February 1st to 5th 2016
Olhão, Portugal
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Nutrient stoichiometry as a tool for determining nutrient condition in coastal systems

Scientific Exhibition
Biodiversity Effects
Thursday, February 4, 2016 -
17:30 to 19:30

Oduor, N. A. 1 Newton, A. 2 Icely, J.D. 3

1Erasmus WACOMA, Universidad de Cadiz,Spain & University of the Algarve, Portugal
2Norwegian Institute of Air Research
3Centre for Marine and Environmental Research (CIMA), University of Algarve, Sagremarisco

Nutrients and light are critical requirements for primary production that sustain life in coastal ecosystems. The EU Water Framework Directive (WFD), implemented in 2000 recommends assessment of nutrient conditions under the physico-chemical biological supporting elements to ensure the achievement of ‘good ecological status’ by 2015. However, not much work has been carried out to develop tools for assessing nutrient conditions. This study examined the use of nutrient stoichiometry as a tool for assessing nutrient conditions in coastal waters in four sites with different nutrient inputs along the Algarve coast, Portugal namely natural inputs (Praia De Faro), municipal sewage effluents (Ramalhete), agricultural inputs (Ponte) and upwelling inputs (Sagres). This study was carried out for a period of one year between July, 2014 and June 2015. Nutrient concentrations were used to develop nutrient ratios (N: P and N: Si) which were then employed in computing Ecological Quality Ratios (EQR) based on the reference condition (RefCon) and actual deviation (AcDev) of AcStat with percentiles metrics used to establish class boundaries. The final status was defined by averaging N: P and N: Si EQRs. Results showed N: P and N: Si values below normal for Praia De Faro, Ramalhete and Ponte while very high ratios were found for Sagres resulting to Good/Moderate and Moderate/Poor ecological status for all the water bodies under study. This tool is essential for assessment and identification of areas with nutrient condition problems and for establishment of effective management actions to ensure maintenance of healthy coastal ecosystems. The study however recommended the analysis of nutrient stoichiometry together with biological quality elements like phytoplankton, macro-algae and benthic fauna.
keywords: 
Nutrient inputs, Nutrient concentrations, Nutrient ratios, WFD, Ecological status, EQR.

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