Pteropod sedimentation at AWI HAUSGARTEN at two different sites from 2004 to 2011

Pteropods are important organisms in high-latitude ecosystems, and they are expected to severely suffer from climate change in the near future. In this study, sedimentation patterns of two pteropod species, the polar Limacina helicina and the subarctic boreal L. retroversa, are presented. Time series data received by moored sediment traps at the Long-Term Ecological Research (LTER) Observatory HAUSGARTEN in eastern Fram Strait were analyzed during the years 2008 to 2012. Results were derived from four different deployment depths (~200, 1,250, 2,400, and 2,550 m) at two different sites (79° N, 04°20' E; 79°43' N, 04°30' E). A species-specific sedimentation pattern was present at all depths and at both sites showing maximal flux rates during September/October for L. helicina and in November/December for L. retroversa. The polar L. helicina was outnumbered by L. retroversa (55-99 %) at both positions and at all depths supporting the recently observed trend toward the dominance of the subarctic boreal species. The largest decrease in pteropod abundance occurred within the mesopelagic zone (~200-1,250 m), indicating loss via microbial degradation and grazing. Pteropod carbonate (aragonite) amounted up to ~75 % of the total carbonate flux at 200 m and 2-13 % of the aragonite found in the shallow traps arrived at the deep sediment traps (~160 m above the seafloor), revealing the significance of pteropods in carbonate export at Fram Strait. Our results emphasize the relevance and the need for continuation of long-term studies to detect and trace changes in pteropod abundances and community composition and thus in the vertical transport of aragonite.

Boron isotopes, trace elements and pH calculation for Norwegian deep sea coral specimen Madrepora o. (1968-2007), 2012

d11B and trace results obtained for a deep sea coral specimen Madrepora oculata collected from the Norwegian Sea (67°N, 9°E, 340 m) during the RV Polarstern ARK/II/Ia cruise (2007). Such coral specimen grew during the last four decades (1968-2007) and geochemical results highligh a seawater pH decrease with an order of magnitude in good agreement with an ocean acidification rate today known. This pH record is strongly impacted by inter-decadal change of ocean dynamic (NAO) and productivity. pHT calculation parameters (Hönisch et al., 2007): a=5; a=0.9804, d11B=39.5 PER MIL, Li/Mg temperature, salinity=35.1, pKB from Dickson (1990).

Response of the calcifying coccolithophore Emiliania huxleyi to low pH/high pCO2: from physiology to molecular level, 2011

The emergence of ocean acidification as a significant threat to calcifying organisms in marine ecosystems creates a pressing need to understand the physiological and molecular mechanisms by which calcification is affected by environmental parameters. We report here, for the first time, changes in gene expression induced by variations in pH/pCO2 in the widespread and abundant coccolithophore Emiliania huxleyi. Batch cultures were subjected to increased partial pressure of CO2 (pCO2; i.e. decreased pH), and the changes in expression of four functional gene classes directly or indirectly related to calcification were investigated. Increased pCO2 did not affect the calcification rate and only carbonic anhydrase transcripts exhibited a significant down-regulation. Our observation that elevated pCO2 induces only limited changes in the transcription of several transporters of calcium and bicarbonate gives new significant elements to understand cellular mechanisms underlying the early response of E. huxleyi to CO2-driven ocean acidification.