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Posts tagged Algal Bloom

The Volga River Delta in the Caspian Sea – April 19th, 2009

April 19th, 2009 Category: Image of the day, Rivers

Caspian Sea - March 31st, 2009

Caspian Sea - March 31st, 2009

The Volga Delta is the largest inland river delta in Europe, and occurs where Europe’s largest river system, the Volga River, drains into the Caspian Sea in Russia’s Astrakhan Oblast, north-east of the republic of Kalmykia. Although some clouds partially obstruct the view of the area, the delta is visible on the northwestern shores.

The Volga Delta has grown significantly in the past century because of changes in the level of the Caspian Sea. However, in recent years industrial and agricultural modification to the delta plain has resulted in significant wetland loss.

Between 1984 and 2001, the delta lost 277 km² of wetlands, or an average of approximately 16 km² per year, from natural and human-induced causes.

The Volga discharges large amounts of industrial waste and sediment into the relatively shallow northern part of the Caspian Sea. The added fertilizers nourish the algal blooms that grow on the surface of the sea, allowing them to grow larger.

This algae is responsible for the green color of the water immediately around the delta, and may also be contributing to the green color present in the rest of the sea’s northern section.

Lake Turkana in the Kenyan Desert

April 1st, 2009 Category: Lakes

Kenya - March 24th, 2009

Kenya - March 24th, 2009

Lake Turkana, formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world’s largest permanent desert lake and the world’s largest alkaline lake.

The climate is hot and very dry. On-shore and off-shore winds can be extremely strong as the lake warms and cools more slowly than the land. Sudden, violent storms are frequent.

Three rivers (the Omo, Turkwel and Kerio) flow into the lake, but lacking outflow its only water loss is by evaporation. Lake volume and dimensions are variable. For example, its level fell by 10 meters between 1975 and 1993. The water is potable but not palatable.

Despite the barren surroundings, the lake itself is a surprisingly rich if somewhat limited habitat for life, which on the lowest level manifests itself in an immense bloom of soda-loving algae, which can change its color from sky blue to jade green. The algae, in turn, support large numbers of fish.

Here, the waters of the lake and the rivers flowing into it appear white due to sun glint. A greenish algal bloom is present in the southern part of the lake.

Cahora Bassa Lake, Mozambique

March 28th, 2009 Category: Lakes

Cahora Bassa Lake, Mozambique - March 24th, 2009

Cahora Bassa Lake, Mozambique - March 24th, 2009

The Cahora Bassa lake is Africa’s fourth-largest artificial lake, situated in the Tete Province in Mozambique. Here, the western part of the lake appears tan from sediments, while the eastern part is green from phytoplankton growth, including various species of green and blue-green algae.

The lake has reached a maximum length and width of approximately 250 km and 38 km respectively, flooding an area of 2,700 km² with an average depth of 20.9 m.

In Africa, only Lake Volta in Ghana, Lake Kariba, on the Zambezi upstream of Cahora Bassa, and Egypt’s Aswan dam are bigger in terms of surface water.

The Cahora Bassa Dam system is the largest hydroelectric scheme in southern Africa with the powerhouse containing 5 x 415MW turbines.

It is one of the three major dams on the Zambezi river system, the others being Kariba and Itezhi-Tezhi (although the latter is not on the main stream of the Zambezi, but on its tributary the Kafue River).

Laguna Madre, Gulf of Mexico

March 23rd, 2009 Category: Snapshots

Laguna Madre, Gulf of Mexico - March 19th, 2009

Laguna Madre, Gulf of Mexico - March 19th, 2009

The Laguna Madre is the name of two long, shallow bays along the western coast of the Gulf of Mexico in the United States and Mexico; the two being separated by the outlet of the Rio Grande.

Meaning “mother lagoon” in Spanish, the Laguna Madre proper is 130 miles (209 km) long, the length of Padre Island. Its biological corridor, though, extends well into Mexico, to the mouth of the Río Soto la Marina in the state of Tamaulipas.

In the United States, the section visible here, Laguna Madre is separated from the Gulf of Mexico on the east by Padre Island, and bounded on the west by mainland Texas, and extends from Corpus Christi in the north to Port Isabel in the south.

In Mexico, Laguna Madre is separated from the Gulf of Mexico on the east by a number of barrier islands, including Barra Los Americanos, Barra Jesús María, and Barra Soto la Marina. It is bounded on the west by mainland Tamaulipas.

The Laguna Madre is very shallow, with an average depth of only 0.9 m. It is connected to the ocean by only two narrow inlets, so the tidal range – which is already minor in this part of the Gulf of Mexico – is negligible.

Oceanographically, the Laguna Madre is considered a hypersaline lagoon; this indicates that it is usually much saltier than the ocean, due to being nearly landlocked in a semiarid environment, and is one of only six hypersaline lagoons in the world. The Laguna Madre has been experiencing a persistent algal bloom (including drift algae) that may be partially caused by its hypersaline conditions, which favor algal growth.

Atmospheric effects are much more important than tides in its circulation; its weak currents generally follow the prevailing winds, and these winds can influence the water level by as much as a meter. Some such currents are visible to the South, their movements made visible by green algae.

The Coastline of Italy in and around the Gulf of Naples

March 8th, 2009 Category: Snapshots, Volcanoes

Naples, Italy - February 26th, 2009

Naples, Italy - February 26th, 2009

Both Italy’s western coastline along the Mediterranean Sea and its eastern shore along the Adriatic are visible here.

The Adriatic coast (above), only partially visible below the clouds, shows a green algal bloom. Further south, some of the peaks of the Apeninnes are capped by snow.

Below, the Mediterranean shoreline is very clear, with almost no clouds and only a slight algal bloom above the Gulf of Naples.

The islands of Ischia (left) and Capri (right) can be seen offshore. Just inland, Mount Vesuvius rises near the gulf, between Naples and Salerno.

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