As we come to the end of the MOOC, perhaps you are wondering how you can help to protect our seas and get involved with ocean science. First and foremost, take a few simple steps to minimise the effect YOU have on the oceans – there’s a great list of simple things you can do (and avoid doing!) here:

http://www.wildlifetrusts.org/blog/thewildlifetrustsblogger/2016/07/25/10-things-you-can-do-help-sea-national-marine-week-23-july-

If you want to go a step further, there are lots of citizen science and conservation projects going on around the UK which are free to take part in. Some are best suited for those who live by the coast but there are plenty which you can contribute to in a couple of hours or less – perfect for a day out at the seaside! Here’s a list to get you started:

Take part one of the Marine Conservation Society’s Beachwatch litter surveys and help to clean up:

http://www.mcsuk.org/beachwatch/volunteers

Conduct your own seaweed survey as part of the Natural History Museum’s Big Seaweed Search:

http://www.nhm.ac.uk/take-part/citizen-science/big-seaweed-search.html

Report a one off cetacean sighting or become a Sea Watch Regular Observer:

http://www.seawatchfoundation.org.uk/

Report basking shark, jellyfish, turtle and non-native species sightings:

http://www.mcsuk.org/what_we_do/Wildlife+protection/Report+wildlife+sightings

If you are a diver you can record your underwater encounters and report them to Seasearch:

http://www.seasearch.org.uk/

Organisations like the Marine Conservation Society and The Wildlife Trusts are always campaigning for better protection of our seas. Sign up to become a friend of Marine Conservation Zones and subscribe to the Marine Conservation Society’s Enewsletter to for regular updates and guidance on how to make your voice heard.

MCS Enewsletter sign up:

http://www.mcsuk.org/enewsletter/subscribe

Become a friend of Marine Conservation Zones:

http://action.wildlifetrusts.org/ea-action/action?ea.client.id=1823&ea.campaign.id=28581

Finally, there are lots of local projects going on around the UK which can’t all be listed here. Try searching online to see what’s going on in your area!

The post How can I get involved? appeared first on Exploring our Oceans .

Using this equation, we can predict that that the more CO₂ the oceans absorb, the more acidic they will become. We measure acidity using the pH scale. Remember, LOWER pH means HIGHER acidity.

But do the observations reflect this theory?

The answer is yes: Sea surface pH has decreased from 8.25 to 8.14 since the Industrial Revolution. This doesn’t sound like much, but the pH scale is not linear – it is logarithmic. So this seemingly tiny change in pH actually translates to a 30% increase in H⁺ ions in our seas. We call this phenomenon ocean acidification.

Biologists are very worried about the effect this will have on marine life. The problem is that a vast number of marine organisms build their skeletons and shells from calcium carbonate. But calcium carbonate dissolves in acidic solutions! Many researchers have showed that when these organisms are exposed to high levels of CO₂, they cannot build their shells/skeletons properly. You can prove this to yourself by doing a simple experiment at home – click here.

Below are some examples of research showing the effect of increasing CO₂ on various sea life.

Ocean acidification threatens the future of many marine creatures, and will have a knock-on effect for entire ecosystems. These ecosystems deserve to be protected not only for their beauty and uniqueness, but because we are a part of them – millions of people around the globe rely on the sea for food and income. This threat is another huge motivation to reduce our carbon emissions and take responsibility for our planet. Yet outside of the scientific community, not many people have heard of ocean acidification. Public awareness is key to shaping climate change policies. So now that you’re in the loop, spread the word!

The post Sour seas: How does carbon dioxide affect our oceans? appeared first on Exploring our Oceans .

Estuaries deliver sediments from rivers into the ocean, but they actually receive even more sediment back from the ocean. This means that all estuaries are slowly being filled in with sediment. That’s why economically important estuaries have to be regularly dredged to prevent ships from running aground.

Sediments are important because they contain a wealth of nutrients which support life within estuaries. But how do the nutrients get there? This is an important question for chemists and biologists alike. One source is the river water itself, which picks up nutrients from soils and weathered rocks. However, a much more important source is from estuarine vegetation like kelp, seagrasses, mangroves and marsh grasses. This vegetation contains a large amount of cellulose which makes it unpalatable for most herbivores. Instead of being consumed by them, most of it is broken down by detrital feeders like bacteria and fungi, which leads to a large amount of organic matter and nutrients being stored in estuarine sediments.

The meeting of fresh water and sea water also plays a role. Water circulation is special in estuaries due to the presence of these two water types, which do not completely mix due to differences in density. Nutrients are entrained from the dense underlying sea water into the fresher surface waters, and this allows an abundance of phytoplankton to flourish. When this phytoplankton dies, some will sink into the more saline layers and be carried back towards land where the organic matter will be recycled. This means that estuaries tend to retain the nutrients they contain.

Filter feeders like bivalves can be important in regulating the amount of sediments in estuarine waters. These animals capture sediments from the water column as they feed and deposit it in larger packets on the estuary bed. This process clarifies the water, allowing sunlight to penetrate and phytoplankton and vegetation to flourish. At the same time excess nutrients are also removed which could otherwise cause eutrophication, where oxygen is removed from the water by bacteria causing ecosystems to die off.

Estuaries are highly important in terms of inorganic (non-biological) chemical reactions as well. In fresh waters, organic and sedimentary particles carried by rivers don’t stick together because they have a net negative charge which makes them repel one another. When these particles meet seawater however, the cations from dissolved salts neutralise the negative charge and weak intermolecular forces take over, causing particles to become attracted to one another (these are collectively known as van der Waal’s forces – you can read more about them here). This aggregation of particles is known as ‘flocculation’, and is another important way in which the sediment load within estuaries is regulated.

Because the flow of fresh and sea waters oppose each other, the current where the waters meet is slower and sediment particles (both flocculated and otherwise) tend to accumulate here before falling to the estuary bed. This removal of particles from the water performs another crucial function which is of interest to trace metal scientists like myself. Many pollutant metals such as lead, chromium and cadmium like to ‘stick’ to these particles and often undergo reactions on their surfaces. This means that instead of travelling further out to sea, a large proportion of these metals are stored in estuarine sediments. Without these natural removal processes, the problem of metal pollution would spread further out to sea and threaten our oceans.

Estuaries face serious threats from anthropogenic pollution by several routes. Heavy metals and other poisonous industrial chemicals can work their way up the food chain and kill animals, whilst an over-abundance of nutrients due to fertiliser run off and sewage input can cause waters to be starved of oxygen. Dredging and land reclamation also threaten habitats above and below the water. A delicate balance must be struck in order to allow humans to utilise estuaries as transport routes and as a source of food and pleasure for years to come, whilst also protecting these unique and fascinating habitats. I hope this article has given you a new appreciation for estuaries!

References:

C.M. Lalli, T. R. Parsons, Biological Oceanography: An Introduction, 2nd edition (1997), Butterworth-Heinemann.

The Open University, Waves, Tides and Shallow Water Processes, 2nd edition (2000), Butterworth-Heinemann.

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For the past six months I’ve been working on samples taken as part of the Shelf Sea Biogeochemistry (SSB) project. Shelf seas are highly productive and absorb a significant amount of CO₂ from the atmosphere, but they are under threat due to anthropogenic disturbance and climate change. We want to know more about them so they can be better managed. In March I was lucky enough to go on an SSB cruise aboard the RRS Discovery.

On my cruise the trace metal team collected samples of seawater, sediments and porewaters in order to study elements such as iron, chromium and radium. We also did some experiments to find out how seawater and sediments interact with each other chemically. Levels of trace metals are so low in seawater that a clean lab with special ventilation and minimal metal components must be used to prevent samples from becoming contaminated.

It was also my job to measure the oxygen and pH levels in different sediment cores collected from the sea floor. These parameters are important to geochemists because other sediment components like metals and organics undergo interesting reactions when oxygen and pH change. This testing took place in a lab which is cooled to the temperature of the sea floor (about 8°C) in order to preserve samples while they are being worked on. I also assisted in extracting pore waters (the water between sediment grains) for trace metal analysis.

During the cruise we acquired some interesting data using spectroscopy and other techniques, but the process of analysing all of the samples collected during this cruise in detail will take months. I am also working my way through samples collected on other cruises from the SSB series. You can find an infographic with more details on how I am extracting chromium isotopic signatures from seawater here.

The post My Research, Part 2 appeared first on Exploring our Oceans .

Image credits:

Hammerhead shark: Galapagos Conservation Trust, http://galapagosconservation.org.uk/wildlife/scalloped_hammerhead_shark/

Copepod: Tracey Saxby, Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/imagelibrary/)

The post Chromium infographic! appeared first on Exploring our Oceans .

One answer is complexity. The oceans contain a myriad of living organisms, and witnessing so many unique creatures interacting with each other provides endless fascination. As a chemist, I will never cease to marvel at the multitude of different atomic combinations which allows this incredible system to exist and live. The most complex molecules that man can create pale in comparison to what nature can do!

I am also interested in the unique challenges and opportunities that the oceans represent. Looking at the bigger picture, the oceans provide millions of people with food, contain vast reserves of metals and minerals, and are even inspiring new medicines. To me, this means a responsibility for us all – figuring out how to make use of the oceans whilst still preserving and protecting them is a huge challenge for humanity. From a personal perspective, I believe the oceans are worth caring for and I want to contribute to that in whatever small way I can. Luckily this is a very enjoyable challenge, and I have been able to learn many interesting skills in pursuit of this goal both at work and in my spare time.

The post Heather Goring-Harford: What do the oceans mean to me? appeared first on Exploring our Oceans .

Today, we can measure dissolved oxygen levels accurately using shipboard sensors, so we have a pretty good idea of how oxygen levels vary through the water column. Most of the oceans are sufficiently oxygenated for aerobic life, although suboxic zones where the breakdown of organic matter occurs are also quite normal in places. There are even some locations like the Black Sea where complete anoxia at depth is natural.

But how does this compare to the past? It’s very difficult to be certain about what the climate was like very early in Earth’s history, but evidence from sulphur isotopes tell us that between 3.85 and 2.45 billion years ago, there was virtually no oxygen in the atmosphere or oceans. It’s thought that some bacteria might have been producing oxygen by photosynthesis during part of this time, but not enough to significantly influence the overall composition of the atmosphere. So, whilst there might have been small oxygen ‘oases’ where early photosynthetic bacteria were active in surface seawater, the deep oceans were probably completely anoxic.

Somewhere around 2.0-2.4 billion years ago, one of the most important climate shifts in Earth’s history occurred: the Great Oxygenation Event. This is widely thought to have occurred due to the production of oxygen by photosynthetic bacteria, but was also related to other changes in environmental chemistry at the time such as reduced fluxes of hydrogen sulphide from hydrothermal sites. The most well-known evidence of the Great Oxygenation Event is Banded Iron Formations (BIFs). These rocks form when iron reacts with oxygen and precipitates from seawater, forming thick bands of red/orange sedimentary rock.

Atmospheric oxygen continued to increase after the Great Oxygenation Event until it reached the levels we have today (21%), although some major fluctuations did occur in the interval. In response, the surface oceans slowly absorbed more oxygen from the atmosphere, although the deep oceans took longer to become oxygenated. There is still a lot debate about how quickly the deep oceans became oxic.

One very relevant feature of the ocean’s oxygenation history to modern environmental concerns is Ocean Anoxic Events (OAEs). The geological record shows that several times in Earth’s history, the oceans have returned to a state of anoxia for intervals of a few hundred thousand years. These periods are associated with global warming and worryingly, with mass extinctions as this graph shows:

So how do these OAEs happen? Picture this: a major volcanic event such as the formation of a large igneous province occurs, and large amounts of carbon dioxide (CO₂) are released into the atmosphere as a result. In response, surface temperatures rise and ocean circulation becomes sluggish as thermal stratification strengthens. Perhaps methane reserves in the deep ocean become destabilised and come to the surface, adding to the greenhouse effect of CO₂ and further warming the planet. On land, chemical weathering becomes more prevalent (also due to higher temperatures), leading to higher nutrient availability in the oceans. Biological activity increases, consuming oxygen in the oceans faster than it can be replaced. A state of ocean anoxia is almost inevitable in these circumstances.

This is just one idea of how OAEs occur. Whilst there is geological evidence for many of the events associated with OAEs, in many cases we are not really sure which are causes and which are consequences – it’s a ‘chicken or egg’ situation.

What we know for sure is that atmospheric CO₂ is on the rise due to anthropogenic activities. Runaway global warming due to this could cause another period of reduced oxygen in the oceans, if not total anoxia. There is some evidence that this might already be starting to happen, although the situation isn’t clear. Scientists only realised that ocean deoxygenation might be a consequence of global warming about 15 years ago, so it’s not something we’ve been monitoring for long. It does appear that wide expanses of the North Pacific have been declining in oxygen content for the past few decades, and the tropics may be experiencing systematic losses in oxygen as well. Furthermore, most climate models predict that dissolved oxygen levels will decrease by 1-7% in the future. On the other hand, there are many uncertainties in these models and studies from other parts of the ocean don’t show any clear trends at present. As with other modern climate change problems, the only way to prevent anthropogenic deoxygenation for sure is to cut CO₂ emissions.

References: Keeling, R. F., Kortzinger, A. and Gruber, N. Ocean deoxygenation in a warming world. Ann. Rev. Mar. Sci. 2, 199-229 (2010).

Holland, H. D. The oxygenation of the atmosphere and oceans. Phil. Trans. R. Soc. B 361, 903-915 (2006).

Hough, M. L., et al. A major sulphur isotope event at c. 510 ma: A possible anoxia–extinction–volcanism connection during the early-middle Cambrian transition? Terra Nova 18(4), 257-263 (2006).

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You are probably already aware of the concerns surrounding global warming, caused by the release of carbon dioxide (CO₂) from burning fossil fuels. Rising temperatures threaten to cause changes in sea level, ocean circulation and even dissolved oxygen levels. But how do CO₂ emissions affect the chemistry of our oceans?

It is thought that the oceans have absorbed up to half of the CO₂ emitted by burning fossil fuels. When CO₂ dissolves in water, it combines with water molecules to form carbonic acid. So the more CO₂ the oceans absorb, the more acidic seawater will become. Organisms like gastropods, bivalves, corals and some plankton have shells or skeletons made of calcium carbonate, which is affected by acidity. See for yourself what happens when a shell is exposed to acid with this simple experiment:

1. Take two clean glasses or jam jars (no lids!). Fill one with water and one with white vinegar. The vinegar is our acid.
2. Find two similar pieces of seashell, e.g. from a mussel or cockle. Put one in water and one in vinegar.
3. Observe what happens to the one in vinegar – what can you see?
4. Leave the shells for 24 hours and then compare.

You should see that the shell in water hasn’t changed much, but the one in vinegar has started to erode and break down. The acidic vinegar has attacked the calcium carbonate shell, and caused it to start dissolving. The bubbles observed in step 3 consist of carbon dioxide, a by-product of this reaction. Why not Tweet a photo of your experiment? Please tag with #FLOceans. Here are my photos – I used limpet, cockle and abalone shells:

Although the oceans won’t become as acidic as the vinegar in this experiment, only a small change will start to affect delicate organisms. We are already starting to see these changes, for example at the ALOHA station in the Pacific Ocean, just north of Hawaii. This graph shows how pH has decreased over the last 25 years at the station (pH decrease = acidity increase):

Not only does higher acidity erode existing calcium carbonate, but it also makes it difficult for organisms to produce more of this material. One study showed that this causes malformations in calcifying plankton. The top images here show normal development, and the bottom images show development under high dissolved CO₂ conditions:

The global consequences of ocean acidification could be extremely serious – the destruction of coral reef habitats and modification of ecosystems may have severe implications for fisheries, aquaculture, tourism and coastal communities. Ultimately the only way to slow the rise in ocean acidity is to reduce the amount of CO₂ in the atmosphere, either by cutting emissions or by removing it using controversial climate engineering.

For more information on ocean acidification, check out http://www.oceanacidification.org.uk/.

Reference:

Billé, R., et al. Taking action against ocean acidification: A review of management and policy options. Environ. Manage. 52(4), 761-779 (2013).

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On the most basic level, water is blue because of the way it interacts with light. When light hits the surface of the ocean, three things can happen to it:

1. Absorption. Light from the sun contains all colours, which combine to appear white. When this light reaches water, some of the colours are absorbed by water molecules and converted into heat energy, which warms the ocean surface. The diagram below shows that of the colours visible to the naked eye, red and orange are best absorbed. Absorbed light never reaches our eyes, so we don’t see these colours. These wavelengths also don’t penetrate very far into seawater, which is why underwater photographers require extra lighting to capture reds and oranges in photographs.

2. Scattering. When some colours of light reach the water, they bounce back off in every direction. In the diagram, you can see that blue light is not absorbed very effectively by water. Blue light is instead scattered, and some of the scattered light reaches our eyes. This is why we perceive the sea to be blue.

3. Reflection. Some light never penetrates the water itself, but bounces off the surface and directly into our eyes. This is how we see reflections on the surface of water. If this reflected light has already had some colours ‘filtered’ out by other objects such as the sky, you will only see the colours that have not already been absorbed. This is why on a grey day, the sea often looks grey as well.

The sea can appear a multitude of other colours for various reasons. If seawater contains lots of suspended sediment, it can appear brown or yellow according to local sediment types. It takes quite a lot of energy for larger sediment particles to be lifted into suspension, so the effect is most prominent where there are large waves and during storms.

Seawater can be also brown due to the presence of coloured dissolved organic matter (CDOM), often produced from the decay of detritus such as plant material.

From a biological perspective, plankton can have great effect on the colour of seawater. Phytoplankton contain chlorophyll for photosynthesis, and waters heavily laden with these species often appear green. Large phytoplankton blooms occur in spring and can sometimes be seen from space.

Pollution from sewage or fertilisers can provide sufficient nutrients for certain species to multiply extremely quickly. This phenomenon, known as eutrophication, is seen in heavily polluted estuaries and coastlines. The eventual die-off and decay of the bloom causes oxygen levels in the surrounding water to become severely depleted, wreaking havoc on local ecosystems and fishing operations.

Interestingly, not all phytoplankton blooms are green. Some species of plankton (such as certain dinoflagellates) cause red or orange blooms known as red tides. These can also be disastrous for local ecosystems as these plankton sometimes produce toxins.

Check out NASA’s website for more cool pictures of ocean colours taken from space.

If you enjoyed this article, you might also fancy finding out what causes the sea to smell the way it does – Compound Interest has a great article on this which can be found here.

The post Our colourful oceans appeared first on Exploring our Oceans .

Chromium is weathered from rocks, transported by rivers into the sea and deposited in ocean sediments. Along this journey, it undergoes different reactions which depend on the presence or absence of oxygen. These reactions cause some isotopes of chromium to be stored in sediments and rocks preferentially to others, and this creates an isotopic ‘signature’. By measuring these signatures in ancient rocks, we may be able to find out what levels of oxygen the chromium was exposed to, providing an indirect measurement of atmosphere or ocean oxygenation at the time the rock formed. We want to know more about how the oxygenation of the oceans affects climate and vice versa to help predict future changes, so this type of measurement should be very useful. The problem is, we don’t yet know exactly how much the oxygenation of seawater affects the isotopic signature of chromium, even in modern seawater. This means we can’t yet use isotopic measurements to their full advantage, but that’s where I come in! To fill this gap in our knowledge, I am measuring the isotopic signatures of chromium in modern seawater to see how they change in waters with different oxygen levels.

Because chromium is present at very low concentrations in seawater, sophisticated techniques and very sensitive equipment are needed to measure its isotopic signature. Few scientists have tried it up to now, so the first year of my PhD has involved lots of work in the lab trying to find the best way of measuring the signatures. Geochemists like me often work in specialist clean labs which are designed to keep out any particles and other contamination that could affect the measurements we make. This is the one I work in:

To extract the dissolved chromium from seawater, I do a redox reaction which involves adding iron to my samples. The reaction causes chromium and iron to come out of solution and form a solid precipitate. Here it is in action:

The colour change you can see is due to oxidation of iron. The reaction only takes a couple of minutes! After filtering the orange precipitate, I need to purify the chromium in it. I use column chromatography to separate chromium from other elements in the sample:

Most elements stick to the orange resin in the columns, but chromium passes straight through for collection. This process removes iron, so the samples go into the columns yellow (like the ones at the bottom of this picture) and come out completely colourless.

The next step is to analyse the samples using a mass spectrometer. The data from this machine needs to be processed using lots of calculations to get a final isotopic signature. This is done using some rather complex MS Excel spreadsheets, making my life a bit easier!

As a PhD student, I don’t spend all day in the lab and reading papers – there are lots of other activities to get involved in. Here at NOC, there are always seminars, conferences and other talks going on. They span a wide range of topics from submarine landslides to pterosaur flight, and everything in between! They can really help to broaden your scientific knowledge. It’s also good to share your own knowledge and skills with others by giving talks or helping out with undergraduate teaching. For some projects, there are opportunities to go out on research cruises, something which I am preparing for next year on the new ship RRS Discovery!

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