**2. Biodiversity in the Caspian**

172 Ecosystems Biodiversity

The Caspian can be considered as divided into three parts, the northern, middle and southern parts. The border between the northern and middle parts runs along the edge of the North Caspian shelf (the Mangyshlak threshold), between Chechen Island (near the Terrace River mouth) and Cape Tiub-Karagan (at Fort Shevchenko). The border between the middle and southern parts runs from the Apsheron threshold connecting Zhiloi Island in the west to Cape Kuuli in the east (north of Turkmenbashi). The northern part covers about 25% of the total surface area, while the middle and southern parts cover around 37% each. However, the water volume in the northern part accounts for a mere 0.5%, while the volume in the middle part make up 33.9%, and in the southern part 65.6% of Caspian waters. These volumes are a reflection of the bathymetry of the Caspian. The northern part is very shallow, with average depths of less than 5m. In the middle part, the main feature is the Derbent Depression with depths of over 500m. The southern part includes the South Caspian

Approximately 130 large and small rivers flow into the Caspian, nearly all of which flow into the north or west coasts. The largest of these is the Volga River that drains an area of 1,400,000 sq. km and runs into the northern part of the Caspian. Over 90% of the inflowing freshwater is supplied by the 5 largest rivers: Volga – 241 km3, Kura – 13 km3, Terek – 8.5 km3, Ural – 8.1 km3 and Sulak 4 km3. The Iranian rivers and the smaller streams on the western shores supply the rest, since there are no permanent inflows on the eastern side. Apart from the extensive shallows of the northern part, the other two physical features that

characterize the Caspian are the Volga and the Kara Bogaz Gol gulf.

Depression with its deepest point being 1025m below the surface (plate 2).

Plate 2. Caspian Sea riparian countries

The biodiversity of the Caspian aquatic environment is a product of thousands of years of isolation from the world's oceans, allowing ample time for speciation. The biological diversity of the Caspian and its coastal zone makes the region one of the most valuable ecosystems in the world. The Caspian harbors some 147 species of fish, 450 species, varieties, or forms of phytoplankton, 87 species of algae, and 315 species of zooplankton. One of the most important features of the Caspian's biodiversity is the relatively high level of endemism among its fauna. Recent studies suggest the actual endemism may be even higher than what is already known. To date, there are 331 known endemic species in the Caspian. They are represented by the following: UNDP, www.caspianenvironment.org/ newsite/Data-MajorDocuments.htm.


Tran boundary Diagnostic Analysis for the Caspian Sea, Caspian Environment Programme. September 2002. Baku. www.caspianenvironment.org/newsite/Data-MajorDocuments.htm.

Table 1. Known endemic species in the Caspian Sea.

The decline in bioresources and biodiversity are closely linked through food chains and feeding patterns. A disturbance in the phytoplankton-zooplankton and benthic communities caused by invasive species for instance may impact species at higher trophic levels, such as sturgeon or seals. With the invasion of ML (*Mnemiopsis leidyi*) as well as introductions of other species the naturally occurring food web may have undergone or be undergoing potentially significant disruptions particular when under concurrent stresses.

The sturgeon species existed 200 million years ago at the same time as dinosaurs and can therefore be called living fossils. At that time sturgeon inhabited many ancient seas. Later on in the process of evolution, possibly due to competition with bony fish species, the

*Mnemiopsis leidyi* Invasion and Biodiversity Changes in the Caspian Sea 175

3. The presence of POPs (in particular pesticides) and PTS from exploitation of oil in some parts of the Caspian Sea is a major source of concern, especially their accumulation in the long-lived species – mollusks, seals, and sturgeons (UNDP,

In the early 1980s, the comb jelly *Mnemiopsis leidyi*, a ctenophore that normally resides off the eastern United States, was accidentally introduced into the Black Sea via ballast waters from cargo ships. This voracious zooplanktonic predator (with extremely high rates of reproduction and growth) reached enormous biomass levels (a few hundreds million tons for the entire basin!) devastating the pelagic (i.e. in water column) food chain in the entire Black Sea basin by the end of 1980s (Vinogradov et al., 1989). Inevitably, such high biomass of this comb jelly consumed a considerable fraction of the zooplankton that had been the food for pelagic fish and their larvae before its arrival. One of the dramatic consequences of the *M. leidyi* invasion was the sharp drop (from about 630,000 tons in 1988 to steadily 150,000 tons in 1991) in commercial catches of planktivorous fish (mainly the anchovy Engraulis encrasicolus L.) in the Black Sea (Kideys 1994; Prodanov et al., 1997). The yearly economical damage to the fisheries sector alone were estimated to be about 250-500 million USD during this period. Although merely one or two researchers pointed out the overfishing as the major cause, the concurrent sharp decrease in zooplankton quantity from different regions in the Black Sea (Kovalev et al., 1998; Gubanova et al., 2002; Gordina et al., 2004) was a conclusive evidence. Indeed one would expect much higher quantities of zooplankton (due to decreased predation) at low levels of planktivorous fish occurence. The decreased levels of the pelagic fish must have also affected the abundance of top predators (several species of predator fish as well as the three species of dolphins) in the Black Sea. Although there are no systematic data on dolphins, they were noted to be scarcer by

*M. leidyi* did not only affected the quantity of animals but also of plant organisms, known as phytoplankton. These (mainly) photosythetic organisms are the food for zooplankton. Due to decreased levels of zooplankton, phytoplankton had a chance to over-grow in the Black Sea (Yunev et al., 2002) during the peak period in *M. leidyi* quantity. Such increase was deleterious particularly for some shallow regions in the Black Sea ecosystem (e.g. off

The situation in the Black Sea has been one of the most striking examples in marine bioinvasion history. Due to scale of the problem, UNEP intervened and gathered international experts in Geneva in 1994, for investigating methods for solving this problem (GESAMP, 1997). The futility of physical and chemical methods for this problem were noted and therefore, biological control seemed the only workable remedy. And, based on the literature knowledge of feeding specificity, another ctenophore species (*Beroe ovata*) rose as the best candidate for dealing with *M. leidyi* problem. Indeed, B. ovata reported feeding only on other ctenophore species (Kremer and Nixon 1976), most notably on *M. leidyi*. However, scientists from the Geneva meeting could not stress on using a new predator species for

www.caspianenvironment.org/newsite/Data-MajorDocuments.htm).

occur within them must be protected.

**3.** *Mnemiopsis leidyi* **problem in the Caspian** 

fishermen and mariners at this period.

Danube River) already badly suffering from eutrophication.

to have impacted the Caspian seal, for whom Kilka are an important food source. Clearly, to restore depleted fisheries, ecosystems and the processes and interactions that

sturgeons started to become extinct but managed to survive in the Caspian Sea. This gigantic lake contains more than 90% of the world resources of sturgeon. Furthermore, the Caspian Sea is also home to many other rare species of crustaceans and mollusks (Birstein et al., 1968).

Due to its unique and diverse habitats, the Caspian Sea has become home to many rare species of flora and fauna. In connection with an increase of the Caspian Sea level during the period of 1994 – 1996, habitats for rare species of aquatic vegetation have drastically decreased. This can be attributed to a general lack of seeding material in newly formed coastal lagoons and water bodies (Aladin and Plotnikov, 2004).

Many rare and endemic plant species of Russia are associated with the intra-zonal communities of the Volga delta and riparian forests of the Samur River delta as well as to the Sarykum barkhan which is a unique refuge for flora adapted to the loose sands of the ancient Central Asian Deserts. The principal limiting factors to successful establishment of plant species are hydrological imbalances within the surrounding deltas, water pollution, and various land reclamation activities. The water level change within the Caspian Sea is an indirect reason for which plants may not get established. This affects aquatic plants of the Volga delta, such as: *Aldrovanda veiculosa* and *Nelumbo caspica*. About 11 plant species are found in the Samur River delta, of which some form a unique liana forest that dates back to the Tertiary period.

Different factors are involved in decline of biodiversity in the Caspian Sea.


sturgeons started to become extinct but managed to survive in the Caspian Sea. This gigantic lake contains more than 90% of the world resources of sturgeon. Furthermore, the Caspian Sea is also home to many other rare species of crustaceans and mollusks (Birstein

Due to its unique and diverse habitats, the Caspian Sea has become home to many rare species of flora and fauna. In connection with an increase of the Caspian Sea level during the period of 1994 – 1996, habitats for rare species of aquatic vegetation have drastically decreased. This can be attributed to a general lack of seeding material in newly formed

Many rare and endemic plant species of Russia are associated with the intra-zonal communities of the Volga delta and riparian forests of the Samur River delta as well as to the Sarykum barkhan which is a unique refuge for flora adapted to the loose sands of the ancient Central Asian Deserts. The principal limiting factors to successful establishment of plant species are hydrological imbalances within the surrounding deltas, water pollution, and various land reclamation activities. The water level change within the Caspian Sea is an indirect reason for which plants may not get established. This affects aquatic plants of the Volga delta, such as: *Aldrovanda veiculosa* and *Nelumbo caspica*. About 11 plant species are found in the Samur River delta, of which some form a unique liana forest that dates back to

1. One of the factors contributing to depleted fisheries and ecosystem resilience is the separation of anadromous fish from their natal river systems in the Caspian. Reduced access to sturgeon spawning sites began in the 1930s with the construction of irrigation weirs, followed by the construction of large dams on the Kura River in the 1950s, the Volga River in the 1960s, and the Sefidrud River in the early 1970s. In the past 50 years, anadromous fish migrations have been blocked to up to 90% of natural spawning grounds on rivers like the Volga and the Kura. As summarized above, anadromous fish such as sturgeon, salmon or herring develop genetically distinct sub-populations in response to environmental variability. Dams without fish passages block migration up rivers for spawners and down rivers for fingerlings. This loss of connectivity and natural selection cannot be replaced by hatcheries and has had the effect of drastically reducing the biological diversity of the Caspian's fish species and populations. It has led to reduced numbers of fish overall and reduced numbers of genetically distinct

2. Invasive species are also factors thought to be contributing to ecosystem stress, loss of biodiversity and depleted fisheries. Invasive species have been shown the world over to have direct and indirect impacts on many ecosystem components, including productive fisheries and the economy. Ecosystems often contain cascading feeding interactions that respond in unpredictable ways to introductions. Invasive species affect individuals, populations, and assemblages of populations in the ecosystems where they occur. One assemblage-level impact is a substantial shift in relative abundances, resulting in declines and losses among native fishes, for example. This is widely believed to have happened in the Caspian with respect to the native species of fish called the Kilka among others. *Mnemiopsis lediyi*, an invasive species of jellyfish, is thought to have affected the cascading feeding interactions that the Kilka relied upon, possibly causing the Kilka populations to decline dramatically, which in turn is thought

coastal lagoons and water bodies (Aladin and Plotnikov, 2004).

Different factors are involved in decline of biodiversity in the Caspian Sea.

populations of fish (Aladin and Plotnikov, 2004).

et al., 1968).

the Tertiary period.

to have impacted the Caspian seal, for whom Kilka are an important food source. Clearly, to restore depleted fisheries, ecosystems and the processes and interactions that occur within them must be protected.

3. The presence of POPs (in particular pesticides) and PTS from exploitation of oil in some parts of the Caspian Sea is a major source of concern, especially their accumulation in the long-lived species – mollusks, seals, and sturgeons (UNDP, www.caspianenvironment.org/newsite/Data-MajorDocuments.htm).
