Artificial light at night reverses monthly foraging pattern under simulated moonlight.

Mounting evidence shows that artificial light at night (ALAN) alters biological processes across levels of organization, from cells to communities. Yet, the combined impacts of ALAN and natural sources of night-time illumination remain little explored. This is in part due the lack of accurate simulations of the complex changes moonlight intensity, timing and spectra throughout a single night and lunar cycles in laboratory experiments. We custom-built a novel system to simulate natural patterns of moonlight to test how different ALAN intensities affect predator-prey relationships over the full lunar cycle. Exposure to high intensity ALAN (10 and 50 lx) reversed the natural lunar-guided foraging pattern by the gastropod mesopredator Nucella lapillus on its prey Semibalanus balanoides. Foraging decreased during brighter moonlight in naturally lit conditions. When exposed to high intensity ALAN, foraging increased with brighter moonlight. Low intensity ALAN (0.1 and 0.5 lx) had no impact on foraging. Our results show that ALAN alters the foraging pattern guided by changes in moonlight brightness. ALAN impacts on ecosystems can depend on lunar light cycles. Accurate simulations of night-time light cycle will warrant more realistic insights into ALAN impacts and also facilitate advances in fundamental night-time ecology and chronobiology.

Local and large-scale spatial variation in a marine predator-prey interaction in the southwestern Atlantic.

Predator-prey interactions are a key ecological process which can be modified by environmental conditions over a range of spatial scales. Through two complementary short-term experiments, we assessed how local and large-scale environmental conditions affect a subtropical intertidal predator-prey interaction. At a local scale, we evaluated the effects of the degree of exposure to wave action and prey density on consumption rate and interaction strength using a whelk-barnacle system. Consumption rate decreased with wave exposure at experimentally reduced prey density but did not change at ambient density. Such an interactive effect occurred due to shifts in the whelk's feeding behaviour, likely linked to encounter rate and stress amelioration underpinned by prey density. Per capita interaction strength of the whelk on the barnacle weakened along the wave exposure gradient, but to a greater degree at reduced compared to ambient prey density. This confirms that environmental harshness can decrease the importance of predators, but the magnitude of change may be modified by density-dependent effects. A large-scale experiment did not reveal spatial patterns in the whelk-barnacle interaction, nor relationships to chlorophyll-a concentration or the minor change in sea temperature across the study area. Patterns in the size of consumed barnacles along the chlorophyll-a gradient suggest changes in food choice related to prey quality and size. We conclude that disentangling the effects of wave exposure and prey density revealed important potential mechanisms driving species locally. Large-scale variation in the whelk-barnacle interaction appeared to be linked to species' traits shaped by the environmental context.

Artificial shorelines lack natural structural complexity across scales.

From microbes to humans, habitat structural complexity plays a direct role in the provision of physical living space, and increased complexity supports higher biodiversity and ecosystem functioning across biomes. Coastal development and the construction of artificial shorelines are altering natural landscapes as humans seek socio-economic benefits and protection from coastal storms, flooding and erosion. In this study, we evaluate how much structural complexity is missing on artificial coastal structures compared to natural rocky shorelines, across a range of spatial scales from 1 mm to 10 s of m, using three remote sensing platforms (handheld camera, terrestrial laser scanner and uncrewed aerial vehicles). Natural shorelines were typically more structurally complex than artificial ones and offered greater variation between locations. However, our results varied depending on the type of artificial structure and the scale at which complexity was measured. Seawalls were deficient at all scales (approx. 20-40% less complex than natural shores), whereas rock armour was deficient at the smallest and largest scales (approx. 20-50%). Our findings reinforce concerns that hardening shorelines with artificial structures simplifies coastlines at organism-relevant scales. Furthermore, we offer much-needed insight into how structures might be modified to more closely capture the complexity of natural rocky shores that support biodiversity.

Harnessing positive species interactions as a tool against climate-driven loss of coastal biodiversity.

Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions.

Using structured eradication feasibility assessment to prioritize the management of new and emerging invasive alien species in Europe.

Prioritizing the management of invasive alien species (IAS) is of global importance and within Europe integral to the EU IAS regulation. To prioritize management effectively, the risks posed by IAS need to be assessed, but so too does the feasibility of their management. While the risk of IAS to the EU has been assessed, the feasibility of management has not. We assessed the feasibility of eradicating 60 new (not yet established) and 35 emerging (established with limited distribution) species that pose a threat to the EU, as identified by horizon scanning. The assessment was carried out by 34 experts in invasion management from across Europe, applying the Non-Native Risk Management scheme to defined invasion scenarios and eradication strategies for each species, assessing the feasibility of eradication using seven key risk management criteria. Management priorities were identified by combining scores for risk (derived from horizon scanning) and feasibility of eradication. The results show eradication feasibility score and risk score were not correlated, indicating that risk management criteria evaluate different information than risk assessment. In all, 17 new species were identified as particularly high priorities for eradication should they establish in the future, whereas 14 emerging species were identified as priorities for eradication now. A number of species considered highest priority for eradication were terrestrial vertebrates, a group that has been the focus of a number of eradication attempts in Europe. However, eradication priorities also included a diverse range of other taxa (plants, invertebrates and fish) suggesting there is scope to broaden the taxonomic range of attempted eradication in Europe. We demonstrate that broad scale structured assessments of management feasibility can help prioritize IAS for management. Such frameworks are needed to support evidence-based decision-making.

Successional convergence in experimentally disturbed intertidal communities.

Determining the causes of variation in community assembly is a central question in ecology. Analysis of ß-diversity can provide insight by relating the extent of regional to local variation in diversity, allowing inference of the relative importance of deterministic versus stochastic processes. We investigated the effects of disturbance timing on community assembly at three distinct regions with varying environmental conditions: Northern Portugal, Azores and Canaries. On the lower rocky intertidal, quadrats were experimentally cleared of biota at three distinct times of the year and community assembly followed for 1 year. Similar levels of α- and γ-diversity were found in all regions, which remained constant throughout succession. When Jaccard (incidence-based) and Bray-Curtis (abundance-based) metrics were used, ß-diversity (the mean dissimilarity among plots cleared at the different times) was larger during early stages of community assembly but decreased over time. The adaptation of the Raup-Crick's metric, which accounts for changes in species richness, showed that the structure of assemblages disturbed at different times of the year was similar to the null model of random community assembly during early stages of succession but became more similar than expected by chance. This pattern was observed in all regions despite differences in the regional species pool, suggesting that priority effects are likely weak and deterministic processes determine community structure despite stochasticity during early stages of community assembly.

The Effect of Light on Bacterial Activity in a Seaweed Holobiont.

Holobionts are characterized by the relationship between host and their associated organisms such as the biofilm associated with macroalgae. Considering that light is essential to macroalgae survival, the aim of this study was to verify the effect of light on the heterotrophic activity in biofilms of the brown macroalgae Sargassum furcatum during its growth cycle. Measurements of heterotrophic activity were done under natural light levels at different times during a daily cycle and under an artificial extinction of natural light during the afternoon. We also measured Sargassum primary production under these light levels in the afternoon. Both measurements were done with and without photosynthesis inhibitor and antibiotics. Biofilm composition was mainly represented by bacteria but diatoms, cyanobacteria, and other organisms were also common. When a peak of diatom genera was recorded, the heterotrophic activity of the biofilm was higher. Heterotrophic activity was usually highest during the afternoon and the presence of a photosynthesis inhibitor caused an average reduction of 17% but there was no relationship with Sargassum primary production. These results indicate that autotrophic production in the biofilm was reduced by the inhibitor with consequences on bacterial activity. Heterotrophic activity was mainly bacterial and the antibiotics chloramphenicol and penicillin were more effective than streptomycin. We suggest primary producers in the biofilm are more important to increase bacterial activity than the macroalgae itself because of coherence of the peaks of heterotrophic and autotrophic activity in biofilm during the afternoon and the effects of autotrophic inhibitors on heterotrophic activity.

Night-time lighting alters the composition of marine epifaunal communities.

Marine benthic communities face multiple anthropogenic pressures that compromise the future of some of the most biodiverse and functionally important ecosystems in the world. Yet one of the pressures these ecosystems face, night-time lighting, remains unstudied. Light is an important cue in guiding the settlement of invertebrate larvae, and altering natural regimes of nocturnal illumination could modify patterns of recruitment among sessile epifauna. We present the first evidence of night-time lighting changing the composition of temperate epifaunal marine invertebrate communities. Illuminating settlement surfaces with white light-emitting diode lighting at night, to levels experienced by these communities locally, both inhibited and encouraged the colonization of 39% of the taxa analysed, including three sessile and two mobile species. Our results indicate that ecological light pollution from coastal development, shipping and offshore infrastructure could be changing the composition of marine epifaunal communities.

Physiological response of fucoid algae to environmental stress: comparing range centre and southern populations.

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.

The role of intraspecific trait variation in driving post-metamorphic survival: Implications for recruitment in open populations.

Most ecological studies attempting to understand causes of population dynamics and community structure disregard intraspecific trait variation. We quantified the importance of natural intra-cohort variation in body size and density of juveniles for recruitment of a sessile marine organism, the barnacle Semibalanus balanoides. Barnacles are representative of species organised in metapopulations, that is, as open local populations connected by larval dispersal. We tracked the individual growth and survival of a cohort of juvenile barnacles from two shores of North Wales. Barnacles settled as larvae in spring of 2002 on previously cleared rock. The density of these new recruits was experimentally manipulated in June and randomly selected individuals were monitored from June to October to evaluate the role of barnacle size and density in predicting survival. In doing so we characterised density at three spatial scales (quadrat: 25 cm2, cells within quadrats: 25 mm2 and neighbourhood: number of neighbours in physical contact with the target barnacle). At all scales, variations in juvenile body size exacerbated the effect of density-dependent mortality on population size. While density-dependent mortality was very intense in the small-sized individuals, large-sized individuals experienced very weak density-dependent mortality and showed high survival rates. Using the concept of 'Jensen inequality', we show that important biases in estimations of survival, based on population size only, occur at high barnacle densities, where survival is low. Our study highlights the role of body size variation in understanding dynamics of open populations.

Environmental factors have stronger effects than biotic processes in patterns of intertidal populations along the southeast coast of Brazil.

Rocky shore communities are shaped by complex interactions among environmental drivers and a range of biological processes. Here, we investigated the importance of abiotic and biotic drivers on the population structure of key rocky intertidal species at 62 sites, spanning ∼50% of the Brazilian rocky shoreline (i.e., ∼500 km). Large-scale population patterns were generally explained by differences in ocean temperature and wave exposure. For the gastropod species Lottia subrugosa, differences at smaller scales (i.e., 0.1-1 km) were better explained by other abiotic influences such as freshwater discharge and substrate roughness. Based on the general population patterns of intertidal species identified, three main oceanographic groups were observed: a cold-oligotrophic grouping at northern sites (Lakes sub-region), a eutrophic group associated with large estuaries and urban zones (Santos and Guanabara bays); and a transitional warm-water group found between the two more productive areas. Larger individuals of Stramonita brasiliensis, L. subrugosa and Echinolittorina lineolata were generally found in the cold-oligotrophic system (i.e., upwelling region), while small suspension feeders dominate the warm-eutrophic systems. Evidence of bottom-up regulation was not observed, and top-down regulation effects were only observed between the whelk S. brasiliensis and its mussel prey Pernaperna. Environmental drivers as compared to biotic interactions, therefore, play a key role determining the population structure of multiple intertidal species, across a range of spatial scales along the SW Atlantic shores.

Repeatability of escape response performance in the queen scallop, Aequipecten opercularis.

In order for natural selection to operate, physiological and behavioural traits must exhibit both inter-individual variability and intra-individual consistency (i.e. repeatability) in performance. In this study, we describe individual variation and temporal repeatability in the escape responses of the queen scallop, Aequipecten opercularis, and determine whether individuals exhibited consistently high or low rankings in different aspects of the escape response. Five measures of individual performance were recorded on four occasions (days 0, 2, 7 and 28), providing proxies for sensory acuity (response latency), immediate and sustained swimming performance (burst and average clap rates), and swimming endurance (total number of claps and total time spent clapping). All components of the escape response exhibited significant inter-individual variability (all P<0.0001). Escape response latency, burst clap rate, total number of claps and total duration spent clapping maintained significant repeatability over 28 days (all P<0.016). Average clap rate was repeatable in the short term (2 days, P<0.0001) but repeatability declined by 28 days (P=0.097). Concordance analysis indicated that individuals maintained the same performance rankings over time for each component of the escape response (all P<0.001). In addition, some individuals ranked as consistently high or low performers across response latency, burst and average clap rate, and total number of claps. An individual's ability to evade predators through the provision of an escape response of an appropriate magnitude, subject to physiological, behavioural and organismal constraints, will have clear fitness-related consequences.

Impacts of artificial light at night on the early life history of two ecosystem engineers.

Sessile marine invertebrates play a vital role as ecosystem engineers and in benthic-pelagic coupling. Most benthic fauna develop through larval stages and the importance of natural light cycles for larval biology and ecology is long-established. Natural light-dark cycles regulate two of the largest ocean-scale processes that are fundamental to larvae's life cycle: the timing of broadcast spawning for successful fertilization and diel vertical migration for foraging and predator avoidance. Given the reliance on light and the ecological role of larvae, surprisingly little is known about the impacts of artificial light at night (ALAN) on the early life history of habitat-forming species. We quantified ALAN impacts on larval performance (survival, growth, development) of two cosmopolitan ecosystem engineers in temperate marine ecosystems, the mussel Mytilus edulis and the barnacle Austrominius modestus. Higher ALAN irradiance reduced survival in both species (57% and 13%, respectively). ALAN effects on development and growth were small overall, and different between species, time-points and parentage. Our results show that ALAN adversely affects larval survival and reiterates the importance of paternal influence on offspring performance. ALAN impacts on the early life stages of ecosystem engineering species have implications not only for population viability but also the ecological communities that these species support. This article is part of the theme issue 'Light pollution in complex ecological systems'.

When One Health Meets the United Nations Ocean Decade: Global Agendas as a Pathway to Promote Collaborative Interdisciplinary Research on Human-Nature Relationships.

Strong evidence shows that exposure and engagement with the natural world not only improve human wellbeing but can also help promote environmentally friendly behaviors. Human-nature relationships are at the heart of global agendas promoted by international organizations including the World Health Organization's (WHO) "One Health" and the United Nations (UN) "Ocean Decade." These agendas demand collaborative multisector interdisciplinary efforts at local, national, and global levels. However, while global agendas highlight global goals for a sustainable world, developing science that directly addresses these agendas from design through to delivery and outputs does not come without its challenges. In this article, we present the outcomes of international meetings between researchers, stakeholders, and policymakers from the United Kingdom and Brazil. We propose a model for interdisciplinary work under such global agendas, particularly the interface between One Health and the UN Ocean Decade and identify three priority research areas closely linked to each other: human-nature connection, conservation-human behavior, and implementation strategies (bringing stakeholders together). We also discuss a number of recommendations for moving forward.

Non-native marine invertebrates are more tolerant towards environmental stress than taxonomically related native species: results from a globally replicated study.

To predict the risk associated with future introductions, ecologists seek to identify traits that determine the invasiveness of species. Among numerous designated characteristics, tolerance towards environmental stress is one of the most favored. However, there is little empirical support for the assumption that non-native species generally cope better with temporarily unfavorable conditions than native species. To test this concept, we ran five pairwise comparisons between native and non-native marine invertebrates at temperate, subtropical, and tropical sites. We included (natives named first) six bivalves: Brachidontes exustus and Perna viridis, P. perna and Isognomon bicolor, Saccostrea glomerata and Crassostrea gigas, two ascidians: Diplosoma listerianum and Didemnum vexillum as well as two crustaceans: Gammarus zaddachi and G. tigrinus. We simulated acute fluctuations in salinity, oxygen concentration, and temperature, while we measured respiration and survival rates. Under stressful conditions, non-native species consistently showed less pronounced deviations from their normal respiratory performance than their native counterparts. We suggest that this indicates that they have a wider tolerance range. Furthermore, they also revealed higher survival rates under stress. Thus, stress tolerance seems to be a property of successful invaders and could therefore be a useful criterion for screening profiles and risk assessment protocols.

Larval tolerance to food limitation is stronger in an exotic barnacle than in its native competitor.

A critical question in marine ecology is understanding how organisms will cope with environmental conditions under climate change. Increasing temperatures not only have a direct effect on marine organisms but may also lead to food limitation through for example trophic mismatches, or by the increased metabolic demands imposed by developing at high temperatures. Using barnacles from a population of North Wales, we studied the combined effect of temperature and food density on the survival, settlement success, developmental time and body size of larvae of the native barnacle Semibalanus balanoides and its exotic competitor, the barnacle Austrominius modestus. Larvae were reared at similar food levels but at temperature ranges which varied among species reflecting their different phenology and tolerances. For S. balanoides (spring larval release) we used a lower temperature of 9 °C, reflecting spring temperatures from N Wales to SW England, and 15 °C representing warmer conditions; for A. modestus (summer larval release) a typical summer temperature for this geographic range of 15 °C was used with a raised temperature of 18 °C. Larvae were reared under controlled conditions in automated, computer programmable incubators and fed diatoms (Skeletonema costatum) at three food levels. We found stress effects of food limitation on larval performance of S. balanoides. While survival during naupliar development was little affected by food and temperature, low food levels strongly depressed survival and settlement during the cyprid stage of S. balanoides at both tested temperatures, but especially at 15 °C. By contrast, at the tested temperatures little effects were found on survival and settlement success in the exotic A. modestus. Both species delayed development in response to low food levels while S. balanoides cyprids showed decreased body size at the high tested temperature. The main impact occurred as a delayed effect, at the time when cyprids attempt to settle, rather than as an effect on naupliar survival or metamorphosis to the cyprid stage. Response in body size and developmental time may have costs at the time of metamorphosis (delayed settlement) or after metamorphosis. Overall, our experiments suggest that as temperature increases, settlement success of S. balanoides larvae (but not that of its competitor A. modestus) will become more sensitive to conditions of food limitation, imposed for instance by phenological mismatches with periods of phytoplankton peak.

Impacts of copper contamination on a rocky intertidal predator-prey interaction.

Metal contamination can change ecological interactions with potential effects on community dynamics. However, understanding real effects of metals on biota relies on studies undertaken in natural conditions. Through a field experiment, we investigated the effects of copper contamination on the responses of a barnacle prey and its predator, the dogwhelk, and explicitly their interaction. Contamination increased barnacle mortality and reduced predation with no effects on interaction strength. This was because the higher mortality of the prey compensated for the lower consumption of the predator. Despite not affecting the interaction strength, these results suggest a decrease in energy flow in the trophic chain that may lead to important changes in community structure and ecosystem functioning. This study shows the importance of manipulative experiments designed to provide mechanistic insights into ecological interactions to better clarify the effect of stressors on the structure and dynamic of communities.

Influence of environmental variables over multiple spatial scales on the population structure of a key marine invertebrate.

Quantifying scale-dependent patterns and linking ecological to environmental variation is required to understand mechanisms regulating biodiversity. We conducted a large-scale survey in rocky shores along the SE Brazilian coast to examine spatial variability in body size and density of an intertidal barnacle (Chthamalus bisinuatus) and its relationships with benthic and oceanographic predictors. Both the size and density of barnacles showed most variation at the smallest spatial scales. On average, barnacle body size was larger on shores located in areas characterised by higher chlorophyll levels, colder waters, low wave action and low influence of freshwater. Barnacles were more abundant at wave-exposed shores. We identified critical scales of spatial variation of an important species and linked population patterns to essential environmental predictors. Our results show that populations of this barnacle are coupled to scale-dependent oceanographic variation. This study offers insights into the mechanisms regulating coastal populations along a little studied coastline.

Metal pollution as a potential threat to shell strength and survival in marine bivalves.

Marine bivalve molluscs, such as scallops, mussels and oysters, are crucial components of coastal ecosystems, providing a range of ecosystem services, including a quarter of the world's seafood. Unfortunately, coastal marine areas often suffer from high levels of metals due to dumping and disturbance of contaminated material. We established that increased levels of metal pollution (zinc, copper and lead) in sediments near the Isle of Man, resulting from historical mining, strongly correlated with significant weakening of shell strength in king scallops, Pecten maximus. This weakness increased mortality during fishing and left individuals more exposed to predation. Comparative structural analysis revealed that shells from the contaminated area were thinner and exhibited a pronounced mineralisation disruption parallel to the shell surface within the foliated region of both the top and bottom valves. Our data suggest that these disruptions caused reduced fracture strength and hence increased mortality, even at subcritical contamination levels with respect to current international standards. This hitherto unreported effect is important since such non-apical responses rarely feed into environmental quality assessments, despite potentially significant implications for the survival of organisms exposed to contaminants. Hence our findings highlight the impact of metal pollution on shell mineralisation in bivalves and urge a reappraisal of currently accepted critical contamination levels.

Novel co-occurrence of functionally redundant consumers induced by range expansion alters community structure.

Ongoing climate change is shifting the geographic distributions of some species, potentially imposing rapid changes in local community structure and ecosystem functioning. Besides changes in population-level interspecific interactions, such range shifts may also cause changes in functional structure within the host assemblages, which can result in losses or gains in ecosystem functions. Because consumer-resource dynamics are central to community regulation, functional reorganization driven by introduction of new consumer species can have large consequences on ecosystem functions. Here we experimentally examine the extent to which the recent poleward range expansion of the intertidal grazer limpet Scurria viridula along the coast of Chile has altered the role of the resident congeneric limpet S. zebrina, and whether the net collective impacts, and functional structure, of the entire herbivore guild have been modified by the introduction of this new member. We examined the functional role of Scurria species in controlling ephemeral algal cover, bare rock availability, and species richness and diversity, and compared the effects in the region of range overlap against their respective "native" abutted ranges. Experiments showed depression of per capita effects of the range-expanded species within the region of overlap, suggesting environmental conditions negatively affect individual performance. In contrast, effects of S. zebrina were commonly invariant at its range edge. When comparing single species versus polycultures, effects on bare rock cover were altered by the presence of the other Scurria species, suggesting competition between Scurria species. Importantly, although the magnitude of S. viridula effects at the range overlap was reduced, its addition to the herbivore guild seems to complement and intensify the role of the guild in reducing green algal cover, species richness and increasing bare space provision. Our study thus highlights that range expansion of an herbivore can modify the functional guild structure in the recipient community. It also highlights the complexity of predicting how functional structure may change in the face of natural or human-induced range expansions. There is a need for more field-based examination of regional functional compensation, complementarity, or inhibition before we can construct a conceptual framework to anticipate the consequences of species range expansions.