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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.
- Residence times in a hypersaline lagoon: using salinity as a tracerPublication . Mudge, S.; Icely, John; Newton, AliceGenerally the waters of the Ria Formosa Lagoon, Portugal have a short residence time, in the order of 0.5 days (Tett, P., Gilpin, L., Svendsen, H., Erlandsson, C.P., Larsson, U., Kratzer, S., Fouilland, E., Janzen, C., Lee, J., Grenz, C., Newton, A., Ferreira, J.G., Fernandes, T., Scory, S., 2003. Eutrophication and some European waters of restricted exchange. Continental Shelf Research 23, 1635e1671). This estimation is based on the measurements of currents and the modelling of water exchange at the outlets to the ocean. However, observations of the temperature and salinity in the inner channels imply that residence time is greater in these regions of the lagoon. To resolve this apparent contradiction, spatial measurements of the temperature and salinity were made with a meter for conductivity, temperature and depth along the principal channels of the western portion of the lagoon, with a sampling frequency of two per second. Evaporation rates of 5.4 mm day 1 were measured in a salt extraction pond adjacent to the lagoon and used to determine the residence time through salinity differences with the incoming seawater. In June 2004, the water flooding in from the ocean had an average salinity of 36.07 which contrasted with a maximum of 37.82 at mid ebb on a spring tide, corresponding to a residence time of >7 days; the mean residence time was 2.4 days. As the tide flooded into the channels, the existing water was advected back into the lagoon. Although there was a small amount of mixing with water from another inlet, the water body from the inner lagoon essentially remained distinct with respect to temperature and salinity characteristics. The residence time of the water was further prolonged at the junction between the main channels, where distinct boundaries were observed between the different water masses. As the water ebbed out, the shallow Western Channel was essentially isolated from the rest of the outer lagoon, and the water from this channel was forced down the Ramalhete Channel, from where it was unable to exit the lagoon in one tidal cycle due to the extensive path length of w14 km to the sea. Although the overall exchange rate of water is short in the outer lagoon, this study emphasizes that management models should take into account additional complexities that might arise from the much longer exchange rates of the inner lagoon. For example, the principal sewage discharge for the urban area of Faro is into the section of the Ramalhete Channel where efficient flushing is impeded by the relatively high residence times of the water body in this channel. The implementation of the techniques used for this study are a quick and relatively cost effective approach to testing assumptions about water quality and exchange in shallow coastal systems.
- Assessment of the water-leaving reflectances of the oceanic and coastal waters using MERIS satellite products in Sagres off the southwest coast of PortugalPublication . Cristina, Sónia; Goela, Priscila; Icely, John; Newton, Alice; Fragoso, BrunoOptical properties of oceanic waters have provided an important tool for observing large scale fluctuations in oceanic conditions by remote sensing. However, there are still problems with calibrating the algorithms that link remote sensing data with in situ measurements, particularly, in coastal areas where there are adjacency affects from land on the reflectance data observed by the satellite sensor. As part of a contract with the European Space Agency to validate the marine products of the MERIS (Medium Resolution Imaging Spectrometer) sensor on the ENVISAT satellite, this study is taking regular measurements with a Satlantic hyperspectral radiometer ranging from inshore to offshore sites, covering both Case-1 and Case-2 waters off the south west coast of Portugal. Water-leaving reflectances (rw) were estimated from downwelling and upwelling spectral irradiances,and compared with MERIS rw for a period between September and November 2008. The results of the “matchup” analysis showed that there was reasonable agreement between the data sets over the period of study at the offshore site where the land adjacency affect on the satellite data was reduced. The greatest deviation of in situ data from satellite values was at the inshore site and at the lower wavelengths of the visible spectrum, where the rws for the blue band were most affected by atmospheric corrections. This study suggests that calibration algorithms of MERIS products with in situ data from the south west coast of Portugal could be improved by using, for example, ICOL ( Improved Contrast between Ocean and Land) processing.
- Microplankton composition, production and upwelling dynamics in Sagres (SW Portugal) during summer 2001Publication . Loureiro, Sofia; Newton, Alice; Icely, JohnMicroplankton community, production, and respiration were studied alongside physical and chemical conditions at Sagres (SW Portugal) during the upwelling season, from May to September 2001. The sampling station was 5 km east of the upwelling center off Cabo S. Vicente, and 2 km of an offshore installation for bivalve aquaculture.
- Oceanographic applications to eutrophication in tidal, coastal lagoons: the Ria Formosa, PortugalPublication . Newton, Alice; Icely, JohnPhysical and biogeochemical processes control the impact of eutrophication in tidal, coastal lagoons and the ecosystem response to nutrient enrichment. Ascreening model of eutrophication in a tidal, coastal lagoon considers a well-mixed box, exchanging with the ocean at a daily rate determined by physical processes and converting nutrient to phytoplankton chlorophyll at a fixed yield. The model uses nutrient levels to estimate maximum biomass, that may be limited by light-controlled growth in turbid, turbulent, highly-diluted or heavily-grazed system. The components of the box model were tested using field data from the Ria Formosa, a mesotidal coastal lagoon in southern Portugal. Sampling coincided with equinox spring tides, in spring and autumn, as well as solstice neap tides, in summer and winter, to cover the full range of tidal exchange. Discrete sampling coincided with high water, mid-ebb, low water and mid-flood to exemplify the different tidal states. Sampling stations included the ocean boundary (lagoon inlet), and two different landward boundary situations: the shallow westernmost “blind end” of the lagoon, and one near to a major sewage outlets. Results show that nutrient loading in the Ria Formosa is sufficiently diluted and flushed by the tides to limit the effects of eutrophication in the outer lagoon. Flushing, however, is insufficient in the inner lagoon. In conclusion, basin-scale parameters in simple box models can be derived from detailed research models and the results of process studies to provide end-users with simple, transparent, screening models for eutrophication and related aspects of water quality.
- Impact of coastal engineering on the water quality of the Ria Formosa Lagoon, PortugalPublication . Newton, Alice; Icely, JohnThe Ria Formosa is a coastal lagoon in southern Portugal. It is a Ramsar and Natura 2000 site and supports important resources such as fisheries, aquaculture and tourism. Human impacts on the Ria Formosa include urbanization, intensive agriculture, aquaculture, and coastal engineering. In this rare, long-term study of a coastal lagoon, the effects of changes in coastal zone management are documented. Data from studies over 12 years are compared to follow the impact of coastal engineering on the water quality of the lagoon. The studies are: • Prior to the opening of the INDIA inlet • Following the opening of the inlet (prior to the operation of the sewage treatment plant) • After the start of the sewage treatment plant operation Recent modifications to the lagoon appear to have improved the water quality of the western lagoon with respect to dissolved oxygen percentage saturation.
- Enrichment experiments and primary production at Sagres (S.W. Portugal)Publication . Loureiro, Sofia; Icely, John; Newton, AliceWater was collected from the Sagres station (SW Portugal) in September 2002, at a site adjacent to the upwelling centre of Cabo São Vicente, during relaxation of upwelling conditions. Surface and depth samples were enriched with inorganic nutrients in order to evaluate their relative influence on the microalgal assemblage. Small-scale, short-term bioassays involved separate in vitro additions of nitrogen and phosphorus. Enrichments with nitrogen led to a general increase of primary production, suggesting nitrogen as the primary potential nutrient limiting microalgal growth during this period, as well as altering the relative microplanktonic composition in favour of diatoms.
- Land Ocean Interactions in the Coastal Zone, LOICZ: lessons from Banda Aceh, Atlantis, and CanutePublication . Newton, Alice; Icely, JohnThis special issue of Estuarine, Coastal and Shelf Science synthesizes and updates the developments in science related to Land Ocean Interactions in the Coastal Zone (LOICZ). Frequent updates about the dynamic coastal zone are useful and necessary as global change accelerates. There is an urgent need to improve the knowledge and understanding of the vulnerability of society and ecosystems to global change hazards in the coastal zone (Vermaat et al., 2005). The collection of papers in this special issue places new developments, findings, techniques and insights within the context of LOICZ science. For the convenience of the reader, the references to papers included in this special issue are printed in italic, whereas other references to LOICZ science are in normal print.
- 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.