Lakes release gas too. In the latest paper freely available from our RELATED project, we show that the vegetation in and around lakes can play an important role in influencing how much of the potent greenhouse gas methane is produced by microbes. The story, led by our former postdoc Erik Emilson, has been covered by BBC News.
Congratulations to our former intern-extraordinaire Beth Smith who’s just published her undergraduate research on how mussels can both outweigh and interact with the effects of terrestrial to aquatic resource subsidies on nearshore lake biogeochemistry. The work was part of our larger NERC RELATED project.
The results are summarised below. Well done Beth!
Kurt Yakimovich, our ‘man in Canada’, recently produced this great video on his MSc research that runs in collaboration with our group. Check it out below:
It has been a busy summer for our NERC-funded project RELATED (that stands for Restoring Ecosystems by Linking Aquatic and Terrestrial Ecological Dynamics). The project aims to test experimentally whether the productivity of aquatic food webs increases with the quantity and quality of terrestrial organic matter deposited in nearshore delta habitats. It builds on our previous work that showed forests fuel the growth of juvenile fish by subsidizing the base of the aquatic food web. RELATED will also feature much more work on unlocking the microbial ‘black box’ at the base of the food web as well as better understanding how greenhouse gas emissions might change with surrounding vegetation. Inland waters are major sources of atmospheric carbon and predicting their responses to future change is of major interest (some great recent work here, here, and here).
We’ve now just finished launching the experimental platform behind RELATED. Over the last 8 weeks, we’ve had a team of 8+ working tirelessly to submerge artificial lake sediments in 3 lakes. This has involved collecting, mulching, and sifting organic and inorganic materials, mixing these at an industrial scale, and outfitting nearly 300 mesocosms with the appropriate sampling gear. By replicating our experiment in 3 different lakes, we’ll be able to study terrestrial-aquatic linkages along gradients in eutrophication and climate change – the main drivers of change in the world’s inland waters. We’ve also had excellent student help from Laurentian University’s School of Architecture work to design and build a network of sampling platforms that will allow us to work without disturbing our sediments.
Here’s the main team celebrating the deployment of the experiment in Ramsey Lake:
Our latest paper in the Proceedings of the Royal Society on the “jellification” of temperate lakes has gotten an impressive amount of on-line attention. At the time of writing this blog, Altmetric scores it as the 22nd highest ranking paper ever published in the journal. You can read summaries from the Washington Post, New York Times, Daily Mail, CBC, CBC Radio, and Yahoo, among others. I’ve also done four separate interviews this week with BBC radio stations (BBC Radio 5, BBC Wales, BBC Cambridgeshire). You can catch the latest, with the BBC World Service from the 26th of Nov, below:
The main finding of the paper is that a small planktonic animal named Holopedium glacialis has been dramatically increasing in two very different lake regions of Canada as the keystone grazer in these lakes, the water flea (Daphnia spp.), has been disappearing. Our results show that this is mainly driven by declines in lake water [Ca]. Daphnia need large amounts of Ca to build their body shell, while Holopedium surround themselves in a gelatinous polysaccharide “bubble”:
This jelly also protects Holopedium from predators. By contrast, Daphnia are increasingly susceptible to predators at low [Ca] because their ability to induce evolved defences is also impaired. Our analyses show how vanishing Daphnia have now left more algae uneaten for their competitors to exploit, allowing them to multiply in number. Many media reports have picked up on this as Holopedium liking ‘pollution’, with low [Ca] somehow being the result of this. But it is more in fact a legacy of pollution. While we have curbed industrial emissions and reduced acid rain, the historical depletion of base cations from the thin soils of the boreal shield, have left behind much lower [Ca] than present prior to industrial activity. Ca concentrations have consequently been falling across much of North America and Europe.
Joanna Wolstenholme, a third year NatSci undergraduate, has just wrapped up seven weeks helping our field campaign in Canada. She authored this entry, describing her experience.
Sudbury, on first inspection, is a rather spread-out mining town, inhabited by many trucks (most of them blue). However the more you explore, the more remarkable the town becomes. It is one of the few areas of the world where remediation has really worked, and the next generation will inherit a greener and cleaner city than the one that their parents inherited. This remarkable change, from a barren ‘moonscape’ caused by years of acid rain (Sudbury was once the world’s largest point source of sulphur dioxide emissions, thanks to large-scale nickel and copper mining), to an area with burgeoning forest cover and recovering lakes, is a great success story that the area can be immensely proud of.
With this backstory, Sudbury, with its 330+ lakes, makes an ideal experimental location for a group dealing in ecosystems and global change. Our study lake, Daisy Lake, is perfectly set up for studying the effects of terrestrial influences on aquatic ecosystems. Along its length, the shores and wetlands have recovered to various degrees. One catchment has even been limed – covered with calcium carbonate to neutralise the acidic soils, and so plant growth is relatively lush. Other areas, closer to the smelter at the north end of the lake, are far more barren; bare, stained rock predominates, with a few stunted trees.
In Daisy, we were studying eight stream deltas, each with very different personalities. At each site Erik and I measured algae, sediment, and water. This all sounds very easy in theory, but in practice (as with any fieldwork, as I came to learn) things were far harder and more complicated… and often involved some rather novel solutions. If nothing else, this placement has certainly given me plenty of opportunities to stretch my problem solving skills!
My first job was to build algae-collectors, which were plastic tubes with cut up swim floats attached from which 6 microscope-slides dangled from fluorescent string. These floated on the surface, but we also sank clay pot holders as another surface for algae to grow on. We left these in the lake (on a beautiful sunny day) at each of the deltas and then returned to collect them 3 weeks later. On a more high-tech note, we also made use of two chlorophyll fluorometers to characterise the algal species found in the water column and benthic layer. After several dry runs measuring the amount of algae on Erik’s office floor, we took them out to the lake, and used them at each of the deltas. The unseasonal amount of rain that Sudbury was experiencing, however, complicated things, and meant that in some sites Erik had to swim with the fluorometers, as we couldn’t reach the sediment from the boat.
As well as working on Daisy with Erik, I also helped Andrew collect additional data for his survey of terrestrial resource use by aquatic organisms. This meant going out to six other lakes around Sudbury, and six down in the Muskokas, to collect water samples, use fluorometers, and deploy and collect the microscope slide contraptions. Key to the project was collecting clean leaf and algal samples, to go off for stable isotope analysis, to allow Andrew to calculate the influence of the terrestrial systems on the lake ecosystems.
In order to grow clean algal samples without the influence of terrestrial DOM, we collected water from each of the lakes, then filtered it into jars and re-inoculated each jar with a small amount of unfiltered lake water, from which we hoped the algae would regrow. This seemed simple in theory, but involved hours of standing by a vacuum pump watching water drip through a filter. One night, we actually filtered water outside a hotel, so as not to set the fire alarms off! Safe to say we got many odd looks. However, the field trip down to the Muskokas was one of the best perks of the summer. We went down in September, almost at the peak of the colours changing, and had two lovely dry but crisp days. Driving down dirt tracks through beautiful forest, to find beautiful lakes to paddle out into was great fun, and a real adventure! It definitely offset the tedium of filtering.
At the end of my seven weeks here I am very sad to be leaving. It was a great experience, with plenty of messing about on boats, exploring new places, and making new friends. I have learnt a lot about the complications of fieldwork, how to solve problems on the fly with limited supplies, and just what really goes on behind those simple sounding ‘Materials and Methods’.