ALBERT

Description: We present a compilation of measurements of bedrock Sr, Nd and Pb isotopic composition across the North American Southwest from the published literature. These datasets allow us to identify the isotopic signature of aeolian material exported from the North American Southwest and explore the contribution of dust to the California Borderland Basins.

Description: Strontium, neodymium and lead isotopic signatures were measured on a suite of surface sediment samples from nine different playa lakes across the Mojave Desert. All sediment samples had carbonates and organic material removed before full chemical digestion prior to analysis. Ferromanganese coatings were also removed in a subset of samples, with no notable isotopic effect from an anthropogenic contribution of Pb detected.

Description: Strontium, neodymium and lead isotopic signatures were measured on sediment samples from silt mantles that drape the bedrock of Anacapa and San Clemente Islands offshore California. These silt mantles are interpreted to be aeolian in origin and were deposited in the Late Quaternary (Muhs et al. 2007). All sediment samples had carbonates, organic material, biogenic silica and Fe-Mn oxides removed before full chemical digestion prior to analysis. Size fractions analysed were 〈63 μm and 〈10 μm.

Description: Strontium, neodymium and lead isotopic signatures were measured on fluvially-derived and hemipelagic sedimentary horizons in Late Quaternary age marine sediments from Ocean Drilling Project sites 893 and 1015 in the California Borderland Basins. All samples had carbonates, organic material, biogenic silica and Fe-Mn oxides removed before full chemical digestion prior to analysis. Age estimates of samples based upon Rack and Merrill (1995), Roark et al. (2003), Romans et al. (2009), Balestra et al. (2018) and Du et al. (2018).

Description: Global change driven by anthropogenic carbon emissions is altering ecosystems at unprecedented rates, especially coral reefs, whose symbiosis with algal symbionts is particularly vulnerable to increasing ocean temperatures and altered carbonate chemistry. Here, we assess the physiological responses of three Caribbean coral (animal host + algal symbiont) species from an inshore and offshore reef environment after exposure to simulated ocean warming (28, 31°C), acidification (300–3290 μatm), and the combination of stressors for 93 days. We used multidimensional analyses to assess how a variety of coral physiological parameters respond to ocean acidification and warming. Our results demonstrate reductions in coral health in Siderastrea siderea and Porites astreoides in response to projected ocean acidification, while future warming elicited severe declines in Pseudodiploria strigosa. Offshore S. siderea fragments exhibited higher physiological plasticity than inshore counterparts, suggesting that this offshore population was more susceptible to changing conditions. There were no plasticity differences in P. strigosa and P. astreoides between natal reef environments, however, temperature evoked stronger responses in both species. Interestingly, while each species exhibited unique physiological responses to ocean acidification and warming, when data from all three species are modelled together, convergent stress responses to these conditions are observed, highlighting the overall sensitivities of tropical corals to these stressors. Our results demonstrate that while ocean warming is a severe acute stressor that will have dire consequences for coral reefs globally, chronic exposure to acidification may also impact coral physiology to a greater extent in some species than previously assumed. Further, our study identifies S. siderea and P. astreoides as potential 'winners' on future Caribbean coral reefs due to their resilience under projected global change stressors, while P. strigosa will likely be a 'loser' due to their sensitivity to thermal stress events. Together, these species-specific responses to global change we observe will likely manifest in altered Caribbean reef assemblages in the future.

Description: Using a targeted metabolomic approach we investigated the effects of low seawater pH on energy metabolism in two late copepodite stages (CIV and CV) of the keystone Arctic copepod species Calanus glacialis. Exposure to decreasing seawater pH (from 8.0 to 7.0) caused increased ATP, ADP and NAD+ and decreased AMP concentrations in stage CIV, and increased ATP and phospho-L-arginine and decreased AMP concentrations in stage CV. Metabolic pathway enrichment analysis showed enrichment of the TCA cycle and a range of amino acid metabolic pathways in both stages. Concentrations of lactate, malate, fumarate and alpha-ketoglutarate (all involved in the TCA cycle) increased in stage CIV, whereas only alpha-ketoglutarate increased in stage CV. Based on the pattern of concentration changes in glucose, pyruvate, TCA cycle metabolites, and free amino acids, we hypothesise that ocean acidification will lead to a shift in energy production from carbohydrate metabolism in the glycolysis toward amino acid metabolism in the TCA cycle and oxidative phosphorylation in stage CIV. In stage CV, concentrations of most of the analysed free fatty acids increased, suggesting in particular that ocean acidification increases the metabolism of stored wax esters in this stage. Moreover, aminoacyl-tRNA biosynthesis was enriched in both stages indicating increased enzyme production to handle low pH stress.

Description: Marine Isotope Stage (MIS) M2, 3.3 Ma, is an isolated cold stage punctuating the benthic oxygen isotope (δ¹⁸O) stratigraphy of the warm Piacenzian interval of the late Pliocene Epoch. The prominent (~0.65‰) δ¹⁸O increase that defines MIS M2 has prompted debate over the extent to which it signals an early prelude to the rhythmic extensive glaciations of the northern hemisphere that characterise the Quaternary and raised questions about the forcing mechanisms responsible. Recent work suggests that CO₂ storage in the deep Atlantic Ocean played an important role in these events but detailed reconstructions of deep ocean chemical stratification are needed to test this idea and competing hypotheses. Here we present new records of the Nd isotope composition of fish debris and δ¹³C and B/Ca ratios of benthic foraminifera from the northwest and southeast Atlantic Ocean. Our novel geochemical data show that, in contrast to major Quaternary glaciations such as MIS 2 (~21 ka) and MIS 100 (~2.52 Ma), the deep North Atlantic Ocean was weakly chemically stratified during MIS M2. We show that Southern Component Water incursion into the Atlantic Ocean was limited to the deep South Atlantic basin during MIS M2 and peaked well before (~10-15-kyr) the atmospheric CO₂ minimum. Our findings imply that the deep Atlantic Ocean was not the principle sink of CO₂ sequestered from the atmosphere during MIS M2, implicating a different CO₂ storage deep-water reservoir mechanism, presumably Southern Component Water incursion into the Pacific Ocean. Weak chemical stratification in the deep Atlantic Ocean during MIS M2 relative to MIS 100 and 2 suggests comparatively active Atlantic meridional overturning circulation. That suggestion is consistent with the warmth of the high latitude North Atlantic during MIS M2 - surface water temperatures cooled during M2 but only to Holocene values. Our findings may help to explain the paucity of evidence for extensive early glaciation of the northern hemisphere during M2 but leave open the possibility of ice sheet advance on Antarctica.

Description: Fish debris Nd isotope data and benthic foraminiferal B/Ca ratio and stable isotope data for the MIS M2, MIS 100 and the Last Glacial-Holocene from ODP Site 1267.

Description: Fish debris Nd isotope data from IODP Site U1313 for Marine Isotope Stage (MIS) M2 and MIS 100.

Description: Age and sand volcanic glass count data from IODP Site U1313 for Marine Isotope Stage (MIS) M2 and MIS 100.