ISSN 19950829, Inland Water Biology, 2012, Vol. 5, No. 4, pp. 299–303. © Pleiades Publishing, Ltd., 2012. Original Russian Text © A.A. Protasov, 2012, published in Biologiya Vnutrennikh Vod, 2012, No. 4, pp. 5–10.
GENERAL HYDROBIOLOGIA
On the Interrelation of Diversity and Structural and Functional Indicators of Hydrobiont Communities A. A. Protasov Institute of Hydrobiology, National Academy of Sciences of Ukraine, pr. Geroev Stalingrada 12, Kiev, 04210 Ukraine email:
[email protected] Received January 12, 2011
Abstract—Empirically derived relationships between indicators of diversity of zoobenthos, zooperiphyton, and zooplankton and the structural characteristics of communities in reservoirs of various types are presented. The relationships between indicators of diversity, the biomass of communities, the spatial structure, and the ratio of energy stored in biomass and scattered energy have been elicited. Keywords: species diversity, taxonomic diversity, hydrobiont ecotopic groups, periphyton, benthos, plankton DOI: 10.1134/S1995082912040128
Diversity is a concept relevant to all parts of the study of life. There are some reasons to separate the section of ecology associated with the study of diver sity [10–12]; according to some authors [7] it is even a complex of doctrines. Biological diversity is becoming an academic discipline [8]. The United Nations declared 2012 as the year of diversity, reflecting the urgent need to preserve the richness of life on earth. Diversity is one of the most important characteristics of biotic communities. Diversity indicators are used to assess the complexity of a community [1]. A quantita tive expression of diversity is defined by both the rich ness of elements and their evenness, i.e., the relative representation (relative abundance) [5, 9, 10]. Diver sity is used as an independent characteristic of com munities, although a quantitative assessment is made on the basis of the richness of a cenopopulation and the abundance of organisms (abundance, biomass, etc.). It should be noted that an assessment of biotic community diversity may be based not only on quanti tative structural indicators such as abundance, biom ass, and oxygen consumption, but also on community composition. Alongside the abundance of individual populations and their relationship being determined by environmental conditions and biotic relationships, the number of species in taxa of higher rank is not accidental. Previously, the author [10] proposed the evaluation of characteristics of communities on the basis of taxonomic diversity. The ratio of species in trophic groups can be just as important a characteristic as the ratio of the abundance of representatives of var ious trophic groups. Thus, the concept of diversity of communities can be quite broad. The aim of this work is to identify the relationship between indicators of diversity and other characteris
tics of communities of ecological groups of aquatic organisms. Zooplankton, micro and macrozooperiphyton, and macrozoobenthos (450 samples in total) were investigated in different water bodies of Ukraine, such as cooling ponds of Krivoy Rog thermal power plant, Chernobyl, and Khmel’nitsk nuclear power plants (NPPs); the Styr’ River flowing in the area of the Rovno NPP; and Kanev (the Dnieper River) and Alexandrovsk (the Yuzhnyi Bug River) reservoirs. The Shannon index was used in a quantitative evaluation of diversity [9]. Since the species identification of aquatic organisms is not always possible, lower identifiable taxon [3] (LIT) diversity was determined instead of species diversity. The taxonomic diversity of zoob enthos was calculated using the Shannon index, taking into account the number of large taxa and the amount of LITs in them [10]. Taxa of different ranks, which in studies of benthos and periphyton are used as “hydro biological groups” such as Hydrozoa, Spongia, Nem atoda, Oligohaeta, Chironomidae and Trichoptera larvae, etc., were taken as “large taxa.” The relationship between indicators of diversity, calculated by the number (HN) and biomass (НB), has been positive, but not always welldefined (Fig. 1). The most strongly (correlation coefficient r = 0.55) related diversity indicators of microzooperiphyton communi ties are connected. In communities of zooplankton and microzooperiphyton, increases in HN and НB of ciliates are closely interconnected in the whole range of values and are mainly determined by the richness (number) of LITs. In macrozooperiphyton and zoob enthos, low values of НB and at the same time HN are defined by both a low richness of LITs and a low even ness, primarily connected with the high dominance in the biomass of largescale forms. Usually it is bivalves
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bit/specimen y = 0.1204x + 1.7251 R2 = 0.0151
(b)
(a)
3
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1
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y = 0.3654x + 1.708 R2 = 0.1766
bit/mg
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y = 0.2856x + 1.7153 R2 = 0.1377
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y = 0.6822x + 1.6612 R2 = 0.4186
1
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Fig. 1. The relationship between diversity calculated by biomass (x axis) and by number (y axis) in communities of (a) macrozo operiphyton, (b) zoobenthos, (c) zooplankton, and (d) microzooperiphyton.
(Dreissena species in this case). Their settlements cre ate favorable conditions for the development of many populations of mobile small forms of oligochaetes, leeches, gastropods, and insect larvae, etc., which leads to an increase in HN. In a series of communities with different rates of НВ, biomass is reduced (Fig. 2). For zooplankton, zoobenthos, and macrozooperiphyton, a negative powerlaw relation was ascertained: НВ = аВ–b, where В is biomass, a ranges from 1.080 to 34.094, and coef ficient b ranges from 0.201 to 0.907. A decrease in diversity with an increasing abundance was observed in a variety of communities and groups of aquatic organ isms [1, 5, 6, 10], which, apparently, can be considered one of the general environmental rules. A.F. Alimov ([1], p. 29) interprets a similar dependence as follows: as far as simplifying a structure of biological systems (reducing their diversity), as a result of pollution or the eutrophication of water bodies and streams, the biom
ass of communities increases.” In addition, biomass can increase for other reasons, such as seasonal fac tors. In this case, a community structure does not always become simpler in all aspects. Thus, as the bio mass of the attached forms increases, spatial complex ity increases. Most often, diversity is reduced by means of reducing evenness. Thus, an increase in biomass is usually due to only one species, which is reflected in the diversity index. According to the author, for the periphyton of a cooling pond of the Khmel’nitsk NPP, a correlation coefficient between biomass and even ness was 0.58; there was no real correlation between biomass and species richness. In this case, the increase in biomass was due to one species (zebra mussel). In zooperiphyton communities, not only can attached forms (sponges and bryozoans [13]) become such a dominant, but so can some insect larvae, such as midges and caddis larvae [14]. An exception to the general rule is microzooperiphyton communities, INLAND WATER BIOLOGY
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ON THE INTERRELATION OF DIVERSITY AND … INDICATORS bit/g
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bit/g (a)
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y = 34.094x–0.9071 R2 = 0.6978
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y = 1.3456x–0.2717 R2 = 0.3092
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bit/g (c) 8.6616x–0.2013
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y= R2 = 0.2195
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y = 0.0765ln(x) + 1.1289 R2 = 0.068
3 2 2 1
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102
104
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Fig. 2. The relationship between biomass (x axis) and diversity calculated by biomass (y axis) in communities of (a) macrozoope riphyton, (b) zoobenthos, (c) zooplankton, and (d) microzooperiphyton.
where an increase in diversity with increasing biomass is expressed quite weakly (Fig. 2d). Alongside an increase in the average weight of an individual in communities of macrozoobenthos, zooplankton, and zooperiphyton, the diversity index also decreased (Fig. 3). Coefficients of the power law for zoobenthos and macrozooperiphyton were from 0.485 to 0.911 (a) and from 0.309 to 0.503 (b); for zooplankton they were 3.239 and 0.090, respectively. No connection was found for micro zooperiphyton communities. By increasing the ratio of total biomass to the num ber of LITs, which with the full definition of species could be considered the average coenopopulations biomass, diversity, calculated by biomass, decreased. For microzooperiphyton, only the tendency of such a connection was noted. Coefficients of the inverse powerlaw relation for communities of zooperiphy INLAND WATER BIOLOGY
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ton, zooplankton, and zoobenthos were as follows: a ranged from 0.200 to 0.542 and b ranged from 1.211 to 1.585. The taxonomic diversity varied nonlinearly with a given number of LITs, since if there is one group (tax onomic diversity is zero), more than one LIT (species) was noted. With an increase in taxonomic diversity, diversity, calculated by number, increased (Fig. 4). The dependence was linear (r = 0.67). This can be interpreted as follows: in communities with a more uniform distribution of the abundance of LITs, their number in “large taxa” distributes more evenly. Taxo nomic diversity also increased with an increase in bio mass; i.e., with an increase in the latter, not only does the number of LITs increase, but their distribution within taxonomic groups becomes more even. Diversity is associated with the complexity of a community structure. However, an estimation of a
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bit/g
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(a) 100
10–2
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y = 0.4953x–0.3086 R2 = 0.4253
10–2
y = 0.9113x–0.5028 R2 = 0.5565
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bit/mg y = 0.4883x–0.3479 R2 = 0.396
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Fig. 3. The relationship between the average weight of a specimen (x axis) and diversity calculated by biomass (y axis) in commu nities of (a) macrozooperiphyton, (b) zoobenthos, and (c) zooplankton.
community structure cannot be unambiguous. An increase in the spatial complexity of periphyton or benthic communities, such as the formation of com munities of sedentary organisms, leads to an increase in species richness and diversity by number, but reduces diversity calculated by biomass. This is due to the fact that the actual complex spatial structure of communities creates a small number of populations, usually with large biomass. In freshwater periphyton and benthos, such organisms, the presence of which determines the complexity of a spatial structure, are attached to filtration mussels (Dreissenidae), bryozo ans, sponges, and filamentous algae. The diversity of communities is defined by both biotic interactions and habitat conditions. In general,
bit/specimen y = 0.947x + 0.3098 R2 = 0.5116 3
2
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Fig. 4. The relationship between taxonomic diversity (x axis) and diversity calculated by number (y axis) in com munities of zoobenthos. INLAND WATER BIOLOGY
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the dependence of diversity on different functional characteristics of a community is not rectilineal, but of an asymptotic nature. [15] As for environment condi tions, in particular the organic matter content, the species richness has no direct positive relationship with the abundance of the primary production. The seemingly logical assumption that the more food there is, the more diverse the consumers are is not made, so the dependence is unimodal in nature [2]. The greatest number of species occurs in some average trophic conditions. Usually, redistribution occurs at high trophicity so that the largest part of them is captured by a small number of populations; i.e., evenness and, respectively, diversity are reduced. In extreme conditions, such as in highlatitude waters, there may be a significant reduction in the species diversity of the interaction of two processes, a reduc tion of the species richness, and a decrease in evenness due to the high dominance of one species [4]. The relationships between indicators of aquatic communities and their structural characteristics led to the following conclusion. An increase in community biomass is usually due to the growth in the biomass of a few species, which leads to a decrease in biomass evenness and reduces diversity. With an increase in biomass, the spatial complexity of communities, the total richness of populations, and diversity can increase. With an increase in species richness in a community, the emergence of new groups (large taxa) is more likely than a significant increase in the species richness of one taxon of high rank, as follows from the positive relationship between taxonomic and species diversity. In an environmental gradient, the unimodal distribution of indicators of diversity should be expected. REFERENCES 1. Alimov, A.F., Elementy teorii funktsionirovaniya vod nykh ekosistem (Elements of the Theory of the Func tioning of Aquatic Ecosystems), St. Petersburg: Nauka, 2000. 2. Alimov, A.F., Studies on Biodiversity in the Plankton, Benthos, and Fish Communities, and the Ecosystems of Fresh Water Bodies Differing in Productivity, Biol. Bull., 2001, vol. 28, no. 1, pp. 75–83. 3. Bakanov, A.I., Using the Characteristics of Zoobenthos Diversity to Monitor the State of Freshwater Ecosys tems, in Monitoring bioraznoobraziya (Monitoring of Biodiversity), Moscow, 1997, pp. 278–282.
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