Nautilus belongs to the cephalopods, a category of mollusks to which the octopus, squid, and cuttlefish octopus also belong. The phylum Mollusca also includes the gastropods (snails and slugs) and bivalves (such as clams and oysters) among others, and is considered one of the most intelligent and successful invertebrate groups in the oceans.

Chemical Analysis of Water

The chemical analysis of water provides considerable insight into the health and workings of lakes, rivers, oceans, and groundwater. Water chemistry has helped scientists to define the different currents and circulation of the world's oceans, improved their understanding of water's interactions with Earth's geologic materials, and given insight into the impact of human activities on waterbodies.

Chemicals: Combined Effect on Public Health

In order to protect public health, regulatory agencies set water standards for substances not normally found in natural waters. So far, most standards have been set for individual substances according to their known harmful effects on human health or quality of life.

Chemicals from Agriculture

An important national issue in the United States is the degradation of water quality from nonpoint sources of pollution, including the prevalent use of fertilizers and pesticides on agricultural land. The issue is of interest to many residents, water resource managers, and policymakers across the nation because of the possible impacts on water uses, such as drinking, irrigation, recreation, and sustaining aquatic life.

Chemicals from Consumers

In people's daily lives, numerous consumer products are used inside the home, and the natural and synthetic chemicals in them often end up in the local sewage treatment plant or household septic system. For example, when someone scrubs and disinfects sinks and toilets, chemicals from the cleansers flow down the drain and down the toilet.

Chemicals from Pharmaceuticals and Personal Care Products

The use or consumption of natural resources often leads to ecological alteration. These changes can result from exposure of living systems to stressors ranging from physical alteration (such as habitat disruption) to chemical pollution.

Chesapeake Bay

The Chesapeake Bay is North America's largest estuary and has a shoreline of more than 12,800 kilometers (8,000 miles). The bay is a long, narrow arm of the Atlantic Ocean that extends northward into Maryland and cuts the state into two parts.

Clean Water Act

The Federal Water Pollution Control Act Amendments of 1972, commonly referred to as the Clean Water Act, is one of the most important and far-reaching environmental statutes ever passed by the U.S. Congress.

Climate and the Ocean

Weather is defined as the state of the atmosphere at a specific place and time, whereas climate is a long-term average of weather in a region. Many factors combine to create the different climates found throughout the world, such as the amount of solar radiation an area receives, local terrain, nearby large bodies of water, and changing geological and biological conditions.

Climate Moderator, Water as a

Water at the Earth's surface and in the atmosphere exerts a strong moderating effect on climate. Generally speaking, the higher the water content in the air, the more moderate (less extreme) the climate.

Coastal Ocean

When you take a waterfront vacation, do you say you are going to the beach or going to the coast? Both the beach and the coast are places where the land meets the sea, but the names reflect the variety of features and conditions that may exist there.

Coastal Waters Management

Americans love the seashore and the water. Nearly half of all the construction in the United States since the 1970s has been on the seacoast.

Colorado River Basin

Located in the southwestern United States and northwestern Mexico, the Colorado River is a 2,330-kilometer (1,450-mile) river with its headwaters in the Rocky Mountain National Park in north-central Colorado. The river is the primary source of water for a region that receives little annual rainfall.

Columbia River Basin

The Columbia River is one of the most dominant environmental features of the Pacific Northwest. Beginning high in the mountains of southeastern British Columbia, the Columbia River flows 2,000 kilometers (1,243 miles) through alpine and subalpine environments, montane forests, lava fields, semiarid grasslands, and low-elevation rainforests before entering the Pacific Ocean.

Comets and Meteorites, Water in

An understanding of the earliest composition of the solar system is derived from analyses of the Sun, comets, and the little-altered carbonaceous chondrites. Most of these measurements have come from analyzing the spectra of light that originates from the Sun or that is reflected by bodies such as comets and asteroids, the presumed source of most meteorites.

Conflict and Water

Water resources management increasingly requires compromise and consensus if solutions to problems are to be formulated and implemented. As issues of competing uses intensify, water decisionmakers are increasingly called upon to manage people as well as the water resource itself.

Conservation, Water

The term conservation emerged in the late nineteenth century to refer to the management—basically for economic reasons—of such valued natural resources as minerals, pastureland, timber, and topsoil. Conservation became part of U.S.

Cook, Captain James

Captain James Cook added more to early knowledge of the southern Pacific Ocean and the western North American coast than any other person. Among his contributions, he surveyed the St.

Corals and Coral Reefs

A coral reef is a structure in the sea constructed by coral skeletons and limestone debris that remains in place after the plant or animal dies. The structure is geological, the communities include plants and animals, and they are controlled by meteorological and oceanographic conditions.

Cost-Benefit Analysis

Since being mandated in the Flood Control Act of 1936 (PL 74–738), cost–benefit analysis has been used routinely in evaluating water projects. Cost–benefit analysis gives decisionmakers a method for evaluating investments in water projects, judging alternative projects, and estimating the impact of various regulatory changes.

Cousteau, Jacques

Jacques-Yves Cousteau, born in Saint-Andre-de-Cubzac, France, on June 11, 1910, explored the depths of the ocean and educated the world on what Jacques Cousteau developed, with Émile Gagnan, the first aqualung in 1943. For the next 50 years, he explored the world's oceans.


Crustaceans include crabs, lobsters, shrimp, krill, barnacles, and related species. There are approximately 40,000 crustacean species, the great majority of which are aquatic.