Free-floating islands, mysteriously moving around on lakes, were described by several Latin authors almost two millennia ago. Seneca (4 BC-AD 65) in his Naturales quaestiones, and by Pliny the Elder (AD 23-79) in his Naturalis historia (“Of Islands Ever Floating and Swimming”), for example, have left us suggestive descriptions of floating islands, reporting details about their size and shape, buoyancy and vegetation. These fascinating ecosystems have been often investigated from ecological, hydrological and management points of view, but there have been almost no studies of their rates of accumulation of organic matter, as well as on their possible role as a natural archive of climate and vegetation changes, as well as of the historical human activity. A 4-m long peat core was collected from the center of the free-floating island of Posta Fibreno, a relic mire in Central Italy. This is the thickest accumulation of peat ever found in a free-floating mire, yet it has formed during the past 700 yr (Zaccone et al., 2017). This free-floating mire shows anomalously high accretion rates (0.5–0.6 cm/yr), that are 10× greater than other terrestrial peatlands (0.02–0.08 cm/yr) (Zaccone et al., 2017), and preserves some peculiar microbial taxa (Zaccone et al., 2018) which show an unusual concurrent species convergence between this sub-Mediterranean site and far Nordic or circumpolar environments (Concheri et al., 2017). Thus, this free-floating island has the potential to be also used as archive of natural and human-induced environmental changes occurring during the last centuries. In this work, the first high resolution records of organic matter accumulation, trace element and dust depositions, and environmental changes from a free-floating island will be presented, and the reliability of this peat archive for geochemical and environmental studies suggested and demonstrated.
The secret and fascinating world of the free-floating peat island of Posta Fibreno
Zaccone C.
;
2026-01-01
Abstract
Free-floating islands, mysteriously moving around on lakes, were described by several Latin authors almost two millennia ago. Seneca (4 BC-AD 65) in his Naturales quaestiones, and by Pliny the Elder (AD 23-79) in his Naturalis historia (“Of Islands Ever Floating and Swimming”), for example, have left us suggestive descriptions of floating islands, reporting details about their size and shape, buoyancy and vegetation. These fascinating ecosystems have been often investigated from ecological, hydrological and management points of view, but there have been almost no studies of their rates of accumulation of organic matter, as well as on their possible role as a natural archive of climate and vegetation changes, as well as of the historical human activity. A 4-m long peat core was collected from the center of the free-floating island of Posta Fibreno, a relic mire in Central Italy. This is the thickest accumulation of peat ever found in a free-floating mire, yet it has formed during the past 700 yr (Zaccone et al., 2017). This free-floating mire shows anomalously high accretion rates (0.5–0.6 cm/yr), that are 10× greater than other terrestrial peatlands (0.02–0.08 cm/yr) (Zaccone et al., 2017), and preserves some peculiar microbial taxa (Zaccone et al., 2018) which show an unusual concurrent species convergence between this sub-Mediterranean site and far Nordic or circumpolar environments (Concheri et al., 2017). Thus, this free-floating island has the potential to be also used as archive of natural and human-induced environmental changes occurring during the last centuries. In this work, the first high resolution records of organic matter accumulation, trace element and dust depositions, and environmental changes from a free-floating island will be presented, and the reliability of this peat archive for geochemical and environmental studies suggested and demonstrated.
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