After reading several articles I am a bit confused concerning the benthic species taken into account for the calculation of species richness and index like I2EC. In the description of I2EC (Grall & Glemarec, 2003) it is mentioned that fixed epifauna should not be counted. What about the vagile epifauna such as many molluscs of hard substrates (Nassarius, Chitons ...) ? I don’t understand why they are listed in mudflat case. What about Serpulidae species like Spirobranchus ?
Concerning the AMBI, normally used in soft sediment habitats, the list of ecological groups contains species like: Balanus trigonus, Nassarius sp., Actinia sp., Tethya sp., Polycarpa sp.
Looks like every study has its own recipe, and it is not possible to know which benthic species are taken into account by the authors for the calculation of each index.
In my opinion, different indices (AMBI, I2EC) must use different lists (infauna with or without epifauna), and each list should be clearly detailled to ensure reproductibility and comparison.
Can anyone enlighten me on this subject ?
Hi, Nicolas,
the problem you faced is much wider than of using of special taxonomic categories for indication. E. g., trying to compare results by different authors working with microbenthos/mesobenthos I found that for total amount of biota in the area no possibility to have correct result! The reasons are different, like: different size limit of accepting organisms, different taxon of hydrobionts, even different sense of volume of term benthos etc.
Other - processing results for compare. Sometimes the type of distribution is different and means of population amounts cannot be compared correctly! As well doing with microfauna even hardly to differ dead and alive specimens (Foraminifera, Testacea et al.). Moreover, some planktonic species have resting stages in benthos (Cyclopoidea) and vise-versa.
Other extremely importance is biocoenotic relations that help for organisms to occupy unexpectedly atypical places.
So, what to do? I think that should use only good indicating taxonomic groups for every subsystem (like plankton, benthos, epiphyton etc.). If operating with macrogroups should not mix them with micro- or even meso-. Should be good statistical processing of quantitative result esp in generalizing. And nobody forbids to improve the proposed methods as the only criterion are practical field experience.
Andrey
In my opinion, these indexes are merely indicative in comparing different sites or made by teams using different sets of organisms to calculate the index. The use of this type of index is more useful in studying the evolution of a site over time or for comparison of nearby sites using the same base of organisms in all studies. Therefore, this issue is resolved. I hope I have helped. Greetings.
Most of the indices you refer to were developed for use with grab sample type data from soft substrates which produce quantitative or semi-quantitative species lists. They do not necessarily translate well to epibiota on hard substrates althouhg work is on-going on this. However, if wish to try I would say the main thing is that you standardise how you deal with the issues. For instance some authors simply remove colonial or vagile taxa from the data set. Other may give a score based on realtive coverage or abundance.
With all univariate type indices it is key to refer to your contextual data on pressures, disurbance etc when intepretating.
Dear
You can read this paper so.
http://vj.areo.ir/article_107814_9fa64740c86385870caf14d7d6f01bb7.pdf
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