Abstract. We reconstruct the aquatic ecosystem interactions since the last interglacial
period in the oldest, most diverse, hydrologically connected European lake
system, by using palaeolimnological diatom and selected geochemistry data
from Lake Ohrid “DEEP site” core and equivalent data from Lake Prespa core,
Co1215. Driven by climate forcing, the lakes experienced two adaptive cycles
during the last 92 ka: "interglacial and interstadial" and
"glacial" cycle. The short-term ecosystems reorganizations, e.g. regime
shifts within these cycles substantially differ between the lakes, as evident
from the inferred amplitudes of variation. The deeper Lake Ohrid shifted
between ultra oligo- and oligotrophic regimes in contrast to the much
shallower Lake Prespa, which shifted from a deeper, (oligo-) mesotrophic to a
shallower, eutrophic lake and vice versa. Due to the high level of ecosystem
stability (e.g. trophic state, lake level), Lake Ohrid appears relatively
resistant to external forcing, such as climate and environmental change.
Recovering in a relatively short time from major climate change, Lake Prespa is
a resilient ecosystem. At the DEEP site, the decoupling between the lakes'
response to climate change is marked in the prolonged and gradual changes
during the MIS 5/4 and 2/1 transitions. These response differences and the
lakes' different physical and chemical properties may limit the influence of
Lake Prespa on Lake Ohrid. Regime shifts of Lake Ohrid due to potential
hydrological change in Lake Prespa are not evident in the data presented
here. Moreover, a complete collapse of the ecosystems functionality and loss
of their diatom communities did not happen in either lake for the period
presented in the study.
Ecosystem regimes and responses in a coupled ancient lake system from MIS 5b to present: the diatom record of lakes Ohrid and Prespa
