Aquatic Environments Lecture 1 PDF

Lecture 1: Aquatic environment In addition to the land (terrestrial) environment, there are three main environmental regions related to water, and these regions differ from each other in their different environmental characteristics and the organisms that live in them. The waters of these regions ha...

Lecture 1: Aquatic environment In addition to the land (terrestrial) environment, there are three main environmental regions related to water, and these regions differ from each other in their different environmental characteristics and the organisms that live in them. The waters of these regions have their own chemical and physical characteristics that make them distinct from each other. The three aquatic environments are: 1. Freshwater Habitat 2. Estuaries environment 3. Marine Habitat 1. Freshwater Habitat Freshwater occupies a small portion of the Earth's surface compared to the sea, ocean, and land water. But the importance of fresh water to humans goes beyond its small area due to its pleanty and consider cheap for daily and industrial uses. Recently, humans have begun to harm this natural source, and therefore this damage must be reduced, or else Fresh water has become unusable by humans themselves. Characteristics of freshwater: The freshwater environment differs from saltwater in many characteristics, including: 1. Freshwater almost has very little concentration of salts. 2. The factors that mainly affect freshwater organisms are oxygen, temperature, and food. 3. Organisms in the freshwater environment are exposed to the risk of drifting from high places or from places where this freshwater is located to the seas. Therefore, these organisms have adapted themselves to this danger by attaching to trees, stones, or any other means. Examples of these adaptations to resist drift are: A. Some parts of the body of these organisms transform into suckers that attach to solid objects. 1 B. In fish, the pectoral fins or body scales change into suckers, as is the case in mollusks and crustaceans. 4. Some fish can swim against the water current. 5. Some organisms can live in brackish water. This is because these organisms can survive in the area between freshwater and saltwater, a mixture of the two types for a certain period, and then enter the sea. These organisms are considered few. 6. It is characterized by being smaller in size than marine water organisms. 7. The most important freshwater animals are: protozoa, sponges, cnidarians, snails, and mollusks. General divisions of the freshwater environment Fresh water can be divided concerning water movement into two main parts: 1. Lentic water (Still water): includes lakes and ponds. Lakes are a relatively static body of water occupying a specific basin of the Earth's surface. Lakes are found in many regions of the world, but they are widely spread in the Northern Hemisphere and are also found in other regions such as East Africa. There are some artificial lakes that humans build. Lakes differ from ponds in some characteristics, the most important of which are: 1. Lakes have a larger area than ponds. 2. The area far from the beach is more important in terms of productivity for lakes, and vice-versa for ponds. 3. There are thermal stratifications in some seasons of the year in lakes, but in ponds, the movement of water prevents such stratification to occur. 2 Lake formation: There are several ways in which lakes can be formed, and these methods depend on how the lake basin was formed. Some basins are formed as a result of the movement of the earth’s crust, volcanic activity, or the activity of icebergs. Other types of lake basins are formed as a result of other factors such as landslides or by the action of some living creatures, such as beavers, or the dense growth of some types of aquatic plants that block and reserve water in a specific area of the valley. In general, the shape of the lake depends on the way its basin is formed. Some lakes have circular basins, which are lakes of volcanic origin, or lakes with semi-circular basins, as is the case with lakes that are found in mountainous areas and are of origin dating back to the Galactic Age. As for lakes with semi-tilted basins, they were formed by the movement of the earth’s crust, and lakes with crescent basins were formed by streams and rivers. It is not possible to apply these types to all lakes in the world, as there are some external factors such as dams, canals, and changes that occur in the shape of the water outfalls leading to the lake. Several factors deeeeeeee the nature of the lake bottom, including the age of the lake, its size, and the type of bottom. Newly formed lakes have a rocky or sandy bottom with little sediment and organic matter, as the latter accumulates in large quantities as the age of the lake increases. Classification of lakes: It has become clear from studying the environment of lakes that it is difficult to establish some foundations that can be relied upon to classify natural lakes. This difficulty is evident in the fact that lakes possess a large group of overlapping characteristics. Some scientists have attempted to classify lakes based on lake formation and the region geomorphology, and more have been distinguished. There are 75 types of them. However, there is another system by which we can classify lakes, taking into account the amount of nutrients present in the lake. Accordingly, there are four types: 3 1. Oligotrophic lakes: This type of lake lacks the presence of sufficient living organisms relative to its size. It is also characterized by an excess of oxygen in the lower layers of the lake due to its lack of use by living organisms. These lakes are also deep and the coastal area in them is small. As for nutrients such as phosphorus, nitrogen, and calcium, their concentration is very low, and in the summer season the lower part of these lakes is cold and is known as a layer Hypolimnion, the top is a warm layer called Epilimnion, these two layers are separated by a third layer called metalimnion. 2. Eutrophic lakes: These lakes are characterized by containing large amounts of biomass. They are shallow and have large beaches. The lower Hypolimnion region of the lake is deeper than the upper Epilimnion layer. During the summer season, the concentration of oxygen decreases to a large degree in the lower layer, where it is used in the oxidation process that takes place on organic materials. Dead body at the bottom. 3. Mesotrophic lakes: This type of lake has intermediate characteristics that fall between the two types of lakes mentioned above. 4. Dystrophic lakes: These lakes are mainly found in the mountainous and swampy regions. These lakes are rich in organic materials and contain a high concentration of humic acid. The amount of humic acid is large, so the water is brown and the hydrogen ion concentration is low. The analysis process is also slow. There is little organic matter, and the reason for this is due to the low concentration of calcium, which results from the accumulation of organic materials and a scarcity of dissolved nutrients. 2.Lotic water (Movement water or Run off water) It includes the water of rivers and streams. Flowing water differs from lentic water in several aspects: 1. Continuous movement of water in one direction. 2. The speed of water flow varies relative to the volume of water. 3. Large variations in water level. 4 4. The depth is small compared to what it is in lakes. 5. Life, physical, and chemical factors change gradually along the watercourse and in one direction. 6. As the flowing water moves forward, it increases in length, width, and depth. 7. Permanent transfer of erosion materials by running water, as running water carries out the transfer of these materials. 8. The productivity of running water depends on the quality and quantity of nutrients present in its basins. 9. Flowing water is open, such as rivers and streams, while still water is closed bodies of water, such as lakes and ponds. 10. The use of nutrients in still water is for several times, while it is temporary in flowing water. 11. The concentration of oxygen in flowing water is more similar between layers of water than in still water. Flowing water is also rich in oxygen due to the constant movement of water and the large surface area exposed to the air. This state of increase in the amount of oxygen occurs even if there are no green plants. 5