The lugworm Arenicola marina is distributed over a wide latitudinal range and exposed to highly fluctuating temperature conditions within seasonal as well as tidal cycles. Animals are specialized to adjust to ambient climate conditions as well as climate variability as evidenced from patterns of latitudinal adaptation and seasonal acclimatisation of thermal tolerance windows. These and associated temperature dependent performance optima were elaborated from in vivo measurements of protein synthesis in artificial burrows and from the quantification of digging activity in natural sediments. The respective results in fact revealed differences in location, width and height of performance curves on the temperature scale between populations from the French Atlantic coast, the German North Sea and the Russian White Sea in accordance with temperature dependent latitudinal adaptation and seasonal acclimatisation. Quantification of the organismal performance range is thus relevant in the light of global warming and climate change, because long-term exposure to temperatures beyond the respective performance window leads to, for example, restrictions of digging activity with the consequence of extended exposure to predators or restrictions of growth. Both phenomena would result in decreased local abundances and eventually in a shift in geographical distribution. This study is part of a joined research project with Münster University (Animal Physiology) within the DFG priority programme AQUASHIFT.