Some Ecological Characteristics of the Caspian Sea
It is located in an inland depression on the
border of Europe and Asia, as the largest enclosed
sea in the world, with a catchment area of 3.5 million km
2
. The Caspian Sea is reported to have got
separated for the first time from the Black Sea in the early Pliocene. The primary marine fauna was
therefore partly eliminated and partly modified. The typical brackish-water Caspian fauna formed
then and has persisted till now. It can be divided into the northern, shallow part (5-6 metres deep)
covering 80 000 km
2
, a middle part (average 190 m) covering 138 000 km
2
and a southern part (up to
1 025 m) covering 168 400 km
2
. The northern shoreline is strongly undulating and includes the deltas
of the Volga, Ural, Emba and Sagiz rivers. The middle and south Caspian shorelines vary, ranging
from narrow beaches fronting seacliffs to broad sandy regions. In the south relatively smooth
western coast is composed of small grained sands and silt. Another important feature of the Caspian
is its changing water level. It has significant effect on its biodiversity. The level is below that of the
World Ocean, highest - 22 m has been reported to have reached nearly 38 000 years ago, but may
have been as low as - 64 m. In the last century the level fluctuated around - 26.2 m, later decreasing
to - 29.0 m. Some regression have been observed from 1995 0nwards , the level currently stands
around the -28.8 m. Almost 130 rivers of various sizes drain into the Caspian with an annual input of
about 300 km
3
.
The cold arctic air, moist sea air masses forming over the Atlantic Ocean, dry
continental air masses from Kazakhstan, and warm air masses coming from the Mediterranean Sea
and Iran determine the climate of teh Caspian.
Biodiversity Status in the Caspian
The Caspian is a productive sea with 22.7 million tonnes of primary production of organic
carbon a year in the northern parts, 50.9 in the middle and 41 million tonnes in the south. Its coastal
zone shows diversified range of habitats from vast river systems to extensive wetlands makes it one
of the most valuable ecosystems in the world. Many endemic taxa are present here showing high
endemism together with representatives from almost all major groups on earth. Its diverse flora and
fauna shows high natural productivity. It lies at the crossing of migration routes of millions of
migrating birds and offers refuge for a number of rare and endangered species.
Most important
element of the fauna is the sturgeon. Several indigenous species are found in the middle Caspian
because of its relative stability over time, salinity regime fluctuating between 0.12 to 10 percent and
central location. consequently the highest number of endemic species are found there. However, the
North Caspian This part shows the greatest diversity of habitats and species. The Volga River system
is accepted as the ancient route for the penetration of Arctic and Mediterranean species, still found
in the Caspian. One comes across different ecological niches with high species diversity. Nearly 379
species from 13 different classes of animals contribute in the bottom macrofauna. In the north the
benthic fauna is less diverse than in the middle and south. There are approximately 76-126 species of
fish belonging to 17 families. Two species, the flounders and a mullet are the introduced aliens. The
origin of pipefish and a sand-smelt is unknown. Most diverse are the families of goby, carp, herring
and sturgeon. The local rare endangered species are; Caspian lamprey, spiny sturgeon, Volga
herring, Caspian salmon, and gfew others. The four primary groups of fishes are; sea , anadromous,
semi-migratory and river fishes. Out of a total of 466 bird species, 120 are nesting, 68 are wintering
and 278 are migratory or summer residents. Marine
birds include gulls, cormorants, pelicans and
flamingoes, congregating along the coast. The Caspian seal is the only mammal within the aquatic
fauna. Thousands of Caspian seals have died during the last two decades, most probably due to
canine distemper virus infection. Nearly 450 taxa of phytoplankton have been recorded, all a mix of
marine, brackish and freshwater forms. A total of 315 zooplankton taxa have been are reported as
the representatives of Arctic, Mediterranean and endemics. The algal taxa are represented by
approximately 64 species from green, red and brown algae. The The new algal species introductions
from the Black Sea is recorded as to have started with the opening of the Volga-Don canal in 1954.
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Potential Biosources of the Caspian and Impact of Pollutants on Food Web
The fish populations have suffered significant changes during the past 5 decades due to
human activities, fisheries and habitat alterations. Traditional Caspian sturgeon is well known for its
valuable caviar. The Caspian held more than 85 percent of the world’s sturgeon nearly 40
years back,
but has decreased dramatically from 30 000 tonnes to approximately 5000 tonnes.
The level of contamination in the sea has increased during the last 4 decades. The reason
being anthropogenic activities because, the entire drainage basin contributes towards this. Nearly 80
percent of the total load of contaminants directly enters through river flow, atmospheric input,
groundwater flow and direct input. Major sources are, untreated waste from industry and agriculture
along the Volga River, offshore oil and gas production, processing, extraction and transportation, and
marine dumping. All these drastically effect the biological processes in particular growth of fish. The
dam
constructions have already changed the hydrology of the Caspian. These have seriously effected
the biodiversity, in particular a reduction in the spawning grounds for some fishes.
The delta
vegetation too has changed. There has been a loss of reeds, cat's tail and bushes. This loss has lead
to a loss of aquatic and coastal fauna. Several anadromous and semi-migratory species have been
deprived of their natural spawning grounds.
Invasive species
Their
damaging effects are increased by the near isolation of Caspian. Species reach here through
the Volga-Don canal, but cannot leave as easily, predators too cannot be easily introduced. This
places the Caspian at risk. This invader feeds on fish eggs and larvae. It will have significant effect on
the fish population in the Caspian. The comb jellyfish can survive the salinity levels
of Caspian, it was
firts recorded here In 1999, presumably after introduction through ballast waters of oil tankers. Its
large blooms are observed in the northern and central parts of the Caspian.
Almost no specific data about the timing, routes, and means of species migrations. Most likely,
migration occurred as a result of direct or indirect human activities because the Caspian Sea lies
along the ancient caravan routes of the Silk Road that connected Europe and Asia. Some species are
weeds of agricultural fields:
Sonchus arvensis, Convolvulus arvensis, Solanum nigrum, Chenopodium
album, Acroptilon repens, etc. These species likely entered the territory with grain and fodder as well
as during agricultural development of the region in the 20th century. For the two
Xanthium species
that originated from the Americas,
X. strumarium is widespread and usually is in waterways in the
Caspian region.
Xanthium spinosum initially was rare after introduction, but it is becoming more
abundant now in disturbed habitats. Along
the Caspian coast, this species prefers well drained
habitats along roads, wetlands, and canals. In addition,
Amaranthus albus and
A. retroflexus have
invasive features. Anthropogenic disturbance complicate natural ecological processes, and new alien
species have the potential to reach the area through accompanying increases in transportation,
trade, and economic activity. Monitoring of alien plants is an important task for the future.
Discussion
The diversity of inland waters and habitats is a comlex subject because of several constraints,
as well as differences in classification and terminology. Their temporal aspects of ecosystem diversity
are especially difficult to quantify (Revenga, 2003). The climate changes in future are expected to
lead to an increase in the temperatures together with a modification in the precipitation regimes.
This will lead to an increase in the sea level. Inland waters will get their share from all these changes
however, they are not considered adequately in many of these scenarios.
The occurrence, structure,
pattern, process, and function of these waters will undergo variations by the changes in
temperatures, hydrology, biogeochemical cycles, and evapotranspiration. All these will lead to a shift
in the species distribution, altering community structures and species interactions. These changes
will contribute to the changes in carbon storage, trace gas emission, biogeochemical variation, and
changes in species composition .
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