Mesopelagic fish abundance and particle size spectrum analysis from Maria S. Merian cruise MSM26, spring 2013

One of the goals of EU BASIN is to understand variability in production across the Atlantic and the impact of this variability on higher trophic levels. One aspect of these investigations is to examine the biomes defined by Longhurst (2007). These biomes are largely based on productivity measured with remote sensing. During MSM 26, mesopelagic fish and size-spectrum data were collected to test the biome classifications of the north Atlantic. In most marine systems, the size-spectrum is a decay function with more, smaller organisms and fewer larger organisms. The intercept of the size-spectrum has been linked to overall productivity while the slope represents the "rate of decay" of this productivity (Zhou 2006, doi:10.1093/plankt/fbi119). A Laser In-Situ Scattering Transmissometer was used to collect size-spectrum data and net collections were made to capture mesopelagic fish. The relationship among the mesopelagic fish size and abundance distributions will be compared to the estimates of production from the size-spectrum data to evaluate the biomes of the stations occupied during MSM 26.

Warming and acidification experiment on early life-stage F. vesiculosus under natural fluctuation and seasonal variations (spring 2013 - 2014)

Genetic diversity of baltic F. vesiculosus is low compared to other populations which might jeopardize their potential for adaptation to climate change. Especially the early life-stage F. vesiculosus may be threaten by ocean warming and acidification. To test this, we exposed F. vesiculosus germlings to warming and acidification in the near-natural scenario in the "Kiel Outdoor Benthocosms" maintaining the natural variation of the Kiel Fjord, Germany (54°27 'N, 10°11 'W) in all seasons (spring 2013 - 2014). Warming was simulated by using a delta treatment adding 5 °C and by increasing pCO2 at 1000 µatm. Warming positively affected germlings' growth in spring and in summer but decreased non-photochemical quenching in spring and survival in summer. Acidified conditions showed much weaker effects than warming. The high genotypic variation in stress sensitivity as well as the enhanced survival at high diversity levels indicate higher potential for adaptation for genetically diverse populations. We conclude that the combination of stressors and season determines the sensitivity to environmental stress and that genetic variation is crucial for the adaptation to climate change stress.