This is a long-term monitoring study of freshwater zooplankton and phytoplankton population changes after introduction of the mysid, Mysis relicta Lovén, 1862 in lake Jonsvatnet. It is an oligotrophic lake located in central Norway (63° 22’ N, 10° 37* E), 150 m above sea level. The lake has three basins divided by narrow sounds with depths of 1 – 3 m. The major basin is Store Jonsvatnet with surface area of 12,4 km2 and the two smaller ones are Lille Jonsvatnet and Kilvatnet with surface areas of 1,6 km2 and 0,8 km2 respectively. The maximum depths of the three basins are 97 m, 37 m and 34 m respectively and the average depth of the lake is 37 m. Method: Plankton are sampled at one station in each lake basin. All samples are taken during the period June-October, twice a month in June - August, once a month in September and one sampling of mysids in late October. Zooplankton is sampled with a 1 m long tube sampler (volume 5 l). A vertical column of water extending from 0 to 20 m depth is consistently sampled every 1 m. Samples from 5 m layers are mixed together and treated as one sample. Phytoplankton is sampled with a water sampler (volume 1.6 l). A vertical column of water extending from 0 to 10 m depth is consistently sampled every 1 m. Samples from 5 m layers are mixed together and treated as one sample. Mysis relicta is sampled in Lille Jonsvatnet with vertical net hauls (net opening 1 m2, mesh size 500 µm) from 1 m above bottom to to the surface.

Lake Candia is a small and shallow lake, located in North-Westerm Italy. The mean elevation is 226 m a.s.l., the surface is 1,5 km², the max depth 7,7 m, the mean depth 4,7 m and the volume 0,007 km3. Lake Candia has suffered during its evolution a natural increase of its trophic state, undergoing a process of eutrophication culminated with a marked worsening of his ecological quality since the '60s. In the late '70s and mid '80s, this ecosystem was affected by fish mortality episodes and by the enormous development of emerged and submerged aquatic macrophytes. The systematic scientific study of Lake Candia began in 1985, when the CNR of Verbania was asked to perform a limnological research with the aim to propose a possible restoration intervention. In addition to the control of pollution sources from the basin, environmentally sound technologies were applied to reduce the effects of eutrophication, such as biomanipulation of the aquatic food chain and macrophyte control and management.The experiment conducted in Lake Candia has shown that significant improvements can be achieved through the management of a specific key components of the biocenosis of the lake. Data collection activities on hydrochemistry, phytoplankton, zooplankton, fish fauna, macrophytes, as well as physical limnology, took place from 1986 until 2012. To date, only hydrometeorological data collection (precipitation, air temperature, wind, solar radiation and lake levels), started in 1987, is active. LTER specific topics are: Long-term analysis of changes in community functional diversity of phyto-and zooplankton. Evaluation of the lake ecosystem response to short and intense rainfall events, in relation to the increase of nutrients input through runoff.

The Neusiedler See - Seewinkel National Park is the first cross-border National Park in Austria and the first Austrian National Park recognised by the IUCN. It covers in total about 90km² on Austrian territory. About 50% of the area (about 4500 ha) is a Nature Reserve Zone, which remains untouched by humans. This zone is dominated by the southernmost Austrian part of the reed belt from Lake Neusiedl. The Conservation Zones are mainly cultural landscapes and require landscape conservation measures and habitat management like pasturing, mowing, cutting reed or water retention. These measures are taken to preserve the cultural landscape and its biodiversity that has developed over centuries. Important habitats like 160 km² of reed belt and around 40 periodically dry soda lakes, as well as sand habitats, dry and wet meadows can be found closely associated with vineyards, cropland, touristic infrastructure and rural settlements. Long-term monitoring programs regarding bird populations, fish ecology or the grazing management enable the cross-border National Park Neusiedler See - Seewinkel to provide biological data from flora and fauna. Furthermore, all soda lakes are monitored frequently regarding salinity, oxygen, temperature, color etc. and biological parameters such as species diversity and quantity of macrozoobenthos. Due to the mosaique of protected and non-protected areas, the boundaries of the National Park area are difficult to define on the shown map.

Lake Stechlin is a a deep clear-water lake located in a nature reserve approximately 80 km north of Berlin, Germany (53°10°N, 13°02° E), at 59 m elevation.The lake basin was formed during the last continental glaciation some 12,000 years ago and today is situated at the transition between temperate/maritime and temperate-continental climates.The drainage basin is almost completely covered by forest (95%), with the exception of the area of a former nuclear power plant and a small village, which diverts its wastewater into a different drainage basin. The shoreline of Lake Stechlin is largely undeveloped with no notable infrastructure. The seepage lake is essentially fed by precipitation and groundwater, resulting in a theoretical water retention time of greater than 40 years.

The Elbe River is one of the major rivers in Central Europe. It springs at an altitude of about 1,400 meters in the Giant Mountains in the north of the Czech Republic. It flows through eastern, middle, and northern Bohemia, and its catchment area includes most of Bohemia. The Elbe traverses the northeastern part of Germany and flows into the North Sea. The total river length is 1,094 km. In the Czech Republic, the monitored river length is 371 km and the catchment area includes 49,933 km2. The average flow at the Czech-German borders is 311 m3 s-1. Many weirs dam the watercourse of Elbe River in the Czech Republic. This artificial intervention is crucial for the characteristics of the riverbed, its width, depth, and bottom substrate. The width of the riverbed in the monitored area ranges from approx. 10 m on the upper course to approx. 150 m on the lower course and river sections above the weirs. The depth of the river varies from 0.5 m in the upper parts and below the weirs to more than 5 m in the lower course and above the weirs. The bottom substrate varies from the stony, gravelly, and sandy fractions in shallow and fast-running sections to muddy/silty fractions in slow-running sections above the weirs. The main tributaries of the Elbe in Bohemia are Metuje, Orlice, Jizera, Ploučnice, Vltava, Ohře and Bílina rivers. The catchment area is densely populated. The river is exposed to various sources of pollution (organic, agricultural, and industrial) and hydromorphological pressures (straightening, shortening, regulation of meanders, and fragmentation of river continuity). There are seven permanent monitoring sites on the Elbe River in the Czech Republic: Děčín (river kilometer 747.9), Litoměřice (796.9), Obříství (842.1), Lysá nad Labem (878.8), Valy (954.7), Hradec Králové (994.4) and Vestřev (1051). The Elbe basin long term environmental research has been organised by the Ministry of Environment of the Czech Republic and cooperation institutions since 1993. More than 600 physicochemical parameters, including sensory properties of water, are regularly monitored in at least nine different types of matrices (water, sediment, periphyton, floats, sedimentable floats, benthos, fish tissues, fish fry, and Dreissena polymorpha tissue) and using passive samplers. Among the main monitored characteristics belong balances of macroelements (carbon, nitrogen, oxygen, phosphorus), concentrations of inorganic salts, heavy metals and various organic pollutants such as pesticides, personal care products (including drugs) and other anthropogenic substances in the environment. Characteristics such as abundance and species composition are regularly monitored in fish, macrophytes, macrozoobenthos, phytobenthos and plankton.

UK ECN site. Windermere is in NW England in the English Lake District, an area of great natural beauty and a tourist destination since the 18th century. The dominant geological structure of the Lake District is a dome of Paleozoic rocks formed by uplift in the Tertiary producing a radial drainage pattern later enhanced during the Pleistocene glaciation, with major lakes occupying bedrock basins in steep-sided, flat-floored valleys. Windermere is the largest natural lake in England with a surface area of 14.8km2 and altitude of only 40m. The lake is divided by a shallow sill into two basins; North Basin (NB) (surface area c. 8km2, maximum depth 64m) and South Basin (SB) (surface area c. 6.7km2, maximum depth 42m). Windermere (ECN site (2o58'W 54o23'N)), has a catchment of 180km2 draining into the lake via two main rivers, several small tarns (lakes) and streams. The catchment is mainly uplands, grazed by sheep all year but also used intensively for recreational purposes. The valley villages are major tourist destinations with consequent increases in sewage input to the lake. Over the past 50 years levels of dissolved reactive phosphorus in the lake have more than doubled, reaching their highest levels in the 1980s. The effluent discharged into SB from the main sewage works is now P-stripped to reduce the nutrient loading to the lake. The lake is a Site of Special Scientific Interest (SSSI), a source of potable water, a major recreational facility and a specialised fishery (for charr, Salvelinus alpinus). The Freshwater Biological Association and latterly the Centre for Ecology & Hydrology have had a laboratory on the shore of Windermere for over 50 years resulting in a large body of scientific literature based on Lake District lakes.

The Gulf of Venice is a gulf that borders modern-day Italy, Slovenia and Croatia, and is at the north of the Adriatic Sea between the delta of the Po river in northern Italy and the Istria peninsula in Croatia. The site is under a heavy antropic impact (nutrient loads, coastal towns, fishery, tourism maritime routes). In the past eutrophic events struck the ecosystem and, more recently, frequent mucus macro-aggregates extended in the whole basin. Study of long term historical time series of the biotic community in the Gulf of Venice in relation with the biogeochemical cycles and physical properties of sea-water have been conducted since the '70s.

UK ECN Site. Esthwaite Water is a natural lake situated in a glacial valley and is generally agreed to be the most productive or eutrophic lake in the English Lake District. It lies approximately 65 m above sea level and has an area of 1 km2 and a maximum depth of 15.5 m. The average retention time is 90 days. The catchment area is 17.1 km 2 and the hills are composed geologically of Bannisdale slates and grits. The surrounding land is used chiefly for agricultural purposes and forestry. The lake is a grade 1 Site of Special Scientific Interest and has been a designated "Ramsar" site since November 1991. The diverse aquatic invertebrate fauna includes a number of species with restricted distributions in Britain, one of which is the flatworm, Bdellocephala punctata. The slender naiad, Najas flexilis, which is listed as Nationally Scarce, has been found in Esthwaite Tarn. Artificial enrichment of the lake occurs by input from the Hawkshead Sewage Treatment Works (which has operated a continuous programme of phosphate stripping since 1989) and originally from effluents from the fish farm which used to be situated towards the south of the lake. The lake undergoes summer stratification with oxygen depletion regularly below 7 m and sometimes as shallow as 5 m. The phytoplankton tends to be dominated by diatoms in spring and by cyanobacteria for much of the summer.

South-West Bulgaria, Mediterranean catchment

Western part of the Gulf of Riga (the Baltic Sea) littoral and sublitoral zone. The marine site is located on the west coast of the Gulf, in the Engure Nature protected area. The monitoring activities are based on three transects which represent an open area of very similar substrate type. These transects are located on the tip of Mersrags, 2.5 km northwards from the port of Mersrags. Long-term studies of the Gulf of Riga coastal zone communities and macrophytes as the key component of littoral zone under natural and anthropogenic impact and possible threats to the littoral zone biological resources. The SCUBA diving is used in marine site assessment.