Month: March 2021

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Diatoms (and their fossils) in ice-covered ocean – from microscope slides to a peer-reviewed publication

by Ben Redmond Roche

I was lucky enough to be a member of the Heikkilä Research Group during the latter half of my MSc (2018-19) and worked very closely with the sagacious diatom specialist Kaarina Weckström. My MSc project appears of interest to the wider scientific community: since our findings were accepted for publication in Marine Micropaleontology (1) in March 2020 there has been ongoing interest in the work, with 4 citations already (2-5). A year after acceptance, as of March 2021, it is still the most downloaded (within past 90 days) article from the journal! How did my project advance in practice? Why does it matter?

The research comprised re-examining 46 selected microscope slides from the North Atlantic training set (6, 7, 8), the largest and most geographically extensive diatom set in the Northern Hemisphere, in order to explore the spatial distributions of the sea-ice affiliated diatoms Fragliaropsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica (A, B & C in Fig. 1, respectively) with respect to sea-surface temperatures and sea-ice concentrations. Due to the subtle morphological differences, the previous training set and literature had grouped the three species collectively under one species name, F. oceanica.

Figure 1. 1000x magnification (A) F. oceanica (B) F. reginae-jahniae (3) F. arctica.

In paleoceanography, training sets such as the one I began exploring, are used to assess the modern relationships of microfossil species (in this case diatoms) to environmental conditions, such as sea-surface temperatures or sea-ice concentration. These species-environment relationships can then be used for reconstructing past environmental conditions from the microfossils in sediment sequences covering past millennia.

I began my research project asking: Are the distributions and thus ecologies of the three diatom species different? Does grouping the three species in the training set potentially mask the true signal of past ocean conditions in reconstructions?

Since the three species are morphologically very similar, and I spent several days training on the microscope with Kaarina learning to distinguish them from one another. The differences can be seen in Figure 1 and summarised by the following descriptions:

It took a while to gain competence on the microscope, but eventually I got my eye in and noted the fundamental differences: F. reginae-jahniae is elongated and the valves are more parallel; F. oceanica has more rounded valves; and F. arctica has the idiosyncratic circular ends. I then counted the relative abundance of the species in the 46 slides over several weeks (a good podcast is crucial when counting diatoms!). We then analysed the species-environment relationships, particularly to April sea-ice concentration (aSIC) and August sea surface temperature (aSST). The multivariate statistical analyses encompassed two aspects: a redundancy analysis (RDA), expressed as a biplot where species are plotted against the variables, and environmental response curves of the species created using R. The latter was done by Professor in Quantitative Palaeoecology Steve Juggins from Newcastle University (p.s. If you start working on quantitative reconstructions, I highly recommend the Chapter Steve wrote with John Birks in vol 5 of Tracking Environmental Change Using Lake Sediments.).

Figure 2. Geographical distributions of the species, grouped and un-grouped. Note the pan-Arctic concentration of F. oceanica compared to F. reginae-jahniae and particularly F. arctica, which is strongly related to the Northwater Polynya region.

It was apparent from the heterogeneous distributions of the species (Fig. 2) that the individual maximum abundances occurred at different aSST/aSIC. The different respective maxima are described in detail in Table 2, but the general results were: F. oceanica is not a true sea-ice species, being present in a wide range of conditions; F. reginae-jahniae has a strong relationship to high aSIC and cold conditions; F. arctica has a particularly strong relationship to high aSIC and is possibly a specialised species in polynya conditions (year-round open ocean surrounded by sea ice). The differences between the species are significant, particularly of F. reginae-jahniae and F. arctica to F. oceanica.  Therefore, separating these species during reconstructions will result in much more nuanced interpretations of palaeo-conditions, particularly of sea ice.

With sea ice declining in the Arctic (9)  and the Atlantic Meridional Overturning Circulation weakening (10) , it is imperative that high-resolution reconstructions of past rapid climate change are made from across the Arctic region to better understand what the potential implications may be. Furthermore, sea-ice affiliated algae are a crucial component of the early spring bloom, contributing for 50-60% of total primary production during the transitional phase (11, 12), with pennate diatoms often accounting for >90% of the total biomass (13); it is imperative that we learn more about these keystone species.

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Ben is a PhD student at RHUL interested in the climatic and ecological implications of polluted sea ice.

List of references:

  1. Weckström K, Roche BR, Miettinen A, Krawczyk D, Limoges A, Juggins S, Ribeiro S, Heikkilä M., 2020. Improving the paleoceanographic proxy tool kit – On the biogeography and ecology of the sea ice-associated species Fragilariopsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica in the northern North Atlantic. Marine Micropaleontology 157:101860. https://doi.org/10.1016/j.marmicro.2020.101860.
  2. Limoges A, Weckström K, Ribeiro S, Georgiadis E, Hansen KE, Martinez P, Seidenkrantz M-S, Giraudeau J, Crosta X, Massé G, 2020. Learning from the past: Impact of the Arctic Oscillation on sea ice and marine productivity off northwest Greenland over the last 9,000 years. Global Change Biology 26:6767–6786. https://doi.org/10.1111/gcb.15334.
  3. Hernández-Almeida IKR, Bjørklund P, Diz S, Kruglikova T, Ikenoue A, Matul M, Saavedra-Pellitero N, Swanberg, 2020. Life on the ice-edge: Paleoenvironmental significance of the radiolarian species Amphimelissa setosa in the northern hemisphere, Quaternary Science Reviews 248:106565. https://doi.org/10.1016/j.quascirev.2020.106565.
  4. Armbrecht LH, 2020. The potential of sedimentary ancient DNA to reconstruct past ocean ecosystems. Oceanography 33:116-123. https://doi.org/10.5670/oceanog.2020.211.
  5. Luostarinen T, Ribeiro, S, Weckström, K, Sejr, M, Meire, L, Tallberg, P, Heikkilä, M, 2020. An annual cycle of diatom succession in two contrasting Greenlandic fjords: from simple sea-ice indicators to varied seasonal strategists, Marine Micropaleontology 158:101873. https://doi.org/10.1016/j.marmicro.2020.101873.
  6. Koç N, Jansen E, Haflidason H, 1993. Paleoceanographic reconstructions of surface ocean conditions in the Greenland, Iceland and Norwegian seas through the last 14 ka based on diatoms. Quaternary Science Reviews 12:115–140.
  7. Andersen C, Koç N, Moros M., 2004. A highly unstable Holocene climate in the sub- polar North Atlantic: evidence from diatoms. Quaternary Science Reviews 23:2155–2166. https://doi.org/10.1016/j.quascirev.2004.08.004.
  8. Miettinen A, Divine D, Husum K, Koç N, Jennings A, 2015. Exceptional ocean surface conditions on the SE Greenland shelf during the Medieval Climate Anomaly. Paleoceanography 30:1657–1674. https://doi.org/10.1002/2015PA002849.
  9. Polyakov IV, Pnyushkov AV, Alkire, MB, Ashik IM, Baumann TM, Carmack EC, Goszczko I, Guthrie J, Ivanov VV, Kanzow T, Krishfield R, Kwok R, Sundfjord A, Morison J, Rember R, Yulin A, 2017. Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean. Science 356:285–291. https://doi.org/10.1126/science.aai8204.
  10. Caesar L, McCarthy, GD, Thornalley DJR, Cahill N, Rahmstorf S, 2021. Current Atlantic Meridional Overturning Circulation weakest in last millennium. Nature Geoscience 14, 118–120. https://doi.org/10.1038/s41561-021-00699-z.
  11. Gosselin M, Legendre L, Therriault J-C, Demers S, Rochet M, 1986. Physical control of the horizontal patchiness of sea-ice microalgae. Marine Ecology Progress Series 29:289–298. https://doi.org/10.3354/meps029289.
  12. Fernandez-Mendez, M, Katlein, C, Rabe, B, Nicolaus, M, Peeken, I, Bakker, K, Flores, H, Boetius, A, 2015. Photosynthetic production in the Central Arctic Ocean during the record sea-ice minimum in 2012. Biogeosciences 12:3525–3549. https://doi.org/10.5194/bg-12-3525-2015.
  13. Rozańska, M, Poulin, M, & Gosselin, M., 2008. Protist entrapment in newly formed sea ice in the coastal Arctic Ocean. Journal of Marine Systems 74: 887–901. https://doi.org/10.1016/j.jmarsys.2007.11.009.
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How to tend to your research (and motivation) during a pandemic: our view of the past year

by Lilia Orozco

It is almost a year since the COVID-19 pandemic spread globally, but the final repercussions for science will be realized in the years to come. Travel restrictions canceled most planned fieldwork, conferences and research visits, while social distancing changed the way we communicate, plan our activities and interact. How we, as a scientific community, confront the new circumstances has been a subject of conversation from the beginning (1-3).

On March 16, 2020, the Universities in Finland were shut down. Since then, our research group has been managing projects and thesis work from a new angle. I started my PhD research on past northern lake ecosystems in November 2020, amid the exceptional situation. I was prepared for the home office and the uncertainty in field and lab work plans. It helped me to focus on what I can do rather than what I cannot. A pandemic-suited mindset might be easy to set at the beginning of a project, but how has it been for those who made their plans prior to COVID-19? I asked our group.

Most of us had to make arrangements. Maxime Courroux, a Master’s student studying sub-arctic lakes, explains:

“A Master’s thesis is a relatively short project. But within a year, I had to change my topic, re-plan my field schedule, and manage to finish everything on time. While this wasn’t a walk in the park, the shared struggle with peers has led to a lot of support. Nothing went as expected, but it was still fun.”

For Tiia Luostarinen, PhD candidate studying microscopic sea-ice organisms, the closure of universities, and even countries, meant leaving laboratory analyses at a short notice.

“When the pandemic started to spread in Europe, I was in Denmark for some lab work but was supposed to travel back home in a couple of days anyway. When the Danish government announced that they are closing their borders, I changed my flights and returned to Finland. It was hard to miss saying proper goodbyes to everyone in Copenhagen.”

Despite the boost in discoveries and publications about and COVID-19 (4, 5) in the past year, natural sciences looking into equally topical global challenges, e.g. climate change and environmental degradation, have not had that luck (6). Restrictions have forced scientists to re-think their projects and plans. The University of Helsinki closed its facilities, but we have been able to carry out essential lab work under strict regulations.

Maija Heikkilä, the principal investigator of both currently active Academy of Finland funded projects, faces these circumstances head-on:

“Getting a research project funded is always a thrill, and in all honesty, having another research project launched during the global pandemic was equally exciting. There are new questions to be answered, new people to be hired, and due to the pandemic, new implementation plans to be made. This is much easier at the very beginning of the project than in the middle of it, but we have managed all our work rather brilliantly. Our University has been strict but prioritized science where possible.”

The University of Helsinki allowed a field trip on our Master’s level course Past environmental change in January 2021, because it was held outdoors with safe distances. Senior researcher Jan Weckström giving a demonstration on sampling methods. Maxime and Lilia were teaching assistants.

Collaboration and exchange of ideas are focal to any research. The social restrictions have forced us to use different technologies (who could have imagined the now-so-routine ZOOM coffees a year ago!). The new ways of communicating are not always ideal, in particular if you have just arrived in a new country. This is the experience of Ana Lúcia Lindroth Dauner, the new postdoc researcher in the team working on integrating and combining paleoecological data. Ana has not even met everybody in the group in person.

“Besides conciliating the time between academic and domestic work, the main issue I have had in starting to work on a project in the midst of the pandemic is the lack of personal contact. The pandemic makes it difficult to get to know new people and, therefore, to share thoughts and ideas.”

Ana shared a view to her home office.

We have all coped with the situation that started one year ago in different ways. We have had to find a balance between life and work, transform our homes into offices, and accept new realities that we did not expect. For Master’s student Meri Mäkelä, whose thesis unravels past ecosystem changes in an arctic fjord, staying motivated has helped her finish her project.

“In February 2020 I definitely couldn’t predict that after a year I would still be finishing my Master’s thesis surrounded by the pandemic. No doubt that the pandemic has slowed down my thesis project, but to be honest, my enthusiasm to left no stone unturned should be blamed more. At least I have learned to make less overly optimistic timetables for my projects to come – I hope.”

Confinement is not ideal for everyone, but after a year of this reality, we have modified our practices. Tiia has learned to appreciate the time at home.

“If you would have asked me if I liked working from home a year ago, the answer would’ve been a definite no. But this situation has at least taught me to appreciate the quietness and flexibility of working from home. And obviously, the better coffee.”

Like Tiia, Maija profits from the advantages of telecommuting and stays optimistic.

“The lack of commuting and traveling has brought a new sense of tranquility to daily work tasks and challenged me to develop new ways for team building. I am positive and face challenges that are much smaller than the responsibility of an individual to take part in fighting the global pandemic.”

Indeed, while we look forward to resuming fieldwork and in-person interaction as soon as it is safe, it is good to keep things in perspective. Despite our differing experiences and perspectives from the past year, everyone has surely mastered one thing – to adapt.

—-

Lilia Orozco is a PhD student who celebrates picking the first fossil remains in her lake sediment samples.

List of references:

  1. Clay RA (2020, March 19). Conducting research during the COVID-19 pandemic. http://www.apa.org/news/apa/2020/03/conducting-research-covid-19
  2. Pain E (2020, April 17) How early-career scientists are coping with COVID-19 challenges and fears. Science Careers.
  3. Kupferschmidt K (2020, February 26). A completely new culture of doing research. Coronavirus outbreak changes how scientists communicate. Science News. 
  4. Science in the Wake of the Pandemic: How Will COVID-19 Change the Way We Do Research? (2020). Molecular cell 79:9–10. https://doi.org/10.1016/j.molcel.2020.06.024
  5. Palayew A, Norgaard O, Safreed-Harmon K, Andersen TH, Rasmussen LN, Lazarus JV (2020). Pandemic publishing poses a new COVID-19 challenge. Nature Human Behaviour 4:666-9. https://doi.org/10.1038/s41562-020-0911-0
  6. Bian SX, Lin E (2020). Competing with a pandemic: Trends in research design in a time of Covid-19. Plos One 15:e0238831. https://doi.org/10.1371/journal.pone.0238831
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Brief overview of current projects

Beyond the shore: sea-ice change and lake ecosystems in the Arctic (SLEET)

The land and the sea are quintessentially tied together via the global hydrological cycle and atmospheric circulation patterns, yet significant disconnect persists in both research and management of land and marine ecosystems. Future intensification of the hydrological cycle in the Arctic and the increased interaction of the sea surface with the atmosphere will further enhance ecosystem interaction across the land-sea boundaries. The overarching objective of this project is to develop an understanding of the natural, long-term coupling of arctic sea-ice cover and lake ecosystem functioning on adjacent land in complementary spatial scales. The project will explore the atmospheric mechanism of this link by reconstructing moisture balance trends and probing their linkages to the quantity and quality of production. (Academy of Finland 2020-2024)

Arctic sea-ice proxies: from seasonal processes to improved reconstructions

Sea-ice decline is one of the most striking consequences of recent climate-driven changes in the Arctic. The short observational time series and current climate models are inadequate in explaining the natural variation and foreseeing responses of arctic marine ecosystems, highlighting the urgent need to exploit natural archives (proxies). Protists abundantly stored in the seafloor of the Arctic Ocean are widely applied proxies for past sea-ice reconstruction, notwithstanding that little is known of their relationships to the ice ecosystem. This project will investigate seasonal processes that result in the formation of proxy archives and apply this knowledge in ecosystem modelling and reconstruction of pre-anthropogenic sea-ice conditions. The results will improve our understanding of the seasonal behaviour of arctic marine ecosystems in the long term. (Academy of Finland 2016-2022)

CAPTURE Consortium Work Package 3: Past and present lake carbon dynamics

The Arctic environment is undergoing marked changes in climate conditions and terrestrial feedbacks that are prone to investigation under the multidisciplinary framework of CAPTURE. The interactions among climate, C and Arctic ecosystems are complex, and there are substantial risks of unexpected feedbacks and rapid transformations. One of the main originalities of the CAPTURE consortium is assessing the C processes in the Arctic across spatial and temporal scales, in order to advance our understanding of C dynamics, climate variability and the risks of unwelcome C-cycle feedbacks.

WP3 investigates the quantity and quality of lake C in present conditions and over the major climatic fluctuations of the late Holocene. In collaboration with WPs 1, 2, and 4, WP3 will assess the lateral C flow between terrestrial and aquatic ecosystems. C quality will be of special interest, since parsing contributions of C sources are essential to understanding lake aquatic C cycling and burial efficiency WP3 focuses on lake sediment records for three principal reasons. First, while many long-term records signify the role of lake
sediments as global C sink, they consider average C accumulation over long time periods and are hence not adequate for observing responses of C burial to rapid climate changes. Second, the role of changing C sources over past climate intervals and the long-term persistence of C sink are largely unknown. Third, most studies focus on temperate and boreal lakes, while contrasting controls of C cycling are at play in the Arctic. (Academy of Finland 2016-2020)

Author: Maija Heikkilä