Report on the development of the national assessment method for the ecological status of natural lakes in Greece, using the Biological Quality Element “Macrophytes” (Hellenic Lake Macrophytes-HeLM assessment method)

Abstract

This report discusses the development of the national ecological assessment method for Greek natural lakes, based on the Biological Quality Element (BQE) “macrophytes”. Due to lack of a common natural lake type within the Mediterranean Lake Geographical intercalibration Group, there has not been a Med GIG Intercalibration Exercise for macrophytes in natural lakes. As a result, there are neither proposed assessment methods with common boundaries within the Med GIG, nor proposed metrics for the assessment of lakes based on macrophytes. It is noted that at the Mediterranean Lake Phytoplankton GIG Intercalibration Report, Member States defined two common water body types (L-M5/7 and L-M8) for reservoirs but none for natural lakes. The operation of the Greek water monitoring network started in 2012, following the publication of a Joint Ministerial Decision in 2011. The development of the current assessment method, as described in this report, is based on the data from this national water monitoring network. In particular, 50 lake water bodies (including 26 reservoirs) have been included in the monitoring network, out of which 16 have been monitored for macrophytes during the 3-year period of 2013-2015. Eight of them are warm monomictic, deep natural lakes with mean depth >9m (GR-DNL), when the other eight are polymictic, shallow natural lakes with mean depth 3-9m (GR-SNL). In these 16 lakes, a total of 272 monitoring sites were established for sampling macrophytes, which resulted in an equal number of macrophytic sampling transects, the data of which have been added in the national dataset. Thirty six of these sites were revisited during the 3-year period, and a total of 308 measurements of maximum macrophytic colonization depth were made. On this national dataset, the most suitable lake macrophyte based assessment components proposed by WISER deliverables D3.2-1 (Kolada et al., 2009), D3.2-2 (Dudley et al., 2011) and D3.2-3 (Kolada et al., 2011) were tested, in various combinations, so as to reach a final form that can be used as a national assessment method for Greece. As already mentioned, this is the first effort to establish a national method, which may need additions and improvements in the future, as well as intercalibration exercises among Member States in the Mediterranean GIG.