Biostratigraphy of Lake Spitaalijärvi: an ultraoligotrophic small lake in Lauhanvuori,western Finland

The Early and Middle Flandrian geological development and paleolimnology of Lake Spitaalijärvi was studied using pollen, diatom and cladoceran analysis and ¹⁴C dating. Spitaalijärvi was isolated from the Ancylus Lake about 9000 B.P., at which time birch and pine and plants typical of open habitat communities grew on the solitary island. The rational limits for Alnus and Picea were ca. 8300 B.P. and 3700 B.P., respectively. During the first few hundred years after isolation Spitaalijärvi was probably fairly eutrophic, with a low water level. Water level began to rise before the Alnus rise (A°) and the lake became oligotrophic. After another transgression, which started before the Picea rise (P°), Tabellaria binalis and Semiorbis hemicyclus appear in the diatom stratigraphy indicating ultra-oligotrophic conditions. The main reason for the ultra-oligotrophy of Lake Spitaalijärvi is the character of the parent material in the catchment, consisting of glacial and littoral deposits derived from the local quartz sandstone of highly siliceous nature.     

Recent stratigraphy and accumulation of sediment in the deep,oligotrophic Lake Pääjärvi in South Finland

Laminated sediment is deposited in the deep areas (> 30 m) of Lake Pääjärvi. In the diatom microstratigraphy a regular alteration of planktonic and littoral floras, which goes in pace with the visual structure, reflects the yearly cycle of sedimentation. Considerable variation in sedimentation was found to have occurred during the past two decades. A sequence, dated to the early 1960's, in which the organic content was exceptionally high, could be identified in the sediment at 6–14 cm depth even in shallower areas where laminations are not formed. This level was used as a marker horizon when determining the recent distribution of sediment by means of 19 cores taken from different parts of the lake. The average annual sediment accumulation in the profundal zone of the lake is 340 g m^?2a^?1 dry weight, of which 25 g m^?2 a^?1 (1100 kJ m^?2 a^?1) is organic carbon.     

Eutrophication and recovery of Lake Vesijärvi (south Finland): Diatom frustules in varved sediments over a 30-year period

Lake Vesijärvi was loaded by sewage from the City of Lahti for 60 years until 1976 when the discharge was diverted. Paleolimnological analyses of the varved bottom sediment indicate that the sedimentation rate within the Enonselka basin, the most eutrophic part of the lake, has been as high as 2 cm yr^–1, and total phosphorus accumulation was 20–40 g P m^–2 yr^–1, during the last 20 years. Within the less eutrophic Laitialanselkä basin, the sedimentation rate did not exceed 1 cm yr^–1, and the formation of varved sediment only began at the end of the 1960's, i.e. about 10 years later than in Enonselkä.Planktonic diatom production was highest in the Enonselka basin. The most abundant diatoms in the sediment between 1970–1985 were Asterionella formosa, Aulacoseira islandica and Stephanodiscus spp. Fragilaria crotonensis and Tabellaria fenestrata had low abundances in the middle of the 1970's but increased again at the end of the 1970's. Asterionella formosa and Diatoma elongatum reached their maxima between 1979–1984 when the hypolimnion of the Enonselk/:a basin was aerated artificially. In the Laitialanselkä basin, the production of planktonic diatoms has been lower and the species composition of the diatom community differed from that in Enonselkä. However, at the end of 1980's the total accumulation of diatoms in Laitialanselkä approached levels which were observed at the end of 1950's in Enonselkä, prior to the rapid eutrophication period.The production and thereby the sedimentation of diatoms has decreased towards the end of the 1980's in Enonselkä, indicating reduced nutrient availability in the lake water. This reduction was due to the decreased external loading of phosphorus as well as to the decreased release of phosphorus from the sediment as a result of improved oxygen balance in the hypolimnion.     

Sysmäjärvi — a lake polluted by mining waste-water

Lake Sysmäjärvi is located inside the municipal boundary of Outokumpu in North Karelia, Finland. Since 1928 metalliferous, and at a later stage highly acid waste-water, has been discharged into the lake. Neutralization of the lake water by liming was introduced, and by the end of 1966 the pH of the water had become neutral to alkaline. Two sediment cores (0.5 m and 5 m long, respectively) were analyzed for pollen, diatoms, loss-on-ignition, organic carbon, Fe, Cu, Ni, Pb, Zn and Hg. The maximum concentrations of organic matter and heavy metal content occur 30 cm below the sediment surface. Evidence of the liming and of accelerated eutrophication appear close to the surface of the sediment (0–10 cm), indicated by an increase in Nitzschia plana.     

Multiple asexual reproduction of Asterionella formosa Hass. from Lake Baikal and Angara reservoirs

The living plankton diatom Asterionella formosa from Lake Baikal and the Irkutsk Water Reservoir was studied using light microscopy. New facts were obtained which provide evidence of the occurrence of multiple asexual reproduction of Asterionella formosa.     

Das Sediment des Kummerower Sees. Untersuchungen des Chemismus und der Diatomeenflora

The Sediment of Lake Kummerow. Investigations on the Chemism and the Diatom Flora The paper deals with the distribution of chemical parameters and of diatoms in the deposits of the eutrophic Lake Kummerow (GDR), produced during about the last 3500 years. The sediment consists of a calcareous gyttja with a very low content of sand and clay. The results indicate a relatively constant trophic state of the lake in former times and an increased production within the last five centuries. Stephanodiscus astraea and its variety minutula is by far the most constant diatom species; in the uppermost parts of the sediment small sized planctonic taxa are increasing, in the main Stephanodiscus hantzschii var. pusillus, Melosira granulata var. angustissima, Asterionella formosa and Synedra acus var. angustissima and var. radians.     

Late Quaternary diatoms in the sediments of Przedni Staw Lake (Polish Tatra Mountains)

The paper presents a diatom succession in the Late Glacial and Holocene sediments of the Przedni Staw lake in the Pie Stawów Polskich Valley High Tatra Mts. Ten diatom phases are distinguished and presented against a pollen diagram from the analyzed core showing continuous sedimentation from the Oldest Dryas to the Subatlantic period. The diatom flora in the Late Glacial sediments is predominantly littoral — Fragilaria, Navicula, Nitzschia, Diploneis, Pinnularia and Amphora species. The Holocene sediments enclose more abundant planktonic species such as Cyclotella quadriiuncta, Asterionella formosa and Melosira distans.     

Resource requirements of four freshwater diatom taxa determined by in situ growth bioassays using natural populations from alpine lakes

We performed a series of in situ batch culture experiments to assess the resource requirements of common diatom taxa in alpine lakes of the central Rocky Mountains of North America. While physiological data are available on the resource requirements of some of these taxa, it is unclear whether intraspecific generalizations can be made across aquatic systems due to the potential development of ecotypes. In these experiments, we used amended lake water for a culture medium and natural diatom populations. Growth kinetics were determined for Asterionella formosa Hassall, Fragilaria crotonensis Kitton, Staurosirella pinnata (Ehr.) Williams and Round and Tetracyclus glans (Ehr.) Mills. Staurosirella pinnata, a historically abundant alpine diatom, had very low N and P requirements. Asterionella formosa and F. crotonensis, generally considered meso- or eutrophic species, exhibited low P requirements if N and Si were in moderate supply. Tetracyclus glans had the highest Si requirement. These experiments reveal that the recent changes in diatom community structure in these alpine lakes may be driven by changes in nutrient supply. We suggest that local diatom taxa and a natural culturing medium should be used to obtain more representative algal physiological data from a particular area.     

Morphological variation of perch Perca fluviatilis in humic lakes: the effect of predator density,competition and prey abundance

Between and within‐lake variations in morphology of perch Perca fluviatilis were studied in four humic lakes in eastern Finland. Perca fluviatilis were more streamlined and smaller headed in a lake with the highest abundance of cyprinids, but lowest abundance of predators (Lake Tuopanjärvi), indicating adaptation to planktivorous feeding and low predator density. Highest bodied fish were found from a lake with the lowest cyprinid but highest predator abundance (Lake Koppelojärvi), which conversely indicates adaptation to more effective predator avoidance. Furthermore, the length of the paired fins was longest in Lake Kinnasjärvi and Lake Tuopanjärvi, where the abundance of benthic macroinvertebrates was lowest, suggesting selection for more effective benthivory. Clear morphological differences of P. fluviatilis between habitats were found only in Lake Kinnasjärvi, whereas in Lake Koppelojärvi and Lake Tuopanjärvi only the length of the paired fins differed and in Lake Harkkojärvi no differences were found. Taken together, these results suggest that inter and intrapopulation morphological differences are probably highly dependent on different biotic factors (i.e. predation risk, resource availability and competition). Spatial and temporal variations in these factors may have a great effect on body morphology of P. fluviatilis.     

Dust mediated transfer of phosphorus to alpine lake ecosystems of the Wind River Range,Wyoming, USA

Alpine lakes receive a large fraction of their nutrients from atmospheric sources and are consequently sensitive to variations in both the amount and chemistry of atmospheric deposition. In this study we explored the spatial changes in lake water chemistry and biology along a gradient of dust deposition in the Wind River Range, Wyoming. Regional differences were explored using the variation in bulk deposition, lake water, sediment, and bedrock geochemistry and catchment characteristics. Dust deposition rates in the Southwestern region averaged 3.34 g m^?2 year^?1, approximately three times higher than deposition rates in the Northwestern region (average 1.06 g m^?2 year^?1). Dust-P deposition rates ranged from 87 µg P m² day^?1 in the Northwestern region to 276 µg P m² day^?1 in the Southwestern region. Subalpine and alpine lakes in the Southwestern region had greater total phosphorus (TP) concentrations (5–13 µg L^?1) and greater sediment phosphorus (SP) concentrations (2–5 mg g^?1) than similar lakes elsewhere in the region (1–8 µg L^?1 TP, 0.5–2 mg g^?1 SP). Lake phosphorus concentrations were related to dissolved organic carbon (DOC) across vegetation gradients, but related to the percent of bare rock, catchment area to lake area, and catchment steepness across dust deposition gradients. Modern phytoplankton and zooplankton biomasses were two orders of magnitude greater in the Southwest than in the Northwest, and alpine lakes in the Southwest had a unique diatom species assemblage with relatively higher concentrations of Asterionella formosa, Pseudostaurosira pseudoconstruens, and Pseudostaurosira brevistriata. These results suggests that catchment controls on P export to lakes (i.e. DOC) are overridden in dominantly bare rock basins where poor soils cannot effectively retain dust deposited P.     

Diatom and chrysophycean cyst profiles in sediment cores from two linked but contrasting Welsh lakes

Llyn Padarn and Llyn Peris are linked by a small river, and although originally a single larger lake, the lakes now support contrasting algal communities. A study of the sequences of diatom remains and chrysophycean cysts present in long sediment cores has been carried out to assess the historical extent of the differences in these algae between the two lakes.

Investigations have included statistical analysis to determine the precision of counting sediment samples. The most efficient sampling and counting procedure, resulting in counts of acceptable precision, involved taking a single sample of sediment from a depth horizon, preparing two replicate slides and counting the entire area of each slide. A comparison of the variation in distribution of these siliceous algae in replicate sediment samples taken from the surface sediment with the variation in distribution down the long sediment core from Llyn Padarn showed that the vertical variation greatly exceeded the horizontal variation. Thus variation in diatom numbers down the sediment core reflects changes in the alga reaching the sediments rather than horizontal patchiness of distribution in the top most layers of sediment.

Studies of the sequences of diatoms and chrysophycean cysts were carried out on a 4·75 m core from Llyn Padarn and 2·1 m core from Llyn Peris representing c. 6000 years and c. 900 years of the two lakes respective history. From c. 6000 until c. 2200 years B.P., Llyn Padarn was an acid oligotrophic lake. It appears that about 2200 years B.P., Llyn Padarn became more enriched, Asterionella formosa was the most numerous diatom preserved in the sediment at this time. Reversion to oligotrophic conditions then occurred c. 2000 years B.P. The oldest material from the Peris sediment core was characterized by centric diatoms similar to those found in Padarn sediment dating from 2000 years B.P. to the surface of the Padarn core. Thus at this time, c. 900 years B.P., the algal communities in the two lakes were similar. Both lakes were oligotrophic. However, by 200 years B.P. the chemistry of the sediment core from Peris showed evidence of extensive copper and slate mining in the environment. At this time the species of siliceous algae preserved in the Peris core changed, and the current differences in algal communities in the two lakes appear to originate from this point in history.     

A study of phosphate limitation in Lake Maarsseveen: phosphate uptake kinetics versus bioassays

In order to assess possible phosphate limitation for the phytoplankton community of Lake Maarsseveen, two techniques (phosphate uptake experiments and bioassays) were employed simultaneously in February–March 1982. In that period the ambient phosphate concentration of the lake water was less than 0.03 µM P and the diatom Asterionella formosa constituted more than 90% of the phytoplankton population. The phosphate uptake experiments showed relatively high uptake capacities and low cell phosphorus contents for the natural phytoplankton community. This suggested phosphate limitation throughout the test period. The growth stimulation of the phytoplankton after enrichment with phosphate, however, only revealed phosphate limitation from the beginning of March and bioassays may therefore be regarded as a less sensitive method.     

The effect of tubificids and chironomids on particle redistribution of lake sediment

The effects of chironomid larvae,Chironomus plumosus, and tubificid worms,Limnodrilus spp., on particle redistribution in lake sediment were investigated experimentally using pots containing sediments obtained from Lake Suwa, Japan. The chironomids and tubificids increased the water content of surface sediment. The chironomid larvae had no effect on particle size distribution, while tubificids continuously accumulated small particles on the surface sediment through their selective feeding activity. Particles larger than 0.125 mm were buried at a sediment depth of 6 cm. In Lake Suwa, long diatom frustules, large plant debris and blue-green algal flocs were found to accumulate in the deeper layer of the lake sediment inhabited by tubificids at high density.     

东北镜泊湖硅藻对近现代气候变化和人类干扰的响应过程

全球气候变暖和人类活动加剧已经导致中国大量湖泊生态系统功能退化,而目前对东北地区湖泊生态系统变化的认识主要源于短期的监测。以东北镜泊湖为例,通过沉积记录和现代监测资料,分析一个多世纪以来以硅藻群落为代表的湖泊生态系统对气候波动和区域人类活动的响应过程。研究结果表明,在人类干扰显著加强之前,风力扰动是镜泊湖硅藻群落变化的一个重要因子,表现为Aulacoseira属种取代小型浮游种(Cyclostephanos、Stephanodiscus和Discostella)成为优势种。20世纪70年代以来,Asterionella formosa、Nitzschia palea和Fragilaria crotonensis的相继增加则反映了流域农业活动加剧、农业化肥大量施用以及污水排放导致的湖泊营养水平升高。温度的持续上升已经引起东北地区一些湖泊硅藻群落结构发生显著变化,但镜泊湖的硅藻记录却未显示这一气候变化的信号。考虑湖泊-流域形态和人类活动的不同,研究认为近几十年气候变化对镜泊湖硅藻群落结构的影响被强烈的人类干扰所掩盖而未显现出来。     

Sensitivity and responses of diatoms to climate warming in lakes heavily influenced by humans

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Sediment and phytoplankton records of the cyanobacterial genus Anabaena in boreal Lake Pyhäjärvi

Past occurrence and quantities of Anabaena cyanobacteria in Lake Pyhäjärvi, SW Finland, were investigated using sediment and phytoplankton records. A short sediment core covering the past 20 years was examined for Anabaena resting spores (akinetes) in order to assess the utility of akinetes as a paleolimnological proxy. Sedimentary akinetes confirmed the past existence of Anabaena in water, but did not show a direct correlation with the amount of Anabaena spp. in water samples. The amount of planktonic Anabaena spp. correlated with total phosphorus and nitrogen concentrations in Lake Pyhäjärvi, but the number of akinetes was considered to have a relationship with low nutrient concentrations and dominant bloom-forming cyanobacteria. Akinetes are probably suitable for low-resolution and long time scale paleolimnological investigations, where they provide information of past cyanobacteria that cannot be directly attained otherwise.     

Recovery of Historically Contaminated Watercourse Polluted by the Chemical Wood Industry: EROD Activity in Fish as Biomarker

Despite outstanding process alterations over decades, pulp- and paper-mill-contaminated sediments and continuing exposure by the effluents may still have effects on biota. In this study, ecotoxicological impacts in the boreal watercourse were analyzed by measuring ethoxyresorufin-O-deethylase (EROD) induction from wild fish populations and from experimentally exposed fish. In order to assess the role of sediment-borne chemicals, juvenile rainbow trout (Oncorhynchus mykiss) were exposed in the laboratory to the surface sediments of Lake Vatianjärvi and Southern Lake Saimaa, both watercourses impacted by the chemical wood industry for approximately a century. Hepatic EROD activity was also measured from roach (Rutilus rutilus) and perch (Perca fluviatilis) caught in Lake Vatianjärvi. Increased EROD activity was not observed in wild fish caught in Lake Vatianjärvi nor in rainbow trout exposed to the sediment of Lake Vatianjärvi, but it was observed in rainbow trout exposed to the sediment of Southern Lake Saimaa, probably explained by critically high concentrations of retene. The results of both the laboratory and field study indicate the absence of EROD-inducing compounds of the previously heavily contaminated Lake Vatianjärvi.     

Interactions of temperature and nutrient changes: effects on phytoplankton in the Piburger See (Tyrol,Austria)

1. Contemporary limnological and palaeolimnological data from Piburger See (Eastern Alps, Austria) allowed the reconstruction of its trophic state since the late 19th century and the assessment of changes in phytoplankton biomass and species composition in relation to selected environmental parameters. 2. A radiometrically dated sediment core from Piburger See was analysed for geochemical parameters, spheroidal carbonaceous particles (SCPs), bacterial and algal pigments, and diatoms. The low SCP sediment inventory assigns Piburger See to the ‘cleaner’ sites in Europe with respect to fossil‐fuel related air pollution. The sedimentary pigment and diatom record reveals moderate eutrophication during the 20th century, followed by a slow re‐oligotrophication since the mid‐1980s because of lake restoration starting in 1970. 3. Epilimnetic temperature for Piburger See was reconstructed using air temperature records. A pronounced temperature increase has been recorded during the mid‐1940s and since the late‐20th century, both promoting algal growth and changes in species composition (e.g. increase in centric diatoms and recent bloom of Asterionella formosa). 4. Climate scenarios project additional substantial warming for this mountain lake by the end of the 21st century which will be most pronounced during the growing season. The predicted change in lake water temperature and thermal dynamics represents a key driver for the trophic and ecological status of Piburger See in the future.     

The pH-independent effect of aluminum on cultures of phytoplankton from an acidic Wisconsin lake

Negative correlations between aluminum and planktonic algal abundance have been reported in acidic lakes. Natural assemblages of phytoplankton from a low-pH, low-Al lake (Franklin Lake, WI) were grown in semi-continuous cultures consisting of four treatments at pH 5.7 with 0.0, 50, 100, and 200 μg Al L⁻¹ and one treatment at pH 4.7 with no Al added. Asterionella ralfsii var. americana (a common diatom plankter in acidic lakes) grew well at both pH 4.7 and 5.7 when no Al was added but declined in all other treatments and so may be useful as an indicator of acidic, low monomeric-Al conditions. Other common plankters that showed this pattern included: Arthrodesmus indentatus, Ar. octocornus, Ar. quiriferus, Staurastrum arachne var. curvatum, S. longipes var. contractum, and S. pentacerum. Common taxa showing no toxic effects of Al were Dinobryon bavaricum, Peridinium limbatum, Stenokalyx monilifera, Elaktothrix sp. and Oedogonium sp. We hypothesize that metal toxicity as a pulse at spring snowmelt could dramatically change algal succession in moderately acidic lakes. The experimental results agreed well with field observations. These types of experiments are useful for predicting the responses of natural phytoplankton communities to increases in Al concentration.     

Studies on Gull Lake, Michigan

The seasonal and depth distribution of phytoplankton in Gull Lake, a moderately large, temperate, dimictic, recreational lake in southern Michigan, U.S.A., is described and discussed. Diatoms (Fragilaria crotonensis, Cyclotella michiganiana, Asterionella formosa, and Synechococcus) grow mainly in summer. Diatoms grew under the winter ice, and objections are lodged to the classic explanation of seasonal growth in temperate lakes, and to a recent hypothesis concerning the `paradox of the plankton'. Two raphe-bearing large diatom species were considered to be truly planktonic. A Synechococcus species was similar to that described previously only from Loch Leven.