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Climate change can affect the distribution and abundance of marine life, with consequences for goods and services provided to people. Because different models can lead to divergent conclusions about marine futures, we present an integrated global ocean assessment of climate change impacts using an ensemble of multiple climate and ecosystem models. It reveals that global marine animal biomass will decline under all emission scenarios, driven by increasing temperature and decreasing primary production. Notably, climate change impacts are amplified at higher food web levels compared with phytoplankton. Our ensemble projections provide the most comprehensive outlook on potential climate-driven ecological changes in the global ocean to date and can inform adaptive management and conservation of marine resources under climate change.While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends.

A number of studies indicate that tropical arthropods should be particularly vulnerable to climate warming. If these predictions are realized, climate warming may have a more profound impact on the functioning and diversity of tropical forests than currently anticipated. Although arthropods comprise over two-thirds of terrestrial species, information on their abundance and extinction rates in tropical habitats is severely limited. Here we analyze data on arthropod and insectivore abundances taken between 1976 and 2012 at two midelevation habitats in Puerto Rico’s Luquillo rainforest. During this time, mean maximum temperatures have risen by 2.0 °C. Using the same study area and methods employed by Lister in the 1970s, we discovered that the dry weight biomass of arthropods captured in sweep samples had declined 4 to 8 times, and 30 to 60 times in sticky traps. Analysis of long-term data on canopy arthropods and walking sticks taken as part of the Luquillo Long-Term Ecological Research program revealed sustained declines in abundance over two decades, as well as negative regressions of abundance on mean maximum temperatures. We also document parallel decreases in Luquillo’s insectivorous lizards, frogs, and birds. While El Niño/Southern Oscillation influences the abundance of forest arthropods, climate warming is the major driver of reductions in arthropod abundance, indirectly precipitating a bottom-up trophic cascade and consequent collapse of the forest food web.

Soil organic matter (SOM) anchors global terrestrial productivity and food and fiber supply. SOM retains water and soil nutrients and stores more global carbon than do plants and the atmosphere combined. SOM is also decomposed by microbes, returning CO 2 , a greenhouse gas, to the atmosphere. Unfortunately, soil carbon stocks have been widely lost or degraded through land use changes and unsustainable forest and agricultural practices. To understand its structure and function and to maintain and restore SOM, we need a better appreciation of soil organic carbon (SOC) saturation capacity and the retention of above- and belowground inputs in SOM. Our analysis suggests root inputs are approximately five times more likely than an equivalent mass of aboveground litter to be stabilized as SOM. Microbes, particularly fungi and bacteria, and soil faunal food webs strongly influence SOM decomposition at shallower depths, whereas mineral associations drive stabilization at depths greater than ∼30 cm. Global uncertainties in the amounts and locations of SOM include the extent of wetland, peatland, and permafrost systems and factors that constrain soil depths, such as shallow bedrock. In consideration of these uncertainties, we estimate global SOC stocks at depths of 2 and 3 m to be between 2,270 and 2,770 Pg, respectively, but could be as much as 700 Pg smaller. Sedimentary deposits deeper than 3 m likely contain >500 Pg of additional SOC. Soils hold the largest biogeochemically active terrestrial carbon pool on Earth and are critical for stabilizing atmospheric CO 2 concentrations. Nonetheless, global pressures on soils continue from changes in land management, including the need for increasing bioenergy and food production.

Soil organic carbon (SOC) is primarily formed from plant inputs, but the relative carbon (C) contributions from living root inputs (i.e. rhizodeposits) vs litter inputs (i.e. root + shoot litter) are poorly understood. Recent theory suggests that living root inputs exert a disproportionate influence on SOC formation, but few field studies have explicitly tested this by separately tracking living root vs litter inputs as they move through the soil food web and into distinct SOC pools. We used a manipulative field experiment with an annual C4 grass in a forest understory to differentially track its living root vs litter inputs into the soil and to assess net SOC formation over multiple years. We show that living root inputs are 2–13 times more efficient than litter inputs in forming both slow-cycling, mineral-associated SOC as well as fast-cycling, particulate organic C. Furthermore, we demonstrate that living root inputs are more efficiently anabolized by the soil microbial community en route to the mineral-associated SOC pool (dubbed ‘the in vivo microbial turnover pathway’). Overall, our findings provide support for the primacy of living root inputs in forming SOC. However, we also highlight the possibility of nonadditive effects of living root and litter inputs, which may deplete SOC pools despite greater SOC formation rates.

Species interaction networks are shaped by abiotic and biotic factors. Here, as part of the Tara Oceans project, we studied the photic zone interactome using environmental factors and organismal abundance profiles and found that environmental factors are incomplete predictors of community structure. We found associations across plankton functional types and phylogenetic groups to be nonrandomly distributed on the network and driven by both local and global patterns. We identified interactions among grazers, primary producers, viruses, and (mainly parasitic) symbionts and validated network-generated hypotheses using microscopy to confirm symbiotic relationships. We have thus provided a resource to support further research on ocean food webs and integrating biological components into ocean models.

Microplastics are pervasive pollutants and have been found in all environmental compartments globally, including aquatic ecosystems. Ingestion and trophic transfer of microplastics through aquatic species have been widely reported. Although a plethora of studies have reported that microplastics can be transferred through higher trophic level food webs with the potential for accumulation and toxicity, most microplastic aquatic toxicity studies have been conducted in laboratory studies. This means that studies within entire ecosystems or at environmentally relevant concentrations are lacking, representing a critical knowledge gap for ecotoxicological impact of microplastics on aquatic species and higher trophic level consumers (including humans). Thus, an understanding of aquatic ecosystem toxicity is still relatively unknown. To address this knowledge gap, this study provides a non-exhaustive summary of microplastic transport pathways, ecotoxicology, food web transfer, and examples of toxic pollutants sorbed onto microplastics in aquatic food webs. This study will guide future research priorities to address microplastic toxicity through aquatic food webs.

The supply and demand of omega-3 highly unsaturated fatty acids (ω-3 HUFA) in natural ecosystems may lead to resource limitation in a diverse array of animal taxa. Here, we review why food quality in terms of ω-3 HUFAs is important, particularly for neural tissue, across a diversity of animal taxa ranging from invertebrate zooplankton to vertebrates (including humans). Our review is focused on ω-3 HUFAs rather than other unsaturated fatty acids because these compounds are especially important biochemically, but scarce in nature. We discuss the dichotomy between ω-3 HUFA availability between aquatic primary producers, which are often rich in these compounds, and terrestrial primary producers, which are contain little to none of them. We describe the use of fatty acids as qualitative and quantitative tracers for reconstructing animal diets in natural ecosystems. Next, we discuss both direct and indirect ecological implications of ω-3 HUFA limitation at the individual, population, food web, and ecosystem scales, which include: changes in behavior, species composition, secondary production rates, trophic transfer efficiency and cross-ecosystem subsidies. We finish by highlighting future research priorities including a need for more research on ω-3 HUFAs in terrestrial systems, more research their importance for higher order consumers, and more research on the food web and ecosystem-scale effects of ω-3 HUFA limitation. Synthesis Mismatches between the supply of and demand for omega-3 highly unsaturated fatty acids (ω-3 HUFA) in natural ecosystems have the potential to result in resource limitation across a diverse array of ecosystems. We combined perspectives from ecology and nutritional science to develop a unified synthesis of ω-3 HUFA ecology. We reviewed the importance of ω-3 HUFAs for animals, the striking differences in ω-3 HUFA availability at the base of terrestrial versus aquatic food webs, and the implications of ω-3 HUFA limitation for food webs. We finished by highlighting research priorities in the field including more research on ω-3 HUFAs in terrestrial systems, on higher order consumers, and at the food web and ecosystem-scales.

1. Healthy soils that contain an active microbiome and food web are critical to sustainably produce food for a growing global human population. Many studies have focussed on the role of microbial species diversity and the presence of key functional groups as important controls on the many functions that a sustainable food system relies on. 2. Here, we synthesise recent ecological empirical evidence and theory to propose that the interactions between organisms in the soil food web are the critical determinant of soil function. 3. We propose the Rhizosphere Interactions for Sustainable Agriculture Model, in which crop roots recruit small, modular, highly connected soil rhizosphere networks from large, static, relatively unconnected and diverse bulk soil networks. We argue that conventional agricultural management disrupts the connections between rhizosphere and bulk soil networks. 4. Synthesis. We identify future research directions for optimising ecological connections between roots and rhizosphere microbial and faunal networks, and between rhizosphere networks and bulk soil networks in agricultural production systems. Knowledge on these connections can be applied in agricultural systems to sustainability produce food for a growing global population.

Recently, studies on microplastics (MPs) have increased rapidly due to the growing awareness of the potential health risks related to their occurrence. The first part of this review is devoted to MP occurrence, distribution, and quantification. MPs can be transferred from the environment to humans mainly through inhalation, secondly from ingestion, and, to a lesser extent, through dermal contact. As regards food web contamination, we discuss the microplastic presence not only in the most investigated sources, such as seafood, drinking water, and salts, but also in other foods such as honey, sugar, milk, fruit, and meat (chickens, cows, and pigs). All literature data suggest not-negligible human exposure to MPs through the above-mentioned routes. Consequently, several research efforts have been devoted to assessing potential human health risks. Initially, toxicological studies were conducted with aquatic organisms and then with experimental mammal animal models and human cell cultures. In the latter case, toxicological effects were observed at high concentrations of MPs (polystyrene is the most common MP benchmark) for a short time. Further studies must be performed to assess the real consequences of MP contamination at low concentrations and prolonged exposure.

Various definitions and indices have been proposed in the literature to identify keystone species. In this study, we intended to make the concept of keystone species operational for marine biodiversity conservation. We used an exclusive definition of keystone species, based on the original concept of keystone predator, and derived a new functional index of keystoneness (KS) from an ecosystem-modeling approach. First, several KS indices were formulated, by combining measures of the mixed-trophic impact (MTI) and biomass of species. Then, a meta-analysis was performed, based on 101 published Ecopath food-web models, selected with a scoring method, and representative of the variety of marine ecosystems worldwide. The indices were applied to the models, and two statistical methods were compared to select the most promising KS index. Rank correlation tests were performed to assess the balance between the contribution of the impact and biomass components to the different KS indices. In addition, a classification tree was implemented, based on ecosystem-specific thresholds applied to the latter species traits, and used to confirm the identified keystone species. The selected index obtained the highest number of models with positive results from both the rank correlation tests and the classification tree. We also demonstrated the limitations of existing KS indices previously applied in the literature. Species were ranked according to their estimates of keystoneness with the selected KS index, so that potential keystone species were quantitatively identified in the 101 modeled food webs. The standardized modeling approach allowed for a comparison of the identified keystone species across models: cartilaginous fishes and toothed whales obtained the highest occurrences. Finally, the selected KS index was applied to the well-known case study of Prince William Sound (Alaska, USA). Potentially significant anthropogenic (fishing) impacts on keystone species were also considered and discussed. The operational methodology presented is directly applicable to marine food webs, and may be adapted to other (freshwater or terrestrial) systems.