Implementation of Trophic Status Index in Brackish Water Quality Assessment of Baltic Coastal Waters The assessment of the trophic state of marine coastal waters is one of the leading initiatives declared in the European Water Framework Directive (WFD). The Baltic Sea is a semi-enclosed ecosystem which consists of subregions with wide salinity and seasonality gradients. Anthropogenic impact results in eutrophication processes on different scales. Efficient eutrophication control and environmental management in the Baltic Sea, according to WFD, requires a prerequisite of common and sensitive indicators for the European coastal waters including the Baltic Sea. In this article the Trophic Status Index TRIX, recently succcesfully implemented in Mediterranean and Northern European sea coastal waters as a holistic approach indicator, was implemented for the Gulf of Rīga and Latvian Baltic Sea coastal water quality assessment between 1999 and 2005.

The “Augšdaugava” protected landscape area was established already in 1990, but the elaboration of the environment protection plan for this largest landscape area in Latvia is still in progress. The nature park “Daugavas loki” as part of this landscape area was established in 1990 and the nature park already has the protection and management plan (2010–2022). The upper Daugava river valley forms the central axis of the protected landscape area and is included in the Natura 2000 network. The complex of the Daugava River with nine large meanders and small, natural unaltered rivers, crossing the ravines, belongs to the Annex I habitat type 3260. This area is also rich in mineral springs and spring fens. There are about 30 lakes with different eutrophication impacts in the area. The possible threats, nature values, and water ecosystem services are discussed.

The ideal or long-term goal of the management plan is to preserve the natural and cultural-historical values of the “Augšdaugava”. It means to preserve the unchanged section of the Daugava River and the adjacent territory, its landscape structure, habitat and species diversity, in the same time promoting sustainable values and socio-economic interests. This complicated goal is demonstrated in the new functional zonation and management proposals.

Protozooplankton are dominant grazers of phytoplankton and an important component of the microbial food web, as a link between pico and nanoplankton to higher trophic levels. Their fast growing rate, relative abundance, biomass and diversity are used as indicators of organic and toxic pollution. The impact of urbanisation on ecosystems and their sustainability and biodiversity have recently been much studied. We studied the protozooplankton ciliate communities during the vegetation period from April to October in two small lakes (Bābelītis, Gaiļezers) and two reservoirs (Bolderāja, Saurieši). The largest peak of biomass (15.7 × 102 mg/l) was found in Gaiļezers Lake in August and of abundance (60.2 × 103 org/l) in Bābelītis Lake in July. The lowest biomass (0.006 mg/l) and abundance (0.12 × 103 org/l) were found in the Saurieši Reservoir station. The most abundant ciliates were from the order Oligotrichida.

Latvian Environment Agency carry out complex monitoring of Kemeri National Park since 1995. At now 6 lakes are included in this monitoring programme: - 3 bog lakes - Akacis Melnezers and Lake Slokas, Lake Aklais; - shallow and overgrown lagoone lake Kanieris; - hypertrophic Lake Valgums with heavy anthropogenic impact. Lake management plan contains: - the description of the current state o f each lake; - the optimal or required lake for each lake (objectives of management); - factors which influence the lake, especially anthropogenic; action plan to achieve the objectives.