My research partner and I plan to conduct a research using tardigrades as bioindicators for air pollution. Air pollution is a broad description that may include many common atmospheric pollutants (ex. particulate matter, ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, etc.) and as of now our research is only limited to determining the effect of air pollution to diversity of the tardigrade species. We are not yet able to determine the possible direct effects of these pollutants on, for instance, the tardigrade's body processes, knowing that these water bears can undergo cryptobiosis to withstand unfavorable environmental conditions. Thus to gather more possible information, we would like to know which, if any, of these common pollutants could have the most effect on tardigrades.
Tardigrades are really tough, in fact Earth should be called the planet of Tardigrades no? That's a good question. If they're survived on Earth for millions of years, endured the coldest, hottest, most radioactive conditions (they survive in space too), then I would imagine that a naturally occurring gas/air pollutant wouldn't affect them right? Something like H2S, CO, CO2, SOx, NOx, etc. have been around long before us humans, being produced by volcanic activities for example. If the Tardigrades survived those conditions then I imagine they've evolved and adapted to those types of gases. I'm being speculative here, not certain. However, more modern air pollutants invented by us, such as Persistent Organic Pollutants (POP's), PCB's, CFC's, HFCF's, etc. Pollutants that are known to be persistent in the food chain, bio-accumulate and bio-magnify in ecosystems, could these affect Tardigrades? Could these devastating pollutants from our industrial processes be the only contaminants that the Tardigrades haven't ever faced or adapted to?
Hi
For some review see here: https://content.sciendo.com/view/journals/eje/4/2/article-p124.xml?language=en
How about ethanol?
One idea that I had toyed with, but never pursued, was to investigate the impact of ethanol. While not a particularly common air pollutant, except in and around whiskey (and other spirits) distilleries and maturation warehouses, atmospheric ethanol is seen to lead to increased growth of the fungus Baudoinia compniacensis (whiskey fungus) and the subsequent black discolouration of buildings, tree trunks and other surfaces. This discolouration would appear to diminish with distance from the distillery / maturation warehouse and thus perhaps can be related to the ambient concentration of ethanol (?). By using a simple ‘grey scale’ (from white to black in 10% gradations) or use of a reflectometer, I'd thought it may be possible to produce a contour plot of Baudoinia growth density and thereby an ethanol impact footprint with distance from a distillery/warehouse. Once the Baudonia footprint was known, scrape samples of Baudonia and/or lichens and mosses could be taken and analysed for tardigrades. The idea being that the abundance and/or number of tardigrade species encountered could be related to the degree of Baudonia growth/discolouration of surfaces and thereby ethanol concentration. Samples of bark & lichen could also be taken for pH measurement, and ambient ethanol concentrations measured by passive samplers and/or diffusion tubes. Or at least that was the idea.
Interestingly, when I first started looking at tardigrades I tried to relax them with alcohol - big mistake, as they immediately curled into a tight ball from which they didn’t uncurl thereby making I.D impossible. It may therefore be the case, given the impact of alcohol on tardigrades, that those epiphytes on trees, buildings, fenceposts etc. nearest to the distilleries/maturation warehouses may actually be devoid of tardigrades (of course this depends on the concentration of ambient ethanol and tardigrade tolerance to low concentrations of it (but that's another area for investigation).
Tree dwelling lichens are widely used as air pollution indicators due to the various air pollution tolerance between different species that occur as epiphytes. In general orange colored lichens are more tolerant to air pollution (nitrogen and sulfur ) and species which contain cyanobacteria as the photo partner are more sensitive to air pollution. We recently published research that shows that tardigrade communities also vary depending on the functional group of the epiphytes (hair lichens vs. foliose lichens vs. bryophytes) and height within the canopy (Young et al 2018). Any attempt to use lichen and bryophyte dwelling tardigrades to indicate air pollution will be stronger if these confounding non-pollution related variables are accounted for. Also I would suggest using epiphytes as the model system as rock or soil dwelling species are not as sensitive of air pollution indicators due to the buffering effect provided by the rock or soil substrate.
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