Future redistribution of fishery resources suggests biological and economic trade-offs according to the severity of the emission scenario.

Climate change is anticipated to have long-term and pervasive effects on marine ecosystems, with cascading consequences to many ocean-reliant sectors. For the marine fisheries sector, these impacts can be further influenced by future socio-economic and political factors. This raises the need for robust projections to capture the range of potential biological and economic risks and opportunities posed by climate change to marine fisheries. Here, we project future changes in the abundance of eight commercially important fish and crab species in the eastern Bering Sea and Chukchi Sea under different CMIP6 Shared Socioeconomic Pathways (SSPs) leading to contrasting future (2021-2100) scenarios of warming, sea ice concentration, and net primary production. Our results revealed contrasting patterns of abundance and distribution changes across species, time periods and climate scenarios, highlighting potential winners and losers under future climate change. In particular, the least changes in future species abundance and distribution were observed under SSP126. However, under the extreme scenario (SSP585), projected Pacific cod and snow crab abundances increased and decreased, respectively, with concurrent zonal and meridional future shifts in their centers of gravity. Importantly, projected changes in species abundance suggest that fishing at the same distance from the current major port in the Bering Sea (i.e., Dutch Harbor) could yield declining catches for highly valuable fisheries (e.g., Pacific cod and snow crab) under SSP585. This is driven by strong decreases in future catches of highly valuable species despite minimal declines in maximum catch potential, which are dominated by less valuable taxa. Hence, our findings show that projected changes in abundance and shifting distributions could have important biological and economic impacts on the productivity of commercial and subsistence fisheries in the eastern Bering and Chukchi seas, with potential implications for the effective management of transboundary resources.

Interactions between climate warming, herbicides, and eutrophication in the aquatic food web.

Understanding the interactive effects of multiple environmental stressors on biological communities is crucial for effective environmental management and biodiversity conservation. Here, we present the results of an outdoor mesocosm experiment examining how an aquatic food web responds to the individual and combined effects of climate warming, heat waves, nutrient enrichment, and herbicide exposure. To assess ecosystem functioning, we examined energy flow, using stable isotope analysis integrated with the bioenergetics food web approach to quantify energy fluxes among trophic levels. Our results revealed that the combined effects of these stressors altered the pattern of energy fluxes within the food web. Under warming conditions, there was an increase in energy flux from producers and primary consumers to secondary consumers. However, we did not observe a significant increase in energy flux in primary consumers, potentially due to enhanced top-down control. Nutrient enrichment increased energy flux from producers to higher trophic levels while simultaneously decreasing detrital energy flux. Herbicide exposure did not significantly affect herbivory energy flux but did reduce detritivory energy flux, particularly from detritus to primary consumers. The interactive effects we observed were primarily antagonistic or additive, although we also detected reversed and synergistic effects. The responses to multiple stressors varied across different energy flow pathways, leading to an asymmetric response. Furthermore, our results also revealed significant differences in the effects of constant warming and heat waves, either alone or in combination with water pollution. The asymmetric response of energy flow pathways and the prevalence of antagonistic effects present significant challenges for ecosystem restoration. Together, our findings provide novel and clear evidence of the complex mechanisms by which the coexistence of stressors can differently affect the pathways of energy flux across trophic levels in aquatic ecosystems. Regulatory strategies for ecosystems should comprehensively consider responses at multi-trophic levels using a network perspective, especially in the face of combinations of global and local stressors.

Multiple facets of marine biodiversity in the Pacific Arctic under future climate.

Climate change is triggering a global reorganization of marine life. Biogeographical transition zones, diversity-rich regions straddling biogeographical units where many species live at, or close to, their physiological tolerance limits (i.e., range distribution edges), are redistribution hotspots that offer a unique opportunity to understand the mechanisms and consequences of climate-driven thermophilization processes in natural communities. In this context, we examined the impacts of climate change projections in the 21st century (2026-2100) on marine biodiversity in the Eastern Bering and Chukchi seas within the Pacific Arctic, a climatically exposed and sensitive boreal-to-Arctic transition zone. Overall, projected changes in species distributions, modeled using species distribution models, resulted in poleward increases in species richness and functional redundancy, along with pronounced reductions in phylogenetic distances by century's end (2076-2100). Future poleward shifts of boreal species in response to warming and sea ice changes are projected to alter the taxonomic and functional biogeography of contemporary Arctic communities as larger, longer-lived and more predatory taxa expand their leading distributional margins. Drawing from the existing evidence from other Arctic regions, these changes are anticipated to increase the susceptibility and vulnerability of the Arctic ecosystems, as trophic connectance between biological components increases, thus decreasing the modularity of Arctic food webs. Our results demonstrate how integrating multiple diversity facets can provide key insights into the relationships between climate change, species composition and ecosystem functioning across marine biogeographic regions.

A dynamic temperature difference control recording system in shallow lake mesocosm.

The effects of climate change on shallow lakes were studied via control experiments, such as a mesocosm study. Accurate control, monitoring and recording of temperature difference are crucial for the ongoing simulation of warming mesocosm. In this article, we provide a method that can adjust automatically and allow real-time monitoring and recording of water temperature. This system is composed of three main parts: the temperature sensor DS18B20, which measures and outputs the digital temperature value; a C8051F320 microcontroller, which acquires, analyses and stores the temperature data and performs control upon start and shutdown of external heating elements; and external heating devices perform heating until the target temperature difference is achieved.•This system can maintain a certain temperature difference under gradually changing external environmental conditions.•This system can achieve real-time online monitoring of water temperature.•This system has an excellent ability to resist disturbance.

Realistic fisheries management reforms could mitigate the impacts of climate change in most countries.

Although climate change is altering the productivity and distribution of marine fisheries, climate-adaptive fisheries management could mitigate many of the negative impacts on human society. We forecast global fisheries biomass, catch, and profits to 2100 under three climate scenarios (RCPs 4.5, 6.0, 8.5) and five levels of management reform to (1) determine the impact of climate change on national fisheries and (2) quantify the national-scale benefits of implementing climate-adaptive fisheries reforms. Management reforms accounting for shifting productivity and shifting distributions would yield higher catch and profits in the future relative to today for 60-65% of countries under the two least severe climate scenarios but for only 35% of countries under the most severe scenario. Furthermore, these management reforms would yield higher cumulative catch and profits than business-as-usual management for nearly all countries under the two least severe climate scenarios but would yield lower cumulative catch for 40% of countries under the most severe scenario. Fortunately, perfect fisheries management is not necessary to achieve these benefits: transboundary cooperation with 5-year intervals between adaptive interventions would result in comparable outcomes. However, the ability for realistic management reforms to offset the negative impacts of climate change is bounded by changes in underlying biological productivity. Although realistic reforms could generate higher catch and profits for 23-50% of countries experiencing reductions in productivity, the remaining countries would need to develop, expand, and reform aquaculture and other food production sectors to offset losses in capture fisheries. Still, climate-adaptive management is more profitable than business-as-usual management in all countries and we provide guidance on implementing-and achieving the benefits of-climate-adaptive fisheries reform along a gradient of scientific, management, and enforcement capacities.

Improved fisheries management could offset many negative effects of climate change.

The world's oceans supply food and livelihood to billions of people, yet species' shifting geographic ranges and changes in productivity arising from climate change are expected to profoundly affect these benefits. We ask how improvements in fishery management can offset the negative consequences of climate change; we find that the answer hinges on the current status of stocks. The poor current status of many stocks combined with potentially maladaptive responses to range shifts could reduce future global fisheries yields and profits even more severely than previous estimates have suggested. However, reforming fisheries in ways that jointly fix current inefficiencies, adapt to fisheries productivity changes, and proactively create effective transboundary institutions could lead to a future with higher profits and yields compared to what is produced today.

Geographical limits to species-range shifts are suggested by climate velocity.

The reorganization of patterns of species diversity driven by anthropogenic climate change, and the consequences for humans, are not yet fully understood or appreciated. Nevertheless, changes in climate conditions are useful for predicting shifts in species distributions at global and local scales. Here we use the velocity of climate change to derive spatial trajectories for climatic niches from 1960 to 2009 (ref. 7) and from 2006 to 2100, and use the properties of these trajectories to infer changes in species distributions. Coastlines act as barriers and locally cooler areas act as attractors for trajectories, creating source and sink areas for local climatic conditions. Climate source areas indicate where locally novel conditions are not connected to areas where similar climates previously occurred, and are thereby inaccessible to climate migrants tracking isotherms: 16% of global surface area for 1960 to 2009, and 34% of ocean for the 'business as usual' climate scenario (representative concentration pathway (RCP) 8.5) representing continued use of fossil fuels without mitigation. Climate sink areas are where climate conditions locally disappear, potentially blocking the movement of climate migrants. Sink areas comprise 1.0% of ocean area and 3.6% of land and are prevalent on coasts and high ground. Using this approach to infer shifts in species distributions gives global and regional maps of the expected direction and rate of shifts of climate migrants, and suggests areas of potential loss of species richness.

Interactions among temporal patterns determine the effects of multiple stressors.

Recent research has revealed that one of the most important characteristics of both natural and anthropogenic disturbances is their temporal heterogeneity. However, little is known about the relative importance of interactions among temporal patterns of multiple stressors. We established a fully factorial field experiment to test whether interactions among temporal patterns of two globally important anthropogenic disturbances of aquatic ecosystems (increased sediment loading and nutrient enrichment) determined the responses of stream benthic assemblages. Each disturbance treatment comprised three distinct regimes: regular and temporally variable pulses and an undisturbed control. The overall frequency, intensity and extent of disturbance was, however, equal across all disturbed treatments. We found that interactions among temporal disturbance regimes determined the effects of the compounded sediment and nutrient perturbations on algal biomass and the diversity, taxonomic and trophic composition of benthic assemblages. Moreover, our results also show that the temporal synchronization of multiple stressors does not necessarily maximize the impact of compounded perturbations. This comprises the first experimental evidence that interactions among the temporal patterns of disturbances drive the responses of ecosystems to multiple stressors. Knowledge of the temporal pattern of disturbances is therefore essential for the reliable prediction of impacts from, and effective management of, compounded perturbations.