http://hdl.handle.net/10174/14284 2026-09-10T18:34:29Z http://hdl.handle.net/10174/42581 Title: Integrating benthic nematode and bacterial communities to assess spatial-temporal dynamics and ecosystem functioning in estuarine sediments Authors: Vieira, Soraia; Adão, Helena; Vicente, Cláudia Abstract: Coastal and estuarine ecosystems are important carbon reservoirs, processes such as recycling of nutrients and degradation of pollutants, occur in soft-sediment intertidal and subtidal habitats. Benthic communities dominated by microorganisms and metazoans play a central role in mediating biogeochemical processes and energy pathways being powerful bioindicators of sediment habitat condition. Strong nematode–bacteria interconnections have been documented, with nematodes stimulating microbial activity and bacteria providing adaptive responses under stressful and low-oxygen conditions. This study aimed to investigate the spatial and temporal interactions between these communities and sediment biogeochemical conditions in the Sado Estuary (Portugal). Combining morphological and molecular approaches, it was explored how biodiversity patterns reflect environmental gradients and ecosystem functioning. Distinct ecological responses between the two biological groups were obtained. Nematode assemblages showed strong spatial and temporal variability, responding rapidly to site-specific environmental changes, whereas bacterial communities were mainly structured by spatial variability directly liked with sediment biogeochemical properties. Combining different approaches bacterial and nematode communities proved to be powerful ecological indicators capable of capturing the dynamics of macrobenthic food webs of the Sado estuary. These relationships between community composition and environmental drivers highlighted that diversity patterns of benthic communities can be integrated to better understand sediment trophic conditions and the impact on energy pathways. The co-occurrence of nematode and bacterial communities can provide a powerful framework for linking biodiversity patterns with ecosystem functioning, improving the evaluation of blue carbon restoration trajectories. The predominance of specific metabolic processes may therefore indicate environmental conditions that favour carbon retention and long-term burial. Such functional insight can contribute to improving the evaluation of blue carbon ecosystems and provide a scientific basis for the development of future predictive frameworks that combine biodiversity data, metabolic pathway analyses, and advanced modelling approaches to assess carbon sequestration potential and support restoration and conservation strategies.   Coastal and estuarine ecosystems represent important carbon reservoirs where key processes such as nutrient recycling, organic matter degradation and pollutant transformation occur in soft-sediment intertidal and subtidal habitats. These environments host complex benthic communities dominated by microorganisms and meiofauna that regulate biogeochemical processes and energy pathways. Among them, benthic bacteria and nematodes are highly sensitive to habitat conditions being powerful ecological indicators of sediment status and functioning. Their interactions have been documented, nematodes stimulate microbial activity, while bacteria provide adaptive responses to nematodes under stressful and low-oxygen conditions. This study investigated the spatial and temporal relationships between nematode assemblages, bacterial communities through different sediment biogeochemical conditions in Sado Estuary (SW cost of Portugal). Combining morphological identification of nematodes assemblages with 16S rRNA metagenomic characterization of bacterial communities, was explored how environmental variations shape biodiversity patterns and ecosystem functioning across contrasting sediment habitats. Results revealed distinct and complementary ecological responses between both groups. Nematode assemblages exhibited strong spatial and temporal variability, responding rapidly to site-specific environmental changes and shifts in trophic conditions, whereas bacterial communities were mainly structured by spatial variability due to sediment properties such as organic matter, grain size and oxygen availability. Together, these communities captured key patterns in benthic ecosystem dynamics. Nematodes reflected short-term ecological responses in line with benthic food webs dynamics, while bacterial communities provided insights into the dominant metabolic pathways driving sediment biogeochemistry. The predominance of specific microbial processes, including aerobic organic matter degradation or anaerobic sulfur-reduction pathways, revealed how environmental conditions regulate energy flow and nutrient cycling in estuarine sediments. The integration of both communities’ diversity provides a powerful framework for linking biodiversity patterns with ecosystem functioning. Combining taxonomic diversity, trophic traits and microbial metabolic pathways, develop integrative ecological framework capable of describing sediment condition and trophic state. Such integrated approaches can support the development of predictive frameworks that evaluate restoration trajectories in blue carbon ecosystems, and estimate the potential for carbon sequestration and long-term carbon burial in coastal sediments. Coupling biodiversity indicators with metabolic and biogeochemical information offers a robust pathway or improving the monitoring and management of estuarine ecosystems, enabling a more comprehensive evaluation of sediment ecological status and their role in long-term carbon storage. 2026-07-06T23:00:00Z http://hdl.handle.net/10174/42548 Title: Tactile stimulation enrichment affects behavioural and physiological responses of a marine commercial fish species, the gilthead seabream Sparus aurata Authors: Soares, Marta C.; Gauy, Ana Carolina dos Santos; Macieira, Júlia; Silva, Bianca Cambiaghi e; Banha, Filipe; Gesto, Manuel; Gonçalves-de-Freitas, Eliane; Saavedra, Margarida Abstract: Fish welfare is gaining increasing attention in both public awareness and research, reflecting a growing recognition and appreciation of its ethical importance in aquaculture. As in nature, reared fish exhibit a range of behaviours and physiological responses suggesting their capacity to experience pain and distress when exposed to deleterious stimuli, however there is a pressing need to aim at the positive aspects of sentience. This study investigated physical and tactile contact as a potential enrichment method for reducing stress and improving welfare in the gilthead seabream Sparus aurata (Linnaeus, 1758). To provide tactile contact, an apparatus made of plastic rods and silicone bristles was used as treatment, while a control setup included only the plastic rods, without the silicone bristles. The experiment lasted 21 days, with fish housed in groups of four per tank. Behavioural assessments were conducted through daily 30-min video recordings, quantifying fish crossing through the bristles, and aggressive displays and attacks. Additionally, half of the fish underwent a confinement stress test on the 22nd day, with cortisol levels and brain monoamines measured to evaluate metabolic stress responses and brain signalling. Individuals in the bristle enrichment group were less inclined to display aggression and showed lower cortisol response after acute stress. Regarding brain monoaminergic activity, differences occurred mostly at two main regional sections: midbrain (central brain section) and hindbrain, both involved in seabream response to acute stress and in connection with bristle enrichment. This is the first demonstration that exposure to tactile stimulation during a limited amount of time is enough to produce behavioural change, mitigate stress responses and modify brain monoaminergic signalling in this important commercial species. 2026-01-01T00:00:00Z http://hdl.handle.net/10174/42546 Title: Living on the Edge: Challenges for Freshwater Mussel Conservation in Mediterranean-Type Temporary Stream Authors: Álvarez, María G.; Rolo, Filipe; Godinho, Francisco; Pinheiro, Paulo; Gil, María; Pires, Daniel; Banha, Filipe; Gama, Mafalda; Anastácio, Pedro M.; Sousa-Santos, Carla; Lima, Cristina Silva; Cardoso, Ana Cristina; Reis, Joaquim Abstract: Mediterranean temporary streams are characterized by high hydrological variability that climate change is expected to intensify, increasing drought frequency and severity. These conditions represent a major threat to freshwater mussels, an imperiled group with limited mobility and strict habitat and host requirements. This study explored key factors shaping freshwater mussel community structure, including the spatial distribution, species compo sition and abundance of coexisting species, in two temporary streams of the Guadiana river basin (southwestern Iberian Peninsula). Pool systems in both streams were characterized and compared under average dry season and extreme drought conditions using aerial imagery, whereas mussel abundance patterns and host–mussel relationships were assessed in the larger and more hydrologically stable stream. Results showed that drought severity had different effects on pool refugia persistence, longitudinal distribution and host fish availability between streams. The smaller stream experienced extensive pool desiccation during extreme drought, causing widespread mussel mortality, whereas the larger stream retained numerous pools that allowed mussel persistence. Mussel abundance showed no relationship with pool size. However, Unio tumidiformis abundance was positively associated with native fish abundance, particularly in upstream reaches. These results highlight hydrological stability and host availability as key drivers of freshwater mussel persistence in Mediterranean temporary streams. 2026-01-01T00:00:00Z http://hdl.handle.net/10174/42545 Title: Moderators of Organic Matter Decomposition in Portuguese Streams: A Field Study and Literature Review Authors: Ferreira, Verónica; Serra, Sónia R. Q.; Calapez, Ana Raquel; Sousa-Santos, Carla; Banha, Filipe; Favas, Paulo J. C.; Graça, Manuel A. S.; Seena, Sahadevan; Rita F., Carvalho; Ribeiro, Filipe; Álvarez, María G.; Pereira, Joana V.; Reis, Joaquim; Canning-Clode, João; Ramalhosa, Patrício; Álvarez, Soledad; Gama, Mafalda; Martelo, Joana; Bedmar, Sergio; Domingues, Andreia; Oliveira, Roberto; Ramos, Jaime; Feio, Maria João Abstract: 1. Organic matter decomposition is a fundamental ecosystem process in streams, which have a large aquatic-terrestrial interface. The sensitivity of organic matter decomposition to changes in environmental conditions promoted by human activities is relatively well understood at large and local scales. In contrast, less is known about the natural variability of organic matter decomposition along natural gradients, especially at intermediate spatial scales. This gap undermines the use of organic matter decomposition as a tool to assess stream functional integrity in biomonitoring programmes. This study aimed at identifying the main moderators of organic matter decomposition under undisturbed conditions to establish natural baseline variation in organic matter decomposition rates in Portuguese streams. 2. A field study was carried out to assess organic matter decomposition rates in 37 least-disturbed streams distributed throughout continental Portugal and Madeira Island. This study addressed gaps in empirical research by using poplar organic matter, including wood, and undertaking the incubation in spring, while previous studies were carried out preferably in autumn/ winter and used alder and oak leaf litter. A systematic literature review was also conducted to compile organic matter decomposition rates from least-disturbed streams across continental Portugal and the Azores archipelago. 3. Organic matter type (leaves or wood), shredder access (fine-mesh or coarse-mesh bags), season (autumn/winter or spring/ summer), water nitrate concentration, the presence of exotic vegetation, distance to the source, and percentage shade emerged as main moderators of organic matter decomposition in the field study. 4. Organic matter type and identity (genus), shredder access, season, stream type (national Water Framework Directive typologies), hydrological regime (permanent or intermittent), water temperature, conductivity, and soluble reactive phosphorus concentrations were also important moderators of organic matter decomposition for the compilation of the field data and literature review data. 5. There was considerable variation in organic matter decomposition across least-disturbed streams, reflecting differences in organic matter type and identity, shredder access, season, and environmental conditions. Therefore, for organic matter decomposition to be used as a tool to assess stream functional integrity, it is necessary to standardise the protocol by selecting specific organic matter types and species, mesh types, and incubation seasons to minimise variation caused by these factors. Choosing stream typologies relevant for the decomposition process (e.g., as outlined in the Water Framework Directive), along with identifying reference decomposition ranges for each typology, may facilitate the assessment of deviations in stream functioning from reference conditions. 2026-01-01T00:00:00Z