Lecture 2: Environmental Factors Affecting Freshwater Environments PDF

1 Lecture 2: 2 3 Environmental factors affecting the freshwater environment: 4 The most important of these factors are: 5 6 1. Temperature: 7 8 Despite the change in temperature in the water, it is considered a factor affecting the life of the 9 organisms that live in the wat...

1 Lecture 2: 2 3 Environmental factors affecting the freshwater environment: 4 The most important of these factors are: 5 6 1. Temperature: 7 8 Despite the change in temperature in the water, it is considered a factor affecting the life of the 9 organisms that live in the water, because most of these organisms have a short range to withstand 10 the temperature change. Therefore, any change in temperature resulting from human activities may 11 lead to a major impact on the life of these organisms, and the change in temperature leads to 12 changes in the water masses, where there is a rotation of the water masses, and a kind of gradation 13 occurs in the layers of water and these changes in the masses. Aquatic water has a significant impact 14 on aquatic life. 15 2. Transparency and light: 16 Suspended materials determine the penetration of light rays into layers of water, and turbidity 17 caused by silt is considered one of the environmental factors affecting living organisms. However, 18 if turbidity is caused by the living organisms themselves, measuring transparency becomes an 19 indicator of living mass. 20 21 The transparency measuring device is known as the Secchi disk, and this name was given to the 22 disk by the Italian scientist who created it in the year 1865. 23 24 Light plays an important role in the growth of plants, and since it is considered the basic link in the 25 animal nutrition chain, a small mass of water rich in plants may be sufficient for the livelihood of 26 a large group of animals. Light is also an important factor for animals, as it helps them to see, which 27 in turn is considered an important and influential factor in Food relations. 28 29 3. Current: 30 Current is one of the determining factors in the livelihood of aquatic organisms, especially those 31 that live in rivers and springs. 32 The current also plays an important role in the distribution of vital gases, salts, and small organisms. 33 34  1 4. Dissolved gases: 2 In contrast, in the marine environment, both oxygen and carbon dioxide are considered factors 3 affecting the life of aquatic organisms. 4 Nowadays, it is a time when everyone is talking about environmental pollution. Dissolved oxygen 5 requirements have become an important factor that is always measured in the degree of the 6 environment and an indicator of its pollution. 7 The amount of oxygen decreases as the temperature increases, and a decrease in the amount of 8 oxygen occurs when there are quantities of dead plants and animals, as most of the oxygen is used 9 in the organic decomposition process. 10 11 5. Concentration of salts: 12 The nature and quantity of salts present in a spot of fresh water depends mainly on the geology of 13 the earth. The reason for this is that a large percentage of the soil in these lands drifts into a spot of 14 freshwater at different times of the year. 15 16 The most important salts found in fresh water are calcium and magnesium bicarbonates. As for the 17 salts present in the form of carbonates, these precipitate to the bottom and mix with the clay. The 18 source of the bicarbonate and carbonate salts is from the combination of carbon dioxide gas, which 19 has a great ability to dissolve in water as it enters it through the atmosphere. There is another source 20 for it, which is organic decomposition by bacteria or as a result of the respiration of aquatic 21 organisms. 22 23 Ecological distribution of organisms in the freshwater environment: 24 Aquatic organisms that live in freshwater environments can be classified and placed in a specific 25 order or system. 26 It differs from the system used in classifying living organisms, and this system is based on 27 environmental characteristics such as: Ecological niches or an organism's location in the food chain 28 or energy chain. 29 Aquatic organisms are divided according to trophic levels into the following: 30 31 1. Producer organisms: They include green plants and microorganisms that produce organic 32 materials. 33 2. Consumer organisms: These includes all living organisms that fall within the categories of 34 secondary producers, plant-feeding, predatory, and parasitic organisms.  1 3. Saprophytic (decomposers) organisms: They are divided according to the nature of the rotting 2 organic materials. 3 4 5 Aquatic organisms are divided based on the nature of their lives into the following: 6 7 1. Benthic organisms: These include those organisms that stick to or settle on the bottom or 8 those organisms that live in the bottom sediments, and the animals of these organisms are 9 divided into two parts. 1) Those that are filter fed. And 2) Those that feed on sediments, 10 such as oysters and gastropods. 11 2. Attached organisms: These are living organisms, include plants and animals, that adhere 12 or attach to the stems and leaves of aquatic root plants or to any other surface protruding 13 above the bottom. 14 3. Plankton: They are living, floating organisms whose movement depends on water currents. 15 Although some zooplankton have the ability to move and remain in a vertical position, 16 floaters in general cannot move against water currents. 17 4. Nekton: Living organisms that have the ability to swim and move freely and include fish, 18 amphibians, and aquatic insects. 19 5. Nestons: These are organisms that swim on the surface of the water. 20 21 22 23 24 25 26 27 28 29 30