LONG-TERM RESILIENCE OF MOLLUSK COMMUNITIES TO NATURAL CLIMATE CHANGES: A CASE EXAMPLE FROM THE ADRIATIC SEA

Ecological systems vary in their responses to long-term climate changes that occur naturally on our planet. Preliminary analyses of the late Quaternary mollusk communities of the Adriatic Sea tentatively suggest that benthic ecosystems of the Po Delta displayed a remarkably resilient response to major long-term environmental changes associated with glacial cycles. The Po Delta was located in an approximately present-day location during the previous interglacial (isotope stage 5.5, ~125ka). During the subsequent glacial phase, the regional sea-level dropped by ~120 meters and the Po Delta migrated ~200km southeastward and resided close to the Mid-Adriatic Deep. The Po Delta returned back to its current location with the onset of the current interglacial phase. We compared core samples from the proximal Po Delta (the previous and current interglacial time intervals) with the distal core samples from the Mid-Adriatic Deep (the last glacial interval). The multivariate ordination (NMDS) and regional diversity analyses suggests that mollusk associations are indistinguishable between the two interglacial deltas. In contrast, the glacial Po Delta located distally represented distinct faunal associations and was dominated regionally by a different suite of species. These preliminary results tentatively suggest that Po Delta ecosystems have responded resiliently to major climate perturbations. When Po Delta migrated offshore during the glacial lowstand the delta communities changed significantly in composition and regional diversity patterns. However, when Po Delta returned to its previous location, the mollusk communities reverted back to their previous state. Whereas this progress report is based on a still limited number of glacial core samples, the reported results suggest that marine benthic communities may be highly resilient to natural, long-term environmental changes that are driven by global climatic processes. This outcome underscores the unique threat of ongoing anthropogenic changes that are altering many marine communities, including contemporary ecosystems of the Po Delta.