Kampamaneettien monimuotoisuudesta ja ekologisesta roolista : esimerkkinä Jää- ja Itämeren Mertensia ovum

Gelatinous zooplankton, such as ctenophores, have attracted attention during the last decade,mainly as a result of the enigma around their potentially increased abundances around the world. Despite the increased attention, they remain either understudied or disregarded in most food web investigations and monitoring programs, and are defined as one of the most difficult groups of pelagic animals to study. Consequently, their diversity and ecological role are often grossly oversimplified and misunderstood, leading to biased views of ecosystem functioning. In addition, ctenophores share traits such as voracious predation behavior, the ability to starve and shrink during periods of low food availability and to tolerate increased temperatures, as well as high reproductive capacity, making them likely to take advantage of changing environmental conditions. In the Arctic, earlier ctenophore data consist of sparse abundance estimates and dietary studies lacking a systematic or integrative approach. In the Baltic Sea, despite the wellestablished routine plankton monitoring program conducted by the surrounding nations, the distribution and the role of the Arctic ctenophore Mertensia ovum in this ecosystem has been unknown since its first reported appearance in 2007. In this thesis, the biodiversity of cydippid ctenophores and their role in Svalbard waters and in the Baltic Sea were studied. Extensive in situ sampling, laboratory experiments, morphological and molecular identification analysis, traditional and molecular gut content analysis, as well as several direct measures of the ctenophores and the pelagic communities they inhabit were combined to address system-specific questions and to better understand how important a role the ctenophores might have in marine ecosystems. A combination of morphological species identification and molecular methods revealed Euplokamis sp. and an unidentified mertensiid species to co-occur with the dominating Mertensia ovum in Arctic waters. Similarly, the first recording of the cydippid ctenophore, Euplokamis sp., near the entrance to the Baltic Sea was reported in conjunction with extensive sampling of Mnemiopsis leidyi and Mertensia ovum. Interestingly, Pleurobrachia pileus, earlier reported to commonly co-occur with M. ovum in the Arctic and be present throughout the Baltic Sea (and earlier reported as the only ctenophore species in the northern Baltic Sea), was not present in either study site. It was demonstrated that morphological species identification alone is insufficient. In addition, the lack of proper species descriptions and public sequences limited the identification to the genus, family or order level. Thus, more emphasis should be placed on combining morphological and molecular methods together with photographic vouchers for rigorous taxonomic identification and accurate species descriptions. The lack of historical survey data and accurate abundance estimates of M. ovum have biased interpretations of its role in the Arctic and Baltic ecosystems. According to the results presented in this thesis, the potential predation impact of M. ovum was high when assuming relatively homogenous distributions of M. ovum and its prey, but it was even higher when patchiness of both predators and prey was taken into account. The potential predation impact was further affected by extensive spatial and seasonal migration patterns. Therefore, to adequately model prey predator interactions, more emphasis should be placed on the fine-scale distribution patterns of predators and prey. Also, different populations of a single species can have very different trophic roles in the food web due to the great difference in body size, as exemplified in this thesis with two populations of M. ovum. In the Arctic, M. ovum is a voracious predator of copepods (Calanus spp.), while in the Baltic, the substantially smaller M. ovum individuals mainly prey upon pico- and microplankton. Thus, generalizing and extrapolating ecological traits such as diet and foraging behavior from one population to another can be misleading. Moreover, the future of the two studied populations of M. ovum is likely to differ substantially because their distribution area will be differently affected by climate change; the distribution area is predicted to diminish in the Baltic Sea and remain more or less constant in the Arctic. To conclude, this thesis demonstrates that our current knowledge on the diversity, role, and potential future changes of the ctenophores in pelagic communities is still very incomplete. Thus, to properly understand the ecological impact of ctenophores at present and in the near future, this thesis suggests that all available techniques need to be applied in species identification, and that clear recommendations for a proper assessment of routine ctenophore monitoring are urgently needed.Hyytelömäisen eläinplanktonin, kuten esimerkiksi kampamaneettien, saama huomio on kasvanut räjähdysmäisesti viimeisen vuosikymmenen aikana. Keskustelua on aiheuttanut lähinnä hyytelöplanktonin mahdollinen maailmanlaajuinen runsastuminen, vaikka tutkijat eivät olekaan tästä yksimielisiä. Kiinnostuksen heräämisestä huolimatta hyytelöplankton on edelleen huonosti tunnettu eläinryhmä. Hyytelöplanktonia ei usein huomioida perinteisissä ravintoverkkotutkimuksissa eikä seurantaohjelmissa, ja sitä pidetäänkin vaikeimmin tutkittavana planktonisena ryhmänä. Näin ollen tieto hyytelöplanktonin monimuotoisuudesta ja ekologisesta roolista on usein joko yksinkertaistettua tai kokonaan väärinymmärrettyä, mikä voi johtaa virheellisiin päätelmiin planktonekosysteemin toiminnasta. Tiedetään kuitenkin, että muun muassa kampamaneetit ovat tehokkaita saalistajia, kykenevät saaliin määrästä riippuen säätelemään kokoaan ja aineenvaihduntaansa, lisääntymään suotuisissa oloissa nopeasti sekä sopeutumaan suuriinkin fysikaalisten tekijöiden, kuten lämpötilan, muutoksiin, minkä vuoksi ne todennäköisesti kykenevät selviytymään voittajina ja jopa runsastumaan tulevaisuuden muuttuvassa ympäristössä. Arktisella alueella tieto kampamaneeteista pohjautuu muutamaan epäsystemaattiseen ja hajanaiseen runsausarviointiin ja ravinnonkäyttötutkimukseen. Itämerellä eläinplanktontutkimuksessa on käytössä alueen valtioiden yhteinen seurantaohjelma, mutta tästä huolimatta arktisen kampamaneetin, Mertensia ovumin, rooli Itämerellä on ollut mysteeri sen jälkeen kun se vuonna 2007 ensimmäisen kerran havaittiin. Tässä väitöskirjatutkimuksessa on tarkasteltu sekä Itämeren että arktisen alueen Cydippida-lahkon kampamaneettien monimuotoisuutta ja merkitystä ravintoketjussa. Tutkimuksen osajulkaisut yhdistelevät laajamittaista, systemaattista näytteenottoa, laboratoriokokeita, lajintunnistusta ja koko ulappayhteisön rakenteen tutkimusta.Osajulkaisuissa arvioidaan Cydippida-lahkon lajirunsautta käyttäen valomikroskopiaa ja uudempia geneettisiä lajintunnistusmenetelmiä sekä tutkitaan M. ovumin ravinnonkäyttöä perinteisillä ja molekyylitason menetelmillä. Näiden tutkimusten tavoitteena on ollut selventää tietoa kampamaneettien roolista merten ekosysteemeissä. Morfologisten ja molekyylitason tunnistusmenetelmien yhdistelmä paljasti, että hallitsevan Mertensia ovumin kanssa arktisilla vesillä esiintyvät myös Euplokamis sp. ja vielä kuvaamaton Mertensiidae-laji. Samoin Euplokamis sp. -laji havaittiin ensimmäisen kerran Itämeren suulla osana laajamittaisempaa amerikankampamaneetin, Mnemiopsis leidyin, ja arktisen kampamaneetin, Mertensia ovumin, seurantaa. Laajamittaisista näytteenotoista huolimatta Pleurobrachia pileus -lajia, jonka on aiemmin raportoitu esiintyvän yleisesti arktisella alueella ja olevan läsnä koko Itämeren alueella (ja joka on aiemmin raportoitu ainoaksi kampamaneettilajiksi pohjoisella Itämerellä), ei havaittu kummallakaan tutkimusalueella. Väitöskirjatyö osoittaa, että perinteiset morfologiset lajitunnistusmenetelmät eivät yksin riitä. On ilmiselvää, että kampamaneettilajit on yleisesti puutteellisesti kuvattu. Lisäksi julkaistujen eenisekvenssien vähyys rajoittaa tarkkuutta, jolle lajit pystytään geneettisillä tunnistusmenetelmillä luokittelemaan. Geneettinen luokittelu on lähempänä suku- tai heimotasoa kuin oikeaa lajitasoa. Yksi väitöskirjan johtopäätöksistä onkin, että kampamaneettien lajintunnistus on varminta, kun yksilöiden valokuvat yhdistetään morfologisten ja molekyylitason tunnistusmenetelmien kanssa. Tieto Mertensia ovumin roolista arktisen alueen ja Itämeren ekosysteemeissä on ollut vääristynyttä, koska tarkkoja tiheystietoja ja historiallista tutkimustietoa on ollut rajoitetusti. Väitöskirjan kahden viimeisen osajulkaisun perusteella on selvää, että M. ovumin vaikutus planktonyhteisössä on suurempi kuin on aikaisemmin ajateltu, etenkin jos lajin ja sen saaliiden laikuittainen esiintyminen otetaan huomioon. Myös alueellinen ja ajallinen vaelluskäyttäytyminen vaikuttavat potentiaaliseen saalistustehokkuuteen. Näin ollen saalistajan ja saaliiden laikuittaiseen esiintymiseen olisi kiinnitettävä enemmän huomiota, jotta peto saalis -vuorovaikutussuhteet saataisiin mallinnettua oikein. Lisäksi saman lajin yhteisöt voivat edustaa eri ravintoverkon tasoja eri alueilla riippuen esimerkiksi yksilöiden kokojakaumasta, kuten arktisen alueen ja Itämeren M. ovum -yhteisöt osoittavat. Arktisella alueella M. ovum on kyltymätön saalistaja, jonka pääasiallista ravintoa ovat hankajalkaisäyriäiset (Calanus spp.). Itämeren yhteisön yksilöt ovat kooltaan huomattavasti pienempiä ja ne syövät lähinnä piko- ja mikroplanktonia. Siten yleistykset lajin ekologisista ominaisuuksista yhteisöstä toiseen voivat olla hyvinkin harhaanjohtavia. Erilaisen ravintokäyttäytymisen lisäksi nämä M. ovum -populaatiot kohtaavat tulevaisuuden ympäristömuutokset eri tavoin, sillä ilmastonmuutos vaikuttaa eri tavalla eri levinneisyysalueilla; Itämerellä esiintymisalueen on ennakoitu pienenevän, kun taas arktisella alueella alue tulee pysymään lähes muuttumattomana. Tämä väitöskirja havainnollistaa, että nykyinen tietomme kampamaneettien monimuotoisuudesta, roolista ulapan ekosysteemissä ja selviytyminen muuttuvassa ympäristössä on edelleen hyvin puutteellista. Väitöskirja myös osoittaa, että voidaksemme ymmärtää kampamaneettien, ja muidenkin hyytelöplanktonryhmien,ekologista roolia ja vaikutusta nyt ja tulevaisuudessa, lajintunnistus olisi tehtävä täsmällisesti asianmukaisia menetelmiä yhdistellen. Erityisen tärkeää olisi suunnitella selkeät suositukset, jotta hyytelöplankton otettaisiin pysyvästi mukaan alueellisiin seurantaohjelmiin

Sea-ice eukaryotes of the Gulf of Finland, Baltic Sea, and evidence for herbivory on weakly shade-adapted ice algae

To determine community composition and physiological status of early spring sea-ice organisms, we collected sea-ice, slush and under-ice water samples from the Baltic Sea. We combined light microscopy, HPLC pigment analysis and pyrosequencing, and related the biomass and physiological status of sea-ice algae with the protistan community composition in a new way in the area. In terms of biomass, centric diatoms including a distinct Melosira arctica bloom in the upper intermediate section of the fast ice, dinoflagellates, euglenoids and the cyanobacterium Aphanizomenon sp. predominated in the sea-ice sections and unidentified flagellates in the slush. Based on pigment analyses, the ice-algal communities showed no adjusted photosynthetic pigment pools throughout the sea ice, and the bottom-ice communities were not shade-adapted. The sea ice included more characteristic phototrophic taxa (49%) than did slush (18%) and under-ice water (37%). Cercozoans and ciliates were the richest taxon groups, and the differences among the communities arose mainly from the various phagotrophic protistan taxa inhabiting the communities. The presence of pheophytin a coincided with an elevated ciliate biomass and read abundance in the drift ice and with a high Eurytemora affinis read abundance in the pack ice, indicating that ciliates and Eurytemora affinis were grazing on algae. (C) 2016 Elsevier GmbH. All rights reserved.Peer reviewe

First recordings of the ctenophore Euplokamis sp (Ctenophora, Cydippida) in Swedish coastal waters and molecular identification of this genus

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Where are they now? – A case study of the impact of international travel support for early career Arctic researchers

Published version, source at http://doi.org/10.1016/j.polar.2016.06.001. License CC BY-NC-ND 4.0.Supporting and training the next generation of researchers is crucial to continuous knowledge and leadership in Arctic research. An increasing number of Arctic organizations have developed initiatives to provide travel support for Early Career Researchers (ECRs) to participate in workshops, conferences and meetings and to network with internationally renowned scientific leaders. However, there has been little evaluation of the effectiveness of these initiatives. As a contribution to the 3rd International Conference on Arctic Research Planning, a study was conducted to analyze the career paths of ECRs who received travel funding from the International Arctic Science Committee between the start of the International Polar Year (2007–2008) and 2013. Two surveys were used: one sent to ECRs who received IASC travel support and one as a specific event study to those unsuccessfully applied for IASC travel support to the IPY 2010 Conference. The results of the surveys indicate that travel support was beneficial to both the research and careers of the respondents, especially if the ECR was engaged with a task or responsibility at the event. Survey responses also included suggestions on how funds could be better used to support the next generation of Arctic researchers

Environmental niche overlap in sibling planktonic species Calanus finmarchicus and C. glacialis in Arctic fjords

Knowledge of environmental preferences of the key planktonic species, such as Calanus copepods in the Arctic, is crucial to understand ecosystem function and its future under climate change. Here, we assessed the environmental conditions influencing the development stages of Atlantic Calanus finmarchicus and Arctic Calanus glacialis, and we quantified the extent to which their niches overlap by incorporating multiple environmental data. We based our analysis on a 3-year seasonal collection of zooplankton by sediment traps, located on moorings in two contrasting Svalbard fjords: the Arctic Rijpfjorden and the Atlantic-influenced Kongsfjorden. Despite large differences in water temperature between the fjords, local realized ecological niches of the sibling Calanus species overlapped almost perfectly. The exception was the earliest copepodites of C. glacialis in Rijpfjorden, which probably utilized the local ice algal bloom in spring. However, during periods with no sea ice, like in Kongsfjorden, the siblings of both Calanus species showed high synchronization in the population structure. Interestingly, differences in temperature preferences of C. finmarchicus and C. glacialis were much higher between the studied fjords than between the species. Our analysis confirmed the high plasticity of Calanus copepods and their abilities to adapt to highly variable environmental settings, not only on an interannual basis but also in a climate warming context, indicating some resilience in the Calanus community

Primary production calculations for sea ice from bio-optical observations in the Baltic Sea

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Contrasting phytoplankton-zooplankton distributions observed through autonomous platforms, in-situ optical sensors and discrete sampling

Plankton distributions are remarkably ‘patchy’ in the ocean. In this study, we investigated the contrasting phytoplankton-zooplankton distributions in relation to wind mixing events in waters around a biodiversity-rich island (Runde) located off the western coast of Norway. We used adaptive sampling from AUV and shipboard profiles of in-situ phytoplankton photo-physiology and particle identification (copepods, fecal pellets and the dinoflagellate Tripos spp.) and quantification using optical and imaging sensors. Additionally, traditional seawater and net sampling were collected for nutrient and in-vitro chlorophyll a concentrations and phytoplankton and meso-zooplankton abundances. Persistent strong wind conditions (~5 days) disrupted the stratification in offshore regions, while stratification and a subsurface chlorophyll maximum (SCM) were observed above the base of the mixed layer depth (MLD ~30 m) in inshore waters. Contrasting phytoplankton and zooplankton abundances were observed between inshore (with the presence of a SCM) and offshore waters (without the presence of a SCM). At the SCM, phytoplankton abundances (Tripos spp., the diatom Proboscia alata and other flagellates) were half (average of 200 cell L-1) of those observed offshore. On the contrary, meso-zooplankton counts were ~6× higher (732 ind m-3 for Calanus spp.) inshore (where a SCM was observed) compared to offshore areas. In parallel, fecal pellets and ammonium concentrations were high (>1000 ind m-3 for the upper 20 m) at the SCM, suggesting that the shallow mixed layer might have increased encounter rates and promoted strong grazing pressure. Low nutrient concentrations (< 1μM for nitrate) were found below the MLD (60 m) in offshore waters, suggesting that mixing and nutrient availability likely boosted phytoplankton abundances. The size of the absorption cross-section (σPII’) and yield of photosystem II photochemistry under ambient light (φPII’) changed according to depth, while the depth-related electron flow (JPII) was similar between regions, suggesting a high degree of community plasticity to changes in the light regime. Our results emphasize the importance of using multiple instrumentation, in addition to traditional seawater and net sampling for a holistic understanding of plankton distributions.publishedVersio

Increased occurrence of the jellyfish Periphylla periphylla in the European high Arctic

This is a post-peer-review, pre-copyedit version of an article published in Polar Biology. The final authenticated version is available online at https://doi.org/10.1007/s00300-018-2368-4.The jellyfish Periphylla periphylla, which can have strong ecological impacts on its environment, is ubiquitous in the Norwegian Sea and its range was predicted to extend northwards. The occurrence of P. periphylla in the northern Barents Sea increased since 2014 and, for the first time, several individuals were collected within a high Arctic fjord (> 78°N) in western Spitsbergen in January 2017. The low solar irradiance prevailing during the polar night and an increased inflow of relatively warm Atlantic water in the European Arctic since the last decade likely provide suitable conditions for the medusa to colonize Svalbard’s fjords during the winter months. However, light avoidance constrains the photophobic P. periphylla to deeper offshore areas during the midnight sun period. The current occurrence of P. periphylla in high Arctic fjords during the polar night will have a limited impact on marine ecosystems in the short term, but long-term effects are more uncertain if its abundance continues to increase

Diversity and seasonal development of large zooplankton along physical gradients in the Arctic Barents Sea

Due to ongoing climate change, a new Arctic Ocean ecosystem is emerging. Within the framework of the Nansen Legacy project, we investigated the community composition of the large zooplankton and its seasonal development along a latitudinal gradient in the northern Barents Sea. Total biomass was maximal in summer and early winter, and minimal in spring, with copepods contributing considerably in all seasons. Euphausiids represented a minor fraction of the biomass, whereas chaetognaths and other gelatinous zooplankton contributed substantially to the sampled zooplankton at all stations, particularly in winter. Amphipod biomass was high in early winter, but otherwise low. Temperature in the water column interior and bottom-depth had the highest explanatory power for the community composition of the large zooplankton, both revealing the same distinct Atlantic and Arctic domains along the studied section. The continental shelf of the northern Barents Sea had an Arctic signature and was in terms of biomass characterized by a dominance of cold-water species, such as Themisto libellula, and Calanus glacialis. The copepod Calanus hyperboreus was the dominant over the continental slope. Locations at the southern and northern end of the studied section were influenced by Atlantic Water (at intermediate depth at the northern stations), and contained a mixture of temperate species, deep-water species, and sympagic amphipods in northern ice-covered waters. In the northern Barents Sea, a seasonal change was observed in the biomass fractions of different zooplankton feeding guilds, with dominance of herbivores in summer and carnivores in winter. This suggests switching between bottom-up and top-down control through the year. On the continental slope, species that are typically considered omnivores seemed to increase in importance. The role of seasonally changing food preferences to bridge periods outside of the main primary production season is discussed in light of ecosystem resilience to the expected changes in the Arctic Ocean.publishedVersio