Physical oceanography and ADCP measurements during Maria S. Merian cruise MSM15/4

After the Eastern Mediterranean Transient (EMT), which occurred in the late 1980s, the abyssal water masses of the eastern Mediterranean were dominated by water masses of Aegean origin. Data from cruises carried out in recent years now indicate that the process of deep water formation has again been reversed, with Adriatic deep water being the main source for the deep water formation. The reversal of deep water production in the Ionian Sea is a long-term process and therefore it needs to be monitored over a period of years. The characteristics which are crucial for the deep water today, how it differs from the deep water before the EMT and in which state of the reversal it resides, these are the questions which have to be investigated continuously during the coming years. The cruises which have been accomplished (such as POS298, M71/3, MSM13/2) and the current one shall fulfill this purpose.

Physical oceanography and ADCP measurements during Maria S. Merian cruise MSM13/2

Up to the end of the eighties the main source of deep water masses in the Ionian Basin was the southern Adriatic Sea. However, during the nineties a dramatic climatic change took place in the eastern Mediterranean Sea: the Eastern Mediterranean Transient (EMT). Since then, deep water has been formed by waters originating in the Aegean Sea. Expeditions carried out in this region in recent years indicate that the process of deep water formation might reverse again. To what extent this assumption applies and what characteristics the deep water in the Ionian Sea exhibit nowadays, should be determined on the cruise. The process of a re-reversal of abyssal water production in the Ionian Sea is a long-term process and must therfore be monitored for several years. Hence, this cruise is part of a series of cruises investigating this question (POS98, M71/3, MSM13/1-2, MSM15/4). The investigations were carried out by means of CTD/lADCP measurements.

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.