Based on historical and WFD-compliant data, the recent inter-annual ecological status and the long-term chemical-physicochemical quality trends of eighteen characteristic Greek rivers have been assessed and interpreted in view of implementing EU environmental policies and the evolution of human pressures. Considering predominating poor ecological status in most of the river outflows, the strengths and weaknesses of the WFD implementation have been highlighted. The long-term decrease of ammonium and nitrite concentrations along with relatively low recent BOD₅ levels, indicate a general improvement of WWTP infrastructure in Greece and the other riparian countries, whereas the improvement of nitrate quality is attributed to the reduction of fertilizers use, and possibly, to the successful application of the Nitrates Directive in certain basins. Despite capacity building in governance and administrative infrastructure the recent years, River Basin Management Plans (RBMPs) are being implemented centrally, largely mechanistically, with minor public participation. Regarding WFD implementation weaknesses and gaps, concrete proposals have been formulated considering both policy/administrative and technical issues. To efficiently conserve and restore aquatic ecosystems, the forthcoming RBMPs should be consistent with ecosystem services principles focusing on nature-based solutions, along with changing attitudes of the state authorities and the public.

Biotic and abiotic data on undisturbed or moderately disturbed lotic sites from a number of studies carried out in northern Greece showed that large rivers differ from small rivers, streams or creeks in terms of diversity, dominant groups and the kind of taxa (concerning the sensitivity of the taxa according to Biological Monitoring Working Party (BMWP) biotic scores). This is mainly due to the differences in their physical characteristics. Correlation of the environmental variables using MDA (multiple discriminant analysis) showed that the chief differentiating factors among the above water bodies are substrate, total suspended solids (TSS), conductivity, slope and temperature. Additionally, there is no clear phenological seasonality in the majority of the dominant benthic macroinvertebrate groups when undisturbed or moderately disturbed sites of mountainous creeks and small rivers are examined. By contrast, in downstream sites of long rivers, seasonality characterizes the dominant benthic macroinvertebrate groups, as it does for other Mediterranean animals.

The life cycle of Xerolenta obvia (Menke, 1828) was studied in two areas, Paleokastro (Chalkidiki), an inland mountainous area, and Nea Karvali (Kavala), a coastal area in northern Greece. At Paleokastro snails hatch in autumn, become adult the following July, but do not lay eggs until October, after which they die. Clutch sizes are small, but eggs and hatchlings are large compared with those at Nea Karvali. Growth is fast in spring, and continues until the end of July. The young hatchlings have dark shell-bands, but by July a quarter of snails appear unbanded. At Nea Karvali, eggs are also laid in October, and young snails emerge from hibernation in March. Here, however, they do not mature until April of the following year. They thus have a 2-year life cycle, with adults dying in their second autumn. Clutches are about three times the size of those at Paleokastro, but eggs and hatchlings are significantly smaller. A little growth occurs in winter, but the rate of growth is generally much slower than at Paleokastro. Only 1–2% of this population has banded shells; the bands are less obvious and they become invisible in some individuals as they mature. At both sites population density fluctuated during the two study years, but it was always higher at Nea Karvali. These results are discussed in relation to the differing climates of the sites, and comparisons made with studies on related species in the region.