Ligament, hinge, and shell cross-sections of the Atlantic surfclam (Spisula solidissima): Promising marine environmental archives in NE North America.

Pierre Poitevin,Aurélie Jolivet,Pascal Lazure,Bernd R Schöne,Julien Thébault,Laurent Chauvaud

doi:10.1371/journal.pone.0199212

Abstract

The Atlantic surfclam (Spisula solidissima) is a commercially important species in North American waters, undergoing biological and ecological shifts. These are attributed, in part, to environmental modifications in its habitat and driven by climate change. Investigation of shell growth patterns, trace elements, and isotopic compositions require an examination of growth lines and increments preserved in biogenic carbonates. However, growth pattern analysis of S. solidissima is challenging due to multiple disturbance lines caused by environmental stress, erosion in umbonal shell regions, and constraints related to sample size and preparation techniques. The present study proposes an alternative method for describing chronology. First, we analyzed growth patterns using growth lines within the shell and hinge. To validate the assumption of annual periodicity of growth line formation, we analyzed the oxygen isotope composition of the outer shell layer of two specimens (46°54'20"N; 56°18'58"W). Maximum δ18Oshell values occurred at the exact same location as internal growth lines in both specimens, confirming that they are formed annually and that growth ceases during winter. Next, we used growth increment width data to build a standardized growth index (SGI) time-series (25-year chronology) for each of the three parts of the shell. Highly significant correlations were found between the three SGI chronologies (p < 0.001; 0.55 < τ < 0.68) of all specimens. Thus, ligament growth lines provide a new method of determining ontogenetic age and growth rate in S. solidissima. In a biogeographic approach, the shell growth performance of S. solidissima in Saint-Pierre and Miquelon was compared to those in other populations along its distribution range in order to place this population in a temporal and regional context.

Highlights

The Atlantic surfclam (Spisula solidissima) is the largest bivalve in the western North Atlantic, reaching a maximum length of 226 mm and longevity of 37 years in the Middle Atlantic Bight population [1]
Mean salinity at a depth of 0–5 m was calculated from 85 measurements recorded between the beginning of August 2010 and the middle of November 2010 near the S. solidissima collection site and found to be 31.49 ± 0.03 (Fig 4)
This study demonstrates that surfclams from Saint-Pierre and Miquelon (SPM) have annual shell growth increments

Summary

Introduction

The Atlantic surfclam (Spisula solidissima) is the largest bivalve in the western North Atlantic, reaching a maximum length of 226 mm (commercial minimum size: 120 mm in USA and 90 mm in Canada) and longevity of 37 years in the Middle Atlantic Bight population [1]. S. solidissima is a commercially important species in Canada and the US Exclusive Economic Zone (EEZ). S. solidissima is a good example of a commercially important species undergoing biological and ecological changes that have been attributed to increased bottom water temperature, the fishery activity, or a combination of both [3,4,5,6,7,8]. These data are measured within the accretionary hard parts of the clam [9,10,11]. A variable that integrates multiple physical and biological factors, represents an integrative approach to monitoring the impact of environmental changes in S. solidissima populations along a geographic gradient during the last few decades [7, 12,13,14]

Methods

Results

Discussion

Conclusion