Given that the plankton is phytoplankton, it seems Rhizosolenoid diatoms such as Rhizosolenia sp. or Neocalyptrella robusta. But the picture needs far better resolution and scales. Note I'm not good at zoology.

Ya,  from the present resolution of the pic I also feel that this could be Rhizosolenia sp. and I also found them during one experiment on Arabian Sea water (off Kochi)

I fully agree with Haimanti and Koji, it is a Rhizosolenia sp. but for better identifying of this species need to pictures with high resolution.

Regards

This book can help you "Marine Phytoplankton Atlas of Kuwait’s Waters" Manal Al-Kandari, Dr. Faiza Y. Al-Yamani, Kholood Al-Rifaie

Thanks for the answers. The image took from FlowCAM, don't have a high resolution image of the same plankton. For this genus level may enough. Thanks.

Most probably Oscillatoria sp..Please go through the article on phytoplankton diversity of Indian sundarbans...IJMES publication by Mitra et al 2014

Sufia, this is no way Oscillatoria and it is Rhizosolenia and moreover this is from Arabian Sea and not from Sundarbans. Oscillatoria has very different filament stricture. This is very clearly a diatom and almost 99% Rhizosolenia sp.

According to the book Belevich suggested, Proboscia sp. may also have a chance because Proboscia can form blooms around there. I suppose that these cells should be described as Rhizosoleniaceae. Restricted description such as within genus or species often fail scientific adequacy. It should be hard to distinguish between Proboscia and Rhizosolenia from FlowCAM images.

Hello Koji,

I think Proboscia is a synonym for Rhizosolenia and has been considered as same genus in Algaebase and in many other sites. The species Proboscia alata was later used as Rhizosolenia alata. However, I had a picture of this species with a better resiluriob and I believe from the same species, it was collected from off Kochi, Arabian Sea. May it helps. 

Hey Biswas.

Thank you for the fine picture of Rhizosolenia setigera. Rhizosolenia alata is basionym of Proboscia alata, the latter is accepted in today's taxonomy (http://www.algaebase.org/search/species/detail/?species_id=Xf68d787e68b25f57). See also Takahashi et al. 1994 Diatom Research (http://www.tandfonline.com/doi/abs/10.1080/0269249X.1994.9705317?journalCode=tdia20#.VNdvP_msVeI). In brief, frustule ultrastructure of their apex differ considerably. Molecular identification may be awaiting as far as I know. Thank you.

Hi Koji,

Yes, I also identified this species as Rhizosolenia setigera.  I was sure from the apex structure under high power of the microscope, however I was only confused with this curved shape of this species. I know those literature you mentioned above and thanks a lot. I hope this answers would help Karnan Chinnadurai .....all the best.....

Hi Biswas

Thank you for the fruitful discussions :-)

I hope the success of Chinnadurai study and hope Chinnadurai acknowledge how the correct microscopy is difficult as we discussed, identifying one species/genus. Thank you.

Biswas,

The composite images provided can barely be seen.   Try again with one that can be magnified. 

Concerning an online collection of diatoms for use in their identification.  Here are two websites from the U.S.  to check out: 

http://clade.ansp.org/diatoms/collections/index.php

https://westerndiatoms.colorado.edu/

Best wishes!

http://westerndiatoms.colorado.edu/

http://clade.ansp.org/diatoms/collections/index.php

try Algaebase website

Hi Biswas and Chinnadurai,

I also identified R. setigera with some curves at an oceanic environment with high levels of anthropogenic activities. So, I assigned this curved shape was because of this kind of stress for now.

This example could be applied to your environments?

Best Regards,

Eveline Aquino.

Hello George,

Thanks for the link. However, I did not find R. setigera in any of those links and I tried many other online sites and catalogs. But a curved R. setigera was not found. I am quite sure after having looked at this species under 60x15 magnification that it must be R. setigera from its apical part.

Thanks Eveline for your post and I am now quite sure that the species is R. setigera. However, I do not think the place at least I collected the samples were under stress, since it was off shore. It could be some other reasons.

Thanks for your positive input.

All the best

Cheers

Haimanti

It could be R.setigera. But the fixed photo not clear enough to be confirmed even without scale.

Dear all:

In my opinion it is not possible to determine the genus of the material presented by Karnan based on the photographs presented by Karnan.

Karnan I recommend get Sundström’s doctoral thesis, Sundström (1986). The marine diatom genus Rhizosolenia. Lund University code LUNDBS / (NBBS-1008) / 1-196.

This author split Rhizosolenia  s. l. in several marine genera: Rhizosolenia s. str., Proboscia Sundström, Pseudosolenia Sundström as was pointed out in previous comments. The differential features between genera would not be visible in these pictures.

I also recommend you the paper about Rhizosolenia s. st., Neocalyptrella, Pseudosolenia, Proboscia by Sunesen & Sar (2007) in which you can see the necessary features for determining an Rhizosolenia s. str. as R. setigera.

https://www.researchgate.net/publication/233741615_Marine_diatoms_from_Buenos_Aires_coastal_waters_%28Argentina%29._IV._Rhizosolenia_s._str._Proboscia_Pseudosolenia_Neocalyptrella

Kind regards.

Eugenia

Article Marine diatoms from Buenos Aires coastal waters (Argentina)....

Definitely i agree with Eugenia.

I'm not even sure this is a diatom from the photos provided. It looks like it could be the freshwater genus Monoraphidium. What is the salinity where this was collected, or maybe there is a river/source of freshwater somewhere near?

You need better images for anyone to be able to provide a definitive answer - good luck!

Dear Researchers,

Thanks for the answers, advice and discussion.

I collected samples during July 2014 from 33PSU saline water of Arabian Sea. I attached some images though the specimens were slightly degraded.

Dear Karnan:

Your pictures show a species of Rhizosolenia, probably R. setigera but for determining the species certainly it is necessary to analyze the material with SEM. We never found curved specimens of this species.

Kind regards.

Eugenia

Thank you Dear Eugenia and all... This year we may get the fresh sample. I will try to image in SEM.

dear karnan. i have only seen first two ur images and it shows Rhizosolenia setigera.

Dear Eugenia,

You get a very usefull reference to Sundström (1986) thesis. But how to find it and what that Lund University code means?