Limnology

Laguna del Acebuche in the national park of Doñana in Spain. Wetlands are the most important ecosystems in some countries, especially Europeans.

Lake Lemán, the first lake studied by limnology.

Lake Hawea in New Zealand.

Limnology (from the Greek λίμνη, límnē, "lake" and λόγος, lógos, " study") is the branch of ecology that studies continental aquatic ecosystems (lakes, lagoons, rivers, ponds, marshes and estuaries), including groundwater and intermittent (or temporary) water bodies, interactions between organisms aquatic species and their environment, and social, ecological, and evolutionary factors that determine their distribution and abundance in these ecosystems. The term "limnology" includes brackish and salty continental waters, so it should not be assumed that it is strictly the study of fresh water.

More than a branch of ecology, it is a multidisciplinary field where branches such as biology, ecology, mathematics, engineering (civil, environmental, etc.), fish farmers, chemists, physicists, landscape architects, sociologists, statesmen.

In the beginning, the term limnology was confined only to the study of lakes and continental water masses. In 1922 the International Society of Limnology was founded, which included epicontinental waters as an object of study.

Continental bodies of water are of great importance for human beings, since many are a source of basic resources for the economy (drinking water, food, water for industry, transportation, future reserves, etc.) or play a role in paper (water purification, microclimatic regulation). This also has to be made compatible with the coexistence of flora and fauna species that subsist in the environment, or depend on it. For these reasons limnology has become a more important science, necessary for the management and conservation of aquatic environments.

History

European School

Its first major figure was the Swiss François-Alphonse Forel (1841-1912), who coined the term "Limnology" and he is considered the father of modern limnology. He concentrated his study on Lake Geneva (Switzerland). He considers that it is a science that integrates different disciplines. In 1892 he published his first study on the geology of Lake Geneva (physical-chemical characteristics) and organisms that inhabit the lake. Einar Naumann (1891-1974), Swedish botanist, studied the oligotrophic lakes of Sweden (very deep lakes, poor in nutrients, cold waters with very low phytoplankton development, very transparent waters). August Thienemann (1882-1960), German zoologist studied the mesotrophic and eutrophic lakes of Central Europe. Shallower and warmer, with more nutrients, less transparency.

This difference between oligotrophic lakes in the north and meso-eutrophic lakes in the south leads to regional limnology (which today no longer makes sense due to the alteration of natural ecosystems that receive large amounts of nutrients and become eutrophic regardless of its origin, a very serious problem that affects the whole world, not just Europe).

In 1922 the International Society of Limnology was founded. From this date, annual congresses are held, the proceedings of which are published.

Limnology in Spain

In the beginning, Europe was in the lead, but after World War II, the United States surpassed it in research, publications, and number of limnologists. In Spain discipline takes time to establish. Two personalities stand out in the field of hydrobiology (freshwater biology): Celso Arévalo and Luis Pardo. In the first decade of the XX century, Arévalo founded the National Hydrobiology Laboratory in Valencia. It focuses on the study of gaps. Pardo was a disciple of Arévalo around the years 1920-1930 and published informative works on freshwater.

In the 1950s Ramón Margalef (ecology, limnology, oceanography) studied aquatic ecology in general. He also studies general ecology hypotheses. He is internationally recognized. As a result of Margalef, many disciples arose, students of the University of Barcelona.

In 1981, a group of water scholars formed the Spanish Association of Hydrobiology, trying to bring together all Spanish stakeholders in Limnology and aquatic ecosystems. However, a couple of years later, it changed its name to the Spanish Association of Limnology. Later, in 2006, it changed its name to the Iberian Association of Limnology, in order to bring together Spanish, Portuguese and Ibero-American stakeholders in Limnology.

American School

Naturalist Stephen Alfred Forbes (1844-1930) favored lakes, marveling at the functional relationship they represented. In 1887 he published The lake as a microcosm . In it he describes the lake as a microcosm, a systemic unit in dynamic equilibrium conditioned by the interests of each organism in its struggle for life, governed by natural selection.

Chancey Juday studied lakes in Wisconsin and Lake Mendota. One of the conclusions she reached from him is that there is a dynamic equilibrium based on the fact that the input of energy and materials is balanced with the expense and output.

G. E. Hutchinson was responsible for the training of great American limnologists and ecologists. Treatise on limnology in 4 volumes focused mainly on lakes (geology, physico-chemistry and biology).

Raymond Lindeman focused on the study of a lake and defended Forbes' theory of dynamic equilibrium.

In 1936, the American Limnological Society was formed, which later became the Association for the Sciences of Limnology and Oceanography, or ASLO, for its acronym in English). A journal of limnology and oceanography is published.

Organizations

Relevance

Globally, water is not evenly distributed across the entire earth's surface. This causes different needs and specific pressures in each region and at the basin level, particularly where human populations exist directly or indirectly (if certain resources are collected and transported to another site, for example). Studies on the availability and quality of water are important to be able to model and forecast the water and economic situation of a region over time. The integrity and health of ecosystems contribute to the health of the soil and the ecological balance that maintains not only biological resources and their intrinsic value and right, but also adequate water recharge, water purification, recreational uses, and other resources and services. ecosystems from which humans benefit. In order to maintain these ecosystem services and resources that maintain our economy and health, it is important to understand the specific characteristics of each basin, each ecosystem, and often even each biological species in order to formulate good management practices and sustainable use.

A better understanding of aquatic ecology will contribute to better decision-making and knowledge of the real value of water.

General limnology

Physical properties

The 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.) and the structure of the land surrounding the body of water. Lakes, for example, are classified by their formation, and lake zones are defined by water depth. The morphometry of river and stream systems is conditioned by the underlying geology of the zone, as well as by the overall velocity of the water. Stream morphometry is also influenced by topography (especially slope), as well as precipitation patterns and other factors such as vegetation and land development. Connectivity between streams and lakes is related to landscape drainage density, lake surface, and lake shape.

Other types of aquatic systems that enter into the study of limnology are 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 freshwater and shallow and dry depending on the time of year.

Chemical Properties

The chemical composition of water in aquatic ecosystems is influenced by natural features and processes, including precipitation, underlying soil and bedrock in the drainage basin, erosion, evaporation, and sedimentation. All bodies of water have a certain composition of elements and compounds, both organic and inorganic. Biological reactions also affect the chemical properties of water. In addition to natural processes, human activities greatly influence the chemical composition of aquatic systems and the quality of their waters.

Oxygen and carbon dioxide

Oxygen saturation and dissolved carbon dioxide are often discussed together because of their coupled roles in respiration and photosynthesis. Dissolved oxygen concentrations can be altered by physical, chemical, and biological processes and reactions. Physical processes, including mixing with the wind, can increase dissolved oxygen concentrations, especially in surface waters of aquatic ecosystems. Since dissolved oxygen solubility is related to water temperature, changes in temperature affect dissolved oxygen concentrations, as warmer water has a lower ability to "hold" oxygen than cooler water. Biologically, both photosynthesis and aerobic respiration affect dissolved oxygen concentrations. Photosynthesis by autotrophs, such as phytoplankton and aquatic algae, increases dissolved oxygen concentrations while simultaneously reducing carbon dioxide concentrations, as carbon dioxide is absorbed during photosynthesis. All aerobic organisms in the Aquatic environments absorb dissolved oxygen during aerobic respiration, while carbon dioxide is released as a byproduct of this reaction. Because photosynthesis is limited by light, both photosynthesis and respiration occur during daylight hours, while only respiration occurs during the hours of darkness or in the dark parts of an ecosystem. The balance between production and consumption of dissolved oxygen is calculated as the "aquatic metabolism rate".

Cross-sectional diagram of factors that influence the metabolic rates of lakes and the concentration of gases dissolved in them. Processes in golden text consume oxygen and produce carbon dioxide, while processes in green text produce oxygen and consume carbon dioxide

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Vertical changes in dissolved oxygen concentrations are affected by both wind mixing of surface waters and the balance between photosynthesis and respiration of organic matter. These vertical changes, known as profiles, are based on principles similar to those of thermal stratification and light penetration. As light availability decreases deeper in the water column, photosynthesis rates also decrease and less dissolved oxygen is produced. This means that dissolved oxygen concentrations generally decrease as one moves deeper into the body of water because photosynthesis is not replenishing the dissolved oxygen that is absorbed through respiration. During periods of thermal stratification, temperature gradients Water density prevents oxygen-rich surface waters from mixing with deeper waters. Prolonged periods of stratification can cause depletion of dissolved oxygen at the bottom; when dissolved oxygen concentrations are less than 2 milligrams per liter, waters are considered hypoxic. When dissolved oxygen concentrations are approximately 0 milligrams per liter, conditions are anoxic. Both hypoxic and anoxic waters reduce the habitat available to oxygen-breathing organisms and contribute to changes in other chemical reactions in the water.

Biological properties

Lake George, New York, United States, an oligotrophic lake

One way to classify lakes is by their trophic status, which is closely related to nutrient chemistry and thus to primary production by photosynthetic organisms.

There is also another way to classify lakes (or other bodies of water) and that is with the trophic status index. An oligotrophic lake is characterized by relatively low levels of primary production and low levels of nutrients. A eutrophic lake has high levels of primary productivity due to very high levels of nutrients. Eutrophication of a lake can lead to algae blooms. Dystrophic lakes have high levels of humic matter and often have yellow-brown, tea-colored water. These categories do not have rigid specifications; the classification system can be seen more as a spectrum encompassing the various levels of aquatic productivity.

Professional Organizations

People who study limnology are called limnologists. There are many professional organizations related to limnology and other aspects of aquatic science, such as the Association for the Sciences of Limnology and Oceanography, the Iberian Association of Limnology, the International Society of Limnology, the Polish Limnological Society, the Society of Limnologists Canadians and the Freshwater Biological Association.