Contrasting calcification responses to ocean acidification between two reef foraminifers harboring different algal symbionts

Abstract

Ocean acidification, which like global warming is an outcome of anthropogenic CO2 emissions, severely impacts marine calcifying organisms, especially those living in coral reef ecosystems. However, knowledge about the responses of reef calcifiers to ocean acidification is quite limited, although coral responses are known to be generally negative. In a culture experiment with two algal symbiont‐bearing, reef‐dwelling foraminifers, Amphisorus kudakajimensis and Calcarina gaudichaudii, in seawater under five different pCO2 conditions, 245, 375, 588, 763 and 907 μatm, maintained with a precise pCO2‐controlling technique, net calcification of A. kudakajimensis was reduced under higher pCO2, whereas calcification of C. gaudichaudii generally increased with increased pCO2. In another culture experiment conducted in seawater in which bicarbonate ion concentrations were varied under a constant carbonate ion concentration, calcification was not significantly different between treatments in Amphisorus hemprichii, a species closely related to A. kudakajimensis, or in C. gaudichaudii. From these results, we concluded that carbonate ion and CO2 were the carbonate species that most affected growth of Amphisorus and Calcarina, respectively. The opposite responses of these two foraminifer genera probably reflect different sensitivities to these carbonate species, which may be due to their different symbiotic algae.

Combined effects of warming and ocean acidification on coral reef Foraminifera Marginopora vertebralis and Heterostegina depressa

“…One species with a porcelaneous shell decreased in size with increasing pCO 2 . Species-specific responses have been confirmed in a study by Hikami et al (2011). Studies of Foraminifera from natural CO 2 seeps with locally decreased pH reported increasing incidences of altered shell structure, decreasing population densities, declining diversity in calcifying Foraminifera, and increasing proportion of Foraminifera with agglutinated shells towards low pH/high pCO 2 (Dias et al 2010;Fabricius et al 2011;Uthicke and Fabricius 2012;Uthicke et al 2013).…”

“…A small but not significant increase in growth was observed in M. vertebralis in the treatment exposed to elevated pCO 2 (738 latm) at 28°C. A slight growth enhancement was observed in other porcelaneous species (Vogel and Uthicke 2012), whereas other studies reported reduced growth at medium to high pCO 2 levels (700-1,100 latm) in Amphisorus hemprichii Hikami et al 2011) and M. rossii (Reymond et al 2013).…”

Ocean acidification induces biochemical and morphological changes in the calcification process of large benthic foraminifera

“…Similar results were also found by Vogel & Uthicke [23], who also observed either no effect or enhanced growth in M. vertebralis after 45 days exposure to as high as 1925 ppm CO 2 . Conversely, a decline in shell weight of newly asexually produced specimens of Amphisorus hemiprichii was detected by Hikami et al [52] after four weeks exposed to low pH/ high pCO 2 conditions. Both species live on and are adapted to the shallow areas of the reef [34].…”

Shell Dissolution in Larger Benthic Foraminifers Exposed to Ph and Temperature Extremes: Results From an in Situ Experiment

“…and tropical reef-associated taxa, including amphisteginids, calcarinids, and nummulitids, that host algal endosymbionts (e.g., Lee, 2006). Responses to elevated pCO 2 among the rotaliids have varied from reduced calcification, especially in taxa that lack algal symbionts (e.g., Allison et al, 2010;Dissard et al, 2010;Haynert et al, 2011), to enhancement of growth and photosynthesis in those with algal symbionts, at least at intermediate pCO 2 levels (e.g., Fujita et al, 2011;Hikami et al, 2011). Among the porcelaneous Miliolida, most experiments have utilized members of the Family Soritidae that host dinoflagellate symbionts.…”