Lakes

Aquatic Habitats

Aquatic Food Webs

Aquatic Food Webs [Image: US EPA]

Aquatic food webs are conceptual diagrams that demonstrate the flow of energy and nutrients in aquatic systems. Although the species that make up aquatic food webs will greatly vary depending on habitat type, the basic trophic levels or feeding levels of food webs are similar. Producers such as phytoplankton, aquatic plants, and algae use photosynthesis to convert sunlight and nutrients into living tissue. Primary consumers such as zooplankton and plant grazers eat producers. Secondary and tertiary consumers such as invertebrate predators, birds, fish, mammals, and humans eat lower-level prey items. Decomposers consume dead plants and animals, breaking organic matter down into nutrients. Since organisms seldom feed exclusively on another, several food chains are often woven together to form a "food web," a complex cycle of interconnected organisms and organic matter.

Explore the NBII Fisheries and Aquatic Resources Node's Aquatic Organisms section for more information about the wide variety of organisms that use the aquatic environment, ranging from endangered species to aquaculture.

Discover the NBII Bird Conservation Node's U.S. Fish and Wildlife Service Focal Bird Species, many of which are shorebirds, seabirds, and waterfowl that are important components of aquatic food webs.

The Clean Water Act

EPA logo [Image: U.S. Environmental Protection Agency]

"The objective of the Federal Water Pollution Control Act, commonly referred to as the Clean Water Act (CWA), is to restore and maintain the chemical, physical, and biological integrity of the nation's waters by preventing point and nonpoint pollution sources, providing assistance to publicly owned treatment works for the improvement of wastewater treatment, and maintaining the integrity of wetlands." Visit the US EPA Clean Water Act website for detailed information about the Clean Water Act, including Total Maximum Daily Loads (TMDLs), point and non-point source pollution measures, wetlands regulations, estuary regulations, and more.

Lakes

Tenaya lake, Yosemite National Park
[Photo: National Park Service]

A lake is any body of water of substantial size, other than the ocean, that holds water with little or no horizontal movement. Lakes can be anywhere from a few meters deep to over 60m deep, and up to 16 km long. Lake Superior, the largest of the five Great Lakes of North America, has the largest freshwater surface area in the world at 82,103 km2. Human-made reservoirs are also considered lakes, despite having been created by the construction of dams or dikes.

In temperate regions, many lakes become thermally stratified as the seasons change. In the summer, warm air heats the surface of the water body, creating the epilimnion, a layer of warm, less dense water. The cooler, denser water below is the hypolimnion, and the transition between the two is the thermocline. When air temperatures decrease at the end of the summer, the water in the epilimnion becomes more dense as it cools, and sinks. "Lake turnover" refers to this phenomenon in which the top layer of water, which is highly oxygenated and rich with plant and animal life from summer productivity, replaces the water below. This process is essential for bringing dissolved oxygen and nutrients to the bottom regions of the lake.

Sources:
Cech, T. 2005. Principles of Water Resources, Second Edition. John Wiley and Sons. Hoboken, NJ.

To find out more about lakes including their classification, habitats, and human impacts, follow the links below:

	Classification Learn about how lakes are classified.
	Human Impacts (Accessible soon) Find out about how human activities can affect lake habitats.
	Lake Habitats Learn about the types of habitats within lakes.

Discover the National Fish Habitat Action Plan and Data

NFHAP logo [Image: National Fish Habitat Action Plan]
[Image: National Fish Habitat Action Plan]

The National Fish Habitat Action Plan (NFHAP) is an unprecedented attempt to address a nationwide fish crisis by focusing on the loss and degradation of their habitat. The Plan was born in 2001 by an ad hoc group supported by the Sport Fishing and Boating Partnership Council. This group was inspired to develop a partnership effort for fish conservation in the image of the successful and strategic North American Waterfowl Management Plan.

As a federal-level partner, the USGS-NBII was designated by the National Fish Habitat Board to house the data delivery system supporting the National Fish Habitat Action Plan. Find out more about NBII's role in the NFHAP and the data associated with the Plan.

Nutrient Cycling vs. Spiraling

Nitrogen and phosphorus are important to aquatic ecosystems in their dissolved or available form for organisms to incorporate into living tissue, and influence the overall productivity of a given ecosystem. They are taken up by living organisms and move through the aquatic food web, including release as waste products and decomposition, in a pattern referred to as the nutrient cycle . In relatively closed systems such as lakes and reservoirs, available nutrients are often cycled repeatedly before they are exported. However, in rivers, the effect of running water transforms the nutrient cycle into a nutrient spiral , in which nutrients are transported downstream in addition to moving through aquatic food webs. "Tighter" nutrient spirals refer to stream systems that retain nutrients relatively well, through instream habitat features that slow the downstream loss of nutrients.

Featured Lake

Yellowstone Lake [Image: USGS]

Yellowstone Lake, located in the center of Yellowstone National Park, is the largest high-elevation lake in North America. It is 20 miles long and 14 miles wide, encompasses 131 square miles of surface area, and has an average depth of 139 feet. It is fed by snowmelt from numerous tributaries, and supports a diverse and rich food web spanning the aquatic and terrestrial. Populations of native Yellowstone cutthroat trout, bald eagles, osprey, pelicans, grizzly bears, and black bears rely on the Yellowstone Lake ecosystem.

The lake is bisected by the rim of the Yellowstone Caldera, which is an active caldera that last erupted 640,000 years ago. Recent research by the USGS and partners shows that the floor of Yellowstone Lake has many hydrothermal features, including hot spring vents and explosion craters, which creates unique habitat in localized areas for a diverse array of organisms. The Yellowstone Lake Biodiversity Inventory Team is conducting research on the lake's aquatic organisms and are identifying microscopic organisms within the lake through taxonomy and genetic analysis that may be new to science.

EPA National Lakes Assessment

National Lakes Assessment [Image: US EPA]

The US Environmental Protection Agency, along with state and tribal partners, has conducted a comprehensive survey of the nation's lakes, ponds, and reservoirs: the National Lakes Assessment. This project uses consistent sampling and analytical procedures to represent and compare lakes and their condition across the country at a regional and national scale. It also provides capacity for continued monitoring, assessment, and collaboration of the nation's lakes.

FishBase

Fishbase is a searchable global database of fish species information.

FishBase on the web contains practically all fish species known to science. Search over 28,000 fish species by common name, scientific name, ecosystem, or country. Or, use the search feature to find tools, maps, or references.

Learn more about FishBase.

The NBII Program is administered by the Biological Informatics Program of the U.S. Geological Survey

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