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Unusual stable morphotype of acroperus harpae (Baird, 1834) from Lake Mỳvatn, Iceland (Cladocera: Anomopoda: Chydoridae) revealed by palaeolimnological studies

Siney A Y, Zawisza E, Einarsson A

Studia Quaternaria

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2012

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Vol. 29

3--7

EN

A new unusual morphotype of Acroperus harpae (Baird, 1834) was found in Lake Mỳvatn and its neighbouring Lake Budlungaflói in Iceland. This form, A. harpae f. multidentata is characterized by a very large head keel and by 5-9 denticles on the posterovental angle of the valves instead of 1-3 common for A. harpae. The new form did not differ from typical A. harpae in the morphology of the postabdomen, head pores or any appendages. A study of Lake Mỳvatn sediments reveled that this form existed in the lake for at least two thousand years.

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Description of the subfossil head shield of Alona protzi hartwig 1900 (anomopoda, chydoridae) and the environmental characteristics of its finding sites

Bjerring R., Nykanen M., Sarmaja-Korjonen K., Sinev A., Jensen K., Nevalainen L., Szeroczyńska K., Zawisza E.

Studia Quaternaria

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2008

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Vol. 25

47-53

EN

This paper gives a description of the head shield of Alona protzi, a rare species of Cladocera (water fleas) whose separated head shield has not yet been described in detail. Subfossil head shields of A. protzi were found in sediment cores taken from lakes in Denmark, Sweden, Finland, Estonia and Poland. Despite the rarity of the species this suggests a wide distribution of A. protzi in northern Europe. The ecology of A. protzi is poorly known. The environmental spectrum of the finding sites was wide and ranged from relatively nutrient poor clear water lakes to eutrophic turbid water lakes, indicating that A. protzi is not narrowly restricted. Most of the lakes were, however, meso-eutrophic with neutral to high pH, and with a relatively low abundance of submerged macrophytes. However, we cannot exclude the possibility that A. protzi mainly lives in groundwater and is only occasionally transported into lakes.

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Reconstruction of the trophic development of lake krakower obersee (mecklenburg, germany) by means of sediment- diatom- and pollen-analysis

Hubener T., Dorfler W.

Studia Quaternaria

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2004

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Vol. 21

101-108

EN

Changes in composition of diatom (Bacillariophyceae) communities and pollen content were analyzed in two cores from the lake Krakower See, Mecklenburg-Vorpommern, Northern Germany. Based on the pollen stratigraphy, a time-depth-curve was built that allowed an estimate of the rate of sedimentation. The pollen curves, especially those of settlement indicators, showed the human influence in the surrounding area. Diatom assemblages clearly indicated that human activities had influenced not only the terrestrial vegetation but also the water body of the lake and it's trophic conditions. From a natural oligo- to mesotrophic lake that had small oscillations in prehistoric times it switched relatively fast into an eutrophic one around 700 years ago. This radical change in the trophic status was an effect of both damming up for mills in the 13th century and increasing settlement activities around the lake.

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Paleolimnological study based on ostracods (crustacea) in late-glacial and holocene deposits of Lake Krakower See (Mecklenburg-Vorpommern, NE Germany)

Finn A.

Studia Quaternaria

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2004

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Vol. 21

109-115

EN

Two cores were taken from the southern lake basin to record the lake development from the Allerod until today. The Late Glacial and Holocene deposits of Lake Krakower See (Mecklenburg-Vorpommern, NE Germany) revealed changing water levels of the lake. Subfossil freshwater ostracods were used to interpret signals in terms of hydrological changes, eutrophication and temperature. A diverse ostracod fauna of 24 species was found in the examined sedyment samples. For the first time the development of Late-Glacial and Post-Glacial freshwater ostracod assemblage could be recorded in the study area.

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How did the nutrient concentrations change in northeastern German lowland rivers during the last four millennia? - a paleolimnological study of floodplain sediments

Schonfelder I., Steinberg C. E. W.

Studia Quaternaria

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2004

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Vol. 21

129-138

EN

This study focuses on the feasibility of floodplain sediments and fluvial sediments in paleomeanders and ox-bows of two lowland rivers (River Havel, River Spree, Brandenburg State, Germany) as archives for quantitative paleolimnological reconstructions and potential basis of future river management strategies. The results presented provide a mean to differentiate between the natural and cultural eutrophication of rivers. Available transfer functions of littoral diatom assemblages in 84 Brandenburg lakes and river sites, and total phosphorus (TP) and total inorganic nitrogen (TN) were used to infer nutrient changes in the Rivers Havel and Spree since the last 4,000 years. In the River Spree near Platkow, fossil diatoms indicated moderate eutrophic TP- and TN-concentrations between 1300 and 1850 AD (TP: 36 mg dm-3, TN: 1,000 mg dm-3). During this time period, the human impact on the nutrient status of the River Spree was more or less indirect via increases of runoff from the catchment as a result of deforestation. In the second lowland river, the lower River Havel, diatom inferred TP-concentrations were 80 žg dm-3 in the late Subboreal (2,000 to 500 BC). That means that the natural diatom flora of this river was eutrophic; mesotrophic conditions even in times without intensive land use did not occur. Furthermore, the fossil diatom flora revealed a potential nitrogen limitation during summer times (till 1400 AD: TN 1,600 to 1,700 mg dm-3). Anthropogenic eutrophication impact on the River Havel can be detected since approximately 800 year ago. The diatom-inferred nitrogen/phosphorus-relation highlighted different trends in eutrophication history within the study area. Without human activities the ratio of both nutrient components was relatively constant. Anthropogenic changes in the catchment area led to a declining TN/TP ratio in the last 1,000 years with changes in algal communities, such as increases of nuisance cyanobacteria blooms in the last decades.