Cephalopod beak sections used to trace mercury levels throughout the life of cephalopods: The giant warty squid Moroteuthopsis longimana as a case study

Abstract

Cephalopods represent an important pathway for mercury transfer through food webs. Due to the general difficulties in capturing oceanic squid, beaks found in the diet of top predators can be used to study their life-cycles and ecological role. Using upper beaks of the giant warty squid Moroteuthopsis longimana (major prey in the Southern Ocean), we describe a method to assess mercury concentrations along the life of cephalopods through the segmentary analysis of beak sections (i.e. tip of the rostrum and subsections along the hood). Distinct total mercury concentrations in the different subsections support that beaks can be used to study mercury levels in different periods of cephalopods' life-cycle. Mercury values in the anterior (1.3-7.9 μg kg^-1 dw) and posterior (7.8-12.5 μg kg^-1 dw) subsections of the hood reflect juvenile and adult stages, respectively. Furthermore, these results confirm that mercury bioaccumulates continuously throughout the individuals' life, with adults doubling their mercury concentrations to juveniles.

Keywords: Bioaccumulation; Mercury; Ontogenetic shifts; Southern ocean; Trace elements.