Axial variability in the relationship of chlorophyll a with climatic factors and the North Atlantic Oscillation in a Basque coast estuary, Bay of Biscay (1997-2006)

• Published in: Journal of Plankton Research
• Main Authors: Villate, Fernando, Aravena, Guillermo, Iriarte, Arantza, Uriarte, Ibon
• Format: Text
• Language: English
• Published: Oxford University Press 2008
• Subjects: Article; North Atlantic; North Atlantic oscillation
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/fbn056v1; https://doi.org/10.1093/plankt/fbn056

The relationships between chlorophyll a concentration and environmental (climatic and associated hydrographical) factors were investigated in the estuary of Urdaibai (Bay of Biscay) in different salinity zones of the euhaline region, using time series for the period 1997-2006. Transfer function (TF) models were used on quarterly data (3 month mean values) to establish possible relationships between time series. In the non-nutrient limited waters with salinities of 30 and 33 PSU a chain of effects from the North Atlantic Oscillation (NAO) to chlorophyll a was established, where air temperature followed inversely the NAO index, water temperature followed air temperature and chlorophyll a followed water temperature. Each of the steps occurred with a lag of 0 (within the 3 month period), however, the effect from NAO to chlorophyll a showed a lag of 1 (a mean of 3 months delay). Consistent with this result, annual mean chlorophyll a biomass in the 30 and 33 PSU salinity zones showed a significant positive relationship with annual mean water temperature and a significant negative relationship with the twelve-month mean NAO index from October of the previous year to September. In the 35 PSU salinity zone no significant relationship between chlorophyll a and NAO or water temperature was observed. It is suggested that nutrient limitation distorts the effect of temperature on phytoplankton biomass enhancement in the outer estuary (35 PSU salinity zone).