limitation for the diatom-dominated phytoplankton of the Bay of Brest (France). Marine Ecology Progress Series, 161, 213-224. Publisher's official version : https://doi.org/10.3354/meps161213 , Open Access version : https://archimer.ifremer.fr/doc/00337/44782/