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Abstract TD56
Plisnier P.-D., 1996, Limnological sampling during a second annual cycle (1994-1995) and some comparisons with year one on Lake Tanganyika. GCP/RAF/271/FIN-TD/56 (En): 60p.


Most of the events noted during the limnological cycle described in 1993-94 (Plisnier et al., 1996) were confirmed in 1994-95 with the tilting of the epilimnion by the south-east (SE) winds during the dry season and upwelling from return deep currents in the south during the dry season. Stratification index differences between the north and south were generally similar in both years. Upwelling of deep water in June to September could be observed near Mpulungu when values of the stratification index (SI) were < 1. Higher concentrations of phosphorus (TP and TDP) in surface waters of Mpulungu were noted during the upwelling.
Oscillations of the water masses were deduced from the behaviour of several parameter concentrations at the end of the dry season. Chimbanfula waves were observed near the shores of Mpulungu in October 1994. Presence of internal waves throughout the whole year, at all LTR stations, were inferred from measured parameter fluctuations. Pulses of turbidity were observed and supported the suggestion that nutrient rich water displacementby internal waves were tied to pulses of phytoplankton and bacterial production.
The amplitude of hydrodynamics has however apparently decreased in 1994-95 compared to the previous year. There was a decrease in the tilting of the thermocline this year probably because of weaker winds. Secondary upwelling in the north of the lake was not deduced from available data in 1994-95.
The oscillations of parameters were found to be either similar or sometimes higher in the coastal area compared to the pelagic area. There was no clear difference in nutrient concentration in the coastal area between the dry and wet season.