Variability in the skeletal mineralogy of temperate bryozoans: the relative influence of environmental and biological factors

Abstract

Bryozoans exhibit a highly variable geochemistry within their calcium carbonate skeletons. Previous studies have predominantly attributed this variability to differences in seawater temperature influencing the relative deposition of aragonite and calcite, and the extent of magnesium incorporation into the calcite lattice. However, the patterns and scale of this variability have not been examined in detail. We conducted a high-replicate, multi-site study on the skeletal mineralogy of temperate Northern Hemisphere bryozoans to investigate the range of skeletal aragonite and Mg-calcite variability between species and the relative influence of environmental and biological factors on skeletal biogeochemistry. During a cruise in May 2012 in Scapa Flow, Orkney, Northeast Scotland, 480 specimens from 3 bryozoan species were collected by SCUBA diving. Samples were obtained from 5 study sites with similar depths and physical characteristics. All specimens were collected within the same week and were selected to be of similar size, age and breeding status. The results of X-ray diffraction analysis showed that wt% MgCO 3 in calcite and wt% aragonite in total CaCO 3 were statistically different between sites for all species. This may be explained by differential population connectivity between sites influenced by the tidal regimes of Scapa Flow. No temperate bryozoan species showed the expected positive trends of increasing wt% MgCO 3 in calcite or wt% aragonite in total CaCO 3 with seawater temperature. Based on the data generated in this study, we suggest that both environmental and biological factors are involved in the control of skeletal mineralogy in some temperate bryozoan species.

Carbonate mineralogy of a tropical bryozoan biota and its vulnerability to ocean acidification

“…All of the bryozoans from Langkawi and Penang are shore samples of colonies from very shallow water (<10 m), whereas many of the bryozoans reported in previous publications came from mid-to outer shelf depths. Analyses of bryozoan assemblage mineralogy relative to depth on the continental shelf are lacking, although Loxton et al (2014) found a positive correlation between depth and the proportion of aragonite in skeletons of the bimineralic cheilostome Microporella ciliata (Pallas, 1766) in NE Scotland. The generality of this trend within and among species is unknown but if applied to the latitudinal comparisons made here more aragonite would be expected in bryozoans from deeper parts of the Malaysian shelf and the contrast with regions of higher latitude would be even greater.…”

“…The mineralogy of the bryozoan skeleton is under a high degree of organismal control (Smith 2014;, although bimineralic species may exhibit apparent ecophenotypic variability in the proportions of calcite and aragonite in their skeletons (e.g. Lombardi et al 2008;Loxton et al 2014).…”

Geochemical and Crystallographic Study ofTurbo Torquatus(Mollusca: Gastropoda) From Southwestern Australia

“…The biological or ''vital effect'' is a time-independent offset from theoretical/experimental equilibrium and thermodynamics controlled by physiological processes. Many organisms exert a certain level of control on CaCO 3 precipitation as identified in previous studies of foraminiferans (e.g., Bentov & Erez, 2006), corals (e.g., Marshall, 1996;Tambutt e et al, 1996), bivalves (e.g., Kennedy et al, 1969), gastropods (e.g., Nehrke & Nouet, 2011;Yao et al, 2010), and bryozoans (e.g., Loxton et al, 2014). As a consequence, it is essential to consider biological controls in the use of biogenic materials as proxies for environmental reconstruction (e.g., Austin & James, 2008, and references therein).…”

Diversity dynamics of Ordovician Bryozoa

“…Kukliński & Taylor ; Loxton et al . ). Marine bryozoans are usually stenohaline, but some unskeletonized ctenostomes can tolerate brackish conditions.…”

“…Water temperature also influences the chemical composition of bryozoan skeletons, generally by increasing the Mg content with increasing temperature (e.g. Kukli nski & Taylor 2008;Loxton et al 2014). Marine bryozoans are usually stenohaline, but some unskeletonized ctenostomes can tolerate brackish conditions.…”