Please have a look at this link and PDF attachment.

https://www.researchgate.net/publication/230578470_Primary_Production_by_Phytoplankton_and_Microphytobenthos_in_Estuaries

Article Primary Production by Phytoplankton and Microphytobenthos in Estuaries

Please have a look at this link also.

http://link.springer.com/chapter/10.1007%2F978-1-4612-4966-5_16

Dear Jayachandran,

you mean all living beings? reaction is too different. But working at the lab of the Danube and Limans (Estuaries) we found several interesting facts. Even desalinated the Estuary never lose completely its marutime or brackish water fauna. Look, please, my last presented publication about the Sassyk ciliates fauna! As well  what happened with this ineresting freshened basin after desalination are gathered in our book (as well my site). If estuary is of some large river and practically fresh, so marine fauna can penitrate over the deep relict river bad and it can be the very upper part of this type Estuary. Moreover  in this relic river bad is concentrated hydrogen sulphide that is suitable for anaerobic organismes od marine origin. I wrote about the Dnieper-Bug Estuary. As about tides it can stimulate exchange of the organismes but is not comfortable for a stable fauna. Therefore in the locality of the Estuary with abruptly changing regime it will be enough poor fauna, eg especially if salinity will be changing from 1-2 over 5-7 promille diapazone and back.

Extra interesting can be redistribution of the primary production of phytoplancton that can be consumpted in the deeper layers and in benthos...

I have enough much books on the question, so if necessary, call me by RG mailing, Will send.

Andrey