G G Polikarpov - Equi-dosimetry of deleterious factors at the level of populations and communities of aquatic organisms - страница 1

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МОРСЬКИЙ ЕКОЛОГІЧНИЙ ЖУРНАЛ

УДК 574.5:551.49.09:543.31:539.16(262.5)+574/577:539.16:574:543.53:575.224:575.5+551.464:541(28):628.394

G. G. Polikarpov1, Prof., Chief Scientist, Yu. P. Zaitsev2, Prof., Chief Scientist, S. Fuma , Dr., Senior Researcher

1 The A. O. Kovalevsky Institute of Biology of the southern Seas (IBSS), National Academy of Sciences of Ukraine,

Sevastopol, Ukraine 2 IBSS Odessa Filial branch, Odessa, Ukraine 3 National Institute of Radiological Sciences (NIRS), Chiba, Japan

EQUI-DOSIMETRY OF DELETERIOUS FACTORS AT THE LEVEL OF POPULATIONS AND COMMUNITIES OF AQUATIC ORGANISMS

A principally new ecological tool is proposed for comparing equivalent effects of very different factors at the levels of populations and communities as the new approach - equi-dosimetry of effects by radiations (ionizing and ul­tra-violet), acidification and metals as well as any other deleterious impacts.

Key words: radiochemoecology, equi-dosimetry, nuclear and non-nuclear pollutions/factors, microcosm, Daphnia, aquatic populations and communities, environmental critical zones, major interphasic marine ecosystems, Black Sea

The present paper is a synthesis and a re­view of three fields of logically mutually con­nected studies: (I) the radiochemoecological con­ceptual model of effects in all possible scales of deleterious factors and the equi-dosimetry ap­proach for ecotoxicity ranking of various toxic chemicals on the basis of ionizing radiation, which were originated and are being developed at IBSS, Sevastopol, Ukraine [15 - 19]; (II) experimental studies of ecological effects of various toxic agents on the aquatic microcosm in comparison with ionizing radiation, originally proposed and are being elaborated at NIRS, Chiba, Japan [3 - 8] and (III) long-term studies in the Black Sea eco­systems - critically impacted zones - which are carrying out on the basis of the concept of the main marine interphasic ('contouric') communities and their interactions at IBSS Odessa Filial branch, Odessa, Ukraine [23 - 25].

I. RADIOCHEMOECOLOGICAL CONCEP­TUAL MODEL

One of us [14, 15] had proposed and de­veloped a conceptual model of zones of responses of organisms, populations and ecosystems to all possible dose rates of ionizing radiation in the en­vironment (Fig. 1). These zones are: the zone of well-being (natural background levels of envi­ronmental ionizing radiation below 0.005 Gy/y), the zone of physiological masking (0.005 -0.1 Gy/y), the zone of ecological masking (0.1 -4 Gy/y) and the zone of damage to ecosystems (>> 4 Gy/y).

© G. G. Polikarpov, Ju. P. Zaitsev, S. Fuma, 2004

5

Fig. 1. Zones of dose rates and their effects in the biosphere [15, 16] Рис. 1. Зоны мощностей доз и производимые ими эффекты в биосфере [15,

16]

The model was afterwards extended and transformed into the radiochemoecological con­ceptual model [16 - 19], which covers effects of both ionizing radiation and chemical pollutants (Fig. 2). The following ecological criteria are used in the Fig. 2: decrease of number or total mass (of populations), decrease of number of species (of communities) and degradation of communities (of ecosystems).

A good agreement of the microcosm data on chemical and ionizing radiation impacts [4] with the radiochemoecological model mentioned above was demonstrated [17]. Equi-dosimetry means the equal ability of proper amounts/doses of different factors (for example, ionizing radia­tion, UV, acidity, heavy metals a.s.o.) to produce the same quantitative effect.

Ecological Gray-equivalent of the effects of chemicals is the ratio: Gy/C, where C is a

2, Т. iii. 2004

chemical concentration [19]. In cases of heavy ionizing particles we have to use Ecological Sievert-equivalent.

II. EXPERIMENTAL STUDIES

Usefulness of the radiochemoecological conceptual model and equi-dosimetric approach was demonstrated by the following examples, in which effects of various toxic agents on water fleas or the aquatic microcosm were compared with those of ionizing radiation.

Water-flea ecotoxicity test

The water flea Daphnia is a typical fresh­water zooplankton. This organism is sensitive to toxic chemicals, and is a key group in aquatic ecosystems. That is, Daphnia is strong in compe­tition among herbivorous zooplankton species,

TOTAL LETHALITY FOR BIOSPHERE

BIOSPHERIC LEVEL

Degradation

1 _______________

EFFECTS AT THE S

Л           DAMAGE TO Impoverishment P ECOSYSTEMS

1             ZONE                . .

BIOCENOTIC                         / j

К

Species reduction ^                                    Number reduction

e a

LEVEL                        / 1 j

 

/              і !

Reinforce of population resistance

ECOLOGICAL  Mutations doubling

MASKING ---------------

ZONE

Stimulation/delay

POPULATION LEVEL

 

In the Black Sea: 10-3-< 10-2 Gy/y

Ionising radiationAny other factor(s)

"I    I    I    I    I I I

10-1 1 10 102 103 106 >107 X...........................Y....................................Z

Gy/y

D

Fig. 2. Long-term reactions of populations/ecosystems to ionizing radiation as well as any chemical or physical factors at the doses in 'masking' and 'damage' zones. X, Y, Z - doses D of non-radioactive factors in each zone. Ecological impacts in the Black Sea are connected with non-nuclear factors because of low doses of ionizing radia­tion [17].

Рис. 2. Долговременные реакции популяций/экосистем на воздействие ионизирующих излучений и любых химческих или физических факторов при дозах, соответствующих зонам "маскировки" и "повреждения". X, Y, Z - дозы D нерадиоактивных факторов в каждой зоне. Экологические последствия в Черном море связаны с неядерными факторами по причине низких доз ионизирующей радиации [17].

and appears to play a key role to control algal biomass. Therefore, once the Daphnia population suffers severely by chemicals such as insecticides, some other zooplankton species such as rotifers or algae are indirectly increased. For these reasons, Daphnia is generally used for ecotoxicity screen­ing of chemicals, and the standard methods for this screening were proposed by the Organization for Economic Co-operation and Development (OECD) and other international or national or­ganization [9]. We investigated effects of acute y-irradiation and some heavy metals (manganese, nickel and copper) on the mobility of Daphnia magna according to the OECD method (OECD Guideline for Testing of Chemicals 202; Daphnia

Морський екологічний журнал, № 2, Т. iii. 2004

sp., acute immobilization test). The details of this study were reported elsewhere [7].

No significant effects on mobility of D. magna were observed at 24 hours after acute 1200 Gy irradiation, but 1350 Gy irradiation signifi­cantly immobilized this organism. The immobility rate of D. magna became higher with the increase in absorbed doses, and almost all individuals were immobilized at 2000 Gy. The dose-response curve was a sigmoid-shape, which is typically observed in lethality for irradiated animals such as rats, monkeys and so on. From this dose-response rela­tionship, the median effect dose (ED50), at which 50 % individuals of D. magna were immobilized, was estimated to be 1600 Gy (Table 1).

Table 1. Median effect doses (ED50) and Gy-equivalent factors (GyEFD) in the Daphnia immobilization test Tабл.  1.  Средние эффективные дозы (ED50) и Гр-эквивалентные   факторы  (GyEFD)  при тесте обездвижения Daphnia

 

y-rays

Heavy metals

 

 

Mn

Ni

Cu

ED501

1600 Gy

990 цМ

180 цМ

3.3 цМ

GyEFD2

1.6

8.9

480

1 Dose at which 50 % individuals of D. magna were immobilized;

2 ED50 of y-rays /ED50 of heavy metals.

Fractions of immobile D. magna were positively correlated with log-transformed doses of each metal, and the relationships between them could be fitted by sigmoid curves, which are typi­cally observed in dose-responses of organisms exposed to toxic chemicals. These dose-response relationships provided the estimation of the ED50s shown in Table 1.

The    equi-dosimetric    approach was

adopted for toxicity ranking of the heavy metals to

D. magna on the basis of y-rays. That is, the

Gy-equivalent factors for D. magna (GyEFD) were

defined by the following equation:

ED50 of y- rays

GyEFD=-50----- (1)

ED50 of heavy metals

The GyEFDs of the heavy metals con­cerned are shown in Table 1. The lager the GyEFD value is, the higher the toxicity is. Toxicity of the heavy metals to D. magna could be therefore ranked as Cu>Ni>Mn.

II.2. Microcosm ecotoxicity test

Microcosms are small scales of experi­mental model ecosystems constructed in the labo­ratory. They provide the biotic or abiotic simplic­ity, controllability and replicability, which cannot be expected in field studies. They also contain interspecies interactions as do natural ecosystems. This means that microcosm tests can evaluate not

2, Т. iii. 2004

only direct effects of toxic agents, but also com­munity-level effects due to interactions among the constituting species or between organisms and toxic agents, which cannot be evaluated by con­ventional single-species tests such as the Daphnia immobilization test described above [1].

We investigated ecological effects of y-rays [3] and various other toxic agents such as ultraviolet-C radiation (UV-C) [22], acidification [12], aluminium [8], manganese [5], nickel [4], copper [8], gadolinium (Gd; [6]) and dysprosium (Dy; Fuma et al., manuscript in submission) using a microcosm consisting of flagellate algae Eu-glena gracilis as a producer, ciliate protozoa Tet-rahymena thermophila as a consumer and bacteria Escherichia coli as a decomposer [10]. This mi­crocosm mimics essential processes in aquatic microbial communities [11].

That is, the microcosm is maintained with photoenergy which Eu. gracilis fixes by photo­synthesis. Metabolites and breakdown products of one species contribute to growth of the other two species. T. thermophila grazes E. coli as staple food. As a result of these interspecies interactions, these three species can co-exist for more than one year without addition of any nutrients. The mi­crocosm can be therefore regarded as a self-sustaining system. The microcosm can evalu­ate not only direct effects of toxic agents but also community-level effects, though it is very simple. For example, 100 цМ copper extinguished E. coli first and then T. thermophila in the microcosm. It is thought that this extinction of T. thermophila was not a direct effect of copper but indirectly arose from extinction of E. coli [8].

In general, degrees of effects observed in the microcosm exposed to each toxic agent were positively correlative with its dose. For example, acute irradiation by 50 or 100 Gy y-rays temporar­ily decreased the cell density of E. coli. At 500 or 1000 Gy, E. coli died out, and the cell densities of the other two species were decreased compared with controls. At 5000 Gy, all species died out [3]. For another example, at 1 or 10 цМ nickel, the cell densities of all species were not affected.

At 100 цМ, T. thermophila and E. coli died out. At 1000 цМ, all species died out [4]. Though effects observed in the microcosm were different in de­tails among the toxic agents, the microcosm gen­erally showed the following dose-response pattern corresponding to the radiochemoecological con­ceptual model: (1) "Ecological or physiological masking zone", i.e., no effects on the cell densities, but there might be some effects that did not lead to decrease in the cell densities; (2) "Number reduc­tion", i.e., decrease in the cell densities of at least one species; (3) "Species reduction", i.e., extinc­tion of one or two species; and (4) "Impoverish­ment", i.e., extinction of all species. According to this categorization, effect doses of the various toxic agents compared with ionizing radiation could be summarised as Fig. 3.

Zone of damages to ecosystems

Impoverishment

 

 

Species reduction Number reduction_________

 

 

Ecological or physiological masking zone

 

 

 

 

y-rays (Gy)

г |

50-100

500-1000

5000

UV-C (J/m2)

100

1000

5000

10000

Acidification

г I

pH 4

pH 3.5

г|

Al (мМ)

10

100-500

г|

1000

Мп (мМ)

г I

100-1000

10000

г I

Ni (мМ)

10

г|

100

1000

Cu (мМ)

10

г|

100

г I

Gd (мМ)

50

100

300

1000

Dy (мМ)

50-100

180

300-560

1000

г :| Not examined

Fig. 3. Effect doses of y-rays and other toxic agents for the microcosm evaluated by the radiochemoecological con­ceptual model

Рис. 3. Эффективные дозы гамма-лучей и других токсических агентов для микрокосма, определенные с по­мощью радиохемоэкологической модели

When "species reduction" is adopted as an endpoint, the Gy-equivalent factors for the mi­crocosm (GyEFM) in the equi-dosimetric approach can be defined by the following equation:

GyEF=       " Species reduction" dose of y - rays (2) " Species reduction" dose of other toxic agents

Table 2 shows the GyEFMs of the heavy metals concerned. Toxicity of these heavy metals to the microcosm could be therefore ranked as Cu=Ni>Gd>Dy>Mn. This toxicity rank was partly the same as that obtained from the Daphnia immo­bilization test described above. That is, both results of the microcosm and Daphnia tests indicated that

copper and nickel were more toxic than manga­nese. However, there was a noteworthy difference in the ecotoxicity rank between these toxicity tests. This difference was that copper and nickel had the same toxicity to the microcosm, while copper was more toxic to Daphnia than nickel. It is thought that this difference in the toxicity rank resulted from different sensitivities to these metals be­tween Daphnia and the species constituting the microcosm.

Table 2. Gy-equivalent factors for the microcosm (GyEFM)

Табл. 2. Гр-эквивалентные факторы для микрокосма (GyEFм)

 

Mn

Ni

Cu

Gd

Dy

GyEFM1

0.05-0.1

5-10

5-10

1.7-3.3

0.89-3.3

1 "Species reduction" dose of y-rays /"Species reduc­tion" dose of heavy metals

Main conclusions from experimental studies presented above are as follows. The equi-dosimetric approach makes it possible to rank ecotoxicity of various toxic agents on the basis of ionizing radiation, whose dose estimation and biological effects have been investigated more in detail than the other toxic agents. In the con­ventional single-species ecotoxicity test, i.e., the Daphnia immobilization test, the equi-dosimetric approach was useful for toxicity ranking of some heavy metals. In the microcosm test, the radio-chemoecological conceptual model was useful to categorise effects of ionizing radiation and some other toxic agents.

In addition to this model, the equi-dosimetric approach made it possible to rank toxicity of some heavy metals to the microcosm at the community-level. It is therefore thought that combination of the radiochemoecological concep­tual model and equi-dosimetric approach is useful for ecotoxicity ranking of various agents on the basis of ionizing radiation in complex microcosms and natural ecosystems. Such ecotoxicity ranking will contribute to a better choice of human activi­ties for conservation of ecosystems. That is, it will provide some scientific basis for replacement of harmful activities with less harmful ones.

III. LONG-TERM MONITORING OF THE BLACK SEA ECOSYSTEMS

All available data on the fate of species, populations and communities of the Black Sea, especially in its NW shelf area, were summarized [23 - 27].

The famous great benthic community of "the Zernov' Phyllophora field" consists of four species of red (agar-bearing) macroalgae - Phyl-lophora genus. They are key species of this very rich biocenosis in the Black Sea degraded to the tragic extent under severe anthropogenic impact in 1950 - 1990. Though this degradation was created under general influence of various anthropogenic activities, the main cause was the decline of water transparency due to eutrophication and increased number of phytoplankton and detritus in water column [23 - 25] (Table 3).

Table 3. Decline of habitat areas and biomass of Phyl-lophora species

Табл. 3. Уменьшение ареалов и биомассы видов

Phyllophora

Period, years

Inhabited area, km2

Total biomass, t

1950s

11000

10000000

1960s

7000

4000000

1980s

3000

1400000

1990

500

300000

One of dominated negative ecological fac­tors in the large area in front of the Danube river delta is eutrophication, which causes the lack of oxygen in near-bottom layer of water - hypoxic conditions ('hypoxia').

Here is a series of data on increase in its damaged area on the NW shelf at depths from 10

to 40 m in 1973 - 1990 [23 - 25]:

2, Т. iii. 2004

Equi-dosimetry of deleterious factors .

Year

1973

1974

1975

1976

1977

1978

1979

1980

1981

Damaged area, 103 km2

4

12

10

3

11

30

15

30

17

Year

1982

1983

1984

1985

1986

1987

1988

1989

1990

Damaged area, 103 km2

12

35

10

5

8

9

12

20

40

From 100 to 200 t of benthic invertebrates and fishes per 1 km2 died in a hypoxia period. During studied 18 years (1973 - 1990) 60 MT of bottom hydrobionts, including up to 5 MT of fishes, perished from hypoxia. Ecological situation in the NW shelf was somewhat improved in the second half of 1990s, but exact data on hypoxia areas are absent.

Severe impacts shown in Table 4 have been observed in the Black Sea shelf and estuarine ecosystems, populations and species. These im­pacts are quantitatively equivalent to the ecologi­cal effects of nuclear pollution/contamination in the Chernobyl NPP' nearest zone, the Kyshtym trail, the Karachay Lake, the other similar nuclear areas in the World. But dose rates of ionizing ra­diation to biota are less than 0.007 Gy/y in the Black Sea (Table 4). It is therefore thought non-nuclear pollution has caused the severe im­pacts in the Black Sea.

Table 4. Damage to ecosystems and populations of the Black Sea species caused by nuclear and non-nuclear pollu­tions [17]

Табл. 4. Поражение экосистем и популяций черноморских видов, вызванное ядерными и неядерными загряз­нениями [17]

Ecological damage assessments

[26]

Lethal Chronic Doses of Ionising Radiation,

Gy

[28]

Equivalent Lethal Chronic

Doses of Non-Nuclear Pollutions, Gy-eq./y [A]

Environmental Nuclear Sources, Gy/y [B] [13, 20, 21]

Ratio A/B

1

2

3

4

5

1.  Cystoseira barbata biocenosis > 99 % of its population size were lost since 1960s on Romanian & Ukrainian shelf under eutrophication & pollution impact.

For Thallophyta (including algae) 180 - 72000

180 - 72000

< 0.005

104 - 107

2.  Gen. Phyllophora biocenosis 97 % of population size were lost during 30 years on NW Black Sea under press of eutrophication, pollution & turbidity.

For Thallophyta (including algae) 180 - 72000

180 - 72000

< 0.005

104 - 107

3. Ostrea edulis

> 95 % of its population were lost during 30       For Mollusca years on the Black Sea shelf under turbidity       600 - 6000 action.

4. Mytilus galloprovincialis

60 % of its population were lost during 30       For Mollusca years on the Black Sea shelf under action of       600 - 6000 hypoxia, caused by eutrophication.

6. Gobiidae populations All 20 species were lost by 80 % of their populations on the shelf during 30 years        For Pisces under action of hypoxia on the bottom & 42 - 360

destruction of their breeding places.

600 - 6000

600 - 6000

< 0.007

< 0.007

105 - 106

105 - 106

42 - 360

< 0.007

104 - 105

Table 3. Contnd.

7. Marine Mammalia populations Dolphins (3 species, endemic subspecies) lost by 90-95 % of their populations sizes during 30 years as consequences of toxi­cants bioaccumulation & killing as bycatch in fisheries. Number of monk seal (Monachus monachus) decreased to few individuals (or to 0) because of lack of reproduction on coastal areas & toxicants bioaccumulation.

For Mammalia 12 - 90

12 - 90 < 0.006 103- 104

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