Physical oceanography during POSEIDON cruise POS264

RV POSEIDON cruise POS264 was carried out by the Institut für Meereskunde of the University of Hamburg and staff from the Niels Bohr Instituttet for Astronomi, Fysik og Geofysik of the University of Copenhagen also participated. The cruise had several objectives: - to educate undergraduate students in the handling of oceanographic instrumentation and in the collection and analysis of field data, - to map the cold overflow through the Faroe-Bank Channel from the Norwegian Sea into the Icelandic Basin and to study its short-time variability and - to quantify the contributions of the water masses which are involved in the mixing of the overflow plume with its ambient water. The planning and preparation of the cruise involved the participating students and was carried out during seminars, both at the Universities of Hamburg and Copenhagen. Following a review of the recent literature and an analysis of historical data the observational programme was designed. Hydrographic and current profiling stations were occupied along several sections crossing the overflow. The experiment was financed by the University of Hamburg. Temperature, salinity and dissolved oxygen data from CTD stations are presented. The temperature and salinity data were quality controlled and calibrated. Oxygen data are not calibrated as no oxygen samples were taken additionally during the cruise.

Investigations on the Chilean kelp crab Taliepus dentatus

Physiological responses of larval stages can differ from those of the adults, affecting key ecological processes. Therefore, developing a mechanistic understanding of larval responses to environmental conditions is essential vis-à-vis climate change. We studied the thermal tolerance windows, defined by lower and upper pejus (Tp) and critical temperatures (Tc), of zoea I, II, and megalopa stages of the Chilean kelp crab Taliepus dentatus. Tp limits determine the temperature range where aerobic scope is maximal and functioning of the organism is unrestrained and were estimated from direct observations of larval activity. Tc limits define the transition from aerobic to anaerobic metabolism, and were estimated from the relationship between standard metabolic rate and temperature. Zoea I showed the broadest, Zoea II an intermediate, and megalopae the narrowest tolerance window (Tp). Optimum performance in megalopae was limited to Tp between 11 and 15°C, while their Tc ranged between 7 and 19°C. Although Tc may be seldom encountered by larvae, the narrower Tp temperatures can frequently expose larvae to unfavorable conditions that can drastically constrain their performance. Temperatures beyond the Tp range of megalopae have been observed in most spring and summer months in central Chile, and can have important consequences for larval swimming performance and impair their ability to avoid predators or settle successfully. Besides the well-documented effects of temperature on development time, variability in field temperatures beyond Tp can affect performance of particular larval stages, which could drive large-scale variability in recruitment and population dynamics of T. dentatus and possibly other invertebrate species.