Temperature as a likely driver shaping global patterns in mineralogical composition in bryozoans: Implications for marine calcifiers under Global Change

Abstract

The Southern Ocean is showing one of the most rapid responses to human-induced global change, thus acting as a sentinel of the effects on marine species and ecosystems. Ocean warming and acidification are already impacting benthic species with carbonate skeletons, but the magnitude of these changes to species and ecosystems remains largely unknown. Here we provide the largest carbonate mineralogical dataset to date for Southern Ocean bryozoans, which are diverse, abundant and important as carbonate producers, thus making them excellent for monitoring the effects of ocean warming and acidification. To improve our understanding of how bryozoans might respond to ocean warming and acidification, we assess latitudinal and seafloor temperature patterns of skeletal mineralogy using bryozoan species occurrences together with temperature data for the first time. Our findings, combining new mineralogical data with published data from warmer regions, show that the proportions of high-Mg calcite and bimineralic species increase significantly towards lower latitudes and with decreasing seawater temperature. These patterns are consistent with the hypothesis that seawater temperature is likely a significant driver of variations in bryozoan mineralogy at a global scale.

Temperature as a likely driver shaping global patterns in mineralogical composition in bryozoans: implications for marine calcifiers under global change

“…Our data illustrate that the skeletons of most Southern Ocean species of bryozoans are formed of IMC, some of LMC and a few of HMC, consistent with previous global data (Fig. 3, 4; Figuerola et al 2022) (Smith et al 2006, Taylor et al 2009). However, we found higher IMC (67 versus 65–58%) and LMC (32 versus 29–27%) percentages and a lower HMC (1 versus 13–8%) percentage compared to those from our own and previous global data as expected due to the higher solubility of HMC in cold waters (Mucci 1983, Davis et al 2000, Smith et al 2006, Taylor et al 2009).…”

“…The proportions of occurrence records of different mineral types remained stable south of the Polar Front, with aragonite almost completely absent and bimineralic occurrence records less than 3% with most occurrence records (97%) dominated by calcite. North of the Polar Front was also dominated by calcite but to a lower level (~62–97%) and higher levels of bimineralic skeletons (~3–32% and 100% for a single occurrence record south of 60°S) (Figuerola et al 2022). There was also a trend of increasing aragonite (from zero up to a maximum of ~9.5%) with decreasing latitude (Fig.…”

“…In addition, two cosmopolitan aragonitic species, Membranipora membranacea , which had high occurrence records (6759), and Hippothoa divaricata , which had some Antarctic occurrence records (n = 21), could mask the general trend (Figuerola et al 2022). These species could also switch in mineralogy in higher latitudes, although they were not found below zero degrees Celsius.…”

“…We integrated new data from the current study with recent (Krzeminska et al 2016, Loxton et al 2018) and older mineralogy data from cheilostome and cyclostome bryozoans worldwide previously summarized by Smith et al (2006) and Taylor et al (2009). Available mineralogical data from genera with undetermined species, and also known species from the White Sea which has unusual conditions that may mask temperature influence (Krzemińska et al 2022), were removed from the analyses (Figuerola et al 2022). The global dataset comprised 549 species (102 Southern Ocean species, excluding six genera with indeterminate species).…”

“…Data are available from the Dryad Digital Repository: <https://doi.org/10.5061/dryad.bvq83bkbm> (Figuerola et al 2022).…”