Trace metals in Antarctic clam shells record the chemical dynamics of changing sea ice conditions

Abstract

The dynamics of freeze and thaw events in Antarctic sea ice impart chemical changes in the underlying sea water. Trace metals in sea ice and accumulated through deposition of dust are released into sea water as sea ice breaks up in spring. Clams such as Laternula elliptica incorporate a record of these and associated chemical dynamics in their carbonate shells. In 2012, we collected samples of L. elliptica from three sites along a sea ice persistence gradient in McMurdo Sound, Ross Sea Antarctica. Concentrations of trace metals in the chondrophore of each shell were measured by laser ablation inductively coupled plasma mass spectrometry. Ablations transected annual growth increments creating time series ranging in length from 13 to 25 yr. An 8‐yr time period of persistent sea ice, associated with presence of the B‐15 and C‐19 icebergs at the entrance of McMurdo Sound, was clearly resolved in the trace element time series. Conservative trace metals (Sr, Ba) were found at higher concentrations, and highly scavenged elements (Pb, Cu) were found at lower concentrations at sites with more persistent sea ice and during the 8‐yr period of iceberg‐influenced sea ice persistence. Bioactive trace metals (Fe, Ni) were found in higher concentrations during ice free conditions, associated with a period of high pelagic productivity. Our results provide an important case study for understanding the chemical signature of changing sea ice dynamics as reflected in bivalve shell material under a changing Antarctic climate.

DNA from mollusc shell: a valuable and underutilised substrate for genetic analyses

“…Bivalve molluscs have been widely used for coastal monitoring anthropogenic aquatic contaminants such as heavy metals (Goldberg et al, 1978;Azizi et al, 2018), micro plastics (Ward, Rosa & Shumway, 2019) and human pathogen transmission (Gyawali et al, 2019;Razafimahefa, Ludwig-Begall & Thiry, 2019) together with seasonal ecotoxicological problems such as algal blooms (Gibble, Peacock & Kudela, 2016;Hinder et al, 2011). Their shells have also been used for almost four decades as a proxy to determine exposure to heavy metal concentrations in modern samples (Yap et al, 2002;Koide, Lee & Goldberg, 1982), historic (Wing et al, 2019) and archaeological samples (Binkowski et al, 2019). Along with being a source of genetical material not just of the individual itself, but pathogens and conditions that they've been exposed to makes mollusc shells a valuable resource to assess the environment in present and past times.…”

Sclerochronology in the Southern Ocean

“…The authors discussed the relationships between sea ice persistence, marine primary production and trace metal availability and incorporation into the shell. As hypothesised by Dick et al (2007) an increased sampling resolution in LA-ICP-MS provided Wing et al (2020) a technical advance in the study trace element incorporation into the shell of L. elliptica. Variability of conservative (Li, Ba, Mg, and Sr), bioactive (Fe, Co, Ni, Zn, and P), and highly scavenged (Al, Cu, and Pb) trace metals in L. elliptica shell seem to be highly coupled with sea ice variability and its cascading effects in the ecosystem (Wing et al 2020).…”

“…The authors also pointed out that sampling resolution was still a limitation and an improvement in analytical techniques could offer a new understanding of trace element incorporation in the shell (Dick et al 2007). A modern example can be found in the work done by Wing et al (2020) in L. elliptica, where 17 trace elements were analysed over shells lifespans ranging from 13 to 25 years. The lifespans of these specimens coincided with an 8-year period of persistent sea ice influenced by the presence of two large icebergs in McMurdo Sound, the area of study (Wing et al 2020).…”

“…A modern example can be found in the work done by Wing et al (2020) in L. elliptica, where 17 trace elements were analysed over shells lifespans ranging from 13 to 25 years. The lifespans of these specimens coincided with an 8-year period of persistent sea ice influenced by the presence of two large icebergs in McMurdo Sound, the area of study (Wing et al 2020). The authors discussed the relationships between sea ice persistence, marine primary production and trace metal availability and incorporation into the shell.…”

Anatomy and behavior of Laternula elliptica, a keystone species of the Antarctic benthos (Bivalvia: Anomalodesmata: Laternulidae)

“…Its wide distribution in the Antarctic realm, high abundance, ease of collection, and ability to survive under experimental conditions have allowed it to reach model status, having been studied in hundreds of scientific articles ( Waller et al, 2016 ) representing a broad spectrum of biological disciplines. Among these are investigations focusing on metabolism and energy budget ( e.g ., Agüera et al, 2017 ; Ahn & Shim, 1998 ; Momo et al, 2002 ), biochemistry ( Ahn, 2000 ; González & Puntarulo, 2011 ), heavy metal concentrations and pollution ( Ahn et al, 1996 ; Lister, Lamare & Burritt, 2015 ; Wing et al, 2020 ), shell composition and structure ( Barrera et al, 1994 ; Nehrke et al, 2012 ; Sato-Okoshi & Okoshi, 2008 ), reproduction and larval development ( Ansell & Harvey, 1997 ; Bigatti, Penchaszadeh & Mercuri, 2001 ; Kang, Ahn & Choi, 2003 , 2008 ; Pearse, Bosch & McClintock, 1986 ; Pearse et al, 1987 ; Powell, Tyler & Peck, 2001 ), ageing ( Peck, Powell & Tyler, 2006 ; Philipp, Pörtner & Abele, 2005 ), ocean acidification and warming ( Bylenga, Cummings & Ryan, 2015 , 2017 ; Cummings et al, 2011 ), thermal stress and hypoxia ( Kim et al, 2009 ; Morley et al, 2007a , 2009a , 2009b , 2012 ; Park et al, 2008 ; Peck, Pörtner & Hardewig, 2002 ; Peck et al, 2004 ; Pörtner, Peck & Hirse, 2006 ), and iceberg scouring ( Harper et al, 2012 ; Philipp, Husmann & Abele, 2011 ). Numerous molecular studies have been applied to the species, from assembling the complete mitochondrial genome ( Park & Ahn, 2015 ), transcriptomics ( Clark et al, 2010 ), and studying heat shock proteins ( Ramsøe, Clark & Sleight, 2020 ; Truebano et al, 2013 ), to treating it as the exemplar for its family in class-wide phylogenetic studies ( Bieler et al, 2014a , 2014b ; Combosch et al, 2017 ).…”