County Wildife Site Criteria for Cornwall Appendices

OLIGOTROPHIC AND DYSTROPHIC LAKES: SourcesDataset Description Owner Role in Inventory Access NotesA Study of theTrophic Status ofStandingFreshwater inCornwallA report which givesan assessment of thetrophic state offreshwater inCornwall (McCartney2006)EN Gives details of theTrophic Ranking Score(TRS) of every tetradin the countyERCCIS Good quality TrophicRanking Score (TRS)information whichcorresponds to thetrophic state offreshwater n theAn estimate ofthe extent ofdystrophic,oligotrophic,mesotrophic andeutrophic standingfreeshwater inGresat BritainA report which givesan assessment of thetrophic state offreshwater in Britain(Palmer & Roy 2001)JNCCContains details ofmethodologyOLIGOTROPHIC AND DYSTROPHIC LAKES: CommentsJNCCwebsitecounty.The trophic statusdata is not relevant ata local levelData SourcesA Study of the Trophic Statusof Standing Freshwater inCornwallThe DefinitionFairReliability of PHTInterpretationFairOverall AssessmentGoodCommentThis source is the only reference available.CommentThere are considerable problems. The definition does notclearly specify how the trophic status should be decided. Wehave followed one suggestion and used the plant communities,but these results refer to a tetrad and not to individual waterbodies. Further fieldwork would be needed to clarify thetrophic status of these waters.ExplanationIn general, the use of the TRS approach is a good one. It is clearand unambiguous, follows some of the guidance within thedefinition and corresponds to the trophic status. It isparticularly good at picking out the dystrophic and oligotrophicwaters in Cornwall and is assumed to select the majority ofthose that are eutrophic, but there is a considerable overlap ofoligotrophic, mesotrophic and eutrophic around TRS values of7.0-7.9 (TRS runs from 3.0-10.0).CommentsMaps of the trophic state of waters in Cornwall exist at tetradlevel and estimates of the areas of waters of varying trophicstatus have been made. It is likely that the distribution ofmesotrophic lakes in Cornwall is rather poorly known and thatthe estimate for the total area is likely to be either imprecise orbiased or both.Appendix 4 - Information Relating to Priority Habitat TypesCounty Wildlife Sites Criteria