The return of the white-tailed eagle: Ecology of predator-prey relationships in the Baltic Sea and Arctic inland

Apex predators regulate ecosystems through top-down processes. In the last century many predator populations crashed due to anthropogenic impacts, but recently some have recovered and are re-colonizing old areas, as well as expanding to new suitable habitats. Rapid loss or return of apex predators can destabilize ecosystems and cause consequences for their prey species as well as for livestock. In the Baltic Sea area, the white-tailed eagle (Haliaeetus albicilla) was virtually absent due to persecution and pollutants during the mid-20th century. The rapid growth of the eagle population from the 1980s onward initiated by extensive conservation efforts has not only brought the species back from the brink of extinction, but also caused growing predation pressure on its prey species, in particular the common eider (Somateria mollissima), which is the major prey of the eagles in the Åland islands and especially in the outer archipelago. In Lapland in northern Finland, where husbandry of semi-domestic reindeer is a traditional livelihood, concerns are rising that the expanding white-tailed eagle population poses a threat to reindeer calves. As top predators, the white-tailed eagles are sensitive to bioaccumulating hazardous substances. Despite the decreased levels of pollutants, the Baltic Sea is still the world’s most heavily polluted sea, while mercury levels in the major water bodies in Lapland, two artificial water reservoirs, are higher than in the Baltic. For successful conservation of both the white-tailed eagle and its prey species research is needed regarding the diet of the eagles and the mechanisms shaping the diet. This system also provides an opportunity to study the predator-prey dynamics following the rapid return of an apex predator to a system from where it has been virtually absent. In this thesis I cover (i) the prey use and nesting habitat choice of white-tailed eagles nesting in the Finnish coast and Lapland, (ii) the connections between the prey use and the nesting habitat, (iii) the use of reindeer calves as prey, (iv) the association between nesting white-tailed eagles and the spatiotemporal population trends of the common eider, and (v) the consequences of prey use and nesting site choice on the mercury burden in white-tailed eagle nestlings in Lapland. I found that the prey use of white-tailed eagles changed in time in the archipelago, and that it both in the archipelago and in the inland was influenced by the habitat in the nesting territories, which reflects the occurrence of prey species. In the inland, the white-tailed eagles preferred territories with higher proportions of lakes, peatbogs, and marshlands, which coincides with the higher occurrence of their preferred food source, fish. In the archipelago the main prey of the white-tailed eagles was common eider, which population in the Baltic has declined rapidly since a peak in 1997. The spatiotemporal changes in the core of the eider population distribution were influenced by the proximity of nesting white-tailed eagles. The eiders declined most in the outer archipelago and on unforested islands in the proximity of eagle nest. On the contrary, the population increased in the inner archipelago in areas with eagle nests. Finally, the prey use and nesting habitats influenced the eagles themselves. Elevated mercury burdens in white-tailed eagle nestlings in Lapland were linked with a diet on high trophic-level species and especially pike, the most important prey species in the area, as well as the proximity to a point source; the artificial reservoir of Porttipahta. As flexible opportunists, the white-tailed eagles should not be food-deprived even though some prey species would decline. Likewise, the prey species should not be over-exploited, as the eagles use alternative prey species when a species decline. Population-level eagle-induced shifts has moved the core of the eider population towards safer nesting environments in the inner archipelago. However, the very rapid decrease of eiders calls for close monitoring and conservation efforts of the species. As top predators, the white-tailed eagles are prone to accumulation of pollutants and are as such excellent sentinel species for environmental pollution. However, consequently they are also vulnerable and thus, even though the population today is viable, a continuum of the thorough monitoring of the white-tailed eagles is important. The ecosystem resilience is today severely challenged by anthropogenic impacts. Returning apex predators can improve the states of the ecosystems by e.g. preventing over-grazing, controlling the growth of prey populations and restricting invasive mesopredators. Successful co-existence with humans requires a general acceptance of the predators which only can be gained through cooperation and involvement of stakeholders and inhabitants that are affected by the matter. Merikotkan paluu: Peto-saalissuhteen ekologiaa Itämerellä ja Lapissa Huippupedot säätelevät ekosysteemejä ylemmiltä trofiatasoilta alaspäin suuntautuvilla prosesseilla. Monien huippupetojen kannat romahtivat viime vuosisadalla ihmistoiminnan takia, mutta hiljattain joidenkin petojen kannat ovat elpyneet. Uudet yksilöt asettuvat usein samoille alueille, joilla laji alun perin esiintyi, mutta laajentavat myös asuinaluetta uusiin sopiviin elinympäristöihin. Huippupetojen äkillinen häviäminen tai paluu voi horjuttaa ekosysteemejä ja muutokset voivat aiheuttaa seurauksia sekä luontaisille saalislajeille että tuotantoeläimille. Merikotka (Haliaeetus albicilla) hävisi vainon ja ympäristömyrkkyjen takia lähes kokonaan Itämereltä 1900-luvun puoliväliin mennessä. Laajan suojelutyön tuloksena merikotkakanta elpyi ja kanta lähti nopeaan kasvuun 1980-luvulla, aiheuttaen samalla kasvavaa saalistuspainetta saalislajeille ja erityisesti haahkalle (Somateria mollissima), joka on merikotkan tärkein saalislaji Ahvenanmaalla, varsinkin ulkosaaristossa. Lapissa, jossa poronhoito on perinteinen elinkeino, merikotkakannan runsas kasvu on aiheuttanut huolta siitä, että merikotkat uhkaavat poronvasoja. Huippupetoina merikotkat itse ovat herkkiä elimistöön kertyville haitallisille aineille. Vaikka Itämeren myrkkypitoisuudet ovat laskeneet, Itämeri on edelleen maailman saastunein meri. Lapissa puolestaan elohopeatasot alueen suurimmissa vesistöissä, Porttipahdan ja Lokan tekoaltaissa, ovat korkeammat kuin Itämerellä. Sekä merikotkan että sen saalislajien suojelun turvaamiseksi tarvitaan tutkimustietoa merikotkan ravinnosta ja sitä säätelevistä mekanismeista. Merikotkan paluu tarjoaa samalla ainutlaatuisen mahdollisuuden tutkia pedon ja saaliin välistä dynamiikkaa järjestelmässä, jossa peto palaa alueelle, josta se on käytännössä puuttunut usean vuosikymmenen ajan. Väitöskirjassani käsittelen (i) pesivien merikotkien saaliinkäyttöä ja pesimäympäristön maisemarakennetta Suomen rannikolla ja Lapissa, (ii) pesimäympäristön maisemarakenteen vaikutusta saalislajien esiintyvyyteen, (iii) poronvasojen esiintyvyyttä saaliissa, (iv) pesivien merikotkien yhteyttä haahkakannan paikallisiin ja ajallisiin muutoksiin, sekä (v) ravintolajien ja pesimäympäristön vaikutusta Lapin merikotkanpoikasten elohopeakuormitukseen. Havaitsin, että merikotkien käyttämissä saalislajeissa oli ajallista vaihtelua Ahvenanmaalla, ja että eri saalislajien osuudet sekä saaristossa että sisämaassa olivat kytköksissä pesimäreviirien elinympäristöihin. Sisämaassa merikotkat suosivat reviirejä, joissa suurempi osuus kuin maisemassa keskimäärin koostui järvistä, kosteikoista ja avosoista. Merikotkat valitsivat näin ollen elinympäristöjä, joissa niiden ensisijaisen saaliin, kalan, saatavuus on paras. Saaristossa merikotkien tärkein saalislaji oli haahka, jonka Itämeren kanta on laskenut voimakkaasti vuoden 1997 huippulukemista. Pesivien merikotkien läheisyydellä oli vaikutusta haahkakannan painopisteen ajalliseen ja paikalliseen muutokseen. Haahkamäärät vähenivät eniten ulkosaaristossa ja puuttomilla saarilla merikotkanpesien läheisyydessä. Sisäsaaristossa haahkakanta sen sijaan vahvistui alueilla, joilla pesi merikotkia. Saalislajeilla ja pesimäympäristön valinnalla oli vaikutusta myös itse merikotkiin. Saalislajien koostumus vaikutti Lapissa kuoriutuneiden merikotkanpoikasten kohonneisiin elohopeapitoisuuksiin. Korkeimmat pitoisuudet havaittiin poikasilla, joiden ravinto koostui korkean trofiatason saalislajeista, erityisesti alueen tärkeimmästä saalislajista hauesta. Toinen elohopeatasoja korottava tekijä oli pesän läheisyys paikalliseen kuormituslähteeseen, Porttipahdan tekoaltaaseen. Joustavina opportunisteina merikotkat eivät kärsine ravinnonpuutteesta, vaikka joidenkin saalislajien populaatiot vähenisivätkin. Vastaavasti yksittäisiin saalislajeihin kohdistuva saalistuspaine ei kasvane ylisuureksi, koska merikotkat siirtyvät vaihtoehtoisiin saalislajeihin, jos jonkin lajin saatavuus vähenee. Haahkakannan painopiste on merikotkien vaikutuksesta siirtynyt sisäsaaristoon päin, eli pesimäympäristöihin, joissa saalistuspaine on matalampi. Haahkakannan nopea romahdus edellyttää kuitenkin kannan tarkkaa seurantaa ja suojelutoimenpiteitä. Huippupetoina merikotkat kerryttävät herkästi ympäristömyrkkyjä, ja soveltuvat täten erinomaisesti indikaattorilajeiksi ympäristömyrkkyjen seurantaan mutta ovat siksi myös haavoittuvia. Vaikka merikotkapopulaatio tällä hetkellä on elinkelpoinen, kannan huolellisen seurannan jatkaminen on tärkeää. Elinympäristöjen sietokyky on nykyään vakavasti heikentynyt ihmistoiminnan takia. Huippupedot voivat palatessaan parantaa ekosysteemien tilaa mm. estämällä ylilaidunnusta, säätelemällä saaliskantojen kasvua ja rajoittamalla haitallisia vieraslajeja, varsinkin pienpetoja. Onnistunut rinnakkaiselo ihmisten kanssa edellyttää petoeläinten yleistä hyväksyntää, mikä on saavutettavissa vain yhteistyöllä ja osallistamalla petojen vaikutuspiirissä olevat sidosryhmät ja asukkaat

Spatial and dietary sources of elevated mercury exposure in white-tailed eagle nestlings in an Arctic freshwater environment

Human-induced mercury (Hg) contamination is of global concern and its effects on wildlife remain of high concern, especially in environmental hotspots such as inland aquatic ecosystems. Mercury biomagnifies through the food web resulting in high exposure in apex predators, such as the white-tailed eagle (Haliaeetus albicilla), making them excellent sentinel species for environmental Hg contamination. An expanding population of white-tailed eagles is inhabiting a sparsely populated inland area in Lapland, northern Finland, mainly around two large reservoirs flooded 50 years ago. As previous preliminary work revealed elevated Hg levels in this population, we measured Hg exposure along with dietary proxies (delta C-13 and delta N-15) in body feathers collected from white-tailed eagle nestlings in this area between 2007 and 2018. Mercury concentrations were investigated in relation to territory characteristics, proximity to the reservoirs and dietary ecology as potential driving factors of Hg contamination. Mercury concentrations in the nestlings (4.97-31.02 mu g g(-1) dw) were elevated, compared to earlier reported values in nestlings from the Finnish Baltic coast, and exceeded normal background levels (40.00 mu g g(-1)). The main drivers of Hg contamination were trophic position (proxied by delta N-15), the dietary proportion of the predatory fish pike (Esox Lucius), and the vicinity to the Porttipahta reservoir. We also identified a potential evolutionary trap, as increased intake of the preferred prey, pike, increases exposure. All in all, we present results for poorly understood freshwater lake environments and show that more efforts should be dedicated to further unravel potentially complex pathways of Hg exposure to wildlife.Peer reviewe

Diet and breeding habitat preferences of White-tailed Eagles in a northern inland environment

Many apex predator populations are recolonizing old areas and dispersing to new ones, with potential consequences for their prey species and for livestock. An increasing population of the White-tailed Eagle (Haliaeetus albicilla) has settled north of the Arctic Circle in northern Finland, mainly at two big water reservoirs but also in areas with mainly terrestrial habitat. We examined nesting habitat preferences and prey use of White-tailed Eagles in this environment, where reindeer husbandry is a traditional livelihood and concerns are rising that the growing White-tailed Eagle population poses a threat to reindeer calves. Lakes, peat bogs, and marshlands were preferred habitats in the nesting territories. Fish constituted 64.3% of the identified prey items, with birds accounting for 28.5% and mammals 7.2%. The nesting territory habitat within a 10 km radius and the latitude influenced the prey composition at both the group and species level. The occurrence of reindeer calves as prey increased with latitude but was not associated with any habitat. Knowledge of the diet and territory preferences can be used to predict future dispersal and local prey use of this species. Nesting White-tailed Eagles do not seem to pose a threat to traditional reindeer herding, but further research is needed regarding non-breeding sub-adults and whether the White-tailed Eagles actually kill reindeer calves or simply exploit their carcasses

Spatial and dietary sources of elevated mercury exposure in white-tailed eagle nestlings in an Arctic freshwater environment

Human-induced mercury (Hg) contamination is of global concern and its effects on wildlife remain of high concern, especially in environmental hotspots such as inland aquatic ecosystems. Mercury biomagnifies through the food web resulting in high exposure in apex predators, such as the white-tailed eagle (Haliaeetus albicilla), making them excellent sentinel species for environmental Hg contamination. An expanding population of white-tailed eagles is inhabiting a sparsely populated inland area in Lapland, northern Finland, mainly around two large reservoirs flooded 50 years ago. As previous preliminary work revealed elevated Hg levels in this population, we measured Hg exposure along with dietary proxies (δ13C and δ15N) in body feathers collected from white-tailed eagle nestlings in this area between 2007 and 2018. Mercury concentrations were investigated in relation to territory characteristics, proximity to the reservoirs and dietary ecology as potential driving factors of Hg contamination. Mercury concentrations in the nestlings (4.97–31.02 μg g−1 dw) were elevated, compared to earlier reported values in nestlings from the Finnish Baltic coast, and exceeded normal background levels (≤5.00 μg g−1) while remaining below the tentative threshold of elevated risk for Hg exposure mediated health effect (>40.00 μg g−1). The main drivers of Hg contamination were trophic position (proxied by δ15N), the dietary proportion of the predatory fish pike (Esox lucius), and the vicinity to the Porttipahta reservoir. We also identified a potential evolutionary trap, as increased intake of the preferred prey, pike, increases exposure. All in all, we present results for poorly understood freshwater lake environments and show that more efforts should be dedicated to further unravel potentially complex pathways of Hg exposure to wildlife.</p

"För jag är ju liksom bara 15. Hur ska jag veta vad jag vill bli när jag är 30?" En undersökning om en grupp ungdomars och deras föräldrars tankar kring gymnasievalet, framtiden och betydelsen av deras ursprung

Gymnasievalet är för många ungdomar det första stora val de står inför. Känslorna varierar då många kan känna stor osäkerhet inför valet medan andra har sin levnadsbana utstakad. Det handlar även om begränsningar och möjligheter där den enskilde individens förutsättningar skall vägas mot utbildningssystemet och strukturerna i dagens föränderliga samhälle. I föreliggande examensarbete är syftet att söka kunskap om hur elever med svenskt respektive utländskt ursprung tänker kring sitt gymnasieval, där vi även vägt in föräldrarnas tankar. Vi har genom kvalitativa forskningsintervjuer mött elever och deras föräldrar som står i vägskälet mellan grundskola och gymnasieskola. Vi söker svar på vilka faktorer som påverkar det val de slutligen gör. Vi undersöker även om det etniska ursprunget inverkar på elevernas gymnasieval. Är familjen bärare av kultur och hur inverkar detta på eleven och dennes val? Vårt sammantagna intryck är att påverkansfaktorerna kring gymnasievalet är många. Här har vi sett hur ursprung och livsvillkor präglar eleven, och hur detta möjliggör eller begränsar elevens val till gymnasieskolan. Elevernas egna åsikter är dock att deras etniska ursprung inte påverkar gymnasievalet. Vi har även sett hur elever med utländskt ursprung värderar både gymnasie- och högskoleutbildning högre än vad elever med svenskt ursprung gör, dock känner eleverna med utländskt ursprung större osäkerhet inför valet

Diet and breeding habitat preferences of White-tailed Eagles in a northern inland environment

Abstract Many apex predator populations are recolonizing old areas and dispersing to new ones, with potential consequences for their prey species and for livestock. An increasing population of the White-tailed Eagle (Haliaeetus albicilla) has settled north of the Arctic Circle in northern Finland, mainly at two big water reservoirs but also in areas with mainly terrestrial habitat. We examined nesting habitat preferences and prey use of White-tailed Eagles in this environment, where reindeer husbandry is a traditional livelihood and concerns are rising that the growing White-tailed Eagle population poses a threat to reindeer calves. Lakes, peat bogs, and marshlands were preferred habitats in the nesting territories. Fish constituted 64.3% of the identified prey items, with birds accounting for 28.5% and mammals 7.2%. The nesting territory habitat within a 10 km radius and the latitude influenced the prey composition at both the group and species level. The occurrence of reindeer calves as prey increased with latitude but was not associated with any habitat. Knowledge of the diet and territory preferences can be used to predict future dispersal and local prey use of this species. Nesting White-tailed Eagles do not seem to pose a threat to traditional reindeer herding, but further research is needed regarding non-breeding sub-adults and whether the White-tailed Eagles actually kill reindeer calves or simply exploit their carcasses

Short half-life of HPV16 E6 and E7 mRNAs sensitizes HPV16-positive tonsillar cancer cell line HN26 to DNA-damaging drugs

Here we show that treatment of the HPV16-positive tonsillar cancer cell line HN26 with DNA alkylating cancer drug melphalan-induced p53 and activated apoptosis. Melphalan reduced the levels of RNA polymerase II and cellular transcription factor Sp1 that were associated with HPV16 DNA. The resulting inhibition of transcription caused a rapid loss of the HPV16 early mRNAs encoding E6 and E7 as a result of their inherent instability. As a consequence of HPV16 E6 and E7 down-regulation, the DNA damage inflicted on the cells by melphalan caused induction of p53 and activation of apoptosis in the HN26 cells. The BARD1-negative phenotype of the HN26 cells may have contributed to the failure to repair DNA damage caused by melphalan, as well as to the efficient apoptosis induction. Finally, nude mice carrying the HPV16 positive tonsillar cancer cells responded better to melphalan than to cisplatin, the chemotherapeutic drug of choice for tonsillar cancer. We concluded that the short half-life of the HPV16 E6 and E7 mRNAs renders HPV16-driven tonsillar cancer cells particularly sensitive to DNA damaging agents such as melphalan since melphalan both inhibits transcription and causes DNA damage

Structure–Function Analysis of the Two-Peptide Bacteriocin Plantaricin EF

Plantaricin EF is a two-peptide bacteriocin that depends on the complementary action of two different peptides (PlnE and PlnF) to function. The structures of the individual peptides have previously been analyzed by nuclear magnetic resonance spectroscopy (Fimland, N. et al. (2008), Biochim. Biophys. Acta 1784, 1711−1719), but the bacteriocin structure and how the two peptides interact have not been determined. All two-peptide bacteriocins identified so far contain GxxxG motifs. These motifs, together with GxxxG-like motifs, are known to mediate helix–helix interactions in membrane proteins. We have mutated all GxxxG and GxxxG-like motifs in PlnE and PlnF in order to determine if any of these motifs are important for antimicrobial activity and thus possibly for interactions between PlnE and PlnF. Moreover, the aromatic amino acids Tyr and Trp in PlnE and PlnF were substituted, and four fusion polypeptides were constructed in order to investigate the relative orientation of PlnE and PlnF in target cell membranes. The results obtained with the fusion polypeptides indicate that PlnE and PlnF interact in an antiparallel manner and that the C-terminus of PlnE and N-terminus of PlnF are on the outer part of target cell membranes and the N-terminus of PlnE and C-terminus of PlnF are on the inner part. The preference for an aromatic residue at position 6 in PlnE suggests a positioning of this residue in or near the membrane interface on the cells inside. Mutations in the GxxxG motifs indicate that the G₅xxxG₉ motif in PlnE and the S₂₆xxxG₃₀ motif in PlnF are involved in helix–helix interactions. Atomistic molecular dynamics simulation of a structural model consistent with the results confirmed the stability of the structure and its orientation in membranes. The simulation approved the anticipated interactions and revealed additional interactions that further increase the stability of the proposed structure