Edyta Zawisza

The development history of Wigry Lake as shown by subfossil cladocera

The Development History of Wigry Lake as Shown by Subfossil Cladocera Environmental changes in Wigry Lake during the Late Glacial and Holocene were studied on the basis of subfossil Cladocera analysis. Cladocera are present in a long core WZS/03 (Słupiańska Bay), and a surface sediments. The sediment contains remains of twenty-seven species belonging to 5 families. Species composition of plankton and the variability in the frequency of specimens of Cladocera made possible to distinguish five phases of their development, which well correlated with palynological phases. The correlation proves that the biological development of Wigry Lake was determined mainly by climatic changes. During the history of the lake, planktonic forms were dominant and represented by Bosminidae. It indicates that the lake was (excluding the initial part) deep and oligo- or mesotrophic. The mesotrophic state has been noted during the Atlantic chronozone and temporary. Taking into consideration the size and the depth as well as the rare human population around the lake it can be stated that the trophy rise was the result of the warm climate. It is also possible that during the last few decades the natural and anthropogenic factors could add. Probably mild winters, warm and long summers, increased tourists number were partly responsible for changes of water state.

Cladocera Community Composition as a Function of Physicochemical and Morphological Parameters of Dystrophic Lakes in NE Poland

Cladocera are one of the most important freshwater biological indicators for a wide range of environmental variables. They show strong responses to several environmental factors (e.g., trophic state, water depth, temperature) and are very sensitive to changes in water pH. The main interest of this study was to evaluate the relationship between subfossil Cladocera community composition and environmental properties of dystrophic lakes (pH, water transparency, conductivity, dissolved oxygen, depth and area). We hypothesize that Cladocera species composition depends on a dystrophication index (HDI); thus, Cladocera assemblages change with the degree of dystrophication. For the study, we selected a group of dystrophic lakes located in Wigry National Park (WNP), NE Poland, where we found subfossil remains of 24 Cladocera species belonging to four families (Chydoridae, Bosminidae, Daphniidae, and Sididae). A non-metric multidimensional scaling (NMDS) was used to elaborate on the similarities among samples in cladoceran-community composition and structure. Statistical analyses showed that Cladocera assemblages in all the studied lakes were similar, and individual Cladocera species respond to the measured environmental parameters (e.g., pH, lake size and depth). Our results suggest that in dystrophic lakes, Cladocera community composition is an emerging characteristic of individual species responses to the environment.

Initial Time of Two High Altitude Crater Lakes (Nevado De Toluca, Central Mexico) Recorded in Subfossil Cladocera

Abstract The objective of this study was the recognition and reconstruction of the origin of two high altitude lakes and the ecological conditions of their early existence based on subfossil Cladocera and chemical analyses. The study focused on the oldest lacustrine sediments from Lake Sol and Lake Luna, located in the crater of Volcano Nevado de Toluca (Central Mexico). The Nevado de Toluca crater developed approximately 12 ka yr BP. According to the literature, the volcano was last active approximately 3.3 ka yr BP, and the lakes developed after that eruption. The remains of nine Cladocera species were found in the bottom sediments of both lakes. The most dominant taxa were two endemic littoral species: Alona manueli and Iliocryptus nevadensis. The total frequency of Cladocera specimens in both of the sediment cores was very low. No Cladocera remains were recorded in the sediment layer at depths between 123–103 m from Lake Luna. The results of the lithological and geochemical analyses showed that this sediment layer was composed of allochthonous material, probably originating from slid down from the volcanic cone. This was suggested by the content of silica (up to 13%), iron (up to 12%), and titanium (up to 4%). The Cladocera remains recorded in the bottom sediments suggested that both reservoirs developed as freshwater lakes at the beginning of the sedimentation. The calibrated radiocarbon dates obtained for the bottom samples were 4040 to 3990 yr BP for Lake Luna (129 cm) and 4485 to 4485 yr BP for Lake Sol (89 cm). The obtained ages were older than the dates of the last eruption, which occurred approximately 3300 yr BP. This result was likely related to the type of radiocarbon dated materials (charcoals).

Cenotes – lakes of the Yucatan Peninsula (Mexico)

Abstract Cenote lakes are natural sinkholes or depressions resulting from the collapse of limestone bedrock exposing the groundwater underneath. Thousands of such lakes are particularly encountered on the Yucatan Peninsula (Mexico). These lakes were of great significance for the Maya culture as important religious places and primary source of drinking water. They permitted the survival of Mayan communities through dry periods known as “Maya drought”. Most of the cenote lakes are large open water pools measuring tens of meters in diameter. The majority of cenotes are smaller sheliered sites. Their waiers are usually very clear and oligotrophic, originating from rain waier filtering slowly through the ground. The auihors visited and coliected zooplankion samples from eight cenotes in November 2013, namely: Ik-Kil, Samula, Zaci, X-Kekn, Actum Ha, Cristal, Sian Ka’an, and Chan Chemuxil (transect Merida-Tulum- Cancun). The analysed lakes differ considerably in morphological terms, varying from very deep to shallow. Some of them are under human impact (tourists). The water samples were anaiysed for zooplankton content, but the phytoplankton frequently occurring was also taken into account. The obtained results are largely varied, indicated big ecological verity among cenotes which depended on lake age, localization and morphometry. As showed our study Cladocera zooplankion was very rare and only present at several sites. Beiween the fauna community Copepoda and Ostracoda species were the most abundant. Phytoplankton were present in all studied lakes and it sees that played the central role in those ecosystems.