Temporal Dynamics Of Phytoplankton Biomass And Primary Production In Relation To Some Physico-chemical Variables In Lake Hora-arsedi Ethiopia.

Diatoms and green algae became more important during periods ofrnPrecipitation (August-September, 2005 and March-April, 2006). ThernPhytoplankton biomass varied from 19.1 to 47.6 (mean =33.42) and fromrn21.5 to 53.15 (mean = 37.47) mg m-3 at the central and near-shore stationsrnrespectively. The vertical distribution of photosynthetic activity was of arntypical pattern for phytoplankton with light-inhibition at the surface on allrnsampling dates. Light-saturated rate of photosynthesis (Amax) ranged from _rn473 to 1230 mg O2 (_ 147.6 to 383.8 mg C) m-3 h-1) at the central station.rnLack of correspondence between phytoplankton biomass and Amax wasrnapparent. Biomass-specific rate of photosynthetic production at lightsaturation,rnphotosynthetic capacity (Pmax) ranged from 13.6 to 52.8 mg O2 (mg Chl a)-1 h-1 at the central station. An inverse relationship betweenrnphotosynthetic capacity (Pmax) and phytoplankton biomass (B) was alsornobserved. The hourly integral photosynthetic rate (_A) ranged 0.41 to 2.0 grnO2 (_ 0.128 to 0.62 g C) m-2 h-1 and the R2 value shows that biomassrnexplains 0.4% of the variance in _A. The daily integral photosynthetic ratesrn((__A ) estimated ranged from 3.0 to 18.0 g O2 (_ 0.94 to 5.62 g C ) m-2 d-rn1.The temporal variations in the taxonomic composition, biomass andrnprimary production of phytoplankton are discussed in relation to somernphysico-chemical and biological variables.

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