Abstract
Phytoplankton behaviour in the middle reaches of the Orinoco river (middle basin) is discussed in relation to the Intermediate Disturbance Hypothesis. Seven sets of samples were taken from two channels formed below the confluence of Meta and Orinoco rivers between September 1990 and August 1991. The Orinoco river channel (ORISMA-1) had many more species than the Meta river channel (ORISMA-2). Chlorophyceae dominated both, except during the rising water period when Bacillariophyceae were dominant. The quantitative dominancy alternates among Chlorophyceae, Bacillariophyceae and Cryptophyceae in both river channels, with minima averaging 14 329 and maxima of 1038 392 cells per liter. The phytoplankton concentration of both river channels is negatively correlated with variability in suspended sediments load. The Shannon-Weaver diversity for ORISMA-1 gives higher values than those from ORISMA-2 and oscillates between 1.37 to 3.52. Disturbances due to increases of water level and high concentration of suspended sediment can be the driving force governing phytoplankton behaviour in large rivers.
Similar content being viewed by others
References
Blanco, L. & L. Sánchez, 1986. Contribucion al estudio taxonómico de las Euglenophyta, Cyanophyta, Chlorophyta y Chromophyta del Medio Orinoco, bajo Caroní, Oracoa y algunas lagunas de inundacion (Venezuela). MEM. Soc. Cienc. Nat. La salle XLV 125–126: 7–48.
Connell, J. H., 1978. Diversity in tropical rain forest and coral reefs. Science 199: 1302–1310.
Conover, W. J., 1980. Practical nonparametric statitics. 2nd Edition. J. Wiley & Sons, Inc. New York: xiv + 493 pp.
Hamilton, S. & W. M. Lewis Jr., 1987. Causes of seasonality in the chemistry of a lake on the Orinoco river floodplain, Venezuela. Limnol. Oceanogr. 32: 1277–1290.
Hamilton, S., S. J. Sippel, W. M. Lewis Jr. & J. F. Saunders, 1990. Zooplankton abundance and evidence for its reduction by macrophyte mats in two Orinoco floodplain lakes. J. Plankton Res. 12: 345–363.
Lewis, W. M. Jr., 1988. Primary production in the Orinoco river. Ecology 69: 679–692.
Lewis, W. M. Jr., J. F. Saunders & R. Dufford, 1990. Suspended organisms and biological carbon flux along the lower Orinoco river. In: Weibezahn, F. H.; H. Alvarez & W. M: Lewis (Eds) The Orinoco river as an Ecosystem; Caracas: 269–300.
Lewis, W. M. Jr., J. F. Saunders & F. H. Weibezahn, 1984. Cross-sectional variation in the chemistry and the suspended sediment load of the Orinoco river at Ciudad Bol'var. Acta Cient. Venezolana 35: 382–385.
Lewis, W. M. Jr. & F. H. Weibezahn, 1985. Progress report on studies of the Orinoco river as an ecosystem. Informe IRNR. USB. 42 p.
Margalef, R., 1983. Limnologia. Ed. Omega, Barcelona. 1010 p.
Meade, R. H., F. H. Weibezahn, W. M. Lewis Jr. & D. Pérez Hernández, 1990. Suspended sediments budget for the Orinoco river. In: Weibezahn, F. H.; H. Alvarez & W. M. Lewis (Eds). The Orinoco river as an Ecosystem, Caracas: 55–80.
Nordin, C. F., C. C. Cranston & A. Mejia, 1983. New Technology for measurement water and suspended sediment discharge of large rivers. Proc. 2nd. Int. Symp. on River Sedimentation, Oct. 1983, Naujing Publ. Water Resources and Electric Power Press, Beijing China. 1145.
Patrick, R., 1988. Importance of diversity in the functioning and structure of riverine communities. Limnol. Oceanogr. 33: 1304–1307.
Reice, S. R., 1985. Experimental disturbance and maintenance of species diversity in a stream community. Oecologia 67: 90–97.
Reynolds, C. S., 1988. Functional morphology and adaptive stratigies of freshwater phytoplankton. In: C. D. Sandgren (ed.), Growth and Reproductive Strategies of Freshwater phytoplankton. Cambrigde University Press, Cambrigde: 388–433.
Saad, M. A. H. & S. E. Antoine, 1978. Limnologycal studies on the river Tigris, Iraq. III. Phytoplankton. Int. Revue ges. Hydrob. 63: 801–814.
Sabater, S., 1990. Phytoplankton composition in a medium-sized Mediterranian river: The Ter (Sapin). Limnetica 6: 47–56.
Sabater, S. & I. Muñoz, 1990. Succesional dynamics of the phytoplankton in the lower part of the river Ebro. J. Plankton Res. 12: 573–592.
Sánchez, L. & E. Vásquez, 1989. Hydrochemistry and phytoplankton of a major blackwater river (Caroní and a hydroelectric reservoir (Macagua), Venezuela. Arch. Hydrobiol. 33: 303–313.
Saunders, J. F. & W. M. Lewis Jr., 1989. Zooplankton abundance in the lower Orinoco river, Venezuela. Limnol. Oceanogr. 34: 397–409.
Sioli. H., 1968. Hydrochemistry and geology in the Brazilian Amazon region. Amazoniana 1: 267–277.
Sousa, P. S., 1984. Ann. Rev. Ecol. Syst. The role of disturbance in natural communities. 15: 353–391.
Vannote, M. G., Wayne Minshall, K. W. Cummings, J. R. Sedell & C. E. Cushing, 1980. The river continuum concept. Can. J. Fish. aquat. Sci. 37: 130–137.
Vásquez, E. & L. Sánchez, 1984. Variacion estacional del plancton en dos sectores del río Orinoco y una laguna de inundación adyacente. MEM. Soc. Cienc. Nat. La Salle. XLIV 121: 11–34.
Weibezahn, F. H., 1985. Concentraciones de especies químicas disueltas y transporte de sólidos suspendidos en el alto y medio Orinoco y sus variaciones estacionales (Febrero 1984–Febrero-1985). Informe de resultados. Convenio MARNR-PDVSA-USB. xxv + 229.
Weibezahn. F. H., 1990. Hidroquímica y transporte de sedimentos en el alto y medio Orinoco. In: Weibezahn, F. H.; H. Alvarez & W. M. Lewis (Eds.) The Orinoco river as an Ecosystem, Caracas: 150–210.
Weibezahn, F. H., A. Heyvaert & M. Lasi, 1989. Lateral mixing of the waters of the Orinoco, Atabapo and Guaviare rivers after its confluence in the Southern Venezuela. Acta Cient. Venezolana 40: 263–270.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Carvajal-Chitty, H.I. Some notes about the Intermediate Disturbance Hypothesis and its effects on the phytoplankton of the middle Orinoco river. Hydrobiologia 249, 117–124 (1993). https://doi.org/10.1007/BF00008848
Issue Date:
DOI: https://doi.org/10.1007/BF00008848