Decline in Coccolithophore Diversity and Impact on Coccolith Morphogenesis Along a Natural CO₂ Gradient

Abstract

Abstract.A natural pH gradient caused by marine CO 2 seeps off Vulcano Island (Italy) was used to assess the effects of ocean acidification on coccolithophores, which are abundant planktonic unicellular calcifiers. Such seeps are used as natural laboratories to study the effects of ocean acidification on marine ecosystems, since they cause longterm changes in seawater carbonate chemistry and pH, exposing the organisms to elevated CO 2 concentrations and therefore mimicking future scenarios. Previous work at CO 2 seeps has focused exclusively on benthic organisms. Here we show progressive depletion of 27 coccolithophore species, in terms of cell concentrations and diversity, along a calcite saturation gradient from ⍀ calcite 6.4 to Ͻ1. Water collected close to the main CO 2 seeps had the highest concentrations of malformed Emiliania huxleyi. These observations add to a growing body of evidence that ocean acidification may benefit some algae but will likely cause marine biodiversity loss, especially by impacting calcifying species, which are affected as carbonate saturation falls.

Nannoplankton malformation during the Paleocene-Eocene Thermal Maximum and its paleoecological and paleoceanographic significance

“…The extended sequence of morphotypes in the plexus, in particular, allows us to draw parallels. The separation, twisting, and loss of rays observed in the D. salisburgensis plexus are similar to the separation, twisting, and loss of elements in E. huxleyi [see Ziveri et al ., , Figure 4]. However, overall irregularity in the plexus is more extreme than in E. huxleyi .…”

“…In E. huxleyi , malformation is expressed largely in the radial, T‐shaped elements on the shield rim. In malformed specimens, the elements can become twisted, incompletely calcified, fused together, or even missing [e.g., Young and Westbroek , ; De Bodt et al ., ; Ziveri et al ., ]. The extended sequence of morphotypes in the plexus, in particular, allows us to draw parallels.…”

“…Understanding the significance of malformation among modern coccolithophores requires a combination of morphologic and genetic information [e.g., Ziveri et al ., ]. For fossil coccolithophores we must rely on the form of coccoliths and thus it is impossible to truly distinguish between the possibility that highly irregular shape represents malformed variants of an individual species (i.e., possibly phenotypic plasticity) or new species (i.e., without malformation).…”

A unique temperate rocky coastal hydrothermal vent system (Whakaari–White Island, Bay of Plenty, New Zealand): constraints for ocean acidification studies

“…The most well-studied shallow submarine CO 2 vents in the context of climate change are in the warm temperate Mediterranean Sea (e.g. Hall-Spencer et al 2008;Kroeker et al 2011;Lidbury et al 2012;Vizzini et al 2013;Baggini et al 2014;Ziveri et al 2014;Cornwall et al 2017a;Hawkins et al 2018), in deep water (e.g. Rossi and Tunnicliffe 2017) or in tropical to subtropical coral reef environments in Papua New Guinea (e.g.…”

Response of Sea Urchin Fitness Traits to Environmental Gradients Across the Southern California Oxygen Minimum Zone

“…There is compelling evidence that projected future changes in ocean temperature, carbonate chemistry, and DO will affect morphological function of calcified hard parts and fitness success. For example, weaker structures in intertidal mussels (Gaylord et al, 2011;Carrington et al, 2015), crustaceans (Taylor et al, 2015;deVries et al, 2016;Lowder et al, 2017), coccolithophorids (Ziveri et al, 2014), and sea urchins (Presser et al, 2010;Collard et al, 2016) could increase vulnerability to predation. Sea urchins produce ellipsoid-shaped, calcitic skeletal structures called tests, as well as calcitic spines, both of which provide the organism with a variety of critical functions such as protection against predators, sensing, locomotion, and feeding (Pearse, 2006).…”