Exploitation and destabilization of a warm, freshwater ecosystem through engineered hydrological change

Exploitation of freshwater resources is having catastrophic effects on the ecological dynamics, stability, and quality of those water resources on a global scale, especially in arid and semiarid regions. Lake Kinneret, Israel (the Biblical Sea of Galilee), the only major natural freshwater lake in the Middle East, has been transformed functionally into a reservoir over the course of ∼70 years of hydrological alterations aimed mostly at producing electrical power and increasing domestic and agricultural water supply. Historical changes in lake chemistry and biology were reconstructed using analysis of sedimentary nutrient content, stable and radioisotope composition, biochemical and morphological fossils from algae, remains of aquatic invertebrates, and chemical indices of past light regimes. Together, these paleolimnological analyses of the lake's bottom sediments revealed that this transformation has been accompanied by acceleration in the rate of eutrophication, as indicated by increased accumulation rates of phosphorus, nitrogen, organic matter, phytoplankton and bacterial pigments, and remains of phytoplankton and zooplankton. Substantial increases in these indices of eutrophication coincide with periods of increased water‐level fluctuations and drainage of a major upstream wetland in the early to middle 20th century and suggest that management of the lake for increased water supply has degraded water quality to the point that ecosystem stability and sustainability are threatened. Such destabilization may be a model for eutrophication of freshwater lakes in other arid regions of the world in which management emphasizes water quantity over quality.Peer reviewedZoolog

Gender differences in conversation topics, 1922–1990

Gender differences in conversation topics were first systematically studied in 1922 by Henry Moore, who theorized that the gender differences in topic choice he observed in a field observation study would persist over time, as they were manifestations of men's and women's “original natures.” In this paper, I report a 1990 replication of Moore's study, in which similar but smaller gender differences in topic choice are found. In order to explore further the apparent trend toward smaller gender differences, reports of quantitative observation studies conducted between 1922 and 1990 are examined. Other explanations besides change over time—such as variations in conversation setting and audience, target populations, and researcher's intentions—may account for the decline in gender differences in topic choice. Social influences are seen more clearly in the discourse about gender differences in conversation than in gender differences in conversation topics themselves.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45599/1/11199_2004_Article_BF00289744.pd