Notice: The following data are unpublished in regular journals. If any information is used from this page or these pdf's, please credit Rie Miyazaki in particular and also this website as the source and owners of the data. Thank you.-
The map at left and the table below illustrate the condition of insect communities in the South Saskatchewan River. The river flows from the west to the northeast.
Going from B to G, that is, from the Alberta border past Saskatoon to the confluence of the North and South Rivers, total insects in a standard set of samples goes from 1280 at B, to zero at D; totals then rise to 1840 at E, and drop to 133 at F-G. Numbers then rise to 767 near G.
Species composition and dominance are altered. At E, Outlook Bridge, imost nsects in the samples are Chironomidae, in contrast to other sites. The highest numbers of species are at B and G. Between B and G number of species is lower, including reduction to zero at D. The obvious explanations for negative conditions between B and G are Gardiner Dam and Saskatoon domestic and light industrial effluents. Details of species samples are given in the PDF's below.
Location B, Lemsford Ferry, low levels of pollution.
Lemsford Ferry, near the Saskatchewan/Alberta border, has little in the way of visible sources of pollution or alteration of the environment- -no city sewage, no pulp mills, etc. However, in recent years I have noticed signs of nutrient enrichment- unusual amounts of bluegreen and other algae, plus new macrophytes compared to past years (I have been collecting at this site since 1970). Lemsford Ferry has probably the most interesting community in the system in my experience- being a good site to collect most of the species on the Rare and Endangered Accounts page. The pdf below shows result from July 2006 samples.
At Outlook Bridge, the total mayflies in the samples was 203, and 174 were Baetis tricaudatus. Thus, diversity and community complexity were very low compared to Lemsford Ferry. Traverella, Lachlania, Isonychia, and other genera were absent at Outlook Bridge, but present at Lemsford Ferry.
At Outlook Bridge, total insects numbered 1466, and of these 1192 were Chironomidae. At Lemsford Ferry, total insects numberred 1248, and of these, 214 were Chironomidae. In general, Chironimidae are indicators of pollution or abnormal conditions. Baetis tricaudatus, above paragraph, is widespread and a tolerant species, and appears to tolerate conditions at Outlook Bridge, but many other species present at Lemsford Ferry are not present.)
About half way between F. and G. is St. Louis Bridge. This area is in the path of the altered thermal regine from Gardiner Dam as well as more or less unknown industrial and municipal impacts from Saskatoon small industry and waste discharges.
The diversity, number of species, and balance among taxonomic groups at G. is perhaps more similar to Lemsford Ferry, B, than the sites between, which have zero insects in one case, dominance of Baetis tricaudatus and Chironomidae in another case, and a reduced fauna in the third case. See table at the top of this page.