Ecological regime shift preserved in the Anthropocene stratigraphic record

Abstract

Palaeoecological data are unique historical archives that extend back far beyond the last several decades of ecological observations. However, the fossil record of continental shelves has been perceived as too coarse (with centennial-millennial resolution) and incomplete to detect processes occurring at yearly or decadal scales relevant to ecology and conservation. Here, we show that the youngest (Anthropocene) fossil record on the northern Adriatic continental shelf provides decadal-scale resolution that accurately documents an abrupt ecological change affecting benthic communities during the twentieth century. The magnitude and the duration of the twentieth century shift in body size of the bivalve Corbula gibba is unprecedented given that regional populations of this species were dominated by small-size classes throughout the Holocene. The shift coincided with compositional changes in benthic assemblages, driven by an increase from approximately 25% to approximately 70% in median per-assemblage abundance of C. gibba . This regime shift increase occurred preferentially at sites that experienced at least one hypoxic event per decade in the twentieth century. Larger size and higher abundance of C. gibba probably reflect ecological release as it coincides with an increase in the frequency of seasonal hypoxia that triggered mass mortality of competitors and predators. Higher frequency of hypoxic events is coupled with a decline in the depth of intense sediment mixing by burrowing benthic organisms from several decimetres to less than 20 cm, significantly improving the stratigraphic resolution of the Anthropocene fossil record and making it possible to detect sub-centennial ecological changes on continental shelves.

Parasitism and host behavior in the context of a changing environment: The Holocene record of the commercially important bivalve Chamelea gallina, northern Italy

“…This rapid warming, and related sea level rise along with other anthropogenic impacts, are predicted to be major driving forces in shaping ecological interactions and morphology of coastal areas. In particular, there is a fast-growing body of ecological literature forecasting multiple and complex effects of global change on ecological interactions, especially in coastal environments ([ 2 – 7 ] among many). Among the many concerns deriving from global change’s impacts on wildlife and society, parasites are poorly profiled.…”

Pyrite-lined shells as indicators of limited oxygen exposure time and inefficient bioirrigation in the Holocene-Anthropocene stratigraphic record

“…Any effects on early diagenetic pathways determined by changes in grain size can be excluded because sediment 545 grain size remains constant downcore at Po and Panzano. Although paleoecological records of foraminifers and dinoflagellates indicate that eutrophication affects the northern Adriatic Sea ecosystems since the 19 th century (Barmawidjaja et al 1995;Sangiorgi and Donders 2004), a main shift in the composition of macrobenthic communities and size of the bivalve V. gibba occurs at the same stratigraphic levels where pyrite linings increase in frequency, i.e., at 80-90 cm at Po and at 12-20 cm Panzano stations (Tomašových et al, , 2020. These levels correspond to the mid-20 th century at both 550 https://doi.org/10.5194/bg-2021-153 Preprint.…”

Climate variation during the Holocene influenced the skeletal properties of Chamelea gallina shells in the North Adriatic Sea (Italy)

“…A complementary approach is to investigate the recent fossil record. This line of research gives access to an archive of ecological responses to past climate transitions that could elucidate near-future scenarios of marine ecosystems under global warming [ 9 , 10 ].…”