Ocean Acidification Model Predicts a 65% Reduction in Large Benthic Foraminiferal Carbonate Sediment Production on the West Florida Shelf By 2140

Abstract:

A meta-analysis of data from our laboratory combined with previously published studies on the effects of ocean acidification on rotalid and miliolid large benthic Foraminifera (LBF) was conducted. This meta-analysis, which included 11 LBF species, found divergent growth rates between the two orders. At [CO_2(air))] < 600 ppm, rotalids increased their diameters by 0.6 ± 0.3(SE)%/d and miliolids increased their diameters by 1.0 ± 0.5%/d. At [CO_2(air))] between 600 – 1,050 ppm, rotalids and miliolid diameters increased by 0.6 ± 0.5%/d and 0.9 ± 0.7%/d, respectively. At [CO_2(air))] > 1,050 ppm rotalids and miliolid increased their diameters by 0.3 ± 0.4%/d and 0.5±0.4%/d, respectively. Using these growth rate values, we estimated LBF carbonate sediment production on the west Florida shelf, an area covering 54,000 km² to a depth of 30 m, at 3.4 Mt/yr. Additionally, a model incorporating foraminiferal growth rates, seawater chemistry, and WFS habitat distributions projects a 1.5 Mt/yr to 1.1 Mt/yr (25%) decrease of rotalid-derived annual carbonate sediment production by the year 2100 ([CO_2(air))] ~ 800 ppm), and a 1.5 Mt/yr to 0.7 Mt/yr (55%) decrease by the year 2140 ([CO_2(air))] ~ 1,300 ppm). Using this same model, miliolid-derived annual carbonate sediment production is projected to decrease from 1.8 Mt/yr to 1.2 Mt/yr (35%) by 2100 ([CO_2(air))] ~ 800 ppm), and from 1.8 Mt/yr to 0.5 Mt/yr (70%) by 2140 ([CO_2(air))] ~ 1,300 ppm). These reductions correspond to a net 30% annual reduction of LBF-derived carbonate sediments by 2100 ([CO_2(air))] ~ 800 ppm) and 65% by 2140 ([CO_2(air))] ~ 1,300 ppm). The differential effects of ocean acidification on the reduction of LBF growth rates and the accompanying transition of LBF-derived carbonate sediment production from predominantly variable-Mg miliolids to low-Mg rotalids will likely have local ecologic implications.