• Energy Research

The link between biodiversity and ecosystem functioning is now well established, but the challenge remains to develop a mechanistic understanding of observed effects. Predator-prey interactions provide an opportunity to examine the role of resource partitioning, thought to be a principal mediator of biodiversity-function relationships. To date, interactions between multiple predators and their prey have typically been investigated in simplified agricultural systems with limited scope for resource partitioning. Thus there remains a dearth of studies examining the functional consequences of predator richness in diverse food webs. Here, we manipulated a species-rich intertidal food web, crossing predator diversity with total predator density, to simultaneously examine the independent and interactive effects of diversity and density on the efficiency of secondary resource capture. The effect of predator diversity was only detectable at high predator densities where competitive interactions between individual predators were magnified; the rate of resource capture within the species mixture more than doubled that of the best-performing single species. Direct observation of species-specific resource use in monoculture, as quantified by patterns of prey consumption, provided clear evidence that species occupied distinct functional niches, suggesting a mechanistic explanation of the observed diversity effect.

Abstract 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.

Latitudinal gradients in species abundance and diversity have been postulated for nearshore taxa but few analyses have been done over sufficiently broad geographic scales incorporating various nearshore depth strata to empirically test these gradients. Typically, gradients are based on literature reviews and species lists and have focused on alpha diversity across the entire nearshore zone. No studies have used a standardized protocol in the field to examine species density among sites across a large spatial scale while also focusing on particular depth strata. The present research used field collected samples in the northern hemisphere to explore the relationships between macroalgal species density and biomass along intertidal heights and subtidal depths and latitude. Results indicated no overall correlations between either estimates of species density or biomass with latitude, although the highest numbers of both were found at mid-latitudes. However, when strata were examined separately, significant positive correlations were found for both species numbers and biomass at particular strata, namely the intertidal ones. While the data presented in this paper have some limitations, we show that latitudinal macroalgal trends in species density and biomass do exist for some strata in the northern hemisphere with more taxa and biomass at higher latitudes.

We review how intertidal biodiversity is responding to globally driven climate change,\ud focusing on long-term data from rocky shores in the British Isles. Physical evidence of warming\ud around the British Isles is presented and, whilst there has been considerable fluctuation, sea surface\ud temperatures are at the highest levels recorded, surpassing previous warm periods (i.e. late 1950s).\ud Examples are given of species that have been advancing or retreating polewards over the last 50 to\ud 100 yr. On rocky shores, the extent of poleward movement is idiosyncratic and dependent upon life\ud history characteristics, dispersal capabilities and habitat requirements. More southern, warm water\ud species have been recorded advancing than northern, cold water species retreating. Models have\ud been developed to predict likely assemblage composition based on future environmental scenarios.\ud We present qualitative and quantitative forecasts to explore the functional consequences of changes\ud in the identity, abundance and species richness of gastropod grazers and foundation species such as\ud barnacles and canopy-forming algae. We forecast that the balance of primary producers and secondary\ud consumers is likely to change along wave exposure gradients matching changes occurring\ud with latitude, thereby shifting the balance between export and import of primary production.\ud Increases in grazer and sessile invertebrate diversity are likely to be accompanied by decreasing\ud primary production by large canopy-forming fucoids. The reasons for such changes are discussed in\ud the context of emerging theory on the relationship between biodiversity and ecosystem functioning.\ud KEY WORDS: Climate change · Intertidal · Range shifts · Biodiversity · Ecosystem functioning ·\ud Northeast Atlantic

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.

Summary Climate change has led to alterations in assemblage composition. Species of temperate macroalgae at their southern limits in the Iberian Peninsula have shown shifts in geographical range and a decline in abundance ultimately related to climate, but with the proximate factors largely unknown. We performed manipulative experiments to compare physiological responses of Fucus vesiculosus and Fucus spiralis from Portugal and Wales (UK), representing, respectively, southern and central areas of their distribution, to different intensities of solar radiation and different air temperatures. Following exposure to stressful emerged conditions, Portuguese and Welsh individuals of both fucoid species showed increased frond temperature, high desiccation levels and reduced photophysiological performance that was evident even after a 16 h recovery period, with light and temperature acting in an additive, not an interactive, manner. The level of physiological decline was influenced by geographical origin of populations and species identity, with algae from the south and those living higher on the shore coping better with stressful conditions. The negative effect of summer conditions on photophysiology may contribute to changes in fucoid abundance and distribution in southern Europe. Our results emphasise how physiological performance of geographically distinct populations can differ, which is particularly relevant when predicting responses to climate change.