Movement of pulsed resource subsidies from kelp forests to deep fjords

Resource subsidies in the form of allochthonous primary production drive secondary production in many ecosystems, often sustaining diversity and overall productivity. Despite their importance in structuring marine communities, there is little understanding of how subsidies move through juxtaposed habitats and into recipient communities. We investigated the transport of detritus from kelp forests to a deep Arctic fjord (northern Norway). We quantified the seasonal abundance and size structure of kelp detritus in shallow subtidal (0‒12 m), deep subtidal (12‒85 m), and deep fjord (400‒450 m) habitats using a combination of camera surveys, dive observations, and detritus collections over 1 year. Detritus formed dense accumulations in habitats adjacent to kelp forests, and the timing of depositions coincided with the discrete loss of whole kelp blades during spring. We tracked these blades through the deep subtidal and into the deep fjord, and showed they act as a short-term resource pulse transported over several weeks. In deep subtidal regions, detritus consisted mostly of fragments and its depth distribution was similar across seasons (50% of total observations). Tagged pieces of detritus moved slowly out of kelp forests (displaced 4‒50 m (mean 11.8 m ± 8.5 SD) in 11‒17 days, based on minimum estimates from recovered pieces), and most (75%) variability in the rate of export was related to wave exposure and substrate. Tight resource coupling between kelp forests and deep fjords indicate that changes in kelp abundance would propagate through to deep fjord ecosystems, with likely consequences for the ecosystem functioning and services they provide.acceptedVersio

IPCC reasons for concern regarding climate change risks

The reasons for concern framework communicates scientific understanding about risks in relation to varying levels of climate change. The framework, now a cornerstone of the IPCC assessments, aggregates global risks into five categories as a function of global mean temperature change. We review the framework's conceptual basis and the risk judgments made in the most recent IPCC report, confirming those judgments in most cases in the light of more recent literature and identifying their limitations. We point to extensions of the framework that offer complementary climate change metrics to global mean temperature change and better account for possible changes in social and ecological system vulnerability. Further research should systematically evaluate risks under alternative scenarios of future climatic and societal conditions

Evaluation of OD trip matrices by traffic counts in transit systems

The paper deals with the Origin/Destination (O/D) trip matrices estimation in transit systems using traffic counts. The methodology allows both the correction and improvement of the global demand level and the updating of the demand model parameters. An application is executed for the sub-regional area of Reggio Calabria (Italy), and the transit network is modelled by both frequency-based and schedule-based approaches. The results concern the estimation of the average level and the temporal distribution of the daily demand for the bus and train sub-systems, the improvement of an initial set of modal split demand parameters

Effects of pH on asexual reproduction and statolith formation of the scyphozoan, Aurelia labiata

The objectives of this research effort focused on the oxidative aging of binders with high recycled asphalt materials. A coordinated program of forced-draft oven aging experiments was conducted on eleven sorts of binder blends including three different types of base binders from TX, NH, and NV, two different types of recycled material (RAP/RAS), and two different types of recycling agents (RA). Implementing the Fourier-Transform Infrared Spectroscopy (FT-IR) and Dynamic Shear Rheometer (DSR) isothermal frequency sweep tests, the oxidation kinetics and rheological performance were determined for the evaluation materials. Results indicated that the oxidative aging rates were influenced by the aging temperature, duration, base binder type, as well as the utilized asphalt modifier, i.e. recycled materials and RAs. It was also noted that the RAs reduced the overall stiffness in the investigated stages of oxidation. However, differential aging rates and hardening susceptibilities were observed between the RA and RAP/RAS additions to each of the three bases, noting that these differences were not consistent with the type of RAS, i.e. MWAS or TOAS. Additionally, the base binder aging properties due to the addition of the recycled material was highly influenced by the RA dosages within each blend. Furthermore, the binder blend oxidative aging predictions at binder specific geographical location indicated that using the recycled materials along with the RAs at the optimum dosage, according to the proposed methodology, was able to restore the binder blend properties to the virgin binder. The influences of the recycled material and RAs on the PG 64-28P base binder were also investigated through the binder PG grading and mortar testing. Consistent directions for the influence of the evaluation materials were observed within both procedures, suggesting the capability of the mortar procedure in characterizing the effects of RAP and RA materials on virgin binder without the use of chemical extraction. The Uniaxial Thermal Stress and Strain Test (UTSST) was also conducted on the PMFC and RPMLC specimens of the NV field project to investigate the influence of the high recycled material and RAs on the asphalt mixtures. Through consideration of the thermo-viscoelastic properties, marked differences in the binder oxidation were noted between the experimental factors. Typically, decreases in the viscous response of the mixtures as well as increases in both the stiffness and brittle behavior were observed with aging and also inclusion of the recycled material. Although the addition of the RAs to the recycled mixtures indicated some extent of properties restoration, crack initiation and fracture were observed to occur in significantly warmer temperatures compared to the virgin mixture

Eco-physiological adaptation shapes the response of calcifying algae to nutrient limitation

The steady increase in global ocean temperature will most likely lead to nutrient limitation in the photic zone. This will impact the physiology of marine algae, including the globally important calcifying coccolithophores. Understanding their adaptive patterns is essential for modelling carbon production in a low-nutrient ocean. We investigated the physiology of Helicosphaera carteri, a representative of the abundant but under-investigated flagellated functional group of coccolithophores. Two strains isolated from contrasting nutrient regimes (South Atlantic and Mediterranean Sea) were grown in phosphorus-replete and phosphorus-limited batch cultures. While growing exponentially in a phosphorus-replete medium, the Mediterranean strain exhibited on average 24% lower growth rate, 36% larger coccosphere volume and 21% lower particulate inorganic carbon (PIC) production than the Atlantic strain. Under phosphorus limitation, the same strain was capable of reaching a 2.6 times higher cell density than the Atlantic strain due to lower phosphorus requirements. These results suggest that local physiological adaptation can define the performance of this species under nutrient limitation

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

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