Abstract
There has been a strong research focus on optical properties in temperate estuaries but very much less in tropical estuaries. These properties comprise light and beam attenuation dominated by suspended particulate matter, Chl a, and CDOM. Spatially and temporally distributed data on optical properties in a tropical wet and dry estuary are compared and discussed in relation to those of temperate estuaries. Sampling in the Nha Phu estuary, Vietnam, consisted of five stations on a transect from head to mouth that was sampled four times during dry conditions and three times during wet conditions between May 2006 and April 2008. Methods comprised CTD, optical measurements, and water sampling for suspended matter, Chl a, and CDOM. Results showed high light attenuation—K d(PAR)—in wet conditions and low in dry. K d(PAR) was highest at the estuary head and lower in the outer part. Spatial and temporal variations in K d(PAR) were in general dominated by variations in suspended particulate matter concentrations in both wet and dry conditions. Chl a concentrations were low and showed no strong variations between wet and dry conditions. CDOM absorption coefficients were higher in wet conditions with high values at the head and lower in the central part of the estuary. The depth of the photic zone was reduced by up to 50% during wet conditions. A residence time in the estuary of 5–6 days was derived from the rate of change of K d(PAR) after a period of heavy rain and discharge of freshwater into the estuary. This complied with a residence time of four and a half days derived from a basic physical relation. Optical properties were in general comparable to temperate estuaries in dry conditions although Chl a concentrations were lower in Nha Phu. A second distinctive point, as compared to temperate estuaries, was the episodic character with days of strong rainfall followed by longer periods of dry weather. All sampling, both wet and dry, was carried out in the dry season which implies a less definitive perception of wet and dry seasons.
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References
Barthel, K., R. Rosland & N. C. Thai, 2009. Modelling the circulation on the continental shelf of the province Khanh Hoa in Vietnam. Journal of Marine Systems 77: 89–113.
Bowers, D. G. & E. G. Mitchelson-Jacobs, 1996. Inherent optical properties of the Irish Sea determined from underwater irradiance measurements. Estuarine, Coastal and Shelf Science 43: 433–447.
Bowers, D. G., G. E. L. Harker, P. S. D. Smith & P. Tett, 2000. Optical properties of a region of freshwater influence—The Clyde Sea. Estuarine, Coastal and Shelf Science 50: 717–726.
Christian, D. & Y. P. Sheng, 2003. Relative influence of various water quality parameters on light attenuation in Indian River Lagoon. Estuarine, Coastal and Shelf Science 57: 961–971.
Cloern, J. E., 1987. Turbidity as a control on phytoplankton biomass and productivity. Continental Shelf Research 7: 1367–1381.
Cloern, J. E., 1991. Annual variations in river flow and primary production in the South san Francisco Bay estuary (USA). In Elliot, M. & Ducrotoy (eds), Estuaries and Coasts: Spatial and Temporal Intercomparisons. Olsen and Olsen, Fredensborg: 91–96.
Cravo, A., M. Madureira, H. Felicia & M. J. Bebianno, 2006. Impact of outflow from the Guadiana River on the distribution of suspended particulate matter and nutrients in the adjacent coastal zone. Estuarine, Coastal, and Shelf Science 70: 63–75.
Di Toro, D. M., 1978. Optics of turbid estuarine waters: approximations and applications. Water Research 12: 1059–1068.
Dyer, K. R., 1997. Estuaries—A Physical Introduction. Wiley, Chichester: 195 pp.
Falkowski, P.G. & J.A. Raven, 2007. Aquatic Photosynthesis, 2nd ed. Princeton University Press, Princeton: 351 pp.
Fujiki, T. & S. Taguchi, 2002. Variability in chlorophyll a specific absorption coefficient in marine phytoplankton as a function of cell size and irradiance. Journal of Plankton Research 24: 859–874.
Gallegos, C. L., D. L. Corell & J. W. Pierce, 1990. Modelling spectral diffuse attenuation, absorption, and scattering coefficients in a turbid estuary. Limnology and Oceanography 35: 1486–1502.
Højerslev, N. K., N. Holt & T. Aarup, 1996. Optical measurements in the North Sea Baltic Sea transition zone. I. On the origin of the deep water in the Kattegat. Continental Shelf Research 16: 1329–1342.
Jerlov, N. G. 1976. Marine Optics, 2nd ed. Elsevier Oceanography Series, 14. Elsevier, Amsterdam: 371 pp.
Jørgensen, B. B., 1996. Case study—Aarhus Bay. In Jørgensen, B. B., K. Richardson (eds) Coastal and Estuarine Studies, Vol. 52. American Geophysical Union, Washington: 241 pp.
Kirk, J. T. O., 1994. Light and Photosynthesis in Aquatic Ecosystems. Cambridge University Press, Cambridge: 401 pp.
Kostoglidis, A., C. B. Pattiaratchi & D. P. Hamilton, 2005. CDOM and its contribution to the underwater light climate of a shallow, microtidal estuary in South-western Australia. Estuarine, Coastal and Shelf Science 63: 469–477.
Lund-Hansen, L. C., 2004. Diffuse attenuation coefficients K d(PAR) at the estuarine North Sea Baltic Sea transition: time-series, partitioning, absorption, and scattering. Estuarine, Coastal and Shelf Science 61: 251–259.
Lund-Hansen, L. C. & H. M. Sørensen, 2009. Parameterization of surface irradiance and primary production in Århus Bay, SW Kattegat, Baltic Sea. Hydrobiologia 620: 173–179.
Lund-Hansen, L.C., T.J. Andersen, M.H. Nielsen & M. Pejrup, 2010. Suspended matter,Chl-a, CDOM, grain-sizes, and optical properties in the arctic fjord-type estuary, Kangerlussuaq, West Greenland during summer. Estuaries and Coasts (Accepted)
McMahon, T. G., R. C. T. Raine, T. Fast, L. Kies & J. W. Patching, 1992. Phytoplankton biomass, light attenuation and mixing in the Shannon estuary, Ireland. Journal of the Marine Biological sAssociation U.K. 72: 709–720.
Pfannkuche, J., 2002. Optical properties of Otago shelf waters: south island New Zealand. Estuarine, Coastal and Shelf Science 55: 613–627.
Philips, E. J., T. C. Lynch & S. Badylak, 1995. Chlorophyll a, tripton, color, and light availability in a shallow tropical inner-shelf lagoon, Florida Bay, FL. Marine Ecology Progress Series 127: 223–234.
Smith, R. C. & K. S. Baker, 1981. Optical properties of the clearest natural waters (200–800 nm). Applied Optics 20: 177–184.
Strickland, J. D. H. & T. R. Parson, 1972. A practical Handbook of Seawater Analyses. Ottawa, Canada: 235 pp.
Van Maren, D. S. & P. Hoekstra, 2004. Seasonal variation of hydrodynamics and sediment dynamics in a shallow subtropical estuary: the Ba Lat River, Vietnam. Estuarine, Coastal and Shelf Science 60: 529–540.
Vant, W. N., 1990. Causes of light attenuation in nine New Zealand estuaries. Estuarine, Coastal and Shelf Science 31: 125–137.
Vant, W. N. & R. J. Davies-Colley, 1986. Relative importance of clarity determinants in Lakes Okaro and Rotorua. New Zealand Journal of Marine Freshwater Research 20: 355–363.
Wolanski, E., 2007. Estuarine Ecohydrology. Elsevier, Amsterdam: 157 pp.
Wolanski, E., N. N. Huan, L. T. Daos, H. N. Nhan & N. N. Thuy, 1996. Fine-sediment dynamics in the Mekong River Estuary, Vietnam. Estuarine, Costal and Shelf Science 43: 565–582.
Zhang, S. P. & B. Wang, 2008. Global summer monsoon rainy seasons. International Journal of Climatology 28: 1563–1578.
Acknowledgments
Director Bui Hong Long and staff at the Institute of Oceanography, Nha Trang, Vietnam, are thanked for their good cooperation and fine hospitality during the project “Hydrodynamics of Wet and Dry Estuaries” financially supported by Danish Research Council contract. Nr. 272-06-0582. Mr. Thrien is thanked for help during the field work.
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Handling editor: Luigi Naselli-Flores
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Lund-Hansen, L.C., Hai, D.N., Lam, N.N. et al. Optical properties of a tropical estuary during wet and dry conditions in the Nha Phu estuary, Khanh Hoa Province, south-east Vietnam. Hydrobiologia 644, 207–216 (2010). https://doi.org/10.1007/s10750-010-0114-1
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DOI: https://doi.org/10.1007/s10750-010-0114-1