Differences in Ice Cover in the Anthropogenic Reservoir of Pławniowice in the Years 1986–2012

The article presents changes in the thickness and duration of the ice cover found in the restored anthropogenic water reservoir of Pławniowice. It also defines the role the ice cover plays in the formation of the reservoir limnological cycle. Characteristic and significant changeability of the ice cover thickness and duration was observed. The changes in the ice cover demonstrate that they are cyclical but not regular. The ice cover did not always form in the analyzed period. It happened twice, i.e. in 1988 and 2007 (a gap of 20 years). The longest lake freezing period lasted 119 days. Changes in the ice cover duration also show certain periodicity. The shortest periods occurred approx. every 7 years. Maximum values of the ice cover thickness ranged between 10 and 52 cm. There is a relation between the ice cover thickness and its duration period. The rate of increase in the ice cover thickness varied between 0.296 and 3.6 cm/d. The hypolimnion removal impact on the ice cover duration period and thickness was not observed. On the other hand, the ice cover duration period affects the spring circulation duration. Thus, it has an influence on the oxygen balance of the limnic ecosystem.

Regional weather survey on Byers Peninsula, Livingston Island, South Shetland Islands, Antarctica

In 2001 the LIMNOPOLAR Project was launched with the aim of addressing the suitability of freshwater ecosystems as useful sentinels of climate change. In this project, an automatic weather station was deployed on Byers Peninsula (Livingston Island, South Shetland Islands) near several freshwater ecosystems under research. Here the multi-year data recorded are presented and compared with meteorological time series from the observatories at the Spanish Juan Carlos I Station, Deception Island and Bellingshausen Station. Lake freezing and thawing periods and snow cover are also investigated. The main results indicate that Byers Peninsula is affected by the very cloudy and wet Antarctic maritime climate. Mean annual temperature is -2.8°C and summer mean temperatures are above freezing. The region shows moderate winds over the year and with moderate, mostly liquid precipitation during the summer. There is a significant linear relationship with meteorological records obtained from Juan Carlos I Station located on the east of Livingston Island. Correlations between meteorological data from both sites are high but with colder and much windier conditions on Byers Peninsula. Therefore, the usefulness and accuracy of meteorological records in the interpretation of ecosystem dynamics are presented.

Mortality Factors of Dalmatian Pelicans (Pelecanus crispus) Wintering in Macedonia, Greece

A survey of dead Dalmatian Pelicans (Pelecanus crispus) at Kerkini Lake, Greece, the major wintering site in Europe of this world-endangered species, was undertaken to investigate the causes of high mortality that occurred during 1991–93. In February 1991, 30% of the population wintering on the Lake (30 individuals) were found dead, the majority (85%) having died of natural causes. A loss of this magnitude does not reflect only locally or on the genetic stock of the species but is also a matter of grave concern relative to its conservation world-wide.Most mortality of the Pelicans coincided with subzero temperatures and the Lake freezing over — conditions that direct fish to deep waters, and make them unavailable to the Pelicans. Necropsies were carried out on the carcasses of 13 Pelicans, including stomach and gizzard, etc., contents' analysis, and gross pathological, bacteriological, toxicological, and parasitological, examinations. All the carcasses found at Lake Kerkini were dehydrated and emaciated. No food was found in the digestive system of the Pelicans, but there was a heavy parasite burden. Species of seven helminth genera were detected in the carcasses, three of them (Bolbophorus, Contracaecum, and Synhimantus) being reported for the first time in Greece. Contracaecum spp. in large numbers (up to 875 worms per bird), were found in the digestive system of all the carcasses. Most parasites were observed to penetrate the wall of the gizzard, causing haemorrhages and ulcers. No evidence of chlorinated hydrocarbon contamination or bacterial infection was found. Mycotic lesions were detected in the air-sacs of one Dalmatian Pelican, which may have contributed to the death of that particular individual in connection with the parasite burden.