Preface to the second edition. About the author. 1 There is no substitute for water. 2 How long is long?. 3 Sediments: an ecosystem's memory. 4 Retrieving the sedimentary archive and establishing the geochronological clock: collecting and dating sediment cores. 5 Reading the records stored in sediments: the present is a key to the past. 6 The paleolimnologist's Rosetta Stone: calibrating indicators to environmental variables using surface-sediment training sets. 7 Acidification: finding the "smoking gun". 8 Metals, technological development, and the environment. 9 Persistent organic pollutants: industrially synthesized chemicals "hopping" across the planet. 10 Mercury - "the metal that slipped away". 11 Eutrophication: the environmental consequences of over-fertilization. 12 Erosion: tracking the accelerated movement of material from land to water. 13 Species invasions, biomanipulations, and extirpations. 14 Greenhouse gas emissions and a changing atmosphere: tracking the effects of climatic change on water resources. 15 Ozone depletion, acid rain, and climatic warming: the problems of multiple stressors. 16 New problems, new challenges. 17 Paleolimnology: a window on the past, a key to our future. Glossary. References. Index

Pollution of Lakes and Rivers: A Paleoenvironmental Perspective

Effective management of aquatic resources requires long-term environmental data. However, because long-term observations are rarely available, indirect proxy methods must be used to substitute for these missing historical data sets. Major advances have been made in paleolimnology over the last decade, and many of these advances can be applied directly to integrated and cost-effective assessments of aquatic ecosystem health. This commentary uses the analogy of human health to argue that paleolimnological data provide information crucial to the decision-making processes of ecosystem managers.

Paleolimnology: an important tool for effective ecosystem management

Lake acidification became an environmental issue of international significance in the late 1960s and early 1970s when Scandinavian scientists claimed that ‘acid rain’ was the principal reason why f ...

Diatoms as indicators of surface water acidity

This chapter presents historical sulfur emission and deposition trends for regions in the United States and describes methods for assessing changes in water chemistry based on current spatial patterns, ion ratios and empirical models, and paleolimnological approaches. Reconstruction of sulfur deposition trends shows that current deposition to case study regions ranges from a factor of about 1 (Upper Midwest) to a factor of 10 (Catskills) above natural background. Deposition in the Northeast was high during the 1920s, 1940s, and 1960s, and has declined significantly since 1970. Sulfur deposition in the Southeast was low before the 1950s, but has increased significantly since then. Change in surface water chemistry can be assessed using simple empirical models, ion ratios, and analysis of current spatial patterns of chemistry. Many assumptions are implicit in these methods, so results should be interpreted carefully. Paleolimnological reconstructions of chemistry and biota from lake sediment records provide more direct evidence of past change than other approaches. Quantitative analyses of diatom and chrysophyte assemblages can be used to reconstruct past lakewater pH with a mean standard error of about ± 0.25 pH units.

Acidic Deposition and Aquatic Ecosystems

A statistically designed survey of lakes and streams in acid-sensitive areas of the United States, the National Surface Water Survey (NSWS), was used to identify the role of acidic deposition, relative to other factors, in causing acidic conditions in 1,181 lakes and 4,668 streams. Atmospheric deposition is the dominant source of acid anions in 75% of the acidic lakes and 47% of the acidic streams. Organic anions are dominant in one-fourth of the acidic lakes and streams; acidic mine drainage is the dominant acid source in 25% of the acidic streams. Other causes of acidic conditions are relatively unimportant on a regional scale. Nearly all the deposition-dominated acidic systems were found in six well-delineated subpopulations that represent about one-fourth of the NSWS lake population and one-third of the NSWS stream population.

https://science.sciencemag.org/content/sci/252/5009/1151.full.pdf

Acidic lakes and streams in the United States : the role of acidic deposition

Thirty-two northern Florida lakes were analyzed to construct a transfer function relating surface sediment diatom assemblages to lakewater pH (R2=0.89, s.e.=0.34). A paleoecological analysis of sediment cores from six of these lakes indicated that two have become more acidic in the last 50 years. The diatom inferred (DI) pH of L. Barco has declined between 0.56–0.82 in the 1900's and DI ANC (acid neutralizing capacity) by 28–46 μeq l-1. The DI pH of nearby L. Suggs has declined 0.91 pH units and its DI ANC by 19 μeq l-1. The timing of the inferred acidification is synchronous with known increases in emissions of sulfates and nitrates that are associated with acidic precipitation. Also, the increasing accumulation of substances related to emissions from the burning of fossil fuels (e.g., Pb, PAH) co-occurs with the lowering of DI pH in the sedimentary record. However, other processes may have accounted for or contributed to recent lake acidification. For instance, the drawdown of local water tables by human consumption may decrease the inseepage of ANC to seepage lakes. Such an effect would be synchronous with increasing depositions of sulfate. There is also clear evidence that Florida lakes are naturally acidic. Thus, paleoecological results indicate acidic deposition to be at certain contributor, but not necessarily the sole cause, of the recent further acidification of some naturally acidic Florida lakes.

P. Roger Sweets

Papers

Paleoecological investigations of recent lake acidification in northern Florida