Geographical differences in growth rates of Arctica islandica (Mollusca: Bivalvia) from the North Sea and adjacent waters

Abstract

Geographical differences in the shell growth rate of several populations of the bivalve Arctica islandica (Mollusca: Bivalvia) were estimated by using the growth lines laid down during their first ten years of life. Attention was focused on populations from the North Sea, but for comparison small samples from adjacent waters were also analysed. A four-fold difference in the average growth rate was found between the slowest and fastest growing shells.Principal component analysis was used to summarize the inter-relationships between environmental variables and growth rates. Shell growth correlated positively with primary production and temperature and inversely with depth and the silt content of the sediment. The North Sea specimens were found to have a strong positive correlation with grain size. Since sediment characteristics also depend on bottom currents, it is suggested that these increased rates reflect lateral seston flux as additional food supply.In a multiple regression model, applied to all available data, average annual temperature, primary production and the interaction between production and water depth explained 50% of the variance. The derived standard coefficients for temperature, primary production and the interaction between depth and primary production were 0.90, 0.47 and −0.92 respectively. The results of this study suggest that the temperature effects on in situ shell growth are easily overruled by other environmental factors.If a similar model was calculated with North Sea data only, 75% of the variance was explained by temperature, primary production and depth×primary production. The standard coefficient for primary production was 1.26. The role of temperature in explaining the observed growth differences is negligible since the standard coefficient is −0.098. The interaction term, depth×primary production had a standard coefficient of −0.95.

The effects of environment on <i>Arctica islandica</i> shell formation and architecture

“…Numerous previous studies demonstrated that the growth rate of A. islandica is linked to environmental variables (e.g., Witbaard et al, 1997Witbaard et al, , 1999Schöne et al, 2004;Butler et al, 2010;Mette et al, 2016). However, the relative importance of the main factors, temperature and food supply/quality driving shell formation are still not well understood.…”

Cell turnover in tissues of the long-lived ocean quahog Arctica islandica and the short-lived scallop Aequipecten opercularis

“…Moreover, environmental change in the German Bight area, including strong eutrophication in the 1960s-1990s (Rijinsdorp and van Leeuwen 1996) and slow but steadily increasing water temperatures around Helgoland (Wiltshire and Manly 2004), could cause thinning of the A. islandica population and the reduction of individual life expectancy. Indeed, conditions around Iceland are more favourable in many respects including food availability and absence of severe fishery impacts (Witbaard et al 1999;Kaiser et al 2006), which explains the higher densities of Iceland A. islandica (Ragnarsson and Thórarinsdottier 2002;Witbaard and Bergman 2003).…”

Physiological responses to self-induced burrowing and metabolic rate depression in the ocean quahogArctica islandica

“…Recorded MLSPs (MLSP rec ) of A. islandica differ regionally between populations from sub-Arctic environments around Iceland (IC) with individual ages of more than 350years (Schöne et al, 2005;Wanamaker et al, 2008), and from the German Bight (GB) with recorded individual MLSPs of 150years (Witbaard and Klein, 1994;Witbaard et al, 1999;Epplé et al, 2006). Low salinity populations with conspicuously shorter life expectancies have established in brackish waters of the sub-Arctic White Sea with a MLSP rec of 53years and the temperate Baltic Sea with MLSP rec of 40years (Begum et al, 2010).…”