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The natural capacity of marine sediments to capture, sequester, and store organic carbon has been recognized by researchers and policy makers for its potential to mitigate against climate change. As a result, Marine Spatial Planning (MSP) and Marine Protected Area (MPA) designation processes increasingly aim to protect “blue carbon” stored in marine sediments by reducing anthropogenic activities that disturb the seabed (e.g., bottom trawling). In this research, we engaged with coastal residents around Dundalk Bay, Ireland to explore public perceptions of the presence and management of carbon-storing marine sediments in the context of the multifaceted relationship between communities and the environment. This has not been previously studied in an empirical setting. Given the largely “unknown” character of this source of blue carbon, we theorized that speculation played a key role in sustaining emerging perceptions of the sediments, by creating a link with existing place meanings. We used interviews (n = 12) and a focus group (n = 7). Reflexive thematic analysis of the data showed that local residents associated multiple, overlapping meanings with Dundalk Bay. We found evidence that speculative mechanisms such as analogy and experiential knowledge were used to bridge between existing place meanings and emerging perceptions of carbon-storing marine sediments, which also helped indicate the valence of people’s feelings about the sediments. We found different views about the presence of the sediments, and residents varied in their prioritization of measures to protect either nature or economic activity in the bay. Because of scientific knowledge gaps related to the distribution and character of marine sediments and the impacts of anthropogenic activity, participants stressed the need for further research and a careful approach to the management of the bay and its sediments. Our work reiterates the importance of recognizing existing people–place connections to understand potential responses to changes in the use and/or management of marine environments. This can help achieve a more engaged and socially acceptable MSP process.

Coastal environments are among the most productive on the planet, providing a wide range of ecosystem services. Development and exploitation mean that they are faced with stresses from a number of anthropogenic sources. Such stresses are typically studied in isolation, but multiple stressors can combine in unexpected ways to alter the structure of ecological systems. Here, we experimentally explore the impacts of inorganic nutrients and organic matter on a range of food web properties. We find that these two stressors combine additively to produce significant increases in connectance and mean food chain length. Such increases are typically associated with enhanced robustness to secondary extinctions and productivity, respectively. Despite these apparent beneficial effects, we find a simplification of web structure in terms of taxon richness and diversity, and altered proportions of basal and top species. These effects are driven by a reduction in community assembly and lower consistency in a range of system properties as a result of the multiple stressors. Consequently, impacted food webs are likely to be more vulnerable to human- or climate-induced perturbations in the long term.

Invasive ecosystem engineers can physically and chemically alter the receiving environment, thereby affecting biodiversity and ecosystem functioning. The Pacific oyster, Crassostrea gigas, invasive throughout much of the world, can establish dense populations monopolising shorelines and possibly altering ecosystem processes including decomposition and nutrient cycling. The effects of increasing cover of invasive C. gigas on ecosystem processes and associated microbial assemblages in mud-flats were tested experimentally in the field. Pore-water nutrients (NH(4)(+) and total oxidised nitrogen), sediment chlorophyll content, microbial activity, total carbon and nitrogen, and community respiration (CO(2) and CH(4)) were measured to assess changes in ecosystem functioning. Assemblages of bacteria and functionally important microbes, including methanogens, methylotrophs and ammonia-oxidisers were assessed in the oxic and anoxic layers of sediment using terminal restriction length polymorphism of the bacterial 16S rRNA, mxaF, amoA and archaeal mcrA genes respectively. At higher covers (40 and 80%) of oysters there was significantly greater microbial activity, increased chlorophyll content, CO(2) (13 fold greater) and CH(4) (6 fold greater) emission from the sediment compared to mud-flats without C. gigas. At 10% cover, C. gigas increased the concentration of total oxidised nitrogen and altered the assemblage structure of ammonia-oxidisers and methanogens. Concentrations of pore-water NH(4)(+) were increased by C. gigas regardless of cover. Invasive species can alter ecosystem functioning not only directly, but also indirectly, by affecting microbial communities vital for the maintenance of ecosystem processes, but the nature and magnitude of these effects can be non-linear, depending on invader abundance.

1. Loss of biodiversity and nutrient enrichment are two of the most pervasive drivers of change in ecosystems globally. However, little is known about how these disturbances interact to affect ecosystem functioning. 2. We established a field experiment to test for effects of loss of consumer species on algal assemblages (richness and assemblage structure) and ecosystem functioning (ecosystem productivity and algal biomass accumulation) on rocky shores. We manipulated the presence of three common molluscan grazer species in newly created rock pools over 13 months. Our grazer manipulation was based on a subtractive experimental design, and we also manipulated nutrient concentrations to evaluate explicitly how resource availability affected the consequences of species loss. 3. We found that the effects of loss of grazer species on algal assemblages and their functioning depended strongly on both the identity of the grazer species lost and of those remaining in the community. Moreover, the effects of loss of species depended on nutrient availability, making it extremely difficult to predict the effects of species loss generally without detailed knowledge of a system. 4. Our results demonstrate clearly that the effects of grazer species loss on primary producers and ecosystem functioning may not be generalisable based on grazer functional roles or traits. 5. Synthesis. Our findings highlight the need to include key physical drivers, such as nutrient availability, explicitly into biodiversity—ecosystem functioning models in order to move towards a predictive framework that incorporates the effects of both environmental heterogeneity and anthropogenic stressors.

Ecosystems are under pressure from multiple human disturbances whose impact may vary depending on environmental context. We experimentally evaluated variation in the separate and combined effects of the loss of a key functional group (canopy algae) and physical disturbance on rocky shore ecosystems at nine locations across Europe. Multivariate community structure was initially affected (during the first three to six months) at six locations but after 18 months, effects were apparent at only three. Loss of canopy caused increases in cover of non-canopy algae in the three locations in southern Europe and decreases in some northern locations. Measures of ecosystem functioning (community respiration, gross primary productivity, net primary productivity) were affected by loss of canopy at five of the six locations for which data were available. Short-term effects on community respiration were widespread, but effects were rare after 18 months. Functional changes corresponded with changes in community structure and/or species richness at most locations and times sampled, but no single aspect of biodiversity was an effective predictor of longer-term functional changes. Most ecosystems studied were able to compensate in functional terms for impacts caused by indiscriminate physical disturbance. The only consistent effect of disturbance was to increase cover of non-canopy species. Loss of canopy algae temporarily reduced community resistance to disturbance at only two locations and at two locations actually increased resistance. Resistance to disturbance-induced changes in gross primary productivity was reduced by loss of canopy algae at four locations. Location-specific variation in the effects of the same stressors argues for flexible frameworks for the management of marine environments. These results also highlight the need to analyse how species loss and other stressors combine and interact in different environmental contexts.

Functionally unique species contribute to the functional diversity of natural systems, often enhancing ecosystem functioning. An abundance of weakly interacting species increases stability in natural systems, suggesting that loss of weakly linked species may reduce stability. Any link between the functional uniqueness of a species and the strength of its interactions in a food web could therefore have simultaneous effects on ecosystem functioning and stability. Here, we analyse patterns in 213 real food webs and show that highly unique species consistently tend to have the weakest mean interaction strength per unit biomass in the system. This relationship is not a simple consequence of the interdependence of both measures on body size and appears to be driven by the empirical pattern of size structuring in aquatic systems and the trophic position of each species in the web. Food web resolution also has an important effect, with aggregation of species into higher taxonomic groups producing a much weaker relationship. Food webs with fewer unique and less weakly interacting species also show significantly greater variability in their levels of primary production. Thus, the loss of highly unique, weakly interacting species may eventually lead to dramatic state changes and unpredictable levels of ecosystem functioning.

Coastal communities and their landscapes are subject to constant change, and today face new challenges as a result of climate change and the sustainable energy transition. To ensure the resilience of coastal communities to ongoing changes in the natural and constructed environment, it is imperative that planners and other decision‐makers understand the importance of local places to residents. We used an interdisciplinary, mixed‐methods approach to study relationships between coastal residents and places in south Co. Wicklow, Ireland, introducing the concept of ‘affective engagement’. Grounded in new materialist theory (notably actor–network theory), this term connects the meaning derived by residents from their relationships with coastal places (‘affect’) to the extent of their material interactions (‘engagement’). ‘Affect’ was determined from thematic analysis of interviews and open questionnaire responses, as well as place attachment scales included in the questionnaire. Measures describing the strength of the relationship between residents and coastal places were used as a proxy for ‘engagement’. To understand how experienced meaning and material interaction interlink, principal component analysis (PCA) was used to join and visually explore the different measures of ‘affect’ and ‘engagement’. Potentially mediating sociodemographic variables were investigated using a permutational multivariate analysis of variance (PERMANOVA). The majority of self‐selected study participants displayed strong place attachment to their most frequently visited places. We found that affective engagement does not vary with age, gender or type of place. Participants favoured natural and constructed places in equal measure. This implies that constructed places can be of high value due to their different functions for different individuals, and that landscape transformations may impact on coastal residents if they cause a change in functionality. We found two domains comprising affective engagement that are not measurable by quantitative or qualitative data alone. The first of these domains is driven by attachments to places, and the other by meanings relating to either personal or social fulfilment afforded by a place. Our findings may help planners better understand the meanings behind local support for (or resistance against) landscape transformations, and how residents' affective engagement might be impacted by proposed interventions. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.

Understanding and predicting the consequences of warming for complex ecosystems and indeed individual species remains a major ecological challenge. Here, we investigated the effect of increased seawater temperatures on the metabolic and consumption rates of five distinct marine species. The experimental species reflected different trophic positions within a typical benthic East Atlantic food web, and included a herbivorous gastropod, a scavenging decapod, a predatory echinoderm, a decapod and a benthic-feeding fish. We examined the metabolism–body mass and consumption–body mass scaling for each species, and assessed changes in their consumption efficiencies. Our results indicate that body mass and temperature effects on metabolism were inconsistent across species and that some species were unable to meet metabolic demand at higher temperatures, thus highlighting the vulnerability of individual species to warming. While body size explains a large proportion of the variation in species' physiological responses to warming, it is clear that idiosyncratic species responses, irrespective of body size, complicate predictions of population and ecosystem level response to future scenarios of climate change.

Ecosystem functioning underpins the ecosystem services upon which humans rely. Critical functions, such as primary and secondary productivity, are, however, increasingly threatened by a range of anthropogenic stressors. Although the extent of the threat of contamination is large and has been increasing, pollution is one of the least‐studied stressors in ecology. We did a systematic review and critical synthesis of the effects of contaminants on marine and estuarine ecosystem functioning. No other stressors besides toxic chemicals were included in this review. We identified 264 relevant studies across a range of contaminants. Toxic contaminants generally altered marine ecosystem functioning by reducing productivity and increasing respiration. Effects varied, however, according to the type of contaminant and the component(s) of the system studied (e.g. particular trophic levels, functional groups or taxonomic groups). Toxicity studies that included a measure of ecosystem function were strongly biased towards planktonic communities in contrast to studies of biodiversity, which have been dominated by work on soft‐sediment communities. Toxicant studies that included measures of ecosystem function rarely included a measure of biodiversity and rarely interpreted their findings within an ecosystem function context. Studies that included multiple components of an ecosystem, that is more than one functional group of organisms, were more likely to find no effect of contamination, possibly due to ecological interactions. Studies that suffered from unclear or flawed methodology were more likely to find a significant impact of contaminants on some endpoints of ecosystem functioning than studies with appropriate designs. Synthesis and applications. Up to 70% of studies found negative impacts of contaminants on primary production. Toxic contaminants therefore have the potential to greatly affect the ecosystem services and benefits provided by these systems. Our findings will help managers and policymakers to determine whether contaminants are affecting both biodiversity and ecosystem functioning in a given context, therefore helping to prioritize areas for remediation. There is still, however, much to understand about the relationships between biological diversity and ecosystem functioning. Our understanding of chemical contaminant effects will remain patchy until direct measures of both variables are undertaken within multiple ecosystems. We therefore recommend the adoption of functional endpoints, such as productivity and respiration, in ecological studies, routine toxicological studies and ecological risk assessment.