Several invasive species can occupy the same geographic area. Interaction between species depends on several factors, and the results of such interactions can be highly diverse. Asparagopsis armata is a invasive red seaweed whose exudates contain a cocktail of toxic halogenated compounds. In this study, the impact of high and low levels of A. armata on the bivalve Ruditapes philippinarum was assessed in a laboratory experiment. Both are prominent invasive species in Europe and could share the same habitats. The effects of the algae were measured at different biological levels, framed by an integrated approach: bioturbation as a proxy for organismal activity and behaviour within the sediment, and several subcellular biomarkers related to oxidative stress and damage, energy metabolism, detoxification, and neurotransmission. While bioturbation revealed the effects of exudates on the bivalve, with a decrease in most parameters when exposed to the different amounts of algae, only marginal responses were found for biomarkers, suggesting a possible temporal decoupling between the behavioural response and the intrinsic biochemical environment. These results denote that despite the recognized potential of biomarkers to address a myriad of situations, a proxy for higher levels of biological organization, such as behaviour, for its integration of lower-level effects, is a robust tool to address complex and lesser-known mixtures of stressors.

Seagrass meadows provide several ecological functions that improve the overall ecological health of coastal systems and therefore, it is urgent to promote the restoration of such habitats. In Ria de Aveiro, a coastal lagoon in the Atlantic Coast of Portugal, a restoration initiative was responsible for transplanting the dwarf eelgrass Zostera noltei into a highly degraded area. This eelgrass was used as a nature-based solution (NbS) to mitigate some of the impacts of historical mercury contamination. Comparisons of key-species features (density and biomass), and some community-derived indicators (total density and biomass, species richness and Shannon-Wiener index) between the transplanted seagrass patch, their bare vicinities, and their counterpart habitats on the source area, provided signs of the effectiveness of the restoration action on the benthic communities' recovery. Indicators were higher within the restored meadow, and biomass derived indicators of the restored meadow were similar to the source meadow.

Early life phenology is a crucial factor for population dynamics in a climate change scenario. As such, understanding how the early life cycle of marine fishes is influenced by key oceanic and climate drivers is of chief importance for sustainable fisheries. This study documents interannual changes in early life phenology of two commercial flatfishes: European flounder (Platichthys flesus) and common sole (Solea solea) from 2010 to 2015 based on otolith microstructure. Using GAMs, we looked for correlations of the North Atlantic Oscillation (NAO), Eastern Atlantic pattern (EA), sea surface temperature (SST), chlorophyl a concentration (Chla) and upwelling (Ui) variation with the onset of hatch, metamorphosis, and benthic settlement day. We concluded that higher SST, more intensive upwelling, and EA were coincident with a later the onset of each stage, while increasing NAO induces an earlier onset of each stage. Although similar to S. solea, P. flesus showed a more complex interaction with the environmental drivers, most possibly because it is at its southern limit of its distribution. Our results highlight the complexity of the relationship between climate conditions and fish early life history, particularly those with complex life cycles that include migrations between coastal areas and estuaries.

A seasonal characterization of mercury (Hg) accumulation in three different estuaries along the Portuguese coast (i.e. Ria de Aveiro, Tagus estuary and Ria Formosa) was done. For that, it was evaluated: (1) Hg concentrations in abiotic (water) and biotic matrices (flora and fauna); (2) the risk of consumption of local seafood species (e.g. bivalves) to human health; and (3) the environmental risk to Hg exposure. During 1 year, water and biological samples were collected during low tide, in each system for Hg quantification. Our findings revealed that total Hg concentrations in surface waters were higher in Ria de Aveiro and Tagus estuary than in Ria Formosa. In Ria de Aveiro, a particular attention should be given in autumn periods, where Hg levels (≈ 100 µg L−1) were considered quite high according to European quality parameters. The same was observed for the Tagus estuary during spring time. Regarding macrofauna Hg levels, no clear seasonal trend was observed. Also, total Hg concentrations in edible species (< 0.5 µg. g−1 ww) represent no risk for consumption. However, considering the environmental risk, in Ria de Aveiro, there is a moderate risk (RQ > 0.1) in autumn periods, which can be a matter of concern.

Highly impacted coastal systems suffer from degradation of their habitats. Human activities enhance these degradation processes, and seagrasses meadows, which are highly sensitive to those pressures, are among the first habitats to suffer this impact. However, it is recognized that seagrass meadows provide several ecological functions that improve the overall ecological health of these coastal systems and therefore, it is urgent to promote the restoration of such habitats. In Ria de Aveiro, a coastal lagoon in the Atlantic Coast of Portugal, a restoration initiative was responsible for transplanting the dwarf eelgrass Zostera noltei into a highly degraded area, the Laranjo Basin, which had suffered for decades from the deposition of mercury. The dwarf eelgrass was used as a Nature based Solution (NbS) to mitigate some of the impacts of this historical contamination. Comparisons of some key-species features (density and biomass), as well as some community-derived indicators (total density and biomass, species richness and Shannon-Wiener index) between the transplanted seagrass patch, their bare vicinities, and their counterpart’ habitats on the source area, provided some hints of the effectiveness of the restoration action on the benthic communities’ recovery. All indicators were higher within the restored meadow, when compared with the adjacent habitat, and biomass derived indicators of the restored meadow were on a par with the source meadow. These results in abundance and diversity of macrobenthic assemblages after 1 year of transplant are already promising. Given that organisms may respond at different paces, long-term monitoring will be key to assess the success of effect of a seagrass restoration in this contaminated habitat.

Seagrass restoration in open coast environments presents unique challenges. Traditional sod transplant designs, though relatively successful in these environments, are impractical for large-scale restoration due to high biomass requirements. Here, we develop the checkers design, which aims to optimise the usage of biomass by transplanting fewer sods in a checkerboard pattern. We established six plots (9 m2 each) for each species (Zostera marina and Zostera noltei), with 25 sods in each plot. The area, percent cover, density, and leaf length were measured at 1, 6, and 12 months. The plots located on the seaward end of the transplant design vanished over the winter, suggesting location-dependent survival influenced by winter storms. Nevertheless, both species exhibited increased percentages of cover, density, and vegetated area after one year, with variations between species. Z. noltei showed a slower expansion but greater resilience to winter, while Z. marina displayed a higher density and cover over the first 6 months but experienced area loss during the winter. Despite these differences, both species survived and increased vegetated areas after one year, indicating the viability and promise of the checkers method for large-scale restoration. However, careful consideration of location or storm-mitigating measures is essential for the successful implementation of this method.

Rocha is a Portuguese pear cultivar with high economic importance in the Portuguese Western Region. Degradative processes following its manipulation can quickly lead to product rejection, especially when sold as a freshcut product. The efficacy of a marine-based edible coating to inhibit superficial browning development in freshcut Rocha pear slices was investigated over a storage period of 15 days. The aqueous extract of Codium tomentosum, an edible green seaweed, was incorporated in an edible coating (0.5 g 100 mL(-1)) for fresh-cut Rocha pear. This novel treatment effect on the quality parameters of the pears was compared with a commercial coating currently used by industry and a control (dipping in deionised water). After 15 days storage at 4 degrees C, samples treated with the seaweed extract exhibited fewer colour changes and lower rates of superficial browning than control and commercial samples. Seaweed extract treatment was also observed to inhibit yeast and mould development, which may further contribute to shelf-life extension.

Understanding the causes of variation in recruitment of marine fishes has been a central goal over the last century. However, the relationship between year class strength and larval growth and survival is poorly known for most species. The main goal of this study was to investigate the relationships between larval traits and year class strength of two flatfish species in an nursery estuary. We examined the effects of the variation in the early life characteristics (pelagic larval growth, pelagic larval duration, size-at-hatching and size-at-settlement) on post-settlement survival of flounder Platichthys flesus and common sole Solea solea in the Mondego estuary (Portugal) over a 5-year period (2011–2015). The two flatfish species showed distinct larval traits variation during the study period, mainly related with location of the spawning ground and intrinsic biologic patterns. Flounder was able to delay metamorphosis while gathering energy and/or waiting for suitable environmental cues from estuarine origins while sole take advantage of better environmental conditions due to a later hatching. Early fast growth were strongly related with subsequent growth, affecting larval survival. Both growth and larval traits variation during the studied period were strongly related with temperature. This study highlights the importance of early growth for fish survival and contributes with key information on fish early life stages that will support a better management of fish stocks.

The increase in frequency and intensity of extreme climate events over the last few decades has been leading to profound changes in estuarine and marine ecosystems worldwide, with strong implications for the species inhabiting these ecosystems as well as for the services provided by them. In this study, we analysed the effects of climate variability on the temporal and spatial variations in population dynamics of the green crab Carcinus maenas in the Mondego estuary (Portugal), between 2003 and 2018. In this 15-year period, a greater recruitment of C. maenas was observed during drought periods, periods which was matched by an increase in secondary production. Ontogenic stage segregation was also observed, with juveniles being found mainly in the further upriver areas of the estuary. The estuarine population was mainly composed of the green morphotype, with the orange and red morphotypes present in more downstream areas of the estuary. Redundancy analysis (RDA) showed high spatial and temporal variability of C. maenas in the estuary which was related with environmental changes over the 15-year period. A correlation between C. maenas biological features and several local-scale (salinity and river runoff) and large-scale (North Atlantic Oscillation index and Eastern Atlantic pattern) environmental variables was identified through cumulative sums analysis (CUSUM), indicating a strong environmental control on C. maenas population dynamics. This paper shows the importance of relatively long-term datasets to unravel the effects of extreme weather events due to climate change on key epibenthic estuarine species, and also how they might cope with a changing marine environment.

Global warming and the subsequent increase in the frequency of temperature anomalies are expected to affect marine and estuarine species' population dynamics, latitudinal distribution, and fitness, allowing non-native opportunistic species to invade and thrive in new geographical areas. Bivalves represent a significant percentage of the benthic biomass in marine ecosystems worldwide, often with commercial interest, while mediating fundamental ecological processes. To understand how these temperature anomalies contribute to the success (or not) of biological invasions, two closely related species, the native Ruditapes decussatus and the introduced R. philippinarum, were exposed to a simulated heat wave. Organisms of both species were exposed to mean summer temperature (~18 °C) for 6 days, followed by 6 days of simulated heat wave conditions (~22 °C). Both species were analysed for key ecological processes such as bioturbation and nutrient generation-which are significant proxies for benthic function and habitat quality-and subcellular biomarkers-oxidative stress and damage, and energetic metabolism. Results showed subcellular responses to heat waves. However, such responses were not expressed at the addressed ecological levels. The subcellular responses to the heat wave in the invasive R. philippinarum pinpoint less damage and higher cellular energy allocation to cope with thermal stress, which may further improve its fitness and thus invasiveness behaviour.

Understanding how marine fish early-life history is affected in the long-term by environmental and oceanographic factors is fundamental given its importance to population dynamics and connectivity. This work aimed at determining the influence of these processes on the interannual variability in hatch day and early-life growth patterns of European seabass, over a seven-year period (2011-2017) in the Atlantic Iberian coast. To accomplish this, otolith microstructure analysis was used to determine seabass hatch day and to develop early-growth correlations. In most years, hatching occurred from February to April, with two exceptions: in 2012, hatching started in early-January, and in 2016 an exceptionally long hatching period was registered. Using generalized additive models (GAM), we observed that sea surface temperature (SST), the North Atlantic Oscillation index (NAOi) and Chlorophyll-a (Chla) were the main drivers behind the inter-annual variability in seabass hatch day. Analysis of correlations between growth increments allowed assessing important periods of seabass growth and how future growth is affected. Since seawater temperature is among the main drivers for seabass recruitment and growth, its life cycle may be hampered due to ocean warming and an increasingly unstable climate, with consequences for the natural marine stocks and their harvest.

Crustaceans are amongst the most reported invaders of coastal habitats, and predatory brachyuran crabs one of the most successful marine invasive groups. They hold high tolerance to abiotic stress and their genetic, life-history, and behavioural adaptation mechanisms prompt their invasive conspicuousness. However, there is a generalized ambiguity on the specific processes that make these bioinvasions successful. No trait-related patterns have yet been found, mostly since traits attributed solely to non-indigenous crab species lack confirmation by comparison with their native counterparts and across each other. Therefore, this review discusses the available literature on fitness and plasticity of brachyuran crabs under global changes, and advances the increasing importance of addressing native versus non-native invasive species comparisons in the annals of brachyura invasion dynamics. Further on, integrative approaches are highlighted and proposed as innovative tools to disentangle trait-related tolerance, overall crab phenotypic plasticity and further adaptation. These indicator tools will advance the knowledge on crabs' invasive potential, which ultimately affects upcoming population dynamics and ecosystem services, adding value to an effective management of coastal bioinvasions.

Variations in otolith elemental composition are widely used to reconstruct fish movements. However, reconstructing habitat use and environmental histories of fishes within estuaries is still a major challenge due to the dynamic nature of these coastal environments. In this study, we performed a laboratory experiment to investigate the effects of variations in salinity (three levels; 5, 18, 30) and temperature (two levels; 16, 21°C) on the otolith elemental composition (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) of juvenile Senegalese sole Solea senegalensis. Temperature and salinity treatments mirrored the natural conditions of the estuarine habitats occupied by juvenile Senegalese sole, thereby providing information on the applicability of otolith microchemistry to reconstruct habitat use patterns within estuarine nurseries, where individual fish move across complex salinity and temperature gradients. While Sr:Ca and Ba:Ca in otoliths were both positively related to salinity, no temperature effect was observed. Partition coefficients, proxies for element incorporation rates increased with increasing salinity for Sr (DSr) and Ba (DBa). In contrast, salinity and temperature had little influence on otolith Mn:Ca and Mg:Ca, supporting physiological control on the incorporation of these elements. Our results are a stepping stone for the interpretation of otolith chemical profiles for fish collected in their natural habitats and contribute to better understanding the processes involved in otolith element incorporation.

Integrated multi-trophic aquaculture systems can minimize the environmental impacts of aquaculture, while delivering economical benefits. However, the use of extractive species such as seaweeds can accumulate pharmaceuticals commonly used in these systems. Therefore, this work evaluated the exposure of the seaweed Ulva to enrofloxacin (ENR), a vastly used antimicrobial in aquaculture, at two dosages (C1, 7.5 mu g L-1 and C2, 15 mu g L-1), and concentrations in water and in Ulva were measured through time. Traditional endpoints such as growth and mortality were assessed as ENR effects in the macroalgae. Enrofloxacin presented good stability in seawater, and degradation rates were influenced by the presence of seaweed at the lowest concentration tested. The seaweed was able to assimilate the antibiotic, reaching internal concentrations of 7.76 +/- 1.11 ng g(-1) WW after 30 min of exposure for C1, and 14.51 +/- 1.22 ng g(-1) WW, after 15 min for C2. Lowest concentrations detected at the end of experimental time were 4.08 +/- 0.42 ng g(-1) WW and 5.09 +/- 1.57 ng g(-1) WW for C1 and C2, respectively, which nonetheless, corresponds to similar to 5% of the maximum residue limit established for fish for ENR by the European regulation. The presence of ENR stimulated Ulva growth, with differences observed 96 h after the beginning of the trial.

Background: The demand for fish and fish products is now higher than ever. However, several problems such as nutrient loading or excessive use of resources can be associated with the intensification of aquaculture systems. Integrated multitrophic aquaculture systems (IMTAs) refer to the co-culture of different species belonging to different trophic levels, and offer a sustainable approach to aquaculture development. In these systems, organic and inorganic extractive species will feed on other species waste or on uneaten feed nutrients, acting as bioremediators. Scope and approach: The extractive capacity that these organisms have to take up nutrients from the water also means they will accumulate chemicals that are often administered in intensive productions. The present review describes a vast number of substances that can be found in IMTAs, either intentionally administered or resulting from contamination, and subsequently accumulated in species reared afterwards in these systems. The presence of such chemicals in organisms produced in IMTAs raises several food safety and human health concerns, which need to be addressed. Key findings and conclusions: Although IMTAs still face many challenges in terms of large scale production, legislations are not yet ready to comprise co-cultivation of multiple species in proximity. Also, maximum residue limits already existent for fish must be set for other organisms also produced in IMTAs in order to protect consumer's health. An increase in extractive species consumption (e.g. seaweeds) has been noticed during the past few years, and as IMTAs gain importance as a sustainable production method, food safety issues must be tackled.

Changes in community structure concurrent with environmental forcing often form a precursor to changes in species diversity, and can have substantive consequences for ecosystem functioning. Here, we assess the effects of altered levels of evenness that are representative of different levels of eutrophication and changes in salinity associated with altered precipitation patterns, on the mediation of nutrient release by sediment-dwelling invertebrate communities. We find that an adjustment towards a more even distribution of species corresponds with an increase in sediment particle reworking that, in general, translates to increased levels of nutrient release. This response, however, is dependent on the functional role of each species in the community and is influenced by concomitant changes in salinity, especially when salinity extends beyond the range typically experienced by the community. Overall, our findings highlight the dynamic nature of species contributions to functioning and reinforce the importance of understanding when, and how, the mechanistic basis of species-environment interactions are modified as the influence of abiotic and biotic factors flex under periods of directional forcing.

Abstract The freshwater–marine transition that characterizes an estuarine system can provide multiple entry options for invading species, yet the relative importance of this gradient in determining the functional contribution of invading species has received little attention. The ecological consequences of species invasion are routinely evaluated within a freshwater versus marine context, even though many invasive species can inhabit a wide range of salinities. We investigate the functional consequences of different sizes of Corbicula fluminea—an invasive species able to adapt to a wide range of temperatures and salinity—across the freshwater–marine transition in the presence versus absence of warming. Specifically, we characterize how C. fluminea affect fluid and particle transport, important processes in mediating nutrient cycling (NH 4‐N, NO 3‐N, PO 4‐P). Results showed that sediment particle reworking (bioturbation) tends to be influenced by size and to a lesser extent, temperature and salinity; nutrient concentrations are influenced by different interactions between all variables (salinity, temperature, and size class). Our findings demonstrate the highly context‐dependent nature of the ecosystem consequences of invasion and highlight the potential for species to simultaneously occupy multiple components of an ecosystem. Recognizing of this aspect of invasibility is fundamental to management and conservation efforts, particularly as freshwater and marine systems tend to be compartmentalized rather than be treated as a contiguous unit. We conclude that more comprehensive appreciation of the distribution of invasive species across adjacent habitats and different seasons is urgently needed to allow the true extent of biological introductions, and their ecological consequences, to be fully realized.

The main objective of this study was to evaluate the functional traits regarding bioturbation activity and its influence in the nutrient cycling of the native clam species Ruditapes decussatus and the invasive species Ruditapes philippinarum in Ria de Aveiro lagoon. Presently, these species live in sympatry and the impact of the invasive species was evaluated under controlled microcosmos setting, through combined/manipulated ratios of both species, including monospecific scenarios and a control without bivalves. Bioturbation intensity was measured by maximum, median and mean mix depth of particle redistribution, as well as by Surface Boundary Roughness (SBR), using time-lapse fluorescent sediment profile imaging (f-SPI) analysis, through the use of luminophores. Water nutrient concentrations (NH4-N, NOx-N and PO4-P) were also evaluated. This study showed that there were no significant differences in the maximum, median and mean mix depth of particle redistribution, SBR and water nutrient concentrations between the different ratios of clam species tested. Significant differences were only recorded between the control treatment (no bivalves) and those with bivalves. Thus, according to the present work, in a scenario of potential replacement of the native species by the invasive species, no significant differences are anticipated in short- and long-term regarding the tested functional traits.