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- Temporal and spatial variation of phytopigments in the Western part of the Ria Formosa lagoon, Southern PortugalPublication . Pereira, M.; Icely, John; Mudge, S.; Newton, Alice; Rubina, R.The spatial and temporal variation of phytoplankton pigments in the western part of Ria Formosa, Portugal, was investigated between September 2000 and July 2002. Sampling stations included the ocean boundary (Anc˜ao inlet) and two different landward boundary situations: 1) the shallow westernmost “blind end” of the lagoon (Ponte) and 2) near a main sewage outlet (Ramalhete). Nutrient concentrations were higher during the first year of sampling but were lower than those recorded in previous studies. This decrease in the concentration of nutrients was possibly the result of the 1997 relocation of the Anc˜ao inlet, which allowed better water circulation in the lagoon. Throughout this study, concentrations of chlorophyll a determined by high-performance liquid chromatography were consistently low. Inter-annual variability in the pattern of chlorophyll a concentration was observed in the form of a bimodal peak (spring/summer and autumn) between September 2000 and June 2001 and more uniformconcentrations from September 2001 until July 2002. Principal component analysis of the concentrations of all pigments did not indicate any spatial- or tidal-related variations but did show that pigment concentrations varied over time. Partial least squares analysis corroborated this temporal shift of the phytoplankton pigment abundance and composition and showed that these shifts could be linked to certain environmental variables. Fucoxanthin was the dominant accessory pigment and was strongly correlated with chlorophyll a. Other marker pigments present in lower concentrations included chlorophyll b, 19′-hexanoyloxyfucoxanthin, neoxanthin, alloxanthin, diadinoxanthin, lutein, zeaxanthin, and beta-carotene. PLS analysis was used to infer the dominant phytoplanktonic groups in the lagoon. This analysis established that diatoms and other algal groups with a similar pigment profile dominated the phytoplankton community throughout the year. Cryptophytes were the second most abundant group in the lagoon. The remaining groups, including dinoflagellates, cyanophytes, and chlorophytes, contributed much less to the total algal biomass (generally <10%).
- 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.
- 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.
- Boundary conditions for the European Water Framework Directive in the Ria Formosa lagoon, Portugal (physico-chemical and phytoplankton quality elements)Publication . Loureiro, Sofia; Newton, Alice; Icely, JohnThe dynamics between nutrients, the microplankton assemblage and physical factors were evaluated in the Ria Formosa (S. Portugal) coastal lagoon. Water samples were collected from Ramalhete and Ponte within the lagoon and compared with the conditions at Barra, an oceanic inlet. The two lagoon stations represent the boundary conditions of two different water bodies that have been registered as intercalibration sites for the European Water Framework Directive. Sampling coincided with high and low water conditions, at the summer and winter solstice, and at the spring and autumn equinox between June 2001 and July 2002. Chlorophyll a values, with a maximum of 5.1 mg l 1 during growing season, were lower than those reported for similar systems. The maximal winter values of 5.99 mM for total inorganic nitrogen, 0.53 mM for phosphate, and 6.34 mM for silicate, were also lower than previously reported for this area. Microplankton peaked during the summer solstices of June 2001 and July 2002, with maximal abundances of 12 105 cells l 1 and 7 105 cells l 1 for total microplankton, respectively: these communities were dominated by diatoms. At the autumn and spring equinox (September 2001 and April 2002), the maximal abundances were 4.9 105 cells l 1 and 2.6 105 cells l 1 total microplankton, respectively: these communities were more evenly distributed between diatoms, dinoflagellates, nanoflagellates and ciliates. At the winter solstice (December 2001), the microplankton were at their lowest with a maximal abundance of 1.0 105 cells l 1: these communities were dominated by small organisms, particularly nanoflagellates. The oceanic microplankton community at the Barra inlet was generally less numerous and differed in composition from the lagoonal communities at Ramalhete and Ponte. Multivariate analysis clustered the microplankton assemblage according to season. Changes in the microplankton community were related mainly to variations in temperature, solar radiation and salinity, and to the availability of the reduced forms of nitrogen. The differences between the parameters observed at the entrance of the lagoon during the summer solstice of 2001 and 2002 may be due, respectively, to the colder upwelled water during 2001 and the much warmer water observed in 2002. Nutrient enrichment was possible both from coastal waters and from internal lagoonal processes. Consequent accumulation of biomass may occur in inner regions where water circulation is restricted, which may lead to episodes of water quality degradation. This study does not alter the boundary conditions for Ramalhete and Ponte registered at the European Commission, respectively, as ‘good/moderate’ and ‘high/good’.