Diversity indexes

In several cases, such as shellfish areas and aquatic reserves, the usual water quaUty parameters do not apply because they are nonspecific as to detrimental effects on aquatic life. Eor example, COD is an overall measure of organic content, but it does not differentiate between toxic and nontoxic organics. In these cases, a species diversity index has been employed as related to either free-floating or benthic organisms. The index indicates the overall condition to the aquatic environment. It is related to the number of species in the sample. The higher the species diversity index, the more productive the aquatic system. The species diversity index is computed by the equation K- = (S — 1)/logjg I, where S is the number of species and /the total number of individual organisms counted. 

In the second publication (Bombardier and Blaise, 2000), laboratory toxicity data derived from two larger projects conducted on freshwater sediments were integrated in the SED-TOX index and it was field validated using four benthic community metrics (species richness, number of taxa in the orders Ephemeroptera, Plecoptera, and Trichoptera, the Shannon-Wiener diversity index, and the ICI-SL which is a version of the Invertebrate Community Index modified for the St. Lawrence River). 

Simpson s Evenness Expressing Simpson s Diversity Index, D, as a proportion of Index the maximum possible value of Ds assumes individuals were... 

After establishing a phylogenetic tree, further analysis can be pursued to determine patterns in diversity within and across communities. Phylogenetic diversity (PD) can be determined with the aid of programs like DOTUR (84), and DIVERSITY (85). DOTUR calculates the Shannon-Weiner index, a calculation of diversity based on how predictable the community is, and the Simpson diversity index, a calculation based on both the number of different samples in a community and their proportions in addition to several richness estimators. DIVERSITY calculates PD a diversity index that summates... 

Aquatic microcosms and mesocosms offer the ideal situation to investigate populations of species interacting in their natural environment (i.e., to study communities stressed in structured systems see Section 4.5.1). It is, however, only recently that these experiments have been analyzed at the community level (Van Wijngaarden et al. 1995 Sparks et al. 1999 van den Brink and Ter Braak 1999). Until 10 years ago, experiments were evaluated at the population level, largely ignoring species interactions and energy flows in the systems. The development of community-level endpoints offered the possibility to evaluate the experiments on a community level (i.e., they offered the opportunity to scale up the level of evaluation Kedwards et al. 1999). Summary community-level endpoints calculated from the results of these experiments are mostly structural ones measures of diversity (e.g. numbers of species, and the Shannon-Weaver diversity index) and similarity of the treated systems compared to the untreated controls (e.g., the principal response curves method, Bray-Curtis dissimilarity, or Stander s index see van den Brink and Ter Braak 1998 for a comparison). 

Figure 9. Optimisation of a diversity index via exhaustive subset enumeration...

Any type of selected descriptor will provide a more or less complex characterization of each virtual library component. The use of similarity indices offers a straightforward method to evaluate similarities between virtual compounds. These indices use a bit-string representation for any descriptor (distances, fingerprints, pharmacophores, and so on) and, by simply counting the presence or the absence of specific bins and comparing the bit strings of virtual compounds, provide a numerical similarity index. The formula for the commonly used Tanimoto similarity index (71, 43), which can readily be transformed into the complementary diversity index, is reported in Fig. 5.14... 

One of the most widely used indexes of community structure has been species diversity. Many measures for diversity are used, from such elementary forms as species number to measures based on information theory. A decrease in species diversity is usually taken as an indication of stress or impact upon a particular ecosystem. Diversity indexes, however, hide the dynamic nature of the system and the effects of island biogeography and seasonal state. As demonstrated in microcosm experiments, diversity is often insensitive to toxicant impacts. 

Thermodynamics of Coral Diversity — Diversity Index of Coral Distributions in Amitori Bay, Iriomote Island, Japan and Intermediate Disturbance Hypothesis... 

Keywords Coral life form, Diversity index, Information entropy, Intermediate disturbance hypothesis... 

In this section, the generality of the results is discussed by conducting a statistical analysis of the data obtained in the previous sections. The diversity index, H [29-32] is calculated and is defined as follows ... 

Relationship between diversity index and environmental properties... 

Figure 9. Diversity index at Stations 1-26 and A-R. The mouth, intermediate, and inner area of the bay are indicated in green, blue, and red, respectively (after [18]).

Figure 12. Relationship between diversity index and the coverage of tabular or branching corals at Stations 1-26 and...

Averages of diversity index of the coral types at the mouth and inner area of the bay with high environmental disturbances were lower than the average of the entire area. However, the average of the diversity index at the intermediate area of the bay with intermediate environmental disturbances was higher than it. This seems to support the IDH demon-... 

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