Friday, October 28, 2011

Interesting papers: Wind in Kansas and spider-hopping rivers

  • I wrestle quite often with whether or not to use this blog space to criticize individual papers or presentations.  On the one hand, I feel that scrutiny is a critical part of science, and we should point out all the problems with studies that make them questionable.  On the other hand, actual people are really sensitive to criticism.  I most cases, irrationally sensitive.  I can't count the number of people who got upset about criticisms they received, even when (as far as I can tell) those criticisms were both justified and constructive.  I'm certainly not immune to this myself.  Anyway, thinking about this kind of thing occasionally keeps me from posting.
  • I'm a little too close to this issue, but Kansas Chapter of the Nature Conservancy has published a paper in PLoS ONE mapping out areas where wind development in Kansas will and will not cause environmental problems.  I imagine this paper (and analysis) will become very politicized.
  • River-crossing spiders in Madagascar.  Are they catching bats and birds?  Holy cow.  The paper is actually about the evolution of this ability.
  • Here's a connection I've seen people talk about but never really quantify.  How does the source of carbon to stream biota (allo vs. auto) affect their mercury load?  Since mercury is associated with carbon, you would think the kind of carbon is important.

Tuesday, October 25, 2011

Ecosystem function in a brown world    I highlighted this paper a few days ago as looking interesting, but after reading it, I felt like expanding a bit.  The paper is by Rubbo et al (2011, Aquatic Sciences) and is entitled "Species loss in the brown world:  are heterotrophic systems inherently stable?"
   Before I get into this paper, I think it is probably worthwhile to put this in some sort of perspective.  There are a few fundamental, objective units in biology.  One of these is the cell, one is the individual.  Within a particular ecosystem, in a particular point in time, another might be the species.  Species definitions get confusing when you start thinking about them over evolutionary time-scales or across huge ranges.  In most settings, it is pretty clear that individual cricket frogs form a distinct and unified group when compared to (for instance) Daphnia magna.  In the minds of old-school natural history biologists, and the general public, species are important.  The whole idea of biodiversity is rooted in the idea that more species is somehow better.
   However, when people started thinking about ecosystem functions (nutrient cycles, primary production) and ecosystem services (carbon sequestration, food production, waste disposal), it was trickier than you might imagine to connect biodiversity to these ecosystem processes and products.  Some research suggested it is particular species, rather than diversity that drove ecosystem function.
   The impression I get (although I'm certainly not an expert) is that certain species are thought to be more likely to have big effects on ecosystem processes than others:  Species that dominate overall biomass, top-predators and other 'keystone' species.
   So what did they do in this paper?  Well, essentially they were extending these relationships between ecosystem processes and community composition into very heterotrophic ecosystems:  Forested vernal ponds. These ponds probably don't get a lot of sunlight, so not a lot of primary production.  Instead, most of the system's energy comes from material that falls in from the nearby terrestrial system.
   The authors have done quite a bit of work on these systems.  They decided to see what would happen if they removed the top predators out of these vernal ponds.  So the authors removed all the frogs and salamanders from 12 ponds, and then added them back in to a randomly selected subset of those ponds.
  The really surprising thing is that nothing seemed to happen.  The "ecosystem processes" that they measured (essentially production and respiration) varied a lot, but didn't vary in response to the presence of these frogs and salamanders.  The authors speculated that because this is a heterotrophic system, the base of the food web (being microbial) has such high turnover that changing grazing pressure wasn't able to affect the overall movement of energy up the food web.  Hence the title suggesting the "Brown world" is more resilient.  That sounds good, but doesn't that suggest algae based systems would be very resilient?  Have these kinds of studies been done in streams (which are also heterotrophic)?
   This is a perfect example of a nice study that is simple, easy-to-understand and extremely well-written.  I don't usually think of Aquatic Science as a top-tier journal, but if this is the caliber of paper that is routinely published there, then I feel like I need to change my thinking.

  Michael J. Rubbo, Lisa K. Belden, Sara I. Storrs-Mendez, Jonathan J. Cole, & Joseph M. Kiesecker (2011). Species loss in the brown world: are heterotrophic systems inherently stable? Aquatic Sciences

Wednesday, October 19, 2011

So many interesting papers: Stream fragmentation and the end of NABS.

  • I think I mentioned before, but the North American Benthological Society elected to change its name during the last annual meeting (last Spring).  I don't think changing the name was a horrible idea by any means (the "North American" part is semi-ridiculous and "Benthological" doesn't cover everything the society/journal covers), but it feels really weird to think of NABS as now being SFS (Society of Freshwater Science).  Anyway, this is the last issue of JNABS you will ever see published.  From now on, the journal is Freshwater Science.  Considering there are already journals out there going by the name Freshwater Biology and Freshwater Ecology and Aquatic Sciences and Aquatic Ecology (all of which are comparable or not as good as JNABS), I feel like Freshwater Science now is part of a group as opposed to standing out.  At any rate, I can't imagine this will affect the quality and appeal of the articles published, which is a good thing because....
  • ...JNABS always seems to have articles I'm really interested in.  Just published is a whole special issue on fragmentation in low-order streams (link goes to the intro).  I'm really glad I know longer have to keep a lengthy file on stream obstruction literature just to argue with watershed districts wanting to build dams, but I'm still interested in how connectivity affects ecosystem function.  As far as I know, hardly anyone has looked at that.  Most studies, like these, are focused on simply establishing community composition changes as a result of impoundments.  That's definitely useful, and you can extend that into functional changes in ecosystems, but not directly as far as I know.
  • Burning to prevent tree invasion is pratically gospel in many parts of the central U.S.  I'm not entirely sure why, except that alternative methods of preventing tree invasion seem more difficult and costly (and usually it probably is).  However, this paper in Eco Apps suggests just removing the trees is sometimes sufficient. 
  • Again, the papers I'm mentioning in these bullet-posts look interesting, and I've read the abstracts.  In some cases I've even read the whole paper before posting here.  However, I'm not really evaluating the significance of these papers to the literature or the appropriateness of the methods.  In this case this is particularly true.  This seems really, really cool.  I just don't quite know what it means.
  • Linguistics is pretty cool.  I hardly ever read anything about the topic, but every time I do I find it fascinating.  Like this about word order and the first language of humans.
  • I think my contract (ha!) says I have to point out anything I see that involves spade-foot toads.  In this study, the authors show that the rapidity with which an individual undergoes metamorphosis doesn't really seem to affect the age at which they reach maturity.

Monday, October 17, 2011

Interesting papers: The search for paleo-shoreline caves, burning through carbon reduces N accumulation, and more!

  • I'm not going to lie.  This paper, on how increasing temperature affects nutrient ratios, is in my queue, but I haven't read it yet.  So I shouldn't try to briefly tell you how amazing it looks or that I think it is great...because theoretically it might not be.  But here I am, telling you I think it looks really interesting and I can't wait to read it!
  • I'm fascinated by predator effects that don't involve the predator actually touching or directly interacting with the prey.  I'm particular fascinated by this in stream ecosystems, where I would assume the "smells" of predators would be pretty quickly diluted, but it seems like these effects continue regardless.  At any rate, here's a neat paper on "non-consumptive" effects of predators.  The authors point out, these aren't necessarily non-lethal
  • This article on the search for paleo-nearshore caves in Bermuda is really fascinating.  Kinda amazing how many areas we really still don't know much about. 
  • I've never heard of the term "brown world" used to describe heterotrophic ecosystems before, but I guess it makes sense.  Also very interesting to see that removal of a top predator in this kind of ecosystem apparently doesn't do anything.   
  • Ok.  Really, I haven't read any of these papers in detail yet.  I'm just skimming them and pointing out how interesting they look.  When I read through these, I may include detailed reviews on a few of these.

Caddisflies through time
I recently had a paper from a co-worker (Jason Veldboom) come across my semi-ridiculous RSS feed.  This paper does something a little bit different than any other publication I've seen:  Follow the elemental composition of a population and its (presumably) primary food resource through time.  
The study is straight-forward, in that the authors simply sampled a filter feeding caddisfly larvae and seston through time.  There's interesting stuff all over this paper.  First off, there are 4 streams sampled here, and initially, the caddisflies from those 4 streams have very different nutrient ratios.  As the caddisflies prepare to emerge, however, the nutrient content in all the streams converges.  The paper can't really pinpoint why this is (are all the larvae without this nutrient ratio dying?), a lot of the difference seems to be driven by carbon content (i.e., fat and energy reserves).  
Secondly, the sheer difference in mass among sites is pretty astonishing.  At the beginning of the study, one of the streams has caddisflies that are >3 times bigger than the other streams!  These are streams with virtually identical thermal regimes, in close geographic proximity and we're talking about a single species of caddisfly.  Why would one stream have individuals who start out their life-cycle with such a massive size difference?  This study really can't even address that, but it is definitely interesting.
Third:  A handful of previous studies have sampled particular species in different locations and generally found minimal differences in elemental composition.  This is really the primary form of evidence in favor of a homeostatic model when it comes to elemental composition in invertebrate consumers.  I've never been a fan of these studies being cited as compelling evidence for homeostasis, because although the presumption is that food quality differs among locations, there's no guarantee that's true.  Further, the evidence from experimental manipulations almost always finds biota are more flexible in their elemental composition.  This study actually suggests even finding a lack of variation among sites might be luck all the way around, since only at the very end of their aquatic life-stage (just at pupation) did these caddisflies have similar elemental composition.
Finally, the whole point of the paper is to look at whether growth in these caddisflies is affected by the imbalance between consumer demand and the nutrient composition of the available food resources.  The surrogate for this imbalance is the imbalance between elemental composition of consumer and food (seston), and it does appear to be related to growth rates (at least for P).  However, these relationships are week (R2 ~0.16-0.25).  I imagine this is because this estimate of elemental imbalance is probably only a crude reflection of the imbalance between demand and available nutrient ratios.  
Overall, this paper was excellent.  I'm interested to see other studies on how elemental composition changes though different life-history stages.  I'd be particularly interested to see how tropical and temperate species compare, since energy storage for low-productivity winter months seems likely to strongly affect elemental composition in temperate biota.

Veldboom, J.A., & Haro, R.J. (2011). Stoichiometric relationship between suspension-feeding caddisfly (Trichoptera: Brachycentridae) and seston Hydrobiologia

Thursday, October 13, 2011

Interesting Papers: Trophic levels matter, recharging aquifers, and a special issue on intermittent streams!

  • I saw Mary Power talk last night at UW-La Crosse.  Dr. Power is famous for having demonstrated the effect that trophic cascades can have on aquatic ecosystems.  She did this study where she showed adding fish to a mesocosm can decrease algal production, even though fish preferentially feed on algal grazers.  The reason is that fish aren't very good predators on these algal grazers (they hide effectively), but they are very good predators on invertebrate predators, which are themselves good predators of the algal grazers.  So the fish wipe out the intermediate predators and the grazers go crazy.  And what shows up here in my reader today?  An interesting article about a similar predator-induced cascade in the wolf-coyote-fox chain.  Very interesting. 
  • This paper on fish in a tropical river demonstrates the importance of floodplain nutrients (even when inundated for just a short time) on highly mobile big fish.  I'm not sure why people who build dams don't understand this, but river regulation is just plain bad for most fisheries. 
  • Recharging aquifers using surface water has become a bit of a hot topic.  There are lots of concerns about the quality of the water going back into the rock (does it have contaminants or not?).  I wasn't aware of any real scienctific studies exploring any of these issues, but now I am
  • Oooh look!  Apparently there's a special issue on intermittent streams being published in Aquatic Sciences.  As far as I can tell though, the only thing published so far is the foreword.  Looking forward to the rest of the articles getting out there.

Wednesday, October 12, 2011

Interesting Papers: Inadvertant management, dissolved organic matter in large rivers, and other cool studies

  • Sometimes management with the best intentions can result in active detriment to an intended beneficiary.  Take this example of supplemental feeding for a European eagle:  The supplemental feed contained pharmaceuticals, so the eagles that were given the supplemental feed were actually worse off than those who weren't. 
  • I haven't read this paper on DOM dynamics in large rivers yet.  But I wouldn't exactly be true to my dissertation work if I didn't get it read in the next couple of days.  I'm not aware of other studies that have followed the dynamics of DOM in such a large system with anything like this kind of detail, so this seems like it could be very interesting.
  • I don't often see social and economic studies in the journals I follow, but this study on the cost and distribution of benefits associated with heat relief is fascinating.  I think environmental justice is a really interesting topic (I'd love to teach a course on this) and this paper is a perfect example of how it fits in with ecosystems services.
  • I don't usually dig through Nature or Science directly, but last week's Nature Podcast made me realize I'd missed an essay co-authored by one of my favorite researchers, Jim Elser.  The essay is about peak phosphorus and I think it is fascinating that nobody, or at least almost nobody talks about phosphorus in the mass media.  I kinda wonder if we'll solve this problem more efficiently and effectively because it isn't a popular press story, as opposed to the other big biogeochemical problems (our over-production of C and N). 
  • In case anyone was wondering, here's the list of journals that show up in my feed reader.  You won't see Nature or Science on there, because the number of things those journals put into their feeds are just overwhelming, and much of it isn't very interesting to an ecologist (not that I'm just an ecologist).  I keep up with the Nature and Science stuff from the podcasts and word of mouth.  I also get L&O's table of contents delivered to my inbox.  I'd like to get the Journal of Great Lakes Research easily, but every time I subscribe to the feed, I end up getting every journal published by their publishing company.  I also get Frontiers in print, because it comes with the membership to ESA.  Anyway, if your article comes out in one of these journals, and I randomly think it looks cool, I'll try to mention it here:
    • Oecologia
    • Journal of Ecology
    • Fundamental and Applied Limnology
    • AFS Transactions
    • Biogeochemistry
    • Hydrobiologia
    • Environmental Science and Technology
    • Aquatic Sciences
    • NABS (actually NABS is now the Society for Freshwater Science...not sure if I updated the feed or not!)
    • Freshwater Biology
    • Functional Ecology
    • Journal of Animal Ecology
    • Ecology
    • Ecology Letters
    • Aquatic Ecology
    • Proceedings of the National Academies of Science
    • Proceedings of the Royal Society (B)
    • Oikos

Tuesday, October 11, 2011

I'm so confused: Comments and Rebuttals in ES&T
So on October 5th, this article by Liao and Kannan entitled “Widespread Occurrence of Bisphenol A in Paper and Paper Products:  Implications for Human Exposure” popped up in my google reader (from the journal Environmental Science and Technology).  Hmm... I glanced over the article, there’s a bit more exposure risk than I thought apparently.  Then, October 10th...5 days later...a comment/rebuttal (warning .pdf) and a reply to that comment and rebuttal appeared in my reader.  So, I’m amazed this comment and reply system happened so quickly.  The actual publication dates are slightly different than the dates the articles appeared in my reader (September 23rd for the article and Sept. 28th for the comment), but are we supposed to seriously believe the journal reviewed the original comment, solicited a reply from the authors, and then reviewed that in 5 days?  
If you actually read the comment you might have a hard time understanding why it was published at all.  I’m not sure the comment makes any sense.  The author of the comment essentially makes two points:  1) the authors of the paper refer to an exposure as being “several orders of magnitude” lower than a reference, when in fact the exposure is “140 thousand fold lower” than the dose and 2) the authors cite a WHO report in saying that some studies have reported adverse responses to extremely low doses of Bisphenol A, but in fact the WHO report doesn’t include those studies as part of its hazard characterization.  
Really?  Neither of these criticisms makes any sense!  Point number 1 is really just an issue of semantics:  140 thousand fold lower is several orders of magnitude lower.  Would the commenter be content with “many” instead of “several”?  The exposure is a lot lower, and marginally different methods of calculating the exposure simply show the same thing.
The second criticism completely misses the point.  Just because the WHO report doesn’t use those studies in its hazard assessment doesn’t mean those studies don’t exist (and apparently they are referenced in the WHO report).  Maybe it would have been better to cite those papers individually:  Is this really worth the publication space to point out?
Even if these were legitimate concerns (and I can’t understand how they are), they are completely irrelevant to the point of the paper (these are merely details discussed in setting up the context of the findings).  
The thing is, this comment is not about science and it isn’t even directed at the authors.  This comment is clearly for the benefit of the “various activist groups” referenced in the last line of the comment.  Why is this comment published again?  I get that there are groups out there who are going to use this article to re-enforce their belief about how the world works and the dangers of Bisphenol A, but those people aren’t necessarily interested in reality anyway, and they probably aren’t reading the minutiae of a technical journal like ES&T.  
Are these guys going to count this on their CV?  Can I just add a few publications to my CV by writing weak criticisms of published papers?  
Or should I just keep this stuff on my blog that nobody reads?

Liao C, & Kannan K (2011). Widespread Occurrence of Bisphenol A in Paper and Paper Products: Implications for Human Exposure. Environmental science & technology PMID: 21939283