The Europaen Commission The Commission on the Protection of the Black Sea Against Pollution
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Report Contents

Preface Chapter 1A Chapter 1B Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12
List of Tables List of Figures

State of Environment Report 2001 - 2006/7

Chief Editor, Prof. Dr. Temel Oguz, Institute of Marine Sciences, Middle East Technical University, Erdemli, Turkey

Chapter 7 - State of Macrophytobenthos

State of the Environment of the Black Sea - 2009

CHAPTER 7 THE STATE OF MACROPHYTOBENTHOS

G. Minicheva

Odessa Branch, Institute of Biology of the Southern Seas, NASU, Odessa, Ukraine

O. V. Maximova, N. A. Moruchkova, U. V. Simakova

P.P.Shirshov Institute of Oceanology RAS, Moscow, Russian Federation

A. Sburlea

National Institute for marine research and development ?Grigore Antipa?, Constanta, Romania,

K. Dencheva

Institute of Oceanology, Bulgarian Academy of Sciences, Varna, Bulgaria,

Y. Aktan

?Istanbul University, Faculty of Fisheries, Istanbul, Turkey

M. Sezgin

Sinop University, Faculty of Fisheries, Sinop, Turkey

7.1. Introduction

The Black Sea bottom algoflora is the impoverished derivative of the Mediterranean one. The species list today comprised 80 Chlorophyta, 76 Phaeophyceae and 169 Rhodophyta (Milchakova, 2002; 2003a,b, 2007). Many of them, however, have either disappeared completely or impoverished, whereas some others flourished during the last decades due to the severe impact of eutrophication on the bottom phytocoenosis. The most well-known sign of the transformations in macrophytobenthos community was the loss of Phyllophora in the region of Zernov?s Phyllophora Field of the northwestern Black Sea. The drastic decrease of macrophytes diversity and almost total disappearance of perennial algae were among the most important changes that had occurred as a result of natural and man-made factors. Given the importance of macroalgae as food and refuge for animals, as well as source of external metabolites and oxygen, their decline affected the entire benthos life. The present chapter reviews the recent changes took place in the macrophytobethos community and assesses its recent status in different coastal environments of the Black Sea

7.2. Ukrainian shelf area

More than 70% of species diversity of macroalgae as well as six species of higher flowering plants (Zostera marina L., Z. noltii Hornem., Zannichellia major Boenn. Ex Reichenb, Ruppia cirrhosa Grande, R. maritime L., Potamogeton pectinatus L., and highly developed algae from the phylum Charophyta) have been present in the northwestern sector of the Black Sea, including the Crimean coastline. The region extending from the Danube Delta (Zmeiny Island) to Tarkhankut Cape 45?N latitude and the Crimean coastal zone are two particular areas with different floristic composition and structural-functional organization of macrophytobenthos communities. The former is affected by the runoff from large rivers (Danube, Dniester, Bug, and Dnepr) and includes numerous limans and shallow water bays. The second region is characterized by a large amount of hard substrate and embayments suitable for settling of macrophytes. Higher salinity and lower level of eutrophication also support richer species diversity. While ~50% of species composition was made up of representatives of red algae in both areas, lower salinity and higher eutrophication in the northwestern part prevailed the development of green algae and to a lesser extent the brown algae (Table 7. 1 and Fig. 7.1).

Table 7.1. Number of macroalgae species (underlined) and its percentage (bold) in the total floristic composition of the northwestern coastal waters of the Black Sea (Milchakova, 2007; Eremenko, Minicheva, Kosenko, 2006).

Area

Taxonomic phyla

Total

Chlorophyta

(Green algae)

Phaeophyta

(Brown algae)

Rhodophyta

(Red algae)

Northwestern coast

54 29

45 24

87? 47

186*? 57**

Crimean coast

56 24

62 27

115 49

233 71

* - number of species

** - percentage of Black Sea floristic composition

Fig. 7.1. Photos for the brown algae Cystoseira barbata (left), Desmarestia viridis (center) and the red algae Polysiphonia elongata (right).

The long-term changes in the species composition of algae of the Zernov?s Phyllophora Field are summarized in Table 7.2. During the 1970s of intense eutrophication, the greatest change in the phytobenthos structure of the northwestern shelf was the disappearance of the brown algae Cystoseira barbata (Fig. 7.1) from the coastal phytocenose of the Danube ? Dnepr interfluves. However, other brown algae of arctic-boreal flora, Desmarestia viridis (Fig. 7.1) was introduced into this area in the 1990s that then spread rapidly and became the dominant species in the cold periods of the year along the Odessa coast within the next 5-6 years. Massive covering of D. viridis thallus with dimensions of 30-50 cm have been often observed along the beaches in March ? April. Its specific surface of the population index [(S/W)p], that indicates the amount of active thalloma surface per 1 kilogram mass of the macrophyte population,? reached 70 m2 kg -1. Besides, the early 1990s of the northwestern Black Sea experienced intense developments of red algae Polysiphonia sanguinea and Pylaiella littoralis with high (S/W)p index values of 78.3 ? 1.9 m2 kg -1 and 140.2 ? 5.1 m2 kg -1, respectively.

Table 7.2. Long term changes in the species composition of algae of the Zernov Phyllophora Field.

Species

1964*

1986*

1989*

2004

2006

2008

Bryopsis plumosa (Huds.) C.Ag.

+

-

-

-

+

-

Cladophora albida (Nees) K?tz.

+

+

+

-

-

+

Ulva rigida Ag.

-

-

+

+

-

-

Rhizoclonium tortuosum (Dillw.) K?tz.

-

+

-

-

-

-

Ulothrix implexa Kutz.

-

-

+

Cladostephus spongiosus f .verticillatus

+

-

-

+

-

-

Feldmannia irregularis (K?tz.) Hamel.

+

-

-

+

-

-

E. siliculosus (Dillw.) Lyngb.

-

-

+

+

-

-

Ralfsia verrucosa (Aresch.) J. Ag.

-

-

-

+

-

-

Stilophora rhizodes (Ehrh.) J. Ag.

-

-

-

+

-

+

S. saxatilis (Kuck.) Sauv.

+

-

-

+

-

-

Spermatochnus paradoxus (Roth.) K?tz.

-

-

-

-

-

+

Rhodophyta

-

-

-

Rhodochorton purpureum (Lightf.) Rosevn.

-

-

+

+

-

-

Callithamnion corymbosum (Sm.) Lyngb.

-

-

-

+

+

-

C. deslonchampii Chauv.ex Duby

-

-

-

+

-

-

Lithothamnion sp.

-

+

+

+

-

-

Lophosiphonia obscura (Ag.) Falkenb.

+

-

-

+

-

+

Peyssonnelia rubra (Grev.) J. Ag.

-

+

+

+

+

+

Ph. crispa (Huds.)P.S.Dixon

+

+

+

+

+

+

Polysiphonia denudata (Dillw.) K?tz.

+

-

+

+

+

+

P. sanguinea (Ag.) Zanard.

-

+

+

31

8

12

* Kalugina-Gutnik and Evstegneeva (1993) and Milchakova (2003a), Tsarenko, Wasser and Nevo (2006).

Table 7.3. Variability of morphological structure of thallus for some common macroalgae of the Ukrainian coast.

Structural element

Specific surface? (S/W)p, m2·kg-1

Cystoseira

barbata

Polysiphonia

elongata

Desmarestia

?viridis

Main axis (stem)

? 2.78 ? 0.17

??? 3.70 ? 0.02

? 13.62 ? 0.36

Lateral branches, 1-st order

? 5.84 ? 0.71

??? 4.60 ? 0.11

? 23.90 ? 0.49

Lateral branches, 2-nd order

11.87 ? 0.45

??? 6.10 ? 0.10

? 37.98 ? 0.80

Lateral branches, 3-rd order

14.82 ? 0.52

? 18.80 ? 0.49

? 68.68 ? 2.35

Apical? branches?

18.42 ? 0.82

? 88.50 ? 2.18

102.75 ? 2.78

Total for thallus

11.62 ? 0.42

? 26.88 ? 3.21

? 76.72 ? 3.56

S/W variability for thallus (%)

135

315

103

In the 1990s, expansion of P. elongata of the Polysiphonia genus was also recorded in the northwestern part of the Black Sea. P. elongata was constantly observed in communities of the Crimean coastal zone in eutrophic and oligotrophic reserve areas (Karadag, Tarkhankut, and Utrish) as well as along the northwestern coast (Milchakova and Kireeva, 2000). Both thick main branches and very thin posterior branches with two-fold greater (S/W)p indices of P. elongata with respect to Cystoseira and Phyllophora (Table 7.3) provided a high intensity metabolic processes and adaptation to diverse conditions in eutrophic and oligotrophic waters at depths up to 50 m, and thus successfully taking over the vacant ecological nich in the mid-1990s.

Severe eutrophication in the northwestern Black Sea has therefore led to a distinct dynamics of structural-functional organization of macrophyte communities. The species with (S/W)p < 15 m? kg-1 ceased to develop due to the increasing level of eutrophication during the early 1970s and 1980s (Minicheva, 1998), (Fıg. 7.1A). In this period Cystoseira was replaced by algal communities of the genus Ceramium, Cladophora, Enteromorpha and the total phytobenthos biomass declined from 3.0 kg∙m-2 to 1.0-1.5 kg∙m-2.

Fig. 7.1A.? Dynamics of changes in surface index (SIcm) and average value of specific surface (S/W) of species composition of phytobenthos of the Danube-Dnepr interfluves.

The end of the 1980s and the early 1990s may be considered as the period of stabilization. This was followed by a significant reduction in the productivity of opportunistic algae species after the mid-1990s that suggested weakening of the eutrophication process. In the autumn 2004, July 2006 and March 2008 surveys, some of the extinct species of Zernov?s Phyllophora field have been emerged again. The finely branched, ecologically active P. sanguinea began to develop in communities of Phyllophora crispa = Phyllophora nervosa with (S/W)p = 10.4 m2 kg -1 and Phyllophora truncata = Phyllophora brodiaei with (S/W)p = 11.5 m2 kg -1, forming up to 20-30%? of the vegetative biomass in the summer period. The expansion of P. elongata at the beginning of the present decade may be considered an intermediate stage in the restoration process, the length of which depends on the rate of decrease of the eutrophication and the climatic conditions. If the present day tendency persists, it is quite possible to expect restoration of the Cystoseira community in the Danube-Dnepr interfluves and more favorable conditions for development of Phyllophora on the northwestern shelf. Table 7.4 summarizes four stages in the transformation of the macrophytobenthos of northwestern Black Sea.

The decreasing trends in average macrophyte biomass and production (Fig. 7.2) also support restoration of the system along the northwestern coast. The sharp peaks in 2002-2003 suggest the impact of anomalous climatic conditions. The winter of 2002-2003 was the coldest one in the last 50 years (Adobovskiy and Bolshakov, 2004) which altered the seasonal dynamics of macrophytes. The Odessa coastal zone was characterized by an intense development of winter species D. viridis, Punctaria latifolia Grev., and Ectocarpus confervoides (Roth.) Le Jolis until the mid-June 2003 but dominated by Enteromorpha intestinalis (L) Link and Cladophora laetevirens (Dillw.) Kutz in June- July 2003. The data therefore suggest that such anomalous future climatic conditions may introduce important biological changes in addition to the effects of eutrophication processes.

The stages shown in Table 7.4 for the changes of the coastal phytobenthos structure coincided with the changes in Cystoseira and Phyllophora phytocoenoses in the less eutrophic offshore waters of the northwestern shelf as well. They comprised the background state from the late 1950s to the early 1970s; degradation state from the mid-1970s to the late 1980s; negative changes from the late 1980s to the early 1990s; partial restoration state towards the 1950s after the mid-1990s (Milchakova, 1999). At present, restoration of Cystoseira phytocoenoses has been limited to the shallow water (1-3 m) coastal zone in open areas (Cape Aya, Cape Sarych, Karadag) and in embayments and bays (Sevastopol Bay, Karkinitsky Bay) as evident by their increasing species diversity and shares of edificatory species (large, perennial species). Cystoseira and Phyllophora occupied 7.42 and 1.62 km? area with stocks of 9200 and 993 tones, respectively, in the Sevastopol Bay (Milchakova, 2003b). The stocks of Gracillaria verrucosa (Huds.) Papenf., G. dura (Ag.) J. Ag. in Kasachya and Novorossiskay embayments of the Crimean coast also made up 55 and 42 tonnes, respectively (Mironova, 2005).

An improvement of ecological conditions can also be seen in seaweed distributions in deep waters. For instance, congestions of green filamentous algae Cladophora sericea (Huds.) Kutz. were found in the southwest Crimea shelf at the depth range of 40-100 meters in spring 2004 (Boltachev and Milchakova, 2004). The green lamellar algae Ulva rigida Ag. was recorded at 35-60 meter depth range in autumn 2005. Even the coastal ecosystem of the Danube-Dnepr interfluve which has been greatly subject to eutrophication started producing some macrophyte development at depths from 5-7 to 12-14 m in 2005-2007.

Table 7.4. The periods of alteration of community structural-functional organization for the macrophytobenthos of northwestern part of the Black Sea.

Stage

Period

Main characteristics

Pre-eutrophication state

Before the

1960s

Dominant of communities ? a large perennial brown alga Cystoseira barbata with a low specific area (S/W ? 12 m??kg-1). Multilayer complex communities with average biomass of 3-5 kg?m-?.

Intensified

Eutrophication

From the early 1970s to the 1980s

Species with S/W lower than 15 m??kg-1 ceased developing C. barbata succeeded the algal community of the genus Ceramium, Cladophora, Enteromorpha. The phytobenthos biomass fell to 1.0-1.5 kg?m-?. The S/W index of the floristic algae composition increased more than two-folds.

Immobility

Mid-1990s

Mass development of species of aliens and previously rare species (Desmarestia viridis, Polysiphonia sunguinea) with S/W ~ 70 m??kg-1.

Decreasing

Eutrophication

The present decade

The red algae Polysiphonia elongata (S/W ? 26.88 m??kg-1) has intensively widened its range, as a step towards restoration of the macrophytobenthos structure.

Fig. 7.2. Annually dynamic of biomass and production of macrophytes community of Danube-Dnepr interfluves.

7.3. Romanian shelf area

Long term changes (1950-2005): Macrophytes in the Romanian coast until the 1970s comprised 154 species (47 Chlorophyta species, 2 Xanthophyta, 30 Phaeophyta, and 79 Rhodophyta) that have been identified as early as 1935 by Celan (1935). They decreased gradually to 86 species in 1970s (Bavaru, 1981), 55 in the 1980s and 31 in the 1990s as depicted in Table 7. 5.

Table 7.5. Number of macroalgal species at the Romanian coast, between 1977 and 2005 by different authors

Phyllum

1977(1)

1976-1995(2)

1996-2005(3)

Chlorophyta (green algae)

31

22

16

Phaeophyta (brown algae)

14

9

5

Rhodophyta (red algae)

41

24

10

Total

86

55

31

Data sources: (1) Bavaru (1981), (2) Vasiliu (1984), (3) Bologa and Sava (2006).??????

The cold winter of 1971-1972 represented a special situation in which drifting ice mechanically destroyed benthic vegetation up to 2-3 m of depth. 80% of the loss of the perennial brown algae Cystoseira barbata stocks was the result of this particular phenomenon. Silt and nutrients from coastal human activities aggravated the unsuccessful macrophytes stocks rehabilitation. Cystoseira continued to be present only in the form of small aggregations mostly in the southern part of the Romanian shore because of the weaker influence of the Danube River in this region. Epiphytic flora and associated fauna also decreased, and as a result perennial algae damaged considerably. The almost complete disappearance of extended belts of Cystoseira had important ecological implications in terms of forming as a substratum and shelter for various other epiphytic macrophytes and animals, especially fish. The disappearance of numerous brown and red algae was mainly related to the depletion of those Cystoseira fields. Phyllophora is a perennial algae, dominant in the famous ?Zernov?s field? (Skolka, 1956), nowadays being present only as scattered islands in the northern Constanta area.

Considerable diminution of phanerogames Zostera marina and Z. nolti (eelgrass) was also observed in former decades. In the last 30 years the standing stock of eelgrass has decreased tenfold in shallow water. Eelgrass served as a favourable biotope for many species of invertebrates and fish. The main reason for the degradation of Zostera communities was the mobilizing of silt when dredging in the coastal zone. These impoverishments in macrophyte community were noticed in many rocky bottom areas (Celan, 1977; Celan & Bavaru, 1973, 1978; Skolka et al., 1980; Bavaru, 1970, 1981; Bavaru and Vasiliu, 1985; Bologa, 1989; Sava et al., 2003) and led to the present decrease of biodiversity in the north-western Black Sea (Bologa, 2002; Bologa et al., 1995).

Hard substratum, earlier populated by slow developing brown alga Cystoseira, was then covered by short life cycle species with fast growth. Most frequent species are Enteromorpha, Cladophora and Ceramium, followed by Ulva, Bryopsis and Callithamnion but their biomass is not comparable with high biomass of Cystoseira in the last decades (Sava, 1999). Most obvious feature of macrophytes community in 1990s was low number of species at the Romanian shore, but they could produce high biomasses, some genera (Enteromorpha, Cladophora, Ceramium) covered 80% of the bottom (Bologa, 1989). An average of 6 kg/m2 wet biomass has been measured in 2004, proportion of green algae being higher in the north, red algae predominating towards the south of the Romanian coast (Sburlea and Mircea, 2006).

Due to large amount of suspended particles and plankton, the transparency of sea water was significantly decreased in 2005 compared to 1980s. The position of the compensation depth changed as a result, and bottom seaweeds growing deeper than 7 to 8 m became shaded (Bologa and Sava, 2006). The latter accounted for the large decline of macrophytes, in spite of the high nutrients levels. The changes of the ecosystem and community structure led to the replacement of some phytocoenoses by others. The consequence was a shift in the seasonal and multiannual dynamics of the algal communities.

As a result of biological pollution, the exotic and toxic species Desmarestia (Phaeophyta) has been observed along the Romanian shore in 2004 and 2005. First recorded in 1992, this particular species has already populated hard substrates of the Odessa harbour and is considered toxic for the neighbouring algae. At present, the rehabilitation of macrophytes community is delayed by secondary eutrophication and human activities such as harbour constructions, industry, and tourism.

With respect to the categories proposed by the World Conservation Union (IUCN) and considering national concerns regarding endangered species, a comprehensive red list of extinct and endangered, rare and insufficiently known benthic macrophytes from the Romanian Black Sea sector has been compiled (Bologa and Bavaru, 1998/99). The list comprised 24 extinct and endangered species (6 Chlorophyta, 6 Phaeophyta, and 12 Rhodophyta), 42 rare species (13 Chlorophyta, 2 Xanthophyta, 9 Phaeophyta, 18 Rhodophyta) and 4 insufficiently known species (1 Phaeophyta, 3 Rhodophyta).

Peculiarity of macrophytobenthos during 1990-2005: Along the Romanian Black Sea shore, the compact, discontinuous and variable rocky bottom characterizes the supra-, medio-, and infralittoral between Cape Midia (440 20? N) and Vama Veche (430 45? N). This substratum constitutes the most varied environment of the benthic domain. During the decades, this benthic zone has shrunk to a narrow inshore strip at the depth of 5-7 m that comprised the only region with sufficient light penetrating within the water column for photosyntesis (Sava, 1999).

The inventory of benthic macrophytes along the Romanian shore in the last decade presents 33 species (Bologa and Sava, 2006): 16 Chlorophyta, 10 Rhodophyta, 5 Phaeophyta and 2 Phanerogama. Usually, Enteromorpha species are mixed with species of Cladophora. Occasionally Bryopsis plumosa (in the warm season) and Entocladia viridis (endophyte in the cellular membranes of Ceramium species) have been observed. After the green algae belt, starting with low depths up to 8 to 9 m were covered by the species of Ceramium. They occupy almost all substrata, contributing with Enteromorpha, to the physiognomy of the present vegetation. Polysiphonia, Callithamnion and Porphyra constituted other common species at lower quantities during various seasons of the year.

There is, however, a clear quantitative and qualitative difference between the macrophyte community of the northern and southern littoral zones of the Romanian coastline (Fig. 7.3). Reduced hard substratum suitable for macrophytes development and more intense pollution caused much lower macrophyte community along the northern Romanian littoral zone. Suspensions in large quantities negatively affected light penetration in the water body and seed germination.

Half of macrophytes species encountered on the Romanian shore at 2 to 4 m depth exist also as epiphytes on Cystoseira developing interstitial spaces suitable for zoobenthos settlement and creating a complex trophic chain (Sburlea and Bologa, 2006). Considering this influence on benthic communities, Cystoseira is ranked as key species.

Fig. 7.3. Location of sampling stations along the Romanian Black Sea coast during 2000-2005 observations (left) and quantitative proportion of red and green algae along the Romanian Black Sea shore (right).

Some species that were considered as disappeared until recently such as Lomentaria clavellosa (Rhodophyta), were found recently in ?2 Mai?Vama Veche? Marine Reservation area, thus making this species easier to monitor and protect. A few thalli of exotic brown alga Desmarestia was observed as stranded to shore but it is not known if they were carried by coastal currents from the north or it was growing on Romanian shelf (Environmental State Report - NIMRD).

Nowadays biomass values are much lower compared with previous published data. High values of macrophyte biomass were found at depths of 2-3 m where there was still enough light and the physico-chemical conditions were relatively good (Sava, 1999). Hard substratum, earlier populated by community of brown alga Cystoseira, is now covered by Enteromorpha, Cladophora and Ceramium, seasonal macrophytes with short life cycle. Their mass development led to a homogenization of benthic communities on extended areas but their biomass is not comparable with high biomass of Cystoseira (Sava, 1999). Starting with 1990, in spite of diminished number of species, a trend of quantitative recovery of Chlorophyta (green algae) and Rhodophyta (red algae) that are more tolerant to eutrophication has been registered on several beaches between Mamaia (in spite of sandy bottom) and Vama Veche.

Fig. 7.4. Annual evolution of biomass (g∙m-2) of green and red algae along the Romanian littoral between 1996 and 2005 (Bologa and Sava, 2006).

The research carried out during 2000-2005 at seven sites between Constanta and 2 Mai both in warm and cold seasons suggested that the new algal communities consisted of very small number of species of mostly green, red algae and brown algae. The perennial associations of the past have declined and the substratum previously populated by Cystoseira is now covered by opportunistic species with a short life cycle and rapid growth. The evolution of biomass since 2000 (Fig. 7.4) showed that green algae were dominant and comprised by the species belonging to the genera Ulva, Enteromorpha and Cladophora that develop all year round, together with Ulothrix and Urospora that develop only during the cold season (spring and autumn). Its maximum development took place in 2003 (25,000 g/m2), but similar values were also registered in 2002 (22,310 g/m2) and 2004 (23,410 g/m2). In 2005, a significant decrease of Chlorophyta biomass was evident; its total value (15,581 g/m2) was almost half of the 2003 value. The red algae acquired the maximum biomass (21,722 g/m2) in 2004 with slight differences to previous years, whereas its biomass reduced more than half of its value in 2000. They were dominated by the species of Ceramium, found on rocky bottom during the entire year due to its high capacity of both asexual and sexual reproduction. During spring, Porphyra and sometimes Polysiphonia and Callithamnion contributed to the total red algae biomass. The latter two species were found in appreciable quantities in samples only in the warm season. The reduction in biomass of both green and red algae in 2005 could be related to the improvement of the state of the ecosystem along the Romanian shore and could have beneficial consequences on the whole algal vegetation.

7.4. Bulgarian shelf area

The long-term observations in the Varna Bay region indicated a decreasing trend of macrophyte species in general and of oligosaprobic species in particular in response to increased level of eutrophication (Dimitrova, 1978; 1996) as summarized in Tables 7.6 and 7.7. The total loss of macrophyte species accounted for more than half as compared to the first half the last century, particularly in the Rhodophyta and Phaeophyta species (Table 7.6), whereas Chlorophyta species increased by 50% during the same period. For example, the average biomass of the Phaeophyta species Cystoseia barbata was estimated as 7 kg.m-2 in 1966-1969 with respect to 1.1kg.m-2 in 1997 up to 2 m depth. It was mostly substituted by Enteromorpha intestinalis, Cladophora vagabunda, Ceramium rubrum.

Table 7.6. Changes in species structure of different types of macrophytes in Varna Bay.

Type

1904-1939

1962-1972

1994

1999

2001

2002

Chlorophyta

10

9

13

13

13

15

Phaeophyta

11

6

4

3

4

4

Rhodophyta

37

23

14

8

11

8

Total

58

38

31

24

28

27

Table 7.7. Changes in saprobic structure of macrophytes in Varna Bay in the years of investigation.

Period

1904 ? 39

1969-72

1994

1999

2001

2002

Oligosaprobic

37

23

3

3

3

3

Mesosaprobic

16

11

21

13

18

17

Polysaprobic

5

4

7

8

7

7

In terms of saprobic structure of macrophytes in Varna Bay, major loss occurred in oligosaprobic species which became almost extinct since the 1990s (Table 7.7). Typical oligosaprobic species such as Ralfsia verrucosa, Stilophora tuberculosa, Nereia filliformis, Dictiota dichotoma, Cladostephus verticillatus were not registered during the last two decades in this region. The most dominant species, in terms of their biomass, are the polysaprobic and mesosaprobic species such as Ceramium rubrum, Callithamnion corrymbosum, Enteromorpha? intestinalis, Ulva rigida, Bryopsis plumosa. This floristic structure was similar to the Odessa Bay further north (Minicheva, 1998).

In 1994, the macrophytobenthos along the Bulgarian Black Sea coast was found to contain 157 species, which constituted 53% of the total Black Sea macroflora. They belonged to 82 genera, 43 families and 25 classes of Rhodophyta, Phaeophyta and Chlorophyta. The first group was the richest with about 55% of all species, followed by the rest with approximately even number of species (Table 7.8). In comparison with the Russian (75%), Romanian (40.7%) and Turkish coast (24%), the Bulgarian Black Sea coast ranked second regarding to macroflora species diversity (Kalugina-Gutnik, 1975).

The comparison of the floristic indices of macrophytobenthic coenoses for 1904-1972 and 1994-2002 periods may be used to assess the level of eutrophication along the Bulgarian coast (Table 7.9). The floristic index increases with enhancement of the level of eutrophication.? For example, in Varna Bay being the most eutrophic part of the Bulgarian coastline, it was increased from 4.3 during 1904-1939 to 5.3 in 1969- 1972 and to more than 6.0 in the 1990s and the present decade. In 1994, the lowest floristic index was in the Cape Maslen and the highest in Kavarna (P=7.5), followed by Varna Bay (P=6.5) (Table 7.9). It acquired intermediate values for Irakly and Zelenka (P= 5.0) and for Bjala and Balchik transects (P= 6.0).

?Table 7.8. Bulgarian and Black Sea macroalgae taxonomic composition.

Regions

Group

Order

Family

Genus

Species

Bulgarian coast

Rhodophyta

8

18

39

86

Phaeophyta

10

16

26

37

Chlorophyta

7

9

17

34

Total

25

43

82

157

Black Sea

Rhodophyta

8

23

61

142

Phaeophyta

11

25

46

77

Chlorophyta

7

14

36

74

Total

26

62

143

293

Table 7.9. Comparison of floristic indices along the Bulgarian coastline.

Transect

Floristic

index (P)

Saprobic

Index (X)

Cape Maslen

3.6

1.170

Zelenka

5.0

0.330

Irakly

5.0

0.350

Bjala

6.0

0.285

Balchik

6.0

0.280

Varna Bay

6.5

0.220

Kavarna

7.5

0.176

The values of saprobic index that decreased with enhancement of the level of eutrophication also indicated high eutrophication tendency along the Bulgarian coast in 1994. The highest saprobic index value was estimated for Cape Maslen (X=1.17) and the lowest one for Kavarna (X=0.176), followed by Varna Bay (Table 7.9).? They are consistent with the highest values total macrophytes biomass in the Cape Maslen (4184.18 g∙m-2) and the lowest level in Kavarna (1367.15 g∙m-2) and Varna Bay (1413.65 g∙m-2) at 5 m depth (Fig. 7.5). Irakly and Zelenka (X=0.35, X=0.33), Bjala and Balchik (X=0.285, X=0.28) have been identified by intermediate saprobic index values and hence intermediate level total macrophytes biomass. The biomass distribution from different types of algae was characterized by the following peculiarities. The highest biomass of brown algae was registered in the Cape Maslen? (2320.07 g.m-2 ), it was 1.1 lower at Zelenka, 2.3 fold lower in Bjala, 22 times lower in Varna Bay, and it was of significant value in Kavarna. The highest biomass of Chlorophyta (1785.16 g.m-2) and Rhodophyta (616.28 g.m-2) representatives was estimated in the Bjala transect (Fig. 7.5). Phaeophyta prevailed? in the Cape Maslen and Zelenka, and Chlorophyta in Varna Bay, Bjala and Kavarna (Fig. 7.5).

Fig. 7.5. Biomass distribution of macrophytes along the investigated transects in 1994.

The low biomass of Phaeophyta (Brown algae) species Cystoseira is considered as a reliable indicator for the estimation of the level of eutrophication. It was registered in greater values in the Cape Maslen area (2320.07 g∙m-2) where it constituted 55.4% of the total biomass whereas only 7.5% in more eutrophic Varna Bay region. On the contrary, the mass development in biomass of the Chlorophyta species Ulva rigida, Enteromorpha intestinalis and the Rhodophyta species Ceramium rubrum and Callithamnion corimbosum is an indication of increased content of organic matter and nutrients, and hence eutrophication (Kalugina-Gutnik, 1975; Bologa, 1989; Minitcheva, 1990). They were dominant in Varna Bay as identified by Ulva rigida (max. biomass 1913.7 g∙m-2), Enteromorpha intestinalis (2287 g∙m-2), Ceramium rubrum (312.5 g∙m-2), Callithamnion corimbosum (624.8 g∙m‑2).

The highest percentage of oligosaprobic algae and the values of saprobic and floristic indices therefore indicated a lower eutrophication level in the Cape Maslen in comparison with the other investigated areas along the Bulgarian coast. The highest level of eutrophication was detected in Varna Bay and Kavarna as further confirmed by low biomass of macrophytobenthos. Zelenka, Balchik, Bjala, Irakly characterized moderately eutrophic regions.

A direct relation exists among the nutrient loading, increasing phytoplankton growth, restricted light penetration and reduction of macroalgae biomass (Hough et al., 1989). In support to this, our results showed that the bulk of biomass in the Cape Maslen area spread at 5m depth. It was 6 times higher than that in Varna Bay due to permanent blooms of phytoplankton and high level of eutrophy. Besides, the highest biomass of Cystoseira (2320.07 g∙m-2), preferring waters with low nutrient loading, was registered in the Cape Maslen area, compared with the other regions, especially Varna Bay and Kavarna.

Fig. 7.6. Average multi-annual specific surface values ( m2.kg-1 ) along the Bulgarian coastline during 1999-2002.

The floristic composition of plant communities along the Bulgarian coast in 1999-2002 can be divided into three categories according to their specific surface values: under 10 m2∙kg-1 (indicating lower eutrophication), from 10 to 30 m2∙kg-1 (indicating intermediate level eutrophication), and over 30 m2∙kg-1 (indicating higher eutrophication). It should be noted that a high specific surface value corresponds to a macrophyte biomass and indicates a higher eutrophication level. According to this classification, in Trakata, 33% belong to macrophytes with specific surface from 10 to 30 m2.kg-1 and 67% belong to macrophytes with specific surface value over 30 m2∙kg-1 (species with specific surface value under 10 m2∙kg-1 are not registered). Traka therefore represented the least eutrophic zone with respect to the other regions. Its average specific surface value for 1999-2002 is 43.68 m2∙kg-1 (Fig. 7.6). The most eutrophicated zone turns out to be the channel between the Varna Bay and its lake in which 92% belong to species with specific surface value over 30 m2∙kg-1 (the mean value = 95.79 m2∙kg-1). It is followed by Galata (83%), Veteran and (72%). Accordingly, the 1999-2002 average value of macrophyte biomass along the coast decrease from Trakata (911.8 g∙m-2) to Veteran (613.83 g∙m-2), Cape Galata (512.7 g∙m-2) and the channel (484.6 g∙m-2) (Fig. 7.7).

The major change during the recent years was biomass decrease of Cystoseira (species indicator of high quality waters) in the Varna Bay. This olygosaprobic macrophyte with low specific surface and big size is replaced by other polysaprobic species such as Cladophora, Enteromorpha, Ceramium with higher specific surface, especially in more eutrophic areas (Dencheva, 1994).

The calculated macroalgal production is highest in Trakata and the Channel regions. The high values in the channel are due to presence of species with high specific surface and intensity of functioning and short life cycle and biomass. The high production in Traka is because of the presence of Cystoseira (high biomass, low specific surface).

Fig. 7.7. Average multi-annual biomass values (g.m-2) along the Bulgarian coastline during 1999-2002.

7.5. Turkish shelf area

A detailed account of the early algal records along the Turkish coast of the Black Sea (Fig. 7.8) is given by Aysel et al. (1996; 2000, 2004; 2005), Erdugan et al. (1996). 25 macroalgal taxa were reported in Trabzon coastal waters and 21 macroalgal taxa at Sinop and its vicinity (central zone), 55 taxa along the coast of Trabzon and 88 taxa between Rize and Sarp in the southeastern part of the Black Sea, 210 taxa at Bartin and 205 taxa at Zonguldak (western zone) belonging to four algal classes (Cyanophyceae, Rhodophyceae, Phaeophyceae and Chlorophyceae).? In total, 258 taxa were identified in the Turkish Black Sea region, from five classes: Cyanophyceae with 13 species, Rhodophyceae with 140 species, Phaeophyceae with 53 species, Chlorophyceae with 50 species and Charophyceae with 2 species. With new additions of algal taxa, this number increased later to 297 by Aysel et al (2004). The list of algal taxa and macrophytes along the Turkish coast of the Black Sea is given in Table 7.10, and their relative dominancy is given in Table 7.11.

Conservation biology and threats: There have been dramatic changes in the southern Black Sea ecosystem as a result of eutrophication caused by increased nutrient input via major northwestern rivers and industrial and harbour activities in recent years.? Abnormal changes due to altered nutrient balance were reflected in the qualitative and quantitative composition of phytoplankton, zooplankton and ichthyofauna (Bat et al., 2007). These changes also included the loss of extensive areas of seagrass meadows, a virtual collapse of the benthos over the shelf area and mass mortalities due to hypoxia. The dredging of sand from the sea has also been destroying the habitats along the Turkish Black Sea coast (?zt?rk, 1998). In addition, the highway construction along the coastline harmed the macroalgae and macrophyte communities (Aysel et al., 2005).

Fig. 7.8. Map for the coastal regions along the Turkish coast of the Black Sea.

Table 7.10. Benthic algae and macrophytes diversity from different areas in the Black Sea coast of Turkey (Aysel et al., 2005).

Regions

Seaweeds

Macrophytes

Cyano-phyta

( CY)

Rhodo

phyta (R)

Phaeo

phyta (O)

Chloro

phyta (C)

Magnolio

phyta

Kirklareli

23

71

24

30

3

151

Kocaeli, Sakarya, D?zce

30

126

50

46

3

255

Zonguldak

20

100

42

43

3

208

Bartin

12

116

43

39

3

213

Kastamonu

22

133

56

48

3

262

Sinop

22

136

52

55

3

268

Samsun

20

106

27

22

3

178

Ordu

14

93

27

26

4

164

Giresun

18

109

33

30

3

193

Trabzon

1

23

8

23

3

58

Rize, Artvin

3

43

15

27

3

91

Total

30

142

57

58

4

297

Table 7. 11. Dominancy in division level among of Black Sea coast of Turkey (Aysel et al., 2005).

Regions

Division

R/O

R/C

R/CY

O/C

O/CY

C/CY

Kirklareli

3.00

3.70

3.10

0.80

1.00

1.30

Kocaeli,Sakarya, D?zce

2.52

2.73

4.20

1.08

1.66

1.53

Zonguldak

2.40

2.30

5.00

1.00

2.10

2.20

Bartin

2.70

3.00

9.70

1.10

3.60

3.30

Kastamonu

2.37

2.77

6.04

1.16

2.54

2.18

Sinop

2.60

2.50

6.50

0.96

2.50

2.59

Samsun

3.92

4.81

4.30

1.22

1.35

1.10

Ordu

3.44

3.58

6.64

1.04

1.93

1.86

Giresun

3.30

3.63

6.05

1.10

1.83

1.66

Trabzon

2.90

1.00

23.00

0.30

8.00

23.00

Rize, Artvin

2.90

1.60

14.3

0.60

5.00

9.00

Seagrasses (Magnoliphyta)

The seagrasses (Magnoliphyta) patchy distributed sandy and muddy substratums of the coast of Turkish coastal zone. According to Milchakova (1999), six species have been occured in the Black Sea. These are Zostera marina (eelgrass), Z. noltii, Potamogeton pectinatus, Ruppia maritima, R. spiralis and Zannichellia major. Among these, Z. marina (eelgrass), Z. noltii, Potamogeton pectinatus and as differently Cymodocea nodosa reported from Turkish Black Sea coast (G?nl?g?r-Demirci & Karakan, 2006). Generally the vertical distribution of Zostera beds in the Turkish self area is mainly between 0.7 m and 6 m but low-density patches can grow down to 17 m. Zostera meadows are an important source of food and shelter for the juvenile stages of many fish and crustacean species The network of roots and leaves in a Zostera bed provides ecological nichs for a wide range of associated with fauna and flora, so that the biotopes are important in maintaning coastal biodiversity. These beds exhibit high rates of primary productivity and are an important source of organic matter, fuelling detritusbased food chains within the biotope (Bostr?m and Bonsdorff, 1997). The distribution of Zostera spp. meadows at the Turkish coastal zone was patchy, forming mosaic patterns with other phytobenthic and zoobenthic species (Ceramium spp., Cladophora spp., Ulva spp., Polysiphonia sp., Potomageton pectinatus, Botryllus schlosseri, and serpulid polychaets). (unpublished data). Seagrass constitute of an important part of the Black Sea coastal zone. They have still received much less attention than the other systems in terms of research and management. In Turkey, as in other Black Sea countries, the negative impact on the seagrass ecosystems is increasing due to a growing coastal population, pollution, and overexploitation of resources. Sinop region is an example of an area strongly influenced by overfishing, illegal bottom trawling, verified by local fisherman complaining on diminishing catch rates.

Consequently, to increase the present scientific knowledge on ecological interactions such as between fish and invertebrate assemblages, and seagrass environments of the region is important.

7.6. Northeastern (Russian) shelf area?

Floristic composition: In the 1970s, the floristic richness of marine algoflora along the northeastern Black Sea coast comprised 146 macroalgae species: 33 Chlorophyta, 35 Phaeophyceae, 78 Rhodophyta (Kalugina-Gutnik, 1975). The studies performed during 1999-2007 identified 143 macroalgae species: 41 Chlorophyta, 29 Phaeophyceae, 73 Rhodophyta (Fig. 7.9). Only 39 of them (10 Chlorophyta, 7 Phaeophyceae, 22 Rhodophyta) had 100% frequency of occurrence, the others were registered only 1-3 times.

The important difference between the 1970s and the 2000s is the increase of Chlorophyta and simultaneous decrease of Phaeophyceae species, such as Grateloupia dichotoma, Dasya baillouviana, Gracilaria verrucosa, Eupogodon apiculatus (=Dasyopsis apiculata). It is noteworthy to point out that none of the widely spread species of Phaeophyceae has disappeared from the regional flora, though the majority of them belongs to oligosaprobic forms. Two brown algae, Arthrocladia villosa and Halopteris scoparia, were noted to be absent in 1999-2000. However, Halopteris was later found in the vicinity of Gelendzhik in 2001, and Arthrocladia at the Maria Magdalena Bank in 2002 (Maximova and Mitjaseva, 2003; Mitjaseva et al., 2003). In June 2003 Gracilaria appeared near Gelendzhik and in Inal Bay, and the real outbreak of this alga took place near Golubaja Bay at the depth of 7-9 m in July 2003. There were approximately 10 large thalli (up to 30 cm high) per square meter (A.A. Georgiev, M.I. Georgieva, pers.com).

Fig. 7.9. Taxonomic composition of North Caucasian bottom algoflora in the 1970s (Kalugina-Gutnik, 1975) and the present decade.

In parallel to floristic depletion, a lot of new species have penetrated to the North Caucasian marine flora from the other regions of the basin: two Ulothrix species, Ulvella lens, Pringsheimiella scutata, Entocladia (= Ectochaete) leptochaete, Cladophora siwaschensis (Chlorophyta); Pylaiella littoralis, Cladostephus spongiosus f. spongiosus, Myriotrichia clavaeformis (= M. repens) (Phaeophyceae); Goniotrichum elegans, Kylinia microscopica, Acrochaetium daviesii, A.savianum, Compsotamnion gracillimum, Polysiphonia fucoides (= P. nigrescens) (Rhodophyta) and some others. Most of them are the endophytes, micro-epiphytes and filamentous forms.

Some species that have been considered to be rare in 1950-70s nowadays are widely spread along the North Caucasian coast. Among them are Chaetomorpha gracilis, Cladophora vadorum, Cladophoropsis membranacea (Chlorophyta), Callithamnion granulatum, Rhodochorton purpureum, Ceramium siliquosum var. elegans (Rhodophyta) and others. Thus, the changes took place not only in the floristic composition but also in the regional status of many species.

Bathymetric distribution and community structure of bottom vegetation: In the middle of 20th century, the most abundant member of bottom flora was Cystoseireta that stretched from 0.5 m to 20 m, in some places even to 35 m (the Bolshoi Utrish cape). The Cystoseireta formation survived under unfavorable conditions in the 1980s-1990s (Fig. 7.10). At present, its biomass at the upper phytal zone (0.25-1 m) reached 13-15 kg/m2 in some places, and its average was about 3.5-5.0 kg/m2. But, lower boundary of Cystoseireta still stay at the depth of 10-12 m (Fig. 7.10); only isolated oppressed thalli of Cystoseira barbata can be noticed as deep as 12-15 m. Its biomass at the localities deeper than 5-6 m usually is not higher than 150-300 g/m2. Overall standing stock of both Cystoseira species was about 2 million tones and their annual primary production was up to 4.4 million tones. The Cystoseira communities included more than 120 species of other macroalgae. At the lower horizon of the phytal zone (18-28 m) the formation Phyllophoreta has been replacing the Cystoseira community, and formations Polysiphonieta (25-50 m) and Antithamnieta (45-70 m) have been usual and widespread along the northern shore of the Black Sea (Kalugina-Gutnik, 1975).

The northeastern Black Sea region produced nearly a half of the Black Sea Cystoseira stock in 1960-70s that was about 980 thousand tons (Kalugina-Gutnik, 1975). The contemporary Cystoseira stock in the region was, however, estimated to reduce to 100 thousand tons (Maximova and Moruchkova, 2005; Vilkova, 2005), but this value may be an overestimate due to very low biomass in deep phytal zone. The biomass of the leading species usually formed about 60% (from 30% up to 95%) of the total community biomass; hence the total stock of the regional macrophytobenthos would be no more than 160-170 thousand tons. Thus, it may be postulated that nearly ten-fold drop of the macrophyte biomass occurred along the North Caucasian coast during last 30 years. Needless to say, its commercial exploitation is not economically feasible any more.

Fig. 7.10.? Cystoseira biomass dynamics (1970s: Kalugina-Gutnik, 1975)

In the 1960s, the Cystoseira belt off the North Caucasian coast was as wide as 1.5 ? 3 km (Kalugina-Gutnik, 1975). Now it is not wider than 300 m, usually about 100 m due to the structural (age, size, biodiversity, etc.) and functional (productivity, oxygen metabolism, bioconcentration) changes due to heavy eutrophication (Kalugina-Gutnik, 1975; Khailov et al., 1992; Maximova and Kucheruk, 1999; Gromov et al., 2001b; Gromov, 2004; and others). Their early life stages were very sensitive to the nutrient enrichment and its subsequent effects of low transparency, high sedimentation, epiphytes etc. (Berger et al., 2003; Is?us et al., 2004; Bergstr?m, 2005). Nitrate enrichment showed a significant negative effect on the attachment rate and germination of Fucus vesiculosus zygotes. Germling survival was reduced by over 20% in moderate nitrate enrichment, and by over 50% in high nitrate and phosphate enrichment during the first 10 days of experiment (Bergstr?m et al., 2003). The intensive sedimentation reduced the survivorship for Fucus serratus embryos: under the 1 mm layer it dropped from 90% to 50%, and under 3 mm layer ? to less than 10%. And what is especially significant: the ruinous effect of organically rich biodeposits was much higher than that of mineral sediment (Chapman and Fletcher, 2002); and the drop of water transparency after Mnemiopsis invasion was due to organic contamination, first of all.

Cystoseira germlings have not been observed deeper than 5 m from the late-1980s and to 2002. But, the annual appearance of numerous juvenile Cystoseira thalli was observed in intensively washed upper phytal zone during all these years. In 2000, the recruitment of juvenile Cystoseira was observed in some places. Maybe it was just the coincidence, but the year 2000 was the first year of suppressed Mnemiopsis activity and beginning of improvement of light and sedimentation conditions indicating an additional role of ?Mnemiopsis on Cystoseira beds.

The situation at lower phytal zone is even more dramatic. In the region between Gelendzhik and Novorossijsk, bottom vegetation was absent at depths greater than 20-25 m. Deep-sea formations of Polysiphonieta and Antithamnieta completely disappeared. As for Phyllophoreta, Phyllophora nervosa abundance dropped significantly at all levels of its bathymetric range. In the 1970s, the attached Phyllophora had formed a wide belt with the coverage up to 50-80% with the mean biomass about 1.5 kg/m2 and up to 4 kg/m2 in the thick beds along the coastline from Anapa to Novorossijsk (Kalugina-Gutnik, 1975). In the 1980s ? early 1990s the coverage was as high as 30-40% and mean biomass was 1.5 kg/m2 (and up to 6 kg/m2 at some locations) at depths from 12 to 28-30 m in the vicinity of Gelendzhik (Maximova and Rybnikov, 1993).

?

Fig. 7.11.? Phyllophora biomass dynamics. Data source for 1970s: Kalugina-Gutnik (1975).

The investigations carried out in 1999-2007 in various points of the North Caucasian coast (Novorossijsk, Gelendzhik, Divnomorskoje, Inal Bay, Djubga, Arhipo-Osipovka, Tuapse) showed that the lower boundary of Phyllophora belt has shrunk by at least 10 m ? to the depth of 15-20 m. One can now observe only rare small beds and single plants, the coverage is not higher than 15-20% and biomass rarely exceeds 0.3-0.5 kg/m2, being usually about some tens of grams. In 2006-2007 we noticed only single thalli of Phyllophora at the depth of 20 m in Gelendzhik region (Fig. 7.11). Thus, not only the community of Zernov?s Phyllophora Meadow showed the catastrophic changes (Milchakova, 2001; Zaitsev, 2006), but also the near-shore populations off the North Caucasian coast. The lower phytal zone associations suffered most from the reduced transparency of coastal waters. Even sciophile Phyllophora crispa could not adapt itself to the narrowing of the photic zone. The similar situation was also observed along the Crimean coast. The Crimean bottom vegetation degraded deeper than 3 m, while there is a marked signs of macrophytobenthic rehabilitation in the upper phytal zone (Milchakova, 2001; Zaika et al., 2004).

As the result of Phyllophora degradation, the dominant structure of deep-sea communities also changed. The biomass of green noncellular algae Codium vermilara ?reached 4 kg/m2 with a density of 1500 sp/m2 at the depths of 10-15 m in 2001-2002. A similar situation took place for the brown crust-forming algae Zanardinia prototypus in 2002-2007. Its coverage increased by 60-80% at depths between 4 and 10 m. These events are called as the macroalgal ?blooms? as observed earlier for filamentous algae in intensively polluted areas, like Cladophora ?blooms? in Anapa Bay (Vershinin and Kamnev, 2001). These blooms were highly dynamic events with significant year-to-year variations. For example, although a lot of juvenile thalli were observed at the depth of 15 m no Codium ?bloom? was observed in 2003-2004 and the production of this alga returned its standard state and became one of the common but not a dominant species. The brown algae Halopteris scoparia has been rather abundant in 2001 in Gelendzhik region, but it has not been observed in following years, except a regular appearance in the vicinity of Tuapse. It may be quite likely that the periodic outbreaks of different species signify a gradual improvement of environmental conditions (e.g., illumination) after the invasion of Beroe ovata. Evidently, the temporarily deserted niches during the Mnemiopsis era started to be filled again but not necessarily by the same species.

In addition to the outbreaks of secondary species, the role of previous dominant species decreased simultaneously up to their disappearance. For example, the floristic composition belonged to the Cystoseira-Phyllophora association in the vicinity of Novorossijsk (Southern Ozereevka, depth 20 m) (Kalugina-Gutnik, 1975), but Cystoseira barbata was entirely absent indicating that the dominant algae group was removed from the association. The same association usually found in the depth range from 10-12 m to 15-18 m (e.g. Phyllophora crispa, Apoglossum ruscifolium and Cladophora dalmatica) also formed underwater bench at the depths of 2-5 m in sheltered regions in close proximity of deeper associations.

Maria Magdalena Bank: situation in clean waters: Macrophytobenthos transformation was also observed in Maria Magdalena Bank that was practically undisturbed and unpolluted region located in 5 km off Anapa coast. During the previous macroalgal investigations at the end of the 1950s, the bottom vegetation of the Bank was studied in the depth range from 2.8 m to 14.4 m, and 26 species of macroalgae were identified including 1 Chlorophyta, 13 Phaeophyceae, 12 Rhodophyta (Petrov, 1960, 1961a, b). After 45 years the algal samples collected at depths from 2 m to 30 m showed 41 species (11 Chlorophyta, 11 Phaeophyceae, 19 Rhodophyta) (Mitjaseva et al., 2003). The main difference in floristic lists was the pronounced increase in the number of Chlorophyta species. The high abundance of green algae was the evidence of brackish and/or eutrophicated waters. The equal quantity of green and brown species was the indication of mesosaprobiont community (Kalugina-Gutnik, 1975).

The next difference was the change of dominants: Cystoseira barbata has been the main alga in the 1950s but it was replaced by Cladostephus spongiosus f. verticillatus, distributed from 2 to 15 m in 2003. C. barbata was registered only twice with small quantities at the very top of the Bank (2 m depth). On the other hand, Cladostephus was not mentioned at all in the 1950s. Likewise, two new associations observed recently C.spongiosus f. verticillatus - Ceramium rubrum at the depth 2-5 m, and Arthrocladia villosa - Antithamnion plumula - Cladophoropsis membranacea - Bryopsis hypnoides at the depth 25-30 m have not been described earlier (Maximova and Moruchkova, 2005). Instead, the attached form of Phyllophora crispa that mainly inhabited the depth range from 8.4 to 14.4 m was found only at 2 m, and only with a few thalli at 15 m in 2003. Thus, these long-term macrophytobenthos transformations observed even at undisturbed localities imply that anthropogenic changes affected the Black Sea macrophytobenthos as a whole even at the opposite end of the sea to the western coast.

Algae of living animal substrata: Recent observations also showed the macroalgae populations attached to the shells of live mollusks Rapana venosa (Gastropoda), Chamelea gallina and Anadara inaequivalvis (Bivalvia) on the soft bottom of the Anapa region and the Gelendzhik Bay at depths from 5 to 20 m. The dead shells were often inhabited by macroalgae, even though mollusks did not demonstrate any sign of illness or damage. The total density of Chamelea reached 300 sp./m2, 10-30 of them bearing algae. The aspect of the association reminded the coloured clouds covering the bottom. The area of this association was wide enough to consider its primary production to be rather significant on the soft bottom.

Epiphytic sinusia and opportunistic species: The Cladophora vagabunda ?bloom? mentioned above is a striking example of r-species development in the Black Sea with its standing crop of 7500 tons in the area of 15 km2 in the Anapa Bay (Vershinin and Kamnev, 2000, 2001). Here the situation with the epiphytic sinusia will be discussed because of its noticeable changes during the last years. Its ecological role is high: about 80% of Black Sea benthic macroalgae are obligate or facultative epiphytes. At the beginning of the 1990s, epiphytic sinusia dominated in Cystoseira communities. In recent years, rich epiphytic flora, especially of red algae (Laurencia obtusa, L. coronopus, Chondria capillaries, Ceramium rubrum, C. secundatum, C. diaphanum, C. siliquosum var. elegans, Polysiphonia subulifera, Antithamnion cruciatum, Seirospora interrupta, Compsothamnion gracillimum etc) were observed but the quantitative characteristics of sinusia became much more spare. Even during their mass development at the end of summer the share of epiphytes in total community biomass did not exceed more than 30-35%. The epiphytic sinusia is more abundant (mainly owing to Ceramium species) at the upper phytal zone (1-2 m).? The peak of its floristic diversity is marked at the depth of 2 m, but its contribution to the total community biomass is not high (3.5-5%). The species richness of epiphytes is lower (mainly Laurencia obtusa and Polysiphonia subulifera) at 5 m depth, but its biomass contribution rises up to 20-25%. At 10 m and deeper levels, the epiphytic sinusia is poor in both qualitative and quantitative aspects. For example, we have noticed 11 epiphytic species at the depths 0.5 m and 5 m, 17 ? at the depth 2 m, and only 5 species at 10 m near Arhipo-Osipovka in 2001. In 2002 (the end of May ? beginning of June), the real ?bloom? of epiphytic Chondrophycus paniculatus (= Laurencia paniculata) was observed in the vicinity of Golubaja Bay. This species was the seasonal dominant of epiphytic sinusia; its brightly yellow thalli masked basiphytic Cystoseira plants. Such high abundance of this species was never reported before. In 2003 (the end of June) the unusually high brown epiphytic Stilophora rhizodes (which had been rather rare in 2002 and earlier) and red Chondria capillaries were observed. They were so abundant (especially S. rhizodes) that nearly replaced the common dominants of epiphytic sinusia in Cystoseira associations - Polysiphonia subulifera and Laurencia obtusa. In 2003 P.subulifera was almost the rare component of sinusia, while L. obtusa was a slightly more abundant. These observations were held in Inal Bay, Golubaja Bay near Gelendzhik, in the vicinity of Divnomorskoje.

The changes in ecological and morphological properties of species: Under prolonged influence of eutrophication some algae have changed their properties. In particular, noticeable shifts occur in saprobic status of some algae populations. For example, oligosaprobic Padina pavonia and polysaprobic Enteromorpha intestinalis started growing in the mesosaprobic conditions; Gracilaria verrucosa and Chara aculeolata, inhabited the Gelendzhik Bay, one of the most polluted places along the shore (Maximova and Luchina, 2002). Apparently, high eutrophication became an environmental background which made the species to change their ecologic preferences. In the eutrophied environment, the morphology of the algae changed. Cystoseira, for example, lost the youngest branches (Khailov et al., 1992), and on the contrary Gracilaria verrucosa, Gelidiella acerosa intensified their branching (Rygalov et al., 1988; Mairh et al., 1990). Furthermore, two shallow-water ecological forms of Phyllophora nervosa appeared in the period of maximal eutrophication of coastal waters in early 1990s (Maximova and Rybnikov, 1993). During the present decade, the plants of the crispa morphotype were not noticed while the pennata form kept its abundance.

7.7. Conclusions

The major features of macrophytobenthos during the last several decades were decreasing species number, domination of small-size species with fast growth rate, decrease of community biomass, and reduction of Cystoseireta phytal zone to a narrow inshore strip shallower than 10 m which could only provide enough light for photosynthesis. As Cystoseira biomass decreased markedly, macroalgae blooms were dominated by opportunistic species (mainly epiphytic filamentous algae) in basiphytic and epiphytic sinusia.

Observations performed during the last 10 years indicated a restoration success of Cystoseira phytocoenoses in the coastal zone, weaker predominance of opportunistic species - mainly their epiphytic filamentous forms, with respect to 1980-90s, re-establishment of the Phyllophora-based community in the centre of the north-west shelf that has been formerly known to be Zernov?s Phyllophora field. The main signature of restoration of Cystoseira and Phyllophora phytocoenoses was raising their species diversity with increasing moiety of large, perennial species and approximately two-fold decrease of the moiety of finely branched epiphyte species. However, no apparent recovery is yet evident at inshore locations close to the mouths of the Danube and Dniester. On the basis of 2004 observations, trophic status of the macrophytobethos along the western coast is classified as eutrophic, whereas the rest (the southern, Caucasian and Crimean) is mesotrophic. The Georgian coastal waters also fall into the eutrophic class.

Ongoing secondary eutrophication and human activities such as harbour constructions, industry, and tourism as well as anomalous climatic conditions led to establishment of different algal-dominated assemblages that adapted to the new conditions along coastal regions after the intense eutrophication state. At present, the macrophytes community structure is sensitive to the climatic changes and is dominated by either winter or summer species depending on the climatic conditions. The data tend to show a positive sign of recovery, but it is still difficult to mention a basin scale restoration of the macrophytobenthos community structure. Monitoring studies on the macroalgal flora should continue to follow likely ecological modifications of the macroalgal flora during its present transitional state.

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