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We write to comment on the recently published paper “Defining phytoplankton class boundaries in Portuguese transitional waters: an evaluation of the ecological quality status according to the Water Framework Directive” (Brito et al., 2012). This paper presents an integrated methodology to analyse the ecological quality status of several Portuguese transitional waters, using phytoplanktonrelated metrics. One of the systems analysed, the Guadiana estuary in southern Portugal, is considered the most problematic estuary, with its upstream water bodies classified as Poor in terms of ecological status. We strongly disagree with this conclusion and we would like to raise awareness to some methodological constraints that, in our opinion, are the basis of such deceptive conclusions and should therefore not be neglected when using phytoplankton to assess the ecological status of natural waters.

Submitted by Ana Barbosa (abarbosa@ualg.pt) on 2012-11-29T11:08:49Z No. of bitstreams: 1 Moran et al 2012 ICES WGPME Report.pdf: 4198242 bytes, checksum: b37ed9ae05945ab8465ad70fa5185489 (MD5) Approved for entry into archive by Merja Muzavor (mmuzavor@ualg.pt) on 2012-11-29T15:04:41Z (GMT) No. of bitstreams: 1 Moran et al 2012 ICES WGPME Report.pdf: 4198242 bytes, checksum: b37ed9ae05945ab8465ad70fa5185489 (MD5) Made available in DSpace on 2012-11-29T15:04:41Z (GMT). No. of bitstreams: 1 Moran et al 2012 ICES WGPME Report.pdf: 4198242 bytes, checksum: b37ed9ae05945ab8465ad70fa5185489 (MD5) Previous issue date: 2012-08

The 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.

This chapter examines the interactions between biologic and hydrologic processes in estuarine and nearshore coastal ecosystems, and their relevance to ecosystem functioning. The role of specific hydrologic variables and processes upon key functional groups of organisms (phytoplankton, heterotrophic bacteria, holozooplankton, merozooplankton, benthos, and nekton) is addressed considering both bottom-up and top-down effects. The impact of biologic processes on relevant hydrologic features, including dissolved gases, inorganic nutrients, organic matter, chemical and biological contaminants, turbidity, and water flow, is then evaluated. Biologic-and hydrologic-driven changes are integrated, specifying how they reverberate into ecosystem functioning over different spatial and temporal scales.

Phytoplankton seasonal and interannual variability in theGuadiana upper estuarywas analyzed during 1996–2005, a period that encompassed a climatic controlled reduction in river flow that was superimposed on the construction of a dam. Phytoplankton seasonal patterns revealed an alternation between a persistent light limitation and episodic nutrient limitation. Phytoplankton succession, with early spring diatom blooms and summer–early fall cyanobacterial blooms, was apparently driven by changes in nutrients, water temperature, and turbulence, clearly demonstrating the role of river flow and climate variability. Light intensity in the mixed layer was a prevalent driver of phytoplankton interannual variability, and the increased turbidity caused by the Alqueva dam construction was linked to pronounced decreases in chlorophyll a concentration, particularly at the start and end of the phytoplankton growing period. Decreases in annual maximum and average abundances of diatoms, green algae, and cyanobacteria were also detected. Furthermore, chlorophyll a decreases after dam filling and a decrease in turbidity may point to a shift from light limitation towards a more nutrient-limited mode in the near future.

The effects of different phases of semidiurnal and spring-neap tidal cycles on phytoplankton and environmental drivers were evaluated in a tidal, freshwater location of a mesotidal estuary (Guadiana estuary, SW Iberia). An Eulerian approach was used and sampling covered different seasons during 2008. Samples were collected during spring and neap tides, at high tide, mid-ebb, low tide and mid-flood. Several physical-chemical variables were measured, as well as phytoplankton abundance and biomass. Salinity was higher at high-tide and suspended particulate matter was higher during spring tides and flood, due to higher vertical mixing and resuspension of bottom sediments. Chlorophyll a concentration during winter and summer neap tides was higher than during spring tides, whilst the abundance of pennate diatoms was higher during winter and Spring spring tides than during neap tides, probably reflecting differences in river discharge. Overall, tidally-induced differences detected in the freshwater tidal reaches of the Guadiana estuary were not as considerable as those observed in the lower estuary. However, the occurrence of tidally-induced variability in some seasons reflects that thorough sampling programs to study estuarine tidal dynamics should be conducted throughout the year. Occasional sampling will not reflect the typical variability of these highly dynamic systems.

Alterations of freshwater flow regimes and increasing eutrophication can lead to alterations in phytoplankton biomass, composition, and growth in estuaries and adjacent coastal waters. Since phytoplankton is the first trophic level of most aquatic foodwebs, these changes can be propagated to other biological compartments, eventually impacting water quality and ecosystem services. However, phytoplankton responses to environmental changes in abiotic variables (e.g., light, nutrients) are additionally controlled by mortality or removal processes (e.g., grazing, horizontal advection and viral lysis). Grazing exerted by microzooplankton, usually dominated by phagotrophic protists, is considered the most relevant phytoplankton mortality factor in most aquatic systems (see Calbet, Landry 2004). In fact, grazing impact of microzooplankton can prevent phytoplankton accumulation in marine systems despite an overall increase in phytoplankton replication rate. By consequence, microzooplankton grazing may minimize problems associated to increased eutrophication and, ultimately, prevent the occurrence of harmful phytoplankton blooms. Thus, microzooplankton grazing on phytoplankton constitutes a key biological process required to understand and predict relationships between hydrological and biological processes in aquatic ecosystems and to use ecosystem properties to improve water quality and enhance ecosystem services, general principles of the Ecohydrology Concept (Zalewski 2000).

Alterations of freshwater flow regimes and increasing eutrophication lead to alterations in light availability and nutrient loading into adjacent estuaries and coastal areas. Phytoplankton community respond to these changes in many ways. Harmful phytoplankton blooms, for instance, may be a consequence of changes in nutrient supply, as well as the replacement of some phytoplankton species (like diatoms, that contribute for the development of large fish and shellfish populations) by ohers (like cyanobacteria, that may be toxic and represent an undesirable food source for higher trophic levels). Nutrient and light enrichment experiments allow us to understand and predict the effects of eutrophication on the growth of phytoplankton. This is a fundamental tool in water management issues, since it enables the prediction of changes in the phytoplankton community that may be harmful to the whole ecosystem, and the design of mitigation strategies (Zalewski 2000).

This synthesis of 3 studies from 2 regions of southern Portugal (Alentejo and Algarve) was part of a workshop focusing on cyanobacteria held at the SAME 10. The first study monitored impacts of the large Alqueva dam on the Guadiana estuary since 1996, revealing changes in sediment load, nutrient regime and phytoplankton succession. Prior to dam construction, dense cyanobacterial blooms occurred in the upper estuary during summer and fall. After dam construction, chlorophyll concentration, phytoplankton diversity and abundances of cyanobacteria decreased, contrary to predictions. Mycrocystins remained at low levels in the seston and undetectable in water samples, except during summer 2003 when the particulate fraction contained 1 μg l–1, while chlorophyll concentrations and abundances of potentially toxic cyanobacteria remained low. Algarve reservoirs studied since 2001 revealed differences in phytoplankton dynamics. In the western mesotrophic reservoirs (Bravura and Funcho), 40 to 50% of surface samples contained cyanobacterial concentrations of ≥2000 cells ml–1, while over 80% of samples from the eastern oligotrophic reservoirs (Odeleite and Beliche) exceeded this value. Spring blooms were dominated by Oscillatoriales in Odeleite and Beliche and by Chroococcales in Bravura and Funcho. Bloom composition seemed to depend on water temperature and management strategies, while toxin concentrations reflected the increased biomass of toxic species. Finally, phytoplankton communities and microcystin production in 5 Alentejo freshwater reservoirs were studied from May to December 2005 and April to July 2006. Cyanobacterial blooms occurred, with varying intensities, not only during summer but also occasionally in winter. Microcystins were detected in 23% of the samples (n = 51), but without correlation with cyanobacterial biomass. Although Microcystis aeruginosa seemed to be the major producer of microcystins, other potentially toxic species were found. In summary, the varying pattern of cyanobacterial bloom occurrence and toxicity requires a systematic approach to monitoring programs for adequate risk assessment.

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.

Tese dout., Ciências do Mar, Universidade do Algarve, 2006 BD/762/90-IG Made available in DSpace on 2011-09-07T16:04:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2005 Junta Nacional de Investigação Científica e Tecnológica (JNICT)

Submitted by Marisa Cesário (mcesario@ualg.pt) on 2013-01-31T16:48:19Z No. of bitstreams: 1 New Medit 2003.pdf: 772831 bytes, checksum: 0cccf767124d4d5c3ad2d700d692d7e4 (MD5) Approved for entry into archive by Emília Pacheco (epacheco@ualg.pt) on 2013-03-18T14:57:18Z (GMT) No. of bitstreams: 2 5665099086848855.zip: 769270 bytes, checksum: 726ae953f53ad58c1116757b9fe5fa8d (MD5) New Medit 2003.pdf: 772831 bytes, checksum: 0cccf767124d4d5c3ad2d700d692d7e4 (MD5) Made available in DSpace on 2013-03-18T14:57:18Z (GMT). No. of bitstreams: 2 5665099086848855.zip: 769270 bytes, checksum: 726ae953f53ad58c1116757b9fe5fa8d (MD5) New Medit 2003.pdf: 772831 bytes, checksum: 0cccf767124d4d5c3ad2d700d692d7e4 (MD5) Previous issue date: 2003

Water samples were collected at bimonthly intervals (April – October 1988) from three stations located in the Ria Formosa coastal lagoon (SE Portugal). Abundance and biovolume of heterotrophic bacterioplankton ranged between 1.2 – 18 x 106 cells.ml-1 and 0.10 - 0.21 μm3.cell-1, respectively. Lowest values were detected at the station close to the ocean and highest values at the station impacted by a domestic effluent. Total bacterial counts showed slight temporal fluctuations while saprophyte numbers (Colony Forming Units) presented a much stronger variation, with maxima during summer. Biovolume exhibited minimal values during summer. Reasons for different patterns of spatial and temporal variability of the bacterial population are discussed.

Submitted by Ana Barbosa (abarbosa@ualg.pt) on 2012-11-29T10:43:20Z No. of bitstreams: 1 Caetano et al 2001 Ecotoxicology and Environmental Restoration.pdf: 557752 bytes, checksum: 3f44d6ed877e0e4c5a9d2b06d5f0f04c (MD5) Approved for entry into archive by Merja Muzavor (mmuzavor@ualg.pt) on 2012-11-29T15:02:49Z (GMT) No. of bitstreams: 1 Caetano et al 2001 Ecotoxicology and Environmental Restoration.pdf: 557752 bytes, checksum: 3f44d6ed877e0e4c5a9d2b06d5f0f04c (MD5) Made available in DSpace on 2012-11-29T15:02:49Z (GMT). No. of bitstreams: 1 Caetano et al 2001 Ecotoxicology and Environmental Restoration.pdf: 557752 bytes, checksum: 3f44d6ed877e0e4c5a9d2b06d5f0f04c (MD5) Previous issue date: 2001

Identifying the environmental drivers of phytoplankton blooms, especially harmful algal blooms, has become imperative for forecasting these events. This study aimed to evaluate phytoplankton variability patterns, phenology and underlying environmental determinants within specific regions off southern Portugal, during a 6-year period (2014-2019). Phytoplankton phenology was assessed using region-specific chlorophyll-a concentration (Chl-a) and abundance of phytoplankton taxa, responsible for amnesic (ASP), diarrhetic (DSP) and paralytic shellfish poisoning (PSP), and relationships between abiotic environmental variables and phytoplankton were explored using Generalized Additive Models (GAM). Over oceanic regions, Chl-a showed a unimodal annual cycle, with increases during the mixed layer deepening phase and late-winter to early-spring maxima. The slope and coastal regions showed an additional summer peak, related with local upwelling, more prominent for the west coast. The development of a coastal counter-current that probably transports riverine nutrients and phytoplankton biomass, might have also contributed for Chl-a increase over the south coast. GAM explained from 14% to 77% of Chl-a variance, with higher explanatory power for oceanic and coastal regions under riverine influence. Sea surface temperature, photosynthetically available radiation, and mixed layer depth emerged as the most influential predictors, and large-scale climate indices showed minor effects. ASP-producing species showed a bimodal annual cycle for most coastal production areas, with first bloom onset in spring, and peak timing during late-spring and summer, associated with upwelling conditions that favour diatom blooms. DSP and PSP-producers exhibited a unimodal annual cycle, peaking during late-summer and late-spring, respectively, during upwelling relaxation periods. DSP models explained between 21% and 54% of the deviance, whereas ASP models revealed a weaker performance (7-8%). In addition to the referred Chl-a predictors, high river discharges exerted a negative influence on both ASP- and DSP-producers. Downwelling/countercurrent regimes globally favoured DSP-producers, while upwelling promoted ASP-producers only over the most southeastern coastal area. Future predictions of harmful phytoplankton blooms for the area should then consider the identified influential predictors but must be complemented with additional environmental variables, and explore specific periods (e.g., seasons, extreme events) and hybrid modelling approaches. O fitoplâncton é o principal produtor primário em ecossistemas marinhos, responsável pela assimilação de CO2 proveniente da atmosfera e transferência de energia para níveis superiores da rede trófica, incluindo os recursos pesqueiros. A variabilidade temporal e espacial do fitoplâncton está relacionada com diversos fatores ambientais, tais como o vento, as correntes oceânicas, o afloramento costeiro, a radiação e temperatura do oceano, turbulência e nutrientes inorgânicos. A identificação dos principais fatores que controlam o florescimento de fitoplâncton, em particular, de espécies produtoras de toxinas, é fundamental para os modelos preditivos, de forma a anteciparem os possíveis impactos associados a futuros florescimentos de algas nocivas. Na presente tese pretendeu-se avaliar os padrões de variabilidade sazonal e interanual do fitoplâncton, bem como identificar os principais forçadores ambientais que ditam a sua abundância em diferentes regiões ao largo da costa sudoeste portuguesa (três regiões costeiras, uma região sob o talude continental e duas oceânicas) caracterizadas por diferentes regimes hidrodinâmicos, durante um período de seis anos (2014-2019). Um conjunto de dados provenientes de deteção remota por satélite (direção e velocidade do vento, temperatura à superfície do oceano, radiação fotossinteticamente ativa e concentração de clorofila-a, Chl-a), modelos (profundidade da camada de mistura), observações in situ (descargas fluviais dos rios Guadiana e Guadalquivir, abundância de grupos de fitoplâncton potencialmente produtores de toxinas e concentração de biotoxinas em duas espécies alvo de moluscos bivalves, Mytilus spp. e Donax trunculus) e indicadores climáticos de larga escala (Multivariate El Niño Southern Oscillation - ENSO, North Atlantic Oscillation - NAO, Atlantic Multidecadal Oscillation - AMO, East Atlantic - EA, Western Mediterranean Oscillation - WeMO) foi utilizado para analisar os padrões de variabilidade intra- e interanual do fitoplâncton. Em particular, as séries temporais de Chl-a e abundância dos grupos de fitoplâncton produtores de toxinas que ocorrem regularmente ao longo da costa portuguesa, em diferentes regiões ou áreas costeiras de produção de moluscos bivalves foram utilizadas para descrever os padrões fenológicos do fitoplâncton. A fenologia baseou-se na análise das seguintes métricas: intensidade, frequência, duração e períodos de iniciação, máximo e término das florescências de fitoplâncton. A aplicação de modelos aditivos generalizados (GAM) a cada região permitiu identificar os forçadores ambientais relevantes para a previsão de Chl-a e dos dois grupos de fitoplâncton mais frequentemente detetados ao largo da costa sudoeste portuguesa, responsáveis pelas síndromes intoxicação amnésica por marisco (Amnesic Shellfish Poisoning, ASP) e intoxicação diarréica por marisco (Diarrhetic Shellfish Poisoning, DSP). Adicionalmente, estes modelos foram ainda utilizados para identificar os padrões de variabilidade intra-anuais e interanuais de Chl-a e dos grupos de fitoplâncton potencialmente produtores de toxinas amnésicas (ASP) e diarréicas (DSP). A distribuição Gaussiana com função de ligação identidade foi aplicada à transformação logarítmica da Chl-a, enquanto para os grupos de fitoplâncton produtores de ASP e DSP, a regressão Binomial Negativa com função de ligação logarítmica foi considerada a mais adequada para ultrapassar o problema de sobredispersão na base de dados. No entanto, a presença de sobredispersão nos dados de abundância do grupo produtor de DSP, em determinadas áreas de produção de bivalves (L6 e L7c-L8), mesmo após a aplicação da regressão Binomial Negativa, sugere que se deveria considerar modelos Zero Inflacionados. Contudo, estes últimos não convergiram para nenhuma área, tendo-se optado pelos resultados obtidos com a primeira distribuição (Binomial Negativa). De modo geral, a Chl-a nas regiões oceânicas exibiu um ciclo anual unimodal, com aumentos durante a fase de aprofundamento da camada de mistura devido ao incremento de nutrientes e/ou à diminuição da mortalidade, e um máximo relativo entre o final do inverno e o início da primavera, provavelmente relacionado com alterações da temperatura e estratificação da camada superficial do oceano. Adicionalmente, filamentos de upwelling, estruturas de mesoescala formadas durante períodos de afloramento costeiro, constituem um importante mecanismo de adveção entre águas costeiras e oceânicas, tal como verificado para a zona oceânica ao largo da costa oeste. A região sob o talude continental exibiu um segundo pico de Chl-a no verão, resultante da combinação dos efeitos da estratificação da coluna da água associada a baixa disponibilidade de nutrientes, e da advecção de nutrientes a partir das zonas costeiras adjacentes durante eventos de afloramento forte. As regiões costeiras também apresentaram um máximo adicional de Chl-a no verão, relacionado com o afloramento costeiro, mais intenso na costa oeste. A presença de uma contracorrente costeira formada durante períodos de relaxamento do afloramento, que provavelmente transporta nutrientes das descargas fluviais e biomassa fitoplânctónica, pode ter também contribuído para o aumento de Chl-a na costa sul. Os modelos aditivos generalizados mistos, aplicados à Chl-a para cada região específica, exibiram uma melhor performance (≥ 60% variância) em oceano aberto e em zonas diretamente influenciadas por descargas fluviais. De modo geral, as variáveis ambientais locais, como a temperatura da superfície do oceano, radiação fotossinteticamente ativa e a profundidade da camada de mistura, emergiram como os preditores mais influentes, enquanto indicadores climáticos de larga escala apresentaram efeitos secundários, menos significativos, destacando-se entre eles o AMO e EA. As espécies de fitoplâncton potencialmente associadas ao síndrome ASP ( Pseudo-nitzschia spp.) apresentaram um ciclo anual bimodal, para a maior parte das áreas de produção de bivalves, com o início dos florescimentos na primavera (mais tarde em relação à Chl-a), e com máximos relativos no final da primavera e verão, em resultado da diminuição da extensão da camada de mistura e aumento da disponibilidade de nutrientes fornecidos pelo afloramento costeiro, favorecendo, assim, as populações de diatomáceas. Pelo contrário, as espécies responsáveis pelos síndromes DSP (e.g., Dinophysis spp.) e PSP (e.g., Gymnodinium catenatum) exibiram um padrão unimodal, com o máximo de abundância no final do verão (assemelhando-se ao padrão de Chl-a nas regiões costeiras), perante situações de estratificação mais intensa entre pulsos de afloramento relativamente fraco ou subsidência da água superficial, que favorecem os dinoflagelados, e final da primavera, respetivamente. No entanto, o pico de espécies potencialmente produtoras de PSP, registado no final da Primavera, não é concordante com a maioria dos estudos que referem uma abundância máxima durante o outono. As espécies potencialmente produtoras de DSP e ASP foram responsáveis pela maioria dos eventos de florescimentos toxigénicos durante o período de estudo, sendo que as espécies associadas ao síndrome ASP atingiram abundâncias mais elevadas, provavelmente devido às elevadas taxas potenciais de crescimento in situ das diatomáceas. Os modelos GAM para espécies potencialmente produtoras de DSP apresentaram um poder preditivo superior (21% - 54% da variância) aos modelos associados a espécies produtoras de ASP (7% - 8% da variância). Para além dos preditores mais influentes referidos para a Chl-a, descargas fluviais elevadas associaram-se a abundâncias inferiores dos grupos produtores de ASP e DSP. Adicionalmente, o regime de convergência/contracorrente associou-se a abundâncias superiores de produtores de DSP, enquanto o regime de afloramento favoreceu a abundância de espécies produtoras de ASP apenas na zona produção sudeste (L9). Contrariamente ao esperado, a intensidade e persistência das condições de afloramento costeiro não foram considerados preditores da abundância de espécies produtoras de ASP na maior parte das áreas de produção, provavelmente devido à existência de um desfasamento temporal (lag) entre as condições favoráveis de afloramento costeiro e a resposta das diatomáceas. Futuros modelos de previsão aplicados à área de estudo deverão assim considerar os preditores mais influentes identificados pelos modelos GAM. Contudo, outras variáveis ambientais deverão também ser ponderados, tais como, a concentração de nutrientes inorgânicos dissolvidos, a turbulência e os processos de mortalidade do fitoplâncton (ex.: predação). Trabalhos futuros poderão ainda contemplar a aplicação dos modelos GAM a diferentes estações do ano, a comparação do desempenho destes modelos com modelos híbridos e a investigação de eventos climáticos extremos. As previsões destes modelos poderão auxiliar na implementação de um sistema de alerta precoce de florescimentos de algas nocivas e no desenvolvimento de programas de gestão integrada dos ecossistemas costeiros mais eficientes. Furthermore, this master thesis was supported by a scholarship within the scope of the project MAR-01.04.02-FEAMP-0003 – CONPRAR – “Contributo para a Proteção do recurso amêijoa Ruditapes decussatus no ecossistema da Ria Formosa”.

Rising atmospheric CO2 alters the ocean biochemistry in the process known as ocean acidification (OA). It influences biodiversity at different levels, including zooplankton, which is a key component of aquatic communities and plays a pivotal role in the structure and functioning of marine planktonic food webs as a major link between pelagic primary producers and planktivorous. The effect of OA on the fitness of individual zooplanktonic species has been reported by many studies mostly developed under laboratory conditions. In this context, this chapter reviews the OA effects on zooplankton and describes the potential of natural shallow-water CO2 vents as in situ laboratories. The impact on zooplankton assemblages is shown from a study in the North Atlantic (Azores islands) and the suitability of this area for future studies on marine organisms and ecosystems. Sites with naturally elevated CO2 conditions are described, including which variables and limitations must be considered. Results shown are highly relevant to improve our predictions of the responses of zooplankton to climate change stressors including OA. Future studies including long-term multigenerational exposure to multiple stressors (e.g. increased pCO2 and food shortage) are a priority to understand the adaptation capacity of common species and how the zooplankton communities will shift.