Seasonal growth variation in Chlamys islandica (Bivalvia) from sub-Arctic Greenland is linked to food availability and temperature

Abstract

In order to assess the role of different environmental parameters in the population dynamics of marine invertebrates in the Arctic, we examined seasonal variation in individual biomass, shell growth, and mass production of somatic and reproductive tissues of immature and maturing scallops Chlamys islandica suspended in culture nets at 15 and 30 m depth in SW Greenland from May 2007 to October 2008. All 3 parameters varied both seasonally and between depths. Individual shell growth rate and biomass were poor proxies for the actual mass growth rate on a seasonal scale. Minimum and maximum mass growth rates were observed from November to February and in April-May, respectively. Simultaneous monitoring of biotic and abiotic parameters in the water column made it possible to establish a growth model relating variation in mass growth rate to variation in environmental conditions. The best-fit model (R 2 = 0.71) indicated that total mass growth rate depended on chlorophyll a concentration, carbon-to-nitrogen ratio of seston, and water temperature. While availability of high-quality food items affected growth positively, the growth model indicated a negative effect of increasing temperature on the mass growth rate of C. islandica. These results indicate that scallops in SW Greenland are resource-limited and that elevated temperature through its effect on metabolic costs reduces growth efficiency. Hence, it is most likely that the growth capacity of C. islandica in SW Greenland is either never realized or only attained for short periods of time (hours to days) under the present conditions. KEY WORDS: Bivalve · Scallop · Temporal dynamics · Production · Food availability · Sub-Arctic · Pectinid · Temperature · Shell growth Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 407: [71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] 2010 tion (Rysgaard et al. 1999, Dagg et al. 2004, Wassmann et al. 2006, Arrigo et al. 2008, potentially leading to altered food conditions for secondary producers. Low temperature is considered an important component of high-latitude marine environments, affecting physiological rates of ectotherms at all trophic levels (Gillooly et al. 2001). Thus, it might be expected that future changes in ocean temperature and food availability in the Arctic will affect the productivity of secondary producers (Blicher et al. 2007). However, the combined effect may not be straightforward. Hence, it is still debated whether the apparent temperature-dependence of the basal metabolism of ectotherms is solely a consequence of thermodynamics, or if the processes involved in metabolism have been subject to evolutionary adaptation to maximize production in a given environment, i.e. maximizing the difference between energy intake and metabolic costs (e.g. Clarke & Johnston 1999, Gillooly et al. 2001, Clarke 2003. In any case, it seems likely that the effect of increasing temperature on organism growth is dependent on the ability of an organism to co...

Seasonal and spatial variations in the RNA:DNA ratio and its relation to growth in sub-Arctic scallops

“…By including scallop SH, the model fit was improved (Table 1, Model II), indicating that G m decreases with increasing individual size. This was expected (Blicher et al 2010), and the inclusion of SH in Model II (Table 1) can be regarded as a simple correction for this size dependence. However, the large fraction of unexplained variation and the significant autocorrelation of the residuals seemed to indicate that RD explained the seasonal cycle in the mass growth rate of Chlamys islandica poorly.…”

“…In the following text we refer to condition and mass growth in terms of total tissue mass. Blicher et al (2010) (n = 502, R 2 = 0.94, p < 0.001)…”

“…First of all, the difference in mass growth rate between scallops at 15 and 30 m depth, respectively, which was most pronounced during late summer, was not reflected in the RD data. Also, during the summer of 2008, the RD of wild scallops at 50 to 60 m was not significantly different from that of cultured scallops, which was unexpected because size-at-age data for scallops collected at the site have indicated relatively slow growth compared to suspended scallops (Blicher et al , 2010. Moreover, the peaks in mass growth rate during spring and summer could not be identified in the RD, which did not show any large fluctuations from May to August, but rather appeared to have a stable and high level during this period.…”

Abundance, oxygen consumption and carbon demand of brittle stars in Young Sound and the NE Greenland shelf

“…It should be noted that values are approximate as they rely on general assumptions regarding the organic C:AFDW ratio and the allometric relationship between biomass and disc diameter to make data directly comparable. Moreover, a general relationship such as this does not consider the potential seasonal variation in macrobenthic activity, which has been reported in other studies in polar areas (Brockington & Clarke 2001, Blicher et al 2010). However, it can be used to produce a preliminary estimate of the carbon requirements of this abundant taxon in the Arctic using a more general approach based on size structure and abundance, which can be effectively described using sea-floor images.…”

The Indo-Pacific oysterSpondylus spinosusSchreibers, 1793 in the Eastern Mediterranean Sea: reproductive features

“…3), and it thus resembles many other bivalves in this respect (e.g., C. islandica, Greenland [Blicher et al 2010];S. calcifer, Gulf of California [Cudney-Bueno and Rowell 2008]; P. magellanicus [Wahle and Jumars 2014]).…”