Search

The global carbon sequestration and avoided emissions potentially achieved via blue carbon is high (∼3% of annual global greenhouse gas emissions); however, it is limited by multidisciplinary and interacting uncertainties spanning the social, governance, financial, and technological dimensions. We compiled a transdisciplinary team of experts to elucidate these challenges and identify a way forward. Key actions to enhance blue carbon as a natural climate solution include improving policy and legal arrangements to ensure equitable sharing of benefits; improving stewardship by incorporating indigenous knowledge and values; clarifying property rights; improving financial approaches and accounting tools to incorporate co-benefits; developing technological solutions for measuring blue carbon sequestration at low cost; and resolving knowledge gaps regarding blue carbon cycles. Implementing these actions and operationalizing blue carbon will achieve measurable changes to atmospheric greenhouse gas concentrations, provide multiple co-benefits, and address national obligations associated with international agreements.

The UN Decade of Ecosystem Restoration is a response to the urgent need to substantially accelerate and upscale ecological restoration to secure Earth’s sustainable future. Globally, restoration commitments have focused overwhelmingly on terrestrial forests. In contrast, despite a strong value proposition, efforts to restore seaweed forests lag far behind other major ecosystems and continue to be dominated by small-scale, short-term academic experiments. However, seaweed forest restoration can match the scale of damage and threat if moved from academia into the hands of community groups, industry, and restoration practitioners. Connecting two rapidly growing sectors in the Blue Economy—seaweed cultivation and the restoration industry—can transform marine forest restoration into a commercial-scale enterprise that can make a significant contribution to global restoration efforts. info:eu-repo/semantics/publishedVersion

The genomic era continues to revolutionize our understanding of the evolution of biodiversity. In phycology, emphasis remains on assembling nuclear and organellar genomes, leaving the full potential of genomic datasets to answer long-standing questions about the evolution of biodiversity largely unexplored. Here, we used whole-genome sequencing (WGS) datasets to survey species diversity in the kelp genus Alaria, compare phylogenetic signals across organellar and nuclear genomes, and specifically test whether phylogenies behave like trees or networks. Genomes were sequenced from across the global distribution of Alaria (including Alaria crassifolia, A. praelonga, A. crispa, A. marginata, and A. esculenta), representing over 550 GB of data and over 2.2 billion paired reads. Genomic datasets retrieved 3,814 and 4,536 single-nucleotide polymorphisms (SNPs) for mitochondrial and chloroplast genomes, respectively, and upwards of 148,542 high-quality nuclear SNPs. WGS revealed an Arctic lineage of Alaria, which we hypothesize represents the synonymized taxon A. grandifolia. The SNP datasets also revealed inconsistent topologies across genomic compartments, and hybridization (i.e., phylogenetic networks) between Pacific A. praelonga, A. crispa, and putative A. grandifolia, and between some lineages of the A. marginata complex. Our analysis demonstrates the potential for WGS data to advance our understanding of evolution and biodiversity beyond amplicon sequencing, and that hybridization is potentially an important mechanism contributing to novel lineages within Alaria. We also emphasize the importance of surveying phylogenetic signals across organellar and nuclear genomes, such that models of mixed ancestry become integrated into our evolutionary and taxonomic understanding.

Marine heatwaves (MHWs) have caused declines in many kelp forests globally. Although the ecological effects of these climatic extremes have been well examined, studies on the role of genotypic variation in underpinning population responses under pressures are lacking. Understanding how kelps respond to different warming profiles and, in particular, intraspecific variation in responses is necessary to confidently anticipate the future of kelp forests, yet this remains a critical knowledge gap for most species. This study examined the responses of early life stages of 9 different genotypes of the Australian kelp Ecklonia radiata to different MHW profiles, where cumulative heat intensity was kept constant: control treatment (constant 19°C), heat spikes (fluctuating 19-23°C), low intensity MHW (ramp up 23°C) and high intensity MHW (ramp up 27°C). Overall, we found significant declines in E. radiata gametophyte performance in all MHW treatments and delays in sporophyte recruitment during MHW exposure. We also found significant genotype by environment (G×E) interactions, suggesting tolerance to acute thermal stress is influenced by genetic variation. Our results showed that offspring from different genotypes within the same population respond differently to MHWs, indicating that some genotypes are susceptible to MHWs while others are more resistant. While the effects on standing genetic variation and subsequent susceptibility to other stressors are unknown, our findings suggest that in addition to immediate impacts on marine organisms, natural genotypic variation in response to thermal anomalies may facilitate the gradual evolution of populations with increased thermal tolerance under future climates.

Este artículo contiene 16 páginas, 5 figuras, 1 tabla., Aim The influence of niche and neutral mechanisms on the assembly of ecological communities have long been debated. However, we still have a limited knowledge on their relative importance to explain patterns of diversity across latitudinal gradients (LDG). Here, we investigate the extent to which these ecological mechanisms contribute to the LDG of reef fishes. Location Eastern Atlantic Ocean. Taxon Reef-associated ray-finned fishes. Methods We combined abundance data across ~60° of latitude with functional trait data and phylogenetic trees. A null model approach was used to decouple the influence of taxonomic diversity (TD) on functional (FD) and phylogenetic (PD) diversity. Standardized effect sizes (SES FD and SES PD) were used to explore patterns of overdispersion, clustering and randomness. Information theoretic approaches were used to investigate the role of large- (temperature, geographic isolation, nitrate and net primary productivity) and local-scale (human population and depth) drivers. We further assessed the role of demographic stochasticity and its interaction with species trophic identity and dispersal capacity. Results Taxonomic diversity peaked at ~15°–20°N, with a second mode of lower magnitude at ~45°N; a pattern that was predicted by temperature, geographic isolation and productivity. Tropical regions displayed a higher proportion of overdispersed assemblages, whilst clustering increased towards temperate regions. Phylogenetic and functional overdispersion were associated with warmer, productive and isolated regions. Demographic stochasticity also contributed largely to community assembly, independently of ecoregions, although variation was dependent on the trophic identity and body size of species. Main conclusions Niche-based processes linking thermal and resource constraints to local coexistence mechanisms have contributed to the LDG in reef fishes. These processes do not act in isolation, stressing the importance of understanding interactions between deterministic and stochastic factors driving community structure in the face of rapid biodiversity change., This study was partially supported by Portuguese national funds from FCT—Foundation for Science and Technology through project UIDB/04326/2020. C.R. and P.N. were financially supported by the Oceanic Observatory of Madeira Project (M1420-01-0145-FEDER-000001—Observatório Oceânico da Madeira-OOM). D.A.S. was supported by a UKRI Future Leaders Fellowship (MR/S032827/1). P.J.M. was supported by a Marie Curie Career Integration Grant (PCIG10-GA-2011-303685). T.W. received funding from the Australian Research Council (DP170100023).

Understanding the effects of ecological disturbances in coastal habitats is crucial and timely as these are anticipated to increase in intensity and frequency in the future due to increasing human pressure. In this study we used directed kelp trawling as a scientific tool to quantify the impacts of broad-scale disturbance on community structure and function. We tested the ecosystem-wide effects of this disturbance in a BACI design using two 15 km2 areas. The disturbance had a substantial impact on the kelp forests in this study, removing 2986 tons of kelp and causing a 26% loss of total kelp canopy at trawled stations. This loss created a 67% reduction of epiphytes, an 89% reduction of invertebrates and altered the fish populations living within these habitats. The effect of habitat loss on fish was variable and depended on how the different species used the habitat structure. Our results show that large-scale experimental disturbances on habitat-forming species have ecological consequences that extend beyond the decline of the single species to affect multiple trophic levels of the broader ecosystem. Our findings have relevance for understanding how increasing anthropogenic disturbances, including kelp trawling and increased storm frequency caused by climate change, may alter ecosystem structure and function.

Recognition of the potential for vegetated coastal ecosystems to store and sequester carbon has led to their increasing inclusion into global carbon budgets and carbon offset schemes. However, kelp forests have been overlooked in evaluations of this ‘blue carbon’, which have been limited to tidal marshes, mangrove forests, and seagrass beds. We determined the continental-scale contribution to blue carbon from kelp forests in Australia using areal extent, biomass, and productivity measures from across the entire Great Southern Reef. We reveal that these kelp forests represent 10.3–22.7 Tg C and contribute 1.3–2.8 Tg C year−1 in sequestered production, amounting to more than 30% of total blue carbon stored and sequestered around the Australian continent, and ~ 3% of the total global blue carbon. We conclude that the omission of kelp forests from blue carbon assessments significantly underestimates the carbon storage and sequestration potential from vegetated coastal ecosystems globally.

Forests are key components of the global carbon cycle and dominate mitigation strategies for climate change and biodiversity loss. In contrast, the importance of and threats facing ocean forests—kelp forests—are comparatively underappreciated. Yet, increasing the global area of kelp forests would enhance biodiversity and drawdown CO2, mitigating climate change.

Kelp forests are in decline globally and large-scale intervention could be required to halt the loss of these valuable ecosystems. To date kelp forest restoration has had limited success and been expensive and unable to address the increasing scale of ecosystem deterioration. Here we developed and tested a new approach: “green gravel”. Small rocks were seeded with kelp and reared in the laboratory until 2–3 cm, before out-planting to the field. The out-planted kelp had high survival and growth over 9 months, even when dropped from the surface. This technique is cheap, simple, and does not require scuba diving or highly trained field workers. It can be up-scaled to treat large areas or even used to introduce genes from more resilient kelp populations onto vulnerable reefs. Green gravel thus overcomes some of the current major limitations of kelp restoration and provides a promising new defense against kelp forest decline.

The paper — Seaweed ecosystems may not mitigate CO2 emissions (Gallagher et al., 2022) — claims that seaweed ecosystems are carbon sources rather than carbon sinks because ‘respiration subsidies’ (from inputs of allochthonous organic carbon) create negative net ecosystem production. That is, that seaweed ecosystems produce more CO2 than they draw down, and thus may not mitigate CO2 emissions. They make this claim using a compiled dataset which shows that, on average, seaweed ecosystems are net heterotrophic. However, their assessment is flawed and conceptually misleading as key terms are misinterpreted, the data presented are biased, and the conclusions are not supported statistically. Here we discuss four flaws in the argument presented by Gallagher et al., which we believe risk confusing further research on seaweed blue carbon and unjustifiably seeding doubt around motivations and initiatives to protect and restore seaweed forests.

In this chapter we describe the approaches available for kelp restoration and emphasizethat you will need to consider the best suited approach(es) for your particular project (Fig. 5.1).The selected methodology will depend on the expertise of your group, project budget, thestressors present, environmental conditions, and whether kelp can return naturally or needsre-introduction

Understanding the extent to which species’ traits mediate patterns of community assembly is key to predict the effect of natural and anthropogenic disturbances on ecosystem functioning. Here, we apply a trait-based community assembly framework to understand how four different habitat configurations (kelp forests, Sargassum spp. beds, hard corals, and turfs) shape the trophic and energetic dynamics of reef fish assemblages in a tropical–temperate transition zone. Specifically, we tested (i) the degree of trait divergence and convergence in each habitat, (ii) which traits explained variation in species’ abundances, and (iii) differences in standing biomass (kg ha−1), secondary productivity (kg ha−1 day−1) and turnover (% day−1). Fish assemblages in coral and kelp habitats displayed greater evidence of trait convergence, while turf and Sargassum spp. habitats displayed a higher degree of trait divergence, a pattern that was mostly driven by traits related to resource use and thermal affinity. This filtering effect had an imprint on the trophic and energetic dynamics of reef fishes, with turf habitats supporting higher fish biomass and productivity. However, these gains were strongly dependent on trophic guild, with herbivores/detritivores disproportionately contributing to among-habitat differences. Despite these perceived overall gains, turnover was decoupled for fishes that act as conduit of energy to higher trophic levels (i.e. microinvertivores), with coral habitats displaying higher rates of fish biomass replenishment than turf despite their lower productivity. This has important implications for biodiversity conservation and fisheries management, questioning the long-term sustainability of ecological processes and fisheries yields in increasingly altered marine habitats.

Coastal refugia during the Last Glacial Maximum (~21,000 years ago) have been hypothesized at high latitudes in the North Atlantic, suggesting marine populations persisted through cycles of glaciation and are potentially adapted to local environments. Here, whole-genome sequencing was used to test whether North Atlantic marine coastal populations of the kelp Alaria esculenta survived in the area of southwestern Greenland during the Last Glacial Maximum. We present the first annotated genome for A. esculenta and call variant positions in 54 individuals from populations in Atlantic Canada, Greenland, Faroe Islands, Norway and Ireland. Differentiation across populations was reflected in ~1.9 million single nucleotide polymorphisms, which further revealed mixed ancestry in the Faroe Islands individuals between putative Greenlandic and European lineages. Time-calibrated organellar phylogenies suggested Greenlandic populations were established during the last interglacial period more than 100,000 years ago, and that the Faroe Islands population was probably established following the Last Glacial Maximum. Patterns in population statistics, including nucleotide diversity, minor allele frequencies, heterozygosity and linkage disequilibrium decay, nonetheless suggested glaciation reduced Canadian Atlantic and Greenlandic populations to small effective sizes during the most recent glaciation. Functional differentiation was further reflected in exon read coverage, which revealed expansions unique to Greenland in 337 exons representing 162 genes, and a modest degree of exon loss (103 exons from 56 genes). Altogether, our genomic results provide strong evidence that A. esculenta populations were resilient to past climatic fluctuations related to glaciations and that high-latitude populations are potentially already adapted to local conditions as a result.

The magnitude and distribution of net primary production (NPP) in the coastal ocean remains poorly constrained, particularly for shallow marine vegetation. Here, using a compilation of in situ annual NPP measurements across >400 sites in 72 geographic ecoregions, we provide global predictions of the productivity of seaweed habitats, which form the largest vegetated coastal biome on the planet. We find that seaweed NPP is strongly coupled to climatic variables, peaks at temperate latitudes, and is dominated by forests of large brown seaweeds. Seaweed forests exhibit exceptionally high per-area production rates (a global average of 656 and 1711 gC m −2 year −1 in the subtidal and intertidal, respectively), being up to 10 times higher than coastal phytoplankton in temperate and polar seas. Our results show that seaweed NPP is a strong driver of production in the coastal ocean and call for its integration in the oceanic carbon cycle, where it has traditionally been overlooked.

Net primary productivity (NPP) plays a pivotal role in the global carbon balance but estimating the NPP of underwater habitats remains a challenging task. Seaweeds (marine macroalgae) form the largest and most productive underwater vegetated habitat on Earth. Yet, little is known about the distribution of their NPP at large spatial scales, despite more than 70 years of local-scale studies being scattered throughout the literature. We present a global dataset containing NPP records for 246 seaweed taxa at 429 individual sites distributed on all continents from the intertidal to 55 m depth. All records are standardized to annual aerial carbon production (g C m−2 yr−1) and are accompanied by detailed taxonomic and methodological information. The dataset presented here provides a basis for local, regional and global comparative studies of the NPP of underwater vegetation and is pivotal for achieving a better understanding of the role seaweeds play in the global coastal carbon cycle.

The production and fate of seaweed detritus is a major unknown in the global C-budget. Knowing the quantity of detritus produced, the form it takes (size) and its timing of delivery are key to understanding its role as a resource subsidy to secondary production and/or its potential contribution to C-sequestration. We quantified the production and release of detritus from 10 Laminaria hyperborea sites in northern Norway (69.6° N). Kelp biomass averaged 770 ± 100 g C m−2 while net production reached 499 ± 50 g C m−2 year−1, with most taking place in spring when new blades were formed. Production of biomass was balanced by a similar formation of detritus (478 ± 41 g C m−2 year−1), and both were unrelated to wave exposure when compared across sites. Distal blade erosion accounted for 23% of the total detritus production and was highest during autumn and winter, while dislodgment of whole individuals and/or whole blades corresponded to 24% of the detritus production. Detachment of old blades constituted the largest source of kelp detritus, accounting for > 50% of the total detrital production. Almost 80% of the detritus from L. hyperborea was thus in the form of whole plants or blades and > 60% of that was delivered as a large pulse within 1–2 months in spring. The discrete nature of the delivery suggests that the detritus cannot be retained and consumed locally and that some is exported to adjacent deep areas where it may subsidize secondary production or become buried into deep marine sediments as blue carbon.

Complex socio-environmental challenges require interdisciplinary, team-based research capacity. Graduate students are fundamental to building such capacity, yet formal opportunities for graduate students to develop these capacities and skills are uncommon. This paper presents an assessment of the Graduate Pursuit (GP) program, a formal interdisciplinary team science graduate research and training program administered by the National Socio-Environmental Synthesis Center (SESYNC). Quantitative and qualitative assessment of the program’s first cohort revealed that participants became significantly more comfortable with interdisciplinary research and team science approaches, increased their capacity to work across disciplines, and were enabled to produce tangible research outcomes. Qualitative analysis of four themes—(1) discipline, specialization, and shared purpose, (2) interpersonal skills and personality, (3) communication and teamwork, and (4) perceived costs and benefits—encompass participants’ positive and negative experiences and support findings from past assessments. The findings also identify challenges and benefits related to individual personality traits and team personality orientation, the importance of perceiving a sense of autonomy and independence, and the benefit of graduate training programs independent of the university and graduate program environment.

Seascapes dominated by large, structurally complex seaweeds are ubiquitous. These critical ecosystems are under increasing pressure from human activities, and conceiving successful management strategies to ensure their persistence and/or recovery is of paramount importance. Currently, ecosystems dominated by large seaweeds are referred to as either ‘forests’ or ‘beds’. We demonstrate how this dual terminology is confusing, is used inconsistently, and reduces the efficiency of communication about the importance and perils of seaweed habitats. As a consequence, it undermines work to alleviate and mitigate their loss and impedes research on unifying principles in ecology. We conclude that there are clear benefits of simply using the more intuitive term ‘forest’ to describe all seascapes dominated by habitat-forming seaweeds. This is particularly true as researchers scramble to reconcile ecological functions and patterns of change across disparate regions and species to match the increasingly global scale of environmental forcing on these critical ecosystems

Net primary productivity (NPP) plays a pivotal role in the global carbon balance, but estimating the NPP of underwater habitats remains a challenging task. Seaweeds (marine macroalgae) form the largest and most productive underwater vegetated habitat on Earth. Yet, little is known about the distribution of their NPP at large spatial scales, despite more than 70 years of local-scale studies being scattered throughout the literature. We present a global dataset containing NPP records for 242 seaweed species at 419 individual sites distributed on all continents from the intertidal to 55 m depth. All records are standardized to annual aerial carbon production (g C m-2yr-1) and are accompanied by detailed taxonomical and methodological information. The dataset presented here provides a basis for local, regional and global comparative studies of the NPP of underwater vegetation, and is pivotal for achieving a better understanding of the role seaweeds play in the global coastal carbon cycle.

15 pages, 12 figures, supplementary data https://doi.org/10.1016/j.dsr.2020.103433, Kelp forests produce large amounts of macroalgal detritus, ranging from whole plants to small particles (1 mm). The role of this kelp detritus in fueling deep-sea communities adjacent to healthy kelp forests was investigated in a region in the north of Norway by comparing the community structure and biodiversity of meio-, macro-, and megafauna in two deep (450 m) areas with different expected input of kelp detritus: a deep fjord basin surrounded by kelp forests and the adjacent continental shelf 15 km offshore from the kelp forests. The results showed that, although the fjord received a significantly higher amount of large kelp detritus (i.e. blades) than the shelf area, the amount of small kelp detritus available on the sediment was similar in both areas. There were significant differences in the multidimensional scaling analyses on the community structure for meio-, macro-, and megafauna between the fjord and the shelf. Significant differences were also found in biomass, abundance and biodiversity indices for some groups. However, no clear pattern emerged in the community structure and biodiversity between the fjord and the shelf, and the observed differences could not be linked directly to kelp detritus availability. The similar amounts of small particles of kelp detritus in the fjord and shelf area suggest that kelp detritus can provide organic matter to ecosystems further away than initially hypothesized, thus potentially shaping the structure and functioning of deep benthic communities distant from the kelp forests. Yet, the direct (trophic) links of kelp detritus and the studied benthic fauna need to be further analysed. The results are discussed in relation to current global changes in kelp forest, including regime shifts from healthy kelp reefs to turfs or barren areas, which reduce drastically the amount of macroalgal detritus produced and exported, This study was funded by the Norwegian Research Council through the KELPEX project (NRC Grant no. 255085/E40). With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Funding Funding for this work was provided by the Australian Research Council (TW: FT110100174, TW, KFD: DP190100058), the University of Western Australia Research Collaboration Awards (TW, TdB, JCL, DD, JNF, HC), the France-Australia Science Innovation Collaboration 2014 program (TdB, TW, JCL, DD), Metabomer and Corsaire Core Facility (CL), the French Government run by the National Research Agency with regards to the investment expenditure programme IDEALG ANR-10-BTBR-04 (JCL, DD) and the Norwegian Research Council (TW, MFP, KFD, KELPEX 255085/E40). As the environment is getting warmer and species are redistributed, consumers can be forced to adjust their interactions with available prey, and this could have cascading effects within food webs. To better understand the capacity for foraging flexibility, our study aimed to determine the diet variability of an ectotherm omnivore inhabiting kelp forests, the sea urchin Echinus esculentus, along its entire latitudinal distribution in the northeast Atlantic. Using a combination of gut content and stable isotope analyses, we determined the diet and trophic position of sea urchins at sites in Portugal (42° N), France (49° N), southern Norway (63° N), and northern Norway (70° N), and related these results to the local abundance and distribution of putative food items. With mean estimated trophic levels ranging from 2.4 to 4.6, omnivory and diet varied substantially within and between sites but not across latitudes. Diet composition generally reflected prey availability within epiphyte or understorey assemblages, with local affinities demonstrating that the sea urchin adjusts its foraging to match the small-scale distribution of food items. A net “preference” for epiphytic food sources was found in northern Norway, where understorey food was limited compared to other regions. We conclude that diet change may occur in response to food source redistribution at multiple spatial scales (microhabitats, sites, regions). Across these scales, the way that key consumers alter their foraging in response to food availability can have important implication for food web dynamics and ecosystem functions along current and future environmental gradients. info:eu-repo/semantics/publishedVersion

Kelps are highly productive macroalgae that form habitats along one-quarter of the worlds’ coastlines. Emerging evidence suggests that kelps have the potential to sequester carbon through the export of detritus to deep marine sinks, yet how much of this detrital carbon is remineralized through grazing and microbial decomposition before it reaches these sinks remains a critical knowledge gap. We measured decay of Laminaria hyperborea detritus in shallow kelp forests (10 m) and adjacent deep fjords (300 m), and experimentally tested the effect of temperature and oxygen conditions similar to those at these habitats in ex situ experiments. Initial decay rate (k) was high (-0.107 to -0.183 d-1) with 40-60% of the original carbon biomass being lost within few weeks, after which decay rates slowed down (k = -0.009 to -0.038 d-1). Temperature had little effect on the rate and extent of decomposition within the temperature range tested (4-10°C). Blade detritus decomposed almost completely in 300 d under aerobic conditions. Anaerobic decay of both blade and stipe detritus ceased, in contrast, after 150-200 d, leaving 20-30% of the initial biomass to decompose extremely slowly or not at all. Decomposition was followed by changes in chemical composition; C:N ratios increased substantially, while mannitol and phenolics disappeared almost completely from the detritus matrix. Slow and incomplete anaerobic decomposition suggest that the potential for long-term burial and sequestration of kelp carbon will be enhanced if detritus is exported to nearby deep areas with permanent or periodic hypoxia near the bottom.

Special issue: Marine ecosystem restoration: theory, practice and future perspectives.-- This research is part of POLARCSIC activities.-- 8 figures, 1 table, supporting information https://doi.org/10.1111/rec.13327.-- This is the pre-peer reviewed version of the following article: Daniel Vilas, Marta Coll, Torstein Pedersen, Xavier Corrales, Karen Filbee-Dexter, Thomas Wernberg; Future trajectories of change for an Arctic deep-sea ecosystem connected to coastal kelp forests; Restoration Ecology 29(S2): e13327 (2021), which has been published in final form at https://doi.org/10.1111/rec.13327. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions, Environmental stressors related to climate change and other anthropogenic activities are impacting Arctic marine ecosystems at exceptional rates. Within this context, predicting future scenarios of deep-sea ecosystems and their consequences linked with the fate of coastal areas is a growing need and challenge. We used an existing food-web model developed to represent the outer basin of the Malangen fjord, a northern Norwegian deep-sea ecosystem, to assess the potential effects of plausible future trajectories of change for major drivers in the area, including links to coastal kelp forests. We considered four major drivers (kelp particulate organic matter [POM] production entering the deep sea, fishing effort, king crab invasion, and ocean warming) to project 12 future scenarios using the temporal dynamic module of Ecopath with Ecosim approach. Overall, we found that the impact of warming on the deep-sea ecosystem structure and functioning, as well as on ecosystem services, are predicted to be greater than changes in kelp forest dynamics and their POM production entering the deep sea and the king crab invasion. Yet, the cumulative impacts are predicted to be more important than noncumulative since some stressors acted synergistically. These results illustrate the vulnerability of sub-Arctic and Arctic marine ecosystems to climate change and consequently call for conservation, restoration, and adaptation measures in deep-sea and adjacent ecosystems. Results also highlight the importance of considering additional stressors affecting deep-sea communities to predict cumulative impacts in an ecosystem-based management and global change context and the interlinkages between coastal and deep-sea environments, This work was funded by the Norwegian Research Council through the KELPEX project (NRC Grant no. 255085/E40). [...] MC acknowledges partial funding by the European Union´s Horizon research program grant agreement No 689518 for the MERCES project, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Este artículo contiene 14 páginas, 6 figuras, 1 tabla., Humans are rapidly transforming the structural configuration of the planet's eco systems, but these changes and their ecological consequences remain poorly quantified in underwater habitats. Here, we show that the loss of forest-forming seaweeds and the rise of ground-covering ‘turfs’ across four continents consistently resulted in the miniaturization of underwater habitat structure, with seascapes converging towards flattened habitats with smaller habitable spaces. Globally, turf seascapes occupied a smaller architectural trait space and were structurally more similar across regions than marine forests, evidencing habitat homogenization. Surprisingly, such habitat convergence occurred despite turf seascapes consisting of vastly different species richness and with different taxa providing habitat archi tecture, as well as across disparate drivers of marine forest decline. Turf seascapes contained high sediment loads, with the miniaturization of habitat across 100s of km in mid-Western Australia resulting in reefs retaining an additional ~242 million tons of sediment (four orders of magnitude more than the sediments delivered flu vially annually). Together, this work demonstrates that the replacement of marine forests by turfs is a generalizable phenomenon that has profound consequences for the ecology of temperate reefs., Holsworth Wildlife Research Endowment; Ministerio de Economía, Industria y Competitividad, Gobierno de España, Grant/Award Number: CTM2017-86695- C3-1-R; Australian Research Council, Grant/Award Number: DE190100692 and DP190100058; UWA; Australian Government International Research Training Program

Este artículo contiene 11 páginas, 3 figuras, 1 tabla., The term ‘Blue Carbon’ was coined about a decade ago to highlight the important carbon sequestration capacity of coastal vegetated ecosystems. The term has paved the way for the development of programs and policies that preserve and restore these threatened coastal ecosystems for climate change mitigation. Blue carbon research has focused on quantifying carbon stocks and burial rates in sediments or accumulating as biomass. This focus on habitat-bound carbon led us to losing sight of the mobile blue carbon fraction. Oceans, the largest active reservoir of carbon, have become somewhat of a blind spot. Multiple recent investigations have revealed high outwelling (i.e., lateral fluxes or horizontal exports) of dissolved inorganic (DIC) and organic (DOC) carbon, as well as particulate organic carbon (POC) from blue carbon habitats. In this paper, we conceptualize outwelling in mangrove, saltmarsh, seagrass and macroalgae ecosystems, diagnose key challenges preventing robust quanti fication, and pave the way for future work integrating mobile carbon in the blue carbon framework. Outwelling in mangroves and saltmarshes is usually dominated by DIC (mostly as bicarbonate), while POC seems to be the major carbon species exported from seagrass meadows and macroalgae forests. Carbon outwelling science is still in its infancy, and estimates remain limited spatially and temporally. Nevertheless, the existing datasets imply that carbon outwelling followed by ocean storage is relevant and may exceed local sediment burial as a long-term (>centuries) blue carbon sequestration mechanism. If this proves correct as more data emerge, ignoring carbon outwelling may underestimate the perceived sequestration capacity of blue carbon ecosystems., Research on the topic was initiated with support from the Australian Research Council and concluded with funding from the Swedish Research Council to IRS. OS acknowledges financial support from Edith Cowan University. DJB acknowledges support from the US National Science Foundation (OCE 1635403). TCJ acknowledges support from the German Federal Ministry of Education and Research (03F0471A, 03F0644A). The graphical ab stract photo was provided by Luke Jeffrey.

Extreme climatic events including marine heatwaves (MHWs) are becoming more frequent and severe in the Anthropocene. However, our understanding of how these events affect population dynamics of ecologically important species is limited, in part because extreme events are rare and difficult to predict. Here, we quantified the occurrence and severity of MHWs over 60 years in warm range edge kelp forests on both sides of the North Atlantic. The cumulative annual intensity of MHWs increased two- to four-fold during this period, coinciding with the disappearance of kelps. We experimentally demonstrated a relationship between strong and severe 2018 heatwaves and high kelp mortality in both regions. Patterns of kelp mortality were strongly linked to maximum temperature anomalies, which crossed lethal thresholds in both regions. Translocation and tagging experiments revealed similar kelp mortality rates on reefs dominated by healthy kelp forests and degraded sediment-laden algal ‘turfs’, indicating equal vulnerability to extreme events. These results suggest a mechanistic link between MHWs and broad-scale kelp loss, and highlight how warming can make ecosystem boundaries unstable, forcing shifts to undesirable ecosystem states under episodically extreme climatic conditions.

Compelling new evidence shows that kelp production contributes an important and underappreciated flux of carbon in the ocean. Major questions remain, however, about the controls on the cycling of this organic carbon in the coastal zone, and their implications for future carbon sequestration. Here we used field experiments distributed across 28° latitude, and the entire range of two dominant kelps in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to environmental factors. Ocean temperature was the strongest control on detritus decomposition in both species, and it was positively related to decomposition. This suggests that decomposition could accelerate with ocean warming under climate change, increasing remineralization and reducing overall kelp carbon sequestration. However, we also demonstrate the potential for high kelp-carbon storage in cooler (northern) regions, which could be targeted by climate mitigation strategies to expand blue carbon sinks.

Marine plant communities such as kelp forests produce significant amounts of detritus, most of which is exported to areas where it can constitute an important trophic subsidy or potentially be sequestered in marine sediments. Knowing the vertical transport speed of detrital particles is critical to understanding the potential magnitude and spatial extent of these linkages. We measured sinking speeds for Laminaria hyperborea detritus ranging from whole plants to small fragments and sea urchin faecal pellets, capturing the entire range of particulate organic matter produced by kelp forests. Under typical current conditions, we determined that this organic material can be transported 10 s of m to 10 s of km. We show how the conversion of kelp fragments to sea urchin faeces, one of the most pervasive processes in kelp forests globally, increases the dispersal potential of detritus by 1 to 2 orders of magnitude. Kelp detritus sinking speeds were also faster than equivalent phytoplankton, highlighting its potential for rapid delivery of carbon to deep areas. Our findings support arguments for a significant contribution from kelp forests to subsidizing deep sea communities and the global carbon sink.

Author(s): Filbee-Dexter, K; Symons, CC; Jones, K; Haig, HA; Pittman, J; Alexander, SM; Burke, MJ | Abstract: A key challenge facing ecologists and ecosystem managers is understanding what drives unexpected shifts in ecosystems and limits the effectiveness of human interventions. Research that integrates and analyses data from natural and social systems can provide important insight for unravelling the complexity of these dynamics. It is, therefore, a critical step towards the development of evidence-based, whole-system management approaches. To examine our ability to influence ecosystems that are behaving in unexpected ways, we explore three prominent cases of “ecological surprise.” We captured the social-ecological systems (SES) using key variables and interactions from Ostrom’s SES framework, which integrates broader ecosystem processes (e.g. climate, connectivity), management variables (e.g. quotas, restrictions, monitoring), resource use behaviours (e.g. harvesting) and the resource unit (e.g. trees, fish, clean water) being managed. Structural equation modelling revealed that management interventions often influenced resource use behaviours (e.g. rules and limits strongly affected harvest or pollution), but they did not have a significant effect on the abundance of the managed resource. Instead, most resource variability was related to ecological processes and feedbacks operating at broader spatial or temporal scales than management interventions, which locked the resource system into the degraded state. Synthesis and applications. Mismatch between the influence of management systems and ecosystem processes can limit the effectiveness of human interventions during periods of ecological surprise. Management strategies should shift from a conventional focus on removal or addition of a single resource towards solutions that influence the broader ecosystem. Operationalizing Ostrom’s framework to quantitatively analyse social-ecological systems using structural equation models shows promise for testing solutions to navigate these events.

The invasive seagrass Halophila stipulacea has spread throughout the eastern Caribbean since it was first recorded in Grenada in 2002. We quantified the distribution and abundance of H. stipulacea , and its associated macroinvertebrate fauna, in sampling stations and transects around the island of Carriacou (a nearby dependency of Grenada) in early 2016. Halophila stipulacea occurred in extensive monospecific stands (average bottom cover, 62%), or smaller mixed stands with native seagrass ( Thalassia testudinum , Syringodium filiforme , Halodule wrightii ), at 1–5 m depth in large bays along the leeward (west) coast. It was sparsely distributed on the more wave-exposed east and south coasts, usually in mixed patches with native seagrass. In leeward bays, H. stipulacea has largely replaced the native seagrass H. wrightii , providing a novel biogenic habitat for various filter-feeding invertebrates living within the turf-like leaf canopy (e.g., sponges, ascidians, bivalves, ophiuroids), and sea urchins (mainly Tripneustes ventricousus ) and a microphagous sea star ( Oreaster reticulatus ) that graze upon it. Populations of the sea star consisted mainly of juveniles indicating the seagrass may serve as a nursery habitat for this endangered species. The spread of H. stipulacea along the leeward coast of Carriacou in recent years represents a community-level shift in the shallow subtidal zone, with attendant changes in habitat structure, species composition, and trophic interactions.

Highlights • A large body of literature exists on extreme cold ocean temperature events. • These events have well documented negative impacts but no consistent definition. • We propose here a definition for use in the detection of marine cold-spells (MCSs). • MCSs are decreasing in count, duration, and intensity over most ocean surfaces. • MCSs are increasing in count and duration in the Southern Ocean. Characterising ocean temperature variability and extremes is fundamental for understanding the thermal bounds in which marine ecosystems have adapted. While there is growing evidence of how marine heatwaves threaten marine ecosystems, prolonged periods of extremely cold ocean temperatures, marine cold-spells, have received less global attention. We synthesize the literature on cold ocean temperature extremes and their ecological impacts and physical mechanisms. Ecological impacts of these events were observed across a range of species and biophysical processes, including mass mortalities, range shifts, marine habitat loss, and altered phenology. The development of marine cold-spells is often due to wind-induced ocean processes, but a range of physical mechanisms are documented in the literature. Given the need for consistent comparison of marine cold-spells, we develop a definition for detecting these events from temperature time series and for classifying them into four categories. This definition is used to consistently detect marine cold-spells globally over the satellite record and to compare the characteristics of notable cold events. Globally, marine cold-spells’ occurrence, duration, and intensity are decreasing, with some areas, such as the Southern Ocean, showing signs of increase over the past 15 years. All marine cold-spell categories are affected by these decreases, with the exception of “IV Extreme” events, which were so rare that there has been little decrease. While decreasing occurrences of marine cold-spells could be viewed as providing a beneficial reduction in cold stress for marine ecosystems, fewer cold spells will alter the temperature regime that marine ecosystems experience and could have important consequences on ecological structure and function.