Hi Bhavya

Salinity of water is one of the most important parameters that control life in the estuaries. Salinity in an estuary is a function of the river/land discharge, local rainfall and tidal amplitude. Consequently, communities living in estuaries are adapted to withstand a certain range in fluctuation of salinity and therefore show complex pattern of distribution along the salinity gradient of the estuary from the upstream to its mouth.

There are so many papers dealing with the issue that you have raised. Some of them are cited below that deals with phytoplankton and salinity regimens:

1. J. W. Rijstenbil, Selection of phytoplankton species in culture by gradual salinity changes. Netherlands Journal of Sea Research, 1988, 22, 291–300.

2. Kies, L., 1997. Distribution, biomass and production of planktonic and benthic algae in the Elbe Estuary. Limnologica 27, 55–64.

3. R. R. L. Guillard, 1962. Salt and osmotic balance. In Lewin, R.A. (ed.), Physiology and Biochemistry of Algae: 929 Academic Press, New York and London.

4. A. Flameling, J. Kromkamp, Responses of respiration and photosynthesis of Scenedesmus protuberans Fritsch to gradual and steep salinity increases. Journal of Plankton Research, 1994, 16, 1781–1791.

5. http://www.liv.ac.uk/hab/Data%20sheets/a_peru/limpoteensalinity.pdf

Best

Dola

Thank you Dr. Dola

I am working on nitrogen cycle in estuarine region. I got a positive relationship btw salinity and uptake rates. So I was wondering how this ecosystem is adjusting with this much fluctuating salinity conditions.

Uptake rate of what? and what is the salinity range at your work site? You may also refer to: Morris, A.W., Mantoura, R.F.C., Bale, A.J., Howland, R.J.M., 1978. Very low salinity regions of estuaries: important sites for chemical and biological reactions. Nature 274, 678-680

Thank you so much for suggesting papers. I do labelled 15N tracer experiments to estimate the nitrate and ammonium uptake rates. In my study area salinity varies from 0- 20. It may change with tidal status.

Salinity in estuaries is a major determinant of biological activity that's why reports have documented the existence of 2 categories of species living in estuaries, i.e. Euryhaline (Adapted for wide fluctuations in salinity), Stenohaline (adapted to a narrow range of salinity). Certain reports have shown that organism metabolic requirements particularly fishes are often lower in higher salinities, thus they do not reproduce during the period of high salinites.

..with regards to uptake of nutrients, some euryhaline fish species like tilapia under experimental conditions have been reported to have a lower food intake, and this occurrence is currently being explored for the purpose of affordable aquaculture.

Dear Chukwuka

Thank you for you answers. It is interesting that fishes will also have affected with salinity. My work is mainly concentrating on phytoplankton uptake of nitrate and ammonium and also carbon fixation. So I was just wondering what is mechanism that make them behave in different way to accustomed with varying salinity conditions.

Hi Bhavya

There are physiological mechanisms by which estuarine organisms osmoregulate even under fluctuating salinity conditions. If interested you may look into:

1. http://www.scielo.br/pdf/ni/v6n4/v6n4a09.pdf

2. http://dyuthi.cusat.ac.in/xmlui/bitstream/handle/purl/101/Dyuthi-T0163.pdf?sequence=8

3. http://ajpregu.physiology.org/content/295/2/R704.full.pdf+html

So those which can tolerate a wide range of salinity fluctuation are called euryhaline while those that live in a narrow range of fluctuating salinity condition are called stenohaline. It all depends on the capability of the concerned organism to osmoregulate and cope with the fluctuation.

Best

Dola

Hi Bhavya...just some extra information

The physicochemistry of the estuarine medium has been documented to affect the rate of uptake of metals from solution by biota. For instance the uptake rate of a metabolically important metal, zinc, by biota from solution increases with decrease in salinity in the estuary and vice versa irrespective of total dissolved concentrations in water.

In other words, the bioavailability of ionic nutrient substances to estuarine biota are more likely to be dependent on the physicochemistry of the estuarine medium irrespective of the total dissolved concentration in the water.

I ,m not sure of your research question. If you are interested in the response of a species community response to its contribution to nitrogen cycling within an estuary then understanding how the species community is affected by by salinity dynamics within the various zones of the estuary is important. However, this is a different question to how salinity dynamics characteristic of an estuary at different time scales affect the nitrogen cycling dynamics of a community that has evolved over the appropriate time scale within estuarine zones. I other words salinity and its variance for that zone with respect to the turnover times of the microbiological community and its affect on the sediment redox , maybe a longer response time, may affect the efficiency of one of the nitrogen cycling processes e.g denitrification, or nitrogen fixation, . The issue then becomes a matter of scale, seasonal and and weekly salinity variability and changes to those parameters due to land use and climate change

Scale is every thing in ecology as its increasingly being realised

All the best

Barry

Hello, Just to suggest you to visit S. Bouillona, from invertebrate topics like:

Estuarine, Coastal and Shelf Science (2002) 54, 901–913

doi:10.1006/ecss.2001.0864, available online at http://www.idealibrary.com on

Carbon and Nitrogen Stable Isotope Ratios of Subtidal

Benthic Invertebrates in an Estuarine Mangrove

Ecosystem (Andhra Pradesh, India)

S. Bouillona*, A. V. Ramanb, P. Daubyc and F. Dehairsa

They have good paper about the subject you are asking

Dear Bhavya,

I, m little bit confuse with your question............ How does salinity variation in estuarine regions affect the biological activities over there means?

Hope these references may help to your work

Sarma, V.V.S.S.; Gupta, S.N.M.; Babu, P.V.R.; Acharyya, T.; Harikrishnachari, N.; Vishnuvardhan, K.; Rao, N.S.; Reddy, N.P.C.; Sarma, V.V.; Sadhuram, Y.; Murty, T.V.R.; DileepKumar, M. Influence of river discharge on plankton metabolic rates in the tropical monsoon driven Godavari estuary, India Estuar. Coast. Shelf Sci.: 85(4); 2009; 515-524.

T. Acharyya, V.V.S.S. Sarma ⁎, B. Sridevi, V. Venkataramana, M.D. Bharathi, S.A. Naidu, B.S.K. Kumar, V.R. Prasad, D. Bandyopadhyay, N.P.C. Reddy, M.D. Kumar. Reduced river discharge intensifies phytoplankton bloom in Godavari estuary, India. Marine Chemistry 132-133 (2012) 15–22

Thank you all for your suggestions. I will explain my questions: Actually, I work on the Nitrogen uptake mechanism in the estuary and coastal waters using 15N tracer technique. During my study I observed that there a positive relationship between uptake rate and salinity.

So my question is what will happen to the phytoplankton body when it is subjected to salinity variation. And in estuary, there will be two types of organisms mainly. Euryhaline and stenohaline. So how they react to the salinity variation?