Suchergebnisse

Abstract
In the brackish ecosystem of the Gulf of Riga, the calanoid copepod Eurytemora affinis is a key species, but recently a new non-indigenous species Eurytemora carolleeae was discovered in the region. In the present study, we aimed to validate the presence of E. carolleeae in the southern part of the Gulf of Riga five years after its first discovery. The study area is the closest region to the Rīga harbour — the main source of non-indigenous species arrival in the Gulf. Recent studies have predicted the possible potential of E. carolleeae invasion due to its physiological plasticity. Male and female specimens of Eurytemora were collected in spring, summer, and autumn of 2013, and analysed based on three morphological indicators. Despite the higher reproduction rate of E. carolleeae, this intrusive species does not seem to have succeeded in establishing during the five-year period after its first discovery in the Gulf of Riga, and hence does not present a threat to the native E. affinis population in the study area.

Abstract
The aim of this study was to assess sediment quality in the ecoregion Engure, western coast of the Gulf of Riga, by using sediment ecotoxicity tests with amphipods Monoporeia affinis and Pontogammarus robustoides and selected biomarkers (AChE, GST, GR, CAT, MT) measured in Macoma balthica, to represent different types of biological responses reacting to different stressors. Ecoregion Engure sediments are characterised by comparatively low concentrations of heavy metals, and the area could be considered as unpolluted. Ecotoxicity tests of ecoregion Engure sediments did not show statistically significant (> 20% mortality) toxic effects. Survival of test organisms ranged from 83 to 100% and revealed "good quality" of tested sediment. There were no established strong differences between the stations and years regarding biomarkers. The integrated biomarker response index indicated more stressful conditions in station Mērsrags, while MT activity revealed heavy metal pollution in station Engure. In general, heavy metal concentrations, ecotoxicity tests and biomarker responses indicate that the ecoregion Engure is not markedly various and anthropogenically affected.

Abstract
The article discusses the results of the national project aimed at elaboration of a conceptual integrated model of the Engure LT(S)ER (Long-Term Socio-Ecological Research) platform of Latvia. The platform represents the drainage basin of costal Lake Engure (644 km2) together with the coastal marine zone of the Gulf of Rîga. The core zone of the ecoregion is the Lake Engure Nature Park (LENP), which is a Ramsar site. The conceptual model is a slightly modified version based on the DPSIR (Drivers-Pressures-States-Impacts-Responses) concept. The socioecological system was spatially demarcated and drivers were subdivided in two groups - external and local ones. The Engure ecoregion was subdivided into seven zones or sub-regions mostly demarcated by natural geological and geographical barriers. Each zone has a specific set of drivers and pressures as well as a specific ecosystem structure and elements of biodiversity. Analysis of the governing drivers and pressures was performed separately for each sub-region during three time periods: 19th century - beginning of 20th century, period of Soviet occupation (1940-1991), and period after restoration of independence of Latvia (1991 - up to now). Characteristics of the state of ecosystems and biodiversity are given. Responses of the socioeconomic component of the socio-ecological system are represented mainly by external factors to the ecoregion, including environmental legislation and funding necessary for research and ecological management. Two alternative scenarios of the development of the Engure ecoregion are discussed: (i) depopulation and land abandonment, and (ii) intensification of agriculture, small-scale industry and building construction. In both cases the present state of ecosystems and the structure of species diversity would be subjected to significant change. Sustainable development of the ecoregion can be provided only by implementation of certain environmental management measures accompanied by long-term socio-ecological research and ecological monitoring.

Water quality in cutaway peatland lakes in Seda mire, Latvia
Transformation into shallow lakes can be a major post-harvesting land-use option for cutaway peatlands. The aim of our study was to analyse factors influencing water quality and communities on lakes created in a cutaway bog in the Seda Mire, Latvia. The residual peat amount and the lake feeding conditions (the balance between ground water and inflow from adjacent river during the spring season) were found to be major factors influencing aquatic chemistry and studied habitats. The studied cutaway lakes cannot be considered as typical bog lakes regarding hydrochemical composition (especially regarding concentrations of major dissolved ions, pH and water colour) and hydrobiological features (metabolic activity, biomass and number of species of phytoplankton and zoobenthos). Considering aquatic chemistry and community structure of the cutaway lakes, a recommendation was made in respect to peat excavation to transform peat mining sites to lakes.