Hi Akmal,

your question is very broad and there is no definite yes or no answer as there are so many benthic species and many of them tend to react differently to pollution.

But the two aspects you have mentioned are certainly important:

Many species have delicate gills (e.g. many Ephemeroptera and Trichoptera taxa) that are sensible towards acidification. A lower pH value due to the inflow of pollutants can reduce the efficiency of the gills and physically damage them.

The other aspect is that each species has a specific tolerance towards the level of dissolved oxygen. Prime examples for this are for instance many Plecoptera taxa. And adding pollutants into the water (especially those that are bioactive - like nutrients - Nitrate, Nitrit, Ammonium, Phosphate) increases the metabolic rate of a freshwater ecosystem (increased algae growth, increased microbial activity etc.) which overall increases the oxygen consumption, which in turn affects the more sensitive benthic organisms.

A third aspect is the toxicity of certain pollutants (e.g. pesticides or heavy metals) which directly influences the lethality of many benthic taxa.

And as you were asking about the resistance towards pollution - a fourth aspect can be the water temperature. The oxygen saturation, the solubility of pollutants and the enzyme activity (both for the macrozoobenthos and for germs/parasites) are all controlled by the water temperature which thus also affects the overall fitness of a species and its ability to tolerate less than optimal environmental conditions.

In many ways make trichoptera sensitive to pollution such as clock gills, lack oh oxygen.

Dear Akmal,

I agree with Michael that cannot select one factor, as there is a large spectrum of possible reasons.But the very important is a size of a watercouse as for dilution of contaminating factor. If you have to do with a small creek or brook the benthic invertebrates and protists will be much more sencitive for disturbing factors!!! Large basins are much more stable. As well I agree with great importance of pH as low index of pH stimulates appearance of ionic form of heavy metals - the most dangerous for living beings. pH changes in small watercouses can be dependent on the primary productivity of phytomicrobenthos and periphyton on pebbles (mountain area) mainly (shallow) and can change from down till dusk from 6,5 till even 9,5-10!

But the biocenotic relations that produce such problems for a sepatare group are still not enough investigated. I'm working now on a Chapter for one book and this is about unfluence of biocenotic relations on geographical distribution. I propose you to read the beginning of second subchapter, may be it will make some aspects more clear:

1.1       The impact of biocenotic relations on the geographic distribution of invertebrates.

I should note that the distribution of different species depends to a large extent not only from factors of a biological nature (climatic, geological), but also from the biocenotic relations, formed in the ecosystems (fig. ). Obviously, given scheme is simplified, but it is quite effective when considering small ecosystems and ecosystems of dependent type.

Gause experiments...

It is also clear that if happen changes even of a small amount of positive bilateral relations into unilateral, although positive, moreover into weaker – neutral or negative can start not only short-term or seasonal successions in ecosystems.

If such changes are long-term and irreversible, especially if they relate to edificatory or even just dominating species in monodominant ecosystems, that means the evolution of these ecosystems can go a completely different way. Destroying of corals in the Great Barrier Reef by star-fish, Crown-of-thorns – Acanthaster planci (L.) is a well-known example. In a two and a half-year period only, about 90 percent of the coral was killed along 38 kilometers of the shoreline of island Guam of the Pacific Ocean (Chesher 1969). Until the middle of the last century this star-fish has been regarded as a great rarity. This is a man-caused activity (dredging & blasting) in coral devastating that stimulates the developing of the star-fish in greater amount, because corals are filtering the star-fish planktonic larvae (Ibid.), so, usually, the system coral-star-fish is perfectly balanced. Appearance of large spots of suitable for hatching in great amounts of bipinnaria larvae of Crown-of-thorns is a factor that destroys balance.

Chesher R. Destruction of Pacific Corals by the Sea Star Acanthaster planci // Science. – 1969. – Vol. 165. – P. 280-283.

It is obvious that in human modified ecosystems (e.g. agroecosystems) grazing species (one-way negative influence), which is usually rare in nature can become pests, and their spread would depend on the food plant.

Andrey

Hi everyone,

Thank you for replying to my question. Since pollution comes from many possible factors and they can work in synergy or not, it is hard to inspect the damage done just by physical inspection. Maybe I should try seeing this from cellular level if that may feed my curiosity.

tow reasons: first to have gill that are sensitive to particles and second to have case and finally kind of feeding that they need the creatures are living in clean water