Relative influences of ocean acidification and temperature on intertidal barnacle post-larvae at the northern edge of their geographic distribution

The Arctic Ocean and its associated ecosystems face numerous challenges over the coming century. Increasing atmospheric CO₂ is causing increasing warming and ice melting as well as a concomitant change in ocean chemistry (“ocean acidification”). As temperature increases it is expected that many temperate species will expand their geographic distribution northwards to follow this thermal shift; however with the addition of ocean acidification this transition may not be so straightforward. Here we investigate the potential impacts of ocean acidification and climate change on populations of an intertidal species, in this case the barnacle Semibalanus balanoides, at the northern edge of its range. Growth and development of metamorphosing post-larvae were negatively impacted at lower pH (pH 7.7) compared to the control (pH 8.1) but were not affected by elevated temperature (+4 °C). The mineral composition of the shells did not alter under any of the treatments. The combination of reduced growth and maintained mineral content suggests that there may have been a change in the energetic balance of the exposed animals. In undersaturated conditions more mineral is expected to dissolve from the shell and hence more energy would be required to maintain the mineral integrity. Any energy that would normally be invested into growth could be reallocated and hence organisms growing in lowered pH grow slower and end up smaller than individuals grown in higher pH conditions. The idea of reallocation of resources under different conditions of pH requires further investigation. However, there could be long-term implications on the fitness of these barnacles, which in turn may prevent them from successfully colonising new areas.     

Placing identity: interviews with Hong Kong Chinese immigrants in Britain and Canada

"This paper explores the ?borderline community of migration'.... The placing of migrant identities is examined in the context of Hong Kong immigrants in Britain and Canada. Changes in identity and the meaning of the multiplicity of migrant identities are explored through interview material. The tensions between the multiple facets of migrants' identities reflect the sociopolitical relationships within and between places. The resolution of these tensions is partially revealed in the hybridity and fluidity of migrants' articulation of their identities, whilst maintaining a primary identification with their culture of origin."     

Quantitative evolved gas analysis: Winchcombe in comparison with other CM2 meteorites

Two bulk Winchcombe along with six other CM2 meteorite samples were subjected to quantitative evolved gas analysis. The observed release patterns for almost all volatile species demonstrate close similarity for all the samples and especially between those for Winchcombe. This can be considered as a fingerprint for this petrological type of meteorites. We identified several gases including H₂, H₂O, O₂, CO, CO₂, and SO₂ released in different temperature ranges. The sources and mechanisms of their release were also established. Some of the gases, H₂, CO, and CO₂, are released as a result of oxidation of macromolecular organic material from oxygen derived from oxygen-bearing minerals (a part of CO₂ is also released as a result of decomposition of carbonates). The others, O₂ and H₂O, are associated with the phase transformation/decomposition of phyllosilicates and (oxy)hydrates, while a high-temperature release of SO₂ is associated mostly with the decomposition of sulfides and in few cases also with sulfates. A low-temperature release of SO₂ is due to evaporation and oxidation of elemental sulfur from the meteoritic matrix and organic material. The total concentrations of H (mostly represented by H₂O), C, and S, calculated according to calibration of the quadrupole mass spectrometer with reference gases and decomposition of solid samples (CaSO₄·2H₂O and NaHCO₃) are in reasonable agreement with those determined by independent methods. Variations in the ratio of the carbon amounts released as CO₂ and CO ( $$/C_CO) between the samples could be an indicator of their terrestrial weathering.     

Responses of humpback whales to a changing climate in the Southern Hemisphere: Priorities for research efforts

Globally, baleen whales were severely depleted by historic whaling. Recovering populations have been observed to alter their behaviour. These changes have been attributed to climate change in some cases and raise concerns over the successful recovery of baleen whale populations. Current data-driven statistical habitat and behavioural models have proven useful for addressing questions of whale distribution changes within their limitations. Given observed changes in oceanic conditions, a new approach to managing baleen whale population recovery is necessary. Model predictions of future whale movements and distributions under climate change scenarios are vital to enable adequate conservation management. This paper presents a new perspective on understanding the impacts of climate change on humpback whales, arguing the need for a system-based multidisciplinary research approach. Our approach includes coupled, mechanistic models based upon robust ecological principles, and integrates key physical, biogeochemical, biological and ecological modules to address long-term changes associated with climate change. To illustrate the need for this system-based multidisciplinary approach, we focus on Southern Hemisphere humpback whales, the recovery of which may be impacted by rapid changes in habitat conditions brought about by anthropogenic climate change.     

Relationships between sedimentary diatom assemblages and lakewater pH values in the Experimental Lakes Area

Relationships between sedimentary diatom assemblages and lakewater pH values from 36 lakes and experimentally acidified Lake 223, in the Experimental Lakes Area, were analyzed. The relationships were used to assign diatoms in the 36 lakes into pH preference groupings. Based on their regional distribution Cyclotella stelligera and Tabellaria flocculosa strain IIIp were categorized as pH indifferent, in comparison to other areas were they have been categorized as acidophilic. Two models were then applied to calculate transfer coefficients which were used to calculate diatom-inferred pH values for Lake 223. Index B and a multiple linear regression of the pH groupings yielded similar correlations (r² 0.82 and 0.84 respectively, p=0.0001). The multiple linear regression inferred a pH of 5.36 for acidified Lake 223 compared to a measured pH of 5.46.     

The formation and aqueous alteration of CM2 chondrites and their relationship to CO3 chondrites: A fresh isotopic (O,Cd, Cr,Si, Te,Ti, and Zn) perspective from the Winchcombe CM2 fall

As part of an integrated consortium study, we have undertaken O, Cd, Cr, Si, Te, Ti, and Zn whole rock isotopic measurements of the Winchcombe CM2 meteorite. δ⁶⁶Zn values determined for two Winchcombe aliquots are +0.29 ± 0.05‰ (2SD) and +0.45 ± 0.05‰ (2SD). The difference between these analyses likely reflects sample heterogeneity. Zn isotope compositions for Winchcombe show excellent agreement with published CM2 data. δ¹¹⁴Cd for a single Winchcombe aliquot is +0.29 ± 0.04‰ (2SD), which is close to a previous result for Murchison. δ¹³⁰Te values for three aliquots gave indistinguishable results, with a mean value of +0.62 ± 0.01‰ (2SD) and are essentially identical to published values for CM2s. ε⁵³Cr and ε⁵⁴Cr for Winchcombe are 0.319 ± 0.029 (2SE) and 0.775 ± 0.067 (2SE), respectively. Based on its Cr isotopic composition, Winchcombe plots close to other CM2 chondrites. ε⁵⁰Ti and ε⁴⁶Ti values for Winchcombe are 3.21 ± 0.09 (2SE) and 0.46 ± 0.08 (2SE), respectively, and are in line with recently published data for CM2s. The δ³⁰Si composition of Winchcombe is −0.50 ± 0.06‰ (2SD, n = 11) and is essentially indistinguishable from measurements obtained on other CM2 chondrites. In conformity with petrographic observations, oxygen isotope analyses of both bulk and micromilled fractions from Winchcombe clearly demonstrate that its parent body experienced extensive aqueous alteration. The style of alteration exhibited by Winchcombe is consistent with relatively closed system processes. Analysis of different fractions within Winchcombe broadly support the view that, while different lithologies within an individual CM2 meteorite can be highly variable, each meteorite is characterized by a predominant alteration type. Mixing of different lithologies within a regolith environment to form cataclastic matrix is supported by oxygen isotope analysis of micromilled fractions from Winchcombe. Previously unpublished bulk oxygen isotope data for 12 CM2 chondrites, when combined with published data, define a well-constrained regression line with a slope of 0.77. Winchcombe analyses define a more limited linear trend at the isotopically heavy, more aqueously altered, end of the slope 0.77 CM2 array. The CM2 slope 0.77 array intersects the oxygen isotope field of CO3 falls, indicating that the unaltered precursor material to the CMs was essentially identical in oxygen isotope composition to the CO3 falls. Our data are consistent with earlier suggestions that the main differences between the CO3s and CM2s reflect differing amounts of water ice that co-accreted into their respective parent bodies, being high in the case of CM2s and low in the case of CO3s. The small difference in Si isotope compositions between the CM and CO meteorites can be explained by different proportions of matrix versus refractory silicates. CMs and COs may also be indistinguishable with respect to Ti and Cr isotopes; however, further analysis is required to test this possibility. The close relationship between CO3 and CM2 chondrites revealed by our data supports the emerging view that the snow line within protoplanetary disks marks an important zone of planetesimal accretion.     

Feasibility of using near-infrared reflectance spectroscopy for the analysis of C, N, P, and diatoms in lake sediments

The present study explored whether rapid, non-destructive near-infrared reflectance spectroscopy (NIRS) could complement conventional paleolimnological and chemical analyses of sediment cores for greater efficiency and cost-effectiveness. The study used a 47-cm long freeze-core from the deepest point in Lake Arendsee, Mecklenburg Plain in northern Germany taken in 1993 to elucidate eutrophication history and to identify the pre-impact algal communities in this system. The core had been analyzed for total C, CO32-, N, P, and diatoms. Thirty-four of the 47 1-cm thick core sections were scanned by NIRS and calibrations were developed for total C, CO32-, N, P, N:P, total diatoms, and three dominant diatom species with different sedimentary profiles (Stephanodiscus binatus, Cyclotella rossii, and Fragilaria crotonensis). Total C ranged from 167-194 mg g-1 dry weight (d.w.), CO32- from 31.3-66.4 mg g-1 d. w., N from 9.9-17.4 mg g-1 d. w., and P from 0.7-6.0 mg g-1 d. w. Calibrations developed using multiple linear regression between NIR-predicted values and chemically-measured values were excellent for P (r2 > 0.99), good for C, N, and N:P (r2 > 0.93), and satisfactory for CO32-(r2 > 0.8). Calibrations for total diatoms and for individual species were highly statistically significant (r2 between 0.54 and 0.69). Although the calibrations are not useful for reliable predictions of the content of diatoms in the samples, the results indicate that NIRS detects spectral properties associated with diatoms or lake conditions when they were present, and that further work is warranted to attempt to improve the results. The study demonstrated that rapid, non-destructive, simultaneous analysis of total C, CO32-, N, P, and N:P in sediment cores is feasible.     

Submersed macrophyte effects on nutrient exchanges in riverine sediments

Submersed macrophytes are important in nutrient cycling in marine and lacustrine systems, although their in nutrient exchange in tidally-influenced riverine systems is not well studied. In the laboratory, plants significantly lowered porewater nutrient pools of riverine sediments compared with bare controls. Deep-rootedVallisneria americana lowered the porewater nutrients to a greater extent than the shallow-rootedPotamogeton pectinatus. V. americana showed significantly higher tissue nutrient content (N in roots, P in leaves) thanP. pectinatus. porewater nutrients in the river increased from spring to summer (1995) when vegetation was at its peak (for porewater PO₄-P, p<0.05). In 1996, porewater nutrients were higher during peak plant biomass in the summer than in the fall (for porewater PO₄-P, p<0.05). In the summer (1995) vegetated patches had significantly greater porewater PO₄-P than bare patches. We hypothesize that the concentrating of particulates in riverine grassbeds and subsequent microbial processing may provide an indirect source of nutrients for submersed macrophytes. In tidally-influenced riverine systems, biological mechanisms such as root uptake of nutrients and lateral oxygen release may be masked by the interaction of physical forces (i.e., tides, currents) with the structure of the grassbeds.