Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the ...coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Climate change strains human and natural system sustainability worldwide. Plum Island Estuary, Massachusetts (PIE MA) salt marshes are socio-environmental ecosystems experiencing two such climate ...stressors: sea level rise (SLR) and the mud fiddler crab
Minuca pugnax
(=
Uca pugnax
Smith) range expansion. Salt marshes are important sources of ecosystem functioning and ecosystem services. Uncertainties remain, however, whether SLR and the fiddler crab range expansion will affect PIE ecosystem functioning and services over time by changing marsh area. We, therefore, determined in this study: (1) to what degree PIE marshes provide residents with cultural ecosystem services (e.g., recreation); (2) whether SLR and the fiddler crab range expansion influence marsh area; and (3) whether policy measures influence the direction of marsh services in the face of SLR and multiple potential impacts of range expanding fiddler crabs. We developed a system dynamics model, parameterized with data from stakeholder surveys, the IPCC Report, and a literature review. We modeled low, moderate, and high SLR both with fiddler crabs enhancing marsh erosion and growth, and with and without mitigation strategies on marsh area and recreation. The multi-stressor effects of fiddler crab
erosion
enhancement and high SLR rates decreased marsh area by 2250. Future losses to marsh area caused declines in recreational days. Policy interventions (e.g., erosion reduction and tidal flood mitigation) largely mitigated these losses. Fiddler crab marsh
growth
by itself also strongly mitigated the effects of SLR. These results provide critical transdisciplinary insight for residents, scientists, and practitioners working to enhance PIE sustainability, and for researchers studying how to support environmental sustainability at scale.
Perhaps the most pressing issue in predicting biotic responses to present and future global change is understanding how environmental factors shape the relationship between ecological traits and ...extinction risk. The fossil record provides millions of years of insight into how extinction selectivity (i.e., differential extinction risk) is shaped by interactions between ecological traits and environmental conditions. Numerous paleontological studies have examined trait‐based extinction selectivity; however, the extent to which these patterns are shaped by environmental conditions is poorly understood due to a lack of quantitative synthesis across studies. We conducted a meta‐analysis of published studies on fossil marine bivalves and gastropods that span 458 million years to uncover how global environmental and geochemical changes covary with trait‐based extinction selectivity. We focused on geographic range size and life habit (i.e., infaunal vs. epifaunal), two of the most important and commonly examined predictors of extinction selectivity. We used geochemical proxies related to global climate, as well as indicators of ocean acidification, to infer average global environmental conditions. Life‐habit selectivity is weakly dependent on environmental conditions, with infaunal species relatively buffered from extinction during warmer climate states. In contrast, the odds of taxa with broad geographic ranges surviving an extinction (>2500 km for genera, >500 km for species) are on average three times greater than narrow‐ranging taxa (estimate of odds ratio: 2.8, 95% confidence interval = 2.3–3.5), regardless of the prevailing global environmental conditions. The environmental independence of geographic range size extinction selectivity emphasizes the critical role of geographic range size in setting conservation priorities.
Manipulative field experiments provide a window into the complexity of nature. Yet there is concern that we lack resolution by conducting experiments on a scale that is too small and short to include ...the relevant complexity of the study system. We addressed this issue by asking how and why the scale (local and global spatial extent, spatial grain, duration) and complexity (number of species, factors, treatment combinations) of experiments performed on marine hard substrata (rocky intertidal, RI; coral reef, CR; rocky subtidal, RS; mangrove root, MR) has changed by assessing 311 total experiments published since 1961 in
Ecology
and
Ecological Monographs
and since 1967 in
Journal of Experimental Marine Biology and Ecology
. We show that the local spatial extent and all metrics of complexity increased as a positive, log-linear function of time. In contrast, the size of experimental units (spatial grain) decreased with time. Quantile regression analysis revealed that these trends are largely driven by changes in the upper bounds of experimental scale and complexity; most studies are still relatively simple in design and conducted over small areas. A structural equation model (SEM) incorporated the direct and indirect effects of six metrics indicating that the complexity of field experiments has increased both as a direct effect of time and because experiments have become smaller in spatial grain. The SEM also showed longer experiments tended to be more complex. We show striking habitat differences, as subtidal experiments (CR, RS) involved more species and were carried out on the largest global spatial scales. RI experiments were the longest.
Future prospects to incorporate more of the complexity of nature into field experiments include site replication, as only 34.7% of all experiments were conducted at more than one site, open experimental designs monitored by technology, and integrating experimental manipulations with long-term monitoring to achieve mechanistic insight across scales relevant to human alteration of the biosphere. The increasing resolution of remote sensing also creates opportunities to track experiment-driven changes in community structure across large scales. We suggest applying these methods to a wider class of problems to enhance our understanding of marine communities and ecosystems.
The impacts of global change—from shifts in climate to overfishing to land use change—can depend heavily on local abiotic context. Building an understanding of how to downscale global change ...scenarios to local impacts is often difficult, however, and requires historical data across large gradients of variability. Such data are often not available—particularly in peer reviewed or gray literature. However, these data can sometimes be gleaned from casual records of natural history—field notebooks, data sheet marginalia, course notes, and more. Here, we provide an example of one such approach for the Gulf of Maine, as we seek to understand how environmental context can influence local outcomes of region‐wide shifts in subtidal community structure. We explore a decade of hand‐drawn algal cover maps around Appledore Island made by Dr. Art Borror while teaching at the Shoals Marine Lab. Appledore's steep wave exposure gradient—from exposed to the open ocean to fully protected—provides a living laboratory to test interactions between global change and local conditions. We then recreate Borror's methods two and a half decades later. We show that overfishing‐driven urchin outbreaks in the 1980s were slowed or stopped by wave exposure and benthic topography. Similarly, local variation appears to have curtailed current invasions by filamentous red algae. Last, some formerly dominant kelps have disappeared over the past 40 years—an observation verified by subtidal surveys. Global change is altering life in the seas around us. While underutilized, solid natural history observations stand as a key resource for us to begin to understand how global change will translate to the heterogeneous mosaic of life in a future Gulf of Maine and other ecosystems around the world.
Feral hogs modify ecosystems by consuming native species and altering habitat structure. These invasions can generate fundamentally different post‐invasion habitats when disturbance changes community ...structure, ecosystem function, or recovery dynamics. Here, we use multiple three‐year exclusion experiments to describe how feral hogs affect hyper‐productive brackish marshes over time. We find that infrequent yet consistent hog foraging and trampling suppresses dominant plants by generating a perpetually disturbed habitat that favors competitively inferior species and disallows full vegetative recovery over time. Along borders between plant monocultures, trampling destroys dominant graminoids responsible for most aboveground marsh biomass while competitively inferior plants increase fivefold. Hog activities shift the brackish marsh disturbance regime from pulse to press, which changes the plant community: competitively inferior plants increase coverage, species diversity is doubled, and live cover is lowered by 30% as large plants are unable to take hold in hog‐disturbed areas. Release from disturbance does not result in complete recovery (i.e., dominant plant monocultures) because hog consumer control is a combination of both top‐down control and broader engineering effects. These results highlight how habitats are susceptible to invasive effects outside of structural destruction alone, especially if large consumers are pervasive over time and change the dynamics that sustain recovery.
Climate change plays a large role in driving species range shifts; however, the physical characteristics of an environment can also influence and alter species distributions. In New England salt ...marshes, the mud fiddler crab
Minuca pugnax
is expanding its range north of Cape Cod, MA, into the Gulf of Maine (GoM) due to warming waters. The burrowing lifestyle of
M. pugnax
means sediment compaction in salt marshes may influence the ability of crabs to dig, with more compact soils being resistant to burrowing. Previous studies indicate that salt marshes along the GoM have a higher sediment compaction relative to marshes south of Cape Cod. Physical characteristics of this habitat may be influencing the burrowing performance of
M. pugnax
and therefore the continuation of their northward range expansion into the GoM. We conducted a controlled laboratory experiment to determine if compaction affects the burrowing activity of
M. pugnax
in historical and range-expanded populations. We manipulated sediment compaction in standardized lab assays and measured crab burrowing performance with individuals collected from Nantucket (NAN, i.e. historical range) and the Plum Island Estuary (PIE, i.e. expanded range). We determined compaction negatively affected burrowing ability in crabs from both sites; however, crabs from PIE have a higher probability of burrowing in higher sediment compactions than NAN crabs. In addition, PIE crabs were more likely to burrow overall. We conclude that site level differences in compaction are likely altering burrowing behavior in the crab’s expanded-range territory by way of local adaptation or phenotypic plasticity.
Climate change is negatively impacting ecosystems and their contributions to human well‐being, known as ecosystem services. Previous research has mainly focused on the direct effects of climate ...change on species and ecosystem services, leaving a gap in understanding the indirect impacts resulting from changes in species interactions within complex ecosystems. This knowledge gap is significant because the loss of a species in a food web can lead to additional species losses or “co‐extinctions,” particularly when the species most impacted by climate change are also the species that play critical roles in food web persistence or provide ecosystem services. Here, we present a framework to investigate the relationships among species vulnerability to climate change, their roles within the food web, their contributions to ecosystem services, and the overall persistence of these systems and services in the face of climate‐induced species losses. To do this, we assess the robustness of food webs and their associated ecosystem services to climate‐driven species extinctions in eight empirical rocky intertidal food webs. Across food webs, we find that highly connected species are not the most vulnerable to climate change. However, we find species that directly provide ecosystem services are more vulnerable to climate change and more connected than species that do not directly provide services, which results in ecosystem service provision collapsing before food webs. Overall, we find that food webs are more robust to climate change than the ecosystem services they provide and show that combining species roles in food webs and services with their vulnerability to climate change offer predictions about the impacts of co‐extinctions for future food web and ecosystem service persistence. However, these conclusions are limited by data availability and quality, underscoring the need for more comprehensive data collection on linking species roles in interaction networks and their vulnerabilities to climate change.
This study presents a framework to explore how species' roles in food webs and their vulnerability to climate change affect ecosystem services. The researchers find that while food webs show resilience to species extinctions driven by climate change, the services provided by these webs are more susceptible to collapse. The findings emphasize the need for more detailed data on species interactions and vulnerabilities to better predict the impacts of climate change on ecosystems and the services they provide.
Ecological theory predicts that kelp forests structured by trophic cascades should experience recovery and persistence of their foundation species when herbivores become rare. Yet, climate change may ...be altering the outcomes of top‐down forcing in kelp forests, especially those located in regions that have rapidly warmed in recent decades, such as the Gulf of Maine. Here, using data collected annually from 30+ sites spanning >350 km of coastline, we explored the dynamics of Maine's kelp forests in the ~20 years after a fishery‐induced elimination of sea urchin herbivores. Although forests (Saccharina latissima and Laminaria digitata) had broadly returned to Maine in the late 20th century, we found that forests in northeast Maine have since experienced slow but significant declines in kelp, and forest persistence in the northeast was juxtaposed by a rapid, widespread collapse in the southwest. Forests collapsed in the southwest apparently because ocean warming has—directly and indirectly—made this area inhospitable to kelp. Indeed, when modeling drivers of change using causal techniques from econometrics, we discovered that unusually high summer seawater temperatures the year prior, unusually high spring seawater temperatures, and high sea urchin densities each negatively impacted kelp abundance. Furthermore, the relative power and absolute impact of these drivers varied geographically. Our findings reveal that ocean warming is redefining the outcomes of top‐down forcing in this system, whereby herbivore removal no longer predictably leads to a sustained dominance of foundational kelps but instead has led to a waning dominance (northeast) or the rise of a novel phase state defined by “turf” algae (southwest). Such findings indicate that limiting climate change and managing for low herbivore abundances will be essential for preventing further loss of the vast forests that still exist in northeast Maine. They also more broadly highlight that climate change is “rewriting the rules” of nature, and thus that ecological theory and practice must be revised to account for shifting species and processes.
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