00000nam 2200000zi 4500 9.878319 CaOODSP 20241203113651 m o d f cr ||||||||||| 190821s1993 oncbd #ob f000 0 eng d CaOODSP eng rda CaOODSP n-cn-on En13-5/93-04E-PDF Reynoldson, Trefor B., author. Historic changes in populations of burrowing mayflies (Hexagenia limbata) from Lake Erie based on sediment tusk profiles / Trefor B. Reynoldson and A.L. Hamilton. Burlington, Ontario : National Water Research Institute ; Ottawa, Ontario : International Joint Commission, [1993] 1 online resource (21 pages, 4 unnumbered pages) : maps, graphs. text txt rdacontent computer c rdamedia online resource cr rdacarrier [NWRI contribution] ; [93-04] Digitized edition from print [produced by Environment and Climate Change Canada]. Includes bibliographical references (pages 16-19). "One of the most dramatic recorded changes in benthic invertebrate community structure due to eutrophication was the elimination of the burrowinq mayfly, Hexagenia limbata, from the western basin of Lake Erie. This was a catastrophic event occurring as a result of two periods of anoxia in the summers of 1953 and 1955. From the examination of sediment cores the changes in historic populations of Hexagenia have been reconstructed from enumeration of mandibular tusks. The changes in the numbers of tusks found in the sediment cores from the western basin of Lake Erie agree well with known historic events but suggest that numbers found in the earliest field samples represent a considerable increase over historic populations. Cores taken from the central basin suggest that Hexagenia was formerly only found in a band around the shore and populations never occurred in the offshore waters. It is suggested that this is strong evidence for the occurrence of brief periods of anoxia in the central basin of Lake Erie prior to cultural eutrophication"--Abstract, page 3. gccst Sediments gccst Lakes gccst Historical research Hamilton, Andrew L. (Andrew Lloyd) author. Canada. Environment Canada. International Joint Commission. National Water Research Institute (Canada) NWRI contribution ; 93-04. (CaOODSP)9.844121 PDF 2.00 MB https://publications.gc.ca/collections/collection_2019/eccc/en13-5/En13-5-93-04-eng.pdf