The overloading of water bodies with nutrients is a widespread ecological alteration. A recent synthesis (CNRS, IFREMER, INRA, IRSTEA) shows that lake ecosystems are particularly concerned by the eutrophication process which results in: (1) ecological disturbances (e.g. invasive species, loss of biodiversity, algal and cyanobacterial blooms), and (2) public health problems (e.g. water quality degradation due to cyanotoxin production). This makes the restoration of eutrophic freshwaters an environmental top-priority and a key-issue for scientific research. Accurate assessments of the present-day lake ecosystems state are thus needed. Moreover, long-term retrospective models of lake dynamics must be developed concomitantly to the analysis of natural and anthropogenic modifications of the catchment, which enhance the external input of sediment and nutrients. Palaeoecological researches are therefore required because they characterize through time the lake's responses to cumulative changes caused by natural (e.g. climate) and anthropogenic impacts (e.g. vegetation clearance, agriculture). They furnish thus fresh insights into a good understanding of the ecological legacies which also determine current lake structure and function, and which must be considered for sustainable lake management. A palaeoecological research was conducted in the hyper-eutrophic Lake Aydat (837 m a.s.l.), located in the Chaîne des Puys (French Massif Central). The high resolution and multi-proxy analysis (pollen, non-pollen palynomophs, diatoms, sedimentology) was combined to an approach of data mining (extraction of frequent (closed) gradual patterns of multi-variate indicators under temporal constraint) and allow to address the:

(1) reference conditions of the lake (prior to extensive human impact) and its natural variability;

(2) aquatic changes phases: timing, intensity, frequency, delay;

(3) reversibility or directions in which the lake is driven by the long-term cumulative impact (e.g. loss of resilience, ratchet effect);

(4) potential drivers: climate vs the diverse range of land uses;

(5) degree of resistance/sensitivity and vulnerability of present-day lake ecosytems.