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Lake Environments (lake + environment)
Selected AbstractsUsing bald eagles to indicate the health of the Great Lakes' environmentLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3 2002William W. Bowerman Abstract The bald eagle (Haliaeetus leucocephalus) is one of the most studied birds of North America, and a great amount of natural life-history information, including the response of various stressors on the eagles' ability to reproduce, are well known. In Michigan, the eagle has been chosen to track the trends of bioaccumulative compounds of concern across watersheds in the state. The state has been divided into major watersheds, and 20% of these are surveyed each year. A control area in northern Minnesota, Voyageurs National Park, is also sampled annually. We report here on the methods used, the preliminary results of the 1999 field season, and how differences in mercury concentrations varied over a 10-year period. Mercury in feathers of nestling eagles declined over time only in Lakes Michigan and Huron, but have not decreased among other subpopulations in Michigan. Concentrations of polychlorinated biphenyls (PCBs) and 4,4,-DDE in blood plasma from nestling eagles have declined over time for most subpopulations; however, they remain greater for breeding areas associated with the Great Lakes' food web. Sea eagles of the genus Haliaeetus are a good sentinel species to track trends in bioaccumulative compounds in aquatic systems. [source] A multi-proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA,JOURNAL OF QUATERNARY SCIENCE, Issue 8 2009David A. Grimley Abstract The Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1,km continuous exposure (,20,m vertically) of Quaternary fluvial and lacustrine deposits, inset within Eocene sediments and buried by thick loess. Fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations, with deposition between ca. 190,140,ka and 24, 18 14C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 24,22 14C ka BP), a relatively permanent shallow lake environment is indicated by ostracods, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier ,18O compositions suggest marsh-like conditions in a periodically drying lake. The surrounding uplands consisted of Picea,Pinus woodlands mixed with cool-temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14C ka BP, with loess and slopewash gradually infilling the former lake by 18 14C ka BP. Modern analogue analyses of ostracods and palaeontological evidence imply a full glacial climate similar to today's mixed-boreal zone in central Minnesota, USA, about 9°C cooler in mean annual temperature than present-day western Tennessee. Copyright © 2009 John Wiley & Sons, Ltd. [source] Evidence for a lacustrine faunal refuge in the Larsemann Hills, East Antarctica, during the Last Glacial MaximumJOURNAL OF BIOGEOGRAPHY, Issue 7 2006Louise Cromer Abstract Aim, There is no previous direct evidence for the occurrence of lacustrine refuges for invertebrate fauna in Antarctica spanning the Last Glacial Maximum (LGM). In the absence of verified LGM lacustrine refuges many species are believed to result from Holocene dispersal from sub-Antarctic islands and continents further north. If freshwater lake environments were present throughout the LGM, extant freshwater species may have been associated with Antarctica prior to this glacial period. This study looked at faunal microfossils in a sediment core from an Antarctic freshwater lake. This lake is unusual in that, unlike most Antarctic lakes, the sediment record extends to c. 130,000 yr bp, i.e. prior to the LGM. Location, Lake Reid, Larsemann Hills, East Antarctica (76°23, E; 69°23, S). Methods, Palaeofaunal communities in Lake Reid were identified through examination of faunal microfossils in a sediment core that extended to c. 130,000 yr bp. Results, Ephippia and mandibles from the cladoceran Daphniopsis studeri and loricae of the rotifer Notholca sp. were found at all depths in the sediment, indicating that these two species have been present in the lake for up to 130,000 years. Copepod mandibles were also present in the older section of the core, yet were absent from the most recent sediments, indicating extinction of this species from Lake Reid during the LGM. Main conclusion, The presence of D. studeri and Notholca sp. microfossils throughout the entire Lake Reid core is the first direct evidence of a glacial lacustrine refugium for invertebrate animals in Antarctica, and indicates the presence of a relict fauna on the Antarctic continent. [source] Vegetation communities of British lakes: a revised classification scheme for conservationAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2007Catherine Duigan Abstract 1.A revised classification scheme is described for standing waters in Britain, based on the TWINSPAN analysis of a dataset of aquatic plant records from 3447 lakes in England, Wales and Scotland, which is held by the Joint Nature Conservation Committee. 2.Separate ecological descriptions of 11 distinct lake groups (A,J) are presented with summary environmental data, macrophyte constancy tables and maps showing their distribution. These lake groups include small dystrophic waters dominated by Sphagnum spp.; large, acid, upland lakes supporting a diversity of plant species, including Juncus bulbosus, Littorella uniflora, Lobelia dortmanna and Myriophyllum alterniflorum; low-altitude, above-neutral lakes with a high diversity of plant species, characterized by the presence of Potamogeton spp., Chara spp. or water-lilies and other floating-leaved vegetation; and coastal, brackish lakes, with macroalgae. 3.The Plant Lake Ecotype Index (PLEX) is presented as an indicator of changing lake environments. PLEX scores reflecting the new classification scheme have been developed for individual plant species and lakes. Applications of the index are demonstrated. 4.There is discussion of possible applications of the data collected and the resultant classification, in the context of the Habitats Directive, the Water Framework Directive and other conservation requirements. © Crown copyright 2006. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] Petit-Lac (western Lake Geneva) environment and climate history from deglaciation to the present: a synthesisBOREAS, Issue 4 2005STEPHANIE GIRARDCLOS During the past decade, the presentation of seismic and sedimentological data has allowed reconstruction of the environment and climate history of the Petit-Lac (western Lake Geneva). Methods such as high-resolution seismics, sediment core analysis (macroscopic description, grain-size analysis, mineralogy) and palynology have been used to infer the changes in the lake's environment from deglaciation to the present. However, no final synthesis has been attempted to link this information in the development of a comprehensive evolution model of the Petit-Lac and its surrounding region. The Petit-Lac deglaciation occurred in three phases during the Rhône glacier retreat: the Geneva stage and the Coppet and Nyon re-advances. In the Versoix area, rivers developed just after the retreat of the Rhone glacier from the Nyon stage. The Nyon fan delta started at the end of the Bølling, and its lobe fluctuated in size and orientation in six phases from the Lateglacial to the present. The action of bottom currents (i.e. erosion, non-deposition surfaces) arising at the beginning of the Holocene indicates that the frequency and direction of strong wind regimes varied greatly. Lacustrine mass failures occurred at different time intervals: two between deglaciation and the end of the Oldest Dryas, two between the Bølling and the Younger Dryas, and four during the Holocene. From the Oldest Dryas to the Contemporary Epoch, the vegetation changed from a steppe to a climate-influenced forest, and finally to a mostly human-controlled forest. [source] | |||||||||||||