ORE Open Research Exeter TITLE Sclerochronology in the Southern Ocean AUTHORS Roman Gonzalez, A JOURNAL Polar Biology DEPOSITED IN ORE 14 July 2021 This version available at http://hdl.handle.net/10871/126395 COPYRIGHT AND REUSE Open Research Exeter makes this work available in accordance with publisher policies. A NOTE ON VERSIONS The version presented here may differ from the published version. If citing, you are advised to consult the published version for pagination, volume/issue and date of publication Polar Biology https://doi.org/10.1007/s00300-021-02899-0 REVIEW Sclerochronology in the Southern Ocean Alejandro Roman Gonzalez1 Received: 23 December 2019 / Revised: 18 March 2021 / Accepted: 8 June 2021 © The Author(s) 2021 Abstract This manuscript aims to provide a comprehensive review of the work done by Antarctic sclerochronology research across diferent taxa (arthropods, bivalves, brachiopods, bryozoans, cephalopods, hard and soft corals, gastropods, echinoderms and teleost fsh), provide an analysis of current challenges in the discipline and start a discussion of what sclerochronology can ofer for Antarctic research in future. The Southern Ocean ecosystem remains largely unstudied in part for its remote- ness, extreme climate and strong seasonality. This lack of knowledge, some of it even on basic biological information, it is especially worrying due to ongoing climate-driven changes that the Southern Ocean ecosystem is experiencing. Lack of long-term in situ instrumental series has also being a detriment to understand long-term feedbacks between the physical environment and the ecosystem. Sclerochronology, the study of periodic accretional patterns in the hard body structures of living organisms, has contributed to a wide range of Antarctic research disciplines (e.g. paleoclimate reconstructions, population structure analysis, environmental proxies). This review highlights a disparity in research focus by taxa with some groups (e.g. bivalves, teleost fsh) attracting most of the research attention, whereas other groups (e.g. gastropod) have attracted much little research attention or in some cases it is almost non-existent (e.g. echinoderms). Some of the long-lived species considered in this review have the potential to provide the much-needed high-resolution eco-environmental proxy data and play an important role in blue carbon storage in the Sothern Ocean. Another issue identifed was the lack of cross- validation between analytical techniques. * Alejandro Roman Gonzalez [email protected] 1 Centre for Geography and Environmental Science, University of Exeter, Penryn campus, Cornwall TR10 9FE, UK Vol.:(0123456789)1 3 Polar Biology Graphic abstract Keywords Antarctic · Sclerochronology · Southern Ocean · Ontogeny · Geochemistry · Growth patterns Introduction sclerochronology has focussed on a wide range of scientifc interests including ontogeny, paleoclimate, archeology and Sclerochronology is the study of growth patterns preserved geochemistry. A key concept in sclerochronology is that all in the hard skeletal structures of living organisms (e.g. individuals within a population respond to common envi- shells, bones, coral reefs) (e.g. Clark 1974; Richardson 2001; ronmental cues/drivers so they display common synchro- Gröcke and Gillikin 2008; Oschmann 2009; Schöne and Gil- nous growth in addition to their own individual biological likin 2013; Butler and Schöne 2017; Butler et al. 2019; Gil- growth rhythm. The sclerochronological literature is rich in likin 2019; Trofmova et al. 2020). Transferring much statis- terminology (e.g. growth increments, growth rings, growth tical knowledge from dendrochronology (tree-ring analysis), marks, growth checks) which also will be refected in some 1 3 Polar Biology part in this review. A distinction should be made in advance used in this review as the portion of growth contained within that in some sclerochronological records (i.e. fsh otoliths two consecutive growth marks/checks. Statistical techniques and gastropod and cephalopod statoliths the term growth used in sclerochronology (many derived from dendrochro- ring) would be preferred over growth increment. Also the nological research) such as: detrending and regional curve term “annuli” is also commonly used in teleost fsh otolith standardization allow to separate individual and populational research; however, in this review it has been substituted for biological growth rhythm from the common synchronous the term “ring” to provide a reduced terminology and avoid growth attributed to common environment drivers in the life confusion. Another clarifcation to be made is the distinction history growth pattern (e.g. Brifa and Jones 1990; Esper between the terms: growth increment and growth check or et al. 2003; Butler et al. 2010; Roman-Gonzalez et al. 2017). mark. Growth check or mark is used in this review as the thin Thus allowing to investigate independently both the biologi- line that it is formed in many sclerochronological records at cal (i.e. individual specifc), population and environmen- the end of the growing season, whereas growth increment is tally driven growth (Fig. 1). Some of the research concepts Fig. 1 Sclerochronology can be used with a varied range of marine organisms (e.g. fsh, bivalves, gastropods, bryozo- ans). In addition, sclerochronol- ogy can provide an insight into varied felds such as: (1) eco- system composition and trophic webs, (2) primary production and marine carbon fuxes, (3) population structure and distri- bution and ageing, (4) current and past ocean temperature and (5) oceanic circulation which in the Southern Ocean are heavily afected by sea ice processes and salinity gradients (*) 1 3 Polar Biology studied by sclerochronology are outlined in Fig. 1, which in the growth increment patterns and in the geochemistry will be discussed further in the main text of this review. of the hard skeletal structures for many Antarctic species. Much sclerochronological research has been undertaken Compared to other proxy records such as ice or sediment in temperate environments and has focussed on long-lived cores, sclerochronology can be annually resolved and abso- species (some of which can attain lifespans spanning sev- lutely dated (i.e. specifc calendar years can be assigned to eral centuries) for a number of reasons (e.g. ageing stud- each growth increment) and the records have the potential to ies, constructions of long proxy records that extend beyond extend beyond the onset of in situ instrumental records with the onset of instrumental dataset). Commercially important crossmatching techniques. In addition, sclerochronological shorter-lived species have attracted attention in the context material such as shells, coral skeleton, cephalopod beaks, of provide scientifc advisory datasets (e.g. population age can be collected from research cruises using a range of sam- structure, recruitment, age of maturity) to the respective fsh- pling gear away from Antarctic research bases and therefore eries’ governing bodies (e.g. Panfli et al. 2002; Hollyman extend the spatial coverage of scientifc data. Many of the et al. 2018a, b; Hunter et al. 2018). species suitable for sclerochronological analysis inhabit Many authors highlight the systemic lack of long-term environments where scientifc data are scarce (e.g. deep-sea, instrumental records in the Southern Ocean and how this gap littoral areas) and they also have a pan-Antarctic distribution limits our understanding of processes and feedbacks in the providing the potential to develop networks of local climatic climate system at southern high latitudes (e.g. Turner and monitoring stations. Data extracted from sclerochronologi- Comiso 2017). Much of this is due to the remoteness and cal records can also feed back into global climate models to harshness of the environment, which limits the operational provide more accurate predictions. life of deployed equipment, and the logistical and economic Thus purpose of this manuscript is to provide the research costs of developing long-term environmental monitoring community with a comprehensive review of the research programmes. Many nations operating Antarctic research pro- on, and related to sclerochronology in the Southern Ocean grammes do not have a year-round, long-term marine moni- and subantarctic islands, provide an analysis of current limi- toring systems in place, such as: the UK RaTS (est. 1997), tations of Antarctic sclerochronology and a discussion of USA Palmer-LTR (est. 1990) and McMurdo Oceanographic possible research avenues to expand the use of Antarctic Observatory (MOO, est. 2017). These few programmes are sclerochronology. This review will cover publications on the bound to the location of their respective Antarctic research following topics: chronology construction, ontogeny and age bases, which does not provide an adequate spatial coverage determination, paleoclimate reconstructions and ontogenetic for the Southern Ocean. geochemical variability, and on the following taxa: bivalves, Thus, the great majority of the Southern Ocean research gastropods, cephalopods, echinoderms, brachiopods, bryo- community has been forced either to deal with scarce zoans, corals and teleost fsh. The common thread in all stud- environmental datasets and/or take advantage of satellite ies reviewed is the analysis of accretional hard skeletal struc- measurements, which ofer ample spatial coverage. Since tures of marine organisms which record the specimens’ life the onset of the satellite era, environmental