Agrita Briede

Heavy metals in rivers of Latvia

Total heavy metal concentrations in waters and sediments (HNO3 digestible Pb, Cu, Co, Ni, Mn, Zn) and their speciation forms in sediments (exchangeable, carbonate bound, iron-manganese oxide bound, organic matter bound and residual) in major and common small watercourses (31 sampling stations) along their flow in Latvia were determined. The metal loads entering the Baltic Sea from Latvia were calculated. Increased metal concentrations were found only in lower reaches of the largest rivers and locally around known industrial pollution sources. Differences in metal concentrations and loads in rivers from different regions of Latvia were related to natural geochemical processes. Metal speciation analysis showed that the dominant metal species are residual metals and those bound to organic matter. Residual and carbonate-bound metal dominated only in rhitral regions of rivers. The concentrations of exchangeable metals increased below pollution sources.

Biological quality metrics: their variability and appropriate scale for assessing Streams

The concept of spatial scale is at the research frontier in ecology, and although focus has been placed on trying to determine the role of spatial scale in structuring communities, there still is a further need to standardize which organism groups are to be used at which scale and under which circumstances in environmental assessment. This paper contributes to the understanding of the variability at different spatial scales (reach, stream, river basin) of metrics characterizing communities of different biological quality elements (macrophytes, fishes, macroinvertebrates and benthic diatoms) as defined by the Water Framework Directive. For this purpose, high-quality reaches from medium-sized lowland streams of Latvia, Ecoregion 15 (Baltic) were sampled using a nested hierarchical sampling design: (river basin → stream → reach). The variability of metrics within the different groups of biological quality elements confirmed that large-bodied organisms (macrophytes and fish) were less variable than small-bodied organisms (macroinvertebrates and benthic diatoms) at reach, stream and river basin scales. Single metrics of biological quality elements had the largest variation at the reach scale compared with stream and basin scales. There were no significant correlations between biodiversity indices of the different organism groups. The correlation between diversity indices (Shannon’s and Simpson’s) of the biological quality eleme (macrophytes, fish, benthic macroinvertebrates and benthic diatoms) and a number of measured environmental variables varied among the different organism groups. Relationships between diversity indices and environmental factors were established for all groups of biological quality elements. Our results showed that metrics of macrophytes and fish could be used for assessing ecological quality at the river basin scale, whereas metrics of macroinvertebrates and benthic diatoms were most appropriate at a smaller scale.

Metal accumulation in sediments and benthic invertebrates in lakes of Latvia

The concentrations of cadmium, lead, nickel and copper in waters, sediments (total metal concentrations and their speciation forms) and benthic macroinvertebrates in 11 lakes of Latvia were determined using atomic absorption spectroscopy. Metal concentrations in lake waters, sediments and biota were compared with water chemistry. Compared to total concentrations, metal speciation forms in sediments were better correlated with respective metal concentrations in invertebrates. Therefore, the evaluation of potential metal bioaccumulation should consider metal speciation. The mean concentrations of trace metals in benthic invertebrates in Latvia were much lower than in other countries, which can be explained by comparatively lower anthropogenic loads. However, local areas of anthropogenic impacts were evident.

Past and current climate change

This section describes long-term observed climatic changes in atmospheric parameters. The focus is on surface climate conditions, but changes in atmospheric circulation are discussed as they often are behind climatic variability seen on regional and local scales. For a summary introduction on mean atmospheric states and conditions in the Baltic Sea Basin see Annex 1.2 with sections on the general atmospheric circulation (A.1.2.1), surface air temperature (A.1.2.2), precipitation (A.1.2.3), clouds (A.1.2.4), and global radiation (A.1.2.5).

Variability and trends in daily minimum and maximum temperatures and in the diurnal temperature range in Lithuania, Latvia and Estonia in 1951–2010

Spatial distribution and trends in mean and absolute maximum and minimum temperatures and in the diurnal temperature range were analysed at 47 stations in the eastern Baltic region (Lithuania, Latvia and Estonia) during 1951–2010. Dependence of the studied variables on geographical factors (latitude, the Baltic Sea, land elevation) is discussed. Statistically significant increasing trends in maximum and minimum temperatures were detected for March, April, July, August and annual values. At the majority of stations, the increase was detected also in February and May in case of maximum temperature and in January and May in case of minimum temperature. Warming was slightly higher in the northern part of the study area, i.e. in Estonia. Trends in the diurnal temperature range differ seasonally. The highest increasing trend revealed in April and, at some stations, also in May, July and August. Negative and mostly insignificant changes have occurred in January, February, March and June. The annual temperature range has not changed.

Metals in sediments of lakes in Latvia

Abstract The concentrations and speciation forms of Pb, Cu, Ni, Cd, Zn, and Mn have been determined in sediments from 49 lakes thoroughout Latvia to study the impact of different pollutant sources and to estimate the background pollution level. Regional variation in pollutant distributions of Pb, Cu, and Cd concentrations is due to anthropogenic load. The enrichment of metals in the top layer of sediments is an estimate of the environmental pollution level. In regions with no known pollution sources, this enrichment was not typical. Another factor that determines metal concentrations in sediments is the organic matter production and sedimentation in eutrophic water bodies.

Recent change - atmosphere

This chapter examines past and present studies of variability and changes in atmospheric variables within the North Sea region over the instrumental period; roughly the past 200 years. The variables addressed are large-scale circulation, pressure and wind, surface air temperature, precipitation and radiative properties (clouds, solar radiation, and sunshine duration). Temperature has increased everywhere in the North Sea region, especially in spring and in the north. Precipitation has increased in the north and decreased in the south. There has been a north-eastward shift in storm tracks, which agrees with climate model projections. Due to large internal variability, it is not clear which aspects of the observed changes are due to anthropogenic activities and which are internally forced, and long-term trends are difficult to deduce. The number of deep cyclones seems to have increased (but not the total number of cyclones). The persistence of circulation types seems to have increased over the past century, with ‘more extreme’ extreme events. Changes in extreme weather events, however, are difficult to assess due to changes in instrumentation, station relocations, and problems with digitisation. Without thorough quality control digitised datasets may be useless or even counterproductive. Reanalyses are useful as long as biases introduced by inhomogeneities are properly addressed. It is unclear to what extent circulation over the North Sea region is controlled by distant factors, especially changes in Arctic sea ice.

Long-Term Ecological Research in Latvia

The article describes the National Long-term Ecological Research (LTER) Network of Latvia, which includes five study sites and eight research projects. It is supported by the Latvian Council of Sciences. The main directions of the research are impacts of climate warming and anthropogenic factors on terrestrial and freshwater communities and ecosystems. Characteristics of research sites are presented. The main results of the long-term investigations and their implementation in ecological management projects are described.

Long-term Development of the Hydroecosystem of the Lake Engure and its Influencing Factors

Long-term Development of the Hydroecosystem of the Lake Engure and its Influencing Factors Investigations of water chemical composition and biota of Lake Engure have been carried out since 1995 by using standard methods for inland surface waters. Time series of air temperature and precipitation for the Mersrags meteorological station for the period 1928 to 2009 are used for the trend analysis. The results show that the long-term development of the hydroecosystem is related to such environmental factors as the lakes geographical location, basin and morphology, as well as the lakes history and relationship of biotic and abiotic factors. Engures ezera hidroekosistēmas ilgtermiņa attīstība un to ietekmējošie faktori Engures ezers ir lielākā reliktā ūdenstilpe Rīgas līča piekrastē. Tas ir sekls, morfometriski eitrofs caurplūstošs ezers. Ezers ir Ramsāres vieta, atrodas Engures dabas parkā, kas ir biologiski daudzveidīga teritorija. Ezera ilgtspējīgas attīstības iespējas saistītas ar vairākiem faktoriem. Engures ezerā ūdens ķīmiskā sastāva un planktisko un bentisko sabiedrību izpēte notiek kopš 1995.g., izmantojot hidroķīmiskās un hidrobiologiskās standartmetodes. 2010.g. veikta arī augstāko augu sabiedrību izpēte. Klimata datu analīzei izmantoti Latvijas Vides, geologijas un meteorologijas centra dati no Mērsraga meteorologiskās stacijas par laiku no 1928.g. līdz 2009.g, Rezultāti liecina, ka Engures ezera regionā notikusi būtiska gada vidējās temperatūras palielināšanās, temperatūras pieauguma tendences vērojamas arī vasarā un pavasarī. Būtiskas nokrišņu izmaiņas nav novērotas. Ezers joprojām ir dzidrūdens stāvoklī, fitoplanktona biomasas ir zemas un nav novērojamas izmaiņas dominējošo aļgu grupu struktūrā. No lokālajiem faktoriem visbūtiskāk ezera ekosistēmu ietekmējusi antropogēnā darbība - 19.gs. vidū izraktais Mērsraga kanāls, kas savieno ezeru ar Rīgas līci. Tas izmainījis ezera morfometriju un ietekmē ezera ziemeļu daļas ūdens ķīmisko sastāvu, kā arī organismu sabiedrību sugu sastāvu. Tikpat būtiska ir ezera geologija un ezerā ietekošās upes, kas ietekmē ūdens cietību, līdz ar to - fosfora atrašanos saistītā formā un mieturaļgu attīstību, kas kavē sedimentu resuspensiju. Fitoplanktons vāji izmanto saistīto fosforu un ezera eitrofikācija izpaužas pastiprinātā augstāko augu attīstība. Kopumā lokālo faktoru (gan antropogēno, gan dabisko) loma ir noteicoša pašreizējā ezera attīstības stadijā. Долгосрочное развитие озера Энгурес и влияющие на него факторы Озеро Энгуре - крупнейшее реликтовое озеро побережья Рижского залива. Мелководное, морфометрически эвтрофное проточное озеро. Озеро Энгуре является объектом Рамсарской конвенции, а также основной частью природного парка Энгуре, имеющего статус территории биологического разнообразия. Долговременное развитие озера связано с несколькими факторами. Относительно регулярные исследования химического состава вод, планктонных и бентосных сообществ озера с использованием стандартных гирохимических и гидробиологических методов проводятся с 1995 года. В 2010 году проведены картирование и анализ высшей водной растительности. Для анализа климатических показателей использованы данные Латвийского центра среды, геологии и метеорологии (станция наблюдений Мерсрагс) за период с 1928 по 2009 годы. Анализ результатов измерений показывают, что в регионе озера с 70-х годов прошлого века существенно увеличились средняя годовая температура воздуха, увеличились тренды средних температур весной и летом. Среднегодовое количество осадков значительно не изменилось. Озеро прозрачное, биомассы фитопланктона низкие и значительные изменения в структуре доминирующих групп водорослей не найдены. В историческом плане существенное антропогенное вмешательство в экосистему озера произошло в середине 19 века - прорытием канала, соединившего озеро с Рижским заливом. Это изменило морфометрию озера, периодическое проникновение солоноватых вод залива повлияло на химический состав, особенно северной части, а также отчасти на видовой состав сообществ организмов. На остальные части озера столь существенно влияют геологическое строение водосбора и приток рек в озеро, обуславливающий гидрокарбонатную жесткость воды, содержание фосфора в связанной форме, что в свою очередь влияет на развитие харовых водорослей, задерживающих ресуспенсию донных отложений. Форма связанного фосфора слабо используется фитопланктоном, поэтому главную роль в эвтрофировании озера на данном этапе принадлежит высшей водной растительности.

Hydrometeorological parameters and aquatic chemistry of Lake Engure: Trends of changes due to human impact and natural variability

Hydrometeorological parameters and aquatic chemistry of Lake Engure: Trends of changes due to human impact and natural variability Lake Engure, located in Latvia, is the largest shallow coastal lake that developed after retreat of the Littorina Sea. It supports high biodiversity and has national and international importance. Engure is a hardwater lake with abundant macrophyte and charophyte vegetation. The present study determined the impact of the main meteorological indicators related to global warming, and also indicators of climate extremes. The lake water level is regulated by hydrotechnical constructions. In the the warm period (April-October) of the year the lake level tends to increase. However, from a perspective of long-term changes, there was a good relationship between the Western type of Atmospheric Circulation Index and water level in general, and also between NAO index in March and lake water level in April. Regarding water chemical composition, there has been a decrease of phosphorus concentration while ammonium and nitrate concentrations have not changed. Ionic composition of Lake Engure is characterised by dominance of hydrocarbonates, calcium and magnesium ions. Engures ezera hidrometeorologisko parametru un ūdeņu ķīmiskā sastāva mainības tendences: antropogēno faktoru un dabiskās mainības ietekmes Engures ezers kā Rīgas līča piekrastes seklūdens ezers, kas izveidojies, atkāpjoties Litorīnas jūrai, ir nacionāli un starptautiski nozīmīgs, ņemot vērā tā ekosistēmu augsto biologisko daudzveidību. Engures ezera ūdeņus raksturo augsta cietība, kas ietekmē iegremdētās un piekrastes joslas vegetāciju. Pētījumā izvērtēts galveno hidrometeorologisko parametru un klimata indikatoru (it īpaši ekstremālo klimatisko parādību) mainības raksturs un pierādītas globāli noritošās pasiltināšanās ietekmes. Esošo ezera ūdens līmeni nosaka hidrotehnisko būvju izveide, bet gada siltajā periodā ir raksturīgs ūdens līmeņa pieaugums, turklāt ilgtermiņā ezera ūdens līmeņa izmaiņas ietekmē atmosfēras gaisa masu pārnese no Ziemeļatlantijas. Pierādīta korelācija starp Ziemeļatlantijas oscilācijas indeksu martā un ezera ūdens līmeni aprīlī. Ūdens ķīmiskā sastāva izmaiņas raksturo fosfora koncentrāciju samazināšanās un relatīvi stabilas slāpekļa savienojumu koncentrācijas. Neorganisko jonu kompozīciju raksturo kalcija, magnija un hidrogēnkarbonātjonu dominance.