No abstract

The elemental signature of trace and minor elements within biominerals has been used to investigate the larval dispersal of bivalves. We investigated the potential of this technique by examining elemental signals in juvenile shells of the hard clam Mercenaria mercenaria within an estuarine−lagoonal system near Cape Lookout, North Carolina, USA. We assessed the spatial distinction (~12 to 40 km) and temporal stability (fall versus spring) of elemental concentrations using inductively coupled plasma mass spectrometry (ICP-MS). Twelve minor and trace elements were present at detectable levels in all shell samples: calcium (Ca), manganese (Mn), aluminum (Al), titanium (Ti), cobalt (Co), copper (Cu), barium (Ba), magnesium (Mg), zinc (Zn), lead (Pb), nickel (Ni), and strontium (Sr). Discriminant function analyses (DFA) using metal to Ca ratios as independent variables correctly assigned hard clams to their site of collection with 100% success from both fall and spring sampling events. Mn:Ca ratio proved to be the most effective discriminator explaining 91.2 and 71.9% of our among-group variance, respectively. Elemental concentrations within juvenile shell differed temporally. A combined DFA approach using shell from both sampling events obtains a classification success of 81.9%. Mn:Ca ratio explained the bulk of among group variance (89.9%) and was consistently different among water masses during each season. Our results demonstrate for the first time the existence of small-scale spatial differences (~12 km) in the elemental chemistry of juvenile bivalve shell exclusively within an estuarine− lagoonal system. Our results suggest that the validation of a similar chemical signal of M. mercenaria larval shells is possible and may be used to trace the dispersal trajectory of this economically important species.KEY WORDS: Mercenaria mercenaria · Microchemistry · Larval dispersal · Population connectivity · Estuary · Plasma mass spectrometry Resale or republication not permitted without written consent of the publisher 157 Fig. 1. Mercenaria mercenaria. Juvenile hard clam shell showing the retained larval shell, the prodissoconch (PD)