Rodeo Lagoon, viewed on a windy day from its southeast corner
|Location||Marin County, California|
|Max. length||900 metres (3,000 ft)|
|Max. width||250 metres (820 ft)|
|Surface area||15 hectares (37 acres)|
|Max. depth||2 metres (6.6 ft)|
Rodeo Lagoon is a coastal lagoon located in the Marin Headlands division of the Golden Gate National Recreation Area, which is in southern Marin County, California. 900 metres (3,000 ft) by 250 metres (820 ft), and is about 2 metres (6.6 ft) deep at its maximum depth. It covers a surface area of about 15 hectares (37 acres).This brackish water body is separated from the Pacific Ocean by a sand bar that forms Rodeo Beach. Rodeo Lagoon stretches approximately
Rodeo Lagoon empties into the Pacific Ocean when the water level reaches a high enough level to erode through the sand bar. This high water level usually occurs in the winter months. The outlet channel, shown at left looking southeast towards Rodeo Lagoon, is spanned by a pedestrian bridge that provides access to Rodeo Beach. Like many other coastal lagoons in California, the outlet becomes completely blocked by a sand bar during the dry summer months, resulting in negligible exchange between the lagoon and ocean during that time.
The depth, surface area, and volume of the lagoon all vary depending on the configuration of the sand berm (high or low) and rainfall (wet or dry). Depths in the center range from less than 1.5 metres (4.9 ft) in a dry summer to nearly 3 metres (9.8 ft) in a wet winter.
Tides do not have a significant effect on the circulation of water in Rodeo Lagoon. Instead, the circulation of water in Rodeo Lagoon is driven almost entirely by the wind. Since the Marin Headlands are often quite windy, it is not unusual to see Langmuir circulation form windrows of foam on the surface of the lagoon.
Rodeo Lagoon is a brackish water body, with salinities in most of the lagoon ranging from 2 to 10 practical salinity units (psu) over the course of the year. However, water near the bottom of the lagoon is often much saltier, reaching levels as high as 25 psu. The bowl-shaped bathymetry of the lagoon traps this dense, salty water and prevents it from quickly draining back out in the ocean.
Rodeo Lagoon provides habitat to a protected species, the tidewater goby. It also provides habitat to many species of migrating waterfowl. Resident fish include the threespine stickleback and prickly sculpin in addition to the tidewater goby. A family of river otters also makes frequent use of the lagoon, and includes brown pelicans in their summer dietThe lagoon is ringed by emergent aquatic vegetation, such as willows and cattail, and has submerged aquatic vegetation like sago pondweed and widgeon grass in the shallow areas. The phytoplankton community includes diatoms, chlorophytes, flagellated protozoa, Microcystis aeruginosa, and Nodularia spumigena. Microcystis sp. and Nodularia sp. are types of toxic cyanobacteria, capable of releasing the toxins microcystin and nodularin into the water.
The population of phytoplankton described above is extremely high in the summer, a condition known as eutrophication. At times, the algae form a visible surface scum, and their high concentration results in large swings in the dissolved oxygen content of the water, culminating in a depletion of oxygen when the population finally crashes. This annual algae bloom, because of its size and potential toxicity, is considered problematic for water quality and fish survival.
Rodeo Lagoon typically suffers from an oxygen deficit or hypoxia in the summer and fall. This deficit is caused by the high oxygen consumption of decaying algae that occurs during that time of year. The large algae population, which withdraws carbon dioxide from the water, also raises the pH to very high levels. The pH is typically greater than 9 throughout the summer algae bloom.
The lagoon is located within the geologically complex Marin Headlands and fills a valley drowned by recent sea level rise following the last glacial period.The bed of the lagoon is covered by viscous black mud that is high in organic content, except at the east and west ends, where non-organic sediment can be found.
Rodeo Lagoon was mostly unaltered until the area was developed by the U.S. military into Fort Cronkhite and Fort BarryIn 1937, the Army constructed a road crossing at the east of the lagoon, which resulted in a reduction in the lagoon's size as the area upstream of the crossing gradually turned into a freshwater marsh. The lagoon is now about 80% of its original size.
Recreation is not allowed on or in Rodeo Lagoon because of water quality and wildlife concerns. However, the lagoon and surrounding area is an excellent place for wildlife viewing, particularly birdingand watching the playful river otters.
Plankton are the diverse collection of organisms that live in large bodies of water and are unable to swim against a current. The individual organisms constituting plankton are called plankters. They provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish and whales.
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, and is often recognized by the discoloration in the water from their pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic, multicellular organisms like seaweed and microscopic, unicellular organisms like cyanobacteria. Algal bloom commonly refers to rapid growth of microscopic, unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.
A thermocline is a thin but distinct layer in a large body of fluid in which temperature changes more rapidly with depth than it does in the layers above or below. In the ocean, the thermocline divides the upper mixed layer from the calm deep water below.
The Marin Headlands is a hilly peninsula at the southernmost end of Marin County, California, United States, located just north of San Francisco across the Golden Gate Bridge, which connects the two counties and peninsulas. The entire area is part of the Golden Gate National Recreation Area. The Headlands are famous for their views of the Bay Area, especially of the Golden Gate Bridge.
The Golden Gate National Recreation Area (GGNRA) is a U.S. National Recreation Area protecting 82,027 acres (33,195 ha) of ecologically and historically significant landscapes surrounding the San Francisco Bay Area. Much of the park is land formerly used by the United States Army. GGNRA is managed by the National Park Service and is the most visited unit of the National Park system in the United States, with more than 15 million visitors a year. It is also one of the largest urban parks in the world, with a size two-and-a-half times that of the consolidated city and county of San Francisco.
A lake ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions.
Rodeo Beach is a beach in the Golden Gate National Recreation Area located in Marin County, California, two miles north of the Golden Gate Bridge. It is characterized by a spit of around 50 meters width at the mouth of a long embayment, known as Rodeo Lagoon; for much of the year the lagoon is cut off from the ocean, making the beach spit a baymouth bar. Part of the beach is sheltered by cliffs. Rodeo Beach is known for its dark, pebbly sand, its uses for surfing and sunbathing, and its locale as a place for viewing, but not collecting, semi-precious stones. This beach is unique among California beaches in that it is largely made up of coarse, pebbly chert grains, both red and green in color. Its mineral composition sets it apart from every other beach in the state Surfing is possible throughout the year and at all tidal stages, but is best in summer — although there is a risk of shark attacks. Due to the North bar offshore of this beach it results in big waves in the winter months with the big swells that come in. Strong currents make swimming dangerous.
The black goby is a species of ray-finned fish found in the Eastern Atlantic and Mediterranean Sea and Black Sea. It inhabits estuaries, lagoons, and inshore water over seagrass and algae. It feeds on a variety of invertebrates and sometimes small fish. This species can also be found in the aquarium trade.
The term fish kill, known also as fish die-off, refers to a localized die-off of fish populations which may also be associated with more generalized mortality of aquatic life. The most common cause is reduced oxygen in the water, which in turn may be due to factors such as drought, algae bloom, overpopulation, or a sustained increase in water temperature. Infectious diseases and parasites can also lead to fish kill. Toxicity is a real but far less common cause of fish kill.
Dawesville Channel is an artificial channel between the Peel-Harvey Estuary and the Indian Ocean at Dawesville, about 80 km (50 mi) south of Perth in Western Australia. It is just south of the regional city of Mandurah and just north of Yalgorup National Park.
In physical oceanography, Langmuir circulation consists of a series of shallow, slow, counter-rotating vortices at the ocean's surface aligned with the wind. These circulations are developed when wind blows steadily over the sea surface. Irving Langmuir discovered this phenomenon after observing windrows of seaweed in the Sargasso Sea in 1927. Langmuir circulations circulate within the mixed layer; however, it is not yet so clear how strongly they can cause mixing at the base of the mixed layer.
The Agua Hedionda Lagoon is a lagoon in Carlsbad, California, that is fed by the Agua Hedionda Creek. Stewardship of much of the lagoon is held by the Encina Power Station and its owner NRG Energy. In November 2000 the Agua Hedionda Lagoon was designated as a critical habitat for the tidewater goby.
A fringing reef is one of the three main types of coral reef recognized by most coral reef scientists. It is distinguished from the other main types in that it has either an entirely shallow backreef zone (lagoon) or none at all. If a fringing reef grows directly from the shoreline the reef flat extends right to the beach and there is no backreef. In other cases, fringing reefs may grow hundreds of yards from shore and contain extensive backreef areas with numerous seagrass meadows and patch reefs.
This is a glossary of terms used in fisheries, fisheries management and fisheries science.
Valenciennea strigata is a species of fish in the family Gobiidae, the gobies. Its common names include the blueband goby, golden-head sleeper goby, and pennant glider. It is native to the Indian Ocean and the western Pacific Ocean where it can be found in outer lagoons and the seaward side of reefs. It occurs in a variety of substrates, sand, rubble, hard, at depths of from 1 to 25 metres. It primarily inhabits burrows dug under rubble, using them as both a nesting site and a refuge from predators. Such burrows typically have two entrances; however, only one of them is open, as the other is covered by rubble, sand, and algae. It can also be found in the aquarium trade. This species can reach a length of 18 centimetres (7.1 in) TL. It is the type species of the genus Valenciennea.
Facultative lagoons are a type of waste stabilization pond used for biological treatment of industrial and domestic wastewater. Sewage or organic waste from food or fiber processing may be catabolized in a system of constructed ponds where adequate space is available to provide an average waste retention time exceeding a month. A series of ponds prevents mixing of untreated waste with treated wastewater and allows better control of waste residence time for uniform treatment efficiency.
Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.
Lake Burton, also known as Burton Lagoon, is a meromictic and saline lake in the Vestfold Hills of Princess Elizabeth Land in Eastern Antarctica. Princess Elizabeth Land, including the lake, is claimed by Australia as part of the Australian Antarctic Territory. The lake has a surface area of 1.35 km2 (0.52 sq mi), a volume of 9.69 million m3, a maximum depth of 18.3 metres (60 ft) and a mean depth of 7.16 metres (23.5 ft). The lake is named after H. R. Burton, a biologist working in the Vestfold Hills of Antarctica.
In oceanography, a front is a boundary between two distinct water masses. The water masses are defined by moving in different directions, i.e. on one side of the front the water is generally moving in one way, and on the other side of the front, the water is moving in another. Depending on the directions of the water masses, a front may be defined as convergent or divergent. The water masses on either side of a front may also have different temperatures, salinities, or densities, along with differences in other oceanographic markers. While most fronts form and dissipate relatively quickly, some, such as the fronts caused by the antarctic circumpolar current, persist for long periods of time.