TY - JOUR
T1 - Nutrient depletion studies in offshore North Sea areas
AU - Woodward, E. M.S.
AU - Owens, N. J.P.
N1 - Copyright © 1990 Published by Elsevier B.V.
The author was not affiliated to SAMS at the time of publication
Funding Information:
Acknowledgements-The authors wish to thank the Master, officers and crew of the RRS Challenger for their help and service at sea. Also thanks is due to the rest of the North Sea Fertiliser Nitrogen team who were on board the vessel, and particularly to Robin Howland for assistance with the onboard nutrient analysis. These cruises are part of a programme funded in part by the U.K. Department of the Environment, under the contract number PECD 7/7/195.
PY - 1990/5/1
Y1 - 1990/5/1
N2 - Nanomolar nitrate and nitrite concentrations are reported for offshore areas of the North Sea during a research cruise in July 1987. The detection system employed was a sea-going chemiluminescence analyser. Surface concentrations during a period of nutrient depletion are reported, not previously described for this sea area. Very low values for the N/P ratio are reported (<0.1), which suggested that phytoplankton primary production was potentially nitrogen limited during the study period for large areas of the North Sea. Some coastal and river influenced regions exhibited a N/P Redfield ratio of >16, suggesting potential phosphate limitation. As well as the horizontal structure for nitrate and nitrite, vertical profiles are reported showing some structure in the nitrate profile above the thermocline. Nitrate levels generally increased towards the surface, from a minimum at the thermocline, and this may represent an important source of nitrogen to the system during nutrient depletion. A nitrite maximum was observed at the base of the thermocline at the deep water sites, this is attributed to either nitrification or nitrate reduction, and indicates that the thermocline region was a site of active nitrogen regeneration. A significant correlation between primary production and the nitrate concentrations below 100 nmoles.dm-3 was found, showing that the nitrate pool, as well as the recycling rate, remains an important influence during periods of nutrient depletion.
AB - Nanomolar nitrate and nitrite concentrations are reported for offshore areas of the North Sea during a research cruise in July 1987. The detection system employed was a sea-going chemiluminescence analyser. Surface concentrations during a period of nutrient depletion are reported, not previously described for this sea area. Very low values for the N/P ratio are reported (<0.1), which suggested that phytoplankton primary production was potentially nitrogen limited during the study period for large areas of the North Sea. Some coastal and river influenced regions exhibited a N/P Redfield ratio of >16, suggesting potential phosphate limitation. As well as the horizontal structure for nitrate and nitrite, vertical profiles are reported showing some structure in the nitrate profile above the thermocline. Nitrate levels generally increased towards the surface, from a minimum at the thermocline, and this may represent an important source of nitrogen to the system during nutrient depletion. A nitrite maximum was observed at the base of the thermocline at the deep water sites, this is attributed to either nitrification or nitrate reduction, and indicates that the thermocline region was a site of active nitrogen regeneration. A significant correlation between primary production and the nitrate concentrations below 100 nmoles.dm-3 was found, showing that the nitrate pool, as well as the recycling rate, remains an important influence during periods of nutrient depletion.
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U2 - 10.1016/0077-7579(90)90008-5
DO - 10.1016/0077-7579(90)90008-5
M3 - Article
AN - SCOPUS:0025603787
SN - 0077-7579
VL - 25
SP - 57
EP - 63
JO - Netherlands Journal of Sea Research
JF - Netherlands Journal of Sea Research
IS - 1-2
ER -