Arctic oceans are undergoing major changes in many of its fundamental physical constituents, such as a shift from multi- to first-year ice, shorter ice-covered periods, increasing freshwater runoff, and warming and alteration in the distribution of water masses. Such changes, often resulting from anthropogenic stressors, have profound impacts on the chemical and biological processes that are at the root of Arctic marine food webs, influencing their structure, function and biodiversity. Yet, much research addressing these on-going changes is practically and financially limited to local scales or rather exploratory by nature, making it imperative to better characterise and understand the structural and functional diversity of ecological systems that contribute to the marine Arctic across larger scales. We aim to offer more insight in the distributions and abundance of macrobenthic species in Arctic seascapes, e.g. bivalves, polychaetes, and crustaceans that live in marine soft bottoms. Building on recent pan-Arctic community data from ~5000 locations, we address a fundamental challenge in Arctic ecological research by employing quantitative methods thus far not feasible. We will use multi-species distribution models that allow determining interactions between species; link functions to environmental characteristics using 4th-corner models. Key is that such approaches link traits and environment without the necessity of including sample locations, holding promise for an approach that translates ecosystem function directly to services; look for indirect interactions and feedbacks between polar benthic macrofauna and ecosystem functioning by employing structural equation models. This enables full inference of spatial diversity patterns of Arctic benthic communities and link community organisation and ecosystem functioning, allowing us to understand the interplay between fine- and broad-scale patterns and processes structuring rapidly changing polar benthic ecosystems.

The response of the terrestrial biosphere to climate change is still largely unknown and represents a key uncertainty in climate change predictions. High latitude regions, including Arctic and boreal ecosystems, constitute a key component of the earth system due to significant soil carbon stocks. High latitude regions are net sources of greenhouse gases, such as methane (CH4) and nitrous oxide (N2O), but there is significant disagreement among flux estimates with further uncertainty due to a rapidly changing environment. Climate change effects are particularly strong during the non-growing season, altering the timing of spring snowmelt, fall freeze-up, and increasing winter temperatures. The changes have significant implications for biogeochemical cycles and ecosystem function across high latitude regions. Despite growing evidence of the importance of non-growing season greenhouse gas emissions, few measurements have been made in pristine Arctic and boreal ecosystems. Non-growing season CH4 emissions can account for 10-100% of annual CH4 flux, while next to nothing is known about emissions of N2O during this period. Process-based models miss non-growing season emissions of CH4, underestimating them by 67% and annual emissions by 25%. I will use complementary observations (WP1), modelling (WP2), and experiments (WP3) to quantify the annual magnitude of CH4 and N2O flux, identify controls on non-growing season flux, and assess why existing models of CH4 flux fail outside of the growing season. Are environmental conditions so different that existing model parameters fail, or is non-growing season biogeochemistry fundamentally different? The overall impact is to shift the paradigm from “nothing happens outside of the growing season” to “capturing non-growing season processes is key to understanding ecosystem dynamics.” Ultimately, results will provide novel insights into greenhouse gas budgets and transform our understanding of fundamental earth system dynamics.

The ability of phytoplankton to access the micronutrient iron fuels vast marine ecosystems, drives biogeochemical cycles and influences climate on a planetary scale. Recent studies in the model diatom Phaeodactylum tricornutum have revealed that high-affinity iron uptake uses a carbonate-dependent phytotransferrin which is highly sensitive to ocean acidification. This project seeks to validate and extend the hypothesis that ocean acidification negatively affects the growth of marine phytoplankton by interfering with this carbonate sensitive uptake mechanism. The influence of acidification on iron uptake rates will be characterized in a number of environmentally relevant and phylogenetically diverse strains of phytoplankton, and results will be confirmed using a combination of reverse genetics and environmental validation. The resulting chemical, biological and rate-constant data will be integrated into large-scale biogeochemical Ocean General Circulation Models, which will allow us to place these results into ecological context. This project will transfer cutting-edge molecular techniques and genomic analyses to the host institution while training the experienced researcher in key analytical and biogeochemical modeling methods. Capacity-building courses in project management and opportunities for communication are planned to further develop the future potential of the researcher. Because of the outsized role that iron-limited phytoplankton have in biogeochemical cycles and the sequestration of carbon dioxide, the multidisciplinary outputs of this action are expected to be of high impact and broad interest to a wide array of disciplines, including biogeochemists, climate modelers, policy makers and resource managers.