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This article discusses the mass disappearance of intertidal mussels in eastern Canada after an unusual winter cold snap in February 2023. The decline in mussel abundance is concerning due to its impact on coastal biodiversity. The cold snap, which saw temperatures drop below -20°C, is believed to be the main driver of the mass disappearance. Other factors such as predation, ice scour, and wave action were ruled out as causes. The article highlights the potential implications of climate change on the future of coastal ecosystems and emphasizes the need to study the frequency of extreme weather events. [Extracted from the article]

Further isolation may arise through site-specific co-evolution between the mussels and hosts; Douda et al. ([7]) demonstrated that there are often differences in the suite of fish hosts used by I U. crassus i , even across genetically and geographically close populations. Keywords: conservation; glochidia; host specificity; parasitism; reproduction EN conservation glochidia host specificity parasitism reproduction 1 5 5 05/03/23 20230501 NES 230501 Understanding the life-history characteristics of endangered species is crucial to their conservation, management, and predicting their responses to environmental change (Stark et al., [16]). Fishing for hosts: Larval spurting by the endangered thick-shelled river mussel, Uniocrassus Host specificity can increase vulnerability of mussels as survival is intrinsically linked to that of their hosts. [Extracted from the article]

Under climate change, marine organisms will need to tolerate or adapt to increasing temperatures to persist. The ability of populations to cope with thermal stress may be influenced by conditions experienced by parents, by both genetic changes and transgenerational phenotypic plasticity through epigenetics or maternal provisioning. In organisms with complex life cycles, larval stages are particularly vulnerable to stress. Positive parental carry‐over effects occur if more stressful parental environments yield more tolerant offspring while the opposite pattern leads to negative carry‐over effects. This study evaluated the role of parental effects in determining larval thermal tolerances for the intertidal mussel, Mytilus californianus. We tested whether thermal environments across a natural gradient (shoreline elevation) impacted mussel temperature tolerances. Lethal thermal limits were compared for field‐collected adults and their larvae. We observed parental effects across one generation, in which adult mussels exposed to warmer habitats yielded less tolerant offspring. Interestingly, although parental environments influenced offspring tolerances, we found no clear effects of habitat conditions on adult phenotypes (tolerances). We found indicators of trade‐offs in energy investment, with higher reproductive condition and larger egg diameters in low stress environments. These results suggest that parental effects are negative, leading to possible adverse effects of thermal stress on the next generation. [ABSTRACT FROM AUTHOR]

COVER PHOTO: Biogenic habitats host much of global biodiversity. Many, like these mussel beds (Bodega Marine Reserve, California, USA) can also buffer climate‐related stresses. Jurgens et al. (this issue; Article e03596; doi:10.1002/ecy.3596) demonstrate how physical facilitation by these habitat‐forming species can dramatically alter climate change predictions for inhabitants. Photo credit: Laura Jurgens. [ABSTRACT FROM AUTHOR]

Mussel beds and rockweed stands (fucoid algae) have been shown to be alternative states on rocky intertidal shores in New England, and here the hypothesis that variation in recruitment provides opportunity for the development of alternative community states was tested. Disturbance by ice scour opens patches for development of alternative states, and in winter 1996-1997, 60 experimental clearings of differing sizes were established on Swan's Island, Maine, USA. Half of the plots were re-cleared during the winter of 2010-2011. Recruitment data for barnacles, mussels, and fucoid algae collected from 1997 to 2012 were used to (1) test for persistence of scale-dependent thresholds, (2) estimate the magnitudes and sources of variation, (3) fit a surface of alternative states as defined by the cusp catastrophe, and (4) test if 1997 recruitment would predict 2010-2011 recruitment in re-scraped plots (i.e., a test of divergence, which is expected in systems with alternative states). For barnacles and mussels, recruitment varied enormously year to year and among sites, but showed consistent patterns over the long-term with respect to clearing size. Average recruitment prior to re-clearing was a good predictor of recruitment afterwards. In contrast, over 50% of the variance in fucoid recruitment was unexplained with weak effects among years and locations. Past fucoid recruitment was a poor predictor of subsequent recruitment. The cusp analysis indicated that fucoid recruitment defines the alternative states. Fucoid recruitment was largely unpredictable and suggests long-term, small-scale priority effects drive the development of alternative states. These observations strongly reinforce the notion that long-term and well-replicated experiments are necessary to develop robust tests of ecological theory. [ABSTRACT FROM AUTHOR]

Because many marine invertebrates have a dispersive planktonic phase, the spatial scale of demographic connectivity among local populations remains a key, but elusive, parameter driving population and metapopulation dynamics. However, temporal variation in the scale of connectivity remains largely undocumented, despite its recognized importance for predicting population responses to environmental changes. To assess the temporal stability of metapopulation connectivity, we conducted a large-scale survey of a blue mussel (Mytilus spp.) metapopulation for five years along a 100-km section of coastline of the Gaspé Peninsula, Québec, Canada. For each year, we estimated the scale of demographic coupling among 27-29 sites within our study region, using the spatial cross-covariance between adult abundance and recruit density across sites. Despite large interannual variability in overall recruit abundance, our analysis revealed stationary spatial distributions of adult and recruit abundance. More importantly, our analysis revealed a consistent demographic coupling among populations at a distance ranging from 12 to 24 km in all but one of the five years studied. The scale of connectivity in this system is thus temporally stable, but can occasionally show irregular fluctuations, and our results provide evidence in support of the integration of time-varying connectivity to marine metapopulation and reserve network theories. [ABSTRACT FROM AUTHOR]

Ecological theory predicts that invasive prey can interact with native prey directly by competing for shared resources or indirectly by changing the abundance or behavior of shared native predators. However, both the study and management of invasive prey have historically overlooked indirect effects. In southern California estuaries, introduction of the Asian nest mussel Arcuatula senhousia has been linked to profound changes in native bivalve assemblages, but the mechanisms of these interactions remain unclear. We performed three field experiments to assess the mechanisms of competition between Arcuatula and native bivalves, and evaluated the potential for Arcuatula to indirectly mediate native predator-prey dynamics. We found that Arcuatula reduces the diversity, abundance, and size of native bivalve recruits by preemptively exploiting space in surface sediments. When paired with native shallow-dwelling clams (Chione undatella and Laevicardium substriatum), Arcuatula reduces adult survival through overgrowth competition. However, Arcuatula also attracts native predators, causing apparent competition by indirectly increasing predation of native clams, especially for poorly defended species. Therefore, invasive prey can indirectly increase predation rates on native competitors by changing the behavior of shared native predators, but the magnitude of apparent competition strongly depends on the vulnerability of natives to predation. Interestingly, our results indicate that the vulnerability of invasive prey to predation can greatly exacerbate impacts on their native competitors. Our findings suggest that consideration of both direct and indirect effects of invasive prey, as well as native predator-prey relationships, should lead to more effective invasive species management. [ABSTRACT FROM AUTHOR]

Most sedentary marine animals disperse from their place of origin during their initial life stages as larvae. The delivery of planktonic larvae back to coastal adult habitats after weeks or months of offshore development is commonly thought to be stochastic, resulting in large recruitment fluctuations and making predictive understanding of population dynamics difficult. Time series of invertebrate settlement on intertidal shores have been used to infer how various oceanographic processes deliver planktonic larvae ashore. However, the possibility that successful settlement may involve a series of different transport mechanisms, which are sequentially utilized by late-stage larvae, has received little attention. To address this, we monitored both the delivery of mussel and barnacle larvae to inner-shelf moorings positioned 200-1400 m from the shore, and larval settlement in the intertidal adult habitat, at two contrasting sites: a headland forming an upwelling center and a downstream bay. Model selection was employed to determine the most likely scenario(s) of larval onshore transport from four a priori transport mechanisms individually and in combination: (1) upwelling or relaxation/downwelling, (2) tidal motions, (3) diurnal sea breezes, and (4) surface waves. Mussel larvae were delivered to the inner shelf during upwelling in the bay, but during downwelling at the headland, and were further transported to the shore by surface waves at both locales. In contrast, the delivery of barnacle larvae to the inner shelf occurred during relaxation/downwelling events at both sites, and intertidal settlement coincided with spring tides, suggesting a role for internal tides in their onshore transport. Thus, sequential mechanisms appear to be utilized by larvae to get to the shore, involving interactions of regional-scale upwelling/downwelling processes and local-scale tidal and surface-wave processes, which differ among taxa and among sites with different topography. A bottleneck for larval delivery across the surf zone may be a result of out-of-phase steps in sequential transport mechanisms leaving larvae lost "in transit." [ABSTRACT FROM AUTHOR]

Riparian habitats provide detrital subsidies of varying quantities and qualities to recipient ecosystems. We used long-term data from three reference streams (covering 24 stream-years) and 13-year whole-stream organic matter manipulations to investigate the influence of terrestrial detrital quantity and quality on benthic invertebrate community structure, abundance, biomass, and secondary production in rockface (RF) and mixed substrates (MS) of forested headwater streams. Using a mesh canopy covering the entire treatment stream, we examined effects of litter exclusion, small- and large-wood removal, and addition of artificial wood (PVC) and leaves of varying quality on organic matter standing crops and invertebrate community structure and function. We assessed differences in functional feeding group distribution between substrate types as influenced by organic matter manipulations and long-term patterns of predator and prey production in manipulated vs. reference years. Particulate organic matter standing crops in MS of the treatment stream declined drastically with each successive year of litter exclusion, approaching zero after three years. Monthly invertebrate biomass and annual secondary production was positively related to benthic organic matter in the MS habitats. Rockface habitats exhibited fewer changes than MS habitats across all organic matter manipulations. With leaf addition, the patterns of functional group distribution among MS and RF habitats returned to patterns seen in reference streams. Secondary production per unit organic matter standing crop was greatest for the leaf addition period, followed by the reference streams, and significantly less for the litter exclusion and wood removal periods. These data indicate that the limited organic matter remaining in the stream following litter exclusion and wood removal was more refractory than that in the reference streams, whereas the added leaf material was more labile and readily converted into invertebrate production. Predator production and total production were tightly coupled in reference and treatment streams, indicating strong relationships between predators and their prey. Results from the artificial wood addition demonstrate that physical structure alone will not restore invertebrate productivity without detrital resources from the riparian forest. Our long-term studies conducted over three decades at the ecosystem scale unequivocally show the necessity of maintaining and restoring aquatic-terrestrial linkages in forested headwater streams. [ABSTRACT FROM AUTHOR]

Increasing evidence shows that spatial interactions between sedentary organisms can structure communities and promote landscape complexity in many ecosystems. Here we tested the hypothesis that reef-forming mussels (Mytilus edulis L.), a dominant intertidal ecosystem engineer in the Wadden Sea, promote abundances of the burrowing bivalve Cerastoderma edule L. (cockle) in neighboring habitats at relatively long distances coastward from mussel beds. Field surveys within and around three mussel beds showed a peak in cockle densities at 50-100 m toward the coast from the mussel bed, while cockle abundances elsewhere in the study area were very low. Field transplantation of cockles showed higher survival of young cockles (2-3 years old) and increased spat fall coastward of the mussel bed compared to within the bed and to areas without mussels, whereas growth decreased within and coastward of the mussel bed. Our measurements suggest that the observed spatial patterns in cockle numbers resulted from (1) inhibition effects by the mussels close to the beds due to preemptive algal depletion and deteriorated sediment conditions and (2) facilitation effects by the mussels farther away from the beds due to reduction of wave energy. Our results imply that these spatial, scale-dependent interactions between reef-forming ecosystem engineers and surrounding communities of sedentary benthic organisms can be an important determinant of the large-scale community structure in intertidal ecosystems. Understanding this interplay between neighboring communities of sedentary species is therefore essential for effective conservation and restoration of soft-bottom intertidal communities. [ABSTRACT FROM AUTHOR]

We considered Cushing's match/mismatch theory in a heterotrophic environment and hypothesized that settlement and recruitment success in blue mussel are higher when the food supply is rich in polyunsaturated and essential fatty acids (PUFA/EFA). To test this hypothesis, we monitored larval development as well as fatty acid composition in trophic resources during two successive reproductive seasons. The decoupling we found between the presence of competent larvae in the water column and settlement rates strongly suggests that metamorphosis is delayed until conditions are suitable. In both years, the major mussel settlement peak was synchronized with a phytoplanktonic pulse rich in EFA, consisting of a large autotrophic bloom in 2007 and a short but substantial peak of picoeukaryotes in 2008. These results suggest a "trophic settlement trigger" that indirectly affects recruitment by strongly improving the settlement rate. Despite similar larval settlement rates during both years, the lower 2007 recruitment likely resulted from a mismatch with a high lipid-quality trophic resource. The seasonal trophic conditions differed greatly between the two years, with fatty acids profiles reflecting heterotrophic plankton production in 2007 and mostly autotrophic production in 2008. In agreement with Cushing's theory, our results highlight a match/mismatch, related to the food lipid quality rather than food quantity. For the first time, we show that the recruitment in marine bivalves may be dependent on phytoplanktonic pulses characterized by high levels of PUFA. [ABSTRACT FROM AUTHOR]

Ecologists still have to elucidate the complex feedback interactions operating among biodiversity and ecosystem processes in engineered systems. To address this, a field experiment was conducted to mimic natural mussel bed meta-ecosystems (Mytilus spp.) of the lower St. Lawrence Estuary (Quebec, Canada) and partition the effects of their biotic and abiotic properties and spatial structure on ecosystem processes and community dynamics of associated macro-invertebrates. We found positive intraspecific feedbacks between mussels and their recruits, and negative interspecific feedbacks between mussels and their associated ecosystem. These feedbacks were associated with mussel bed ecosystem processes (fluxes of ammonium and oxygen). In addition, we showed that proximity between mussel patches increased within-patch nutrient fluxes. Our study revealed the potential for meta-ecosystem engineering to drive feedback interactions between community and ecosystem functioning in marine fragmented systems. It also shows the relevance of meta-ecosystem theories as a conceptual framework to elucidate biotic and abiotic processes controlling ecosystem and community structure. Such framework could contribute to ecosystem-based management of spatially structured systems such as reserve networks and fragmented ecosystems. [ABSTRACT FROM AUTHOR]

Temperature and primary production (often linked to nutrient supply) are two of the few factors influencing species diversity and abundances across mesoscale gradients, while at smaller scales the habitat complexity offered by bioengineers is important. Previous studies have illustrated effects of upwelling and biogeography on intertidal bioengineers, but it is not known if these proëesses influence assemblages associated with those bioengineers in a similar way. We examined the habitat structure offered by two species of mussels and their associated fauna in five regions across 3000 km and three biogeographic provinces of the South African coast, replicating upwelling and. non-upwelling areas within each region. Upwelling and region influenced the structure of mussel beds (the density and size of mussels). In contrast, upwelling did not influence mesoscale differences in composition, abundance, .and numbers of species of crustaceans, mollusks, or polychaetes in mussel beds. Regardless of trophic level or mode of reproduction, mussel bed fauna were influenced only by region. Regional differences were strongly influenced by biogeography. The associated fauna was, however, also strongly correlated with the structure of the habitats created by mussels. Our results support the importance of upwilling to a critical ecosystem engineer, but show that these effects do not extend directly to the assemblages of associated fauna, which are more influenced by regional-scale effects and biogeography. We suggest that mesoscale patterns in the associated fauna of this bioengineered habitat are driven by the direct effects of biogeography, combined with the influence of biogeography and upwelling on mussel bed structure. [ABSTRACT FROM AUTHOR]

Stationary boundaries of sedentary species may belie dynamic processes that form them. Our aim was to test an implication of an evolving body of theory, that such boundaries are manifestations of complex regulatory dynamics. On rocky shores of British Columbia, large-scale field experiments altered the densities of predatory sea stars (Pisaster ochraceus), causing shifts in the location of the lower vertical boundaries of their prey, sea mussels (Mytilus californianus). While control mussel beds remained unchanged, experimental reductions of sea star densities caused the downward extension of the lower boundaries, and experimental increases in sea stars densities caused the upward recession of the lower boundary well into the zone presumed to be a spatial refuge from predation. Cleared plots prepared within the initial boundaries were recolonized to varying degrees, depending on predator densities. After 30 months, plots on sea star removal sites showed high densities of adult mussels, control plots showed intermediate densities, and sea star addition plots showed only a sparse cover of alternative prey. Observations by divers at high tide showed that as small prey were depleted progressively from removal, to control, to addition sites, correspondingly larger mussels were attacked, including very large individuals comprising the lower boundary of addition sites. The findings contradict classic theory of zonation based on static prey refuges and support an alternative theory in which boundaries are maintained by complex, spatially structured equilibria. [ABSTRACT FROM AUTHOR]

It is well established that predators can scare as well as consume their prey. In many systems, the fear of being eaten causes trait-mediated cascades whose strength can rival or exceed that of more widely recognized density-mediated cascades transmitted by predators that consume their prey. Despite this progress it is only beginning to be understood how the influence of predation risk is shaped by environmental context and whether it can exert an important influence on ecosystem-level processes. This study used a factorial mesocosm experiment that manipulated basal-resource identity (either barnacles, Seinibalanus balanoides, or mussels, Mytilus edulis) to determine how resources modify the influence of predation. risk, cascade strength, and the efficiency of energy transfer in two, tritrophic, rocky-shore food chains containing the predatory green crab (Carcinus inaenas) and an intermediate consumer (the snail, Nucella lapillus). The effect of predation risk and the strength of trait-mediated cascades (both in absolute and relative terms) were much stronger in the barnacle than in the mussel food chain. Moreover, predation risk strongly diminished the efficiency of energy transfer in the barnacle food chain but had no significant effect in the mussel food chain. The influence of resource identity on indirect-effect strength and energy transfer was likely caused by differences in how each resource shapes the degree of risk perceived by prey. We suggest that our understanding of the connection between trophic dynamics and ecosystem functioning will improve considerably once the effects of predation risk on individual behavior and physiology are considered. [ABSTRACT FROM AUTHOR]

Investigating how food supply regulates the behavior and population structure of predators remains a central focus of population and community ecology. These responses will determine the strength of bottom-up processes through the food web, which can potentially lead to coupled top-down regulation of local communities. However, characterizing the bottom-up effects of prey is difficult in the case of generalist predators and particularly with predators that have large dispersal scales, attributes that characterize most marine top predators. Here we use long-term data on mussel, barnacle, limpet, and other adult prey abundance and recruitment at sites spread over 970 km to investigate individual and population-level responses of the keystone intertidal sunstar 1-Jeliaster helianthus on the coast of Chile. Our results show that this generalist predator responds to changes in the supply of an apparently preferred prey, the competitively dominant mussel Perumytilus purpuratus. Individual-level parameters (diet composition, per capita prey consumption, predator size) positively responded to increased mussel abundance and recruitment, whereas population- level parameters (density, biomass, size structure) did not respond to bottom-up prey variation among sites separated by a few kilometers. No other intertidal prey elicited positive individual predator responses in this species, even though a large number of other prey species was always included in the diet. Moreover, examining predator-prey correlations at ∼80, 160, and 200 km did not change this pattern, suggesting that positive prey feedback could occur over even larger spatial scales or as a geographically unstructured process. Thus individual-level responses were not transferred to population changes over the range of spatial scales examined here, highlighting the need to examine community regulation processes over multiple spatial scales. [ABSTRACT FROM AUTHOR]

Recruitment variation can be a major source of fluctuation in populations and communities, making it difficult to generalize results. Determining the scales of variation and whether spatial patterns in the supply of individuals are persistent over time can provide insight into spatial generality and the application of conservation and metacommunity models. We examined these issues using eight-year-long data sets of monthly recruitment of intertidal mussels (Mylilus spp., Perumytilus purpuratus, Sernimytilus algosus, Brachidontes granulata) and barnacles (Balanus glandula, Chihamalus dalli, Jehlius cirratus, Noiochthainalus scabrosus) at sites spanning >900 km along the coasts of Oregon-northern California (OR-NCA, 45.47-39.43° N) and central Chile (CC, 29.5-34.65° S). We evaluated four general "null" hypotheses: that despite different phylogenies and great spatial separation of these taxa, their similar life history strategies and environmental settings lead to similar patterns of recruitment (1) between hemispheres, (2) in time, (3) in space, and (4) at larger and smaller spatial scales. Hypothesis 1 was rejected: along the OR-NCA coast, rates of recruitment were between two and three orders of magnitude higher, and patterns of seasonality were generally stronger and more coherent across space and time than along CC. Surprisingly, however, further analysis revealed regularities in both time and space for all species, supporting hypotheses 2 and 3. Temporal decorrelation scales were 1-3 months, and characteristic spatial scales of recruitment were ∼250 km. Contrary to hypothesis 4, for the ecologically dominant species in both hemispheres, recruitment was remarkably persistent at larger mesoscales (kilometers) but was highly stochastic at smaller microscales (meters). Across species, increased recruitment variation at large scales was positively associated with increased persistence. Our results have several implications. Although the two regions span distinct latitudinal ranges, potential forcing processes behind these patterns include similar large-scale climates and topographically locked hydrographic features, such as upwelling. Further, spatial persistence of the recruitment patterns of most species at the mesoscale supports the view that marine protected areas can be powerful conservation and management tools. Finally, persistent and yet contrasting spatial patterns of recruitment among competing species suggest that recent metacommunity models might provide useful representations of the mechanisms involved in species coexistence. [ABSTRACT FROM AUTHOR]

In marine systems, the occurrence and implications of disturbance-recovery cycles have been revealed at the landscape level, but only in demographically open or closed systems where landscape-level dynamics are assumed to have no feedback effect on regional dynamics. We present a mussel metapopulation model to elucidate the role of landscape-level disturbance cycles for regional response of mussel populations to onshore productivity and larval transport. Landscape dynamics are generated through spatially explicit rules, and each landscape is connected to its neighbor through unidirectional larval dispersal. The role of landscape disturbance cycles in the regional system behavior is elucidated (1) in demographically open vs. demographically coupled systems, in relation to (2) onshore reproductive output and (3) the temporal scale of landscape disturbance dynamics. By controlling for spatial structure at the landscape and metapopulation levels, we first demonstrate the interaction between landscape and oceanographic connectivity. The temporal scale of disturbance cycles, as controlled by mussel colonization rate, plays a critical role in the regional behavior of the system. Indeed, fast disturbance cycles are responsible for regional synchrony in relation to onshore reproductive output. Slow disturbance cycles, however, lead to increased robustness to changes in productivity and to demographic coupling. These testable predictions indicate that the occurrence and temporal scale of local disturbance- recovery dynamics can drive large-scale variability in demographically open systems, and the response of metapopulations to changes in nearshore productivity. [ABSTRACT FROM AUTHOR]

Mussel beds along the wave-exposed coast of the eastern North Pacific Ocean serve as an important habitat,' harboring a high diversity of species. A comparison of California mussel bed community diversity in 2002 to historical data (1960s to 1970s) revealed large declines (mean loss 58.9%), including some declines >141 species (∼80% loss). Concurrent work revealed inconsistent changes in mussel populations (biomass and bed thickness) along the California coast, suggesting that diversity declines may be related to large-scale processes rather than local habitat destruction. Potential factors causing declines in mussel community diversity are discussed, with regional climate change associated with the Pacific Decadal Oscillation and climate change-induced alterations of ecological interactions and biological processes suggested as likely causes. Although extensive literature has predicted the potential effects of climate change on global diversity, this study is one of the few examples of declines attributed to climate change. [ABSTRACT FROM AUTHOR]

In this study, we test in southern New Zealand a conceptual model of food web linkage that is seascape dependent, which can explain some of the variability in rocky shore community structure among sites and coasts. Using a comparative-experimental approach at local and distant sites we demonstrate that mobile subtidal predators (fish and crabs) can exert strong predation pressure on small mussels in the low tidal zone, but only in sites where the seascape includes subtidal reefs. On intertidal benches with adjacent subtidal reefs (+SR), 60-100% of small (5-15 mm) transplanted mussels were removed within a day from experimental tiles on the low shore when unprotected from predation, compared to fully caged controls that had approximately 100% survival over several months. In partial cages that exclude fish but not crabs, survivorship was intermediate. In contrast, on benches without subtidal reefs (-SR) 40-100% of mussels survived for months, even if unprotected. This difference is expressed in lower cover (0-60%) of mussels on rocks at +SR benches compared to -SR benches (70-99%). The central to northern west coast of the South Island is composed mostly of -SR benches, and predation on small mussels there was low and similar to the -SR benches on the east coast, whereas the +SR benches on the east coast had much greater predation. This contrasts to other studies in New Zealand that examined only predation on larger mussels by seastars and concluded that predation is strong on the west coast and weak on the east coast. Excluding large predators from low-shore areas with new recruits for a year in one +SR site showed longer-term predation effects on their abundance and cover. Short-term sampling at the east coast sites showed that mussel settlement was greater in -SR compared to +SR sites, providing some evidence that seascapes may also affect settlement. Overall, predation depended on the local seascape and ultimately affected community structure via suppression of effective recruitment rates. This study emphasizes the importance of predation on early life stages of basal species and the influence of seascapes on top-down interactions between subtidal predators and their intertidal prey. [ABSTRACT FROM AUTHOR]

We integrated across individual, population, community, and ecosystem levels to understand the impact of environmental stress by tracking the foundation species Mytilus edulis in the hypoxic estuary Narragansett Bay, Rhode Island, USA. Our initial surveys revealed that the mussels occurred in nine extensive (2-28 ha) dense (814-9943 individuals/m²) subtidal reefs that attracted a diverse suite of predators (sea stars, crabs, gastropods). Hypoxia occurred in the summer of 2001, and a mussel transplant experiment revealed overall reduced growth rates of individuals, and higher mortality rates among larger mussels. At the population level, large decreases in densities and cover of mussels were correlated with dissolved oxygen concentrations, leading to extinction at one site and reductions of over an order of magnitude at others. Within one year, seven of the eight remaining populations were edged to extinction, and the previously extinct population was recolonized. At the community level, a predator exclusion experiment indicated that predation was an unimportant source of mussel mortality during the hypoxic period, in part due to the emigration of sea stars, as predicted by the Consumer Stress Model. However, mussels were too intolerant to hypoxia to have a net benefit from the predation refuge. The seasonal (summer) occurrence of hypoxia allowed sea stars to return following a fag, as predicted by a stress return time model, and the resumption of predation contributed to the subsequent extinction of mussel populations. At the ecosystem level, the initial filtration rate of the mussel reefs was estimated at 134.6 × 106 m³/d, equivalent to filtering the volume of the bay 1.3 times during the 26-d average residence time. That function was reduced by >75% following hypoxia. The effect of hypoxia on each level of organization had consequences at others. For example, size-specific mortality and decreased growth of individuals, and reduced filtration capacity of reefs, indicated a loss of the ability of mussels to entrain planktonic productivity and potential to control future eutrophication and hypoxia. Our study quantified patterns of loss and identified pathways within an integrative framework of feedbacks, summarized in a conceptual model that is applicable to similar foundation species subjected to environmental stress. [ABSTRACT FROM AUTHOR]

The high trophic connectivity of many communities can produce large numbers of indirect interactions. Although many trait-mediated indirect interactions (TMII) are caused by changes in prey behavior, less is known about the effects of changes in predator behavior such as prey switching or multiple predator effects (MPE) on indirect interactions, especially in marine systems. We performed a series of field caging experiments off the Isles of Shoals, Maine (USA) from 2000 to 2002 to test for the presence of behaviorally mediated indirect effects in a shallow subtidal food web. Specifically, crab (Cancer borealis) predation on sea urchins ( Strongylocentrotus droebachiensis) was quantified in three habitats (Codium fragile algal beds, barrens, and mussel beds) representing differing combinations of food and shelter to examine the effects of prey switching by crabs. A second predator (the lobster, Homarus americanus) was added to the crab treatments to examine MPE effects. Urchin mortality was significantly lower in the mussel habitat than in the Codium and barren habitats. Mussels produced a positive indirect effect on urchins by changing the behavior of crabs; crabs fed on mussels instead of urchins (prey switching). In the barrens, crab predation on urchins indirectly increased the abundance of the introduced ascidian, Diplosoma sp., whereas Codium density did not change among treatments. A significant risk reduction for urchins occurred in Codium and barren habitats, but not in mussel habitats when crabs and lobsters were combined. Lobsters also produced a positive indirect effect on mussels by reducing crab predation. Thus, lobsters modify crab behavior and dampen changes in community structure. Our results illustrate the importance of predator behavior and habitat context in modifying consumer pressure and community structure, and argue for the consideration of these factors in other multi-predator systems where habitats represent food and/or shelter. [ABSTRACT FROM AUTHOR]

It was hypothesized that Rockweed stands and barnacle-mussel beds on sheltered rocky shores in New England may represent alternative states and outlined experimental tests suitable to address this question. This hypothesis was advanced because mussels and the seaweed Ascophyllum nodosuin are often codominant in sheltered bays, and their co-occurrence is not adequately explained by the standard paradigm of consumer control. It was suggested that the development of alternative states depends upon the timing and spatial scale of pulse perturbations. The results of experiments that show patch size determines the rates of predation and recruitment. Results provide evidence consistent with the formation of alternative communities on rocky shores of sheltered bays.

Examines the patch dynamics of mussels found on rocky shores in Halifax, Nova Scotia. Comparison of the dynamics of natural and experimentally constructed mussel patches; Processes in determining patch size and structure; Importance of wave disturbance than predation in determining patch structure.

Studies the growth and condition of seep mussels (Bathymodiolus childressi) at Brine Pool NR1, Gulf of Mexico. Influence of environment on the population dynamics of organisms; Characterization of the deep-sea environment; Analysis of spatial heterogeneity within both the population and the environment; Physiological conditions and growth of the mussels.

Investigates the role of the physical environment in determining the body temperatures of rocky intertidal mussels in terrestrial habitats. Estimation of errors from the use of environmental averages; Long-term predictions of mussel temperature in the field; Decoupling of the effects of climate and tidal cycle.

The effects of facultative epiphytes on a bivalve host were studied on an islet near Santa Catalina Island, California. The primary cover in the mid-intertidal zone was a mosaic of red algal turf (Corallina officinalis, Gigartina canaliculata, and Gelidium coulteri) and clumps of the mussel Mytilus californianus. In certain circumstances the algae attached to and overgrew the mussels. In other marine habitats, facultative epibionts benefit bivalve hosts by masking them from predators. At Catalina, spiny lobsters (Panulirus interruptus) and oystercatchers (Haematopus bachmani) preyed on intertidal mussels. However, in tagging studies, overgrown mussels displayed a nonsignificant trend towards lower survivorship. A factorial experiment manipulating exposure to predators and the cover of epiphytes demonstrated that overgrowth significantly reduced survivorship. There was no significant statistical interaction between treatment effects, indicating that the presence of algae did not protect the mussels from predators. Overgrown mussels also had significantly lower rates of growth and reproduction than naturally clear mussels of similar size and location. Experimental removal of the epiphytes caused significant increases in mussel growth and reproduction relative to overgrown controls. In the community circumstances chosen for this study, the epiphytic habit is a part of the processes in which otherwise freeliving algae become dominant on the rock surface.

Presents a study that examines whether gull predation is necessary to obtain a California mussels-(`Mytilus californianus')dominated community by determining whether differences in body size among sessile species can alter the ultimate outcome of competition for space. Location of study site; Regional effects of gull predation; Influence of the relative body size of species in this intertidal community.

This data set describes the abundance of 50 invertebrate taxa found in intertidal mussel beds along the Atlantic Canadian coast. This information resulted from a regional‐scale study that investigated the effects of wave exposure on the richness and composition of invertebrate assemblages from intertidal mussel beds. Abundance data are provided for taxa representing the Annelida, Arthropoda, Bryozoa, Chordata, Cnidaria, Echinodermata, Mollusca, Nematoda, Nemertea, and Platyhelminthes. The data characterize mussel beds from wave‐sheltered and wave‐exposed locations spanning 315 km of the coast of Nova Scotia. Univariate and multivariate analyses revealed that the compositional structure of these invertebrate assemblages differed markedly depending on wave exposure. Overall, because of its taxonomic diversity, the inclusion of data for basal, intermediate, and top trophic levels, and the coverage of two extremes of environmental stress, this data set could be useful to test broader aspects of ecological theory. Areas of ecology that could advance using this data set are those concerning environmental stress models of community organization, abundance–occupancy relationships, species co‐occurrence, species abundance distributions, dominance and rarity, spatial scales of population and community variation, and distribution of functional and phylogenetic diversity. Use of this data set for academic or educational purposes is allowed as long as the data source is properly cited. When used for academic or educational purposes, this data set should be cited using the title of this Data Paper, the names of the authors, the year of publication, and the corresponding volume and article numbers. [ABSTRACT FROM AUTHOR]

Mussel beds and seaweed canopies on Gulf of Maine rocky shores represent stochastic alternative community states. In the systems studied, community recovery from disturbance is highly deterministic and strongly driven by consumer control. Those mussel bed and algal-canopy sites were chosen that were as similar as could be found in terms of physical conditions. Sites with extreme physical conditions were avoided to maximize detecting the presence of stochastic alternative states. The mussel bed and algal-canopy sites chosen, however, did indeed differ in abiotic parameters and that is part of the problem.

Experimental clearings in macroalgal (Ascophyllum nodosuni) stands were made at 12 sites in 1996 to determine if mussel beds and macroalgal stands on sheltered intertidal shores of New England represent alternative community states. Sites were located on Swan's Island, Maine, USA. At each site an uncleared control plot and four sizes of circular clearings, which mimicked ice scour events, were established. The purpose of this data set is to provide access to recruitment data collected in the experimental plots from 1997 to 2007. [ABSTRACT FROM AUTHOR]

An abstract of the article "Densities and Cover Data for Intertidal Organisms in the Gulf of Maine, USA, From 2003 to 2007," by Peter S. Petraitis, Harrison Liu, and Erika C. Rhile is presented.

Experimental clearings, in macroalgal (Ascophyllum nodosum) stands were established in 1996 to determine if mussel beds and macroalgal stands on protected intertidal shores of New England represent alternative community states. Circular clearings 1, 2, 4, and 8 m in diameter were made in Ascophyllum stands at 12 sites on Swan's Island, Maine, USA. Each site also had an uncleared control. The sites are nested within four bays. The purpose of this data set is to provide access to data on densities and percent cover in the 60 experimental plots from 1996 to 2002. Data include densities of mussels (Mytilus edulis and Modiolus modiolus), an herbivorous limpet (Tectura testudinalis), herbivorous snails (Littorina littorea, Littorina obtusata), a predatory snail (Nucella lapillus), a barnacle (Semibalanus balanoides), and fucoid algae (Ascophyllum nodosum and Fucus vesiculosus), and percent cover by mussels, barnacles, and fucoids. Published analyses of the data set show that succession depends on clearing size and not on site-specific differences. [ABSTRACT FROM AUTHOR]