Invasive mollusc faunas of the River Thames exemplify biostratigraphical characterization of the Anthropocene

Abstract

Profound changes to the species configuration of ecosystems globally during the 19th to 21st centuries, resulting from the introduction of neobiota, have produced a distinctive palaeontological signature in sedimentary deposits, here exemplified by those of the River Thames. Coring near Teddington Lock (ca. 4.3 m above sea level, ca. 89 km upstream from the mouth of the Thames estuary) yielded dense assemblages of shells of the invasive Asian clam Corbicula fluminea (recently invaded in 2004) and the zebra mussel Dreissena polymorpha (invaded 1824), which together accounted for 96% of individuals sampled. Population densities of C. fluminea of over 6000 individuals per m2 were maintained for a depth of 1 m indicating that the Asian clam is an important biostratigraphical marker in the Thames for sedimentary deposits accumulating since 2004. The first modern European occurrence of C. fluminea was in Portugal in 1980. In 1987, the first occurrence of C. fluminea on the northern coast of South America was observed in the Caripe River, Venezuela. The non‐native range of D. polymorpha was restricted to continental Europe for over 200 years until it appeared in the Great Lakes, USA, in 1986 having been transported in ballast water. Within three years, it reached populations of over 750,000 individuals per m2 and it is presently recorded in 35 states. Therefore, the pan‐Atlantic range expansion of D. polymorpha, coupled with the recent invasion history of C. fluminea in Venezuela and Portugal, identifies a biostratigraphical interval in sedimentary deposits forming from the early 1980s that can be correlated between Europe and the Americas.

Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch

“…Novel energy sources included whale oil 43 and stream energy; for example, there were >65,000 water-powered mills in the U.S.A. prior to 1840 CE 44,45 . Human-enabled species introductions expanded, and transfers happened rapidly, exemplified by the spread of accidentally introduced aquatic mollusks in Europe 46 . This informal interval represents the fundamental transformation from pre-industrial to full industrial energy use.…”

“…The annual rate of species invasions has greatly increased since the late-20 th century 172 . Species inventories of ecosystems record rapid or substantial changes in many seas 173 , rivers 174 , estuaries 175 and terrestrial settings 176,177 , often leaving a biostratigraphical signature of change 46,178 . Many invasive species signal highly human-disturbed ecosystems 179 .…”

Planetary‐scale change to the biosphere signalled by global species translocations can be used to identify the Anthropocene

“…2011); (2) the rapid migration of the Asian clam ( Corbicula fluminea ) through European waterways from the 1980s (Himson et al . 2020) (this clam arrived in North America during the 1920s and became widespread across the United States and Mexico; López et al . 2019); (3) the zebra mussel ( Dreissena polymorpha ) and quagga mussel ( Dreissena rostriformis bugensis ) through North American lakes since 1986 and 1989 respectively (e.g.…”

“…2019), and Europe and North America (Himson et al . 2020). Also important is the response of microorganisms to human perturbations of coastal and freshwater ecosystems since the Industrial Revolution (Wilkinson et al .…”

“…2019; Himson et al . 2020) whilst C. wailesii is known to produce a fossil record in its native range of the Pacific Ocean (e.g. Koizumi & Tanimura 1985).…”