| Summary: | Climate change together with anthropogenic eutrophication have led to, and will lead to, shifts in a number of abiotic factors in the oceans, such as temperature, carbon dioxide [CO2], pH, oxygen saturation and salinity. These stressors will act simultaneously on marine organisms and may have synergistic, additive or even antagonistic effects on physiological performance and tolerance. As such, multiple stressor experiments are crucial to gain a better understanding of future vulnerability of species, populations and ecosystems. Early life stages of invertebrates are generally considered most vulnerable to environmental stress, but only a few studies have concerned brooding species such as the Norway lobster (Nephrops norvegicus), which is a benthic species, of great ecological and commercial importance. The benthic stages (adults, juveniles and embryos) spend most of their time in soft sediment burrows where they may be afflicted by low pH, hypoxia and in turn an increased Mn2+ concentration while the subsequent pelagial stages (Zoea I-III) are exposed to elevated seawater temperature and fluctuations in salinity. This poses the question: Is the Norway lobster already at it tolerance limit or can it tolerate additional climate change related stress? This thesis comprises four studies primarily on embryonic development but also on larval, juveniles and eggbearing female Norway lobsters. In Paper I, a potential combined effect of long-term (4 months) exposure to ocean acidification (OA) and elevated temperature on embryonic physiology was investigated. Although the Norway lobster embryos rarely encounter the highest temperature tested (18°C) naturally, they were found to be tolerant to the treatment with no combined effects on development rate, metabolic rate or the level of oxidative stress. In Paper II an easy-to-use quantitative tool for the development staging of the Norway lobster embryos was described. Qualitative variables was fitted to the quantitative scale of amount yolk and tested against elevated ...
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