Research Article: Responses of molluscan communities to centuries of human impact in the northern Adriatic Sea

Date Published: July 19, 2017

Publisher: Public Library of Science

Author(s): Ivo Gallmetzer, Alexandra Haselmair, Adam Tomašových, Michael Stachowitsch, Martin Zuschin, Geerat J. Vermeij.


In sediment cores spanning ~500 years of history in the Gulf of Trieste, down-core changes in molluscan community structure are characterized by marked shifts in species and functional composition. Between the 16th and 19th century, a strong heavy metal contamination of the sediments, most notably by Hg, together with the effects of natural climatic oscillations (increased sedimentation and organic enrichment) drive community changes. Since the early 20th century up to 2013, the combined impacts of cultural eutrophication, frequent hypoxic events and intensifying bottom trawling replace heavy metal contamination and climatic factors as the main drivers. The pollution-tolerant and opportunistic bivalve Corbula gibba and the scavenging gastropod Nassarius pygmaeus significantly increase in abundance during the 20th century, while species more sensitive to disturbances and hypoxia such as Turritella communis and Kurtiella bidentata become rare or absent. An infaunal life habit and scavenging emerge as the dominant life strategies during the late 20th century. Down-core shifts in the proportional abundances of molluscan species and functional groups represent a sensitive proxy for past ecological changes and reveal a century-long anthropogenic impact as the main driver behind these processes in the northern Adriatic Sea, offering also a unique perspective for other shallow marine ecosystems worldwide.

Partial Text

Most marine ecosystems worldwide are affected by human activities, and pristine coastal areas have virtually disappeared [1–3]. The human influence ranges from direct exploitation of multiple resources to pollution, from coastal urbanisation to eutrophication, and involves large-scale and complex phenomena such as marine invasions, ocean acidification and global warming. Modern ecological studies often fail to capture long-term ecosystem responses to anthropogenic stressors because they are restricted to a time scale of a few years or a few decades and thus do not recover conditions pre-dating anthropogenic disturbance. An approach integrating palaeontological, sedimentological and geochronological methods applied to sediment cores [4, 5] and including the study of historical accounts relevant to the topic can solve this problem and discriminate between natural and anthropogenic drivers of changes in benthic ecosystems [6].

The molluscan community in the sediment cores from Panzano Bay experienced several shifts over the past ~500 years.