Paleolimnology
Encyclopedia
Paleolimnology is a scientific subdiscipline closely related to both limnology
and paleoecology
. Palaeolimnological studies are concerned with reconstructing the paleoenvironments of inland waters (lakes and streams
; freshwater
, brackish, or saline
) – and especially changes associated with such events as climatic change
, human impacts (e.g., eutrophication
, or acidification
), and internal ontogenic processes.
Paleolimnological studies are commonly based on meticulous analyses of sediment
cores, including the physical
, chemical
and mineralogical
properties of sediments, and diverse biological
records (e.g., fossil diatoms, cladocera
, ostracodes, molluscs, pollen
, pigments, or chironomids). One of the primary sources for recent paleolimnological research is the Journal of Paleolimnology.
of lakes, and the role of internal lake processes in directing lake development. Although Einar Naumann
had speculated that the productivity of lakes should gradually decrease due to leaching of catchment soils, August Thienemann
suggested that the reverse process likely occurred. Early midge records seemed to support Thienemann's view.
Hutchinson
& Wollack suggested that following an initial oligotrophic stage lakes would achieve and maintain a trophic equilibrium. They also stressed parallels between the early development of lake communities, and the sigmoid growth phase of animal communities - implying that the apparent early developmental processes in lakes were dominated by colonization effects, and lags due to the limited reproductive potential of the colonising organisms.
In a classic paper, Raymond Lindeman
outlined a hypothetical developmental sequence, with lakes progressively developing through oligotrophic, mesotrophic, and eutrophic stages, before senescing to a dystrophic
stage and filling completely with sediment. A climax forest community would eventually be established on the peaty fill of the former lake basin. These ideas were further elaborated by Ed Deevey
, who suggested that lake development was dominated by a process of morphometric eutrophication
. As the hypolimnion
of lakes gradually filled with sediments, oxygen
depletion would promote the release of iron-bound phosphorus
to the overlying water. This process of internal fertilization would stimulate biological productivity, further accelerating the in-filling process.
Deevey and Lindemann's ideas were widely, if uncritically, accepted. Although these ideas are still widely held by some limnologists, they were effectively refuted in 1957 by Deevey's student Daniel A. Livingstone
. Mel Whiteside also criticized Deevey and Lindemann's proposal, and palaeolimnologists now consider that a host of external factors are equally or more important as regulators of lake development and productivity. Indeed late-glacial climatic oscillations (e.g., the Younger Dryas
) appear to have been accompanied by parallel changes in productivity, illustrating that 1) lake development is not a unidirectional process, and 2) climatic change can have a profound effect on lake communities.
) on lake communities. Their studies reveal pronounced changes in the bottom fauna of North American and European lakes, a consequence of severe oxygen depletion in the eutrophied lakes.
From 1980 to 1990 the primary focus of paleolimnologists efforts shifted to understanding the role of human impacts (acid rain
) versus natural processes (e.g., soil leaching) as drivers of pH
change in northern lakes. The pH
-sensitivity of diatom
communities had been recognised since at least the 1930s, when Friedrich Hustedt
developed a classification for diatoms, based on their apparent pH preferences. Gunnar Nygaard
subsequently developed a series of diatom pH indices. By calibrating these indices to pH, Jouko Meriläinen introduced the first diatom-pH transfer function. Using diatom and chrysophyte fossil records, research groups led by Rick Battarbee (UK), Ingemar Renberg (Sweden), Don Charles (US), John Kingston (US), and John Smol (Canada) were able to clearly demonstrate that many northern lakes had rapidly acidified, in parallel with increased industry and emissions. Although lakes also showed a tendency to acidify slightly during the their early (late-glacial) history, the pH of most lakes had remained stable for several thousand years prior to their recent, anthropogenic acidification.
In recent years palaeolimnologists have recognised that climate is a dominant force in aquatic ecosystem processes, and have begun to use lacustrine records to reconstruct paleoclimates. Sensitive records of climate change have been developed from a variety of indicators including, for example, paleotemperature reconstructions derived from chironomid fossils, and palaeosalinity records inferred from diatoms.
Limnology
Limnology , also called freshwater science, is the study of inland waters. It is often regarded as a division of ecology or environmental science. It covers the biological, chemical, physical, geological, and other attributes of all inland waters...
and paleoecology
Paleoecology
Paleoecology uses data from fossils and subfossils to reconstruct the ecosystems of the past. It involves the study of fossil organisms and their associated remains, including their life cycle, living interactions, natural environment, and manner of death and burial to reconstruct the...
. Palaeolimnological studies are concerned with reconstructing the paleoenvironments of inland waters (lakes and streams
STREAMS
In computer networking, STREAMS is the native framework in Unix System V for implementing character devices.STREAMS was designed as a modular architecture for implementing full-duplex I/O between kernel or user space processes and device drivers. Its most frequent uses have been in developing...
; freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
, brackish, or saline
Saline water
Saline water is a general term for water that contains a significant concentration of dissolved salts . The concentration is usually expressed in parts per million of salt....
) – and especially changes associated with such events as climatic change
Climatic Change
Climatic Change is a scientific journal published by Springer Science+Business Media. It deals with the problems of climatic variability and change...
, human impacts (e.g., eutrophication
Eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
, or acidification
Acid rain
Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions . It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen...
), and internal ontogenic processes.
Paleolimnological studies are commonly based on meticulous analyses of sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
cores, including the physical
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
, chemical
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
and mineralogical
Mineralogy
Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...
properties of sediments, and diverse biological
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
records (e.g., fossil diatoms, cladocera
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
, ostracodes, molluscs, pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
, pigments, or chironomids). One of the primary sources for recent paleolimnological research is the Journal of Paleolimnology.
Lake ontogeny
Most early paleolimnological studies focused especially on the biological productivityProductivity (ecology)
In ecology, productivity or production refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface per unit time, for instance grams per square metre per day. The mass unit may relate to dry matter or to the mass of carbon generated...
of lakes, and the role of internal lake processes in directing lake development. Although Einar Naumann
Einar Naumann
Einar Christian Leonard Naumann was an assistant professor of botany and limnology at the University of Lund. Naumann worked during the summers at the Fishery Station in Aneboda , where he established a field laboratory of the Limnological Institute in Lund .In 1921 he suggested the establishment of...
had speculated that the productivity of lakes should gradually decrease due to leaching of catchment soils, August Thienemann
August Thienemann
August Friedrich Thienemann was a German limnologist, zoologist and ecologist. He was an associate Professor of Hydrobiology at the University of Kiel, and director of the former Hydrobiologische Anstalt der Kaiser-Wilhelm-Gesellschaft at Plön.A co-founder of Societas Internationalis...
suggested that the reverse process likely occurred. Early midge records seemed to support Thienemann's view.
Hutchinson
G. Evelyn Hutchinson
George Evelyn Hutchinson FRS was an Anglo-American zoologist known for his studies of freshwater lakes and considered the father of American limnology....
& Wollack suggested that following an initial oligotrophic stage lakes would achieve and maintain a trophic equilibrium. They also stressed parallels between the early development of lake communities, and the sigmoid growth phase of animal communities - implying that the apparent early developmental processes in lakes were dominated by colonization effects, and lags due to the limited reproductive potential of the colonising organisms.
In a classic paper, Raymond Lindeman
Raymond Lindeman
Raymond Laurel Lindeman was an ecologist whose graduate research is often credited with being a seminal study in field of ecosystem ecology...
outlined a hypothetical developmental sequence, with lakes progressively developing through oligotrophic, mesotrophic, and eutrophic stages, before senescing to a dystrophic
Dystrophic lake
Dystrophic lake refers to lakes with brown- or tea-coloured waters, the colour being the result of high concentrations of humic substances and organic acids suspended in the water. Because the term has long been misused in the literature, these lakes are better referred to as humic lakes...
stage and filling completely with sediment. A climax forest community would eventually be established on the peaty fill of the former lake basin. These ideas were further elaborated by Ed Deevey
Edward Smith Deevey, Jr.
Edward Smith Deevey, Jr. , born in Albany, New York, was a prominent American ecologist and paleolimnologist, and an early protégé of G. Evelyn Hutchinson at Yale University...
, who suggested that lake development was dominated by a process of morphometric eutrophication
Eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
. As the hypolimnion
Hypolimnion
The hypolimnion is the dense, bottom layer of water in a thermally-stratified lake. It is the layer that lies below the thermocline.Typically the hypolimnion is the coldest layer of a lake in summer, and the warmest layer during winter...
of lakes gradually filled with sediments, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
depletion would promote the release of iron-bound phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
to the overlying water. This process of internal fertilization would stimulate biological productivity, further accelerating the in-filling process.
Deevey and Lindemann's ideas were widely, if uncritically, accepted. Although these ideas are still widely held by some limnologists, they were effectively refuted in 1957 by Deevey's student Daniel A. Livingstone
Daniel A. Livingstone
Daniel A. Livingstone is the James B Duke Professor Emeritus and Research Professor, in the Department of Biology at Duke University, Durham, North Carolina...
. Mel Whiteside also criticized Deevey and Lindemann's proposal, and palaeolimnologists now consider that a host of external factors are equally or more important as regulators of lake development and productivity. Indeed late-glacial climatic oscillations (e.g., the Younger Dryas
Younger Dryas
The Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief period of cold climatic conditions and drought between approximately 12.8 and 11.5 ka BP, or 12,800 and 11,500 years before present...
) appear to have been accompanied by parallel changes in productivity, illustrating that 1) lake development is not a unidirectional process, and 2) climatic change can have a profound effect on lake communities.
Anthropogenic eutrophication, acidification and climatic change
Interest in paleolimnology eventually shifted from esoteric questions of lake ontogeny to applied investigations of human impact. Torgny Wiederholm and Bill Warwick, for example, used chironomid fossils to assess the impacts of increased nutrient loading (anthropogenic eutrophicationEutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
) on lake communities. Their studies reveal pronounced changes in the bottom fauna of North American and European lakes, a consequence of severe oxygen depletion in the eutrophied lakes.
From 1980 to 1990 the primary focus of paleolimnologists efforts shifted to understanding the role of human impacts (acid rain
Acid rain
Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions . It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen...
) versus natural processes (e.g., soil leaching) as drivers of pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
change in northern lakes. The pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
-sensitivity of diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
communities had been recognised since at least the 1930s, when Friedrich Hustedt
Friedrich Hustedt
Friedrich Hustedt was a German teacher and botanist, best known for his diatom systematics research.He was born and grew up in Bremen, Germany. He taught school for 32 years, in 1924 becoming the head teacher of the school at Hauffstraße in Bremen...
developed a classification for diatoms, based on their apparent pH preferences. Gunnar Nygaard
Gunnar Nygaard
Gunnar Nygård was a Danish phycologist, and a leading authority on the ecology and taxonomy of Danish phytoplankton. Nygaard completed his Masters at University of Copenhagen, initially working at the Freshwater Biological Laboratory in Hillerød as a research stipendiary...
subsequently developed a series of diatom pH indices. By calibrating these indices to pH, Jouko Meriläinen introduced the first diatom-pH transfer function. Using diatom and chrysophyte fossil records, research groups led by Rick Battarbee (UK), Ingemar Renberg (Sweden), Don Charles (US), John Kingston (US), and John Smol (Canada) were able to clearly demonstrate that many northern lakes had rapidly acidified, in parallel with increased industry and emissions. Although lakes also showed a tendency to acidify slightly during the their early (late-glacial) history, the pH of most lakes had remained stable for several thousand years prior to their recent, anthropogenic acidification.
In recent years palaeolimnologists have recognised that climate is a dominant force in aquatic ecosystem processes, and have begun to use lacustrine records to reconstruct paleoclimates. Sensitive records of climate change have been developed from a variety of indicators including, for example, paleotemperature reconstructions derived from chironomid fossils, and palaeosalinity records inferred from diatoms.