Embryonic and larval development is affected by environmental conditions and maternal provisioning. Crucial environmental factors like salinity and temperature stress have unfavorable effects on growth and biomass accumulation in the early ontogeny of decapod crustaceans. Energy investment of females into offspring production may show intraspecific variability. Just recently it was shown that initial biomass of eggs and larvae of an estuarine crab varied significantly among broods of different females, playing a significant role for larval survival and development.The marine crab, Cancer pagurus, has a broad geographical distribution from north Norway to West Africa and is also abundant in the Mediterranean and is still expanding its biogeographic range northwards. This implicates a wide temperature tolerance range of the species. Due to global warming, sea surface temperature in the North Sea around the island of Helgoland rose 1.1°C since 1962. These changed conditions might especially be of severe consequences for early ontogenetic stages of invertebrates, as the larvae of C. pagurus, which in the future might more often encounter temperatures above borders of thermal tolerance. Temperature thresholds are reflected in oxygen limitation. Beyond threshold temperatures of optimum, the animal metabolism is working in the range of pejus temperatures not allowing long-term survival. If critical temperatures are exceeded, metabolism transfers to anaerobic work, where survival is restricted. Changes in the efficiency of metabolism are well reflected in the elemental composition of an organism, which can be used as a measure of metabolic stress or fitness. In the present study we give evidence of temperature driven changes in the chemical composition of C. pagurus larvae and specification of intraspecific variability. We will demonstrate the variability in fitness of offspring and female participation. Additionally we aspire an estimation of consequences of global warming on the most sensitive stage of a population of a medium geographical extension of the key species C. pagurus to assess the potential of adaptability.