The Late Quaternary lake history of Taro Co and three neighbouring lakes was investigated to reconstruct local hydrological conditions and the regional moisture availability. Ostracod-based water ...depth and habitat reconstructions combined with OSL and radiocarbon dating are performed to better understand the Taro Co lake system evolution during the Late Quaternary. A high-stand is observed at 36.1 ka before present which represents the highest lake level since then related to a wet stage and resulting in a merging of Taro Co and its neighbouring lakes Zabuye and Lagkor Co this time. The lake level then decreased and reached its minimum around 30 ka. After c. 20 ka, the lake rose above the present day level. A minor low-stand, with colder and drier conditions, is documented at 12.5 cal. ka BP. Taro Co Zabuye and Lagkor Co formed one large lake with a corresponding high-stand during the early Holocene (11.2–9.7 cal. ka BP). After this Holocene lake level maximum, all three lakes shrank, probably related to drier conditions, and Lagkor Co became separated from the Taro Co-Zabuye system at c.7 ka. Subsequently, the lake levels decreased further about 30 m and Taro Co began to separate from Zabuye Lake at around 3.5 ka. The accelerating lake-level decrease of Taro Co was interrupted by a short-term lake level rise after 2 ka BP, probably related to minor variations of the monsoonal components. A last minor high-stand occurred at about 0.8 ka before today and subsequently the lake level of Taro Co registers a slight increase in recent years.
•Late Quaternary lake level reconstructed for the Taro Co lake system, Tibetan Plateau.•Lake level reconstruction by combined dating and ostracod-based water depth•Late Pleistocene lake level high-stands are observed at 36.1, 18 and 12.5 ka BP.•Holocene maximum at 10.5 ka BP, shrinking thereafter due to drier conditions•Records from neighbouring basins shows synchronised climatic evolution.
Three species of North American freshwater catfishes (Ameiuridae), including Black Bullhead (Ameiurus melas), Brown Bullhead (A. nebulosus), and White Catfish (A. catus), were reported to have been ...introduced into Irish waters since the late 19th century. However, only isolated specimens of A. melas have been authenticated from two widely separated locations to date: Terenure College Lake, Dublin and Cork Lough, Cork City. During 2006, an unidentified Ictalurid catfish was reported to have been captured by an angler in an undisclosed tributary of the Erne catchment. The author examined two specimens of catfish in the collections of the National Museum of Ireland – Natural History which were obtained from Terenure College Lake during July 1889. Although both specimens were labelled as White Catfish, they proved to be A. melas, one of which was estimated to be 9 years of age. The age of the Terenure specimen suggests that they were probably introduced during the early 1880s, or were the progeny of an already established self-sustaining population introduced at an earlier date. All known records of North American catfishes in Irish waters and their potential invasiveness are reviewed.
The Laurentian Great Lakes are vast, spatially heterogeneous, and changing. Across these hydrologically linked basins, some conditions approach biogeochemical extremes for freshwater systems ...anywhere. Some of the biogeochemical processes operate over nearly as broad a range of temporal and spatial scales as is possible to observe in freshwater. What we know about the biogeochemistry of this system is strongly influenced by an intense focus on phosphorus loading, eutrophication, and partial recovery; therefore, some important biogeochemical processes are known in detail while others are scarcely described. These lakes serve as a life support system for tens of millions of people, and they generate trillions of dollars of economic activity. Many biogeochemical changes that have occurred have surprised us. Biogeochemistry affects how these lakes perform these functions and should be a higher research priority.
The biogeochemical functioning of the Great Lakes affects tens of millions of people and trillions of dollars of economy, but our knowledge of their biogeochemistry is fragmentary.
The history of environmental damage and recovery in the Great Lakes is long and includes many surprises.
Large lakes such as the Great Lakes combine characteristics of small lakes and the world's oceans, making them worthy objects of study to advance fundamental understanding.
The Great Lakes are understudied relative to their scale and importance.
1. Eutrophication constitutes a serious threat to many European lakes and many approaches have been used during the past 20-30 years to improve lake water quality. Results from the various lake ...restoration initiatives are diverse and the long-term effects are not well described. 2. In this study we evaluated data from more than 70 restoration projects conducted mainly in shallow, eutrophic lakes in Denmark and the Netherlands. Special focus was given to the removal of zooplanktivorous and benthivorous fish, by far the most common internal lake measure. 3. In more than half of the biomanipulation projects, Secchi depth increased and chlorophyll a decreased to less than 50% within the first few years. In some of the shallow lakes, total phosphorus and total nitrogen levels decreased considerably, indicating an increased retention or loss by denitrification. The strongest effects seemed to be obtained 4-6 years after the start of fish removal. 4. The long-term effect of restoration initiatives can only be described for a few lakes, but data from biomanipulated lakes indicate a return to a turbid state within 10 years or less in most cases. One of reasons for the lack of long-term effects may be internal phosphorus loading from a mobile pool accumulated in the sediment. 5. Synthesis and applications. Lake restoration, and in particular fish removal in shallow eutrophic lakes, has been widely used in Denmark and the Netherlands, where it has had marked effects on lake water quality in many lakes. Long-term effects (> 8-10 years) are less obvious and a return to turbid conditions is often seen unless fish removal is repeated. Insufficient external loading reduction, internal phosphorus loading and absence of stable submerged macrophyte communities to stabilize the clear-water state are the most probable causes for this relapse to earlier conditions.
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