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

Watershed land use and nutrients

The widespread problems associated with cultural eutrophication are well-known.  Essentially, humans dump a lot of biotically important elements into water, and the resulting algal and bacterial dynamics render those waters pretty unfavorable for native species and desirable species (i.e., you get a lot of fish kills and stinky water).

A big source of those nutrients is agriculture.  Row-crop agriculture, in particular, is a huge source of nutrients to streams and rivers (and ultimately lakes and the ocean).  When people discuss these topics, they tend to focus on the raw quantities of the most important nutrients:  Phosphorus and nitrogen.  There's good reason for this:  Typically, adding phosphorus [pdf] to lakes causes eutrophication all by itself.  So it is certainly true that the quantity of nutrients added is important.

However, the ratio of nutrients that is added can also be important, particularly when nutrient inputs aren't at ridiculously high quantities.  The importance of nutrient ratios in determining the function and species composition in aquatic ecosystems is an area of on-going, intense research (including some of my own).  However, at the watershed scale, there haven't been a lot of studies documenting what controls the ratio of nutrients.  Agriculture, of all types, typically gets treated as the same, and typically is linked to particular elements.

I've had a paper rejected recently on the watershed controls over nutrients, and one of the criticisms was that I didn't put it into the appropriate context.  Well...that's a problem.  So I'm taking the time to go back and re-read papers I've already read and reading for the first time some papers that I probably should have read.

One of the first ones on my list is also a relatively older paper, by Arbuckle and Downing (2001; full cite below).  For whatever reason, this one didn't sink in the first time I read it.  It is a note, rather than a full article, so it is shorter, but it is very good.  Essentially, one of the authors, in a previous paper modeled the amount of nutrients in cow manure, and found that the N:P ratio is actually pretty low, whereas the runoff from  row-crop agriculture is pretty high.

Why does it matter whether the N:P ratio is high or low?  Haven't we discussed Liebig's Law?  Well, we have, but I'll recap.  Algae (and all life) is composed of N and P (and a bunch of other stuff) and that N & P is used in a particular ratio.  So if you've got tons of N, but very little P, then you won't be able to use all the N because the amount of P is insufficient to build the proteins and so forth that you need to grow (the reverse is also true, and you can pick any two biotically relevant elements and play the same game).

We typically think of "pristine" streams and rivers and lakes as having a pretty high N:P ratio, meaning there is more N than they can use.  So if you add more P, you get more growth from algae and bacteria.  Hence, algal blooms (bad news!).  What Arbuckle and Downing (2001) pointed out is that the ratio of nutrients coming off different agricultural systems varies tremendously.  Sure, a farmer may be pouring fertilizers onto his fields, but what is in the fertilizer?

So the authors went out and measured N:P ratio in a bunch of streams and related it to the agricultural practices in the watershed.

The unusual result is that the N:P ratio of material coming off of these intensely fertilized agricultural systems has a very low N:P ratio (i.e., an N:P ratio you would expect to see in a pristine system) whereas the N:P ratio of export from intensely grazed lands will be much lower (i.e., an N:P ratio more typically associated with huge growth in algae and algal blooms).

That's a pretty counter-intuitive result.  You typically look at pasture lands as being less damaging to both the terrestrial and aquatic habitats than row-crop agriculture.  And maybe even here they are, but not in terms of nutrient ratios.

I think the key here is in where the study took place;  Iowa.  There really wasn't anywhere that the authors could go in that state without dramatic nutrient pollution in terms of sheer quantity.  Most of their watersheds were greater than 50% row crops.  As the authors point out "Most Iowa lakes are eutrophic or hypereutrophic..." (p 972).  However, as the authors point out, the differences in nutrient ratio between the row-crop and animal agricultural systems may cause differences in the algal species that becomes dominant in a system.

I interpret this as:  Well, you may get a bloom, but there's a big difference between an algal bloom and a 'harmful algal bloom'.  The former acts by starving the water of oxygen when all those algal cells die.  The latter actively poisons the water.  Good winds or the right conditions will completely alleviate the effects of an algal blooms caused by a 'non' harmful species, but you are going to have dead fish and irritated people if you end up with Karenia brevis (one agent of the notorious red tides).

To Summarize:

Not all agriculture is created equal, at least in terms of nutrient export.

Arbuckle, K.E., & Downing, J.A. (2001). The influence of watershed land use on lake N: P in a predominantly agricultural landscape Limnology and Oceanography, 46 (4), 970-975

My Research Part II: Elemental Imbalances

I discussed previously the rather important Law of the Minimum. Essentially, that law states that growth is controlled not by the total of resources available, but by the scarcest resource (limiting factor). As with most biological principles, this law was derived from agriculture. Those raising crops all over the world were in the habit of shifting huge amounts of manure from feedlots to crop fields with the hope that whatever they were adding would cause the crops to grow more. In fact, in most cases, the crops would grow quite a bit more if just a single nutrient were added. And that's why the history of industrial fertilizers is really a history of how people can add nitrogen and phosphorus to soils.

At the same time that farmers and other agricultural experts were discovering that adding a few pounds of ammonia had the same effect as adding a hundred pounds of manure, ecologists were going around and trying to figure out what the limiting factor was for a whole bunch of plants and animals living in the wild. Over time a number of trends began to emerge and embed themselves into the background of ecological thinking: Autotrophs tended to be limited by nitrogen in terrestrial systems and phosphorus in aquatic systems, large mammals tended to be limited by food energy more than nutrients, etc. And so people tended to focus on particular elements because of their 'obvious' importance to particular processes.

In fact, some quite prominent research looking at how ecosystems function was done by looking pretty much entirely at a single element. One of the most famous and fascinating researchers of the early 1900s was Ray Lindeman, who spent his entire, short career studying how just 1 element (Carbon) was cycled in a bog. And this was and is somewhat interesting, but a little bit of common sense should cut in at some point and begin to wonder: Why just carbon? Is carbon being cycled in a form that is only carbon? The answer, of course, is that materials that contain carbon (like leaves and bugs and soils) also contain lots of other elements. All those elements are being cycled at once, in far more complex and interacting dynamics than you would ever even understand existed if you considered only one element.

(Side Note: Why was Ray Lindeman so interesting? Well, he was the first person to do anything like this, his papers essentialy began the field of ecosystem ecology, and he died tragically young before he even completed a postdoc. I'm sure I'm not the only ecologist to have read other papers from his lifetime, read his papers, and wondered in a somewhat dumbstruck amazement as to whether the entire science of ecology was set back a solid 20-25 years by his premature death.)

Let's imagine the biological parts of the carbon cycle for a moment. Atmospheric CO2 is taken up by plants, which are eaten by herbivores, who are eaten by predators. Along the way some plant material falls off and turns into soil, as does the feces and bodies of the animals. Within the soil, bacteria burn all that carbon for energy, releasing CO2 into the atmosphere, which goes back to the plants again. But what determines the amount of CO2 a plant takes in? If CO2 is the limiting factor, then the amount of CO2 taken in will be related to the maximum growth rate of the plant. But what if the amount of nitrogen in the soil is the limiting factor? Does the plant keep taking in more CO2 than it can use? Or does it taken in just as much CO2 as it can use with the amount of available nitrogen? Do different plants do different things?

The underlying problem here is that sometimes (probably most times) the resources available to an organism are not the ones that are optimum for its growth. To go back to the Liebig's barrel analogy from two weeks ago (here), organisms have no reason to build a long stave out of CO2, when they can only build a short one out of nitrogen. When an organism is faced with resources that do not match its elemental demands, we refer to it as an elemental imbalance. A big chunk of ecological stoichiometry is determining how elemental imbalances come to be, how organisms react to them, and how they influence the cycling of elements.

Let's explain some of the possibilities a little here. Let's go back to our hypothetical plant, and let's give it a name. Let's call it a mustard plant. Our hypothetical mustard plant is growth-limited by nitrogen in the soil, but has enough of everything else, and has a huge abundance of CO2 (because the atmosphere is essentially a limitless source of the stuff).

The first question is: Why? Why did the mustard plant evolve to need more nitrogen than was available here? There are lots of possible explanations for this, but one of the key issues is that chemical processes that make life alive are fundamentally constrained. It simply isn't possible to create a protein molecule without using some nitrogen. In many cases, the nutritional needs of an organism are determined not by evolution or biology, per se, but by the fundamental nature of the universe. These fundmental constraints make living organisms relatively homeostatic (that is, their body elemental composition doesn't change), at least compared to non-living materials.

The next question is: So what is this little mustard plant going to do about it? The answers to this depend a lot on the context of how they are asked. For instance, a continued shortage of nitrogen over evolutionary time scales might result in mustard plants evolving to minimize their nitrogen demands or possibly mustard plants will develop ways to extract more nitrogen from the soil. Alternatively, mustard plants might use that extra CO2 in other ways. For instance, many plants create secondary defensive compounds that consist of carbon compounds with little or no other nutrients. These defensive compounds may make the plant poisonious or unpalatable.

Finally, we might wonder: What is controlling the amount of carbon moving up the food change from this plant? If, for instance, nitrogen is limiting growth, then it may be directly linking to the amount of carbon being pulled out of the atmosphere. However, if the plants are producing the secondary defensive compounds with excess carbon, there may be a non-linear response. Plants begin to get starved for nitrogen and stop their basic growth process, but continue to produce new mass in the form of secondary defensive compounds, which deter herbivores from consuming, and therefore further reduce the amount of carbon moving up the food chain.

And all this is going on in the context of multiple plant and animal species competing for the same resources as well! Needless to say, this is an incredibly complicated process that will probably continue to keep ecologists occupied for, oh, say, the next ten thousand or so years.

And this is only the tip of the iceberg!

My Research Part 1: The Law of the Minimum

Although I love talking about random wildlife and neat Kansas habitats, I am interested in updating my online explanations for my own research as well. Therefore I'm going to take us down a path towards understanding the fairly complex research that I do. So that I don't lose anyone, I'm going to try to start from some basic ecological concepts and work my way towards the more complex ones.

There are few more fundamental aspects of life than eating. Life does not spontaneously generate energy or material, and therefore all living things must pull nutrients from their surroundings in order to grow, survive and reproduce. On a personal, visceral level, every human understands this concept.

The early biologists (i.e., farmers) understood it too, and they understood that plants, as well as animals, needed to pull in nutrients to survive. Generally speaking, the first crops that would be planted on a plot of land would yield better than subsequent plantings. At least from the times of the early Egyptians, but probably long before that, the use of animal and plant waste products as fertilizers was common. There was very little understanding from those early farmers about what was actually being replaced with the additions, but whatever it was seemed to work. Adding manure or other fertilizers (dead plants, ashes, crushed seashells, etc.) prior to planting would cause greater yields.

Figuring out exactly what was happening had to wait until adequate understanding of chemistry was developed, and that happened during the lifetime of Justus von Liebig (mid 1800s). At the time, a lot of focus was given to the organic character of the soil. Much stock was put in the amount and quality of humus within the soil (Humus is degraded plant or animal matter that gives soil a dark brown or black color). Liebig, on the other hand, thought that humus was an essentially meaningless product for increasing plant yields, and argued instead that a single, inorganic component (ammonium) was far more important.


What Liebig understood is that a plant is made up of a few dozen elements. Agricultural plants needed all these elements to survive, but the repeatedly used soil was only deficient in one of them. When farmers of his day added manure or humic soil to their fields, they were adding a mix that contained all the elements, but all that mattered is that they were adding the 1 element that was missing. Liebig explained this by using a visual metaphor of a bucket constructed with staves of unequal length. Each stave represents a single nutrient that the plant needed, and the amount of water that the bucket can hold represents the plant's yield.


What Liebig explained is that the bucket would only hold as much water as the shortest stave. That is, a plant will only grow until it runs out of the nutrient that is least available. Liebig argued that for the agricultural systems in his neck of the woods (Europe) the nutrient in least supply was nitrogen, and that in order to increase yields, all one needed to do was add nitrogen (in the form of ammonia). Although there was some hiccups in the implementation of this concept, it has certainly proven to be correct. So much nitrogen fertilizer is used in the Mississippi basin, for instance, that it is causing the infamous Gulf of Mexico Hypoxic Zone.

However, what's true for plants is actually true for all living organisms. Liebig's Law states : growth is controlled not by the total of resources available, but by the scarcest resource (limiting factor). Notice the word resource and not element or nutrient here. That's because sometimes the limiting resource is not chemical. For instance, the growth of a population of hermit crabs may be limited by the availability of shells rather than any particular nutrient.

Liebig wasn't the first one to propose this idea, but he certainly made it popular. The effect on agriculture was slow but astounding. Fertilizers that targeted the missing nutrients in the soil (usually nitrogen) became extremely important to the boom in agriculture in the 1900s.

This idea of a limiting factor has really fascinated ecologists. Experiments have been on plant and animal species from aquatic and terrestrial habitats all over the world trying to get an idea of what the most likely limiting nutrients are. In general, important limiting factors for plants have included light, nitrogen, phosophorus, and the availability of pollinators, while larger animals (like humans) generally seem to be limited by food energy (the # of calories in the available food).

Limiting factors are an important component of evolutionary theory as well. This is, essentially, where evolution occurs. If a particular resource is limiting, and everyone in a population is competing for that resource, then individuals who can exploit that resource more efficiently will be more successful and more likely to pass on their genetic material.

Ok, I think that's enough for this week.

On the replacement of inaccurate and misleading scientific terms or: how I learned to stop worrying and love the ‘periphyton’.

Paul Frost is a good friend and long-time collaborator of mine at Trent University in Canada. He's spent most of his career working on ecological stoichiometry and animal physiology. Today's post is an essay Paul wrote about the use of the word periphyton in stream ecology. I've often referred to this article when arguing with people about the use of terms in ecology in general, so I asked Paul if I could publish it here. Enjoy!


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The sciences of limnology and oceanography require the use of specialized terminology. Also known as jargon, this terminology can save us the time and effort used to describe explicitly every article and action involved in doing aquatic science. Articles as diverse as seston (suspended particulate organic matter) and thermocline (a depth in lakes and oceans showing some prescribed temperature change) would be awkward to define in every instance of their use. While obviously useful, many scientific terms are a potential source of confusion. This confusion comes about when one term has several alternative meanings or when alternative and competing terms have the same meaning. In addition, a few terms while used to refer to one thing can literally mean something else. The desire to avoid terminological confusion can stimulate calls for change, which, if successful, result in the addition and deletion of words or expressions from the working lexicon of aquatic scientists. While such change might offhand appear desirable, we should all pause to consider the potential effects of eliminating well-established scientific terms that happen to be inaccurate, vague, or ill-defined. For example, the retirement of an offending misnomer could potentially create confusion for future readers of the literature due to a temporal disjunction in terms referring to the same item or action. Ironically, the desire to reduce confusion may ultimately lead to further and potentially more confusion (at least over the short-term).

Fig. 1. Yearly occurrences of terms referring to the attached organic matter in the benthos (aufwuchs, biofilm, and periphyton) found in Limnology and Oceanography between 1957 and 2002. Numbers of occurrences were counted by searching JSTOR and the ASLO website for each year. (click to enlarge)

So we are left with seemingly contradictory concerns when making decisions regarding whether to retain an established term or seek a better alternative. Isn’t it better if we find the most accurate term for an article or action and use it instead of other incorrect but more established terms? Or maybe we should keep well established terms because changing terms, in and of itself, produces confusion. Does it really matter if we go one way or the other as long as each term is accurately defined at the first use in each manuscript? In this paper, I examine an example of this uncertainty by presenting the current confusing situation regarding the terms used to characterize the particulate organic matter (POM) attached to rocks, plants, and the sediments of aquatic ecosystems. This particular example illustrates the problems of having multiple terms referring to the same item and how terminological change may not be helpful especially if the new terms are equally misleading or vague. With this problem in mind, I consider several solutions to resolving the general issue of multiple terms referring to one article and provide suggestions for the future use of benthic POM terminology.

There are a bevy of terms that refer to the particulate organic matter attached to rocks and other submerged surfaces: “aufwuchs”, “biofilm”, “benthic algae”, the epi-s (epilithon, epipssamon, epixylon, and epiphyton), and “periphyton”. These terms can be found in the limnological literature referring to the POM or distinct parts of it, are sometimes used concurrently in the same article, and have widely varying levels of scientist support (based on comments I have received in more than one review provided by more than one reviewer). Given that these terms often refer to essentially the same thing and most of them are found fairly often in the literature, there appears to be no current consensus on what to call the attached particulate organic matter in benthic ecosystems or any strong rationale with which to decide the term to use.

Each of these terms if examined closely and/or literally are somehow deficient in their ability to precisely define the attached POM. For example, periphyton, if taken literally, simply means “around the plant” and thus fails to provide any information about what it is that is around the plant. In addition, periphyton is commonly used to refer to materials attached to non-plant substrates (i.e., rocks). A different take on periphyton is that it means “plants around”, which is as uninformative as the first definition. Clearly, ‘periphyton’ fails to convey an exact meaning of the attached benthic POM. Biofilm is another commonly used term for the POM, which is also vague and somewhat inaccurate. This term literally means a living film or perhaps a film derived from living organisms. Biofilm is deficient in its lack of acknowledgment of the non-living components of the attached particulate organic matter. Benthic algae only refers to the attached algae of benthic ecosystems and fails to capture the complex nature of the attached POM. There are also the terms consisting of ‘epi-’ and a Greek-derived root. These terms simply mean ‘on the’ and your substrate of choice. For example, epilithon means ‘on the rock’. This term includes all organic types (including living and non-living material) and specify the type of substrate under investigation. Such terms avoid confusion over whether we are talking about rocks, sand, mud, or plants as substrates. A literal dissection of the ‘epi-’ terms shows the terms could be regarded as overly inclusive. For example, epilithon could mean, as it is commonly intended to, particulate organic matter attached to rocks. But it could also mean, if taken literally, a bed of zebra mussels. It doesn’t say what is actually attached to the rocks. One final alternative, sometimes seen in the literature, is the use of a combination of these terms as in ‘epilithic biofilm’. This solves some of the problems noted above except that all of the above terms (e.g., periphyton, biofilm, benthic algae, epilithon) which would be used in some combination are, one way or another, problematic and therefore ultimately fail refer to the entire complex mixture of organic matter.

There are several solutions to this terminological problem. We could simply choose the most established or well-known term and then stand united behind it. Alternatively, we could look for the most correct alternative and use it. Or we might instead look for an innovative and relatively unencumbered term. In this case, the most established term is periphyton (see below), the most correct alternative would probably be found in using a mix of the terms, and a new term might be something like ‘organofilm’.

Fig. 2. Total yearly usage of terms (periphyton, benthic algae, biofilm, and the epi’s) found in the titles and abstracts of six widely read limnological journals (Limnology and Oceanography, Freshwater Biology, Journal of the North American Benthological Society, Canadian Journal of Fisheries and Aquatic Sciences, Archiv für Hydrobiologie, and Hydrobiologia) during the years 1985-2005. Term usage was assessed using root (i.e., periphyt*) searches in the Web of Knowledge. (click to enlarge)

Barring the widespread adoption of a new term (i.e., organofilm), the already discussed terms, periphyton and its alternatives, will continue to battle for usage in the aquatic literature. It might be that one term will ultimately win out and eliminate the usage of all of the competing terms. One indication of whether that is happening is provided by examining the patterns of term usage over the relatively recent past. During the past twenty years, the annual occurrence of all terms (i.e., periphyton, benthic algae, biofilm, and the “epi’s”) in the titles and abstracts of papers published in 6 aquatic journals has steadily increased from 31 times per year in 1986 to 83 times per year in 2005 (Fig. 2). The use of periphyton, on the other hand, has remained relatively steady, being found 30 times per year both in 1987 and 2005 (Fig. 2). It thus appears that the relative use of periphyton (compared to the other terms) has decreased somewhat over the last twenty years (64% of occurrences in 1988 to 33% in 2001; Fig. 3). Despite this, periphyton was the most common term over the entire period being found a total of 539 times at an average annual rate of 26.9 times per year. This total exceeded the number of occurrences (425) of the second most common group of terms (the “epi’s”) by about 26%. Similar to periphyton, the “epi’s” and benthic algae have seen relatively steady use in the literature (Fig. 3). Biofilm, on the other hand, has increased in the total number of occurrences per year (from 0 in 1987 to 15 in 2004) and, consequently, has increased its percentage share of total references (0% in 1983 to 19% in 2002; Fig. 3).

Fig. 3. The percentage of total occurrences for terms (periphyton, benthic algae, biofilms, and the epi’s) found in the titles and abstracts of six widely read limnological journals (Limnology and Oceanography, Freshwater Biology, Journal of the North American Benthological Society, Canadian Journal of Fisheries and Aquatic Sciences, Archiv für Hydrobiologie, and Hydrobiologia) during the years 1985-2005. Term usage was assessed using root (i.e., periphyt*) searches in the Web of Knowledge. (click to enlarge)

These results indicate that the term, biofilm, has taken hold and we should perhaps expect increased usage of this term in the future at the expense of periphyton and the ‘epi-‘ terms. This increased usage of biofilm may eventually create a positive feedback mechanism, where its prevalence leads to its greater use and increased disuse of the alternative terms. I recognize that predicting future patterns of term usage is difficult given that authorial preferences, editorial advice and direction, and perceived proper usage are all likely to influence these patterns. Nonetheless, I suspect that biofilm will ultimately replace periphyton in the common parlance of the limnological vocabulary. That is unless we choose not to follow this route of replacing one ill-conceived term with another. Why not keep and promote periphyton along with a clear and distinct definition of what the term means?

I remain perplexed by some of spirited arguments against the continued use of periphyton that I have received in both oral and written form. Would I have fewer readers of my scientific paper or would it have less impact if I were to choose to use the term, ‘periphyton’? As I generally define the term, ‘periphyton’, when I first use it in a paper, how much confusion could possibly arise? Why would adopt an alternative term (i.e., biofilm) that is also misliteral and borrowed from another biological discipline (i.e., microbiology) over our own troubled term? If we were to start replacing all vague, confusing, or multidefinitional terms, we would have a considerable task ahead of us. For example, we might consider changing ‘limnology’ which means the study of lakes to a term that includes the study of rivers, streams, and other freshwater ecosystems (e.g., limnopotamology). Or perhaps we should phase out ‘oceanography’ for an alternative term (e.g., oceanothalassology) that means more than the charting of the ocean. Once started, we would find terms in need of replacement throughout our scientific vocabulary (Box 1). The problem with this is that we would generate a lot of confusion by doing so; more so than that caused by the original misliteral or multiple terms. In the end, maybe we shouldn’t overly worry about the arbitrary nature of language and learn to live (or love) the unique and interesting patterns of word usage that science and history has provided us.

References.

Frost, P.C., H. Hillebrand, and M. Kahlert. 2005. Low algal carbon content and its effect

on the C:P stoichiometry of periphyton. Freshwater Biology 50: 1800-1808.

The Society for Environmental Toxicology and Chemistry (SETAC)

Last week I attended SETAC's annual conference, which took place in Milwaukee. I gave a talk about toxistoichiometry, and attended the whole meeting.

There's a lot to talk about with SETAC, so I think I'm just going to hit the memorable stuff for now:

1. SETAC's annual conference is riddled with extremely poor talks. The 2nd talk of the Green Chemistry session was by an EPA scientist who didn't really give a talk at all. He simply recited a list of criteria for what makes a chemical 'environmentally friendly.' No justification, no explanation, nothing but a recitation of conditions. I wish this were unusual, but in fact, SETAC appears plagued by talks from people who don't really seem to care about producing a quality talk. That's extremely disappointing, especially when the titles and/or abstracts sound so promising. By comparison, the annual conference for the North American Benthological Society (NABS) typically contains a slew of extremely well-done talks.

2. The heavy metals story is overwhelming. There were multiple sessions and hundreds of posters detailing the toxicity and effects of heavy metals. This was encouraging to me, since I've been working to stop a project by an energy company to dump heavy metals into the Kansas river. The sheer volume of evidence in support of the hazards of heavy metals makes my job easier.

3. Ecotoxicologists at SETAC need to get better, and that's all there is to it. One speaker used a tennis-shoe metaphor/literary device to get her point across ( the "Just do it." approach or a "New Balance"), without ever explaining what either meant. Another speaker referred to a 24 hr toxicity test on crustaceans as 'Chronic.' A third speaker (actually the chair of my session) gave a talk that consisted entirely of him recounting an unsuccessful survey for hellbender salamanders and then showing us pictures he took while he was doing the survey.
These are unacceptable, and we should expect better from scientists giving talks at major conferences. If you don't have any results or data, don't try to amuse me by showing me your pretty underwater photographs of a bluegill. A talk at a scientific conference should include, at minimum, a complete story of some research, along with necessary background info and some kind of data.

4. The good talks: While the "Ecotoxicology" sessions were mostly awful, the "Wildlife Ecotoxicology" session was amazing. I didn't agree with all of the science (particularly one speaker's assumption-laden justification for his qualitative interpretation of his data) in almost every talk we got an introduction, a compelling methodology, and a insightful synthesis. This peaked with Nico van den Brink and Frouke Vermeulen's separate talks demonstrating the importance of taking into account foraging on heavy metal uptake from both a theoretical and experimental basis. That whole session was stellar, and has to rank as the overall highlight of the conference.

5. Tyrone Hayes. This guy gave the best scientific talk I have ever seen in my life. You can read about him online here, here, and here. He made a compelling case that Syngenta has bought out the integrity of several researchers and may be unfairly influencing the EPA. Apparently this fight has been going on for awhile, although I hadn't been fully aware of it. I do know that corporate interests certainly seem able to "buy" whatever results they want from unscrupulous researchers.

6. My talk. I thought my talk went fairly well. I had a lot of good questions, mostly on a more general front, but also a few that made me think. When people see this research, they start thinking up lots of intuitive ideas about how to go forward, and for some reason, a lot of these ideas are pretty obvious. I had multiple questions that paralleled my own thoughts, and the thoughts others have offered. One of my hopes during this conference was to interact with some profs who might be interested in doing some toxi-stoich research in their own labs. I don't know if that is going to happen.

There was a lot more that happened, and I'll try to recount some of it here, along with my thoughts on how to improve scientific conferences.

Toxistoichiometry: Integrating Ecological Stoichiometry and Ecotoxicology

In my current job I haven’t been doing a lot of original research, but that hardly means I am abandoning my wide range of research interests. I wanted to explain today a little bit about the “big idea” that I’ve been chipping away at for years. What follows are pieces from a talk I’m going to give to the Society of Environmental Toxicology and Chemistry in Milwaukee on November 12^th.

Evaluation of toxicity is most often done by the use of standard bioassays on commonly used test organisms. For example, you can pull up an EPA-approved method for determining the acute or chronic toxicity of any chemical to Daphnia spp. Theoretically, anyone in the world can follow the same protocol and get the same result. In reality, considerable differences occur between labs and even between Daphnia strains (not to mention different species), but this overall approach has been accepted for years as a means of estimating toxicity. The problem is that this method only estimates relative toxicity within a specific context. Relating the results of these short-term, laboratory tests to real-world scenarios is not only difficult, it may be impossible. For example, frequently used protocols often provide organisms with an abundance of high-quality resources, while in nature organisms are often faced with either low quantity or low-quality resources. A number of studies have tried to understand how the effect of a toxin varies with food quantity, but few have adequately addressed how food quality alters the effect of a toxin. Imbalances between the nutritional quality of a food source and an organism’s dietary needs are common in nature and appear to play a role in individual physiology, population dynamics, community interactions, and ecosystem processes. The study of how nutrient imbalances alter ecological relationships is often referred to as ecological stoichiometry. Organisms respond to changes in the stoichiometric ratio of elements in their food with corresponding variations in growth, reproduction, assimilation, and excretion. Essentially, nutritional imbalances have a large effect on ecosystem function.

My interest is in linking ecological stoichiometry with ecotoxicology. Initially, I have focused on how food quality affects acute toxicity in aquatic organisms. My collaborators at the University of Notre Dame and Trent University and I have shown that some toxins (iodine, cobalt, fluoxetine in particular) are stoichiometrically explicit, meaning the effects on organisms vary based on the quality of food the organism is getting. Other toxins do not appear to be stoichiometrically explicit (bendiocarb, triclosan, methanol) although it is obviously harder to prove.

The implications of stoichiometrically explicit toxins are presently unknown, but one can imagine a situation where the concentration of a toxin allowed by law is harmless when organisms are fed high-quality food, but detrimental when they are given poor quality food. Obviously, in nature species are often faced with food shortages or poor food quality, thus the actual effect of toxins may be much greater than the estimated effects. Evaluating the risk a chemical poses to an ecosystem therefore requires a more context specific approach. Are the receiving ecosystems frequently nutrient stressed? Are times of pollutant release going to coincide with occasions when ecosystems are nutrient stressed? I’m not sure whether regulatory agencies are equipped to permit in this way.

This kind of work is obviously just a first crack at the idea, and in many ways a very basic approach. Without this kind of base data, however, addressing more interesting questions becomes difficult. I believe that toxistoichiometry has the potential to provide a new axis of understanding for ecotoxicology.