ZOO401 Official Handouts

Topic No.1

Introduction to Limnology

Freshwater systems – lakes, wetlands, rivers and streams, have been critical to the establishment of civilizations throughout human history. From ancient times, civilizations have been established based on their proximity to water. Water bodies are essential to humans not only for drinking but also for transportation, agriculture, energy production, industry and waste disposal. Contaminated runoff from expanding urban and agricultural areas, airborne pollutants and hydrologic modifications such as drainage of wetlands are just few of the many factors that continue to degrade surface waters. Determining which of these factors has the most significant influence on the quality of a water body requires knowledge about the interaction of the water body with its watershed and how the various inputs affect its physical, chemical and biological characteristics. One of the critical sciences required to understand these aquatic ecosystem interactions is called limnology.

The term Limnology was coined by Francois-Alphonse Forel (1841 – 1912) who established the field with his studies on 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, for originally Societas Internalis Limnologiae). Forel‟s original definition of limnology, oceanography of lakes was expanded to encompass the study of all inland waters.

Welch (1935) conceived the problem of “Biological productivity” as the central theme of Limnology. He defined Limnology as that branch of science which deals with all causal influences which determine it. According to Schwoerbel (1987), Limnology is the science of inland waters viewed as ecosystems together with their structures, materials and energy balance. Kiihnelt (1960) considered limnology as a sub set of ecology along with “Oceanography” (which is concerned with marine ecosystem) and “Epheirology” (which deals with terrestrial habitats). In short, Limnology is the study of all aquatic systems including lakes, wetlands, marshes, bogs, ponds, reservoirs, streams, rivers etc. with regard to their physical chemical and biological characteristics. The term Limnology is derived from Greek word; Limne means lake and logos means knowledge. Limnology is often regarded as a division of ecology or environmental science. It is however, defined as “the study of inland waters” (running and standing waters fresh and sometimes saline; natural or manmade). This includes the study of lakes, ponds, rivers, reservoirs, swamps, streams, wet lands, bogs, marshes etc. Hence, it is commonly defined as that branch of science which deals with biological productivity of inland waters and with all the causal influences which determine it.

Biological productivity, as used in the above definition, includes its qualitative and quantitative features and its actual and potential aspects. Under the term inland waters are included all kinds or types of water – running or standing; fresh, salt or other physicochemical composition which are wholly or almost completely included within the land masses. Causal influences involve various factors – physical, chemical, biological, meteorological etc which determine the character and quantity of biological production.

Limnology encompasses an integration of physical, chemical, and biological components of inland aquatic ecosystems with the drainage basin, movements of water through the drainage basin, and biogeochemical changes that occur en route, and within standing (lentic) waters and exchanges with the atmosphere. The lake ecosystem is intimately coupled with its drainage area and atmosphere, and with its running (lotic) waters and ground waters that flow, and metabolize en route, components of the land being transported to the lake.

Topic No.2

Importance of limnology as a science

Although modern limnology encompasses the study of all inland waters, its development is particularly identified with the study of lakes. Much of the conceptual framework around which the science was built was derived from studies on lakes, and most of the early limnologists were lake scientists.

Limnology is the study of the chemistry, biology, geology, and physics of waters that are found within continents. In contrast, oceanography is the study of open ocean waters. Waters found within continents may be lakes, reservoirs, rivers, or wetlands (land where water covers the surface for at least part of the year) Although most limnologists specialize in freshwaters, the study of saline lakes, like the Great Salt Lake, also falls under the discipline of limnology.

One of the more important goals of limnology is providing guidelines for water management and water pollution control. Limnologists also study ways to protect the wildlife that lives in lakes and rivers as well as the lakes and rivers themselves. Some limnologists are working on construction of artificial wetlands, which could serve as habitats for a variety of animal and plant species and aid in decreasing water pollution.

Importance of limnology

•  Limnology is important because it deals with the study with every part of the freshwater.
•  It investigates the physical and the chemical quality of the fresh water.
•  It studies about the biodiversity of the freshwater.
•  It helps to develop the new scientific technology for the conservation of the freshwater.

In addition to scientific interest and basic knowledge, limnology can provide some important applications like,

•  Planktonic successions
•  Study of evolution of lakes and reservoirs
•  Geomorphology