Polluted ecosystems bioindicators
 
1-Cerastoderma glaucum- olive green cokle - 30 mm in length
The  says "olive green" cockle  may be put at the first rank of bioindicator species living in highly disturbed habitats characterized   by very large variations of water's temperature and salinity  and, before all, by high pollution with strong eutrophication.
This species is,  byway, typical of lagoonary environment.
It lives in the Tunis lake or in the Ichkeul lake where salinity's can reached 65°/°°.

Eutrophication =this phenomena is to be related, principally, with nutrients input by discharges in the medium of urban , industrial  or agricultural waterwastes.

2-Abra tenuis-  12 mm in length-
Like Cerastoderma glaucum this species lives in lagoons  with very large variations of water's temperature and salinity  and strong eutrophication.
It lives in the Tunis lake and in the Ichkeul lake.
 

3-Nassarius corniculus- horned nassa-  20 mm in length
This gastropod  is abundant in all the eutrophic lagoons where it lives in  areas with large amount of algae.
 


4-Gastrana fragilis -  22 mm in length
This species  which has red blood  coloured by  haemoglobin can lives in very  polluted bottoms where oxygen is rare.
It toleres very low salinities and, therfor, may lives in areas where they are sewage discharges like in the Tunis lake.
Photos by J. Zaouali