Friday, March 19, 2010

Organic matter processing and retention

ResearchBlogging.orgI've already mentioned one of the papers from the big 25th anniversary issue of JNABS.  I've now read a handful of these papers, and they continue to be very interesting and a little bit annoying.  Why are they annoying?  Well, I like the review aspect of the papers, I don't like the "JNABS played X role in the development of X concept", because, really?  Who the hell cares?  This is a perfect example of the sometimes egocentric nature of scientists:  It isn't enough for something to be discovered or understood.  It must be clear that this person discovered or understood something.  And by extension, this society contributed this to science.  I know that the incentive structure of the entire scientific community is geared towards rewarding this kind of attitude, but that doesn't make it right.  If anything, it makes it more wrong.

But I digress.  Let's focus on "A review of allochthonous organic matter dynamics and metabolism in streams" by Tank and others (2010; full cite below).  Actually, because I know all these authors, I'm going to list out the others:  Emma Rosi-Marshall, Natalie Griffiths, Sally Entrekin, and Mia Stephen.  Frankly all these people are awesome, and so I fully expected this paper to be awesome.

I was not disappointed.

There is a hell of a lot of interesting stuff in here.  Lets bring out some of the highlights:

  • There have been a hell of a lot of leaf-decomposition studies.  Essentially, inverts and microbes are the big players, with other factors influence the effectiveness of those two main players.  Some of those other factors:  Pollution (by reducing invert populations/diversity and sometimes increasing microbial activity, temperature, and leaf species (even different hybrids have different decomp rates).
  • Biomonitoring using leaf decomposition (at least combined with invert measurements) might be a good way to measure ecosystem health or "stream integrity".  There are a lot of papers cited here that I'll have to read at some point (assuming I can get access).  
  • Although production to respiration ratios (P/R ratios) have often been used to determine allochthnous versus autochthonous production (whether or not a stream is heterotrophic or autotrophic), this is a more complicated assessment than was first believed (although the authors here don't fully explain why).
  • People have tried a lot of different things to measure organic matter retention:  using leaves, sticks, logs, particle analogs (waterproof paper cut into squares), plastic strips, wooden dowels, etc.  Why?  Because most small streams have energy budgets dominated by terrestrial inputs (at least, most small streams that have been studied).  Getting estimates of in-stream retention of little stuff (dissolved or just fine particles) has been a lot more difficult. 
As I said, there's a hell of a lot here, and I'm in no way going to reproduce all the interesting stuff here.  Those are just a few highlights.  However, it is worth pointing out that this kind of research is a natural extension of some of the oldest 'modern' ecological studies that have ever been done.  What do I mean by modern?  I mean studies integrating abiotic and biotic components to understand large-scale phenomena.  Maybe 'modern' isn't the right about awesome?


This paper offers a pretty comprehensive overview of organic matter dynamics in streams, including decomposition, metabolism, and budgets.  Prior to doing any research on this topic, I would recommend reading through this to get a good historical perspective.

Tank, J.L., Rosi-Marshall, E.J., Griffiths, N.A., Entrekin, S.A., & Stephen, M.L. (2010). A review of allochthonous organic matter dynamics and metabolism in streams Journal of the North American Benthological Society, 29 (1), 118-146 : 10.1899/08-170.1

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