Forests feed lake life

Our latest paper has just appeared in Science Advances.  In it, we present widespread evidence that aquatic consumers use terrestrial resources depending on the features of surrounding catchments.  It is really nice to see this out as it caps the food web workshop we organised in Cambridge more than two years ago and includes data we collected during our summer 2014 field campaign.  There’s a nice write up of the work put out by our friends at the Cary Institute.

The work emerged out of our forest fuel fish growth story, which hinted that there can be a lot of variation in the extent to which lake food webs use terrestrially derived material, depending on the features of the surrounding catchments.  With funding from a NERC collaborative grant, our new paper managed to assemble the largest dataset to date of the isotopic composition of zooplankton and their associated food webs from across 147 lakes spanning the boreal to subtropics.  Our aim was to address the use of terrestrial resource in lake food webs once and for all.

Algae and land plants differ in their assimilation of heavy versus light forms of atoms such as carbon, allowing the ratios between these two forms to be used as dietary tracers.  Using these isotopic signatures, we discovered that half of all the zooplankton samples we amassed were comprised of at least 42% terrestrially derived material, but this was underpinned by large variation ranging from 11 to 83%.  Using some awfully complex stats, we go on to show that terrestrial support of zooplankton was generally greatest in lakes with long shorelines and surrounded by dense vegetation and rich soils.  This work now explains the large variation in terrestrial resource use by aquatic food webs and delivers a major advance towards resolving the ‘controversy’ around this process.

Rewinding the Tape of Life

Journal of Ecology Blog

If evolution happened anew, what would the present-day plant world look like?  That is, would the randomized processes that govern evolutionary change tell a different story? And particularly for plants which are sessile organisms, is the starting point of ‘who gets there first’ the most important of all?

Priority effects – the order and timing of species arrival into local communities – can affect ecological community structure and functioning, with profound effects for species persistence and ecological interactions (Chase et al., 2000; van de Voorde et al., 2011). As such, the arrival of different species at different times can dramatically alter the evolutionary tapestry of any given system on ecological time frames, but also in evolutionary time. In particular, the diversification of early arriving species can pre-empt available niche space to prevent the establishment, dominance or diversification of species that arrive later on down the road.

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A closed loop of ideas

1) Throughout this text, I will use the word “terrestrial” to refer to the planet Earth as opposed to “space”, which slightly pains my aquatic biologist heart.
2) As a lot of the talks had some link with plant sciences, I feel like, despite this entry being space or lake focused, it also has a place on this green and leafy blog!

This week, I was lucky enough to go to Lausanne, a small Swiss city on Lac Léman, to attend the MELiSSA Workshop. What is MELiSSA? As an ecologist, it is unlikely that you are acquainted with this European Space Agency (ESA) project, which stands for Micro-Ecological Life Support System Alternative. It was created in 1989 (read more on how it began here) and brings together European and Canadian partners from 13 different countries in an attempt to fulfill human needs in outer space via the development of life in closed systems. The main ideas include: recycling waste and carbon dioxide aboard spacecraft by using bacteria; and producing food, water, and oxygen in a regenerative way to keep costs low. Put in their words, it aims “at a total conversion of the organic wastes and CO2 to oxygen, water and food”.


Terrestrial lake eco-loop. Copyright: ESA.


What drew me to this workshop is that this closed loop is based on lake ecosystems, as depicted in the diagram above. Whether lake ecosystems are truly closed is debatable, and in my opinion is rather incorrect (I still believe in the importance of allochthony!). However, in the natural terrestrial environment, lakes are probably the system that comes nearest to the idea of a closed loop, due to their ecological isolation and the limitation of external inputs. In lakes, the processing of waste products via plant and algal metabolic activity fuels the regeneration of food, clean air, and pure water – and this is why the lake aquatic ecosystem is used as a model for MELiSSA.

Concretely, they try to reproduce this via the following compartmentalization of tasks:

I Organic waste degradation & solubilisation by thermophilic anoxygenic bacteria
II Carbon compounds removal by photoheterotrophic bacteria
III Nitrification by nitrifying bacteria
IV a Food and oxygen production by photosynthetic bacteria
IV b Food, oxygen and water production by higher plants
V The crew


Which recreates the loop:


The 5 compartments of the MELiSSA loop. Copyright: ESA. See Godia et al. (2002).


The two-day workshop brought together 140 participants from 21 countries, from academia and industry, who discussed solutions to issues associated with space travel. With more than 40 speakers, you can imagine the days were long, but invigorating, and made even more enjoyable by the quality of the tea breaks and meals (a giant parmesan filled with rice for lunch!). To give you an idea of the breadth of topics discussed, here are the titles of the 6 sessions that made up the workshop: 1) Waste processing, 2) Water recycling, 3) Air recycling, 4) Food production & preparation, 5) Chemical & microbial safety and 6) System tools. These covered subjects as seemingly divergent as food production and new food sources, clean showerheads, anaerobic digestion, human feces disposal, and hydroponic plant-fish interactions.

My thoughts about space research have always been that the money put into it could instead be used to solve terrestrial problems. Scientific terrestrial problems – feeding the world, conserving biodiversity, predicting the effects of global change – urgently need solutions. As an aquatic biologist, I have heard many times that the deep sea has been infinitely less explored than the surface of the moon. Why should we keep investing into space research then? Is sending men to the Moon or to Mars a sci-fi dream, a demonstration of our technological power, or a serious and, perhaps in the future, necessary escape from a damaged planet Earth? Whichever of these it may be, I have come to understand that spending money on what may first sound utopic is actually beneficial to our planet in much more concrete and terrestrially applicable ways than I ever imagined. What the conference taught me is that there’s a kind of closed loop of ideas: space research takes from ecology, and vice versa.

And indeed, there is no doubt that the vast majority of the research and new technologies discussed throughout the workshop aims to bring more sustainable innovations or alternatives to extant ones. Ultimately, the idea of the closed loop is about recycling: anything that is part of the loop needs to be reused, recycled, and regenerated. By incorporating this ecological idea into technological principles, the closed loop can also yield a new form of economy, a “circular economy”, whereby waste is limited and the value of products is retained. Of course, I am skeptical about some of the proposed projects – too utopic, not financially viable, no real advances made. For instance, I would love to dive in underwater gardens (large glass tanks maintained at supposedly constant temperature), but I don’t understand how they could ever be part of the solution to feed the world.

In addition to this little inner discussion I had with myself, what I can really take home from this meeting is a lot of new knowledge on microbial communities – how they interact among themselves but also with their environment, how they process nutrients, and how they can be studied. One question that particularly triggered my interest is whether prosperous and diverse microbial communities that can auto-regulate are less harmful, or risk-prone, than disinfected zones whereby resistant microbes have the potential to thrive and be pathogenic? I also saw how my current research could be applied in various ways. As a PhD student, not getting results can sometimes distract you from the focus of your project, and leave you wondering why you are there and for what purpose. Seeing the potential – both theoretical and applied – of my research, gave me a surge of motivation and new ideas. It also pushed me to think of subjects that had never even crossed my mind, namely the number of issues associated with space travel – microbial contamination, food and water supply, waste removal, breathing clean air…

Finally, I would like to say that my most valued moments of the workshop were occasions to exchange ideas with Mark Nelson. Mark was part of the first Biosphere 2 mission from 1991 to 1993 (if you don’t know about this 2-year closed loop experiment, in Arizona, with 8 crew members, I recommend reading about it) and is one of the founders of the Institute of Ecotechnics. I have to admit I was a little nervous about attending the workshop, fearing that I would feel out of place amongst all these engineers and businessmen. In the first few minutes upon my arrival though, I met Mark and felt like I was in the right place, and that I could learn a lot from this workshop. Mark is an ecologist – the academic son of H.T. Odum, and the academic grandson of G.E. Hutchinson – and has been involved with MELiSSA for many years. It was truly engaging to discuss space exploration, closed systems, systems ecology, urbanization and many other exciting or demoralizing topics. Special encounters like these can give large events a whole other dimension.

In the end, I came to the conclusion that environmental thinking can successfully be integrated into space activities, and can promote synergies between space and terrestrial research. I am glad I attended this workshop, which gave me space for thought as well as a taste of something new. And to open up the discussion: how do you feel about closing the loop?


Copyright: ESA.



Making sense of canopies

Béatrice Wedeux and David Coomes published a paper in Biogeosciences analysing how environmental factors and selective logging interact to shape the canopies of tropical forests. Using airborne laser scanning technology across a 750 km2peat swamp forest landscape in Borneo, the study reveals strong shifts in canopy height and gap patterns along environmental gradients linked to changing peat depth. In areas where logging roads were detected on historical satellite imagery, the canopy is lowered and has larger gaps, especially so on deep peat where tree growth is thought to be limited by low nutrient availability and waterlogging. The study identifies a close link between the height and the gap structure of tropical peat swamp forests at the landscape scale and reinforces the vulnerability of this ecosystem to human disturbance. The degradation of tropical peat swamps has been at the heart of climate negotiations in Paris, as emissions from fires in Indonesian peatlands over the last couple of months – exacerbated by a dry El Niño spell – approach the total annual emissions of Brazil (1.62 billion metric tons;


Airborne laser scanning allows the detection of openings at different height cross-sections of the canopies of old-growth and selectively logged forests.

Read online: Wedeux, BMM and Coomes DA (2015) Landscape-scale changes in forest canopy structure across a partially logged tropical peat swamp, BIOGEOSCIENCES 12(22):6707–6719, DOI: 10.5194/bg-12-6707-2015.

The future of environmentally-friendly farming?

Our first paper on the agri-environment has just appeared in this month’s issue of PLoS Biology.  This is an important piece for us as it provides a foundation for empirical work being carried out by several group members.

The paper essentially makes three main points.  The first is that we spend a lot more money subsidizing farming than trying to mitigate its environmental impacts.  We’ve tried to plot this out below.  What you can clearly see is that the purple (mitigation expenditure) is nearly invisible relative to what is spent on subsidizing farming (shown in the orange slices).

Financial support to farmers from taxpayers and consumers associated with agricultural policies as a proportion of the total value of agricultural production (VoP) at the farm gate.

The figure now provides what is essentially a map of the ‘perversity‘ of agricultural subsidies – showing where we spend money to do things that are often bad for the environment and costly to the economy.  A first step in reducing conflict between agriculture and the natural environment would be to do away with the subsidies in orange.

Continue reading

New multi-lake experiment launched

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).

Experiment behind the beautiful Living with Lakes Centre

New experiment behind the beautiful Living with Lakes Centre

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.

Artificial sediments with increasing organics from left to right.

Artificial sediments with increasing organics from left to right.

Here’s the main team celebrating the deployment of the experiment in Ramsey Lake:

Explaining the origins of species diversity

The July 2015 issue of New Phytologist has come out and its a doozy!  The entire issue features work on evolutionary plant radiations, drawing together a range of papers that summarize the current state of knowledge about “where, when, why, and how” plant radiations happened.  An editorial by Colin Hughes, Reto Nyffeler Peter Linder outlines the content of what will surely be a landmark issue for years to come!

Many, if not all, of these papers were presented at a symposium organized in Zurich that we attended with our New Zealand collaborators Professors Bill and Daphne Lee in June 2014:

We're somewhere in the crowd

We’re somewhere in the crowd …

For me, this was possibly one of the most intellectually stimulating meetings that I’ve ever attended.  Talks drew major figures in plant ecology, evolution, and systematics and really pushed the boundaries out on ‘diversification’ research.  The field itself is still arguably quite new, with many of the key questions synthesized in a 2008 paper by Peter Linder.  In fact, we have a PhD studentship available to follow-up some of these questions and build on what we talked about at the meeting.

You might have noticed that we even have a contribution in the New Phytologist Special Issue.  Our paper tests the mechanisms by which plant evolutionary radiations emerge and influence ecological dynamics.  We apply more of our expertise in structural equation modelling to focus on 16 species-rich genera in the alpine zone of New Zealand.

Diversity in New Zealand’s alpine.  Celmisia, Chionochloa, Dracophyllum, and Veronica all appear in this photo.

One of the most exciting aspects of our paper is that we’ve tried to reconstruct the niche space that each genus has occupied over the last 20 million years.  This is fairly ambitious and has involved tasks like reconstructing sea surface temperatures through the Cenozoic from isotopic measurements of foraminifera deposited in marine sediment cores, and then using these to estimate past land temperatures.  We’ve also had to consider that the alpine zone has grown immensely over time with uplift of the Southern Alps.  To do so, we collated radiometric dates of rocks and tried to infer their rate of uplift since the Miocene.

Overall, our results suggest that genera that colonized New Zealand earlier encountered more ‘vacant’ environmental space, which promoted species diversification and further occupancy of the environment.  Genera that occupied more environmental space were subsequently more dominant in present-day vegetation plots.  The key message is that time not only explains why diversity arises, but how this diversity influences ecological dynamics.  The Special Issue has many other fabulous papers, so do check it out!