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Pictures of Red Tide

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Ozone LayerThe ozone layer is a layer in Earth's atmosphere which absorbs most of the Sun's UV

radiation. It contains relatively high concentrations of ozone (O3), although it is still very small

with regard to ordinary oxygen, and is less than ten parts per million, the average ozone

concentration in Earth's atmosphere being only about 0.6 parts per million. The ozone layer is

mainly found in the lower portion of the stratosphere from approximately 20 to 30 kilometres

(12 to 19 mi) above Earth, though the thickness varies seasonally and geographically.1

The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri

Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson,

who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure

stratospheric ozone from the ground. Between 1928 and 1958 Dobson established a worldwide

network of ozone monitoring stations, which continue to operate to this day. The "Dobson

unit", a convenient measure of the columnar density of ozone overhead, is named in his honor.

The ozone layer absorbs 9799% of the Sun's medium-frequency ultraviolet light (from

about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life

forms on Earth.

*Source: National Center for Atmospheric Research

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Algal BloomAn algal bloom is a rapid increase or accumulation in the population of algae (typically

microscopic) in an aquatic system. Algal blooms may occur in freshwater as well as marine

environments. Typically, only one or a small number of phytoplankton species are involved, and

some blooms may be recognized by discoloration of the water resulting from the high density

of pigmented cells. Although there is no officially recognized threshold level, algae can be

considered to be blooming at concentrations of hundreds to thousands of cells per milliliter,

depending on the severity. Algal bloom concentrations may reach millions of cells per milliliter.

Algal blooms are often green, but they can also be other colors such as yellow-brown or red,

depending on the species of algae.

Bright green blooms are a result of cyanobacteria (colloquially known as blue-green algae) such

as Microcystis. Blooms may also consist of macroalgal (non-phytoplanktonic) species. These

blooms are recognizable by large blades of algae that may wash up onto the shoreline.

Of particular note are harmful algal blooms (HABs), which are algal bloom events involving toxic

or otherwise harmful phytoplankton such as dinoflagellates of the genus Alexandrium and

Karenia, or diatoms of the genus Pseudo-nitzschia. Such blooms often take on a red or brown

hue and are known colloquially as red tides.

A harmful algal bloom (HAB) is an algal bloom that causes negative impacts to other

organisms via production of natural toxins, mechanical damage to other organisms, or by other

means. HABs are often associated with large-scale marine mortality events and have been

associated with various types of shellfish poisonings.

*source: "Harmful Algal Blooms: Red Tide: Home". www.cdc.gov. Archived from the

original on 27 August 2009. Retrieved 2009-08-23