In some regions I have noticed this phenomenon due strees and adverse environmental or hydrographical factors.Chlamydononas, Euglena and some other algal forms change their color due accumulation of pigments.
Dear Javad,
Could you please make few photomicrographs of the specimen which will aid in identification of the organism.I agree with Dr.Rao. It could even be HAB of Microcystis. Hope you will add few photomicrographs.
Dear Javad,
This is a typical picture for a algal 'water bloom'. The organism that is causing it may be quite different and you should send us photomicrographs for a proper identification. In any case, the algae may not be dead at all, but the over-growth has been pushed along the shoreline by the wind.
I think this may be an algal bloom as suggested by Dr. Rao and Dr. Jackson but Euglena change color from green to red. It may be some species of Microcystis but needs photographs of organisms
yes, the layer is formed by the dead micro-algae. if the layer is formed by diatom bloom then should be a considerable amount of DO change.
Dear all;
As I mentioned (also M.P. Arulmoorthy) there is no evidence about abnormal changes for DO saturation at lake water body. I think they are dead algae which is eliminated by some people from the lake shore.
It is necessary to do microscopical analysis and photomicrographs of the yellow-green layer for identification of the organism (probably more organisms).
Yes It is necessary to do microscopical analysis. But I did DO monitoring at a 24 hours period of time. I measured DO, DO%, EC and temperature with hourly frequency at surface and near bottom of the lake. I chose a place covered by this layer.
But I did not record any abnormal change in DO and DO% at either surface or near bottom. The data of the DO% was exactly like the data which I got last year at this time.
Dear Javad, Thanks for the updates, but you haven't mentioned for how many days you hv monitored the DO change this time and for how long times the bloom is found in this place. It seems that it is cornered due to wind flow and you may have measured the DO just after the accumulation of the algae in that place. You may continue DO measurement for at least 15 days and then you would have something to conclude!!
well, irrespective of long term observations, a simple 24 hours cycle , especially if with hourly onbservations, should be enough for a two-pronged decision: if O2 levels oscillate (increase from mrning to mid-afternoon and decrease at night, with a minimum before or during sunrise and maximum toward midafternoon, then you might be looking at live cells. if irrespective of time of the day and ofthe presence or absence or light O2 decreases, then you have a layer of dead stuff (probably algae, given the colour) consuming oxygen during decomposition (mainly bacteria respiration, in other words),
If neither happens, I can only think of some inorganic pigment (or maybe organic, but highly resistant to oxydation)
What is the characteristics of the Tabellaria genus?I mean the optimum temperature and TN/TP ratio?
and are the Tabellaria species produce poison (Toxin)?What are the impacts?
Dear Javad,
Iam adding the description of the genus(with reference) and a paper which will give you some information required by you.
The genus Tabellaria is characterized as follows:Cells form zig-zag colonies joined by mucilage pads, Valves are elongate with capitate ends, wider at the center than at the ends. A rimoportula (terminus of a tubular process appearing as a hyaline line) in the center of the valve face. Septae are present on the numerous copulae (girdle bands). Pseudoseptae may also be present.
Spaulding, S., and Edlund, M. (2008). Tabellaria. In Diatoms of the United States.
Good luck!