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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Periphyton 2
Regional-scale variation in diatom-water chemistry relationships in the eastern U.S.
D.F. Charles, F.W. Acker, D.D. Hart, and C.W. Reimer. Patrick Center for Environmental Research, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103
We analyzed ANSP data collected between 1951 and 1991 from 116 sites on 47 fourth to tenth order rivers from Maine to Texas to determine how ecological relationships of benthic diatoms varied over large and intermediate regional scales. Multivariate analyses put diatom assemblages into four main groups. Group membership correlates similarly with both geographic region and water chemistry: 1) northeastern U.S. rivers with lower alkalinity and hardness, and pH 6.5-7.8; 2) dilute southeastern coastal plain rivers with the lowest average pH (5.5-7.3); 3) rivers west of the Appalachian Mountains, generally having pH >7.5, but with relatively low chloride; and 4) Gulf Coast rivers with the highest chloride (>100 mg/L), hardness (>250 mg/L), and pH of all the groups. Concentrations of major ions, pH, alkalinity, hardness, and conductivity explained most of the variation among diatom assemblages, based on DCCA. Factors related to water quality problems, such as BOD, phosphorus, dissolved oxygen, ammonia, and turbidity explained much less variability on a large scale, but had greater importance within the four groups. Diatom taxa abundance-weighted-mean values for several water chemistry characteristics varied among the four regions, often by large amounts, and in proportion to the average measured values for each region.
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