TY - JOUR
T1 - Climatic effects on plankton and productivity on the Faroe Shelf
AU - Hansen, B.
AU - Eliasen, S.K.
AU - Gaard, E.
AU - Larsen, K.M.H.
PY - 2005
Y1 - 2005
N2 - Previous investigations have shown that new primary production on the Faroe Shelf during the spring bloom varies considerably from one year to another, both with regard to timing and intensity. It has also been found that variations in new primary production are transmitted up the food chain to top predators such as cod and haddock. An observed inverse relationship between new primary production and zooplankton biomass, especially Calanus finmarchicus, might be due to grazing, but could also reflect a dependence of both new primary production and C. finmarchicus import on the horizontal exchange between waters on the shelf and off it. Here, we investigate this question, using observations and an idealized numerical model. We find that the large variability in new primary production is most likely due to the direct effect of variable horizontal exchange rates on phytoplankton reproduction (horizontal Sverdrup mechanism), rather than grazing. Enhanced horizontal exchange flushes phytoplankton from the shallow areas and limits primary production. Horizontal exchange rate seems most sensitive to horizontal density differences between on-shelf and off-shelf waters, which is governed by atmosphere–ocean heat exchange and precipitation. For the primary observational period from 1990 to 2003, a close relationship was found between air temperature in January–April and new primary production. Cold winters produced large density differences, small horizontal exchange rates, and intensive new primary production. Other, less direct, evidence indicates, however, that this relationship may not have been valid in a period before 1990.
AB - Previous investigations have shown that new primary production on the Faroe Shelf during the spring bloom varies considerably from one year to another, both with regard to timing and intensity. It has also been found that variations in new primary production are transmitted up the food chain to top predators such as cod and haddock. An observed inverse relationship between new primary production and zooplankton biomass, especially Calanus finmarchicus, might be due to grazing, but could also reflect a dependence of both new primary production and C. finmarchicus import on the horizontal exchange between waters on the shelf and off it. Here, we investigate this question, using observations and an idealized numerical model. We find that the large variability in new primary production is most likely due to the direct effect of variable horizontal exchange rates on phytoplankton reproduction (horizontal Sverdrup mechanism), rather than grazing. Enhanced horizontal exchange flushes phytoplankton from the shallow areas and limits primary production. Horizontal exchange rate seems most sensitive to horizontal density differences between on-shelf and off-shelf waters, which is governed by atmosphere–ocean heat exchange and precipitation. For the primary observational period from 1990 to 2003, a close relationship was found between air temperature in January–April and new primary production. Cold winters produced large density differences, small horizontal exchange rates, and intensive new primary production. Other, less direct, evidence indicates, however, that this relationship may not have been valid in a period before 1990.
KW - climate
KW - Faroe Shelf
KW - horizontal exchange
KW - primary production
KW - zooplankton
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-27744453220&partnerID=MN8TOARS
U2 - 10.1016/j.icesjms.2005.04.014
DO - 10.1016/j.icesjms.2005.04.014
M3 - Article
SN - 1054-3139
VL - 62
SP - 1224
EP - 1232
JO - ICES Journal of Marine Science
JF - ICES Journal of Marine Science
IS - 7
ER -