A view of the Earth from a satellite shows an azure planet composed almost entirely of water. The oceans that cover two-thirds of the Earth's surface to an average depth of almost 2.5 miles contain 97% of the planet's water and have a profound influence on its environment. If the ocean basins were shallower, the seas would spread across the continents, and the only dry land areas wou…
Estuaries are places of transition, where rivers meet the sea. An estuary is a partially enclosed body of water formed where freshwater from rivers flows into the ocean, mixing with the salty seawater. Salinity in estuaries varies from slightly brackish (0.5 to 5 ppt) at the freshwater end to moderately brackish (5 to 18 ppt) to highly saline (25 to 30 ppt) near the ocean. Although influenced by t…
In many parts of the world, fish is the major source of protein in the diet. Humans on average worldwide obtain 16% of their animal protein from fish, and an estimated two billion people worldwide depend on fish for 40% of their protein supply. A staple in the diet of many cultures, fish are consumed in much greater quantities in countries other than the United States. The United States consumes o…
In its 2000 National Water Quality Inventory (2002), the EPA reported that fourteen of the twenty-seven coastal states and territories had rated the water quality of some of their coastal waters. The states had assessed 14% of the 22,618 miles of national coastline excluding Alaska, or 5.5% (3,221 miles) of ocean shoreline (including Alaska's 36,000 miles of coastline). Of the 14% of ocean …
Hundreds of times each year, beach closings take place to protect the public from possible exposure to pathogens (disease-causing organisms). The bacteria that cause the closings are generally harmless, but they are present in large numbers in the sewage of humans and warm-blooded animals. Their presence indicates the possible presence of disease-causing organisms. The most common problem caused …
Any number of man-made materials or excessive amounts of naturally occurring substances can adversely affect marine and estuarine waters and their inhabitants. Because water is such an effective solvent and dispersant, it is difficult to track and quantify many pollutants known to have been discharged into marine and estuarine waters, and in many cases the source of pollution may be unknown. Some …
Harmful algal blooms (HABs) are having significant impacts on coastal and estuarine areas of the United States and the rest of the world, affecting the health of both humans and aquatic organisms and the vitality of local and regional economies. The number and diversity of reported HAB events have increased since the 1970s. Understanding the causes of HABs and mitigating and preventing their conse…
Exotic species are plants, animals, and microbes that have been carried from one geographic region to another, either intentionally or unintentionally. Unintentional introduction includes transport in ballast water of ships, or as pests on imported fruits, vegetables, and animals or animal products. Prior to modern times, movement from one geographical region to another was infrequent and slow, al…
The environments of U.S. oceans and estuaries are flourishing at some locations, experiencing stress in others, and have been overwhelmed in a few localities. An increasing level of knowledge and awareness of environmental issues in the United States has led to more stringent regulatory protections for these ecosystems and a slow but steady reversal of a downward trend. Private organizations are t…
Please include a link to this page if you have found this material useful for research or writing a related article. Content on this website is from high-quality, licensed material originally published in print form. You can always be sure you're reading unbiased, factual, and accurate information.
Highlight the text below, right-click, and select “copy”. Paste the link into your website, email, or any other HTML document.
User Comments Add a comment…