Timescales of volcanic impacts on terrestrial and aquatic ecosystems in the Eastern Mediterranean

Instrumental data show that while the impact of volcanic eruptions on their immediate vicinity is destructive, long-term consequences can be beneficial. However, beyond last millennia observational data and ancient oral history, the detailed insights into timescales and scopes of recovery remain largely unresolved. Here we illustrate the complex response of local and regional vegetation, aquatic ecosystem, and fire activity to volcanic eruptions in close connection to prevailing climate conditions and assess the recovery time in varve-years.

We selected five volcaniclastic layers in the annually laminated sediments from Lake Van (Turkey). Analysed intervals cover glacial, interglacial, stadial and interstadial snapshots (spanning from Marine Isotope Stages 3 to 9e) and facilitate studying ecosystem’s responses under different climatic boundary conditions. Using high-resolution pollen data, non-pollen palynomorphs, and microscopic charcoal particles (>20 µm) we attempted to disentangle climatic and volcanic forcing of natural environmental disturbances. Our results highlight that the thickness of subsequent volcanic deposits and the respective climatic conditions strongly influence the impact on terrestrial and aquatic ecosystems. Similarily, the vegetation types predominant before the volcanic eruption have a decisive influence on subsequent pollen productivity and vegetation composition. On land, the most common response to ash deposition is a sudden shift towards steppe herbaceous taxa and abrupt fire activity. The affected herbaceous vegetation can recover to pre-eruption levels in as few as 20 to 40 varve-years. On the contrary, the lake water experiences intensified productivity due to subsequent nutrient input and significant short-term increase in aquatic taxa and non-siliceous microfossils.

Our approach helps in understanding complex ecosystems subjected to a variety of influencing factors operating on different time scales. Our results show the importance of distinguishing between the impact of tephra deposition and volcanically-induced climate change for tracking short-term ecosystem changes superimposed on long-term trends.