38. Effects of elevated sea water pCO2 on two species of euphausiids: Meganyctiphanes norvegica and Nyctiphanes couchii. Effect on survival, moulting, growth and food uptake

Anders Mangor-Jensen (1) ,Ingegjerd Opstad (1)*, Erik Sperfeld (3), Inger Semb Johansen (1), and Padmini Dalpadado (2)

1 Institute of Marine Research, Austevoll Research Station, 5392 Storebø, Norway
2 Institute of Marine Research, PO Box 1870, 5817 Bergen, Norway

3 Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB), Alte Fischerhütte 2, 16775 Stechlin

*Corresponding author: anders.mangor-jensen@imr.no

As a consequence of increased atmospheric concentration of CO2, more CO2 will diffuse into the global water bodies and shift the pH to a less basic state. This process is believed to be a result of anthropogenic emissions and referred to as ocean acidification. How different organisms cope in higher CO2 environments have been an important issue during the last decade. Euphausiids (krill) are ecological key species low in the food chain and represent a vast biomass predated on by fish and marine mammals. Krill are calcifiers, meaning that they deposit calcium carbonate to reinforce their exoskeleton. Effects of elevated pCO2 on these mechanisms were the aim of the present investigation.

Two species of North Sea krill (or more southerly distributed in the North Atlantic), Meganyctiphanes norvegica and Nyctipanes couchii, were collected from net hauls in Bjørnefjorden south of Bergen. The krill were sorted and stocked in 50 liter tanks were injured individuals were removed over a 7 days period. At the start of the experiment individual krill were transferred into 1 litre jars each supplied with flow through of experimental water. The jars were placed partially submerged in 50 litre tanks for temperature control.

The different water qualities were produced by adding highly enriched CO2 water to mixing tanks under control of feedback pumps. Total alkalinity and pH was registered at frequent intervals during the experimental period that lasted for 6 weeks. The target values were set to [CO2] = 1000 ppm (pH 7,4) and [CO2] = 1700 ppm (pH 7,6) in addition to untreated control water (pH= 7,9 [CO2]= 430 ppm). A total number of 24 krill were used at each pCO2 regime. During the experiment moults were collected from each jar to assess growth and molting frequencies. At termination a food intake experiment on individual basis were conducted, and the krill frozen in liquid nitrogen for determination of specific enzymes believed to participate in acid/base regulation. Findings of these ongoing experiments will be presented at the symposium.