Water and Marsh Plants in the Artificial Brokopondo Lake (Surinam, S. America) During the First Three Years of Its Existence

Abstract

The Brokopondo Lake in the interior of Surinam began to form when on 1 February 1964 the dam in the Surinam River near Afobaka was closed. The lake was intended to cover an area of about 150.000 ha and to have a maximal depth of about 47 m.The basin, largely occupied by forest, was not cleared beforehand. During the initial stage the water in the flooded forest was characterised by a very high content of organic matter and the absence of oxygen. As the water level rose, differentiation between a hypolimnion and an epilimnion developed. The oxygen content of the epilimnion was high.During the first three years of its existence the lake attained an area of about 84.000 ha and a maximal depth of 38 m.Within this period eight aquatic plant species became numerous in the lake. Special attention was paid to Eichhornia crassipes and Ceratopteris pteridoides. In April 1966, when the lake covered about 78.000 ha, the former had colonized 53 %, the latter 21 % of this area.Since September 1966 both diminished greatly, Eichhornia as a result of artificial control, Ceratopteris for unknown reasons.Floating pieces of decaying wood became overgrown by a variety of plant species, 27 of which were recorded.Mixed vegetations of water and marsh plants developed, free-floating mats (Eichhornia being the matrix), patches attached to partly submerged tree tops, and belts along the shore. Twentytwo species were observed as constituents of these floating vegetations.

The fish fauna of Brokopondo Reservoir, Suriname, during 40 years of impoundment

“…Deep water (hypolimnion) remained anoxic with relatively low temperature, high electrolytes (conductivity) and gases H 2 S and CH 4 . The mineralization of organic matter of the inundated forest resulted in abundant growth of floating macrophytes, ultimately covering 582 km 2 (or 75% of the lake area) in 1966 (Donselaar, 1968). Aerial spraying with herbicide had eradicated most floating aquatic macrophytes by 1970, but decomposition of these water plants resulted in low dissolved oxygen levels in the hypolimnion in -1976 (Panday-Verheuvel, 1983).…”

“…Amazonian reservoirs pose particular problems related to intensive decomposition of inundated tropical rainforest vegetation (Tundisi et al, 1993). Severe deterioration of water quality in the reservoir and downstream of the dam resulting in local (reservoir) to extensive (downstream) fish kills, explosive increase of free floating macrophytes, large-scale production of 'greenhouse' gases, and vertical stratification with an anoxic hypolimnion were first described for Brokopondo Reservoir (Donselaar, 1968;Heide, 1982; Panday-Verheuvel, 1983).…”

“…Amazonian reservoirs pose particular problems related to intensive decomposition of inundated tropical rainforest vegetation (Tundisi et al, 1993). Severe deterioration of water quality in the reservoir and downstream of the dam resulting in local (reservoir) to extensive (downstream) fish kills, explosive increase of free floating macrophytes, large-scale production of 'greenhouse' gases, and vertical stratification with an anoxic hypolimnion were first described for Brokopondo Reservoir (Donselaar, 1968;Heide, 1982; Panday-Verheuvel, 1983).The Brokopondo Dam clearly had negative effects on the diverse Suriname River fish fauna (Boeseman, 1964;Mees, 1967;Nijssen, , 1969 Agostinho et al (1999) anticipated the following long term effects of reservoir aging on the fish fauna: a reduction in number of top-predators, mean size of species (and even within a species) and species richness, dominance of pelagic species and short-lived species with fast growth, and, in advanced stages of aging, dominance of species adapted to shallow water with low oxygen (first noticeable in littoral areas). Our objectives are to describe the pre-impoundment Suriname River fish fauna in the area of the future Brokopondo Reservoir (based on the 1963-1964 collection of Boeseman) and the fish fauna of Brokopondo Reservoir in 1967Reservoir in , 1978Reservoir in and 2002Reservoir in -2005 in order to document impacts of the dam on the Suriname River fish fauna and long term changes in reservoir communities as hypothesized by Agostinho et al (1999).…”

Notes on the Fishery Potential and Fish Fauna of the Brokopondo Reservoir (Surinam)

“…(2) An off-shore area (depths from 3 to about 10 m) with dead tree trunks emerging from the water, their tree tops sometimes still present. Areas (I and 2) occupy about 70% of the total reservoir (Van Donselaar, 1968).…”

Impactos ecológicos das represas hidrelétricas na bacia amazônica brasileira<A NAME="top1"></A>

“…de animais herbívoros, pragas e doenças.Algumas das espécies mais daninhas em represas africanas e asiáticas são endêmicas na América do Sul tropical, por exemplo Eichhornia crassipes e Salvinia auriculata (Salvinia molesta, da represa Kariba, foi descrita mais tarde como espécie nova com reprodução exclusivamente vegetativa). Suriname, em condições hidroquímicas similares às da Amazônia, houve um crescimento maciço de Eichhornia crassipes e Ceratopteris pteridoides logo depois do represamento(DONSELAAR, 1968). Eichhornia, foi eliminada com herbicidas (2,4,D).…”