Impacts of ocean acidification on intertidal benthic foraminiferal growth and calcification

Abstract

Foraminifera are expected to be particularly susceptible to future changes in ocean carbonate chemistry as a function of increased atmospheric CO 2 . Studies in an experimental recirculating seawater system were performed with a dominant benthic foraminiferal species collected from intertidal mudflats. We investigated the experimental impacts of ocean acidification on survival, growth/calcification, morphology and the biometric features of a calcareous species Elphidium williamsoni . Foraminifera were exposed for 6 weeks to four different pH treatments that replicated future scenarios of a high CO 2 atmosphere resulting in lower seawater pH. Results revealed that declining seawater pH caused a decline in foraminiferal survival rate and growth/calcification (mainly through test weight reduction). Scanning electron microscopy image analysis of live specimens at the end of the experimental period show changes in foraminiferal morphology with clear signs of corrosion and cracking on the test surface, septal bridges, sutures and feeding structures of specimens exposed to the lowest pH conditions. These findings suggest that the morphological changes observed in shell feeding structures may serve to alter: (1) foraminiferal feeding efficiency and their long-term ecological competitiveness, (2) the energy transferred within the benthic food web with a subsequent shift in benthic community structures and (3) carbon cycling and total CaCO 3 production, both highly significant processes in coastal waters. These experimental results open-up the possibility of modelling future impacts of ocean acidification on both calcification and dissolution in benthic foraminifera within mid-latitude intertidal environments, with potential implications for understanding the changing marine carbon cycle.

Assessing the impact of different carbonate system parameters on benthic foraminifera from controlled growth experiments

“…Responses of calcifying benthic foraminifera to pH changes are not consistent and laboratory studies show that calcification/dissolution rates under varying pH concentrations differ between and within species. Several studies observe continuing growth under low pH conditions while reporting a reduction in shell weight, size or the number of newly added chambers in several species, including Ammonia group tepida (e.g., Knorr et al, 2015;Prazeres et al, 2015;Guamán-Guevara et al, 2019;Oron et al, 2020). On the contrary, other studies do not report any low pH-related negative effects on several species of benthic foraminifera, including B.…”

“…Guamán-Guevara et al (2019) report increased mortality of Elphidium williamsoni under low pH conditions (7.3≤pH≤7.7), andCharrieau et al (2018) further document severe decalcification for Ammonia sp. and Elphidium crispum (7.25≤pH≤7.5).…”

Comparison of Corrosion Rate in the Environment of 10% Acetic Acid solution with different Deflection.

“…Based on the test results of microstructure and microscope polarized, there is a phenomenon corrosion stress cracking, i.e transgranular stress cracking corrosion and intergranular stress cracking corrosion. [1] From the results of the study that the samples with different deflections in the variation of exposure time, the corrosion rate is getting smaller because the corrosion material is not soluble in the solution so it inhibits the corrosion process as in table 1, table 2 and based on the figure 4 for deflection 1 cm or deflection 1.5 cm. And based on the microstructure result that the carbon steel pipe sample of API 5L-X65 occurs stress corrosion cracking either transgranular corrosion or intergranular corrosion as in figure 5 [2].…”

Effect of Seawater Acidification on Physiological and Energy Metabolism Responses of the Common Cockle (Anadara Antiquata) of Gazi Bay, Kenya

“…Coastal areas are among the most productive and dynamic marine ecosystems, supporting a variety of essential habitats and species (Velez et al, 2016a). However, the absorption of atmospheric CO 2 by the ocean since industrial times has progressively changed seawater chemistry through a process known as ocean acidification (OA) (Small et al, 2010;Guamán-Guevara et al, 2019). These nearshore areas are characterized by small-scale interactions among physical, biological, and anthropogenic factors, which contribute to a relatively large variability (spatial and temporal) of seawater carbonate chemistry relative to the open ocean (Range et al, 2012).…”