Description: Zooplankton plays a major role in ocean food webs and biogeochemical cycles, and provides major ecosystem services as a main driver of the biological carbon pump and in sustaining fish communities. Zooplankton is also sensitive to its environment and reacts to its changes. To better understand the importance of zooplankton, and to inform prognostic models that try to represent them, spatially-resolved biomass estimates of key plankton taxa are desirable. In this study we predict, for the first time, the global biomass distribution of 19 zooplankton taxa (1-50 mm Equivalent Spherical Diameter) using observations with the Underwater Vision Profiler 5, a quantitative in situ imaging instrument. After classification of 466,872 organisms from more than 3,549 profiles (0-500 m) obtained between 2008 and 2019 throughout the globe, we estimated their individual biovolumes and converted them to biomass using taxa-specific conversion factors. We then associated these biomass estimates with climatologies of environmental variables (temperature, salinity, oxygen, etc.), to build habitat models using boosted regression trees. The results reveal maximal zooplankton biomass values around 60°N and 55°S as well as minimal values around the oceanic gyres. An increased zooplankton biomass is also predicted for the equator. Global integrated biomass (0-500 m) was estimated at 0.403 PgC. It was largely dominated by Copepoda (35.7%, mostly in polar regions), followed by Eumalacostraca (26.6%) Rhizaria (16.4%, mostly in the intertropical convergence zone). The machine learning approach used here is sensitive to the size of the training set and generates reliable predictions for abundant groups such as Copepoda (R2 ≈ 20-66%) but not for rare ones (Ctenophora, Cnidaria, R2 〈 5%). Still, this study offers a first protocol to estimate global, spatially resolved zooplankton biomass and community composition from in situ imaging observations of individual organisms. The underlying dataset covers a period of 10 years while approaches that rely on net samples utilized datasets gathered since the 1960s. Increased use of digital imaging approaches should enable us to obtain zooplankton biomass distribution estimates at basin to global scales in shorter time frames in the future.

Description: The presence of tipping points in ecological systems implies abrupt changes in the dynamics of the ecosystem. In these piecewise-smooth dynamical systems sliding dynamics, i.e., dynamics on the switching boundary, have been reported for population models. However, the question whether or not, and if so under which conditions, sliding dynamics may occur in an optimally controlled system have not yet been studied. We explore this issue in a simple harvesting model with two regimes, and find that optimal sliding may occur if regular steady states do not exist. Hence, sliding dynamics may be part of an optimal policy.

Description: The effects of climate change (CC) on contaminants and their potential consequences to marine ecosystem services and human wellbeing are of paramount importance, as they pose overlapping risks. Here, we discuss how the interaction between CC and contaminants leads to poorly constrained impacts that affects the sensitivity of organisms to contamination leading to impaired ecosystem function, services and risk assessment evaluations. Climate drivers, such as ocean warming, ocean deoxygenation, changes in circulation, ocean acidification, and extreme events interact with trace metals, organic pollutants, excess nutrients, and radionuclides in a complex manner. Overall, the holistic consideration of the pollutants-climate change nexus has significant knowledge gaps, but will be important in understanding the fate, transport, speciation, bioavailability, toxicity, and inventories of contaminants. Greater focus on these uncertainties would facilitate improved predictions of future changes in the global biogeochemical cycling of contaminants and both human health and marine ecosystems.

Description: The Wadden Sea became a UNESCO World Heritage Site in 2009 owing to its geographical and ecological importance. Given its status and its global recognition, academic understanding of, and engagement with, a diverse set of stakeholders is crucial to the sustainability of the Wadden Sea and the wildlife that inhabit its transnational boundaries. As such, this paper reviews with whom, how, and to what extent the academy has engaged with Wadden Sea stakeholders. This study finds that stakeholder groups (whom, with vested interests in the sea, might be expected to be present) are missing from academic publications focused on stakeholders in the Wadden Sea. Moreover, existing studies tend to focus on singular, categorized stakeholder ‘groups’, and lack transboundary integration, as well as reference to UN Sustainability Goal 14 – a key target for environmental protection. In sum, the review provides (1) an analysis of academic work that engages Wadden Sea stakeholders to assist future researchers undertaking work in this global ecologically significant area, and (2) a discussion of where future academic work might be developed.

Description: Epibenthic dinoflagellates occur globally and include many toxin-producing species of concern to human health and benthic ecosystem function. Such benthic harmful algal blooms (BHABs) have been well described from tropical and sub-tropical coastal environments, but assessments from north temperate waters, e.g., northern Europe, and polar regions are scarce. The present study addressed the biodiversity and distribution of potentially toxic epibenthic dinoflagellate populations along the west coast of Sweden (Kattegat-Skagerrak) by morphological and molecular criteria. Morphological analysis conducted by light- and electron-microscopy was then linked by DNA barcoding of the V4 region of 18S rRNA gene sequences to interpret taxonomic and phylogenetic relationships. The presence of two potentially toxigenic epibenthic dinoflagellates, Prorocentrum lima (Ehrenberg) F.Stein and Coolia monotis Meunier was confirmed, along with a description of their spatial and temporal distribution. For P. lima, one third of the cell abundance values exceeded official alarm thresholds for potentially toxic BHAB events (〉1000 cells gr–1 of macroalgae fresh weight). The same species were recorded consecutively for two summers, but without significant temporal variation in cell densities. SEM analyses confirmed the presence of other benthic Prorocentrum species: P. fukuyoi complex, P. cf. foraminosum and P. cf. hoffmannianum. Analyses of the V4 region of the 18S rRNA gene also indicated the presence P. compressum, P. hoffmannianum, P. foraminosum, P. fukuyoi, and P. nanum. These findings provide the first biogeographical evidence of toxigenic benthic dinoflagellates along the west coast of Sweden, in the absence of ongoing monitoring to include epibenthic dinoflagellates. Harmful events due to the presence of Coolia at shellfish aquaculture sites along the Kattegat-Skagerrak are likely to be rather marginal because C. monotis is not known to be toxigenic. In any case, as a preliminary assessment, the results highlight the risk of diarrhetic shellfish poisoning (DSP) events caused by P. lima, which may affect the development and sustainability of shellfish aquaculture in the region.

Description: Community engagement for disaster risk reduction has become central to participatory emergency management. In neoliberal contexts, publics are increasingly portrayed as responsible for preparing and responding to disasters, while at the same time and contradictorily, they are engaged by the state to encourage compliance with top-down policies and directives. This is happening while incremental budget cuts reinforce the operationalisation of community engagement as information dissemination and service delivery. In this paper we scrutinize the ways in which community engagement for disaster risk reduction has been governed and translated into practice in Australia, focusing on the experiences of the practitioners and community representatives doing community engagement in a peri-urban and multi-hazard area of Victoria. We identify and discuss the role of connectors—individuals fostering connections within and among state-led emergency services, local government, and publics—in negotiating change and building relationships. Our analysis shows how the political economy of state-led emergency management hinders the efforts of connectors, contributing to disconnection between publics, community representatives, and emergency agencies. In navigating the bureaucratic, temporal, and financial constraints of state-led community engagement, the emergency sector is missing opportunities to listen, learn, and work with connectors. The result is missed opportunities to build meaningful connections with publics for disaster risk reduction.

Description: The marine dinoflagellate Alexandrium Halim represents perhaps the most significant and intensively studied genus with respect to species diversity, life history strategies, toxigenicity, biogeographical distribution, and global magnitude and consequences harmful algal blooms (HABs). The socioeconomic impacts, environmental and human health risks, and mitigation strategies for toxigenic Alexandrium blooms have also been explored in recent years. Human adaptive actions based on future scenarios of bloom dynamics and shifts in biogeographical distribution under climate-change parameters remain under development and not yet implemented on a regional scale. In the CoCliME (Co-development of climate services for adaptation to changing marine ecosystems) project these issues were addressed with respect to past, current and anticipated future status of key HAB genera and expected benefits of enhanced monitoring. Data on the distribution and frequency of Alexandrium blooms related to paralytic shellfish toxin (PST) events from key CoCliME Case Study areas, comprising the North Sea and adjacent Kattegat-Skagerrak, Norwegian Sea, and Baltic Sea, and eastern North Atlantic marginal seas, were evaluated in a contemporary and historical context over the past several decades. The first evidence of possible biogeographical expansion of Alexandrium taxa into eastern Arctic gateways was provided from DNA barcoding signatures. Various key climate change indicators, such as salinity, temperature, and water-column stratification, relevant to Alexandrium bloom initiation and development were identified. The possible influence of changing variables on bloom dynamics, magnitude, frequency and spatial and temporal distribution were interpreted in the context of regional ocean climate models. These climate change impact indicators may play key roles in selecting for the occurrence and diversity of Alexandrium species within the broader microeukaryote communities. For example, shifts to higher temperature and lower salinity regimes predicted for the southern North Sea indicate the potential for increased Alexandrium blooms, currently absent from this area. Ecological and socioeconomic impacts of Alexandrium blooms and effects on fisheries and aquaculture resources and coastal ecosystem function are evaluated, and, where feasible, effective adaptation strategies are proposed herein as emerging climate services.

Description: Wildfires play an essential role in the ecology of boreal forests. In eastern Siberia, fire activity has been increasing in recent years, challenging the livelihoods of local communities. Intensifying fire regimes also increase disturbance pressure on the boreal forests, which currently protect the permafrost beneath from accelerated degradation. However, long-term relationships between changes in fire regime and forest structure remain largely unknown. We assess past fire-vegetation feedbacks using sedimentary proxy records from Lake Satagay, Central Yakutia, Siberia, covering the past c. 10,800 years. Results from macroscopic and microscopic charcoal analyses indicate high amounts of burnt biomass during the Early Holocene, and that the present-day, low-severity surface fire regime has been in place since c. 4,500 years before present. A pollen-based quantitative reconstruction of vegetation cover and a terrestrial plant record based on sedimentary ancient DNA metabarcoding suggest a pronounced shift in forest structure toward the Late Holocene. Whereas the Early Holocene was characterized by postglacial open larch-birch woodlands, forest structure changed toward the modern, mixed larch-dominated closed-canopy forest during the Mid-Holocene. We propose a potential relationship between open woodlands and high amounts of burnt biomass, as well as a mediating effect of dense larch forest on the climate-driven intensification of fire regimes. Considering the anticipated increase in forest disturbances (droughts, insect invasions, and wildfires), higher tree mortality may force the modern state of the forest to shift toward an open woodland state comparable to the Early Holocene. Such a shift in forest structure may result in a positive feedback on currently intensifying wildfires. These new long-term data improve our understanding of millennial-scale fire regime changes and their relationships to changes of vegetation in Central Yakutia, where the local population is already being confronted with intensifying wildfire seasons.

Description: Over the past decade, a series of airborne experiments in the Arctic and Antarctica explored microwave emission from sea ice and ice sheets at frequencies from 0.5 to 2 GHz. The experiments were motivated by the fact that lower frequencies penetrate deeper into a frozen surface, thus offering the possibility to measure physical temperatures at great depths in ice sheets and, subsequently, other unique geophysical observables including sea ice salinity. These experiments were made feasible by recent engineering advances in electronics, antenna design, and noise removal algorithms when operating outside of protected bands in the electromagnetic spectrum. These technical advances permit a new type of radiometer that not only operates at low frequency, but also obtains continuous spectral information over the band from 0.5 to 2 GHz. Spectral measurements facilitate an understanding of the physical processes controlling emission and also support the interpretation of results from single frequency instruments. This paper reviews the development of low-frequency, wide band radiometry and its application to cryosphere science over the past 10 years. The paper summarizes the engineering design of an airborne instrument and the associated algorithms to mitigate radio frequency interference. Theoretical models of emission built around the morphologic and electrical properties of cryospheric components are also described that identify the dominant physical processes contributing to emission spectra. New inversion techniques for geophysical parameter retrieval are summarized for both Arctic and Antarctic scenarios. Examples that illustrate how the measurements are used to inform on glaciological problems are presented. The paper concludes with a description of new instrument concepts that are foreseen to extend the technology into operation from space.

Description: The redox speciation of iron was determined during the iron fertilization LOHAFEX and for the first time, the chemiluminescence assay of filtered and unfiltered samples was systematically compared. We hypothesize that higher chemiluminescence in unfiltered samples was caused by Fe(II) adsorbed onto biological particles. Dissolved and particulate Fe(II) increased in the mixed layer steadily 6-fold during the first two weeks and decreased back to initial levels by the end of LOHAFEX. Both Fe(II) forms did not show diel cycles downplaying the role of photoreduction. The chemiluminescence of unfiltered samples across the patch boundaries showed strong gradients, correlated significantly to biomass and the photosynthetic efficiency and were higher at night, indicative of a biological control. At 150 m deep, a secondary maximum of dissolved Fe(II) was associated with maxima of nitrite and ammonium despite high oxygen concentrations. We hypothesize that during LOHAFEX, iron redox speciation was mostly regulated by trophic interactions.