Caspian Sea 2011

2010

Golden algae are represented by only two species. Both species belong to the genus Di- nobryon. While both species are found in all parts of the Caspian Sea, they are considered to be rather rare. Diatoms are dominant in number and in terms of biomass in almost all parts of the Caspian Sea. There are 275 species and forms belonging to 62 genera, with nine species endemic to the Cas- pian Sea. Of the total, 25 species have not been found for the past 20 years. Due to species revi- sions, the taxonomy of 40 species has changed in recent years. The composition of species in the North and South Caspian Sea differs. As many as 104 species in the North Caspian Sea are not found in the South Caspian Sea, and 118 species in the South Caspian Sea are not found in the North Caspian Sea. About 70 species are distrib- uted throughout the Caspian Sea and these are the most abundant in number. Diatoms produce about 40% of the total organic matter present in the North Caspian Sea, and produce up to 98% of organic matter in the South Caspian Sea. For the most part, this organic matter is produced by only one species - Rhizosolenia [=Pseudosolenia] calcar-avis, introduced unintentionally, alongside the ac- climatisation of two species of mullet (Karpevich, 1975). I t was very abundant in the 1960s, and though its numbers have dropped somewhat, it is still dominant in all areas of the Caspian Sea. Brown algae are small in number and in terms of diversity. Only five species are known in the South Caspian Sea and two of these are endemic. Red algae are not abundant, mostly inhabiting the South Caspian Sea, and only a few species found in the Central Caspian Sea and one spe- cies in the Ural Furrow in the North Caspian Sea. In total, 23 species have been identified in the Caspian Sea, six of which are endemic. Brown and red algae are small metaphytas. Their pres- ence is very significant at depths between 10 and 20 meters, where high plants are absent and where red algae dominate.

by 33%. The most abundant species are Diatoms (Bacillariophyta), green algae (Chlorophyta) and blue-green algae (Cyanophycota). Numbers of species of red algae, brown algae, pyrrophytas and golden algae are small. Most algae species are phytoplankton, but there are also some mi- crophytobentos and periphyton algae species, and some species are small individual plants. Phytoplankton is the primary producer of organic matter in the Caspian Sea, totalling from 200 to 230 million tonnes annually. Blue-green algae in the Caspian Sea are rep- resented by freshwater, brackish and marine spe- cies. There are 131 species and 19 forms of blue- green algae belonging to 29 genera. However, about 30 of these species have not been found during the past 20 years. Most of these species inhabit the North Caspian Sea, while only two in- habit the South Caspian Sea. Blue-green algae can be found in phytoplankton and in one-cell membranes on the water surface and on coating rock in tide zones – and in periphyton. Blue-green algae are most abundant in August and Septem- ber. The composition of the various species dif- fers in the south and north portions of the Cas- pian Sea: in the north there are 88 species and forms, and 84 in the south – only 21 species are present in both areas. Dinoflagellates are represented by only 35 spe- cies. However, these species are highly significant as they provide the main food source for many zo- oplankton species. The species composition tends to be very uniform. In the North Caspian Sea, pyr- rophitas are not abundant; in the past, however, before the introduction of exotic diatoms, pyrro- phytas dominated both the south and middle sec- tors of the Caspian Sea. Since the 1960s, this dom- inance has diminished. Over the last few years, however, pyrrophytas have increased in number in the South Caspian Sea. These algae have chloro- plasts of different shapes and colors – olive, brown, yellow, red – even blue and colorless. Green is the one color that is not prevalent in pyrrophytas. The most common species in the Caspian Sea are from the genera Protocentrum and Prorocentrum.

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