PS112 - Weekly report No. 1 | 18.03.2018 – 27.03.2018

Course Antarctica - departure into the polar autumn

[04. April 2018] The expedition PS112 started in the evening of the 18th of March from Punta Arenas, Chile, with 50 scientists and technicians from 7 nations on their way into the Southern Ocean. The destination: the South Shetland Island region around Elephant and King George Island at the northern tip of the Antarctic Peninsula.

The expedition revolves around three projects, which are third-party funded:

1. POSER (POpulation Shift and Ecosystem Response – Krill vs. Salps) is financed by the Ministry of Science and Culture of Lower Saxony (MWK)

2. PEKRIS (The performance of Krill vs. Salps to withstand in a warming Southern Ocean) is financed by the Federal Ministry of Education and Research (BMBF) and

3. Works under the CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources) framework and is financed by the Federal Ministry of Nutrition and Agriculture (BMEL).

The overarching aim of all three projects is to understand the change in population dynamics of krill and salps caused by the temperature increase in the Atlantic sector of the Southern Ocean as a result of climate change, as well as the consequences for the ecosystem.

Krill and salps are the two most common phytoplankton consuming marcroplankton organisms in the Atlantic sector of the Southern Ocean. They are, however, markedly different in their life history, feeding biology, population dynamics and their trophic position in the marine Antarctic ecosystem. Whereas krill occupies a central position in the Antarctic marine trophic web, the gelatinous salps are barely consumed. A shift in abundance and distribution between krill and salps could, given their different position in the food web, result in a cascade of short- and long-term changes in the ecosystem structure and in important ecosystem functions. Long-term studies from 1920 to 2000 have shown that the krill population is decreasing and the salp population increasing, but the reasons are still not thoroughly understood.

In this context, the focus of POSER is on the consequences of abundance shift of krill and salps on the plankton communities, their diversity and the associated biochemical cycles. PEKRIS, on the other hand, deals with the ability of both organisms to adapt to increasing sea temperatures on the basis of their physiological and genetic fitness. Few studies have investigated the effect of external stressors on krill and there are hardly any such studies on salps. With these two complimentary projects, we will try to predict the consequences of ocean warming on the salp and krill populations, and what an abundance shift would mean for the marine Antarctic ecosystem. KrillBIS represents the German contribution to CCAMLR and serves to collect abundance information of krill and salps north of the Antarctic Peninsula. Furthermore, the abundance information enables us to extrapolate the data collected in the POSER project to larger scales and to quantify the consequences for the ecosystem.

Fig. 1: Impressions from the Drake passage. (Photo: Alfred-Wegener-Institut)

Fig 2: Scientific dive team during the first outing. (Photo: Alfred-Wegener-Institut)

The first two days after our departure from Punta Arenas in calm waters were marked by a burst of activity consisting of organising of lab space and unpacking the countless boxes and devices. The Drake Passage soon confirmed its fierce reputation. Force 8-9 Bft winds noticeably affected the initial industriousness (Fig 1). Admiralty Bay at King George Island was reached on Thursday the 22^nd of March. The first net hauls commenced outside the bay and the study organisms – krill and salps - were sighted for the first time. The integrative physiology group under Magnus Lucassen successfully deployed their fish traps. He will introduce his work in more detail in next week’s report. After the first promising net hauls, we dropped anchor in the evening inside Admiralty Bay to undertake the calibration of the EK 60 echosounder the next day. This device will provide us with information on krill densities in the study area for the duration of the cruise. The scientific dive team used the time during the calibration to test their equipment under ambient conditions (Fig 2). The other research groups, which will be introduced during the coming weeks, made use of the time to complete the setup of their labs and instruments.

Fig 3: Impressions of Admiralty Bay, King George Island. (Photo: Alfred-Wegener-Institut)

On the 24^th of March we left the breath-taking scenery of Admiralty Bay (Fig 3) to commence with the first five legs of the CCAMLR transect. Consistent foul weather made the ship quite lively but due to the experience of the officers and crew we successfully completed the transect. In the days ahead we will complete our process studies on krill - which were initiated during the transect - in the shelter of the South Shetland Islands. In the lee of this wind-swept area, the dive team will try to catch live salps needed for the experiments with the aid of the MASMA, a custom built, diver operated plankton pump.

There is a lot of work ahead, we are in good spirits and we are looking forward to the voyage ahead.

Greetings and best wishes from a busy ship.

Bettina Meyer