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WORKING DRAFT OF ARTICLE: LIMNOLOGY

Limnology (/lɪmˈnɒlədʒi/ lim-NOL-ə-jee; from Greek λίμνη, limne, "lake" and λόγος, logos, "knowledge"), 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 (running and standing waters, both fresh and saline, natural or man-made). This includes the study of lakes and ponds, rivers, springs, streams and wetlands. A more recent sub-discipline of limnology, termed landscape limnology, studies, manages, and conserves these aquatic ecosystems using a landscape perspective.

Limnology is closely related to aquatic ecology and hydrobiology, which study aquatic organisms in particular regard to their hydrological environment. Although limnology is sometimes equated with freshwater science, this is not necessarily correct since limnology also comprises the study of inland salt lakes.

History

The term limnology was coined by François-Alphonse Forel (1841–1912) who established the field with his studies of Lake Geneva. Interest in the discipline rapidly expanded, and in 1922 August Thienemann (a German zoologist) and Einar Naumann (a Swedish botanist) co-founded the International Society of Limnology (SIL, from Societas Internationalis Limnologiae). Forel's original definition of limnology, "the oceanography of lakes", was expanded to encompass the study of all inland waters, and influenced Benedykt Dybowski's work on Lake Baikal.

Prominent early American limnologists included G. Evelyn Hutchinson, Ed Deevey, E. A. Birge, and C. Juday.

Physical Properties

Physical properties of aquatic ecosystems are determined by a combination of heat, currents, waves and other seasonal distributions of environmental conditions. The morphometry of a body of water depends on the type of feature (such as a lake, river, stream, wetland, estuary etc.) the structure of the earth surrounding the body of water. Lakes for instance are classified based on the shoreline being wave-swept. River and stream system morphometry is driven by underlying geology of the area as well as the general velocity of the water. Another type of aquatic system which falls within the study of limnology is estuaries. Estuaries are bodies of water classified by the interaction of a river and the ocean or sea. Wetlands vary in size, shape, and pattern however the most common types, marshes, bogs and swamps, often fluctuate between containing shallow, freshwater and being dry depending on the time of year.

Light interactions

Light zonation is the concept of how the amount of sunlight penetration into water influences the structure of a body of water. These zones define various levels of productivity within an aquatic ecosystems such as a lake. For instance, the depth of the water column which sunlight is able to penetrate and where most plant life is able to grow is known as the photic or euphotic zone. The rest of the water column which is deeper and does not receive sufficient amounts of sunlight for plant growth is known as the aphotic zone. There are portions of the electromagnetic spectrum which is reflected when sunlight hits the surface of the water which is known as albedo.

Thermal stratification

Similar to light zonation, thermal stratification or thermal zonation is a way of grouping parts of the water body within an aquatic system based on how each layer has different temperature variations. The shallower the water, the more light is able to penetrate meaning that the water will be warmer. This relationship continues exponentially as you move down the water column, so the water will be warmest near the surface but progressively cooler as you move towards the bottom of the body of water. The amount of organic matter on the uppermost layer of the water (also referred to as turbid waters) will influence the temperature of the rest of the system because it will increase the amount of heat absorbed higher in the water column and less heat will make its way to the lower portions of the water.

Thermoclines

Thermoclines are another physical feature in lakes especially and are way of defining different layers of water in which the temperature drops a degree in temperature as you increase depth. 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 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.

Paleoclimate Proxies

Sediment Cores

My Portion

Chironomids

Jamila's Portion

History

Lake ontogeny

THIS IS AN EXISTING CONTRIBUTION TO THE ARTICLE

Most early paleolimnological studies focused especially on the biological productivity 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.

External links

• International Paleolimnology Association (IPA)
• Indiana University Biology Dept. Paleolimnology homepage
• Journal of Paleolimnology (JOPL)
• NOAA online Paleolimnology data collection

Sylerb 18:01, 16 May 2017 (UTC)

Draft of Article: Outline

1. Lake Ecosystem Background

• Physical Properties
• Chemical Properties
• Water Quality Measures

2. Paleo-Proxies

• Vegetation and Archabotony
• Relationship to Climate
• Field Methods (coring, charcoal and pollen analysis)
• What past data can tell us about present and future climate/ environmental change

Initial Sources to Review:

H.H. Birks H.J.B. Birks Multi-proxy studies in palaeolimnology Vegetation History and Archaeobotany, 15 (2006), pp. 235–251

H.J.B. Birks Numerical tools in palaeolimnology – progress, potentialities, and problemsJournal of Paleolimnology, 20 (1998), pp. 301–332

J.P. Smol Pollution of Lakes and Rivers – A Paleoenvironmental Perspective Blackwell, Oxford (2008)

Sylerb 06:41, 12 May 2017 (UTC)

UO Long Term Environmental Change: Article Assignment Selection

I plan to work with Jamila to add to the Paleolimnology page on Wikipedia for this course project. We will dividing up the sections we are planning on writing and I will be focusing on the physical and chemical processes which are involved in the study of limnology. In addition to giving background information regarding things like water quality parameters and physical characteristics of lake ecosystems, I will be discussing the relationship between these topics and climate. To take into consideration the "paleo" perspective of this topic I will discuss the ways in which paleo-proxies are used to understand these processes (both physical and chemical) and how it can be studied from past records.

Bibliography of Useful Sources: In progress!

Sylerb 21:34, 4 May 2017 (UTC)