Valuation of ecosystem services can provide evidence of the importance of sustaining and enhancing those resources and the ecosystems that provide them. Long appreciated only as a commercial source ...of oysters, oyster reefs are now acknowledged for the other services they provide, such as enhancing water quality and stabilizing shorelines. We develop a framework to assess the value of these services. We conservatively estimate that the economic value of oyster reef services, excluding oyster harvesting, is between $5500 and $99,000 per hectare per year and that reefs recover their median restoration costs in 2–14 years. In contrast, when oyster reefs are subjected to destructive oyster harvesting, they do not recover the costs of restoration. Shoreline stabilization is the most valuable potential service, although this value varies greatly by reef location. Quantifying the economic values of ecosystem services provides guidance about when oyster reef restoration is a good use of funds.
Views from the dock McClenachan, Loren; Scyphers, Steven; Grabowski, Jonathan H.
Ambio,
01/2020, Letnik:
49, Številka:
1
Journal Article
Recenzirano
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The ability of resource-dependent communities to adapt to climate change depends in part on their perceptions and prioritization of specific climate-related threats. In the Maine lobster fishery, ...which is highly vulnerable to warming water associated with climate change, we found a strong majority (84%) of fishers viewed warming water as a threat, but rank its impacts lower than other drivers of change (e.g., pollution). Two-thirds believed they will be personally affected by warming waters, but only half had plans to adapt. Those with adaptation plans demonstrated fundamentally different views of human agency in this system, observing greater anthropogenic threats, but also a greater ability to control the fishery through their own actions on the water and fisheries management processes. Lack of adaptation planning was linked to the view that warming waters result from natural cycles, and the expectation that technological advancements will help buffer the industry from warming waters.
Despite recognition of the significance of both food web interactions and habitat complexity in community dynamics, current ecological theory rarely couples these two processes. Experimental ...manipulations of the abundance of the two predators in an oyster-reef trophic cascade, and the structural complexity provided by reefs of living oysters, demonstrated that enhanced habitat complexity weakened the strengths of trophic interactions. The system of tri-trophic interactions included oyster toadfish (Opsanus tau) as the top predator that consumed the mud crab (Panopeus herbstii), which preys upon juvenile oysters (Crassostrea virginica). On reefs of low complexity, toadfish controlled mud crab abundances and indirectly determined the level of mortality of juvenile oysters. The indirect effects of toadfish on oysters emerged through their influence on how intensely mud crabs preyed on oysters. Augmentation of habitat complexity by substituting vertically oriented, living oysters for the flat shells of dead oysters disrupted both of the direct trophic linkages but did not alter the magnitude of the indirect effect of toadfish on juvenile oysters. This paradox can be understood by partitioning the mechanisms by which toadfish influence mud crabs and ultimately juvenile oysters. Trait-mediated indirect interactions (TMIIs; i.e., predator-avoidance behavior in mud crabs) accounted for 95.6-98.2% of toadfish indirect benefits to oyster survival and, consequently, were a much greater contributor than density-mediated indirect interactions (DMIIs; i.e., the reduction in crab abundance by toadfish). Avoidance behavior was unaffected by modification in habitat complexity. Complex reefs increased total oyster survival because added habitat complexity reduced mud crab predation on oysters. Additionally, the magnitude of this effect was much greater than the increase in oyster mortality as a result of complex reefs disrupting toadfish predation on mud crabs. This experimental demonstration of how habitat complexity modifies trophic interactions in a temperate reef community has fundamental implications for our understanding of species interaction webs and community structure. The influence of habitat complexity on the strength of a trophic cascade generally may depend upon whether physical complexity provides actual and perceived refuges for component predator-prey pairs.
Oyster reefs as carbon sources and sinks Fodrie, F. Joel; Rodriguez, Antonio B.; Gittman, Rachel K. ...
Proceedings - Royal Society. Biological sciences/Proceedings - Royal Society. Biological Sciences,
07/2017, Letnik:
284, Številka:
1859
Journal Article
Recenzirano
Odprti dostop
Carbon burial is increasingly valued as a service provided by threatened vegetated coastal habitats. Similarly, shellfish reefs contain significant pools of carbon and are globally endangered, yet ...considerable uncertainty remains regarding shellfish reefs' role as sources (+) or sinks (−) of atmospheric CO2. While CO2 release is a by-product of carbonate shell production (then burial), shellfish also facilitate atmospheric-CO2 drawdown via filtration and rapid biodeposition of carbon-fixing primary producers. We provide a framework to account for the dual burial of inorganic and organic carbon, and demonstrate that decade-old experimental reefs on intertidal sandflats were net sources of CO2 (7.1 ± 1.2 MgC ha−1 yr−1 (µ ± s.e.)) resulting from predominantly carbonate deposition, whereas shallow subtidal reefs (−1.0 ± 0.4 MgC ha−1 yr−1) and saltmarsh-fringing reefs (−1.3 ± 0.4 MgC ha−1 yr−1) were dominated by organic-carbon-rich sediments and functioned as net carbon sinks (on par with vegetated coastal habitats). These landscape-level differences reflect gradients in shellfish growth, survivorship and shell bioerosion. Notably, down-core carbon concentrations in 100- to 4000-year-old reefs mirrored experimental-reef data, suggesting our results are relevant over centennial to millennial scales, although we note that these natural reefs appeared to function as slight carbon sources (0.5 ± 0.3 MgC ha−1 yr−1). Globally, the historical mining of the top metre of shellfish reefs may have reintroduced more than 400 000 000 Mg of organic carbon into estuaries. Importantly, reef formation and destruction do not have reciprocal, counterbalancing impacts on atmospheric CO2 since excavated organic material may be remineralized while shell may experience continued preservation through reburial. Thus, protection of existing reefs could be considered as one component of climate mitigation programmes focused on the coastal zone.
Recreational fishery management poses unique challenges as diverse user groups often maintain disparate attitudes and behaviors, limiting our ability to predict how fishing mortality may change under ...future regulatory conditions. We surveyed Striped Bass Morone saxatilis anglers from multiple coastal Atlantic states to explore how potential policies may change fishing behavior, assess angler motivations and catch‐related attitudes, and determine whether attitudes correlate with intended behavior. Results revealed that rule changes fundamentally changed effort allocation, whereby participants often shifted fishing effort to other saltwater species. However, disparate groups of anglers responded quite differently to potential policies. Importantly, differences in participant attitudes about fishing, such as how much they value keeping fish, were important predictors of intended behavior. Overall, our study illustrates how behavior, and thus fishing mortality, may shift under future management scenarios, and that an understanding of the characteristics of recreational fishing populations may help to predict the directionality and magnitude of these changes.
Although use of refuge habitats by prey can reduce their risk of predation, refuge use may also involve costs such as increased within-refuge competition for resources. Despite the ubiquity of refuge ...use by prey, it is unknown whether predator-induced use of refuges has widespread, negative nonconsumptive effects on prey growth, survival, and fecundity. We performed a meta-analysis of 204 studies of aquatic taxa containing data on 271 distinct predator-prey pairs and found strong evidence that the negative effect of predation risk on prey activity, growth, and fecundity increases when prey have access to refuge habitats. Moreover, the effect of refuge habitats on growth and activity depends upon whether the refuge provides partial or total protection from predators. These results suggest that prey choosing whether to use refuges face a trade-off between lowering the immediate risk of being consumed and increased nonconsumptive costs of refuge use. Our results suggest that changes in nonconsumptive effects in the presence of refuge habitats may alter prey population dynamics, coexistence, and metapopulation dynamics. Moreover, our results reveal key pragmatic considerations: the magnitude and direction of nonconsumptive effects may depend on the presence of refuge habitat and whether the refuge provides partial or total protection from predators.
Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban ...shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems.
Reef-building oysters are important coastal foundation species that provide ecosystem services. Overharvesting, destructive fishing practices, and environmental degradation have caused significant ...declines in global oyster populations, necessitating restoration efforts in many regions to rebuild oyster habitat and recover lost services. Understanding how biological and physical gradients regulate oyster recruitment, survivorship and growth will help guide future efforts to successfully restore oyster populations. We conducted a field experiment in Ipswich, Massachusetts, to quantify the effects of tidal elevation, predator exclusion, and reef vertical relief on oyster settlement, recruitment and survivorship. Oyster settlement was 3 times greater at the deepest intertidal elevation compared to the 2 shallower intertidal elevations. Reef vertical relief and predator exclusion did not affect oyster settlement or survivorship. Despite increased sedimentation and algal fouling with increasing depth, living oyster densities remained significantly elevated at the deepest intertidal elevation 8 mo after the experimental reefs were constructed. Oyster mortality during this period was highest (>70%) at our shallowest elevation treatment, likely the result of desiccation and food limitation. Meanwhile, mortality during the first winter post-recruitment was high across all elevations (all >64%), with our deepest elevation treatment experiencing the highest mortality rate (90%). Our results suggest that there is a gradient in oyster settlement rates, which increase at lower elevation, and that the dominant drivers of mortality also likely vary with elevation. Our findings highlight the need for region-specific studies to quantify biological and physical gradients prior to large-scale restoration efforts.
Predator effects on prey dynamics are conventionally studied by measuring changes in prey abundance attributed to consumption by predators. We revisit four classic examples of predator—prey systems ...often cited in textbooks and incorporate subsequent studies of nonconsumptive effects of predators (NCE), defined as changes in prey traits (e.g., behavior, growth, development) measured on an ecological time scale. Our review revealed that NCE were integral to explaining lynx—hare population dynamics in boreal forests, cascading effects of top predators in Wisconsin lakes, and cascading effects of killer whales and sea otters on kelp forests in nearshore marine habitats. The relatives roles of consumption and NCE of wolves on moose and consequent indirect effects on plant communities of Isle Royale depended on climate oscillations. Nonconsumptive effects have not been explicitly tested to explain the link between planktonic alewives and the size structure of the zooplankton, nor have they been invoked to attribute keystone predator status in intertidal communities or elsewhere. We argue that both consumption and intimidation contribute to the total effects of keystone predators, and that characteristics of keystone consumers may differ from those of predators having predominantly NCE. Nonconsumptive effects are often considered as an afterthought to explain observations inconsistent with consumption-based theory. Consequently, NCE with the same sign as consumptive effects may be overlooked, even though they can affect the magnitude, rate, or scale of a prey response to predation and can have important management or conservation implications. Nonconsumptive effects may underlie other classic paradigms in ecology, such as delayed density dependence and predator-mediated prey coexistence. Revisiting classic studies enriches our understanding of predator—prey dynamics and provides compelling rationale for ramping up efforts to consider how NCE affect traditional predator—prey models based on consumption, and to compare the relative magnitude of consumptive and NCE of predators.
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