Water pollution is the contamination of natural water bodies by chemical, physical, radioactive or pathogenic microbial substances. Adverse alteration of water quality presently produces large scale illness and deaths, accounting for approximately 50 million deaths per year worldwide, most of these deaths occurring in Africa and Asia. In China, for example, about 75 percent of the population (or 1.1 billion people) are without access to clean drinking water. Widespread consequences of water pollution upon ecosystems include species mortality, biodiversity reduction and loss of ecosystem services. Some water pollution may occur from natural causes such as sedimentation from severe rainfall events; however, natural causes, including volcanic eruptions and algae blooms from natural causes constitute a minute amount of the instances of worldwide water pollution. The most problematic of water pollutants are microbes that induce disease, since their sources may be construed as natural, but a preponderance of these instances result from human intervention in the environment (such as discharge of raw sewage) or human overpopulation phenomena. One of the chief causes of water pollution is agricultural activity where tillage practices, fertilizer, pesticide and herbicide use create massive amounts of sedimentation and chemical discharge to natural waters. Industrial discharges, by contrast, have been greatly mitigated in Western Countries, but remain a significant issue in developing countries.
[Raul Perianez is the lead author of this article]
Heavy metal distributions in the Gulf of Cadiz are generated chiefly by coastal riverine discharge, and thus...
OverfishingLast Updated on 2014-12-07 17:22:32Overfishing is the human act of extracting aquatic (that is, marine and freshwater) fauna from natural water bodies at a rate greater than the reproductive and recruitment functions can replace that extraction. While there is some evidence that localized overfishing may have occurred in prehistoric eras, the bulk of overfishing has taken place in the last 150 years as the human population has expanded greatly and fishing technologies have enabled harvesting of many species at rates not imagined in earlier times. For over a century man's role in the depletion of certain regional fisheries has been noted. A functional definition of overfishing is sometimes given as the reduction in catch per unit effort by fishermen. Typically the concept of overfishing is linked to an individual aquatic species, and this issue is most often discussed within a specific marine or lacustrine province... More »
Mississippi RiverLast Updated on 2014-11-29 22:15:22The Mississippi River drains the largest river basin in North America, and is one of the major rivers of the world.
The Mississippi River watershed is the fourth largest in the world, extending from the Allegheny Mountains in the east to the Rocky Mountains in the west. The watershed includes all or parts of 31 states and two Canadian provences. The watershed measures approximately 1.2 million square miles (3.1 million square kilometers), covering about 40% of the lower 48 states. The Mississippi drains most of the United States between the Appalachian Mountains in the east and the Rocky Mountains in the West.
The mainstream of the Mississippi River has headwaters rising at Lake Itasca, Minnesota and flows approximately 2340 miles (3765 km). Though the longest part of the river includes the the Missouri River which flows approximately 2540 miles (4088 km) before joining the... More »
Water pollutionLast Updated on 2014-11-17 12:18:45Water pollution is the contamination of natural water bodies by chemical, physical, radioactive or pathogenic microbial substances. Adverse alteration of water quality presently produces large scale illness and deaths, accounting for approximately 50 million deaths per year worldwide, most of these deaths occurring in Africa and Asia. In China, for example, about 75 percent of the population (or 1.1 billion people) are without access to unpolluted drinking water, according to China's own standards. Widespread consequences of water pollution upon ecosystems include species mortality, biodiversity reduction and loss of ecosystem services. Some consider that water pollution may occur from natural causes such as sedimentation from severe rainfall events; however, natural causes, including volcanic eruptions and algae blooms from natural causes constitute a minute amount of the... More »
Animal Agriculture and the EnvironmentLast Updated on 2014-11-15 14:53:25
Animal production industries have seen substantial changes over the past several decades, the result of domestic/export market forces and technological changes. The number of large operations has increased, and animal and feed production are increasingly separated in terms of both management and geography. Concern that these changes are harming the environment has prompted local, State, and Federal policies and programs to control pollution from animal production facilities.
Changes in the structure of livestock and poultry production are behind many of the current concerns about animals and the environment. Structural changes have been driven by both innovation and economies of scale. Organizational innovations, such as production contract arrangements, enable growers to access the capital necessary to adopt innovative technologies and garner economies of size in their efforts... More »
Aquatic plantsLast Updated on 2014-11-09 18:55:53
Aquatic plants grow in shallow to deep water zones. The three main types of aquatic plants are (1) single-celled phytoplankton, (2) periphyton (algae growing attached to substrates) and (3) multicellular macrophytes. Phytoplankton includes several groups of algae (e.g., green algae, golden brown algae, euglenophytes, dinoflagelates, and diatoms) and one group of photosynthetic bacteria (Cyanobacteria). Planktonic algae may be either benthic (attached to a substrate) or planktonic (floating in the water column). There are large numbers of phytoplankton (> 400 species) in many bodies of freshwater; phytoplankton are most common in habitats with high nutrient levels.
Periphyton may grow attached to other plants (ephytic periphyton) or on rocks and other substrate (epibenthic periphyton). Typically, periphyton is made up of a diatoms, a variety of filamentous algae... More »
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