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Shock waves are supersonic high-amplitude pressure waves that cause barotrauma when they transfer kinetic energy to the tissues of animals.1-4 Snapping shrimp (Alpheidae) produce shock waves and are exposed to them frequently, so we asked if these animals have evolved mechanisms of physical protection against them. Snapping shrimp generate shock waves by closing their snapping claws rapidly enough to form cavitation bubbles that release energy as an audible "snap" and a shock wave when they collapse.5-8 We tested if snapping shrimp are protected from shock waves by a helmet-like extension of their exoskeleton termed the orbital hood. Using behavioral trials, we found shock wave exposure slowed shelter-seeking and caused a loss of motor control in Alpheus heterochaelis from which we had removed orbital hoods but did not significantly affect behavior in shrimp with unaltered orbital hoods. Shock waves thus have the potential to harm snapping shrimp but may not do so under natural conditions because of protection provided to shrimp by their orbital hoods. Using pressure recordings, we discovered the orbital hoods of A. heterochaelis dampen shock waves. Sealing the anterior openings of orbital hoods diminished how much they altered the magnitudes of shock waves, which suggests these helmet-like structures dampen shock waves by trapping and expelling water so that kinetic energy is redirected and released away from the heads of shrimp. Our results indicate orbital hoods mitigate blast-induced neurotrauma in snapping shrimp by dampening shock waves, making them the first biological armor system known to have such a function. VIDEO ABSTRACT.
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Decápodos , Dispositivos de Protección de la Cabeza , Animales , EncéfaloRESUMEN
Salinity drops in estuaries after heavy rains are expected to increase in frequency and intensity over the next decades, with physiological and ecological consequences for the inhabitant organisms. It was investigated whether low salinity stress increases predation risk on three relevant commercial bivalves in Europe. In laboratory, juveniles of Venerupis corrugata, Cerastoderma edule, and the introduced Ruditapes philippinarum were subjected to low salinities (5, 10 and control 35) during two consecutive days and, afterwards, exposed to one of two common predators in the shellfish beds: the shore crab Carcinus maenas and the gastropod Bolinus brandaris, a non-indigenous species present in some Galician shellfish beds. Two types of choice experiment were done: one offering each predator one prey species previously exposed to one of the three salinities, and the other offering each predator the three prey species at the same time, previously exposed to one of the three salinities. Consumption of both predators and predatory behaviour of C. maenas (handling time, rejections, consumption rate) were measured. Predation rates and foraging behaviour differed, with B. brandaris being more generalist than C. maenas. Still, both predators consumed significantly more stressed (salinity 5 and 10) than non-stressed prey. The overall consumption of the native species C. edule and V. corrugata was greater than that of R. philippinarum, likely due to their vulnerability to low salinity and physical traits (e.g., thinner shell, valve gape). Increasing precipitations can alter salinity gradients in shellfish beds, and thus affect the population dynamics of harvested bivalves via predator-prey interactions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00227-021-03942-8.
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AIM: Evolutionary history of natural populations can be confounded by human intervention such as the case of decorator worm species Diopatra (Onuphidae), which have a history of being transported through anthropogenic activities. Because they build tubes and act as ecosystem engineers, they can have a large impact on the overall ecosystem in which they occur. One conspicuous member, Diopatra biscayensis, which was only described in 2012, has a fragmented distribution that includes the Bay of Biscay and the Normanno-Breton Gulf in the English Channel. This study explores the origin of these worms in the Normanno-Breton region, which has been debated to either be the result of a historic range contraction from a relic continuous population or a more recent introduction. LOCATION: Northeastern Atlantic, the Bay of Biscay, and the Normanno-Breton Gulf. METHODS: We utilized a RAD-tag-based SNP approach to create a reduced genomic data set to recover fine-scale population structure and infer which hypothesis best describes the D. biscayensis biogeographic distribution. The reduced genomic data set was used to calculate standard genetic diversities and genetic differentiation statistics, and utilized various clustering analyses, including PCAs, DAPC, and admixture. RESULTS: Clustering analyses were consistent with D. biscayensis as a single population spanning the Bay of Biscay to the Normanno-Breton Gulf in the English Channel, although unexpected genetic substructure was recovered from Arcachon Bay, in the middle of its geographic range. Consistent with a hypothesized introduction, the isolated Sainte-Anne locality in the Normanno-Breton Gulf was recovered to be a subset of the diversity found in the rest of the Bay of Biscay. MAIN CONCLUSIONS: These results are congruent with previous simulations that did not support connectivity from the Bay of Biscay to the Normanno-Breton Gulf by natural dispersal. These genomic findings, with support from previous climatic studies, further support the hypothesis that D. biscayensis phylogeographic connectivity is the result of introductions, likely through the regions' rich shellfish aquaculture, and not of a historically held range contraction.
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Heat waves are expected to increase in duration and frequency, impacting coastal ecosystems, especially intertidal organisms living near their thermal tolerance limits. Sedentary infaunal species are limited to some extent in escapes from sudden temperature changes, rather modifications to their physiology and behaviour are expected. This may lead to strong ecological and economic impacts on commercial bivalve species, such as Venerupis corrugata, Ruditapes decussatus, the introduced Ruditapes philippinarum and Cerastoderma edule, the most relevant in NW Spain. We investigated lethal and sublethal effects of heat during low tide on these species in the laboratory. Summer temperatures experienced within field, shallow sediments at approximately 2 cm depth i.e. 20 °C (control), 27 °C, 32 °C, and 37 °C, were replicated during four consecutive days and the diffusion of heat at the burrowing depth of each species was estimated; temperature exposure was expressed as degree hours above 22 °C. After two days of tidal exposure, C. edule and V. corrugata suffered significant mortalities, and also the most dramatic decrease in scope for growth (SFG) as well as reduction in burrowing activity. After four days under stress, all species had negative SFG. On recovery, species showed compensation at longer exposures, particularly C. edule. These effects of temperature on mortality, growth potential and burrowing ability may increase the time to achieve commercial size and exposure to predation. Particularly, V. corrugata, with a center of distribution lower in the intertidal and subtidal, and C. edule, shallower in the sediment, may be the most affected. Clearly the intensity and frequency of heat waves will affect these key species in the intertidal sediment flats changing ecosystem functioning and fisheries management strategies.
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Bivalvos , Cardiidae , Animales , Ecosistema , Calor , EspañaRESUMEN
Range shifts due to annual variation in temperature are more tractable than range shifts linked to decadal to century long temperature changes due to climate change, providing natural experiments to determine the mechanisms responsible for driving long-term distributional shifts. In this study we couple physiologically grounded mechanistic models with biogeographic surveys in 2 years with high levels of annual temperature variation to disentangle the drivers of a historical range shift driven by climate change. The distribution of the barnacle Semibalanus balanoides has shifted 350 km poleward in the past half century along the east coast of the United States. Recruits were present throughout the historical range following the 2015 reproductive season, when temperatures were similar to those in the past century, and absent following the 2016 reproductive season when temperatures were warmer than they have been since 1870, the earliest date for temperature records. Our dispersal dependent mechanistic models of reproductive success were highly accurate and predicted patterns of reproduction success documented in field surveys throughout the historical range in 2015 and 2016. Our mechanistic models of reproductive success not only predicted recruitment dynamics near the range edge but also predicted interior range fragmentation in a number of years between 1870 and 2016. All recruits monitored within the historical range following the 2015 colonization died before 2016 suggesting juvenile survival was likely the primary driver of the historical range retraction. However, if 2016 is indicative of future temperatures mechanisms of range limitation will shift and reproductive failure will lead to further range retraction in the future. Mechanistic models are necessary for accurately predicting the effects of climate change on ranges of species.
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Distribución Animal , Cambio Climático , Thoracica/fisiología , Animales , Reproducción , Estaciones del Año , TemperaturaRESUMEN
Estuarine bivalves are especially susceptible to salinity fluctuations. Stage-specific sensibilities may influence the structure and spatial distribution of the populations. Here we investigate differences on the energetic strategy of thread drifters (3-4 mm) and sedentary settlers (9-10 mm) of Cerastoderma edule over a wide range of salinities. Several physiological indicators (clearance, respiration and excretion rates, O:N) were measured during acute (2 days) and acclimated responses (7 days of exposure) for both size classes. Our results revealed a common lethal limit for both developmental stages (Salinity 15) but a larger physiological plasticity of thread drifters than sedentary settlers. Acclimation processes in drifters were initiated after 2 days of exposure and they achieved complete acclimation by day 7. Sedentary settlers delay acclimation and at day 7 feeding activity had not resumed and energetic losses through respiration and excretion were higher at the lowest salinity treatment. Different responses facing salinity stress might be related to differences in habitat of each stage. For sedentary settlers which occupy relatively stable niches, energy optimisation include delaying the initiation of the energetically expensive acclimation processes while drifters which occupy less stable environments require a more flexible process which allow them to optimize energy acquisition as fast as possible.
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Models of ecological responses to climate change fundamentally assume that predictor variables, which are often measured at large scales, are to some degree diagnostic of the smaller-scale biological processes that ultimately drive patterns of abundance and distribution. Given that organisms respond physiologically to stressors, such as temperature, in highly non-linear ways, small modelling errors in predictor variables can potentially result in failures to predict mortality or severe stress, especially if an organism exists near its physiological limits. As a result, a central challenge facing ecologists, particularly those attempting to forecast future responses to environmental change, is how to develop metrics of forecast model skill (the ability of a model to predict defined events) that are biologically meaningful and reflective of underlying processes. We quantified the skill of four simple models of body temperature (a primary determinant of physiological stress) of an intertidal mussel, Mytilus californianus, using common metrics of model performance, such as root mean square error, as well as forecast verification skill scores developed by the meteorological community. We used a physiologically grounded framework to assess each model's ability to predict optimal, sub-optimal, sub-lethal and lethal physiological responses. Models diverged in their ability to predict different levels of physiological stress when evaluated using skill scores, even though common metrics, such as root mean square error, indicated similar accuracy overall. Results from this study emphasize the importance of grounding assessments of model skill in the context of an organism's physiology and, especially, of considering the implications of false-positive and false-negative errors when forecasting the ecological effects of environmental change.
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Seafloor biodiversity is a key mediator of ecosystem functioning, but its role is often excluded from global budgets or simplified to black boxes in models. New techniques allow quantification of the behavior of animals living below the sediment surface and assessment of the ecosystem consequences of complex interactions, yielding a better understanding of the role of seafloor animals in affecting key processes like primary productivity. Combining predictions based on natural history, behavior of key benthic species and environmental context allow assessment of differences in functioning and process, even when the measured ecosystem property in different systems is similar. Data from three sedimentary systems in New Zealand illustrate this. Analysis of the behaviors of the infaunal ecosystem engineers in each system revealed three very different mechanisms driving ecosystem function: density and excretion, sediment turnover and surface rugosity, and hydraulic activities and porewater bioadvection. Integrative metrics of ecosystem function in some cases differentiate among the systems (gross primary production) and in others do not (photosynthetic efficiency). Analyses based on behaviors and activities revealed important ecosystem functional differences and can dramatically improve our ability to model the impact of stressors on ecosystem and global processes.
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Organismos Acuáticos/fisiología , Ecosistema , Modelos Biológicos , Nueva ZelandaRESUMEN
As climate change is expected to impose increasing thermal stress on intertidal organisms, understanding the mechanisms by which body temperatures translate into major biogeographic patterns is of paramount importance. We exposed individuals of the limpet Patella vulgata Linnaeus, 1758, to realistic experimental treatments aimed at disentangling the contribution of water and air temperature for the buildup of thermal stress. Treatments were designed based on temperature data collected at the microhabitat level, from 15 shores along the Atlantic European coast spanning nearly 20° of latitude. Cardiac activity data indicated that thermal stress levels in P. vulgata are directly linked to elevated water temperature, while high air temperature is only stressful if water temperature is also high. In addition, the analysis of the link between population densities and thermal regimes at the studied locations suggests that the occurrence of elevated water temperature may represent a threshold P. vulgata is unable to tolerate. By combining projected temperatures with the temperature threshold identified, we show that climate change will likely result in the westward expansion of the historical distribution gap in the Bay of Biscay (southwest France), and northward contraction of the southern range limit in south Portugal. These findings suggest that even a minor relaxing of the upwelling off northwest Iberia could lead to a dramatic increase in thermal stress, with major consequences for the structure and functioning of the intertidal communities along Iberian rocky shores.
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Cambio Climático , Temperatura , Aire , Animales , Océanos y MaresRESUMEN
This study examines the importance of thermal refugia along the majority of the geographical range of a key intertidal species (Patella vulgata Linnaeus, 1758) on the Atlantic coast of Europe. We asked whether differences between sun-exposed and shaded microhabitats were responsible for differences in physiological stress and ecological performance and examined the availability of refugia near equatorial range limits. Thermal differences between sun-exposed and shaded microhabitats are consistently associated with differences in physiological performance, and the frequency of occurrence of high temperatures is most probably limiting the maximum population densities supported at any given place. Topographical complexity provides thermal refugia throughout most of the distribution range, although towards the equatorial edges the magnitude of the amelioration provided by shaded microhabitats is largely reduced. Importantly, the limiting effects of temperature, rather than being related to latitude, seem to be tightly associated with microsite variability, which therefore is likely to have profound effects on the way local populations (and consequently species) respond to climatic changes.
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Gastrópodos/fisiología , Refugio de Fauna , Temperatura , Animales , Océano Atlántico , Temperatura Corporal , Ecosistema , Europa (Continente) , Geografía , Proteínas HSP70 de Choque Térmico/análisis , Estrés Fisiológico , Luz SolarRESUMEN
Extreme heat events cause patchy mortality in many habitats. We examine biophysical mechanisms responsible for patchy mortality in beds of the competitively dominant ecosystem engineer, the marine mussel Mytilus californianus, on the west coast of the United States. We used a biophysical model to predict daily fluctuations in body temperature at sites from southern California to Washington and used results of laboratory experiments on thermal tolerance to determine mortality rates from body temperature. In our model, we varied the rate of thermal conduction within mussel beds and found that this factor can account for large differences in body temperature and consequent mortality during heat waves. Mussel beds provide structural habitat for other species and increase local biodiversity, but, as sessile organisms, they are particularly vulnerable to extreme weather conditions. Identifying critical biophysical mechanisms related to mortality and ecological performance will improve our ability to predict the effects of climate change on these vulnerable ecosystems.
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Calor/efectos adversos , Modelos Biológicos , Mytilus/fisiología , Animales , Cambio Climático , Ecosistema , Océanos y Mares , Estrés Fisiológico , Olas de MareaRESUMEN
We used hyperspectral imaging to study short-term effects of bioturbation by lugworms (Arenicola marina) on the surficial biomass of microphytobenthos (MPB) in permeable marine sediments. Within days to weeks after the addition of a lugworm to a homogenized and recomposed sediment, the average surficial MPB biomass and its spatial heterogeneity were, respectively, 150-250% and 280% higher than in sediments without lugworms. The surficial sediment area impacted by a single medium-sized lugworm (~4 g wet weight) over this time-scale was at least 340 cm2. While sediment reworking was the primary cause of the increased spatial heterogeneity, experiments with lugworm-mimics together with modeling showed that bioadvective porewater transport from depth to the sediment surface, as induced by the lugworm ventilating its burrow, was the main cause of the increased surficial MPB biomass. Although direct measurements of nutrient fluxes are lacking, our present data show that enhanced advective supply of nutrients from deeper sediment layers induced by faunal ventilation is an important mechanism that fuels high primary productivity at the surface of permeable sediments even though these systems are generally characterized by low standing stocks of nutrients and organic material.
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Sedimentos Geológicos , Poliquetos/fisiología , Animales , Biomasa , Modelos Teóricos , AguaRESUMEN
Predicting the extent and direction of species' range shifts is a major priority for scientists and resource managers. Seminal studies have fostered the notion that biological systems responding to climate change-impacted variables (e.g., temperature, precipitation) should exhibit poleward range shifts but shifts contrary to that expectation have been frequently reported. Understanding whether those shifts are indeed contrary to climate change predictions involves understanding the most basic mechanisms determining the distribution of species. We assessed the patterns of ecologically relevant temperature metrics (e.g., daily range, min, max) along the European Atlantic coast. Temperature metrics have contrasting geographical patterns and latitude or the grand mean are poor predictors for many of them. Our data suggest that unless the appropriate metrics are analysed, the impact of climate change in even a single metric of a single stressor may lead to range shifts in directions that would otherwise be classified as "contrary to prediction".
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Cambio Climático , Ecosistema , Modelos BiológicosRESUMEN
We present a Dynamic Energy Budget (DEB) model for the quintessential keystone predator, the rocky-intertidal sea star Pisaster ochraceus. Based on first principles, DEB theory is used to illuminate underlying physiological processes (maintenance, growth, development, and reproduction), thus providing a framework to predict individual-level responses to environmental change. We parameterized the model for P. ochraceus using both data from the literature and experiments conducted specifically for the DEB framework. We devoted special attention to the model's capacity to (1) describe growth trajectories at different life-stages, including pelagic larval and post-metamorphic phases, (2) simulate shrinkage when prey availability is insufficient to meet maintenance requirements, and (3) deal with the combined effects of changing body temperature and food supply. We further validated the model using an independent growth data set. Using standard statistics to compare model outputs with real data (e.g. Mean Absolute Percent Error, MAPE) we demonstrated that the model is capable of tracking P. ochraceus' growth in length at different life-stages (larvae: MAPEâ=â12.27%; post-metamorphic, MAPEâ=â9.22%), as well as quantifying reproductive output index. However, the model's skill dropped when trying to predict changes in body mass (MAPEâ=â24.59%), potentially because of the challenge of precisely anticipating spawning events. Interestingly, the model revealed that P. ochraceus reserves contribute little to total biomass, suggesting that animals draw energy from structure when food is limited. The latter appears to drive indeterminate growth dynamics in P. ochraceus. Individual-based mechanistic models, which can illuminate underlying physiological responses, offer a viable framework for forecasting population dynamics in the keystone predator Pisaster ochraceus. The DEB model herein represents a critical step in that direction, especially in a period of increased anthropogenic pressure on natural systems and an observed recent decline in populations of this keystone species.
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Metabolismo Energético/fisiología , Modelos Biológicos , Reproducción/fisiología , Estrellas de Mar/fisiología , Animales , Biomasa , Abastecimiento de Alimentos , Dinámica PoblacionalRESUMEN
Thresholds profoundly affect our understanding and management of ecosystem dynamics, but we have yet to develop practical techniques to assess the risk that thresholds will be crossed. Combining ecological knowledge of critical system interdependencies with a large-scale experiment, we tested for breaks in the ecosystem interaction network to identify threshold potential in real-world ecosystem dynamics. Our experiment with the bivalves Macomona liliana and Austrovenus stutchburyi on marine sandflats in New Zealand demonstrated that reductions in incident sunlight changed the interaction network between sediment biogeochemical fluxes, productivity, and macrofauna. By demonstrating loss of positive feedbacks and changes in the architecture of the network, we provide mechanistic evidence that stressors lead to break points in dynamics, which theory predicts predispose a system to a critical transition.
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Bivalvos/fisiología , Ecosistema , Animales , Modelos Biológicos , Nueva Zelanda , Océanos y MaresRESUMEN
Intertidal populations of the ecosystem engineering polychaete, Diopatra biscayensis, were analyzed on the French Atlantic coast for three years with individual size estimated from tube-cap aperture. All but the northernmost population along the Bay of Biscay have yearly recruitment. Individuals live 3-5 years and are likely reproductive as one year olds. Simulations indicate dispersal distances are <50 km; yet, populations also exist within the Normano-Breton Gulf in the western English Channel, more than 450 km from the northernmost Bay of Biscay population at La Trinité-sur-Mer. Three of the four populations in the Normano-Breton Gulf have no young of the year, but are near to active mussel culture where mussel seed is transported on ropes from dense D. biscayensis areas in the Vendée-Charente region in the Bay of Biscay. The majority of D. biscayensis were adjacent to the likely source, mussel seed ropes. Transport assisted by aquaculture is the likely explanation for the populations in the Normano-Breton Gulf.
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Poliquetos/fisiología , Migración Animal , Animales , Acuicultura , Océano Atlántico , Tamaño Corporal , Simulación por Computador , Ecosistema , Francia , Larva , Poliquetos/crecimiento & desarrollo , Densidad de Población , Dinámica PoblacionalRESUMEN
Modeling the biogeographic consequences of climate change requires confidence in model predictions under novel conditions. However, models often fail when extended to new locales, and such instances have been used as evidence of a change in physiological tolerance, that is, a fundamental niche shift. We explore an alternative explanation and propose a method for predicting the likelihood of failure based on physiological performance curves and environmental variance in the original and new environments. We define the transient event margin (TEM) as the gap between energetic performance failure, defined as CTmax, and the upper lethal limit, defined as LTmax. If TEM is large relative to environmental fluctuations, models will likely fail in new locales. If TEM is small relative to environmental fluctuations, models are likely to be robust for new locales, even when mechanism is unknown. Using temperature, we predict when biogeographic models are likely to fail and illustrate this with a case study. We suggest that failure is predictable from an understanding of how climate drives nonlethal physiological responses, but for many species such data have not been collected. Successful biogeographic forecasting thus depends on understanding when the mechanisms limiting distribution of a species will differ among geographic regions, or at different times, resulting in realized niche shifts. TEM allows prediction of the likelihood of such model failure.
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Understanding and forecasting current and future consequences of coastal warming require a fine-scale assessment of the near-shore temperature changes. Here we show that despite the fact that 71% of the world's coastlines are significantly warming, rates of change have been highly heterogeneous both spatially and seasonally. We demonstrate that 46% of the coastlines have experienced a significant decrease in the frequency of extremely cold events, while extremely hot days are becoming more common in 38% of the area. Also, we show that the onset of the warm season is significantly advancing earlier in the year in 36% of the temperate coastal regions. More importantly, it is now possible to analyse local patterns within the global context, which is useful for a broad array of scientific fields, policy makers and general public.
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Cambio Climático , Conservación de los Recursos Naturales , Ecosistema , Política Pública , Agua de Mar , Organismos Acuáticos , Predicción , Calentamiento Global , Calor , Océanos y Mares , Estaciones del Año , Tiempo (Meteorología)RESUMEN
Gridded weather data were evaluated as sources of forcing variables for biophysical models of intertidal animal body temperature with model results obtained using local weather station data serving as the baseline of comparison. The objective of the study was to determine which gridded data are sufficient to capture observed patterns of thermal stress. Three coastal sites in western North America were included in this analysis: Boiler Bay, Oregon; Bodega Bay, California; and Pacific Grove, California. The gridded data with the highest spatial resolution, the 32-km North American Regional Reanalysis (NARR) and the 38-km Climate Forecasting System Reanalysis (CFSR), predicted daily maximum intertidal animal temperature most similarly to the local weather Station data. Time step size was important for variables that change rapidly throughout the day, such as solar radiation. There were site-based differences in the ability of the model to predict daily maximum intertidal animal temperature, with the gridded data predictions being the closest to local weather station predictions in Boiler Bay, Oregon. In a review of gridded data used as part of ecological studies, there was broad use of the data across subject areas and ecosystems so the recent improvements in the spatial (from 2 degrees to 32 km) and temporal scales (from 6 hours to 1 hour) of gridded data will further add to the applicability within the ecological community particularly for mechanistic studies.
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Ecosistema , Monitoreo del Ambiente/métodos , Tiempo (Meteorología) , Animales , Bivalvos/fisiología , California , Océanos y Mares , Oregon , Temperatura , Factores de TiempoRESUMEN
Biogenic forces alter sediment characteristics along several axes with important consequences for structure of benthic communities. The usual axes discussed are those of sediment stabilization versus resuspension and mobile versus temporally persistent organisms. A third axis of bioadvection is typically subsumed within the others. Here we argue that given the complex fluid dynamics resulting from the bidirectional forces that organisms exert on porewater, bioadvection needs to be examined separately. The probable major players in generation of bioadvection are described with impacts on transport both of materials and heat. Illustrations are given of the bidirectionality of bioadvection and the resultant changes in oxygenation either surficially or at depth, as well as of heat transport both laterally within the sediment and vertically.