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- Evaluation of eutrophication in the Ria Formosa coastal lagoon, PortugalPublication . Newton, Alice; Icely, John; Falcão, Manuela; Nobre, A.; Nunes, J.; Ferreira, J.; Vale, C.The Ria Formosa is a shallow mesotidal lagoon on the south coast of Portugal, with natural biogeochemical cycles essentially regulated by tidal exchanges at the seawater boundaries and at the sediment interface. Existing data on nutrients in the water column and the sediment, together with chlorophyll a and oxygen saturation in the water column,compared using different models for assessing eutrophication. The European Environmental Agency criteria are based on the comparison of nutrient concentrations which indicate that the situation in the Ria Formosa is ‘‘poor’’ to ‘‘bad’’. In contrast, the United States Estuarine Eutrophication Assessment is based on symptoms, including high chlorophyll a and low oxygen saturation, which indicate that the Ria Formosa is near pristine. Despite these contradictions, a preliminary assessment by Driving forces, Pressures, State, Impact, Reponses(DPSIR) of eutrophication demonstrate the potential for episodic eutrophic conditions from treated and untreated domestic effluent as well as from non-point source agricultural run off. Sediments are also an important source of nutrients in the lagoon, but their contribution to potential eutrophic conditions is unknown.
- The yield of chlorophyll from nitrogen: a comparison between the shallow Ria Formosa lagoon and the deep oceanic conditions at Sagres along southern coast of PortugalPublication . Edwards, Vivien; Icely, John; Newton, Alice; Webster, RuthThe yield of chlorophyll from dissolved inorganic nitrogen (DIN) has been shown to be a potentially useful parameter for predicting eutrophication, particularly, in the northerly, coastal waters of the North East Atlantic (NEA). This study investigates whether this parameter might also be appropriate for the southerly, coastal waters of the NEA. Nitrogen enrichment experiments were carried out using microcosms to determine the microplanktonic yield of chlorophyll from DIN in waters from the Ria Formosa (April 2002) and from Sagres (September 2002) on the south coast of Portugal. Continuous culture techniques enabled experiments to be run for 7 days after enrichment so that changes in the cumulative yield over time could be calculated. Yields from the Sagres experiment were consistently higher than those from the Ria Formosa experiment, with respective maximum yields of 4.7 and 2.1 mg chl (mmol N) 1, and respective steady-state yields of 3.1 and 0.9 mg chl (mmol N) 1. In addition, regressions carried out on historical data sets from the two study sites showed poor correlation between chlorophyll and nitrate. Other differences between the microcosm experiments at the two sites, included: background concentrations of DIN, silicate and phosphate that were, respectively, 5.6 mM, 8.1 mM, and 0.3 mMhigher in the Ria; chlorophyll concentrations at Sagres that were double those of the Ria; accumulation of particulate nitrogen that was both more rapid and more substantial at Sagres; a different community structure for the diatoms at the two sites; more numerous autotrophic dinoflagellates, flagellates and cyanobacteria, as well as more numerous protozoan grazers, at Sagres. These differences may explain why the yield of chlorophyll from DIN at Sagres is one of the highest reported in the literature. This yield parameter requires further study under a range of seasonal conditions and with a range of microplankton communities before it could be considered useful for predicting eutrophication throughout the coastal waters of the NEA.
- Identifying the source of nutrient contamination in a lagoon systemPublication . Wayland, D.; Megson, D.; Mudge, S.; Icely, John; Newton, AliceNutrient concentrations within watercourses are often associated with the input of sewage or the runoff of fertilizers. Due to population increases, there has been a dramatic rise in the amount of fertilizer applied to land, as well as in the further development of sewage treatment plants (STPs), both of which can lead to significant discharges with associated eutrophication risks in coastal waters. The implementation of the European Union Water Framework Directive (EU-WFD) should improve the management and quality of European water bodies. The Ria Formosa Lagoon, Portugal, is one such water body monitored under the WFD where two inter-calibration sites have been developed, that of the Anc˜ao Basin, which has a status of “high/good,” and that of the Ramalhete Channel, with a status of “good/moderate.” Spatial nutrient concentrations (NH+ 4 , NO–2 , NO–3 , PO3–4 ) and lipids were measured in two areas that were thought to contribute nutrients into the Anc˜ao Basin; a river that flows through several golf courses and the Ramalhete Channel, which receives discharge from both Faro Airport and a STP. Nutrient analyses showed that waters from the Ramalhete Channel had substantial concentrations, the highest of which was ammonium, which exceeded 180 μM near the sewage discharge site; however, concentrations diminished towards the sea, reaching 2.7 μM suggesting the utilization of NH+4 by seagrasses (Zostera noltii).The Atlantic Ocean was also a source of nitrate, contributing 1.8 μM, whereas sources of phosphate originated in the Anc˜ao Basin catchment and included a commercial horticulture site,several golf courses, and the STP. Principal component analysis (PCA) and cross plots of the 5β-coprostanol/cholesterol and 5β-coprostanol/(5β-coprostanol + 5α-cholestanol) ratios identified areas of fecal contamination, highlighting several sites previously unknown to contain sewage matter. In general, nitrogen sources were associated with agriculture and phosphate originated from the golf complex and sewage discharges. These effects were partly mitigated, however, by eutrophic ponds between the river and the lagoon.