Browsing by Author "Domingues, Rita B."
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- Ammonium, nitrate and phytoplankton interactions in a freshwater tidal estuarine zone: potential effects of cultural eutrophicationPublication . Domingues, Rita B.; Barbosa, Ana; Sommer, Ulrich; Galvão, Helena M.Nitrate and ammonium are the most important nitrogen sources for phytoplankton growth. Differential utilization of inorganic nitrogenous compounds by phytoplankton has been observed and may have significant impacts on primary productivity at local scales. We used enrichment experiments with natural phytoplankton populations from the freshwater tidal zone of the Guadiana estuary, a coastal ecosystem increasingly subjected to anthropogenic influences, to study the effects of nitrate and ammonium on N-consumption and phytoplankton growth. In addition, we used combined additions of nitrate and ammonium to understand the inhibitory effect of ammonium over nitrate uptake. Ammonium concentrations in the freshwater tidal reaches of the Guadiana estuary throughout the sampling period were too low to exert an inhibitory effect on nitrate uptake or a toxic effect on phytoplankton growth. Nitrate was clearly the main nitrogen source for phytoplankton at the study site. Overall, nitrate seemed to become limiting at concentrations lower than 20 lM and N-limitation was particularly significant during summer. A trend of decreasing nitrate uptake with increasing ammonium concentrations and uptake suggested an overall preference for ammonium. However, preference for ammonium was group-specific, and it was observed mainly in green algae and cyanobacteria. In fact, cyanobacteria relied only on ammonium as their N-source. On the contrary, diatoms preferred nitrate, and did not respond to ammonium additions. The increasing eutrophication in the Guadiana estuary and particularly increased inputs of nitrogen as ammonium due to urban waste effluents may result in a shift in phytoplankton community composition, towards a dominance of cyanobacteria and green algae.
- Are microcosm volume and sample pre-filtration relevant to evaluate phytoplankton growth?Publication . Nogueira, Patrícia; Domingues, Rita B.; Barbosa, Ana B.“Bottle effects” are one of the most deeply rooted concerns of phytoplankton microcosm studies and are mainly related to incubation time and sample volume. Sample pre-filtration to remove larger grazers is also a common procedure in experimental phytoplankton ecology studies, particularly in nutrient enrichment experiments. However, the effects of bottle volume and sample pre-filtration on the outcomes of such experiments, particularly on the net growth rates of specific phytoplankton taxa, have never been addressed. Therefore, this study aims to evaluate the effects of different bottle volumes and sample pre-filtration on phytoplankton net growth rates in microcosm experiments. To accomplish this goal, unfiltered and filtered (b100 μm)water samples, collected in the Guadiana estuary,were nutrient-enriched to avoid nutrient limitation and incubated for 3 days in polycarbonate microcosms with different volumes (0.5 L–8.0 L), inside a plant growth chamber. Phytoplankton composition, abundance, biomass and taxon-specific net growth rates were evaluated throughout the experiment. No systematic significant effects of bottle volume were detected in phytoplankton growth rates. However, sample filtration caused significant changes in phytoplankton composition, with a decline of diatom abundance. Moreover, the removal of large-sized predators and large-sized phytoplankton (diatoms) after sample filtration cascaded down the food web, affecting taxon-specific net growth rates differently. Net growth rates of green algae and eukaryotic picophytoplankton were significantly higher in filtered treatments in respect to unfiltered treatments. Conversely, both diatoms and cryptophytes presented higher net growth rates in unfiltered treatments while net growth rates of picoplanktonic cyanobacteria and plastidic nanoflagellates were not affected by sample filtration.We conclude that, while microcosm volume does not affect results in phytoplankton microcosms, sample pre-filtration may significantly alter the structure of the original phytoplankton community and hence increase the problems associated with the extrapolation of experimental outcomes to the natural environment.
- Are nutrients and light limiting summer phytoplankton in a temperate coastal lagoon?Publication . Domingues, Rita B.; Guerra, Cátia C.; Barbosa, Ana B.; Galvão, HelenaThe Ria Formosa coastal lagoon is one of the most important and vulnerable ecosystems in Portugal, and it is subjected to strong anthropogenic pressures and natural nutrient inputs associated with coastal upwelling. The aim of this study was to evaluate the occurrence of nutrient and light limitation of phytoplankton growth during the productive period, and assess potential impacts of limitation on ecosystem eutrophication. Inorganic nutrients were added to natural microcosms filled with water collected at the landward and seaward boundaries, in summer 2012. Experimental treatments were incubated in situ under two different light intensities during 24 h. Phytoplankton composition, abundance and biomass, net growth rates and nutrient consumption were evaluated. At the landward location, potential nutrient limitation by nitrogen was observed. Nitrogen addition led to a significant increase in N consumption, resulting in higher phytoplankton growth, mainly diatoms, in all N-enriched treatments, under both light intensities. Significant consumption of silica and phosphorus was not reflected on growth, and it was probably due to luxury consumption. At the seaward station, hytoplankton, mainly cyanobacteria and eukaryotic picophytoplankton, were primarily limited by light, due to a deeper mixed layer. Nutrients were not limiting the phytoplankton growth due to import of nutrients from upwelled waters to the adjacent coastal zone.
- Assessing stakeholders’ risk perceptions in a vulnerable coastal tourism destination (Faro beach, Southern Portugal)Publication . Domingues, Rita B.; Costas, Susana; Jesus, Saúl; Ferreira, OscarEffective coastal management is essential in regions where tourism is a main economic activity. However, poor communication and disagreement between stakeholders hamper the way decisions are conveyed to residents and home/business owners, potentially affecting economic development. We analysed managers and scientists' views regarding risk perceptions of Faro Beach (Algarve) residents, contributing to the identification of differences and similarities towards a sustainable management. We used a qualitative content analysis of managers and scientists' discourses. Managers and scientists recognize that residents, particularly fishermen, are quite knowledgeable about the risks they face by living at the beach. However, scientists and managers believe that residents easily forget about the problems due to an optimism bias and positive previous experience with hazards, that never caused fatalities or serious consequences, leading to an underestimation of the severity of the risks. Managers think that residents are not concerned about the environmental problems of Faro Beach, and both scientists and managers see education as the best solution to increase risk perception and concern of residents. We suggest that truly collaborative approaches to coastal management should be promoted, including an active involvement of residents in the decision process, thus increasing their self-efficacy and behavioural control.
- Bottom-up regulation of phytoplankton in the Guadiana estuaryPublication . Domingues, Rita B.; Galvão, Helena M.; Barbosa, Ana B.; Sommer, UlrichPhytoplankton are key players in the aquatic environment and they can be effectively used to understand and predict the functioning and production of aquatic ecosystems. Given that phytoplankton is affected by natural and human-induced perturbations, such as eutrophication and global climate change, it is pressing to understand which factors regulate phytoplankton communities. The main goal of this work was, therefore, to understand how phytoplankton growth and production in the turbid Guadiana estuary, particularly in the freshwater tidal zone, is regulated by bottom-up factors, namely nutrients and light. Enrichment bioassays were carried out to evaluate nutrient and light limitation of phytoplankton growth. Nutrient limitation, specifically by nitrogen, was observed during the productive period. Nitrogen, as nitrate, became limiting to phytoplankton growth at concentrations lower than 20 WM. Although nitrate was the main nitrogen source in the Guadiana estuary, an overall preference for ammonium was observed, mainly by cyanobacteria and green algae. Diatoms were the most nutrient-limited group, and they clearly preferred nitrate as their N-source. Regarding light availability, phytoplankton was not acclimated to the low light conditions that prevail in the Guadiana estuary and light limitation occurred throughout the year. Diatoms were the most light-limited group, whilst cyanobacteria seemed to be more acclimated to low light. Primary production was higher in the more turbid regions, where light availability was the lowest, but nutrient concentrations, although occasionally limiting, were the highest. Therefore, phytoplankton in such turbid regions were the most efficient in using limiting resources. River flow was a major regulator of nutrient and suspended matter inputs to the estuarine zone. Tidallyinduced variability of phytoplankton and environmental drivers in the freshwater tidal estuarine zone was low and resulted from seasonal and fortnightly variability in river flow and tidal currents.
- A brief journey along time in the Guadiana estuaryPublication . Morais, Pedro; Domingues, Rita B.The physical characteristics of the Guadiana estuary and the richness of its adjacent territories were essential in defining the historical and cultural context of the entire region. The extended navigability of the estuary was fundamental to establish trade routes with the Mediterranean civilizations, namely with the Phoenicians, Greeks, and Carthaginians. These civilizations created several commercial harbors along the Guadiana, namely in Mértola, Alcoutim, Castro Marim and Ayamonte. In these locations the human presence dates back as far as the Neolithic (12,000 to 4,000 BCE) and the Chalcolithic periods (4,000 to 3,100 BCE). Later, the Romans (II BCE to V CE), the Alans (V to VI CE.), the Visigoths (VI to VIII CE), and the Arabs (VIII to XIII CE) successively settled in this Iberian region, until the borders of the continental Portuguese territory were set in the 13th century. The predominant North-South direction of the estuary is intrinsically linked with the definition of the Portuguese and Spanish territories, as it serves as a natural border in its last 50 km. Ore extraction and cereal production in the surrounding areas of the estuary turned Mértola into the most important trading center, up to the Portuguese conquest in 1238 (Fig. 6.1). Copper, iron, and manganese were the main ore resources, but silver and gold were exploited as well. With the Portuguese conquests, the economic importance of the Guadiana estuary decreased sharply. In the 15th and 16th centuries, cereals were shipped to the Portuguese forts of northern Africa, but it was only in the late 19th century that all the regions around the estuary had a new economic burst.
- Co-limitation of phytoplankton by N and P in a shallow coastal lagoon (Ria Formosa): implications for eutrophication evaluationPublication . Domingues, Rita B.; Nogueira, Patricia; Barbosa, Ana B.The Ria Formosa coastal lagoon is a highly productive shallow ecosystem in southern Portugal, subjected to nutrient inputs from anthropogenic and natural sources. Nutrients are major abiotic drivers of phytoplankton in this system, but their effects on phytoplankton assemblages and the occurrence of nutrient limitation are still poorly understood. The main goal of this study was, thus, to evaluate the occurrence, type, and effects of nutrient limitation on phytoplankton community and specific functional groups in the Ria Formosa coastal lagoon. We conducted nutrient enrichment experiments with factorial additions of nitrogen (N) and phosphorus (P) using natural phytoplankton assemblages from distinct locations in the Ria Formosa, throughout a yearly cycle. Phytoplankton composition and abundance were evaluated using inverted and epifluorescence microscopies, and spectrophotometric methods were used for biomass. Limitation was defined as higher phytoplankton growth following enrichment with a particular nutrient in relation to the non-enriched control. The most common type of phytoplankton limitation was simultaneous co-limitation by N and P; diatoms, as r-strategists, were the most frequently limited group. Single N and P limitation, and serial P limitation were also observed, as well as negative responses to nutrient enrichment. Group-specific responses to nutrient enrichment were not reflected in the relative abundance of phytoplankton groups within the whole assemblage, due to the numerical dominance of pico-sized groups (cyanobacteria and eukaryotic picophytoplankton). Ambient nutrient ratios and concentrations did not predict phytoplankton nutrient limitation, given the different nutrient utilisation traits among phytoplankton functional groups. Therefore, nutrient ratios should not be used as indicators of nutrient limitation in eutrophication assessment.
- Connections between upwelling patterns and phytoplankton variability under different coastal regimes in SW Iberia PeninsulaPublication . Krug, Lilian; Silvano, Kathleen M.; Barbosa, Ana B.; Domingues, Rita B.; Galvão, Helena M.; Luis, Joaquim; Platt, Trevor; Relvas, Paulo; Sathyendranath, ShubhaThe region off southwestern Iberia (NE Atlantic) encompasses a wide variety of oceanographic regimes, including differently (geographic) oriented coastal areas impacted by upwelling, riverine inputs and submarine groundwater discharge, submarine canyons and seamounts, and open ocean waters, thereby potentially promoting zone-specific phytoplankton dynamics. Overall, this heterogeneous region is classified as being very sensitive to climate change, and climate-driven alterations (e.g., sea surface warming, changes in upwelling patterns and intensity) have been recently reported for the area. The present study aims to understand the contribution of upwelling to seasonal and interannual variability of coastal phytoplankton, using a remote sensing-based approach. Phytoplankton variability was evaluated using satellite-derived chlorophyll-a (Chl-a), as a proxy for phytoplankton biomass, and primary productivity (PP). Chl-a were obtained from merged SeaWiFS (Seaviewing Wide Field-of-view Sensor), MeRIS (Medium Resolution Imaging Spectrometer) and MODIS-Aqua (Moderate-resolution Imaging Spectroradiometer) sensors at Globcolour portal. PP data at 9.25 km resolution were derived from Eppley’s Vertically Generalized Production Model, based on SeaWiFS and MODIS-Aqua and available at the Ocean Productivity site. Upwelling intensity was estimated using the difference in sea surface temperature (SST) between off and nearshore zones. Advanced Very-High Resolution Radiometer (AVHRR) 4 km SST were obtained from Pathfinder database. Other phytoplankton environmental drivers, such as local (e.g., river flow) and global (e.g., North Atlantic Oscillation - NAO) climate variables, were also analysed. The study area was divided into subareas differently impacted by upwelling and riverine flow, and satellitederived data was averaged for each zone. Seasonal and interannual variability covering a 14-year time series (1998- 2011) for each variable/region were explored. Chl-a at offshelf locations was significantly lower than coastal areas, and exhibited a fairly stable unimodal annual cycle, with maximum during March. Coastal locations displayed more variable annual patterns, with spring and summer Chl-a maxima, reflecting the impact of upwelling events and freshwater inputs. In respect to interannual variability, NAO index and coastal Chl-a were negative and significantly correlated, with 1-month lag. Chl-a interannual trends were also correlated to local climate variables, namely riverine flow for the easternmost coastal zone. The correlation between upwelling intensity and phytoplankton off SW Iberia is region-dependent being less strong within regions dominated by riverine influence.
- Constrains on the use of phytoplankton as a biological quality indicator within the Water Framework Directive in portuguese watersPublication . Domingues, Rita B.; Barbosa, Ana B.; Galvão, Helena M.The European Union Water Framework Directive (WFD), a new regulation aiming to achieve and maintain a clean and well-managed water environment, refers to phytoplankton as one of the biological quality elements that should be regularly monitored, and upon which the reference conditions of water quality should be established. However, the use of phytoplankton as a biological quality element will result in several constraints, which are analyzed in this article with examples from Portuguese waters. Specifically, the establishment of reference conditions of water quality may be difficult in some water bodies for which no historical data exists. The sampling frequency proposed for phytoplankton monitoring does not seem suitable to assess phytoplankton succession, and may preclude the detection of algal blooms. Finally, the use of chlorophyll a as a proxy of phytoplankton biomass and abundance has been proposed by some authors, but it may overlook blooms of pico- and small nanophytoplankton, and overestimate the importance of large microphytoplankton. Furthermore, most studies in Portugal have used only inverted microscopy for phytoplankton observation and quantification; this method does not permit the distinction between autotrophic and heterotrophic cells, especially in samples preserved with Lugol’s solution, and does not allow the observation of smaller-sized cells. Finally, some techniques, such as remote sensing and chemotaxonomic analysis, are proposed to be used as supplements in phytoplankton monitoring programs.
- Depression and quality of life in older adults: Mediation effect of steep qualityPublication . Brandolim Becker, Nathália; de Jesus, Saul Neves; Viseu, João; Stobaus, Claus Dieter; Guerreiro, Mariana; Domingues, Rita B.Background/Objective: Sleep insufficiency, which affects more than 45% of the world's population, has a great importance when considering older adults. Thus, this research tested a mediation hypothesis, through a path analysis, which explains how depression relates to the quality of life considering the effect's of sleep quality in older adults. Method: A sample of 187 community-dwelling Portuguese older adults answered questionnaires about sociodemographic status (age, gender, highest level of education completed, family status, sports activities, health, and retirement status), quality of life, sleep quality, and depression. Descriptive and path analysis statistics were performed considering the results of the normality test. Results: The sample has health characteristics and presents adequate sleep duration. Sleep quality acted as a mediator between depression and the quality of life in older adults, considering the variation of gender and health. This suggests that it is important to establish self-care practices, namely sleep quality, to intervene in the ageing process. Conclusions: It is important to consider sleep quality associated with depression for older adults and to test interventions to minimize health impacts. Also, more researches are needed about the primary prevention in steep quality relating to depression. (c) 2017 Asociacion Espanola de Psicologia Conductual. Published by Elsevier Espana, S.L.U.