Introduction to Applied Ecology

Introduction to Applied Ecology

Black Sea Marine Life

Prepared by: Oksana Harbuziuk

Instructor: Vicky Meretsky

2004

Introduction.History.The Black Sea has a long history of developing from a salty TethysSea 50-60 million years ago through a series of brackish to salty basins and into a mildly salty Black Sea nowadays. The TethysSea was connecting Atlantic and PacificOceans 50-60 million years ago. Then, as a result of tectonic movements, the TethysSea became isolated from Pacific Ocean and later from Atlantic. Disconnected from salty waters, the Sea gradually became freshwater body divided into a few brackish basins. One of them – called Sarmatic – was stretching where the Black, Azov, Caspian, and AralSeas are these days. The basin shrunk to the size of the Black Sea and was changing its saltiness status while acquiring and loosing connection to the Atlantic Ocean through the Mediterranean Sea and accepting melting waters from glaciers. Finally, after being a freshwater Neoeuxinian Sea-Lake with freshwater species during the last Wurm glaciation, the basin established connection to the Mediterranean Sea about 7,500 years ago (seismic waves and radiocarbon dating methods, Kerr 1998) and was rather rapidly filled with salty water (HSE 2004); the water level was rising about 15cm a day (Kerr 1998). Gradual salinisation of the Black Sea to the present level was accompanied by extinction of freshwater species and intrusion of Mediterranean saltwater species (Andrusoff 1893, HSE 2004).

Physics and chemistry.Due to its rare inner location and generous freshwater river supply, the Black Sea has approximately half the salinity of the open ocean: 18 ‰ as opposed to 35‰. The peculiarity is due to generous freshwater supply by rivers (the Danube, the Dnieper, the Don, the Dniester, etc.) and precipitation over sea surface (1.5 times less the river supply) as well as narrowness of Bosphorus connection to the salty water source.

The Black Sea is also the largest in the world anoxic basin. Owing to its specific pycnocline/density distribution, only the upper 200 m contain enough oxygen for nonbacterial marine life. Then a thin hypoxic layer follows that contains small quantities of oxygen and hydrogen sulfide (H2S), the compounds that cannot coexist in large quantities. All the rest of the water down to the sea bottom is generally anoxic because of presence of hydrogen sulfide (H2S). Andrusoff (1893) and Science (1891) allude to decomposition of large quantity of extinct species 7,500 years ago, mentioned in the first paragraph, as the source of hydrogen sulfide. Since salty Mediterranean water enters the Black Sea and being denser accumulates at the bottom, vertical circulation is precluded. The amassed hydrogen sulfide stays at the bottom dissolved in water. The resource of hydrogen sulfide is build up by decay of flora and fauna descending from the upper inhabited layer (Andrusoff 1893).

Pollution.At the beginning of the 20th century, the shallow AzovSea (the deepest place is 9 m) was a celebration of diversity of marine life(GIWA 2004). The 20th century introducedmany changes. In the Black Sea basin, the 25 commercially significant fish species in 1950s and 1960s are reduced to only five in 1990s. Nutrient enrichment – eutrophication – is causing algal blooms, creating favorable conditions for invading species, and reducing biodiversity by changing water conditions for sensitive species. Nitrogen and phosphorus are the major misbalanced macroelements. The major sources of nitrogen eutrophication are the Danube (about 50%), precipitation on the Black Sea surface, and the Don with smaller rivers carrying waters to the AzovSea. Most important phosphorus contributors are the Danube (about 50%), precipitation on the Black Sea surface, the Dnieper, and the Don with smaller rivers of the Azov region (GIWA 2004). Eutrophication is the cause of the growing hypoxic zone in the northwestern shelf of the Black Sea near Romanian shore (GIWA 2004).

Oil pollution (with the Danube contributing almost 50%, HSE 2004) and sewage/wastewater discharge are the next most significant contaminants. Data on oil discharge from ballast water by ships and on microbial contagion of the beach waters are not systematically collected and sometimes not readily publicly available. Increase in acute water borne diseases such as hepatitis and cholera is caused by infected drinking water. Heavy metals, radionuclides, pesticides and polychlorinated biphenyls (PCBs) are not considered to be of crucial magnitude (HSE 2004).

Discussion.Microorganisms.The deep sea waters of the anoxic region (below 200 m) are inhabited by low-light adapted bacteria. Karl (1978) describes the distribution of microorganisms across the water column. According to his studies, the hypoxic layer between the oxygenated and anoxic waters contains a “vertically restricted layer (20-30m) of metabolically active cells.” The lower anoxic region is characterized by microorganism concentration that is 5 to 10 times higher than in the seas with oxygen presence. Microbial biomass increases with sea depth; and upper layer of sediments contains four orders more of microbial biomass than the adjacent deep water column. The author also describes the possible role of microorganisms in pyrite (FeS2) formation from iron monosulfide through greigite (Fe3S4) stage. Overmann etal. (1992) describe a brown sulfur bacterium that is adapted to extremely low-light environment (0.0005% of the surface light) and uses bacteriochlorophyl e for photosynthetic oxidation. The Clorobium phaeobacteriodes was compared to twelve other purple and green sulfur bacteria; the brown bacterium outperforms them by 175% increase in light-gathering pigment and low energy needs.

Viruses.There are two types of viruses in the Black Sea – allochthonic and authochthonic. Allochthonic are mostly brought with wastewater or sewage discharge. Some diseases caused by contaminated water like cholera were documented after 1991 in the south of Ukraine. The authorities had to introduce some measures on local scale including building municipal facilities treating urban wastewater or sewage. NASU (1998) has undertaken a local (Sevastopol) five-year study of viruses on Crimean sea shore. Serological and virological tests of water, sediments, and mollusks Mytilus have been done. The scientists have revealed the following viruses in their samples: poliovirus (causing poliomyelitis), virus of hepatitis, rotavirus (severe diarrhea among children), reovirus (mild infections of upper respiratory and gastiointestinal tract of humans), adenovirus (respiratory illness), and COX-1&2 (fever, inflammation, and pain in various tissues). Cox-1, hepatitis, rota-, and adenovirus were identified in 30 percent of mollusk communities in quantities capable of causing illness for people eating them. Mutations that allow the virus to adapt to new (marine) environment may be caused by ultraviolet radiation, chemicals, or other factors.

The scientists have also registered a significant decrease in authochthonic viruses from 5.4*105 virions average in March 1995 to 6*104 virions average in May 1996, which constitutes an almost tenfold decrease. The authors do not mention what is responsible for this helpful change. Also, impact of viruses called bacteriophages (literally “eaters of bacteria”) on bacteria was studied. The authors assess that 30 to 60 percent of mortality in the sea water organisms is caused by virus infection; and 5 to 9 percent of bacteria are infected by phages.

Plankton.Phytoplankton photosynthesize their food from sunlight and are 0.002 to 1 mm in size. They include cyanobacteria, diatoms, dinoflagellates (have two flagella), Radiolaria (having glassy geometric skeletons) with only one species for the Black Sea(NASU 1998) and Ciliata (dense hairlike covering – “eyelash”). Zooplankton has some members that spend their whole life in the floating community called holoplankton and some joining members for the eggs and larva stage called meroplankton. Holoplankton include pelagic sea snails and slugs, krill; copepods (like small crabs) are most abundant multicellular animals of the sea, 184 common species and 244 endemic species in the Black Sea (NASU 1998); salps (semitransparent barrel-like marine animals, the most advanced marine invertebrates), some marine worms, and jellyfish. Meroplankton embrace eggs and larva of starfish, sea urchins, benthic sea snails and slugs, octopus (eight-tentacle carnivorous mollusk), lobsters, crabs, marine worms, and reef fish (AMO 2004).

The studies (NASU 1998) indicate that the oxygenated layer of the Black Sea contains ten times more zooplankton biomass than central regions of tropical Atlantic and about five times more than zooplankton-rich western and eastern Atlantic and Mediterranean Sea. Due to eutrophication, phytoplankton numbers started to increase in early 1980s. There have been recorded 80 species of holoplankton in 1963 for the open sea and 150 species for the area including fresh water in 1984.

Seagrass and fishes.There are six seagrass species listed for the Black Sea (NASU 1998). These include common eelgrass (Zostera marina), dwarf eelgrass (Zostera noltii), fennel pondweed, horned pondweed, and two species of ditch-grass family (beaked tasselweed and spiral tasselweed). Eelgrasses are among the most abundant seagrasses, forming underwater meadow communities. They cover rocky and sandy beds of the shallow seashore and were estimated at 350,000 and 50,000 tons correspondingly in 1980s. Construction of harbors and exploitation (used as fertilizer; for filling pillows and mattresses; as wool substitute; for packing eggs, furniture and other delicate objects) have reduced the eelgrasses number since then (UNEP 1999). Thickets of eelgrass host epiphytic communities of red, pink, and green macroalgae; from about 20 species off shore to about 80 species in enclosed coastal water (NASU 1998). Mollusks are abundant in seagrasses; and they are a spawning ground for many fishes. The most common are grass goby, deep-smoted pipefish, horse pipefish, strait-nosed pipefish, grey wrasse, spotted wrasse, red mullet, grey mullet, picarel, and sea horse (Popov 1931, UNEP 1999). Some eelgrasses are preserved in two nature reserves (NASU 1998).

Rocks and stones covered with brown algae Cystoseira have almost disappeared in early 1970s, the first shock being from cold winter with freezing sea water and floating ice (80% of the stock was damaged). Cystoseira rocky underbrush used to house multiple blenny species (sphinx blenny, Montagu’s blenny, redspeckled blenny, Tompot blenny, and triple-fin blenny), clingfish species (two-spotted clingfish, shore clingfish, and Connemara clingfish), black scorpion fish, peacock wrasse, and goby species (flat-head goby, giant goby, black goby, and tubenose goby) (Popov 1931, UNEP 1999).

Further from the seashore behind Zostera thickets (0-10 m deep) and Cystoseira brown algae (down to 10-20 m) communities, Popov (1931) identifies sand and shell biocenoses with their characteristic fishes, followed by mud with mollusk Mytilus (Mediterranean mussel), and then the mud with Modiola phaseolina till the end of continental platform.

Migratory fishes include the following families: Scombridae (Atlantic mackerel, bluefin tuna, Atlantic bonito), Mugilidae (mullets), Mullidae (goatfishes), Clupeidae (herrings, shads, sardines), Engraulidae (anchovies), Acipenceridae (Starry sturgeon, white sturgeon, Russian sturgeon), Pristipomatidae (sargos), and Sparidae (porgies). They stay near the south coast of the Black sea in winter and migrate to the northern coast and to the AzovSea in the summer (Popov 1931). Some migrate to the Mediterranean or the MarmoraSea (Atlantic mackerel) for winter and spawning (Galtsof 1924).

Reptiles.There are only two species of reptiles in the Black Sea and four species of mammals. Reptiles include Dice water snake (Natrix tesselata) and European pond turtle (Emys orbicularis).

The water snake inhabits coastal brackish waters. The snake travels with DanubeRiver to ZmiyinyiIsland that outstands from the Black Sea continental platform 37 km off the coastal line. Also found along coast in Turkey. The snake is usually 1 to 1.3 m long, though happens to grow to 2 m sometimes; stained green to almost black in color. The snake is not poisonous; feeds on small bottom fish, mostly gobies; though frogs, tadpoles, and salamanders also occur in the diet.

The European pond turtle lives in the warm coastal waters with places to sunbath. Predominantly, the turtle reaches 25 cm in size. The reproductive age is between 8 and 10; some individuals live for 120 years. This generalist enjoys fish, mollusks, amphibians, insects, and earthworms as well as water plants in the diet.

Like the water snake above, the turtle hibernates October through April, hidden in the bottom mud; the snake prefers dry holes in the shore. Both species have a breeding season May through beginning of June and lay eggs in June or July. Female turtles lay their eggs in a clutch of 3 to 16 at times quite far from water; the water snakes prefers hollow places under leaves of stones for her nest with 10-25 eggs. Both species hatch in September, though the turtles can wait through the winter and appear next spring if the summer was cold. The European pond turtles are protected in most countries of their residence (Krumphanzl 2001, Huurne 2004).

Mammals.The Black Seahas few mammal species. Mediterranean monk seal, common dolphin, harbor porpoise, and bottlenose dolphin constitute the community.

The monk seal is dim brown in color with occasional white tummy patches. They inhabit underwater caves and like quiet sea beaches. The diet consists of sea perch, sea carp, fish from themullet family; and cuttlefish, squid, octopus, and chambered nautilus from phylum Mollusca. The seals attain sexual maturity at the age of four; and babies are born year round after eleven monthsof gestation (UNEP 1999). The estimate is 300-500 individuals; there was a severe decline incurred after more than 60 percent of the Cote des Phoques monk seal population died from some epidemic in the Western Sahara. The Mediterranean monk seal is registered as “critically endangered” with the International Union for the Conservation of Nature and Natural Resources (IUCN) and is protected from killing or live catching for trade by Convention on International Trade in Endangered Species (CITES) (The Monachus Guardian 1999).

The common dolphin is of a mixed color with black, gray, white and yellow patches. The animals populate offshore waters with sporadic coastal visits when forming schools and following small fish migrations. The diet consists of small pelagic fish like anchovy, sprat, and pipefish. The common dolphin females grow to 1.5-1.7 m, rarely 2 m; the males being about 20 cm longer; live for 25-30 years. Sexual maturity is attained at 2-4 years for females and 3-4 for males. Calves appear in the summer after 10-11 months of gestation. The young dolphins feed on mother’s milk for about half year. The species is the most numerous mammalian in the Black Sea; the population in Romanian waters is about 600 to 800 individuals; scientific studies with the species statistics are in agenda today. Natural calamities are lung nematode and undisclosed morbillivirus. Common dolphin is protected by CITES and ACCOBAMS (Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and Contiguous Atlantic Area) as well as Berne and Bonn conventions and enlisted in the IUCN and Ukrainian Red Books (UNEP 1999).

Harbor porpoise is the shortest-living Black Sea cetacean: 7-8 years, 15 being the longest. This small animal (1.3-1.5 m, with a maximum of 1.8 m) weighs only about 30 kg and enjoys coastal waters along the Crimean peninsula and Turkish seashore; does not mind semifresh waters. The diet of harbor porpoise consists of both benthic fishes like gobies and small pelagic species (anchovy). Sexual maturity and calving duration is similar to that of the common dolphin, though porpoise female is more productive bringing a new calf almost yearly. Ship traffic, fishermen exploitation, and water pollution are disturbing critical habitats; large die-off from the gas-platform explosion in the AzovSea occurred in 1982. Natural disasters include early ice formation on the AzovSea (porpoise migrate to the Azov and the MarmoraSea) and lungworm infection. The species is extensively protected with conventions like the common dolphin (UNEP 1999).

Finally, bottlenose dolphin is the largest regional marine mammal that grows up to 3.3 m. They live all over the continental shelf of the Black Sea. Attain sexual maturity at 5 to 12 years and are less fertile than the common dolphin. The species enjoy pelagic and benthic fish like herring, whiting; grey, red, and striped mullets; turbot, anchovy, and bonito. Used to be the less numerous cetacean in the Black Sea; exact numbers are not known. Critical habitat and protection are identical to that of the common dolphin (UNEP 1999).

Conclusion.Biodiversity.The Black Sea was rich in biodiversity earlier in the 20th century. About 60 percent of its fishes are of Mediterranean origin; 20 percent are fresh water species; and about 16 fish species are “pontocaspian relicts” (GIWA 2004). According to Zaitsev and Mamaev (1997) as in GIWA (2004) a total of 3774 marine species from gastropoda to mammalia were identified in the Black Sea. Still, the biodiversity of the sea was adversely affected during the 20th century. More than 60 species of plants and animals are listed as endangered or extinct (University of Delaware 2003).