by Ana Samperiz Vizcaino, PhD student at Cardiff University and ICY-LAB cruise scientist

The Earth is in constant change. Over millions of years it has gone through consecutive periods of cooling and warming, with successive changes in seawater temperature, sea-level and ice sheet’s extent. Oceanographic instruments only provide records (of temperature, salinity, pH, …) from the last few decades. So, how do scientists know what the ocean was like thousands of years ago?

Historians and archaeologist use archives to decipher certain aspects of ancient civilisations. So do oceanographers, but they use a different type of archives. Marine archives, such as ocean sediments, corals and shells have been widely used to reconstruct past ocean conditions. Geochemical analysis can shed light on several environmental and hydrographic parameters. For example, the composition of the oxygen atoms within the carbonate (CaCO₃) skeleton of these animals can be used to estimate the seawater temperature in which they lived. However, the use of these marine archives is complicated and have some limitations. It is for this reasons that there is a constant search to expand the suite of archives that can be used to understand the history of the oceans.

In a new paper, published recently in Earth and Planetary Science Letters, we explore the geochemistry of stylasterid corals. This family of deep-sea corals, although known since the 19^th century, has barely been studied previously. Stylasterids are fascinating creatures that build branching calcareous colonies of a few centimetres high, despite their polyps (the living tissue in charge of defence, feeding and reproduction) being only ~ 2-3mm in size. Furthermore, they are the only known coral group able to build their skeleton out or aragonite or calcite (or even both!) and whether they can serve as marine thermometers was unknown until now.

More than 90 stylasterid specimens were collected during 10 different oceanographic expeditions, from the North to South Atlantic and the Galapagos islands (including the ICY-LAB cruise in 2017). We measured and examined the oxygen isotopes within the stylasterid skeletons and created their first temperature calibration. Calibrations acts as a sort of “Rosetta Stone” for oceanographers. In this case, it informs us of how much the amount of oxygen isotopes within the coral skeleton will change as a result of temperature variations. They are the first step needed towards reconstructing historical environmental conditions.

Our results demonstrated that seawater temperature is recorded in the skeleton of stylasterids. They showed that oxygen isotopes in these organisms is a more precise temperature proxy than in other deep-sea corals. While questions remain open regarding the cause of these differences, and we do not fully understand the biochemical processes involved in coral skeletal growth, this is great news for oceanographers. This work raises the potential use of stylasterids to produce records of past seawater temperature. And although more work will be needed to combine other geochemical analysis and improve the quality of stylasterid coral records, this work lays the first stone.

Article citation: Samperiz, Ana, Laura F. Robinson, Joseph A. Stewart, Ivo Strawson, Melanie J. Leng, Brad E. Rosenheim, Emily R. Ciscato, Katharine R. Hendry, and Nadiezhda Santodomingo. “Stylasterid corals: a new paleotemperature archive.” Earth and Planetary Science Letters 545 (2020): 116407

The first paper from the European Research Council project Isotope Cycling in the Labrador Sea (ICY-LAB) has been published in Progress in Oceanography.

The aims of the ambitious ICY-LAB project were to investigate the influence of meltwater, coming from the Greenland Ice Sheet, on the supply of nutrients to the oceans and how this, in turn, impacts marine biology. Dr Kate Hendry and her international and multi-discipline team have published a new paper showing how they used geochemistry, together with physical, biological, and geological data, to gain a holistic insight into the cycling of these important nutrients.

The scientific crew spent about five weeks at sea in 2017, mostly near the western coast of Greenland, sampling waters, sediments and marine life using a range of cutting-edge technologies.

For example, a Remotely Operated Vehicle (ROV) took high-definition, real time videos of the seafloor and samples of marine life, water and sediments.

Their paper highlights the importance of glacial meltwaters, combined with shelf currents and biological production, on biogeochemical cycling in these high-latitude regions over a range of timescales.

Vigorous biological uptake in the glacial fjords keeps the surface concentration of key dissolved nutrients needed for algae, such as nitrate, phosphate and silicon, very low. However, sediment particles from the glaciers reach the shelf waters, albeit in a patchy way, and are then rapidly transported away from the shore.

These particles, together with the remains of algal shells and biological material, are rapidly dissolved and cycled through shallow marine sediments. This means that the seafloor is a very important source of nutrients – especially silicon – to the overlying waters.

Future changes in the supply of these reactive, glacial sediments, as well as changes in the shelf currents that transport them, will have a profound impact on the nutrient balance and ecosystem structure in the fjords and coastal waters, and potentially even further afield.

This study shows how geochemical and oceanographic analyses can be used together to probe not only modern nutrient cycling in this region, but also changes in glacial meltwater discharge through time.

Reference:

Hendry, K.R. et al. (2019) The biogeochemical impact of glacial meltwater from Southwest Greenland. Progress in Oceanography.

Accessible version can be found on Zenodo, or here.

The chemistry of sponge skeletons records the chemistry of the oceans, but may also reflect their health and growth patterns.

Sponges are very simple animals that live attached to the bottom of the seafloor or freshwater lakes. Many types of sponges produce their skeletons from individual elements (called spicules) from a glassy material, silica. This means that these sponges need to take up dissolved silicon in order to grow.

We’ve known for a few years that sponges incorporate different forms of silicon, or isotopes, according to the concentration of dissolved silicon available to them. Spicules can be picked out from marine sediments, analysed, and used to investigate the chemistry of past oceans.

The ICY-LAB team, together with Kerry Howell at Plymouth University and another EU funded project SponGES, have recently published a review paper summarising what we know about sponge silicon isotopes. We also present new data from sponge grounds in the North Atlantic (including the Labrador Sea) to show that, whilst the availability of dissolved silicon is the main control on the isotopes within the sponges, the health and growth of the sponge also plays an important role. This means that we can use isotopes to track, for example, how silicon is recycled around within dense sponge grounds.

The paper is published in Quaternary Science Reviews, and is accessible here.

Kate Hendry, March 2019

A study led by a team of isotope geochemists and glaciologists from University of Bristol shows the importance of subglacial weathering on the export of silica from glacial systems and how differences in rock weathering can alter the geochemical signature of the silica that is released.

Glaciers and ice sheets have been shown to play an important role in nutrient cycles, including through the export of silica. Silica is a key nutrient for some types of algae, such as diatoms, which form the basis of many aquatic ecosystems and are responsible for carbon storage on a global scale.

In the study published in Geochimica et Cosmochimica Acta (accessible version Hatton-et-al-2019), the researchers measured meltwaters from two Greenlandic glaciers – Leverett Glacier (Southwest Greenland) and Kiattuut Sermiat (South Greenland). These glaciers vary in size (~600km² compared to 36km²) and the rocks beneath each weather in different ways. By measuring silica concentrations, silicon isotope composition and major ion concentrations of the meltwaters, the team have shed light on the subglacial processes occurring and have produced a conceptual model of how the two systems differ.

They wanted to determine:

• If the distinct isotopic signature previously measured in Greenland was consistent in a different glacial catchment;
• What processes are causing this distinct isotopic signature;
• To produce a new conceptual model of the subglacial system by considering the changes in this isotopic signal over the melt season.

The study found that both Greenlandic catchments have an isotopic signature that is distinct from non-glacial rivers, despite their size differences. But there are differences between the catchments, which appear to correspond to differences in the weathering processes that are occurring under the glaciers themselves.

By combining the silicon isotope composition measurements with major ion concentrations, the team found that the two catchments have contrasting weathering regimes. Leverett Glacier is larger and so waters are likely to spend a longer time under the glacier, resulting in enhanced silicate mineral weathering. Whereas Kiattuut Sermiat is much smaller and acts more like a small alpine glacier, dominated by carbonate weathering over the melt season. The difference in weathering regime may impact the isotopic signature, as silicate weathering will lead to the formation of new, distinct solids, which will can react and dissolve – given enough time.

The study also considers the importance of the high rates of physical erosion in these systems, which results in finely crushed rocks, also influencing the geochemistry of meltwaters.

There is still a lot of work to be done to continue improving our understanding of glacial weathering and how they impact the nutrients exported in meltwaters. However, this work builds on work done recently by Dr Jon Hawkings and team, which shows the impact of past ice sheets on the global silicon cycle.

The research team are continuing to work on other glacial systems to investigate whether the patterns seen in Greenland are consistent globally. By combining further field studies with laboratory experiments, they hope to build on this study and provide the community with a better constrained silicon isotopic composition of glacial rivers.

This work is part of the European Research Council Funded project ICY-LAB, led by Dr Kate Hendry, which aims to provide insight into nutrient cycling, biomineralization, and the taxonomy and biogeography of siliceous organisms in an ecologically important region near Greenland. It also works towards the Leverhulme trust funded project led by Professor Jemma Wadham, exploring the role of sub-ice weathering on the silica cycle. These projects will consider how these glacial meltwaters travel through fjord systems, to predict the fluxes of glacial silica exported into the open ocean.

Blog post written by Jade Hatton, January 2019

Ice sheets of the last ice age seeded the ocean with silica

New research led by glaciologists and isotope geochemists from the University of Bristol has found that melting ice sheets provide the surrounding oceans with the essential nutrient silica.

Read our press release here!

Barium? Why would you want to measure barium in seawater?

Barium is a metal, and is dissolved in seawater in very low concentrations – for every litre of seawater there’s only about 0.00001g of barium. This amount isn’t fixed and varies around the ocean. Scientists have noticed that barium seems to correlate with other things in the ocean, for example the nutrient silicic acid (dissolved silicon) and alkalinity (which is basically the amount of ions in the water). Linked to this, barium has been thought to be useful in the Arctic as a tracer of river input (especially in winter when there’s not much biological activity that can also take up barium). However, this use of dissolved barium hasn’t been explored fully, and there haven’t been any studies to look at how dissolved barium behaves from one season to the next.

In a new paper, published in the Journal of Geophysical Research Oceans, we investigated barium in seawater and sea-ice from the Arctic. We collected samples during the Norwegian funded N-ICE2015 project, which was set up to study the physics, chemistry and biology of sea-ice in a changing Arctic. The Norwegian Polar Institute led the expedition, freezing their ship – the R/V Lance – into sea-ice north of Svalbard and taking a lot of measurements and samples as it drifted through the Arctic.

The barium measurements showed that there was no simple relationship with freshwater input, even in winter when biological activity was very low. This points towards an important process – likely within sea-ice – that is controlling barium distribution. Whilst this observation puts a question mark over using barium as a river tracer, our results do highlight the importance of understanding the chemical reactions that go on within sea-ice: in a changing world where sea-ice is diminishing, not only are we fundamentally changing the physics of the ocean but also the chemistry, with knock-on effects on marine biological production.

Read the full paper here.

Hendry, Katharine R., Kimberley M. Pyle, G. Barney Butler, Adam Cooper, Agneta Fransson, Melissa Chierici, Melanie J. Leng, Amelie Meyer, and Paul A. Dodd. “Spatiotemporal Variability of Barium in Arctic Sea‐Ice and Seawater.” Journal of Geophysical Research: Oceans (2018).

On March 23^rd, the University of Bristol hosted the IsoGlace workshop about novel isotope systems in glaciated environments. The workshop was organised by ICY-LAB’s Kate Hendry to coincide with a visit from UoB Benjamin-Meaker fellows Ellen and Jon Martin, from the University of Florida Gainsville, and featured talks from glaciologists and geochemists about how we can use isotopic measurements to understand glacial processes today and in the past, with a view to how these systems might change in the future. The talks (which included some exciting new ICY-LAB results!) were followed by discussions on the key questions, and how we might be able to address them through future innovations and collaborations. The university welcomed visitors from all around the UK, including colleagues from Southampton, UCL, Imperial, Nottingham and Cambridge. The day was a great success, and everyone left brimming with ideas!

Many thanks to the Jean Golding Institute and the Cabot Institute at the University of Bristol for funding, and to the School of Geographical Sciences for the use of their lecture theatre and facilities.

by Timothy Culwick

A new method of identifying old sponge specimens using DNA mini-barcoding.

Sponges are some of the most diverse and varied of the aquatic invertebrates with about 7,000 species described so far (Hooper 2002). Their success and morphological variability results in major problems with specimen identification. Due to similarities in hand specimen features a microscope is often needed to apply the appropriate Order let alone species separation. This difficulty is compounded in deep marine environments where much of the data come from camera drop images or broken fragments from trawling.

In Marine Biodiversity, Cardenas and Moore (2017) describe a new Geodia location on New England sea mounts and test a new way of specimen identification using mini-barcodes.

In the North Atlantic there are large sponge grounds on the slopes and shelves with most of the biomass stemming from the Geodiidea and Ancorinidae families. The grounds are both potentially ecological and environmentally important due to their size and extent. Geodiidea form the largest of the sponges in these grounds with single sponges getting up to 1m in diameter. Whilst comparatively easy to identify from large undamaged specimens due to its external morphology, broken or small specimens are much harder to separate. The damaged and diminutive species currently rely on spicule morphology which is difficult for non-specialise.

DNA Barcodes for Geodia species in the North Atlantic have been studied before (Cardenas 2013). They looked at the Folmer cytochrome oxidase subunit I (COI), 28S and 18S. of which both 28S and COI were unique for each species. Although due to slow evolution, identification of close species is limited (Schuster 2017). 18S was reported to be unique for four species but identical for two others. 18S has been previously noted to be conservative and therefore not useful for barcoding. However, this study relies on material to have no degradation of the DNA. Here we run into a problem with whole barcode sequencing. There is a limited number of specimens due to the challenge of collection at the depth and many were collected before DNA sequencing was possible. This is particularly true for most holotypes. These specimens were, and most still are, preserved using methods that degrade DNA making this type of analysis impossible.

The new specimens described by Carden and Moore (2017) were fixed in formalin which breaks down DNA so were unable to obtain a full-length barcode. They tried extracting two mini-barcodes the universal mini-barcode (=first 130bp of the Folmer barcode) and the Depressio-mini-barcode (= last 296bp of the Folmer barcode). Both barcodes hold the advantage of using an established barcoding database, so time and effort is not required to create one. The universal mini-barcode was obtained for five out of eight specimens. As with the full barcode it could not distinguish close species but importantly they all unambiguously identified the Geodia genus. This level of identification although superficially arbitrary for an organism within this phylum this is very helpful. The Depressio-mini-barcode was as sensitive as the full-length barcode with these specimens. However, it has not been used as a tool for identification on other sponges so should be treated cautiously. The potential sensitively suggested from this study is very striking and would be of great interest to look at further.
The most interesting part of this paper is what they went on to do next: they tried this mini-barcoding approach on two old specimens which would usually be considered unusable for DNA analysis. The first was a 11-14yr formalin fixed specimen from which they retrieved 100-300bp sequences. The second was a 161yr old dry holotype where two mini-barcodes were obtained. These hints of a method to open up the large proportion of collections to potential analysis which would otherwise be unusable. However, only two old specimens were tested and only one of the mini-barcodes can be considered reliable at this time. I don’t think the authors when far enough with this avenue of the paper to extrapolate the value of this technique as far as they have. There is great potential to increase the reliability of the sponge barcoding data and to look at many phylogenetic and taxonomic questions (Erpenbeck 2016). It would have been interesting to have tried with multiple samples to give an idea of the reliability and frequency of which results can be obtained. This is an interesting new avenue of DNA sequencing and could yield valuable results, but it needs further work to become the staple tool that is suggested.

Bibliography

Cardenas, P., & Moore, J, (2017), First records of Geodia demosponges from the New England seamounts, an opportunity to test the use of DNA mini-barcodes on museum specimens: Marine Biodiversity, pp 1–12.

Cardenas, P., H. T. Rapp, A. B. Klitgaard, M. Best, M. Thollesson, and O. S. Tendal, (2013), Taxonomy, biogeography and DNA barcodes of Geodia species (Porifera, Demospongiae, Tetractinellida) in the Atlantic boreo-arctic region: Zoological Journal of the Linnean Society, v. 169, p. 251-311.

Erpenbeck, D., M. Ekins, N. Enghuber, J. N. A. Hooper, H. Lehnert, A. Poliseno, A. Schuster, E. Setiawan, N. J. De Voogd, G. Woerheide, and R. W. M. Van Soest, (2016), Nothing in (sponge) biology makes sense – except when based on holotypes: Journal of the Marine Biological Association of the United Kingdom, v. 96, p. 305-311.

Hooper, J., & van Soest, R., (2002), Systema Porifera: A Guide to the Classification of Sponges.

Schuster, A., J. V. Lopez, L. E. Becking, M. Kelly, S. A. Pomponi, G. Woerheide, D. Erpenbeck, and P. Cardenas, (2017), Evolution of group I introns in Porifera: new evidence for intron mobility and implications for DNA barcoding: Bmc Evolutionary Biology, v. 17.

And so, we’re nearly there!  We’ve sailed across the Atlantic, from our final station on the southern tip of Greenland all the way back home. We’re currently sailing through Irish Waters, due to pass by the Lizard sometime in the early hours of tomorrow.

We’ve had an incredibly busy, and successful, expedition (and I think that we’re all in need of some rest!).

We have collected or filtered approximately 28,000 litres of seawater; over 50 metres of marine sediments; and 1551 biological specimens (across 10 Phyla). The ROV dived for over 186 hours (over a week!) and we surveyed an area over twice the size of Wales…

During that time, we ate 1000 kg of carrots, 400 kg of potatoes, 280 l of fruit juice, 52 kg of baked beans, and went through 2000 tea bags. We also ate one whole bag of frozen broad beans.

But aside from all the science we meticulously planned, what are some of the concluding thoughts of the scientists onboard?

Highlights of ICY-LAB

George: Preserving handfuls of deep-sea life in jars of ethanol..

Shannon: Conducting CTD collections and delegating responsibility- I liked being the boss! I loved the dynamic of the Night Shift!

Veerle: The giant rays and the squid attack we saw on the ROV footage was really cool to see!

Adam: The friendships forged during the coldest water sampling stints on the deck through the night. As well as the beautiful sunrises!

Ana: Something I won’t ever forget is the moment we saw the seafloor at 3000 metres for the first time- it wasn’t like anything I’ve seen before.

Claire: Searching the seafloor for samples was great, and finding carnivorous sponges was a definite highlight for me.

Grace: Conversations with Dave Edge, and dancing in the deck lab with Allison whilst slicing sediment cores!

Hong Chin: The integration of the whole science team was great!

James: A particular morning off the coast of Nuuk when a beautiful sunrise emerged and the whales came out.

Jake: Seeing freshly-made maps of the seafloor, and meeting strong currents off southwest Greenland which made for very interesting sailing! Also, escaping from the cold biology room each time!

Michelle: Seeing awesome deep-sea animals, and being in the ROV van!

Rebecca: I never thought I’d de-goo a bamboo coral.

Amber: Filtering 6000 litres of seawater!

Marcus: Seeing the sun rise over Greenland with new and old friends.

Steph: That moment in Nuuk when the sun rose and the whales came out was unforgettable.

Laura: Dougal requesting Thai Fish Curry for dinner constantly.

Kate: It was great how the whole science team gelled so well together, and made the whole experience awesome!

Allison: The very first gravity core that came up with more than 5 metres of sediment was great.

I’m glad I brought:

George: A multi-tool.

Grace: Tea and chocolate!

Kate: My slippers.

Shannon: Hard drive space.

Laura: A coffee machine and down jacket!

Rebecca: Warm fuzzy hoodies.

Adam: A journal and sketchpad.

Ana: Earplugs.

Michelle: A thermal onesie.

Veerle: My cruise notes from previous cruises.

James: Headphones and chocolate.

Allison: Music speakers.

Jake: A tweed jacket.

Marcus: A boiler suit, my DSLR camera, and high-fit waterproof trousers.

Claire: My boiler suit for the cold room.

Hong Chin: Hair ties.

Steph: Thick socks.

Amber: A bath mat, and the game Jungle Speed!

Things I wish I brought:

Ana: A boiler suit.

Shannon: More shoe options.

Veerle: My music collection.

George: More ‘normal’ clothes.

Adam: Chocolate and tea.

Rebecca: Snacks.

Grace: A jet ski!

Kate: My cat.

Laura: A cosy jumper.

James: Shoes and boiler suit.

Michelle: Music speakers.

Allison: A ‘big-ass’ telephoto lens.

Jake: Earl Grey tea.

Marcus: Another 2 terabytes of data space, and a lapel microphone.

Hong Chin: A far-range camera lens.

Steph: Binoculars.

Amber: A more extensive playlist for the chemistry lab!

Things I didn’t end up using:

Kate: Seasickness tablets.

George: A load of books there wasn’t time to read!

Ana: I was too tired to keep a journal, so I didn’t need that!

Shannon: My waterproof trousers.

Adam: Seasickness tablets.

Allison: My sunhat!

Veerle: My swimsuit.

Laura: Swimming gear.

Rebecca: Surprisingly, I never wore my warmest winter jacket.

Michelle: Two pairs of sunglasses were unnecessary.

James: Shorts.

Jake: Swimming shorts, flip-flops.

Marcus: Waterproof coat, flip-flops.

Hong Chin: A thermos flask.

Steph: My camera.. I can rely on everyone else’s lovely photos!

Thanks to all the scientists, technicians, and all the crew of the RRS Discovery for a great scientific adventure!

And thank you for reading our cruise blogs – please do keep reading to find out about all our updates.

The ICY-LAB Team

The ICY-LAB science crew on the front deck of RRS Discovery! (Photo credit: Martin Bridger)