Investigations on seven sediment cores from the New Ireland Basin, east of Papua New Guinea

Sediment cores were recovered from the New Ireland Basin, east of Papua New Guinea, in order to investigate the late Quaternary eruptive history of the Tabar-Lihir-Tanga-Feni (TLTF) volcanic chain. Foraminifera d18O profiles were matched to the low-latitude oxygen isotope record to date the cores, which extend back to the early part of d18O Stage 9 (333 ka). Sedimentation rates decrease from >10 cm/1000 yr in cores near New Ireland to ~2 cm/1000 yr further offshore. The cores contain 36 discrete ash beds, mostly 1-8 cm thick and interpreted as either fallout or distal turbidite deposits. Most beds have compositionally homogeneous glass shard populations, indicating that they represent single volcanic events. Shards from all ash beds have the subduction-related pattern of strong enrichment in the large-ion lithophile elements relative to MORB, but three distinct compositional groups are apparent: Group A beds are shoshonitic and characterised by >1300 ppm Sr, high Ce/Yb and high Nb/Yb relative to MORB, Group B beds form a high-K series with MORB-like Nb/Yb but high Ce/Yb and well-developed negative Eu anomalies, whereas Group C beds are transitional between the low-K and medium-K series and characterised by flat chondrite-normalised REE patterns with low Nb/Yb relative to MORB. A comparison with published data from the TLTF chain, the New Britain volcanic arc and backarc including Rabaul, and Bagana on Bougainville demonstrates that only Group A beds share the distinctive phenocryst assemblage and shoshonitic geochemistry of the TLTF lavas. The crystal- and lithic-rich character of the Group A beds point to a nearby source, and their high Sr, Ce/Yb and Nb/Yb match those of Tanga and Feni lavas. A youthful stratocone on the eastern side of Babase Island in the Feni group is the most probable source. Group A beds younger than 20 ka are more fractionated than the older Group A beds, and record the progressive development of a shallow level magma chamber beneath the cone. In contrast, Group B beds represent glass-rich fallout from voluminous eruptions at Rabaul, whereas Group C beds represent distal glass-rich fallout from elsewhere along the volcanic front of the New Britain arc.

Grazing rates and body mass of Calanus finmarchicus and Calanus glacialis incubated under elevated pCO2

It is currently under debate whether organisms that regulate their acid-base status under environmental hypercapnia demand additional energy. This could impair animal fitness, but might be compensated for via increased ingestion rates when food is available. No data are yet available for dominant Calanus spp. from boreal and Arctic waters. To fill this gap, we incubated C. glacialis at 390, 1120 and 3000 µatm for 16 days with Thalassiosira weissflogii (diatom) as food source on-board RV Polarstern in Fram Strait in 2012. Every four days copepods were sub-sampled from all CO2 treatments and clearance and ingestion rates were determined. During the SOPRAN mesocosm experiment in Bergen, Norway, 2011, we weekly collected C. finmarchicus from mesocosms initially adjusted to 390 and 3000 µatm CO2 and measured grazing at low and high pCO2. In addition, copepods were deep frozen for body mass analyses. Elevated pCO2 did not directly affect grazing activities and body mass, suggesting that the copepods did not have additional energy demands for coping with acidification, neither during long-term exposure nor after immediate changes in pCO2. Shifts in seawater pH thus do not seem to challenge these copepod species.