Unprecedentedly fast, human-derived fossil-fuel burning has elevated atmospheric CO₂ with largely unknown impacts to surface ocean organisms. While warming and acidification have produced some observable changes globally and regionally in a physical and chemical sense, associated changes to planktonic calcifying organisms at the base of marine food webs and ecosystems remains very poorly understood. In particular, coccolithophores (phytoplankton), foraminifera and pteropods (zooplankton) that form CaCO₃ shells have been demonstrated as particularly, puzzlingly, and potentially sensitive recorders of such combined influences. Furthermore, the Mediterranean Sea has been recognized as a global climate change “hotspot” whereby regional impacts are expected to be especially profound throughout the 21st century. Much knowledge is missing however on the nature of pre- versus post-anthropogenic change throughout the W. Mediterranean in particular, and the CALMED projects aims to fill these important and glaring gaps with new studies on these 3 major classes of marine calcifying plankton. We will explicitly test the hypothesis that human-induced climate change since the mid-19th century has already borne detectable changes on these plankton groups that are observable through their assemblage compositions, mass and morphometry, and seasonal cycling of both former aspects plus geochemical tracers.

CALMED exploits a “top-down” approach in the broader Mediterranean basin, including the NE Atlantic as a form of “background”, by examining water samples, sediment traps, surface sediments, and down-core sediments dating back several centuries into the last millennium. This combination should enable a temporally- and spatially-scaled assessment of the major planktonic calcifying groups under the influence of diverse Mediterranean physical oceanographic and associated geochemical influences and features, plus a greater understanding of marine biodiversity changes of the same organisms through a critical time period.

The findings should ultimately contribute critical knowledge on a number of outstanding issues in the Mediterranean Sea, which is widely-recognized as especially sensitive to a range of global-scale influences but yet at the marginal sea (or basin) scale.