01566nas a2200169   4500008004100000245013100041210006900172260001200241300001400253490000700267520094200274100001501216700001601231700001601247700001701263856011601280       2003                        eng d00aRelationship between Water Chemistry and the Distribution of the Endangered Aquatic Quillwort Isoetes sinensis Palmer in China0 aRelationship between Water Chemistry and the Distribution of the  c2003///  a361 - 3670 v183 aThe progressive decline in populations of Isoetes sinensis Palmer in China has been attributed to deteriorating water quality; however, no data have been adduced to support this assumption. In this study we identified locations in China that presently have populations of I. sinensis and locations where the species has been extirpated. We measured various water chemistry parameters at these sites, as well as at similar sites within the distribution range of I. sinensis but from where the species has never been recorded. The results indicate that distribution and occurrence of I. sinensis are closely correlated with water chemistry. Water samples drawn from habitats from where I. sinensis has been extirpated had higher concentrations of heavy metal ions, particularly chromium VI (Cr 6+). In addition, these samples consistently yielded higher readings for dissolved carbon dioxide, water hardness, and concentration of nitrates.1 aWen, M.-Z.1 aPang, X.-A.1 aWang, Q.-F.1 aTaylor, W.C.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0242275988&partnerID=40&md5=c81ad2c1833c6a70e17163c958e43e50