CR prepress abstract  -  doi: 10.3354/cr00763

ABSTRACT: Thermal tolerance windows were investigated in lugworms (Arenicola marina) from the North Sea, the English Channel and the Atlantic during winter and summer seasons. We adopted the concept of oxygen and capacity limited thermal tolerance and tested a variety of methods for their suitability to identify characters of the respective thermal window like critical, pejus (lat.: getting worse) and optimum temperatures (T_c, T_p and T_opt) as well as temperature dependent performance. First, the effect of acute temperature changes on oxygen consumption and pumping activity was examined in artificial burrows ventilated by animals collected in winter and summer from North Sea mudflats (acclimation temperatures 5°C and 10°C). Second, the window of acutely temperature dependent growth was evaluated by following the integration of uniformly labelled ¹³C-L-phenylalanine into proteins of the cuticulo-muscular tube, using NMR-spectroscopy, possibly providing access to T_p. Third, seasonal changes in haemoglobin half-saturation oxygen tension (P₅₀) and haemoglobin oxygen status in vivo were studied in lugworms from the North Sea population. T_c were defined by use of oxygen consumption measurements, whereas pumping activity, growth performance and tissue oxygenation allowed to determine T_opt. Our results show that the thermal window of actively ventilating animals is narrower in winter than in summer. The acute optimum temperature of growth performance was tilted towards the lower T_c and likely shifts with acclimation. Methods were found suitable to identify the acute thermal window of oxygen limited thermal tolerance in the lugworm. Consecutive comparison of populations during various seasons in a latitudinal cline should thus lead to a better understanding of the impacts of climate change on marine ecosystems.