Ecophysiology and ecological impacts of an Antarctic invader: the chironomid, Eretmoptera murphyi.

Antarctica has entered a period of rapid, and potentially drastic, change. The combined pressures of anthropogenic climate change, which disproportionately affects the polar regions, and an increase in human activity and connectivity in and around the Antarctic, is opening the least invaded continent on the planet to new species. As ice retreats, terrestrial habitats ripe for colonisation by both humans and non native species are increasing, and so must our knowledge of the biology, ecology and impact of invading species. This thesis explores these issues through the model invasive species, the chironomid, Eretmoptera murphyi Schaeffer (Diptera: Chironomidae), which has successfully colonised Signy Island in the maritime Antarctic, following introduction by humans in the 1960s. Through whole organism experiments and field observations, we confirm parthenogenesis and adult emergence throughout summer on Signy. Physiological studies are employed to assess the midge’s potential to establish further south, and/or cope with climate change. Differing responses to temperature are identified in different life stages, which at various points in the life cycle must endure microclimate temperatures from +30 ºC to -20 ºC, on Signy Island. The impact of microhabitat temperature and moisture conditions on development and overwintering survival is examined, with oviposition sites found to be an important factor in determining reproductive success, especially considering a warming climate. The extent of E. murphyi’s distribution on Signy is updated, doubling previous estimates of its range, and finding that it is on the brink of moving into new valley systems. Where it occurs, the midge is capable of increasing soil nitrates by as much as five times the background levels, bringing nitrogen levels up to that seen in association with seal colonies. As the only true insect on the island, and a significant detritivore, E. murphyi has the potential to affect change to local vegetation and is arguably a new keystone species in this nutrient-poor ecosystem. Existing biosecurity measures in place seem unlikely to limit its spread which appears to be tracking footpaths used by researchers on the island. Larval stages are also able to survive several weeks in sea water, suggesting there is little impediment to its eventual colonisation of other islands and the Antarctic Peninsula, where it would likely flourish. This body of work encompasses a range of disciplines from whole organism biology through to ecosystem function, and highlights the impact that a single, and seemingly innocuous invasive species can have on an Antarctic terrestrial ecosystem

Surviving the Antarctic winter - Life stage cold tolerance and ice entrapment survival in the invasive chironomid midge Eretmoptera murphyi.

An insect’s ability to tolerate winter conditions is a critical determinant of its success. This is true for both native and invasive species, and especially so in harsh polar environments. The midge Eretmoptera murphyi (Diptera, Chironomidae) is invasive to maritime Antarctic Signy Island, and the ability of fourth instar larvae to tolerate freezing is hypothesized to allow the species to extend its range further south. However, no detailed assessment of stress tolerance in any other life stage has yet been conducted. Here, we report that, although larvae, pupae and adults all have supercooling points (SCPs) of around −5 °C, only the larvae are freeze-tolerant, and that cold-hardiness increases with larval maturity. Eggs are freeze-avoiding and have an SCP of around −17 °C. At −3.34 °C, the CTmin activity thresholds of adults are close to their SCP of −5 °C, and they are likely chill-susceptible. Larvae could not withstand the anoxic conditions of ice entrapment or submergence in water beyond 28 d. The data obtained here indicate that the cold-tolerance characteristics of this invasive midge would permit it to colonize areas further south, including much of the western coast of the Antarctic Peninsula

Life cycle and phenology of an Antarctic invader – the flightless chironomid midge, Eretmoptera murphyi

Knowledge of the life cycles of non-native species in Antarctica is key to understanding their ability to establish and spread to new regions. Through laboratory studies and field observations on Signy Island (South Orkney Islands, maritime Antarctic), we detail the life stages and phenology of Eretmoptera murphyi (Schaeffer 1914), a brachypterous chironomid midge introduced to Signy in the 1960s from sub-Antarctic South Georgia where it is endemic. We confirm that the species is parthenogenetic and suggest that this enables E. murphyi to have an adult emergence period that extends across the entire maritime Antarctic summer season, unlike its sexually reproducing sister species Belgica antarctica which is itself endemic to the Antarctic Peninsula and South Shetland Islands. We report details of previously undescribed life stages, including verification of four larval instars, pupal development, egg gestation and development, reproductive viability and discuss potential environmental cues for transitioning between these developmental stages. Whilst reproductive success is limited to an extent by high mortality at eclosion, failure to oviposit and low egg-hatching rate, the population is still able to potentially double in size with every life cycle

Not so free range? Oviposition microhabitat and egg clustering affects Eretmoptera murphyi (Diptera: Chironomidae) reproductive success

Understanding the physiology of non-native species in Antarctica is key to elucidating their ability to colonise an area, and how they may respond to changes in climate. Eretmoptera murphyi is a chironomid midge introduced to Signy Island (Maritime Antarctic) from South Georgia (Sub-Antarctic) where it is endemic. Here, we explore the tolerance of this species’ egg masses to heat and desiccation stress encountered within two different oviposition microhabitats (ground surface vegetation and underlying soil layer). Our data show that, whilst oviposition takes place in both substrates, egg sacs laid individually in soil are at the greatest risk of failing to hatch, whilst those aggregated in the surface vegetation have the lowest risk. The two microhabitats are characterised by significantly different environmental conditions, with greater temperature fluctuations in the surface vegetation, but lower humidity (%RH) and available water content in the soil. Egg sacs were not desiccation resistant and lost water rapidly, with prolonged exposure to 75% RH affecting survival for eggs in singly oviposited egg sacs. In contrast, aggregated egg sacs (n = 10) experienced much lower desiccation rates and survival of eggs remained above 50% in all treatments. Eggs had high heat tolerance in the context of the current microhabitat conditions on Signy. We suggest that the atypical (for this family) use of egg sac aggregation in E. murphyi has developed as a response to environmental stress. Current temperature patterns and extremes on Signy Island are unlikely to affect egg survival, but changes in the frequency and duration of extreme events could be a greater challenge

Moving out of town? The status of alien plants in high‐Arctic Svalbard, and a method for monitoring of alien flora in high‐risk, polar environments

Abstract Rising human activity in the Arctic, combined with a warming climate, increases the probability of introduction and establishment of alien plant species. While settlements are known hotspots for persistent populations, little is known about colonization of particularly susceptible natural habitats. Systematic monitoring is lacking and available survey methods vary greatly. Here, we present the most comprehensive survey of alien vascular plant species in the high‐Arctic archipelago of Svalbard to date, aimed at (i) providing a status within settlements; (ii) surveying high‐risk habitats such as those with high visitor numbers and nutrient enrichment from sea bird colonies; (iii) presenting a systematic monitoring method that can be implemented in future work on alien plant species in Arctic environments; and (iv) discuss possibilities for mapping alien plant habitats using unmanned aerial vehicles. The systematic grid survey, covering 1.7 km2 over three settlements and six bird cliffs, detected 36 alien plant species. Alien plant species were exclusively found in areas of human activity, particularly areas associated with current or historic animal husbandry. The survey identified the successful eradication of Anthriscus sylvestris in Barentsburg, as well as the rapid expansion of Taraxacum sect. Ruderalia over the last few decades. As there is currently no consistent method for monitoring alien plant species tailored to polar environments, we propose a systematic methodology that could be implemented within a structured monitoring regime as part of an adaptive monitoring strategy towards alien species in the Arctic

Carbon storage in Norwegian ecosystems (revised edition)

Bartlett, J., Rusch, G.M., Kyrkjeeide, M.O., Sandvik, H. & Nordén, J. 2020. Carbon storage in Norwegian ecosystems (revised edition). NINA Report 1774b. Norwegian Institute for Nature Research. This report discusses approximate estimations of the carbon budgets within Norway’s mainland ecosystems. It stands as an initial overview of the natural potential of carbon storage and sequestration in Norwegian ecosystems. We describe carbon cycling in five key ecosystem groups: forest, alpine and cryosphere, agriculture and grassland, wetland, and freshwater and nearshore ecosystems. We emphasise the vital ecosystem service that Norwegian landscapes and ecosystems provide in sequestering carbon, and how climate change and management practices may aggravate or mitigate this function. We find that the largest stores of carbon in Norway are in the forests (32%) which also cover 38% of the total land area. Wetlands and permafrost cover 9% and 3% of the total land mass respectively, yet are storing over 2.2 Pg C, 31% of the nation’s carbon. These two ecosystems are the most carbon dense ecosystems per km2, with 53 and 48 kg C m−2 for wetlands and permafrost respectively. The next densest storage of carbon can be found in freshwater lake sediments, with 45 kg C m−2, amounting to 13% of all carbon stores. Forests and low-mid alpine zones sequester the most carbon on an annual basis (5.5 and 5.3 Tg C yr−1, respectively), with soils in alpine heathlands contributing the most to alpine carbon stores. In considering the carbon stored in key ecosystems, we find that Norway contains approximately 0.18% of all global carbon stocks, with a land mass that is 0.07% of the planet. This high carbon-to-area ratio is likely due to the large proportion of the country that is carbon rich peatlands (alpine and lowland) and boreal forest. Since ratifying the Paris Agreement, Norway has pledged to become carbon neutral by 2050, yet is presently one of the highest CO2/CO2-e emitters per capita in Europe, and within the top 20% of emitters globally. The main terrestrial ecosystems that are included in the emissions reporting system for Norway include forest, arable land and farm grazing land, infrastructure areas, and a small portion of the total area of mire, as well as land-use changes among these areas. However, a large portion of the remaining land area in Norway is to a limited extent included in the accounting, although its carbon emissions and sink capacity can be significantly affected by management practices and/or conversion. Currently non-managed areas such as wetlands, alpine zones, freshwater sediments, habitats included in non-agricultural open lowland classes, and the cryosphere including permafrost, are not adequately considered in carbon reporting, especially due to limitations in area representation and knowledge gaps concerning carbon uptake, storage and emissions in these systems, and concerning the consequences of land use change on carbon stocks. These areas account for more than half of the land cover of Norway and could account for approximately 68% of the nation’s carbon stores. Additionally, coastal ecosystems, such as kelp forests are also not included, yet play a key role in both carbon budgets and bio-diversity measures. The Intergovernmental Panel on Climate Change (IPCC) finds that the conservation and enhancement of carbon sinks and natural carbon stores is one of the surest ways for us to com-bat the extremes of climate change. The most efficient and cost-effective process is by using existing ecosystems. Current national inventories do consider the changes in land use, and how this may impact carbon emissions. However, much of the regularly assessed land types are biased towards managed ecosystems, and there is currently no framework for how to incorporate impacts on biodiversity. The loss of biodiversity is accelerating, and that has negative consequences for populations, species, communities and ecosystems, and thus ecosystem services, including those underpinning the capacity for climate mitigation and adaptation. The recent reports from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES Global Assessment 2019) and the Intergovernmental Panel for Climate Change (IPCC Land Report 2019) both point to biodiversity and ecosystems as underpinning climate actions. They also emphasise the necessity of developing mixes of instruments that make best use of synergistic opportunities that can motivate land-owners and other decision-makers to make decisions that both conserve biodiversity and ecosystem integrity and deliver high levels of ecosystem services. The latter includes reduced greenhouse gas emissions and increased removals. Ensuring a diverse portfolio of healthy ecosystems, either through conservation of already existing ones or by restoring degraded ones, will have the greatest value of ecosystem services and ensure the highest chance of adaptability to climate change pressures in the future. The ability of non-managed and seemingly unproductive ecosystems, such as alpine landscapes, to sequester and store carbon is significant. We suggest that, in addition to a ‘Klimakur’ (“climate cure”), there is a need for a ‘Naturkur’ (“nature cure”) to implement a strategy for biodiversity and ecosystem services following-up the findings and recommendations from the Intergovernmental Science-Policy Platform on Bio-diversity and Ecosystem Services (IPBES), the new international commitments under the Bio-diversity Convention (CBD), and the national implementation of the Norwegian “Nature for Life” white paper (Meld. St. 14 (2015-2016), Ministry of Climate and Environment 2015). A Naturkur would emphasise the value of maintaining a diverse portfolio of ecosystems at a national level, ecosystems that are inextricably interlinked with carbon storage, sequestration capacity and bio-diversity itself, and of finding solutions that can help achieve multiple objectives by proposing synergistic measures. Or rather, a harmonized Klima-Naturkur, where actions for climate mitigation and adaptation, and for biodiversity and ecosystem services conservation are not designed independently, but address societal challenges in a coordinated manner, are synergistic, and reinforce each other to achieve multiple benefits.Bartlett, J., Rusch, G., Kyrkjeeide, M.O., Sandvik, H. & Nordén, J. 2020. Karbonlagring i norske økosystemer (revidert utgave). NINA Rapport 1774b. Norsk institutt for naturforskning. Denne rapporten presenterer omtrentlige estimater av karbonbudsjettene i Fastlands-Norges økosystemer. Den gir en innledende oversikt over det naturlige potensialet for karbonopptak og -lagring i norske økosystemer. Vi beskriver karbonkretsløpet i fem viktige økosystemgrupper: skog, fjell (inkl. kryosfære), åpent lavland (inkl. jordbruksareal), våtmark og ferskvann/kyst. Vi fremhever den viktige økosystemtjenesten som norske landskap og økosystemer yter ved å lagre og binde karbon, og hvordan klimaendringer og forvaltningspraksis kan forverre eller dempe denne funksjonen. Våre estimater viser at det største karbonlageret i Norge ligger i skog (32 %), som også dekker 38 % av det totale landarealet. Våtmark og permafrost dekker henholdsvis 10 % og 3 % av den totale landmassen, men lagrer allikevel over 2,2 Pg C, som tilsvarer 31 % av landets karbon. Disse to økosystemene er de mest karbontette økosystemene per km2, med henholdsvis 53 og 48 kg C m−2 for våtmarker og permafrost. I innsjøsedimenter finnes 45 kg C m−2, som utgjør 13 % av all karbonlagring. Skog og lav- og mellomalpin sone tar opp mest karbon på årsbasis (henholdsvis 5,5 og 5,3 Tg C per år), med alpine lyngheier som natur-typen som bidrar mest i fjellets karbonlager. Våre estimater viser at Norge totalt har omtrent 0,18 % av de globale karbonlagrene, med en landmasse som tilsvarer 0,07 % av jordoverflaten. Dette skyldes sannsynligvis den høye dekningen av karbonrike myrer og boreale skoger. Siden godkjenningen av Parisavtalen har Norge forpliktet seg til å bli karbonnøytral innen 2050, men har i dag et av de høyeste CO2(-ekvivalent)-utslippene per innbygger i Europa og er dermed blant de 20 % av verdens land med høyest utslipp. Utslippsrapporteringssystemet for Norge omfatter (bruksendringer i) produktiv skog, jordbruks- og beitemark, infrastrukturområder og en liten del av det totale myrområdet. En stor del av Norges øvrige arealer er bare i begrenset grad omfattet av karbonregnskapet, selv om forvaltning og/eller bruksendringer har stor betydning for deres karbonutslipp og -opptaksevne. For øyeblikket tar f.eks. ikke karbonrapportering og areal-statistikk tilstrekkelig høyde for ikke-forvaltede arealer, fordi det ikke finnes noen systematiske målinger av karbon for hele økosystemet, og fordi størrelsen på endringene i økosystemenes karbon som skyldes bruksendringer, er dårlig kjent. Dettet gjelder bl.a. våtmarker, permafrost, alpine soner, ferskvannssedimenter eller åpent lavland utenom landbruksareal. Disse områdene utgjør mer enn halvparten av Norges areal og kan utgjøre omtrent 68 % av landets karbonlager. Heller ikke kystøkosystemer som tareskog er inkludert, selv om disse spiller en nøkkelrolle for både karbonbudsjetter og biologiske mangfold. Ifølge FNs klimapanel (IPCC) er bevaring og forbedring av naturlige karbonfangere og karbonlagre en av de sikreste måtene å bekjempe de mest ekstreme klimaendringene på. Den mest kostnadseffektive måten er ved å bruke eksisterende økosystemer. Nåværende nasjonale karbonregnskap vurderer kun endringer i arealbruk og hvordan disse kan påvirke karbonutslipp. Ikke-forvaltede økosystemer er dermed sterkt underrepresentert, og deres betydning for naturmangfold blir heller ikke tatt høyde for. Tapet av biologisk mangfold er akselererende og har negative konsekvenser for bestander, arter, samfunn, økosystemer og dermed økosystem-tjenester. Å sikre et mangfold av økosystemer med god tilstand, enten ved å bevare uberørte naturtyper eller ved å restaurere degradert natur, vil sikre den største verdien av økosystem-tjenester og tilpasningsevnen til klimaendringer. Ikke-forvaltede og tilsynelatende uproduktive økosystemer, som alpine naturtyper og våtmarker, har en betydelig evne til å binde og lagre karbon. Vi foreslår at det i tillegg til klimakur utredes en tilsvarende naturkur. Målet bør være å implementere norsk handlingsplan for naturmangfold (Meld. St. 14 (2015-2016)), følge opp funn og anbefalinger fra det internasjonale naturpanelet (IPBES) og de nye globale målene som skal vedtas av konvensjonen om biologisk mangfold (CBD) i oktober 2020. En naturkur vil kunne bidra til at Norge opprettholder et mangfold av økosystemer i god økologisk tilstand, noe som er svært viktig for lagring og opptak av karbon. Naturkur bør blant annet inneholde en oversikt over tiltak og løsninger som er bra for både naturmangfold og klima. En slik utredning bør inneholde særskilte kapitler som kombinerer klima- og naturkur, hvor tiltak for klimatilpasning og bevaring av biologisk mangfold og økosystemtjenester ses i sammenheng, gir synergier og forsterker hverandre. En norsk oppsummering av rapporten er publisert i NINA Temahefte 76b (https://hdl.handle.net/ 11250/2655582)