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Black sea seagrasses
Marine Pollution Bulletin 46 (2003) 695–699 www.elsevier.com/locate/marpolbul
Focus
Black sea seagrasses Nataliya A. Milchakova a, Ronald C. Phillips a
b,*
Institute of Biology of Southern Seas, 2 Nakhimov Avenue, Sevastopol, 99011 Crimea, Ukraine b 22/5 Oktyabrskoi Revolutzii Avenue, apt. 306, Sevastopol, 99038 Crimea, Ukraine
Keywords: Black sea; Seagrasses; Zostera
1. Introduction Throughout geologic history, the Black Sea has been repeatedly disconnected from and reconnected to the Mediterranean Sea. About 18,000–20,000 years ago, the Black Sea became disconnected and the waters became substantially desalinated, resulting in an almost complete extinction of the marine flora which had come from the Mediterranean Sea (Zaitsev and Mamayev, 1997). A permanent connection formed as recently as 5000–7000 years ago, leading to an increased salinity of the Black Sea and an increased marine flora. About 1500–2000 years ago, the salinity of the seawater in the Black Sea approximated the present salinity (averaging 17–19%). The restricted connection of the Black Sea to the Mediterranean Sea has resulted in a number of special features: (1) near absence of seawater exchange; (2) highly reduced salinities; (3) changes in the components of seawater and salt balances are long-term, especially near the inflowing river mouths; (4) no tidal influences and considerable seiches; and, (5) fluctuations of the sea levels and upwelling and downwelling events in the nearshore seawaters (Zenkevich, 1963; Baidin and Kosarev, 1986; Matishov and Denisov, 1999). According to Gorelov (2001), almost the entire Black Sea displays oceanic conditions with closed nutrient turnovers and pelagic food chains. These areas are stable hydrologically and less influenced by external natural and anthropogenic impacts as compared to the estuarineshelf areas, which comprise 24% of the total basin area of the Black Sea (420,325 km2 ).
*
Corresponding author. E-mail address: [email protected] (R.C. Phillips).
In contrast, the estuarine-shelf areas are characterized by terrigenic nutrient influxes and benthic food chains prevailing. These latter areas are most vulnerable to the impact of external factors such as the thermal effect of the atmosphere and river influxes. Distinguishing hydrological characteristics of the estuarine-shelf water bodies of the Black Sea are their shallow (20 m) depths, marked seasonal and interannual fluctuations in water temperature and salinity, ice cover in winter, predominantly wind-induced seawater circulation, and rapid water exchange. Some authors claim that two trends have clearly been manifested: (1) disturbance of ecosystems provoked by anthropogenic pollution; and, (2) expansion of Atlantic species (Zaitsev and Alexandrov, 1998; Matishov and Denisov, 1999). The anthropogenic sources have been found to substantially reduce biological diversity and productivity of the Black Sea. These sources are especially damaging to traditional fisheries and spawning grounds which have vanished or are going out of existence, affecting also spawning migration routes which have been disturbed, and the homing instinct in fishes is extinguishing (Matishov and Denisov, 1999; Volovik et al., 1993). Zaitsev and Alexandrov (1998) stated that the Black Sea is widely considered as the most damaged sea on the planet. They also stated that since the 1950s, the volumes of nutrients and organic substances introduced onto the northwestern shelf of the Black Seas of the Ukraine coast by the Danube, Dnestr and Dnepr rivers have increased about 10-fold. The northwestern shelf has become the largest hypertrophic area in the entire Mediterranean Basin. The majority of investigators have stated that pollutants enter the Black Sea through river influx, and industrial, municipal and agricultural sewage, through navigation, dredging, dumping, atmospheric pollutants,
0025-326X/03/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0025-326X(02)00361-2
696
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699
and oil and gas extraction on the shelf. The extracted petroleum hydrocarbons (EPH) averages 50–150 mg/kg in the seawater, while that in the substrate is 50–3500 mg/kg (Patin, 1997). In the coastal ecosystems of the shallow bays and estuaries, seagrasses play the key part as the basic primary producers. The highest levels of primary productivity of seagrasses have been found in ecotones of fresh and brackish water areas, e.g., the northwestern Black Sea and in the Kerch Strait (Milchakova, 1999; Morozova-Vodyanitskaya, 1959; Pogrebnyak, 1965). Seagrasses give shelter to more than 70 species of invertebrates, 34 fishes, and 19 fish larvae, in which shrimps, scad, and perch predominate (Gordina and Beloivanenko, 1976; Makkaveeva, 1976). For these organisms, the seagrass communities are the feeding and nursery grounds. For a long time Zostera spp. in the Black Sea have been a traditional commercial item used in local agriculture as a forage additive and for winterizing barns for livestock. It has been proved in experiments that in milk cows whose fodder contained Z. marina, the daily milk yield increased by 15–20% and the fat content increased by 0.35%. The weight increase of sheep was 20–30% and
that of pigs was 10–15% (Lukina, 1986). Zostera spp. are also a valuable source of pectins (Ovodov et al., 1973). Being rich in hemicellulose and pectins, seagrasses may also be used as a gluing component in mixed fodder granulation and packaging.
2. Features of seagrasses in the black sea There are six species of vascular plants in the Black Sea. These include four species of seagrasses (Zostera marina, Z. noltii, Ruppia maritima, R. cirrhosa) and two species of seagrass associates (Potamogeton pectinatus, Zannichellia major). The first information regarding the distribution and ecology of the Black Sea bottom vegetation appeared at the beginning of the 20th century (Savenkov, 1910; Zernov, 1913). Later, details on the biology, community and population structure, and environmental impacts of the seagrasses are summarized in Kulikova and Kolesnikova (1976), Kulikova (1981); Milchakova (1988a,b, 1989a,b, 1990a,b,c, 1996, 1999); Sadogursky (1996), and others. Compared to the other southern Euro-Asian seas (Azov, Caspian, Aral), the Black Sea has the most ex-
Fig. 1. Map of seagrass distribution in the Black Sea at present. (1) Danube delta, Kiliya branch, (2) Dnestr coastal salt lake, (3) Tiligul coastal salt lake, (4) Beresan coastal salt lake, (5) Dnieper-Bug coastal salt lake, (6) Yagoplytsky Bay, (7) Tendrovsky Bay, (8) Dzharylgatsky Bay, (9) Donuzlav coastal salt lake, (10) Laspi Bay, (11) Yalta Bay, (12) Kara-Dag, (13) Feodosiya Bay, (14) Kerch Bay, (15) Kerch Srtait, (16) Anapa Bay, (17) Novorossisk Bay, (18) Gelendzhik Bay. ( ) Zostera marina, ( ) Z: noltii, ( ) Potamogeton pectinatus, j Ruppia cirrhosa, Zannichellia major.
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699
tensive seagrass communities. These occupy vast areas of the sea bottom, especially in the northwestern part of the Black Sea (Kalugina-Gutnik, 1975; Milchakova, 1988b, 1990c, 1999; Morozova-Vodyanitskaya, 1959; Ostrovchuk, 1973; Pogrebnyak, 1965; Sadogursky, 1996; Zaitsev and Alexandrov, 1998; Fig. 1). Between 1934–1937, communities of Z. marina were seriously impaired, possibly due to Labyrinthula. In the northwestern Black Sea, the devastation was almost catastrophic. Fortunately, Z. noltii, also found in shallow bays and coves, was not affected (Morozova-Vodyanitskaya, 1938).
2.1. Distribution and ecology Zostera spp. usually grow in the largest bays and gulfs, in coastal salt lakes and occasionally in river deltas, as in the Dunaisky Biosphere Reserve of the Danube River where the annual salinity is 0.3–14% (Milchakova and Alexandrov, 1999; Ostrovchuk, 1973; Pogrebnyak, 1965; Pogrebnyak et al., 1972). In other bays, such as Sevastopol Bay and the Kerch Strait, the salinity is higher, e.g., 17–19% (Zaitsev and Alexandrov, 1998). The total sea bottom occupied by Zostera spp. in the bays of the northwestern Black Sea is more than 950 km2 or 40% of the total area of all the bays (Milchakova, 1999; Fig. 1). There are no data regarding the growth of Zostera spp. on the shores of Georgia and Bulgaria. Near the Turkish coast, Z. noltii was found near Cape Sinop (Cirik and Cihangir, 1987). The shorelines along the
697
eastern and western coasts have smooth contours with few bays and inlets. Zostera spp. grow in pure and in mixed communities (algae and seagrass associates) on silty and sandy sediments, often with a mixture of shell grit. Depths of growth range from 0.2 to 17 m. One hundred and fifteen algal species were identified as growing in the Z. marina communities, and 62 species in the Z. noltii communities (Milchakova, 1999). The majority of algae are epiphytes encrusting leaves and only occasionally rhizomes and roots (Milchakova 1988a,b, 2000; Maslov et al., 1998). The average biomass of Z. marina is estimated to be 1–3 kg m 2 (wet weight) and reaches a maximum (5 kg m 2 ) at 1–3 m depths in summer with density averaging 988 shoots m 2 (Milchakova, 1999). In Z. noltii, biomass estimates varied from 0.5 to 2 kg m 2 (wet weight) and density from 680 to 4376 shoots m 2 (Table 1). Maxima were noted at depths to 1 m in summer. At greater depths, the density decreases. This species grows from 0.2 to 10 m deep. At 3–10 m, the species is found in patches. Though most investigators have acknowledged that the recent eutrophication of coastal ecosystems of the Black Sea has led to the degradation of key benthic and plankton communities (Zaitsev and Mamayev, 1997; Zaitsev and Alexandrov, 1998), the dynamics of the long-term changes observed in the Zostera spp. communities demonstrate that there are many localities where the relevant biomass estimates have increased 1.5–3 times (Table 2). This trend is seen in the bays of Sevastopol, in the Kerch Strait and Kerch Bay, in the
Table 1 Average biomass and density of Zostera spp. in the Black Sea Location
Depth (m)
Biomass (wet weight in g m 2 )
Density (shoots m 2 )
Reference
Karkinitsky Bay Z. marina Z. noltii
1 1
1109 745
105 680
Unpublished data YugNIRO, Kerch
Donuslav coastal salt lake Z. marina 2
836
218
Milchakova and Alexandrov (1999)
Kerch Strait, northern part Z. noltii 1
2231
4376
Unpublished Data (Milchakova)
Southern Part Z. noltii Z. marina
1 1
782 2008
3204 916
Sadogurskaya (2000) Unpublished Data (Milchakova)
Kerch Bay Z. marina Z. noltii Chernaya River, mouth Sevastopol Bay Kamysh-Burun Bay
3 1 1 3 3
3958 1104 2986 2819 5056
600 3332 1136 776 433
Maslov and Sadogursky (2000) Alexandrov (2000) Alexandrov (2000) Maslov and Sadogursky (2000)
Tamansky Bay Z. noltii
0.5
374
N/A
Maslov (personal communication)
698
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699
Table 2 Long-term changes in the biomass (B, g 2 ; wet weight) and density (D, shoots m 2 ) of Z. marina near Sevastopol and Kerch (Milchakova, 1996, 1988b, 1990a; Alexandrov, 2000; Maslov and Sadogursky, 2000) Location
Depth (m)
1981–1983
1994–1999
Laspi Bay
5
Kazachaya Bay
1
B––831 D––471 B––1466 D––200 B––1566 D––248 B––1569 D––252 B––1462 D––392 B––3335 D––724 B––1185 D––226 B––3161 D––988
B––2140 D––608 B––2416 D––312 B––2195 D––468 B––3223 D––936 B––3037 D––760 B––2822 D––940 B––3958 D––600 B––5700 D––467
3 Streletskaya Bay
2
Severnaya Bay
2
Holland Bay
2
Kerch Bay
3
Kerch Strait
3
Karkinitsky Gulf in which Zostera spp. communities have been recovering for some time, even in the dumping areas (Milchakova, 1999). It is likely that this increase in the yield of Zostera biomass is related to several factors, the most significant of which is the decrease in industrial pollution, coupled with an increased recreational use of the bays. 2.2. Protection In the Black Sea, seagrasses have been placed under protection in ten nature reserves under the State control of Ukraine and Romania (Leonenko et al., 1999). The largest of these are the Dunaisky Biosphere Reserve and the Chernomorsky National Reserve.
References Alexandrov, V.V., 2000. The evaluation of Zostera marina L. coenopopulations state in the Sevastopol region (the Black Sea). Ecologita Morya 52, 26–30 (in Russian). Cirik, S ß ., Cihangir, B., 1987. Karadeniz inceburun (Sinop) cevresi € niversitesi SU € zerine ilk notlar//Ege U bentik denizel bitkileri u € r€ € r€ U unleri Y€ uksek okulu: SU U unleri dergisi. 4 (13–14), 106–111. Gordina, A.D., Beloivanenko, T.T., 1976. The diversity of species and the numbers of fish eggs and larvae in Zostera and Phillophora biocenoses. Biologiya Morya 36, 40–50 (in Russian). Gorelov, V.K., 2001. Special features of formation of biota in inland seas of Russia. Biological grounding of the sustainable development of the coastal marine ecosystems. Abstract of the present of the International Conference, Murmansk, 2001, pp. 63–65 (in Russian). Kalugina-Gutnik, A.A., 1975. Phytobenthos of the Black Sea. Naukova Dumka. Kiev., 1–246 (in Russian). Kulikova, N.M., 1981. Eelgrass phytocenoses in the Black and Azov Seas. In: Commercial Algae and their Use. Moscow, VNIRO: 74– 80 (in Russian).
Kulikova, N.M., Kolesnikova, E.A., 1976. The associations of aquatic flowering plants in Sevastopol Bay. Biologiya Morya, Naukova Dumka 36, 17–25 (in Russian). Leonenko, V.B. et al., (Eds.), 1999. National Nature Reserves of Ukraine: A Guidebook. Kiev, pp. 1–240 (in Russian). Lukina, G.D., 1986. Polysaccharide seagrasses of the Black Sea: the chemical composition, structure, properties, and practical use. Synopsis of Ph.D. (chemistry) Thesis. Odessa. 1–22pp (in Russian). Makkaveeva, E.B., 1976. The dynamics of mass species populations of eelgrass biocenoses. Biologiya, Moriya Naukova, Dumka Kiev 36, 25–40 (in Russian). Maslov, I.I., Sadogursky, S.E., 2000. Ecological description of Zostera marina L. in Kerch Strait. Bull. Nikitsky Botanical Garden 76, 26– 27 (in Russian). Maslov, I.I., SarkinaI, S., Belich, T.V., Sadogursky, S.E., 1998. The annotated catalogue of algae and mushrooms of the nature reserve Care Martiyan. Nilitsky Botanical Garden Press, Yalta, pp. 1–33 (in Russian). Matishov, G.G., Denisov, V.V., 1999. Ecosystems and bioresources of the European seas of Russia in the late XXth-early XXI centuries. Murmansk., 1–127 (in Russian). Milchakova, N.A., 1988a. On the vital capacity of coenopopulations of Zostera marina and Z. noltii (Zosteraceae) in phytocenoses of the Kazachya Bay of the Black Sea. Botanical J. 73 (10), 143–148 (in Russian). Milchakova, N.A., 1988b. The composition and distribution of Zostera marina L. phytocenoses in some bays of the Black Sea. Plant Resources 1, 41–47 (in Russian). Milchakova, N.A., 1989a. Comparative description of the structure of Zostera spp. populations in the pure and mixed phytocenoses in the Kazachya Bay. Ecologiya Morya 31, 26–30 (in Russian). Milchakova, N.A., 1989b. Statistical analysis of the effect of granulometric composition of bottom sediments on the abundance and dimensional structure of populations of Zostera marina L. in the Black Sea. Ecologiya Morya 32, 59–63 (in Russian). Milchakova, N.A., 1990a. Vegetative reproduction of the eelgrass Zostera marina L. in Sevastopol Bay (Black Sea). Biologiya Morya 2, 51–57 (in Russian). Milchakova, N.A., 1990b. Sexual reproduction of the eelgrass Zostera marina L. in Sevastopol Bay of the Black Sea. Biologiya Morya 3, 45–51 (in Russian). Milchakova, N.A., 1990c. The composition and structures of the communities of two species of Zostera L. in Kerch Strait of the Black Sea. Plant Resources 3, 417–427 (in Russian). Milchakova, N.A., 1996. On the communities of Zannichellia major Boenn.. In the Kerch Strait of the Black Sea. Gydrobiol Zhurnal 32 (5), 14–18 (in Russian). Milchakova, N.A., 1999. On the status of seagrass communities in the Black Sea. Aquat. Bot. 65, 21–32. Milchakova, N.A., 2000. The dynamics of Zostera marina L. leaves in Sevastopol Bay. Biol. Mar. Medit. 7, 255–258. Milchakova, N.A., Alexandrov, V.V., 1999. Bottom vegetation at some sites of coastal salt lake Donuslav (the Black Sea). Ecologiya Morya 49, 68–72 (in Russian). Morozova-Vodyanitskaya, N.V., 1938. Epidemic disease of eelgrass in the Black Sea. Priroda 1, 94–98 (in Russian). Morozova-Vodyanitskaya, N.V., 1959. Aquatic plant associations in the Black Sea. Proc. Sevastopol Biol. Station 11, 3–28 (in Russian). Ostrovchuk, P.P., 1973. Bottom vegetation of the Karkinitsky Bight (Black Sea). Synopsis of Ph.D. (biology) Thesis. Odessa. 1–26 (in Russian). Ovodov, Yu.S., Korochan, V.D., Vasiliyev, B.K., Nedashkovskaya, G.N., 1973. About gel-forming properties of zosterin and its fragments. Chem. Natural Compds. 2, 267–269 (in Russian). Patin, S.A., 1997. Ecological Problems Encountered in Extracting Oil and Gas on the Shelf. VNIRO Press, Moscow (in Russian).
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699 Pogrebnyak, I.I., 1965. Bottom vegetation of the lagoons in the northeastern Black Sea and at the adjacent sea areas. Sunopsis of Doctoral Thesis, Odessa. pp. 1–46 (in Russian). Sadogurskaya, S.A., 2000. Zostera noltii Hornem. in the coastal sea water of the Kerch Strait near the Crimea. Bull. Nikitsky Botanical Garden 76, 4–35 (in Russian). Sadogursky, S.E., 1996. The ecofloristic description of seagrass phytocenoses along the Crimean coast. Synopsis of Ph.D. Thesis, Yalta, pp. 1–22 (in Russian). Savenkov, M.Y., 1910. Materials of the Study of Oikology and Morphology of Zostera spp. near Sevastopol. Pechatnik Publishing House, Kharkov, pp. 1–36 (in Russian).
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Zaitsev, Yu.P., Alexandrov, B.G., 1998. Black Sea Biological Diversity Ukraine. In: Black Sea Environmental Series 7. United Nations Publications, New York, p. 351. Zaitsev, Yu.P., Mamayev, V., 1997. Marine Biological Diversity in the Black Sea: A Study of Change and Decline. In: Black Sea Environmental Series 3. United Nations Publications, New York, pp. 1–208. Zenkevich, L.A., 1963. Biology of the Seas of the USSR. Acad. Nark. Publ, Moscow, pp. 1–739 (in Russian). Zernov, S.A., 1913. On studies of the life of the Black Sea. Reports of the imperial Academy of Sciences 32 (1), 1–299 (in Russian).
Focus
Black sea seagrasses Nataliya A. Milchakova a, Ronald C. Phillips a
b,*
Institute of Biology of Southern Seas, 2 Nakhimov Avenue, Sevastopol, 99011 Crimea, Ukraine b 22/5 Oktyabrskoi Revolutzii Avenue, apt. 306, Sevastopol, 99038 Crimea, Ukraine
Keywords: Black sea; Seagrasses; Zostera
1. Introduction Throughout geologic history, the Black Sea has been repeatedly disconnected from and reconnected to the Mediterranean Sea. About 18,000–20,000 years ago, the Black Sea became disconnected and the waters became substantially desalinated, resulting in an almost complete extinction of the marine flora which had come from the Mediterranean Sea (Zaitsev and Mamayev, 1997). A permanent connection formed as recently as 5000–7000 years ago, leading to an increased salinity of the Black Sea and an increased marine flora. About 1500–2000 years ago, the salinity of the seawater in the Black Sea approximated the present salinity (averaging 17–19%). The restricted connection of the Black Sea to the Mediterranean Sea has resulted in a number of special features: (1) near absence of seawater exchange; (2) highly reduced salinities; (3) changes in the components of seawater and salt balances are long-term, especially near the inflowing river mouths; (4) no tidal influences and considerable seiches; and, (5) fluctuations of the sea levels and upwelling and downwelling events in the nearshore seawaters (Zenkevich, 1963; Baidin and Kosarev, 1986; Matishov and Denisov, 1999). According to Gorelov (2001), almost the entire Black Sea displays oceanic conditions with closed nutrient turnovers and pelagic food chains. These areas are stable hydrologically and less influenced by external natural and anthropogenic impacts as compared to the estuarineshelf areas, which comprise 24% of the total basin area of the Black Sea (420,325 km2 ).
*
Corresponding author. E-mail address: [email protected] (R.C. Phillips).
In contrast, the estuarine-shelf areas are characterized by terrigenic nutrient influxes and benthic food chains prevailing. These latter areas are most vulnerable to the impact of external factors such as the thermal effect of the atmosphere and river influxes. Distinguishing hydrological characteristics of the estuarine-shelf water bodies of the Black Sea are their shallow (20 m) depths, marked seasonal and interannual fluctuations in water temperature and salinity, ice cover in winter, predominantly wind-induced seawater circulation, and rapid water exchange. Some authors claim that two trends have clearly been manifested: (1) disturbance of ecosystems provoked by anthropogenic pollution; and, (2) expansion of Atlantic species (Zaitsev and Alexandrov, 1998; Matishov and Denisov, 1999). The anthropogenic sources have been found to substantially reduce biological diversity and productivity of the Black Sea. These sources are especially damaging to traditional fisheries and spawning grounds which have vanished or are going out of existence, affecting also spawning migration routes which have been disturbed, and the homing instinct in fishes is extinguishing (Matishov and Denisov, 1999; Volovik et al., 1993). Zaitsev and Alexandrov (1998) stated that the Black Sea is widely considered as the most damaged sea on the planet. They also stated that since the 1950s, the volumes of nutrients and organic substances introduced onto the northwestern shelf of the Black Seas of the Ukraine coast by the Danube, Dnestr and Dnepr rivers have increased about 10-fold. The northwestern shelf has become the largest hypertrophic area in the entire Mediterranean Basin. The majority of investigators have stated that pollutants enter the Black Sea through river influx, and industrial, municipal and agricultural sewage, through navigation, dredging, dumping, atmospheric pollutants,
0025-326X/03/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0025-326X(02)00361-2
696
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699
and oil and gas extraction on the shelf. The extracted petroleum hydrocarbons (EPH) averages 50–150 mg/kg in the seawater, while that in the substrate is 50–3500 mg/kg (Patin, 1997). In the coastal ecosystems of the shallow bays and estuaries, seagrasses play the key part as the basic primary producers. The highest levels of primary productivity of seagrasses have been found in ecotones of fresh and brackish water areas, e.g., the northwestern Black Sea and in the Kerch Strait (Milchakova, 1999; Morozova-Vodyanitskaya, 1959; Pogrebnyak, 1965). Seagrasses give shelter to more than 70 species of invertebrates, 34 fishes, and 19 fish larvae, in which shrimps, scad, and perch predominate (Gordina and Beloivanenko, 1976; Makkaveeva, 1976). For these organisms, the seagrass communities are the feeding and nursery grounds. For a long time Zostera spp. in the Black Sea have been a traditional commercial item used in local agriculture as a forage additive and for winterizing barns for livestock. It has been proved in experiments that in milk cows whose fodder contained Z. marina, the daily milk yield increased by 15–20% and the fat content increased by 0.35%. The weight increase of sheep was 20–30% and
that of pigs was 10–15% (Lukina, 1986). Zostera spp. are also a valuable source of pectins (Ovodov et al., 1973). Being rich in hemicellulose and pectins, seagrasses may also be used as a gluing component in mixed fodder granulation and packaging.
2. Features of seagrasses in the black sea There are six species of vascular plants in the Black Sea. These include four species of seagrasses (Zostera marina, Z. noltii, Ruppia maritima, R. cirrhosa) and two species of seagrass associates (Potamogeton pectinatus, Zannichellia major). The first information regarding the distribution and ecology of the Black Sea bottom vegetation appeared at the beginning of the 20th century (Savenkov, 1910; Zernov, 1913). Later, details on the biology, community and population structure, and environmental impacts of the seagrasses are summarized in Kulikova and Kolesnikova (1976), Kulikova (1981); Milchakova (1988a,b, 1989a,b, 1990a,b,c, 1996, 1999); Sadogursky (1996), and others. Compared to the other southern Euro-Asian seas (Azov, Caspian, Aral), the Black Sea has the most ex-
Fig. 1. Map of seagrass distribution in the Black Sea at present. (1) Danube delta, Kiliya branch, (2) Dnestr coastal salt lake, (3) Tiligul coastal salt lake, (4) Beresan coastal salt lake, (5) Dnieper-Bug coastal salt lake, (6) Yagoplytsky Bay, (7) Tendrovsky Bay, (8) Dzharylgatsky Bay, (9) Donuzlav coastal salt lake, (10) Laspi Bay, (11) Yalta Bay, (12) Kara-Dag, (13) Feodosiya Bay, (14) Kerch Bay, (15) Kerch Srtait, (16) Anapa Bay, (17) Novorossisk Bay, (18) Gelendzhik Bay. ( ) Zostera marina, ( ) Z: noltii, ( ) Potamogeton pectinatus, j Ruppia cirrhosa, Zannichellia major.
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699
tensive seagrass communities. These occupy vast areas of the sea bottom, especially in the northwestern part of the Black Sea (Kalugina-Gutnik, 1975; Milchakova, 1988b, 1990c, 1999; Morozova-Vodyanitskaya, 1959; Ostrovchuk, 1973; Pogrebnyak, 1965; Sadogursky, 1996; Zaitsev and Alexandrov, 1998; Fig. 1). Between 1934–1937, communities of Z. marina were seriously impaired, possibly due to Labyrinthula. In the northwestern Black Sea, the devastation was almost catastrophic. Fortunately, Z. noltii, also found in shallow bays and coves, was not affected (Morozova-Vodyanitskaya, 1938).
2.1. Distribution and ecology Zostera spp. usually grow in the largest bays and gulfs, in coastal salt lakes and occasionally in river deltas, as in the Dunaisky Biosphere Reserve of the Danube River where the annual salinity is 0.3–14% (Milchakova and Alexandrov, 1999; Ostrovchuk, 1973; Pogrebnyak, 1965; Pogrebnyak et al., 1972). In other bays, such as Sevastopol Bay and the Kerch Strait, the salinity is higher, e.g., 17–19% (Zaitsev and Alexandrov, 1998). The total sea bottom occupied by Zostera spp. in the bays of the northwestern Black Sea is more than 950 km2 or 40% of the total area of all the bays (Milchakova, 1999; Fig. 1). There are no data regarding the growth of Zostera spp. on the shores of Georgia and Bulgaria. Near the Turkish coast, Z. noltii was found near Cape Sinop (Cirik and Cihangir, 1987). The shorelines along the
697
eastern and western coasts have smooth contours with few bays and inlets. Zostera spp. grow in pure and in mixed communities (algae and seagrass associates) on silty and sandy sediments, often with a mixture of shell grit. Depths of growth range from 0.2 to 17 m. One hundred and fifteen algal species were identified as growing in the Z. marina communities, and 62 species in the Z. noltii communities (Milchakova, 1999). The majority of algae are epiphytes encrusting leaves and only occasionally rhizomes and roots (Milchakova 1988a,b, 2000; Maslov et al., 1998). The average biomass of Z. marina is estimated to be 1–3 kg m 2 (wet weight) and reaches a maximum (5 kg m 2 ) at 1–3 m depths in summer with density averaging 988 shoots m 2 (Milchakova, 1999). In Z. noltii, biomass estimates varied from 0.5 to 2 kg m 2 (wet weight) and density from 680 to 4376 shoots m 2 (Table 1). Maxima were noted at depths to 1 m in summer. At greater depths, the density decreases. This species grows from 0.2 to 10 m deep. At 3–10 m, the species is found in patches. Though most investigators have acknowledged that the recent eutrophication of coastal ecosystems of the Black Sea has led to the degradation of key benthic and plankton communities (Zaitsev and Mamayev, 1997; Zaitsev and Alexandrov, 1998), the dynamics of the long-term changes observed in the Zostera spp. communities demonstrate that there are many localities where the relevant biomass estimates have increased 1.5–3 times (Table 2). This trend is seen in the bays of Sevastopol, in the Kerch Strait and Kerch Bay, in the
Table 1 Average biomass and density of Zostera spp. in the Black Sea Location
Depth (m)
Biomass (wet weight in g m 2 )
Density (shoots m 2 )
Reference
Karkinitsky Bay Z. marina Z. noltii
1 1
1109 745
105 680
Unpublished data YugNIRO, Kerch
Donuslav coastal salt lake Z. marina 2
836
218
Milchakova and Alexandrov (1999)
Kerch Strait, northern part Z. noltii 1
2231
4376
Unpublished Data (Milchakova)
Southern Part Z. noltii Z. marina
1 1
782 2008
3204 916
Sadogurskaya (2000) Unpublished Data (Milchakova)
Kerch Bay Z. marina Z. noltii Chernaya River, mouth Sevastopol Bay Kamysh-Burun Bay
3 1 1 3 3
3958 1104 2986 2819 5056
600 3332 1136 776 433
Maslov and Sadogursky (2000) Alexandrov (2000) Alexandrov (2000) Maslov and Sadogursky (2000)
Tamansky Bay Z. noltii
0.5
374
N/A
Maslov (personal communication)
698
N.A. Milchakova, R.C. Phillips / Marine Pollution Bulletin 46 (2003) 695–699
Table 2 Long-term changes in the biomass (B, g 2 ; wet weight) and density (D, shoots m 2 ) of Z. marina near Sevastopol and Kerch (Milchakova, 1996, 1988b, 1990a; Alexandrov, 2000; Maslov and Sadogursky, 2000) Location
Depth (m)
1981–1983
1994–1999
Laspi Bay
5
Kazachaya Bay
1
B––831 D––471 B––1466 D––200 B––1566 D––248 B––1569 D––252 B––1462 D––392 B––3335 D––724 B––1185 D––226 B––3161 D––988
B––2140 D––608 B––2416 D––312 B––2195 D––468 B––3223 D––936 B––3037 D––760 B––2822 D––940 B––3958 D––600 B––5700 D––467
3 Streletskaya Bay
2
Severnaya Bay
2
Holland Bay
2
Kerch Bay
3
Kerch Strait
3
Karkinitsky Gulf in which Zostera spp. communities have been recovering for some time, even in the dumping areas (Milchakova, 1999). It is likely that this increase in the yield of Zostera biomass is related to several factors, the most significant of which is the decrease in industrial pollution, coupled with an increased recreational use of the bays. 2.2. Protection In the Black Sea, seagrasses have been placed under protection in ten nature reserves under the State control of Ukraine and Romania (Leonenko et al., 1999). The largest of these are the Dunaisky Biosphere Reserve and the Chernomorsky National Reserve.
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