INTRODUCTION In contrast to other harmful metals, as e.g. mercury and cadmium, the concentrations of lead in coastal fishes from the Baltic Sea have attracted far less attention (e.g. von Westernhagen and Bignert, 1996; Jezierska and Witeska, 2001; Szefer, 2002; Pokorska et al., 2012; Nyberg et al., 2013; Boalt et al., 2014) although effects of this toxic metal on humans (e.g. Guinnee, 1972; Bremner, 1974; Brian et al., 1980; IPCS, 1989; ATSDR, 2005), fishes, mammals, and birds (e.g. Haider, 1964, 1977; NRCC, 1979; Atchison et al., 1987; Eisler, 1988; Hofer and Lackner, 1995; Pain, 1996; Dietz et al., 1998) have been documented. Considering the significant inflow of lead into the sea and over its vast drainage area (e.g. Ruhling et al., 1992; HELCOM, 1997, 2003, 2010; Bartnicki et al., 2000; Buse et al., 2003) this is rather surprising. In the 1970s some investigations on the concentrations of lead in certain species of Baltic fish, mainly Baltic herring (Clupea harengus membras L.) and cod (Gadus morhua callaris L.), were performed (e.g. Lehtonen, 1973; Voipio et al., 1977; Tervo et al., 1980; Perttila et al., 1982), followed by attempts at its monitoring, mainly in the muscle tissue of herring and in the liver of cod, for the Baltic Marine Environment Protection Commission (Helsinki Commission, HELCOM) by some Baltic national research institutes, e.g. the Finnish Institute of Marine Research (Haahti, 1991), the Swedish Museum of Natural History (Jorhem and Sundstrom, 1993), and the Estonian Marine Institute (Jankovski et al., 1996). In the southern Baltic Sea similar investigations additionally included sprat (Sprattus sprattus balticus Schn.), flounder (Platichthys flesus L.), perch (Perca fluviatilis L.), and some other species (Falandysz and Lorenc-Biala, 1984). After confirmation that lead mainly concentrates in internal organs, such as kidney and liver, and bone tissue of fish (e.g. Reichenbach-Klinke, 1980), and not in muscle tissue like mercury, the interest in such monitoring declined significantly, especially because the observed concentrations of lead in the muscle tissue of fish were far below the accepted security levels for fish as food for human consumption (e.g. Nuutamo et al., 1980; Haahti, 1991; Tahvonen and Kumpulainen, 1996; Leivuori, 2007). Starting again in the 1980s, monitoring of the concentrations of lead has been continued, with mainly liver and muscle tissue of herring studied (e.g. Jankovski et al., 1996; Roots and Simm, 2002; Lind et al., 2006; Leivuori, 2007). The present study focuses on the concentrations of lead in the muscle tissue and some internal organs, mainly liver, but in some cases also in gonads, kidneys, spleen, and bile, of some representative coastal fish species from various parts of the Baltic Sea, including two coastal inlets in SW Finland (isolated in the late 1950s from the Baltic Sea). The aim is to survey and to compare the concentrations of lead in the similar fish species as in previous studies from various parts of the Baltic Sea (Voigt, 1999, 2000a, 2000b, 2003, 2004, 2008a, 2008b, 2013). MATERIAL AND METHODS Some abundant coastal fish species (adults and mainly of comparable size for each species separately, with the exception for the fishes from two isolated freshwater reservoirs, see below) from various parts of the Baltic Sea (Fig. 1) were sampled in the autumn season during the years 1997-2006 for analysis of concentrations of lead in muscle tissue and some internal organs, mainly liver and gonads. Besides bow-nets and gillnets trawling was used for sampling. The following five fish species were focused upon: * Baltic herring, sampled from Peimari-Pemarn in the Finnish Archipelago Sea ([Angstrom]-AS), Tvarminne area at the Finnish SW coast of the Gulf of Finland (H-Tva), and Vaike Vain Strait at the western Estonian coast (VV); * smelt (Osmerus eperlanus L.) from the rivermouth area of the Kokemaenjoki-Kumoalv in the Bothnian Sea (RKK), Peimari-Pemarn (A-AS), Tvarminne (H-Tva), Vaike Vain (VV), and south-western coastal freshwater basin of Pargas-Parainen (PP); * perch from Tvarminne (H-Tva), Vaike Vain (VV), Pargas-Parainen (PP), and the southern coastal freshwater basin of Gennarby (Gby); * eelpout (Zoarces viviparus L. …
INTRODUCTION Transitional waters, for example lagoons, represent important but fragile ecosystems in the coastal landscape, providing key ecosystem services such as water quality improvement, fisheries resources, habitat and food for migratory and resident animals, and recreational areas for human populations. The Anzali International Wetland was registered in the Ramsar Convention in 1975 as Ramsar Site #40, Wetlands International Site Reference No. 2IR005 (JICA 2005). The Anzali Wetland complex comprises large, shallow, eutrophic freshwater lagoons, shallow impoundments, marshes, and seasonally flooded grasslands at the south-western coast of the Caspian Sea (Fig. 1). It consists of different aquatic and dry land ecosystems and is a good example of a natural habitat supporting an extremely diverse wetland flora and fauna (Ayati 2003). Oligochaete annelids have a worldwide distribution, being frequently the most abundant benthic organisms in freshwater ecosystems; many species are cosmopolitan (Brinkhurst and Jamieson 1971). They are used in biodiversity studies, pollution surveys, and environmental assessment and have also economic importance (Mason 1996; Wetzel et al. 2000; Rodriguez and Reynoldson 2011). Although many researchers have studied the Anzali Wetland from the pollution-related, faunistic, and ecological points of view (e.g. Ayati 2003; JICA 2005; Charkhabi and Sakizadeh 2006; Akbarzadeh et al. 2008; Jafari 2009; Tahershamsi et al. 2009; Mirzajani et al. 2010; Pourang et al. 2010; Jamshidi-Zanjani and Saeedi 2013), there are no data on the species diversity of the Oligochaeta of the region, except the single record of Tubifex tubifex by Pourang (1996). The aquatic Oligochaeta species of Iran are mentioned only in a few papers: Stephenson (1920), Egglishaw (1980), Aliyev and Ahmadi (2010), Ahmadi et al. (2011, 2012), Ardalan et al. (2011), Jablonska and Pesic (2014). Until now 19 species of aquatic oligochaetes occurring in inland waters of Iran have been recorded. The aim of this study was to evaluate the diversity and distribution of this group and to contribute to the Oligochaeta fauna of both the Anzali Wetland and Iran. MATERIAL AND METHODS Study area The Anzali International Wetland (37[degrees]28' N, 49[degrees]25' W), one of the largest freshwater coastal wetlands of Iran, is located in the Guilan Province at the south-western coast of the Caspian Sea and covers an area of 193 [km.sup.2] (Pourang et al. 2010) (Fig. 1). The main wetland covers about 11 000 ha; it comprises an open freshwater lagoon with a length of 26 km and a width of 2.0-3.5 km, surrounded by reed beds extending its eastern border for another 7 km. Eleven rivers and groundwater seeps feed the wetland. The wetland complex is separated from the Caspian Sea by a dune system; the passage to the sea has a width of 426 m. The wetland supports extensive reed beds and an abundant submerged and floating macrovegetation. Its permanently aquatic portion is surrounded by seasonally flooded marshes and water impoundments, which are also fringed by reed beds and damp grassland. The southern part of the wetland is mainly adjacent to rice fields and patches of woodland, while the northern part borders on sand dunes with grassland and a scrubby vegetation. The wetland consists of four main parts: the western, the central (Sorkhankol Wildlife Refuge), the south-western (Siahkeshim Protected Area), and the eastern; the last part has different physico-chemical, morphologic, phytoecological, and geographical characteristics, including a higher anthropogenic pressure (Ayati 2003). [FIGURE 1 OMITTED] Total precipitation in the Anzali Wetland is about 1500 to 2000 mm [y.sup.-1]. Maximum water depth is about 3 m but it is fluctuating (Jafari 2009). The water depth has decreased, owing to solid sedimentation, in some parts to less than 0.5 m (Ayati 2003). In the last ten years, salinity has slightly increased with the rise of the level of the Caspian Sea, which has caused more intensive mixing of water, as well as with the inflow of salt from increased upstream irrigation. …
Hydromorphological quality assessment is an important research topic, especially after the implementation of the EU Water Framework Directive.In this study the hydromorphological quality at 46 sites in 22 streams of the Venta River Basin District (RBD) in Latvia was investigated during the vegetation periods of 2011-2013.The UK River Habitat Survey method was used in the research.No significant differences in Habitat Quality Assessment (HQA) and Habitat Modification Scores (HMS) were found between stream types.We found that the most important factor affecting HQA scores in our research territory was instream vegetation, which coincides with results of other researchers.There was a significant negative correlation between HQA and HMS.Distance from the source had a negative correlation with HQA and a positive correlation with HMS.River type had a positive correlation with special features (beaver dams, fringing reed bank, wetlands, etc.).
Three dams affect the flow of the lower Daugava River.The water reservoirs created by damming are relatively small with residence times from three to nine days.However, the water flow alteration is sufficient to cause a decrease in the phytoplankton biomass from an average of 246 to 96 mg m -3 .The diatom community was dominated by single-cell and small (d = 5-10 µm) centric diatoms under the unaltered flow conditions.Under the altered flow conditions, chain-forming freshwater planktonic diatoms and singe-cell pennatae diatoms dominated the diatom community.The concentrations of dissolved silica varied between 51 and 121 µmol dm -3 and of biogenic silica from 1 to 12 µmol dm -3 .In both cases the lowest values were observed during summer months.Furthermore, dissolved and biogenic silica concentrations were higher at stations representing unaltered flow conditions in comparison to those representing altered flow conditions during summer.
Seagrasses are marine angiosperms fulfilling important ecological functions in coastal ecosystems worldwide. Out of the 66 known seagrass species only two inhabit the Baltic Sea and only one, Zostera marina L., is found in its NE part. In the coastal waters of Estonia, where eelgrass grows at its salinity tolerance limit, only scarce information exists on the Z. marina community and there are no data on eelgrass growth. In the current study the community characteristics and growth of eelgrass were studied at four sites: Ahelaid, Saarnaki, and Soru in the West-Estonian Archipelago Sea and Prangli in the Gulf of Finland. Fieldwork was carried out from May to September in 2005. The results showed that eelgrass grew between 1.8 and 6 m with main distribution at 2-4 m. The eelgrass bed had a considerably higher content of sediment organic matter compared to the adjacent unvegetated areas, but this difference was statistically significant only in areas where the movement of soft sediments is higher. The results also showed that altogether 19 macrophytobenthic and 23 invertebrate taxa inhabited the eelgrass stand. The prevailing vascular plants were Stuckenia pectinata and Potamogeton perfoliatus. Besides attached macrophytes, drifting algae were recorded within the eelgrass communities throughout the study period. Most common invertebrate species inhabiting eelgrass stands were Peringia ulvae, Cerastoderma glaucum, Mytilus trossulus, Macoma balthica, Mya arenaria, Theodoxus fluviatilis, and Idotea chelipes. Irrespective of the studied basin, the increasing eelgrass density supported an elevated diversity and abundance of benthic invertebrates. The eelgrass shoot biomass showed a constant increase from May to September. The overall growth pattern was similar for all studied areas but varied among depth strata. The average shoot density of eelgrass was 50-1300 shoot per m 2 , average biomass ranged from (0.75) 7.8 to 37.31 g dw m -2 in spring and from 18.42 to 68.59 g dw m -2 in autumn.
INTRODUCTION Charophyte communities are an important element in shallow enclosed fresh- and brackish-water ecosystems (Mathieson and Nienhuis, 1991; van den Berg et al., 1998; Pelechaty et al., 2006). They provide shelter and habitat for numerous species including epiphytic microalgae, filamentous macroalgae, as well as various crustacean and insect species (Linden et al., 2003; Schmieder et al., 2006; Torn et al., 2010). Besides, charophytes are an important component in the food web as part of the diet of benthic invertebrates (Kotta et al., 2004, 2013), waterfowl (Noordhuis et al., 2002; Schmieder et al., 2006), and fish and fish larvae (de Winton et al., 2002; Dugdale et al., 2006). Declining distribution and diversity of charophytes have been observed in many regions worldwide including the brackish Baltic Sea (Blindow, 2000, 2001; Schubert and Blindow 2003; Munsterhjelm, 2005). Eutrophication is assumed to be the most important threat to charophytes causing their decline (e.g. Blindow, 1992; Auderset Joye et al., 2002). The main effect associated with eutrophication is the bloom of ephemeral planktonic algae, which leads to increased sedimentation, water turbidity and, as a result, reduced light availability. The shortage of light may reduce the photosynthetic production and growth of charophytes down to the level where their sustainable development becomes impossible (Blindow et al., 2002; Johnsen and Sosik, 2004; Hautier et al., 2009; Dickey et al., 2011). On the other hand, charophytes often prefer soft bottom habitats where even moderate wind may cause sediment resuspension and sedimentation of particles on the plant surface. In such habitats underwater light climate is naturally very variable (Schneider et al., 2006 and references therein). Thus, charophytes are adapted to periodic stress of low light intensities. Nevertheless, the interactive effect of elevated eutrophication and weather variables may result in poorer light conditions than expected from their separate effects (Blindow et al., 2003; Kling et al., 2003). So far, the studies concerning photosynthesis of charophytes are mainly based on laboratory experiments with either detached pieces or single individuals (e.g. Blindow et al., 2003; Marquardt and Schubert, 2009). Very few have been carried out in the natural environments, especially in brackish bodies of water. As compared to their freshwater counterparts, charophytes are often naturally stressed at elevated salinity and therefore are expected to respond differently to changes in light conditions (e.g. Blindow et al., 2003). The existing data on in situ primary production of charophytes related to light limitation are scarce and hardly comparable because of difference in methodologies and the environmental conditions among habitats (Kufel and Kufel, 2002). Light is a key limiting factor for photosynthetic production in aquatic environments (Kurtz et al., 2003; Asaeda et al., 2004, Binzer et al., 2006; Zhang et al., 2010). Earlier experimental studies carried out at the community level have also shown that canopy density and canopy structure significantly affect the photosynthetic production of marine macroalgae (Middelboe et al., 2006). This suggests that macroalgal communities are largely light-limited and such light limitation increases with canopy height and/or community biomass (Parnoja et al., 2013). Altough the photosynthetic production of marine macroalgae at the community level has been increasingly studied (Middelboe and Binzer, 2004; Middelboe et al., 2006; Parnoja et al., 2013), to the best of our knowledge, there is only a single study on charophyte communities (Libbert and Walter, 1985). Based on the above, our goal was to determine the primary production of a charophyte community under manipulated in situ light conditions. We hypothesized that (a) the community would have higher responses under more severe light limitation and (b) the recovery of charophyte photosynthetic performance would be faster under less severe disturbances. …
We studied the wing dimorphism in Roesel's bush cricket populations. A total of 410 individuals (77 macropterous and 333 brachypterous) were sampled in seven sites. We found a high frequency (≤ 53%) of macropterous individuals in some meadows surrounded by forests. We measured the body weight, thorax weight, and abdomen weight in connection with macroptery vs brachyptery. We could find a positive correlation between macroptery and thorax weight. The abdomen weight of females showed high individual variation; thus the supposed trade-off between macroptery and lower fertility of females was not supported.
INTRODUCTION Zoopsammon is a diverse group of organisms living in the interstitial spaces between sand grains at the shoreline. The term psammon is nowadays mainly used to characterize freshwater sandy beach habitats, although it was originally defined as 'a transitional zone between aquatic and soil habitats' (Schmid-Araya, 1998), and is also applicable to brackish and marine beach habitats, where the intertidal zone can be considered as psammon habitat if the sediment consists of sand and is regularly exposed (e.g. Tzschaschel, 1983; Golemansky, 1998; De Smet and Chernyshev, 2006; Alekperov et al., 2007). However, in the marine literature psammic comunities are more often referred to as meiofauna. Psammon communities have received very little attention compared to lower littoral and sublittoral meiobenthos, and psammon has been rarely treated as a single entity. Despite its unstable and very fluctuating environment, the arenal zone hosts a large variety of species (Pejler, 1995; Golemansky, 1998; Gheskiere et al., 2005). Protists, nematodes, rotifers, small crustaceans, tardigrades, gastrotrichs, turbellarians, oligochaetes, and insect larvae are regularly found from psammon habitats (Thane-Fenchel, 1968; Whitman and Clark, 1984; Schmid-Araya, 1998, Kotwicki et al., 2005a, 2005b). From psammic taxa, rotifers have received relatively much attention in freshwater habitats (e.g. Pejler, 1995; Bielariska-Grajner, 2001; Segers and Chittapun, 2001). In marine beach habitats, nematodes tend to be the most thoroughly researched psammic taxa (e.g. Gheskiere et al., 2004, 2005; Liu et al., 2008; Maria et al., 2012, 2013). From the Baltic Sea area some information is available on psammic ciliates (Czapik and Fyda, 1992), testate amoebae (Golemansky, 1998), rotifers (Thane-Fenchel, 1968; Sorensen, 2001), and nematodes (Gheskiere et al., 2005). In Europe, freshwater zoopsammon has received more attention in Poland (e.g. Bielariska-Grajner, 2001; Ejsmont-Karabin, 2003; Nesteruk, 2007; Kalinowska, 2008, 2013; Bielaiska-Grajner and Poznaiska, 2010). At the Estonian water bodies, the coastal zone was sampled already in the 19th century. In these studies, some beach invertebrates were recorded (Eichwald, 1849, 1852; Levander, 1894). However, it is not known where exactly the samples were taken (water or sediment, at waterline/beach or deeper water). First true reports on the interstitial fauna, i.e. zoopsammon, of sandy beach in Estonia date from the 1980s. In these sampling campaigns, Golemansky (1983) investigated psammic testate amoebae from the Estonian coast of the Gulf of Finland, and Kutikova and Haberman (1986) determined the taxonomic composition of rotifers from the arenal zone of Lake Vortsjarv. Recently, some information has been provided about the taxonomic composition and density of zoopsammon communities, their temporal and spatial distribution, and relation with various environmental variables in some Estonian coastal beaches (Lokko et al., 2014) and in two lakes (Lokko et al., 2013; Lokko and Virro, 2014). The aim of this study is to provide an overview and sum up the current knowledge on the taxonomic structure of zoopsammon in Estonian waters. This summarized information serves as a basis of the current status of psammic communities both in freshwater and marine habitats and potentially allows assessing the current status and conservation value of Estonian interstitial beach habitats. MATERIALS AND METHODS The present study is based on two previous studies (Lokko et al., 2013, 2014) and an additional sampling campaign carried out in 2011-2014. Samples were taken from three sandy beaches along the Estonian coast of the Gulf of Finland, Baltic Sea, and from four lakes across Estonia (Fig. 1). The coastal sampling sites were located at Keibu Bay near Nova village (Nova Beach, the westernmost sampling site), at Pirita Beach within Tallinn City, and at a popular beach of Narva Bay adjacent to a small town of Narva-Joesuu (the easternmost site). …
Summer blooms of nitrogen-fixing filamentous cyanobacteria are recurrent phenomena in the Baltic Sea.Salinity, varying from 0 to10 PSU in the surface layer of the Baltic Sea, is among the major factors affecting the basin-scale distribution of various bloom-forming cyanobacterial species.The effects of salinity on the growth rate and cellular carbon, nitrogen, and phosphorus ratios of two major cyanobacterial species that form dense blooms in the Baltic, Aphanizomenon sp.(strain KAC 15) and Nodularia spumigena (strain HEM), were studied.Cells were grown under N 2 -fixing conditions in a salinity gradient from 0 to 10 PSU.The growth rates of the species showed contrasting responses to salinity.For Aphanizomenon sp. the maximum growth rates (0.28-0.31 d -1 ) were observed at salinities of 0-2 PSU, while for N. spumigena the maximum growth rate occurred at 8-10 PSU (0.14-0.16 d -1 ).The latter species did not tolerate low salinities (< 2 PSU).The observed differences in salinity tolerances constrain the distribution patterns of these two species during cyanobacterial blooms, Aphanizomenon sp.being more abundant in the coastal and less saline areas.The variations in growth rates were largely reflected in cellular N : P and C : P ratios, which varied two-fold, and in C : Chla ratios with 5-fold variability.Cellular C : N ratios were rather constant at all salinities and close to the Redfield ratio for Aphanizomenon sp.(on average 5.9 g g -1 ) and above the Redfield ratio for N. spumigena (on average 8.0 g g -1 ).The relatively higher N : P and lower C : N ratio showed a higher need of N for Aphanizomenon sp.than for N. spumigena.This is partly explained by the higher abundance of N-rich phycobilin pigments in Aphanizomenon sp. as indicated by fluorescence measurements.The observed differences in pigmentation indicate species-specific strategies in light harvesting.
A national assessment system for the classification of the ecological status of coastal waters according to the requirements of the EU Water Framework Directive was established in Estonia in the year 2007. The Estonian Phytobenthos Index was used to assess the ecological status of coastal waters based on submerged aquatic vegetation. After the testing period it appeared that the selected method did not respond to anthropogenic pressure in two national water types: the Vainameri and Parnu Bay. During this study new indexes were developed and validated against pressure for these areas. The PCF index was combined from the proportion of perennial species, charophytes, and Fucus spp. This index is suitable for the assessment of the ecological status in the Vainameri area. In Parnu Bay the depth distribution of higher plants and the proportion of opportunistic species showed the strongest correlation with eutrophication variables. These metrics were combined into the HPO index. The class boundaries for assessing the ecological status of water quality were determined for both indexes. The paper describes the calculation of the indexes.
This review summarizes winter conditions from six polymictic European shallow lakes. The lakes range from oligotrophic to hyper-eutrophic. Four of the lakes freeze regularly while ice cover is absent or rare in the two others. Ice duration and timing of ice-out are significantly influenced by climate signals in three of the lakes. Winter water temperature remains higher in non- ice-covered lakes. No long-term trend in temperature is detectable except for one lake where winter water temperature began to increase in 1986. Secchi depth in winter is equal or greater than summer values in all six lakes indicating relatively better light conditions in winter. Total phosphorus concentration in winter ranges from 10 to 130 µg L -1 , which is equal or lower than summer values and is unrelated to chlorophyll a in five of the sites. Phytoplankton species composition during winter differs largely at the six sites. The winter assemblages largely depend on the trophic level and the conditions during the previous season. Winter chlorophyll a and phytoplankton biomass are usually lower than summer values because of reduced photosynthetic rates. Bacterial production often exceeds primary production. Epipelic algal assemblages tend to proliferate during winter in both ice-covered and non-ice-covered lakes. Primary production is low during winter because of insufficient light. Zooplankton abundances and biomass critically depend on conditions during the previous season and the winter situation and are quite variable from year to year, but their values correlate with the trophic status of the lakes. As a result, winter conditions are important to understand seasonal and annual changes in shallow lakes.
The study was performed on the basis of an inventory of the genus Tilia in Latvia.A total of 134 dendrological objects were inventoried in order to clarify factors limiting the distribution of linden in the territory of Latvia.During the 2007-2013 inventory 47 taxa of Tilia were found.The taxa and their winter hardiness were evaluated according to the Sokolov scale.In the interpretation of the distribution of taxa 16 geographical and climatic factors were used.Spearman's rank correlation indicated a connection with 11 factors, among them distance to the sea, height above sea level, average January temperature, sum of negative temperatures, and amount of annual precipitation.The results of statistical analysis demonstrated an irregular connection between the geographical distribution of the genus Tilia and ecological factors.A negative correlation with height above sea level was observed for T. americana, T. × moltkei, and T. platyphyllos subsp.platyphyllos.Analysis of winter hardiness of trees revealed that trees get frozen in hard winters although they grow in hardiness zones that fit linden.
This article focuses on the socioeconomic aspects of recreational ice fishing and on the related pressures on the fish stocks of Lake Peipsi in changing ice conditions. Structured interviews conducted with anglers were combined with the assessment of the landings, the numbers of fisher- men, and fluctuations in ice-cover periods. At weekends, up to 3000 anglers were observed on the Estonian side of the ice-covered lake. Respondents defined ice fishing as a hobby; however, financial gain from selling caught fish was an important incentive for retired or unemployed persons. Eurasian perch, Perca fluviatilis L., was the most important target fish. Catches amounted from 0 to 20 kg (mean ~ 4 kg) per day per angler. Depending on the length of the ice-cover period, which varied from a few days to four months, the total catch may differ about ten times. In the case of long ice-cover periods, anglers may fish out approximately 40% of the total catch of perch, roach, Rutilus rutilus (L.), and ruffe, Gymnocephalus cernuus (L.) in the lake. However, favouring recreational fisheries would help to maintain the traditional fisheries-dependent lifestyle and benefit socioeconomically less secured people around Lake Peipsi and beyond.
We studied relationships between nutrient loading, local abiotic variables, richness and biomasses of macrophytes, and associated invertebrate species in the north-eastern Baltic Sea.The study showed that nutrient load strongly correlated to the richness and biomass of macroalgal and invertebrate species and functions and often interacted with local abiotic variables such as salinity and depth.Generally elevated nutrient loads increased the species richness of macrophytes and benthic invertebrates and the biomass of annual macroalgae and of the majority of invertebrate feeding groups, but reduced the biomass of perennial macroalgae.The study also showed that the effect of nutrient loading was scale-specific, i.e. different responses to nutrients were observed at water-body and gulf scales.The biomass of the majority of species and functions was a function of the gulf-scale nutrient loading whereas the variability of annual algae and chironomidae reflected changes in the water-body level nutrient loading.
A list of 212 bryophyte species occurring in Estonian mires was compiled using published sources, databases, and specimens from Estonian herbaria. The highest number of species, 153, occur in fens, 98 species have been found in transitional mires, and 77 in bogs. Of the mire species 10 are protected by law and 42 are redlisted in Estonia. The present list is a basis for further scientific investigations and nature protection planning.
Zooplankton has been acknowledged as an intermediate link between bottom-up and toptown regulators, thereby indirectly describing trophic interactions in various food webs.We used zooplankton as a core indicator of biodiversity in the species-poor ecosystem of the northeastern Gulf of Riga by evaluating its role as a dietary component of pelagic fishes.Furthermore, seasonal and interannual variation of total abundance and biomass of zooplankton with mean individual weight of a zooplankter was analysed based on field data collected between 1957 and 2013.The dominating species in mesozooplankton were rotifers and copepods.Abundance and biomass estimates of zooplankton indicated the highest values during summer months (June: peak abundance; August: highest biomass).The dominating species during the peak abundance were rotifers and copepods; the biomass maximum was indicated by copepods (in June) and cladocerans (in July and August).When averaged over summers, the total zooplankton abundance was 156.2 ± 2.4 thousand ind/m 3 , biomass 62.9 ± 1.3 mgC/m 3 , and zooplankter individual weight 0.433 ± 0.004 µgC/ind.Our study showed that mean zooplankter weight and total zooplankton biomass correlated with the agespecific herring weight data.To conclude, the structure and stock size of the zooplankton community adequately indicated strong effects of zooplankton on fish size and growth.
Climate change is expected to profoundly affect both temperature and net precipitation, with implications for lake water level. We describe the design of a harmonized, simultaneous, cross- European mesocosm experiment to elucidate the effects of climate change on community structure, functioning, and metabolism in shallow lakes at low and high nutrient levels with contrasting depths (1 and 2 m). We used cylindrical (D = 1.2 m) tanks that were either 1.2 or 2.2 m high, each having a 10-cm sediment layer. We inoculated the mesocosms with a mixed sample of sediment and plankton from lakes with contrasting nutrient concentrations and added macrophytes and planktivorous fish. Sediment was pre-equilibrated to the required experimental nutrient concentration. During the experiment the water level decreased with increasing temperature (up to 90 cm in the Mediterranean mesocosms) while conductivity increased. The average chlorophyll a concentration increased with temperature in the deep mesocosms but was more variable in the shallow mesocosms. Macrophyte
Riparian soils are affected by both natural and anthropogenic disturbances occurring in the water bodies and on the catchment area.These riparian areas are also rich in microhabitats and therefore host various soil biota, including diatoms.Diatoms are known for their bioindication abilities in water and could potentially be used in that context in the riparian zone.Therefore the possibility of riparian soil diatoms acting as indicators of both terrestrial and aquatic disturbances is worth discussion.We analysed diatom community structure and their variability between different study areas and sites.We also quantified diatom species diversity and richness and evenness of the riparian topsoils.Possible effects of various anthropogenic disturbances on diatom communities, alkaline air pollution, and the effects of mining waters pumped into the area were studied in northeastern Estonia.These results were compared with results from an area with low human influence in south-eastern Estonia.Additionally, we evaluated the potential of diatoms as indicators of various anthropogenic disturbance levels and a water contamination gradient based on sulphate concentrations.Community parameters, including species richness, diversity, and evenness, indicated some differences between the studied communities both when the separate study sites and distinguishable anthropogenic disturbance levels were compared.Diatom assemblages also showed moderate variability between the study sites, which could be influenced by variable moisture conditions, variable organic matter content, and the trophic level of the water body.Despite the variable levels of human influence the two compared areas shared about 51.4% of the species.Our findings show that the diatom community composition of riparian soils could potentially indicate anthropogenic disturbance levels, especially through the abundance, absence, or presence of specific species (e.g.Hantzschia amphioxys, Fragilaria zeilleri var.
Studies of the properties of soil organic matter are essential for understanding the humification reactions and soil diagenesis processes. The aim of this study is to analyse properties of peat and peat humic acids as well as factors influencing their variability. Humic acids isolated from an ombrotrophic bog peat profile were used as study objects. Relations among peat age, decomposition and humification degree, botanical composition, and properties of peat humic acids (elemental, functional composition, spectral characteristics) were studied. The variability of peat properties was found to be less significant than the differences in the properties of peat-forming living matter, which indicates the dominant impact of humification processes on the properties of peat. Correspondingly, the composition of peat humic acids was insignificantly affected by the differences in the composition of the precursor living organic material.
Re-vegetation of extracted peatlands is a slow and sporadic process. The aim of our study was to clarify whether this process is affected by the distance from vegetated areas and propagules arrival or by the conditions for propagules germination and plant growth. Our analysis is based on three extracted peatlands in Estonia, abandoned 26-31 years ago. In all study areas vegetation was analysed on the gradient from a neighbouring vegetated area towards the central part of the peatland. In addition, peat blocks were collected from the marginal and central parts of the peatlands, held in favourable moisture conditions for seed germination in a greenhouse, and half of them were fertilized with a complex fertilizer. Our study showed the species pool to be present everywhere on abandoned extracted peatlands, but the germination was influenced by different factors such as water table, peat chemistry, etc. The species richness on extracted peatlands was higher close to the neighbouring vegetated areas and decreased towards the central part of the peatland, but for the peat blocks held in the greenhouse, the number of species was higher for the blocks collected from the central parts of the peatlands. The proximity of the vegetated area did not increase the number of species developed in the greenhouse whereas higher moisture and temperature conditions initiated the growth of many additional species not found on the extracted peatlands. Our study demonstrated that fertilization with a complex fertilizer did not have an overall influence on the number of species, indicating that the re-vegetation of extracted peatlands is more controlled by moisture conditions than by the availability of nutrients or propagules arrival.
