Interactive effects of temperature, food and skeletal mineralogy mediate biological responses to ocean acidification in a widely distributed bryozoan

Abstract

Marine invertebrates with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification (OA) due to the elevated solubility of this form of calcium carbonate. However, skeletal composition can vary plastically within some species, and it is largely unknown how concurrent changes in multiple oceanographic parameters will interact to affect skeletal mineralogy, growth and vulnerability to future OA. We explored these interactive effects by culturing genetic clones of the bryozoan (formerly) under factorial combinations of dissolved carbon dioxide (CO), temperature and food concentrations. High CO and cold temperature induced degeneration of zooids in colonies. However, colonies still maintained high growth efficiencies under these adverse conditions, indicating a compensatory trade-off whereby colonies degenerate more zooids under stress, redirecting energy to the growth and maintenance of new zooids. Low-food concentration and elevated temperatures also had interactive effects on skeletal mineralogy, resulting in skeletal calcite with higher concentrations of magnesium, which readily dissolved under high CO For taxa that weakly regulate skeletal magnesium concentration, skeletal dissolution may be a more widespread phenomenon than is currently documented and is a growing concern as oceans continue to warm and acidify.

Spatio-temporal variation of skeletal Mg-calcite in Antarctic marine calcifiers

“…warming, acidification and pollution) which should be considered as they can co-occur. The combined effects of increased temperature and reduced pH (from increased CO 2 concentrations) on the widely distributed cheilostome bryozoan Jellyella tuberculata (Bosc, 1802), including from subAntarctic regions [67], was found to dissolve their zooids, possibly due to an increase of skeletal Mg content at high temperatures which made the skeletons more susceptible to dissolution under high CO 2 [68]. Therefore, organisms living in Antarctic coastal areas that have experienced significant warming in recent years (e.g.…”

Abiotic and biotic interactions in the diffusive boundary layer of kelp blades create a potential refuge from ocean acidification

“…This trend was less pronounced at pH 7.7 in the dark whereby the DBL oxygen concentrations looked similar for epiphytized and bare blades. The pH decrease in the mainstream seawater did not affect the respiration rates of the epiphyte/blade complex at the blade surface likely because bryozoans present a great plasticity and different strategies which enable them to cope with pH decrease (Swezey, Bean, Hill, et al., ; Swezey, Bean, Ninokawa, et al., ). Moreover, the pH fluctuations occurring in the microenvironment of seaweeds can reach very low levels, from 8.1 down to 7.0 in the dark (De Beer and Larkum, ; Hurd et al., ), and bryozoans living upon the blades may be used to these daily drops in the surrounding pH.…”

Skeletal carbonate mineralogy of Scottish bryozoans

“…There is also a wide range of Magnesium (Mg) content in bryozoan calcite, ranging from low magnesium carbonate (LMC, < 4 wt% MgCO 3 ), through intermediate magnesium carbonate (IMC, > 4 wt%MgCO 3 to < 8 wt%MgCO 3) to high magnesium carbonate (HMC, > 8 wt%MgCO 3 ) [ 20 , 27 ] with most bryozoans featuring low to intermediate Mg-calcite [ 27 , 20 , 29 , 30 ]. This variation can be ascribed to environmental, physiological or phylogenetic influences [ 31 ].…”