Phytoplankton dynamics; Bio-optical algorithms; SeaDAS process optimization; MODIS Aqua; Lake Tanganyika
Abstract :
[en] Lake Tanganyika is one of the world's great freshwater ecosystems. In recent decades its hydrodynamic characteristics have undergone important changes that have had consequences on the lake's primary productivity. The establishment of a long-term Ocean Color dataset for Lake Tanganyika is a fundamental tool for understanding and monitoring these changes. We developed an approach to create a regionally calibrated dataset of chlorophyll-a concentrations (CHL) and attenuation coefficients at 490 nm (K490) for the period from July 2002 to December 2006 using daily calibrated radiances retrieved from the MODIS-Aqua sensor. Standard MODIS Aqua Ocean Color products were found to not provide a suitable calibration for high altitude lakes such as the Lake Tanganyika. An optimization of the extraction process and the validation of the dataset were performed with independent sets of in situ measurements. Our results show that for the geographical, atmospheric and optical conditions of Lake Tanganyika: (i) a coastal aerosol model set with high relative humidity (90%) provides a suitable atmospheric correction; (ii) a significant correlation between in situ data and CHL estimates using the MODIS specific OC3 algorithm is possible; and (iii) K490 estimates provide a good level of significance. The resulting validated time series of bio-optical properties provides a fundamental information base for the study of phytoplankton and primary production dynamics and interannual trends. A comparison between surface chlorophyll-a concentrations estimated from field monitoring and from the MODIS based dataset shows that remote sensing allows improved detection of surface blooms in Lake Tanganyika.
Disciplines :
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others Engineering, computing & technology: Multidisciplinary, general & others Life sciences: Multidisciplinary, general & others
Clark D.K. MODIS algorithm theoretical basis document. Bio-optical algorithms-Case 1 waters (1997). http://eospso.gsfc.nasa.gov/ftp_ATBD/REVIEW/MODIS/ATBD-MOD-18/atbd-mod-18.pdf Version 1.2 50 pp. http://eospso.gsfc.nasa.gov/ftp_ATBD/REVIEW/MODIS/ATBD-MOD-18/atbd-mod-18.pdf
Cocquyt C., and Vyverman W. Phytoplankton in Lake Tanganyika: a comparison of community composition and biomass off Kigoma with previous studies 27 years ago. Journal of Great Lakes Research 31 4 (2005) 535-546
Descy J.-P., Hardy M.-A., Sténuite S., Pirlot S., Kimirei I., Sekadende B., et al. Phytoplankton pigments and community composition in Lake Tanaganyika. Freshwater Biology 50 (2005) 668-684
Fu G., Baith K.S., and McClain C.R. SeaDAS: The SeaWiFS Data Analysis System. Proceedings of "The 4th Pacific Ocean Remote Sensing Conference", Qingdao, China, July 28-31, 1998 (1998) 73-79
Gordon H.R., and Voss K.J. MODIS normalized water-leaving radiance algorithm theoretical basis document (1999). http://modis.gsfc.nasa.gov/data/atbd/atbd_mod17.pdf Version 4, 96 pp. modis.gsfc.nasa.gov/data/atbd/atbd_mod17.pdf
Gordon H.R., and Wang M. Surface-roughness considerations for atmospheric correction of ocean color sensors. I. The Rayleigh-scattering component. Applied Optics 31 (1992) 4247-4260
Gordon H.R., and Wang M. Retrieval of water-leaving radiance and aerosol optical thickness over the oceans with SeaWIFS: A preliminary algorithm. Applied Optics 33 (1994) 443-452
Hecky R.E., and Kling H.J. The phytoplankton and the protozooplankton of the euphotic zone of Lake Tanganyika: Species composition biomass chlorophyll content and spatial-temporal distribution. Limnology and Oceanography 26 3 (1981) 548-564
Hecky R.E., Spigel R.H., and Coulter G.W. The nutrient regime. In: Coulter G.W. (Ed). Lake Tanganyika and its life (1991), Oxford University Press, Oxford 76-89
Jeffrey S.W., Mantoura R.F.C., and Wright S.W. Phytoplankton pigments in oceanography (1997), SCOR - UNESCO, Paris 661 pp
Kirk J.T.O. Optics of UV-B radiation in natural waters. In: Williamson C.E., and Zagarese H.E. (Eds). Impact of UV-B radiation on pelagic freshwater ecosystems, Schweizerbart, Stuttgart (1994) 1-16
Mackey M.D., Mackey D.J., Higgins H.W., and Wright S.W. CHEMTAX - A program for estimating class abundances from chemical markers: Application to HPLC measurements of phytoplankton. Marine Ecology Progress Series 144 1-3 (1996) 265-283
Mölsä H., Reynolds J.E., Coenen E.J., and Lindqvist O.V. Fisheries research towards resource management on Lake Tanganyika. Hydrobiologia 407 (1999) 1-24
Mueller J.L. SeaWiFS algorithm for the diffuse attenuation coefficient, K(490), using water-leaving radiances at 490 and 555 nm. In: Hooker S.B., and Firestone E.R. (Eds). SeaWiFS postlaunch technical report series. SeaWiFS postlaunch calibration and validation analyses, part 3 Vol. 11 (2000), NASA, Goddard Space Flight Center, Greenbelt, Maryland 24-27
Naithani J., Deleersnijder E., and Plisnier P.-D. Origin of intra-seasonal variability in Lake Tanganyika. Geophysical Research Letters 29 (2002) 10.1029/2002GL015843
Naithani J., Deleersnijder E., and Plisnier P.-D. Analysis of wind-induced thermocline oscillations of Lake Tanganyika. Environmental Fluid Mechanics 3 (2003) 23-29
Naithani J., Plisnier P.-D., and Deleersnijder E. A simple model of the eco-hydrodynamics of the epilimnion of Lake Tanganyika. Freshwater Biology 52 (2007) 2087-2100
O'Reilly C.M., Alin S.R., Plisnier P.-D., Cohen A.S., and McKee B.A. Climate change decrease aquatic ecosystem productivity of Lake Tanganyika, Africa. Nature 424 (2003) 766-768
Plisnier P.-D., and Coenen E.C. Pulsed and dampened annual limnological fluctuations in Lake Tanganyika, the Great Lakes of the World (GLOW): Food-web, health and integrity. In: Munawar M., and Hecky R. (Eds). Ecovision World Monograph Series, Leiden, The Netherlands (2001) 81-94
Plisnier P.-D., and Descy J.-P. CLIMLAKE: Climate variability as recorded in Lake Tanganyika. Global change, ecosystems and biodiversity SPSD 2, research project EV/13/02. Final report (2001-2005) (2005), Science Policy office, Belgium 105 pp
Plisnier P.-D., Chitamwebwa D., Mwape L., Tshibangu K., Langenberg V., and Coenen E.C. Limnological annual cycle inferred from physical-chemical fluctuations at three stations of Lake Tanganyika. Hydrobiologia 407 (1999) 45-58
Plisnier P.-D., Mgana H., Kimirei I., Chande A., Makasa L., Chimanga J., et al. Limnological variability and pelagic fish abundance (Stolothrissa tanganicae and Lates stappersii) in Lake Tanganyika. Hydrobiologia 625 1 (2009) 117-134 10.1007/s10750-009-9701-4
Sarmento H., Leitao M., Stoyneva M., Compère P., Couté A., Isumbisho M., et al. Species diversity of pelagic algae in lake kivu (east africa). Cryptogamie, Algologie 28 3 (2007) 246-269
Smith R., and Baker K.S. The bio-optical state of ocean waters and remote sensing. Limnology and Oceanography 23 (1978) 247-259
Stenuite, S. (2009). Le picoplancton du Lac Tanganyika : Nature, biomasse et production. PhD. Thesis, University of Namur, Namur, Belgium, 326 pp.
Verburg P., Hecky R.E., and Kling H. Ecological consequences of a Century of warming in Lake Tanganyika. Science 301 (2003) 505-507
Verschuren D. The heat on Lake Tanganyika. Nature 424 (2003) 731-732
Vuorio K., Nuottajärvi M., Salonen K., and Sarvala J. Spatial distribution of phytoplankton and picocyanobacteria in lake tanganyika in march and april 1998. Aquatic Ecosystem Health and Management 6 3 (2003) 263-278
Wright S.W., and Jeffrey S.W. Pigment markers for phytoplankton production. In: Volkman J.K. (Ed). Marine organic matter: biomarkers, isotopes and DNA. Handbook of environmental chemistry Vol. 2 (2006), Springer, Berlin Part N 374pp
