Environmental Physico-chemical Sampling Strategy
Considerations: Data on the physical and chemical environment at each sampling site will be collected for two main reasons: (1) to support the biotic collections by providing some quantitative measures of habitat (primarily water quality); and (2) to characterize selected hydrologic systems in their own right and as preliminary data for more intensive studies in the future.
Samples for supporting biotic collections:
Environmental samples may support the biotic collections in several ways:
- For presence/absence taxon data, the ranges of selected chemical variables can be identified, giving an estimated environmental tolerance by that taxon for each variable, thereby describing some sort of niche space
- For taxa with relative (or absolute) abundance data, modal or optimal values of these variables can be determined. In particular, we'll do this for the diatom data to create a "training set" to relate relative diatom abundance to selected variable, likely total salinity, Cl, and TP, among others.
- I will be trying, by the way, to do enough approximate field analyses (simple Hach-kit stuff) to keep up with what kinds of lakes we really are sampling (Ca-Mg-CO3? Na-CO3? Na-SO4? Na-Cl?) It will hopefully point out if we have gaps in our targeted range of lake types, and perhaps guide site selection along the way.
You will have your own system for organizing your biotic collections, with some sort of identifiers for site location, sub-site location, habitat description, date, etc. To link up with the environmental data base (EDB for short, for now), you will need to attach two or three additional identifiers, which I'll have to generate for you in the field:
- SITE -- Unique code for a "site" or "stop." A site is defined here as any sampling location where the water is potentially from a different source. For example, an inlet stream or spring will be considered a different site from an adjacent lake, no matter how close these features are to each other, because the source water reaching the stream or spring is not completely the same at the lake. SUBSITES are those locations in a site (typically a lake here) where the water source may be essentially the same, but water chemistries may differ because of lack of mixing. Examples would be epilimnion, hypolimnion, and littoral samples. Shoreline pools are a difficult category -- some may be essentially lake water from wave overwash, while others may be more influenced by spring discharge and more of a modified groundwater signal.
- QWID -- Unique code for the water sample that most closely represents your sampling point (e.g., for lakes, we'll take a sample from the epilimnion, hypolimnion, and a "representative" near-shore area -- but not at every place a bug was picked up...).
- SEDID -- Unique code for the sediment sample (if any) that is related to your sample; again, we'll be taking a few "representative" samples from each lake
Samples for characterizing hydrologic systems or features:
I will be concerned, at least at some selected sites, with collecting a few more hydrologic samples that may have no direct relation to a specific biotic collection. Some of these mini-projects will include:
- To determine the trophic status of each lake with traditional measures of TP, secchi disk transparency, and chlorophyll a
- To collect data potentially useful for hydrologic and geochemical analysis. To this end, I will want, e.g., to sample some groundwater on the upgradient side of selected lakes, to measure some groundwater head gradients, and to sample some inlet streams and measure their flow. I may also collect some sediment samples for mineralogic analysis. Analysis of the water samples would emphasize major ions for mineral equilibria analysis; Ca analysis for (later, potentially) groundwater influx study; conservative ions for tracer and evaporative concentration information; and stable isotopes for further characterizing evaporative regime.