Marine and Environmental Sciences Centre

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Organizational Unit

Publications

Portable rainfall simulator: evaluation and suitability of plot geometry to improve rainfall uniformity

Publication . Costa, Antônio Reynaldo de Sousa; Alvarenga, Lívia Alves; Thebaldi, Michael Silveira; Melo, Pâmela Aparecida; Colombo, Alberto; Isidoro, Jorge

Os simuladores de chuva são uma importante ferramenta para várias áreas das geociências. Os autores da maioria dos estudos publicados com simuladores de chuva tentam conseguir uma distribuição da precipitação o mais uniforme possível. Contudo, sendo tal muito difícil, são utilizados índices que visam aferir a maior ou menor uniformidade da precipitação na área da parcela em estudo. Um dos mais utilizados é o coeficiente de uniformidade de Christiansen. Neste trabalho, foram analisadas possíveis alterações da geometria da área molhada da parcela para melhorar a uniformidade da precipitação. Isso foi avaliado através da intensidade da precipitação e do coeficiente de uniformidade de Christiansen na área molhada da parcela. Os testes foram realizados utilizando dois modelos de bicos pulverizadores e diferentes pressões de operação. A geometria inicial da parcela era de 0,7 x 1,0 m (0.70 m2). Os resultados do coeficiente de uniformidade de Christiansen foram classificados como baixos, enquanto o melhor desempenho em termos de uniformidade de precipitação foi obtido a uma pressão de 48,3 kPa. A precipitação com menor uniformidade foi observável próximo dos limites externos da parcela. Com base nos melhores resultados do coeficiente de uniformidade de Christiansen, propôs-se reduzir a área útil da parcela experimental de 0,70 para 0,56 m2, levando a uma intensidade de precipitação de 114.07 e 149.20 mm·h−1 e a um coeficiente de uniformidade de Christiansen de 81,6 e 83,8% para os dois modelos de bicos pulverizadores. Os resultados mostraram que proceder com ajustes na geometria da parcela pode conduzir, de forma simples e rápida, a uma maior uniformidade da precipitação artificial.

2023Journal article

Open Access

Spatial and temporal variations of Cockle (Cerastoderma spp.) populations in two portuguese estuarine systems with low directed fishing pressure

Publication . Santos, Cátia; Cabral, Sara; Carvalho, Frederico; Sousa, António; Goulding, Thomas; Ramajal, João; Medeiros, João Paulo; Silva, Gilda; Angélico, Maria Manuel; Gaspar, Miguel; Brito, Ana C.; Costa, José Lino; Chainho, Paula

Cockles are amongst the most exploited bivalve species in Portugal, playing an important ecological and socioeconomic role in coastal ecosystems. Two sympatric species of cockles, Cerastoderma edule (Linnaeus, 1758) and Cerastoderma glaucum (Bruguiere, 1789-1792) may co-occur in estuaries and coastal lagoons in mixed populations along the European Atlantic coast, namely in Portugal, France and the United Kingdom. The increasing importance of shellfish harvesting in Portugal requires a good knowledge of cockle stocks and temporal variability in stock levels to better inform sustainable management practices. Therefore, this study aimed at assessing spatial and temporal variations in cockle populations in two Portuguese estuarine systems where the species are exploited at low levels. Sampling was carried out using a clam dredge, covering the entire potential area of occurrence of cockles in the Tagus and Sado estuaries at around the same time of the year in each of the three sampling years (2015, 2018, and 2019). The abundance, spatial distribution and population structure of cockles were examined at each system. Moreover, several water and sediment parameters were measured to understand the influence of environmental conditions on the spatial distribution and abundance of cockles. The results obtained showed that cockles occur mostly in the intermediate areas of both estuarine systems and are more abundant in the Tagus estuary. Depth, average sediment grain size and the species Ruditapes philippinarum were the factors that better explained the probability of species occurrence. The population structure analysis indicated that natural mortality is constraining the cockle communities given the low abundance of adult individuals with marketable size in both estuaries. This study highlights the need for appropriate management measures to ensure the sustainability of these bivalve population stocks that have significant socioeconomic importance for local populations.

2022Journal article

Open Access

Changing webs—Variation of complex networks over a tidal cycle in an intertidal rocky reef

Publication . Vinagre, Catarina; Mendonça, Vanessa

Incorporating temporal variation in models is one of the most important challenges in food web research. One of the environments where time causes profound changes is the intertidal zone, where the immersion-emersion cycle drastically changes the abiotic and biotic conditions. Intertidal rocky shores have been intensively studied, however the variation in the complex food web network that occurs during a tidal cycle remains undescribed. Highly resolved food web networks were assembled for an intertidal reef depicting the food web during low and high tide, and with and without tide pools. It was concluded that high tide adds new species to the web, but it does not add complexity since network connectance was not changed. This occurs because incoming species are mostly highly generalist fish, which add many new links to the web. Tide pools, however, add not only diversity but also complexity. Webs were dominated by intermediate species, with the proportion of top consumers fluctuating throughout the tidal cycle, being lowest during low tide and highest at high tide, due to the incoming larger vertebrate predators. Consumer taxa outnumbered resource taxa, except at low tide when pools are present. Mean trophic level was lowest at low tide (2.3) and highest at high tide with pools (2.6). Omnivory was high and showed little change. "Chain", the number of links connecting top to basal species, was stable but low. This implies that disturbance can rapidly travel bottom-up or top-down through predator-prey links. The increased connectance given by the addition of tide pools likely increases robustness to disturbances, an important feature in coastal areas so often impacted by human action.

2023-09Journal article

Open Access

Three mitochondrial lineages and no Atlantic-Mediterranean barrier for the bogue Boops boops across its widespread distribution

Publication . Cunha, Regina L.; Faleh, Abderraouf Ben; Francisco, Sara; Šanda, Radek; Vukić, Jasna; Corona, Luana; Dia, Mamadou; Glavičić, Igor; Kassar, Abderrahmane; Castilho, Rita; Robalo, Joana I.

Marine species exhibiting wide distributional ranges are frequently subdivided into discrete genetic units over limited spatial scales. This is often due to specific life-history traits or oceanographic barriers that prevent gene flow. Fine-scale sampling studies revealed distinct phylogeographic patterns in the northeastern Atlantic and the Mediterranean, ranging from panmixia to noticeable population genetic structure. Here, we used mitochondrial sequence data to analyse connectivity in the bogue Boops boops throughout most of its widespread distribution. Our results identified the existence of three clades, one comprising specimens from the Azores and eastern Atlantic/Mediterranean, another with individuals from the Canary Islands, Madeira and Cape Verde archipelagos, and the third with samples from Mauritania only. One of the branches of the northern subtropical gyre (Azores Current) that drifts towards the Gulf of Cadiz promotes a closer connection between the Azores, southern Portugal and the Mediterranean B. boops populations. The Almeria-Oran Front, widely recognised as an oceanographic barrier for many organisms to cross the Atlantic-Mediterranean divide, does not seem to affect the dispersal of this benthopelagic species. The southward movement of the Cape Verde Frontal Zone during the winter, combined with the relatively short duration of the pelagic larval stage of B. boops, may be potential factors for preventing the connectivity between the Atlantic oceanic archipelagos and Mauritania shaping the genetic signature of this species.

2022-12Journal article

Open Access

Gymnodinium catenatum paralytic Shellfish toxin production and photobiological responses under marine heat waves

Publication . Lopes, Vanessa M.; Court, Mélanie; Seco, Martim Costa; Borges, Francisco O.; Vicente, Bernardo; Lage, Sandra; Braga, Ana Catarina; Duarte, Bernardo; Santos, Catarina Frazão; Amorim, Ana; Reis Costa, Pedro; Rosa, Rui

Marine heatwaves (MHWs) have doubled in frequency since the 1980s and are projected to be exacerbated during this century. MHWs have been shown to trigger harmful algal blooms (HABs), with severe consequences to marine life and human populations. Within this context, this study aims to understand, for the first time, how MHWs impact key biological and toxicological parameters of the paralytic shellfish toxin (PST) producer Gymnodinium catenatum, a dinoflagellate inhabiting temperate and tropical coastal waters. Two MHW were simulated—category I (i.e., peak: 19.9 ◦C) and category IV (i.e., peak: 24.1 ◦C)—relative to the estimated baseline in the western coast of Portugal (18.5 ◦C). No significant changes in abundance, size, and photosynthetic efficiency were observed among treatments. On the other hand, chain-formation was significantly reduced under category IV MHW, as was PSP toxicity and production of some PST compounds. Overall, this suggests that G. catenatum may have a high tolerance to MHWs. Nevertheless, some sublethal effects may have occurred since chain-formation was affected, suggesting that these growth conditions may be sub-optimal for this population. Our study suggests that the increase in frequency, intensity, and duration of MHWs may lead to reduced severity of G. catenatum blooms.

2023-02-14Journal article

Open Access