GeoLog

The absorption of atmospheric CO₂ by the oceans results in a decline in ocean pH, hence ‘ocean acidification’, and reduces carbonate ion availability. This presents a problem to calcifying organisms (those that deposit calcium as either calcite or aragonite as hard parts) because they cannot produce their shells, valves (in the case of bivalves), or tests (in the case of diatoms) as readily.

To explain this, we need a little chemistry. When CO₂ dissolves, it combines with water to form carbonic acid (H₂CO₃). This then breaks down to form bicarbonate (HCO₃^-) when one hydrogen ion is lost, and then carbonate (CO₃^2-) as the other hydrogen ion is lost. This carbonate is the important stuff, as it combines with calcium to form the calcium carbonate (CaCO₃) used by bivalves to produce shells. If something (such as the ocean) is more acidic, there must be more hydrogen ions available. These hydrogen ions interfere with the calcification process as they bond with carbonate, meaning there is less available for shell formation.

Calcification: carbonate chemistry in action!

This process is relatively well established for a number of calcifying organisms, although there are exceptions to (the coccolith, Emiliania huxleyi, for example) and the response to elevated CO₂ levels is not uniform across species.

Much of current research has focussed on the effect of constant CO₂ levels on calcification, but what about animals that live in environments where the CO₂ concentration is constantly changing? The availability of carbonate in estuaries is particularly variable as CO₂ concentrations vary seasonally (there’s a greater carbon load in the winter as storms wash nutrients into rivers), diurnally and with the tide. The impact of elevated CO₂ levels on an organism is also dependant on its life stage; something that is particularly true of bivalves.

Bivalve larvae. Photo credit: Minami Himemiya (source).

Bivalves spend the first part of their life in the plankton, first as a veliger (a relatively amorphous looking ciliated blob) and then as a pediveliger (that same blob, but this time with an identifiable foot) before metamorphosing into a miniature adult. During these larval stages, they are particularly vulnerable to ocean acidification and, until recently, both the reasons behind this, and the longer-term implications of this vulnerability, were unclear.

This is where doctors Christopher Gobler and Stephanie Talmage come in. They took to the lab to tackle why larvae are especially vulnerable to acidification and what this means for them in both the short and long term. It’s impossible to take a look at how all bivalves respond to acidification, though, so to tackle these questions, two bivalve species, the hard-shelled clam (Mercenaria mercenaria) and the Atlantic bay scallop (Argopecten irradians) joined the team.

The Atlantic bay scallop, Argopecten irradians. Photo credit: Rachael Norris and Marina Freudzon (source).

Using their RNA:DNA ratio as a proxy for growth and the uptake of a radioactive calcium isotope, ⁴⁵Ca, to estimate calcification, Gobler and Talmage found that growth in the presence of elevated CO₂ results in individuals of a smaller size. This is because there is less calcium available for uptake. Their findings, revealed that high CO₂ concentrations, not only affected size, but also negatively impacted bivalve physiology, as individuals reared in these conditions were found to have thinner shells. Shells are an important defence against predators and the reduction in shell thickness (and hence strength) may put them at greater risk from predation.

The higher the CO2, the slower the calcium uptake: calcium uptake rates of larval Atlantic bay scallop, Argopecten irradians, under different CO2 concentrations over a 12-hour period (Gobler and Talmage, 2013).

When transferred from a high CO₂ environment to an environment with an ambient CO₂ concentration, larvae grew faster than those in ambient conditions throughout the whole of their development. However, this higher growth rate doesn’t compensate for the low calcification rate during larval stages, as their final is still smaller than individuals reared in ambient conditions at all life stages. This “legacy effect” presents a significant problem for adult bivalves, due to the detrimental impact of reduced calcification on their defences.

By Sara Mynott, EGU Communications Officer

Reference:

Gobler, C. J. and Talmage, S. C.: Short- and long-term consequences of larval stage exposure to constantly and ephemerally elevated carbon dioxide for marine bivalve populations, Biogeosciences, 10, 2241-2253, doi:10.5194/bg-10-2241-2013, 2013.

We model the changes in the geographic location of continents via paleogeographic reconstructions. However, the current methodology for generating these reconstructions is not without problems! Publication of palaeogeographic reconstructions is scarce, probably resulting from the difficulties associated with generating them. Conventional reconstructions are presented as static maps which have poor spatial and temporal resolution. In addition, they are often difficult to replicate as the ‘input data’ used to produced the reconstructions is usually not included in publication. Reconstructions quickly become outdated as the models they are superimposed onto are improved and become more refined.

In Biogeosciences, Wright et al. (2013) present a new method which hopes to overcome some of the issues associated with conventional palaeogrographic reconstructions. Combing the open-source plate motion reconstruction tool, GPlates, with paleobiological data the aim is to uncover spatial and temporal correlations and test the reliability of existing reconstructions. GPlates allows for easy modification and updating of reconstructions and is easily linked to already established models. The new method is tested against the already existing publicly accessible Palaegeographic Atlas of Australia (Totterdell, 2002). It contains 70 palaeogeographic time slices for the Phanerozoic derived from palaeoenvironmental reconstructions, tectonic histories and other geological evidence. In addition, the model is supplemented with fossil indicators from the open-access Palaeobiology database.

Fossil collections (a), palaeogeographical reconstructions taken from the Palaeogeographic Atlas for Australia (b), are reconstructed in GPlates (c) using the Phanerozoic plate motion model (d) and data associations, as per the Emsian example (e) to test and refine the palaeogeographic and plate motion models (click for larger). Source: Wright et al., 2013.

In order to generate their own plate reconstruction in 1Myr intervals in GPlates, for the Australian Phanerozoic, the authors based their relative plate motions on work by Dr. Jan Golonka. The plate motions are derived from palaeomagentic data and Apparent Polar Wander Paths (APW) and are further supported by geological observations, such as location of orogenies and sedimentary basins. A number of taxonomical data were acquired from the Palaeobiology database and assigned GPlates mark-up language so that the data could be included in the new reconstructions. The time scales between the Palaoegeographic Atlas of Australia and the Paleobiology database differed, so they were standardised. The spatial and temporal associations between the palaeogeography and fossil collections were tested for inconsistencies. Where these arose; the fossil collections were taken as the true representation of the palaeoenvironment. For example, if the fossils indicated a truly marine environment, whilst the palaeogeography suggested a terrestrial setting, this was flagged as an inconsistency in the model that needed refining.

The new model has allowed the authors to gain a detailed understanding of the plate tectonic movements of Australia during the Phanerozoic. The article goes into much greater detail than I intend to do so here, I refer you to the article itself if you want more information! During the Cambrian, the new model suggests that Australia spanned equatorial latitudes and formed part of Gondwana. By the Palaeozoic, the Northern margin of Gondwana (North and South China, Tibet and Indochina, amongst others) had detached and this marked the onset of opening and closing of a number of palaeo-Asiatic and Tethys basis. The remaining Pangaea further breaks-up during the Cretaceous, with India and Australia moving northwards, away from Antarctica.

Temporal coverage of eastern Australia basins (EA) and the Eromanga Basin (EB). The data gaps may be related to sampling gaps, orogenic episodes and the influence of glaciations during the late Palaeozoic. Source: Wright et al., 2013.

Palaeogeographic and biofacies data can be embedded into the plate tectonic models in order to uncover inconsistencies and refine the reconstructions. The clear benefits of including palaeobiological data are highlighted during the Emsian time period (402Ma). The paleogeographic reconstruction from the Atlas for Australia proposed a land environment for deposition at this time, whilst the fossil and lithological evidence, suggest a marine environment. Temporal ranges of fossils in relation to the deposition of their associated Formations were problematic and no formations which displayed age disagreements were included in the new model.

Whilst the inclusion of paleobiological data is clearly beneficial to the construction of the models, geographical and temporal gaps in the fossil record, compromise the accuracy of the plate reconstructions. In some cases the gaps in the fossil record are simply due to a sampling bias, but in others it is not clear if the issue is fossil preservation or the environment at the time of deposition.  As a result, other data are required as a proxy for biological data. Improvements to the models could be made by including other paleoenvironment indicators such as data from well logs could be included in future models. To further improve the methodology, it is important to remember that sediments and fossils deposition is often confined to basins. In future, it would be valuable to included elevation data or proxies for these into the models. GPlates will also soon allow the incorporation of chronostratigraphic data (Sikora et al., 2006) as well as paleobiological data.

By Laura Roberts Artal, PhD Student, University of Liverpool

References:

Golonka, J.: Late Triassic and Early Jurassic palaeogeography of the world, Palaeogeogr. Palaeocl., 244, 297–307, 2007.

Totterdell, J. M.: Palaeogeographic Atlas of Australia, Geoscience, Australia, 2002.

Sikora, P. J., Ogg, J. G., Gary, A., Cervato, C., Gradstein, F., Huber,B. T., Marshall, C., Stein, J. A., and Wardlaw, B.: An integrated chronostratigraphic data system for the twenty-first century, Geoinformatics: data to knowledge, 397, 53–59, 2006.

Wright, N., Zahirovic, S., Müller, R. D., and Seton, M.: Towards community-driven paleogeographic reconstructions: integrating open-access paleogeographic and paleobiology data with plate tectonics, Biogeosciences, 10, 1529-1541,  2013.

Yellowstone National Park, USA, is well known for its outstanding natural beauty.

“Grand Prismatic Spring” by David Mencin, distributed by the EGU under a Creative Commons licence.

This is the Grand Prismatic Spring in the Midway Geyser Basin, Yellowstone National Park. It is the third largest hotspring in the world and the largest found in the United States, with a maximum diameter of about 90 m. It discharges roughly 2.5 cubic metres of mineral-rich water per minute, which flows down the rocky terraces evenly on all sides. Hotsprings are rich in minerals because warmer water is capable of holding more dissolved solids than colder water – and the water here can reach 87 °C in the centre of the spring!

Little can survive these high temperatures, though there are strains of thermophyllic (heat loving) bacteria and algae (chemoautotrophs and heteroautotrophs) that thrive in these conditions! There is more life found at the edges of the spring where waters are cooler. Rather than producing energy from the sun, as is the case for photosynthetic bacteria, chemoautotrophic bacteria oxidise minerals in the spring-water to produce energy. Heteroautotrpohs, on the other hand, use both photosynthesis and chemoautotrophy to obtain their energy.

These bacteria are also responsible for the bright rings of colour that surround the spring. Coating the rock in large bacterial mats; their energy-harnessing pigments dictate the colours that surround the water. If the bacteria contain more chlorophyll, the mats will be more green in colour and if they contain more carotenoids, the bacterial carpet will be more of an orangey brown.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their images to this repository and since it is open access, these photos can be used by scientists for their presentations or publications as well as by the press and public for educational purposes and otherwise. If you submit your images to Imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

After studying ‘Applied Environmental Sciences’ I decided to go with a friend for six months to New Zealand for the southern hemisphere winter. Leaving as soon as my diploma thesis (on epiphytic lichens) was written, we set off into the distance to work and travel. We chose New Zealand as our dream destination because these two islands have so many different landscapes to offer – and this is how I was able to capture this picture:

“Honeycomb Weathering” by Stefanie Boltersdorf (University of Trier, Germany), taken on the Kaikoura Peninsula, New Zealand. This photo is distributed by the European Geosciences Union under a Creative Commons License.

The photo shows honeycomb weathering on the Kaikoura Peninsula, with extends from the East coast of the South Island. Composed of mudstone and limestone, the terraces were once wave-cut platforms and have since been uplifted and deformed (during the Quaternary). The peninsula extends into the sea and encounters the relatively shallow Chatham Rise, an area of ocean floor to the east of New Zealand that was largely dry during the Cretaceous period, but now lies nearly 1000 metres underwater. This area is also one of the region’s most productive fishing grounds, a consequence of the nutrient-rich water that upwells along the coast. At low tide, the ocean gives way to a rocky floor, which is easily navigable by foot for quite some distance – and from there you can have a better view of the local seals and seabirds. At this spot, a branch of the Southern Alps, the so-called Seaward Kaikoura Range, comes close to the sea.

Very early in the morning, after sleeping next to the sea and having breakfast in our small van, ‘Berty’, the tide was very low and we took the opportunity to go for a walk. It was on this adventure we found this stunning structure, peppered with small molluscs that were sheltering in the eroded depressions. These depressions are a consequence of honeycomb weathering – a process initiated when salt meets porous rock. Sea spray delivers salt to the rocks, which, after the water has evaporated, is deposited in the pore spaces. Over time, the salt crystals push the minerals apart and weaken the rock. Small pockets collect seawater and erode into ever-larger depressions, eventually creating this marvellous honeycomb structure.

Although I have been dealing with epiphytic lichens during my diploma thesis, I remained true to them, even after my trip. After my return, and inspired by my trip to the highly lichen-rich New Zealand, I started my PhD thesis – investigating a method of quantitatively and qualitatively assessing nitrogen deposition in lichens, with the help of stable isotopes.

By Stefanie Boltersdorf, with Geo-facts from Sara Mynott

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

“Amazonian floodplain” by Jürgen Kesselmeier, distributed by the European Geosciences Union under a Creative Commons licence.

After the Nile, the Amazon River is the second longest river in the world and, by releasing up to 300,000 cubic metres per second into the Atlantic Ocean, accounts for approximately one-fifth of the planet’s total river flow. The river and its tributaries are characterised by extensive annual flooding of over 350,000 square kilometres of forested areas. Floodplain water levels may exceed 9m.

Not all of the Amazon’s tributaries flood simultaneously each year. For example, many branches begin to flood in November and continue to rise until June, whereas the Rio Negro starts rising in February or March.

The freshwater ecosystems of the Amazon floodplain are vital repositories of biodiversity, hosting fish, reptiles, and other aquatic animals normally inhabiting the river’s main water channels but migrating to newly-flooded areas in order to feed and reproduce. The region’s flora also relies on the annual flooding cycle: seeds are dispersed by the water and by fruit-eating animals and fish that thrive in the temporary wetlands.

This view of the flooded forest was captured by Jürgen Kesselmeier, a biogeoscientist at the Max-Planck-Institut für Chemie, Mainz, Germany. He explains, “I took this picture at the end of April 2008 during one of my visits to the Amazonian rainforest, in the Várzea, or ‘floodplain’ region of the Rio Solimoes near Manaus (shortly before this river joins the Rio Negro). This area is known to show a flood pulse of 10-15m, meaning the water level of these river systems fluctuates by 10-15m on a regular basis every year. This picture was shot near the time of maximum flooding and therefore large areas were inundated. It features a magical-looking forest and, to me, offers a glimpse into just why this ecosystem is so special.”

Logging and the clearing of land for cattle ranching change the Amazonian floodplain landscape. Overfishing, the construction of dams and roads, and pollution, from nearby human habitations and gold mining in smaller streams, also threaten the local ecosystem.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

“Irish coast” by Lena Noack, distributed by the European Geosciences Union under a Creative Commons licence.

Among geoscientists, the beautiful island of Ireland is best known for its Giant’s Causeway, an area with some 40,000 polygonal columns of layered basalt that formed 60 million years ago as a result of a volcanic eruption. But another recognisable feature of the Emerald Isle, is its lush green vegetation, a product of the island’s mild climate and frequent rainfall.

It was on a rare sunny day of a two-week trip to Ireland in September 2010 that Lena Noack from Germany’s Institute of Planetary Research in Berlin capture this stunning landscape. Lena says: “I took the photograph on a holiday, a round-trip all over Ireland I did together with two friends. We wanted to see the beautiful nature the island is famous for and found it almost everywhere! The trip was an unforgettable experience, and I would love to go back one day.”

The photo beautifully showcases Ireland’s colours: the calm blue of the sea and the bright green of the pastures. It was captured along the south-western coast of the island in the Dingle peninsula.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

In this month’s Geosciences column, Mona Behl discusses a recent paper on the effects of anthropogenically-induced climate change on the planet’s oceans. 

A recent study led by scientists at the Scripps Institute of Oceanography, University of California San Diego, suggests that observed changes in ocean salinity are inconsistent with natural climate variations and can be attributed to human-induced climate change.

Average salinity measured near ocean surface (Source: NASA)

Co-authored by Peter J. Gleckler, Benjamin Santer, and Paul Durack of the Lawrence Livermore National Laboratory in Livermore, California, and Tim Barnett of The Scripps Institution of Oceanography, the paper, entitled “The fingerprint of human-induced changes in the ocean’s salinity and temperature fields,” was published in the AGU journal Geophysical Research Letters on 2 November 2012. This research builds on the studies conducted by Barnett et al. (2005) and Pierce at al. (2006), examining warming in the upper 70 m of the ocean and concluding that it could also be explained by human-induced climate change. By simultaneously examining temperature and salinity fields, this new work highlights that the observed changes in the ocean are consistent with human forcing of the climate.

The oceans constitute 71% of the global surface area, store 97% of the world’s water, receive 80% of all surface rainfall, and absorb 90% of the Earth’s energy. Salinity, along with temperature, determines the ocean’s density and therefore plays a vital role in guiding ocean currents from the equator to the poles. By redistributing heat around the world, ocean currents have a profound influence on global climate. Scientists monitor salinity in the world’s oceans to determine how evaporation and precipitation patterns are changing. To that end, it has been suggested that decreased salinity at high latitudes in the Atlantic is consistent with observed changes in precipitation in high latitudes. Ocean salinity is also a signature of the global hydrological cycle, which is one of the most important elements of the climate system. Human induced climate change leads to an increased polarisation of the global water cycle, causing arid regions to become drier and high rainfall regions to become wetter. A change in the water cycle poses a substantial risk to human societies and ecosystems, affecting food availability, stability, access, and use.

Salinity and temperature correlations related to human-induced climate change (Source: Pierce et al. 2012)

Pierce et al. (2012), using a technique called ‘detection and attribution,’ compared observed changes in salinity and temperature to 11,000 years of model simulations. Detection is a process of demonstrating that the observed changes in ocean salinity and temperature are substantially different, in a statistical sense, from the changes that may arise due to natural variability of the ocean-atmosphere system, brought on by volcanic eruptions, solar fluctuations, or regular climatic patterns. Attribution, on the other hand, establishes whether the detected changes in ocean salinity and temperature are caused by natural variability (internal or external) or external forcing, such as human-induced changes in atmospheric composition due to an increase in greenhouse gases or changes in land cover. The detection and attribution analysis is, therefore, a rigorous technique to verify computer model simulated changes in ocean salinity and temperature. The findings from this study show that the changes in ocean salinity and temperature over the top 125m are inconsistent with the natural causes of climate change. The observed changes can, however, be detected and attributed to anthropogenic forcing of climate change.

It is very likely that the results of this new study will contribute to the next report of the Intergovernmental Panel on Climate Change, scheduled to be released in phases beginning in 2013.

The research was funded by the United States Department of Energy and National Ocean and Atmospheric Administration (NOAA).

For more background, check out this video by Climate Central, explaining the relationship between ocean salinity and climate.

By Mona Behl, Visiting Fellow with the American Meteorological Society Policy Program

In this week’s Imaggeo on Mondays, brought to you by the photographer himself, Lukas Hörtnagl (University of Innsbruck, Austria) tells us about the ‘blue haze’ or ‘tule fog’ of California’s Sequoia National Park.

“Blue haze” by Lukas Hörtnagl, distributed by EGU under a Creative Commons licence

I was visiting the United States to attend the Fall Meeting of the American Geophysical Union in December 2011 and decided to stay four more weeks to visit some of the National Parks in California, Arizona and Nevada. Soon, it was obvious that each park seemed eager to look its best on camera. California’s Sequoia National Park was no exception.

This photo was taken in January 2012 while driving down the Generals Highway — a road that crosses the National Park and is named after two of its most famous trees, the General Sherman and General Grant sequoias — looking west/south-west at the western borders of the park. Further in the background is the Great Central Valley in California.

The thick ground fog visible in the photo is called ‘tule fog’ and typically forms during the winter months when longer nights result in an extended period of ground cooling. The combination of relatively high humidity (e.g. after rain events) and the loss of heat by radiation can lead to the formation of this fog, which can last for days. While the fog layer is cold, the air directly above is typically warm and — as you can see in the picture — clear. However, the visibility down in the valley was much better than it seemed from above.

By Lukas Hörtnagl, Biomet Innsbruck

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Today’s text is brought to you by the author of this impressive picture, Patrick Klenk (Heidelberg University, Germany).

“Wonderland” by Patrick Klenk, distributed by EGU under a Creative Commons licence

This photograph is part of a series of images which I took in Death Valley National Park on a brisk December morning in 2011. In this case, we were close to Aguereberry Point, a mountain viewpoint located at 1961m above sea level, overlooking the central part of this “vast geologic museum”. This was our  first trip to the Death Valley, and the scenery was unlike anything I would have expected, which was mostly due to a 5cm snow cover that had fallen the previous night. When we got to the viewpoint early in the morning, the last clouds were just moving out and the strong winds had created these delicate icy structures on shrubs, rocks and grasses, which instantly started to sparkle and glow as soon as the sun came out. Especially when viewed against a backlighting sun, one got the impression of an almost unworldly setting, seemingly defying gravity. It didn’t last for long, however – the sun melted everything away within just a couple of hours. Hence, this image truly was about being in the right place at the right time, about capturing a glimpse of an ephemeral winter wonderland.

The picture was taken with a Nikon D7000, using a 18-105mm lens. Aperture was f/11, with exposure of 1/320s at ISO 160 and a focal length of 105mm. Beyond the black-white conversion (using Silver Efex Pro 2), no further picture editing was carried out except for  adding a little vignette for emphasizing the subtle backlighting atmosphere of the central part of the image.

In my real life, I am a physicist, currently working at the Institute of Environmental Physics, Heidelberg University, Germany, on novel approaches for using Ground-Penetrating Radar for Quantitative Soil Hydrology.

By Patrick Klenk

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Geotalk, featuring short interviews with geoscientists about their research, continues this month with a Q&A with Dr Stephanie Henson (University of Southampton) who tells us about her work on marine ecosystems, and gives great advice to young scientists. If you’d like to suggest a scientist for an interview, please contact Bárbara Ferreira.

Dr Stephanie Henson

First, could you introduce yourself and let us know a bit about your current research topic(s)?

I started out as an undergraduate in physics at the University of Leicester before moving into oceanography with a Masters degree at the University of Southampton. After a couple of years as a science administrator, I moved back into academia with a PhD in oceanography, also at the University of Southampton. I did postdocs in America at the University of Maine and Princeton University, and now I’m a biogeochemical oceanographer at the National Oceanography Centre in Southampton, UK. I’m interested in how the physical environment affects phytoplankton and carbon uptake. Phytoplankton are tiny plants that live in the ocean and although they only make up 1% of Earths biomass, they absorb almost half of atmospheric CO2 and produce about half of the oxygen we breathe. They are also the base of the marine food web, and support fish, whales, etc. Most phytoplankton can’t swim and so are at the mercy of ocean mixing and currents which determine how much light and nutrients they receive. I’m interested in understanding how variability (on seasonal, inter annual and longer time scales) in phytoplankton and carbon uptake arises, and use a combination of satellite, ship, and model data to achieve this.

Earlier this year, you received an EGU Arne Richter Award for Outstanding Young Scientists for your ‘fundamental contribution to the study of marine ecosystems’. Could you summarise the research you have done in this area?

I’ve spent much of my career so far investigating how phytoplankton are affected by changes in the ocean environment, for example wind patterns, ocean mixing, eddies, etc. One of the clearest examples of these interactions is the annual ‘spring bloom’. Just as on land spring heralds a sudden greening of the trees and plants, in the ocean the phytoplankton bloom when conditions are right; an event which is very important for providing food to fish and other marine animals, but also for absorbing CO2 from the atmosphere. The year to year variability in physical conditions leads to variability in the timing, size and distribution of the phytoplankton bloom, which I’ve studied mainly with satellite ocean colour data. Bringing in situ data and modelling into the mix, I’ve looked at how longer term variability, such as changes in the North Atlantic Oscillation might affect phytoplankton.

A second strand of my research has been assessing the strength of the ‘biological carbon pump’ – a term that refers to the transfer of carbon from the upper ocean to the deep ocean where it is locked away out of further contact with the atmosphere for thousands of years. The pump is a key part of the global carbon cycle, but my recent work has suggested it may not be as large as once thought. This is worrying because it means our knowledge of a major planetary carbon flux is incomplete. I’ve also studied how the pump strength changes spatially in the ocean, which gives us some ideas for what might control its variability.

Among other topics, you are interested in “trends in ocean primary productivity“. Could you explain to us what ocean productivity is and how it can vary (due to, e.g., climate change)?

Phytoplankton use light and CO2 to photosynthesise and produce oxygen – this process is called primary production. Anything that alters the amount of light or nutrients that phytoplankton receive can alter primary production. Because of the need for light, phytoplankton live near the surface of the ocean. They get their nutrients from the water itself, but most of the ocean’s nutrients are in the deep, dark water. The amount of light and nutrients a particular patch of the ocean gets depends mostly on the physics happening in the ocean and atmosphere, which changes the amount of mixing in the upper ocean. Too little mixing and there won’t be a good supply of nutrients from the deep waters; too much mixing and the phytoplankton will be mixed into deep waters and won’t receive enough light. Climate change will lead to increased ocean temperatures, reducing the amount of mixing in many regions. This is predicted to result in a general decrease in ocean primary production, which might lead to a positive feedback loop: decrease primary production, decrease CO2 uptake, warmer planet, less ocean mixing, decrease primary production, and so on.

What are your future research plans?

I’m working in several areas connected to understanding variability in phytoplankton, for example combining data from new technologies to understand the spring bloom. We’ve recently deployed ocean gliders in the Northeast Atlantic, which can sample from the surface to about 1000m depth for months at a time, to investigate the physical processes that prompt the start of the spring bloom. By combining satellite data, which gives us information on the surface patterns of phytoplankton, with the glider data, which tells us about the vertical distribution, we hope to gain a whole new perspective on this long-standing question. I’m also investigating methods to detect signatures of global warming in time series of marine ecosystems. We have over 15 years of satellite data on phytoplankton, but it’s not long enough yet to easily distinguish a trend from the natural variability, so we’re trying out sophisticated statistical analyses, but also investigating some of the long in situ time series as well.

You have an impressive CV! At a young age, you are not only an active and successful researcher, but you are also leading a research group, teaching, and supervising PhD students. What advice would you give to young students looking to pursue an academic career in the geosciences?

The first thing I’ll say is going to seem obvious, but the second part of it maybe not so much. First, work hard. But not too hard! Personally, I avoid work on evenings or weekends unless it’s an emergency. I find that to be productive and creative, I need to step away from my computer regularly. I suspect the same is true for most people, so although it’s tempting to put in crazy hours when things get tough, try going for a long walk and having an early night instead – you might work more efficiently tomorrow!

I’d also advise students not to be afraid to challenge the status quo. It’s easy to accept the existing assumptions and paradigms, but I say ‘question everything’. Much of the time the existing paradigm will be correct (and in questioning it you will have learnt a lot), but sometimes you may spot a gap in our knowledge or reasoning. If you do, don’t be afraid to explore it – it might be the route to a new insight in your field!

Finally, I can’t emphasise enough the importance of supportive mentors to help you along the way. If your tutor or supervisor is a good mentor, cultivate the relationship and maintain it even if you move to another university. You may also meet academics in your field at conferences or meetings that you develop a rapport with. Don’t be afraid to pick their brains about career choices, or discuss ideas with them – most academics will be flattered to be sought out for advice.