Variação espacial e temporal da produtividade primária pelo fitoplâncton na represa de Jurumirim (Rio Paranapanema, SP)

Abstract

Spatial and temporal variations on the primary productivity by the phytoplankton in Jurumirim Reservoir (Paranapanema River, São Paulo, Brazil)A study on the spatial and temporal variations of the primary productivity by phytoplankton was conducted in Jurumirim Reservoir (Paranapanema River, São Paulo, Brazil) from October, 1995 to July, 1996. Six sampling stations were selected, three in Paranapanema Arm, two in Taquari Arm and one in das Posses Arm. The C 14 method was used for measuring the primary production and a study on the correlated physical and chemical variables was made.In November, 1995 and in January-February, 1996 the T 2 station (transition region of Taquari Arm) presented the highest value of primary production (23.9 and 20.1 mgC.m , respectively) and in the other two studied periods (April and July, 1996), it was the second most productive station (6.0 and 10.2 mgC. .h -1 ), when compared with the other five stations. In Taquari Arm, an increase on the primary production occurred from the T 1 (riverine zone) to T 2 stations (transition region), in all the four studied periods. In Paranapanema Arm, an increase on the primary production was also observed from the P 1 (riverine zone) to P 2 (transition zone) and to P 3 stations (main water body zone) in October-November, 1995 and July, 1996. In January-February 1996, the increase in the three successive stations was low, while in April, 1996 no significant variation was observed on the primary production. A variance analysis showed that there were significant modifications in the suspended matter amounts, in the water conductivity and in the inorganic phosphate and nitrate concentrations in the different periods of the year.The seasonal variations can be attributed to the water precipitation, to the allochthonous loads of suspended solids, nitrogen and phosphorus introduced by the two tributaries, and to internal recycling of nutrients. The statistical analysis also showed significant differences between sampling stations on the primary productivity by phytoplankton, on the euphotic zones, on the water conductivity and on the silicate concentrations. The spatial differences of the primary productivity are due to the modifications on the amplitudes of the euphotic zones. The euphotic layer presents longitudinal variations, that can be attributed, besides the solar radiation intensities, to the different allochthonous material loads, the tripton sedimentation and the sediment ressuspension caused by the water circulation. The spatial differences in the silicate concentrations and in the water conductivity are due to the geological influences of the watershed of each tributary (Paranapanema, Taquari and das Posses Rivers). The ions and silicate inputs by the three rivers present a different dilution when introduced in each compartment of the reservoir.

Phytoplankton assemblages in a reservoir cascade of a large tropical - subtropical river (SE, Brazil)

“…Canoas I and Canoas II, the newest reservoirs in the Paranapanema cascade, were the ones with lower phytoplankton diversity. The Jurumirim spatial complexity effect on the phytoplankton productivity and structure has been already well demonstrated (Henry et al, 1998;Nogueira, 2000). Another particularity that influences richness and diversity is the connectivity with lateral wetlands, mainly with seasonal or permanent lakes containing a huge amount of different microhabitats (macrophyte-dominated).…”

“…Before the zone of the influence of the first dam (Upstream of Jurumirim), where fluvial conditions and high productivity predominate (Henry et al, 1998;Nogueira, 2000), all the main algae groups were well represented. In the stratified lacustrine environments of Jurumirim and Chavantes Reservoirs, the assemblages were dominated by small unicellular diatoms, mainly D. stelligera.…”

“…reservoirs of the Paraná-La Plata basin are highly affected by the usually complex spatial structure and conspicuous seasonal changes (mainly dry-wet periods) (Henry et al, 1998;Nogueira, 2000;De León and Chalar, 2003;MatsumuraTundisi and Tundisi, 2005;Soares et al, 2008). The present study analyses the phytoplankton variability (inter and intra-reservoir) along a cascade of eight reservoirs constructed for hydroelectric production in the Paranapanema River (São Paulo State).…”

“…Previous studies on phytoplankton assemblages of the Paranapanema basin (taxonomy, organizational structure and productivity) were carried out by Henry (1990Henry ( , 1993, Henry et al (1998), Nogueira (2000), Bittencourt-Oliveira (2002), Ferrareze and Nogueira (2006), Henry et al (2006a, b) and Bicudo et al (2006).…”

Parasite infracommunities of Leporinus friderici: A comparison of three tributaries of the Jurumirim Reservoir in southeastern Brazil

“…trematodes) can be the result of changing overall abiotic factors and, particularly, changes to the intermediate host community that lead to parasite homogenization. Previous studies have identified a significant reduction in potential intermediate host communities (zooplankton and benthic communities), and thereafter a proportional decrease in fish density and diversity in the Jurumirim Reservoir (Henry et al 1998, Mitsuka andHenry 2002). All these are key factors which maintain parasite dynamics.…”