Effects of ocean acidification on different life-cycle stages of the kelp Laminaria hyperborea (Phaeophyceae), link to supplementary data

Our objective for this study was to evaluate the influence of preindustrial and expected future atmospheric CO2 concentrations (280 µatm and 700 µatm pCO2, respectively) on different life-cycle stages of the kelp Laminaria hyperborea from Helgoland (Germany, North Sea). Zoospore germination, gametogenesis, vegetative growth, sorus formation and photosynthetic performance of vegetative and fertile tissue were examined. The contribution of external carbonic anhydrase (exCA) to C-supply for net-photosynthesis (net-PS) and the Chla- and phlorotannin content were investigated. Female gametogenesis and vegetative growth of sporophytes were significantly enhanced under the expected future pCO2. rETR(max) and net-PS of young vegetative sporophytes tended to increase performance at higher pCO2. The trend towards elevated net-PS vanished after inhibition of exCA. In vegetative sporophytes, phlorotannin content and Chla content were not significantly affected by pCO2.

Clay and smectite content in sediment core CRP-3

The Cenozoic sediments of the CRP-3 drill core from the continental shelf of McMurdo Sound in Ross Sea, Pacific sector of the Southern Ocean, have been investigated for their clay mineral assemblages, especially for the smectite abundances, concentrations and crystallinities. The assemblages of CRP-3 are very different from those of the CRP-1 and CRP-2/2A drill cores. Thus, an almost monomineralic assemblage characterizes the sequence below 330 mbsf. This assemblage is made of well-crystallized smectite with probably authigenic origin between 800 mbsf and 625 mbsf. From 625 mbsf to 330 mbsf the assemblage consists of moderately crystallized smectite that, at least in part, seems to be of detrital origin and thus indicates weathering under a relatively warm and wet climate. In the interval 330-145 mbsf, smectite concentrations fluctuate between 50% and 100% and probably document alternating phases of chemical weathering under a warm and wet climate and physical weathering under a relatively cool and dry climate. Above 145 mbsf the smectite decreases dramatically to concentrations of about 20% and becomes poorly crystalline. In contrast, illite and chlorite become more abundant. Such an assemblage is typical for early Oligocene and younger sediments in McMurdo Sound and reflects physical weathering conditions under a cool climate on a glaciated Antarctic continent. Correlations of the changes in the clay mineral spectrum of CRP-3 with other cores from McMurdo Sound and from other parts of the Southern Ocean has to remain speculative at this stage, because of the poor age control.

Sedimentology and benthic foraminiferal assemblages of the late Younger Dryas and early Holocene in the Skagerrak

A high-resolution study of palaeoenvironmental changes through the late Younger Dryas and early Holocene in the Skagerrak, the eastern North Atlantic, is based on multi-proxy analyses of core MD99-2286 combined with palaeo-water depth modelling for the area. The late Younger Dryas was characterized by a cold ice-distal benthic foraminiferal fauna. After the transition to the Preboreal (c. 11 650 cal. a BP) this fauna was replaced by a Cassidulina neoteretis dominated fauna, indicating the influence of chilled Atlantic Water at the sea floor. Persisting relatively cold bottom-water conditions until c. 10 300 cal. a BP are presumably a result of an outflow of glacial meltwater from the Baltic area across south-central Sweden, which develops a strong stratification of the water column at MD99-2286. A short-term peak in the C/N ratio at c. 10 200 cal. a BP is suggested to indicate input of terrestrial material, which may represent the drainage of an ice-dammed lake in southern Norway, the Glomma event. After the last drainage route across south-central Sweden closed, c. 10 300 cal. a BP, the meltwater influence diminished, and the Skagerrak resembled a fjord with stable inflow of waters from the North Atlantic through the Norwegian Channel and a gradual increase in boreal species. Full interglacial conditions were established at the sea floor from c. 9250 cal. a BP. Subsequent warm stable conditions were interrupted by a short-term cooling around 8300-8200 cal. a BP, representing the 8.2 ka event.