Influence of the hidrometric variation in the phytoplankton in the transition zone Paranapanema river: Jurumirim reservoir (SP)

Author(s)

Danielli Cristina Granado

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2008-10-03

Examining board members

Raoul Henry; Carlos Eduardo de Mattos Bicudo; Maria do Carmo Calijuri; Jandira Liria Biscalquini Talamoni; Andréa Tucci

• Advisor: Raoul Henry

Abstract

With objective of understanding the influence of the hidrometric variation in the structure of phytoplankton community form Paranapanema river community fitoplanctônica and of three lateral lakes (Camargo, Coqueiral and Cavalos) with different association levels with the course of water, located in the transition area with the Dam of Jurumirim monthly samplings were accomplished in the subsuperfície and in the bottom of the atmospheres, in the period of July of 2004 to July of 2005. Of November 11, 2004 on February 10, 2005, the collections subsuperficiais passed to be accomplished twice in the week, totaling 27 samplings. With the samples physical and chemical analyses were accomplished (temperature of the air and of the water, precipitation, transparency of the water, electric conductivity, alkalinity, dissolved oxygen, pH, nutrients presents and speed of the current in Rio) and biological (chlorophyll more feofitina, wealth, composition, abundance, occurrence frequency, density, biovolume, diversity indices, dominance, equitability, structures of size of the organisms and tax of the community\'s modification). In function of the hidrometric variation, five periods were defined: falling of 2004 (July to September of 2004), low water (October to December), rising (January and February), high water (March and April) and falling of 2005 (May, June and July of 2005). The Lakes Camargo and Coqueiral, for they be permanently associated Rio Paranapanema presented a similar pattern amongst themselves and with the course of water, in relationship the physical and chemical variables, except for the dissolved oxygen. While the Cavaloss Lake, for being an isolated atmosphere and of smaller dimensions it presented a dynamics different from the other bodies of water. The phytoplankton community of the mouth zone of the Paranapanema River into the Reservoir of Jurumirim in the year of study was composed for 180 táxons, of the which the class Chlorophyceae was responsible for more than 40% of the total. The seasonal phytoplankton variation can be attributed, mainly, the fluctuation of the hidrometric level. The low water period was characterized by low densities and biomasses (but the smallest ones were registered in the beginning of the falling of 2004) and high diversity values. While the rising phases and high water presented high densities and biomasses, acted, especially, for the class Cryptophyceae (Cryptomonas brasiliensis) and, intermediate levels of diversity. The Cavaloss Lake presented a similar pattern in relation to variation of those attributes of the community, but with values twice higher than the other starting from the end of the rising; and that you/they stayed high even falling of 2005. As the diversity in that adapts, the values were larger of the end of the rising to the end of the high water and smaller in the falling periods. In the intensive study (samplings twice in the week), a phase that could be detected as of equilibrium it was just detected at the Cavaloss Lake through the presence of Aphanocapsa spp. during approximately five weeks, since then, the biomass of that species was reduced and Cryptomonas brasiliensis prevailed with more than 40% for two collections, characterized by the sudden increase in the hidrometric level, that destabilized the community, favoring that species opportunist\'s development, being substituted by a pick of elevation of the biomass of Botryococcus braunii, following by increase of the diversity. Like this, it seems that the clímax of the ecosystem was altered and the succession reverted to initial process, seen by the development of pioneering species (Rstrategist), following by increase of the diversity. In the other lakes, Cryptomonas brasiliensis also presented growth picks along the study, being related to precipitation events and/or wind. Without the antropic interference, characterized by the handling of the dam of Jurumirim, probably, the phytoplankton community would have more time to solemnity-organize during the limnofase unchaining a true succession in the Lakes Camargo and Coqueiral. The hidrologic pulse then, would work as an intermediate disturbance elevating the diversities. Seemingly, in the current conditions, the flood has just been causing a disturbance of low frequency, without resulting in maximum diversity, due to constant entrance of water in the connected ponds along the seasonal cycle. However, in the Cavaloss Lake, isolated, the substantial increase of the volume of water in the end of January of 2005 a disturbance of intermediate intensity can be considered, seen the high diversity values and wealth found after the inundation, that you/they were the highest of this lakes during the study period. (AU)