I am in Raleigh, NC for the 2017 Society of Freshwater Science Meeting. I arrived here late last night and this is my first full day at the conference. My twitter feed has exploded with lots of tweets about the talks with hashtag #2017SFS. Instead of joining the tweets, I think it is a good idea to write something in a little more detail and share my thoughts on what I have learnt today in this blog.
Given my interests in biogeochemistry, I was mostly hopping between the macrosystem session and the biogeochemistry session today. Thus, what I am going to write will mostly be based on what I learnt from talks in these two sessions.
1. Conceptual synthesis on fundamental ecological concepts. It is so refreshing to see studies using streams as a model system to advance general conceptual understanding of ecology. The talk by Xiaoli Dong discussed the effects of template (e.g. riffle vs pools, upwelling of groudwater) and self-organization (i.e. feedbacks between algal community and nutrient availability) on patterns of nutrients availability in streams. The idea of counterbalance between local and long distance feedbacks was inspiring. This talk reminds me the Science paper by Chris Klausmeier on the regular pattern of vegetation and the Theoretical Population Biology paper by Ben Bolker and Stephen Pacala on the moment equation method describing spatial pattern formation. My advisor Ford Ballantyne presented his idea of extending the concept of thermal performance curve to element fluxes in streams. Streams are excellent systems to demonstrate/investigate general principles of ecology. Yet I feel we haven’t fully realized such potential. I believe there is a huge opportunity to do this in the future
2. Efforts to conduct broad scale synthesis. One effective way to achieve generality in ecology is to synthesize studies broadly. Jim Heffernan synthesized stream metabolism all over the place and showed distinct differences, especially in ecosystem respiration, between streams with or without human influences. Ryan Hill presented the Lake catchment dataset that includes hydrologically related landscape quantities. These broad synthesis of data and exploration of pattern are promising ways to generate a more general understanding of streams. There is a great opportunity to push forward in this direction. We have a lot of data to be analyzed!
3. Advancements and refinements in methodology. While many people emphasize the importance of ideas and argue that great methods do not compensate for crappy ideas, great ideas do not compensate for crappy methodology either. It is nice to see we keep pushing the rigor of methodology. For example, Rob Payn presented a theoretical analysis to show potential problems of the existing TASCC method. I have a keen interest in this topic as I have been working on the methodology analyzing pulse nutrient release data in my statistics master thesis research. There is still a lot work to do to figure out a rigorous yet easy to apply method to estimate nutrient uptake rate in streams. Hillary Madinger presented gas exchange measurements using Ar and SF6. Her work showed that gas exchange rates measured using these two tracer gases could deviate from the relationship prescribed by Schimdt number scaling (potentially due to presence of bubbles). Using Ar could be advantageous for metabolism estimates as its diffusion behavior is similar to O2 and therefore introduces less error using Schimdt number scaling. In my opinion, the influence of bubbles and how it affect our modeling of metabolism is something worth further investigation. Not only does bubbles influence measurements and calculation of gas exchange rate, it can also influence the effective saturation deficit. There are also several interesting talks related to phosphorus. Matt Trentman talked about influences of the form of phosphorous on estimated update rate. Whitney Beck showed in a meta-analysis that the form of phosphate salt could influence the effect size of nutrient addition on algal growth. It is something I haven’t thought about before. Being careful with the chemical we use in the experiment. It matters.
4. Opportunity to combine multiple perspectives in understanding nitrogen cycles in streams. Several talks presented analyses of watershed scale nitrogen removal and retention. For example, Ashley Helton used findings from the LINX II project and analyzed the nitrogen removal based on different shapes of stream network. Wil Wollheim used distributed sensors to estimate nitrate retention in a watershed. There are also several talks on a more mechanistic understanding of nitrogen cycles in streams. James Guinnip showed that nitrogen release from mussel beds stimulated nitrification and denitrification in streams. Erin Eberhard‘s talk on the co-occurance of nitrogen fixation and nitrification in streams challenged the conventional wisdom that these two processes usually don’t occur simultaneously along nitrogen availability gradient. I see a great opportunity to combine forces here. The broad scale analyses have mostly used simple equations to describe nitrogen uptake. The detailed transformation of different forms of nitrogen could be important. Combining mechanistic understanding of the nitrogen cycle with watershed level modeling could be very promising.
5. Variability is ubiquitous. What we think is constant may not be that constant. Amber Ulseth talked about the highly variable temperature sensitivity of GPP and ER in an alpine river network. This is something I have thought about a lot. Temperature sensitivity of ecosystem processes is hard to get and may not be that universally constant (i.e. ~0.35 eV for photosynthesis and ~0.65 eV for respiration). It is so satisfying and somewhat proud to say that I have read every single paper cited in Amber’s presentation. If you are also interested in temperature sensitivity of stream carbon cycle and you want to read more on it, here is a very brief reading list I created.
That is all I have so far. Thanks to all the great presentations today. I look forward to great talks and posters tomorrow. Maybe I will have another post like this after all the talks tomorrow.