Freeze-Thaw Durability of Basalt Fibre Reinforced Bio-Based Unsaturated Polyester Composite.

This paper presents an experimental study of the wet freeze-thaw (FT) durability of a fibre-polymer composite produced by vacuum infusion using an innovative bio-based unsaturated polyester resin (UPR) and basalt fibres. As the benchmark, an equivalent composite produced with a conventional (oil-based) UPR was also tested. The composites were preconditioned in water immersion for 30 days at 20 °C followed by exposure to wet FT for up to 300 cycles; each FT cycle consisted of 3 h in dry freezing condition (-20 °C) and 8 h in thawing condition (23 °C) submerged in water. The composites' properties were assessed after preconditioning and after 100, 200, and 300 FT cycles, through mechanical (tensile, compressive, in-plane shear, interlaminar shear) and thermomechanical (dynamic mechanical analysis) tests. Gravimetric and scanning electron microscope analyses were also carried out. The results obtained show that the preconditioning stage, involving water immersion, caused most of the damage, with property reductions of 5% to 39% in the bio-composite, while in the oil-composite they ranged between 4% and 22%, being higher for matrix-dominated properties. On the other hand, FT alone had an insignificant effect on the degradation of material properties; after exposure to FT, property recovery was observed, specifically in matrix-dominated properties, such as interlaminar shear strength, which recovered by 12% in the bio-composite during exposure to FT. The overall performance of the bio-composite was inferior to the conventional one, especially during the preconditioning stage, and this was attributed to the hydrophilicity of some of the components of its bio-based resin.

Impacts of hypoxic events surpass those of future ocean warming and acidification.

Over the past decades, three major challenges to marine life have emerged as a consequence of anthropogenic emissions: ocean warming, acidification and oxygen loss. While most experimental research has targeted the first two stressors, the last remains comparatively neglected. Here, we implemented sequential hierarchical mixed-model meta-analyses (721 control-treatment comparisons) to compare the impacts of oxygen conditions associated with the current and continuously intensifying hypoxic events (1-3.5 O2 mg l-1) with those experimentally yielded by ocean warming (+4 °C) and acidification (-0.4 units) conditions on the basis of IPCC projections (RCP 8.5) for 2100. In contrast to warming and acidification, hypoxic events elicited consistent negative effects relative to control biological performance-survival (-33%), abundance (-65%), development (-51%), metabolism (-33%), growth (-24%) and reproduction (-39%)-across the taxonomic groups (mollusks, crustaceans and fish), ontogenetic stages and climate regions studied. Our findings call for a refocus of global change experimental studies, integrating oxygen concentration drivers as a key factor of ocean change. Given potential combined effects, multistressor designs including gradual and extreme changes are further warranted to fully disclose the future impacts of ocean oxygen loss, warming and acidification.

Physiological resilience of a temperate soft coral to ocean warming and acidification.

Atmospheric concentration of carbon dioxide (CO2) is increasing at an unprecedented rate and subsequently leading to ocean acidification. Concomitantly, ocean warming is intensifying, leading to serious and predictable biological impairments over marine biota. Reef-building corals have proven to be very vulnerable to climate change, but little is known about the resilience of non-reef-building species. In this study, we investigated the effects of ocean warming and acidification on the antioxidant enzyme activity (CAT-catalase, and GST-glutathione S-transferase), lipid peroxidation (using malondialdehyde, MDA-levels as a biomarker) and heat shock response (HSP70/HSC70 content) of the octocoral Veretillum cynomorium. After 60 days of acclimation, no mortalities were registered in all treatments. Moreover, CAT and GST activities, as well as MDA levels, did not change significantly under warming and/or acidification. Heat shock response was significantly enhanced under warming, but high CO2 did not have a significant effect. Contrasting to many of their tropical coral-reef relatives, our findings suggest that temperate shallow-living octocorals may be able to physiologically withstand future conditions of increased temperature and acidification.

Effect of tidal environment on the trophic balance of mixotrophic hexacorals using biochemical profile and photochemical performance as indicators.

Fluctuations of environmental factors in intertidal habitats can disrupt the trophic balance of mixotrophic cnidarians. We investigated the effect of tidal environments (subtidal, tidal pools and emerged areas) on fatty acid (FA) content of Zoanthus sociatus and Siderastrea stellata. Effect on photophysiology was also accessed as an autotrophy proxy. There was a general tendency of a lower percentage of zooplankton-associated FAs in colonies from emerged areas or tidal pools when compared with colonies from the subtidal environment. Moreover, tidal environment significantly affected the photophysiology of both species. Colonies from the subtidal generally showed lower values of α, ETRmax and Ek when compared with their conspecifics from tidal pools or emerged areas. However, the absence of consistent patterns in Fv/Fm and in dinoflagellate-associated FAs, suggest that these corals are well adapted to intertidal conditions. This suggests that intertidal pressures may disturb the trophic balance, mainly by affecting heterotrophy of these species.

Different ecophysiological responses of freshwater fish to warming and acidification.

Future climate change scenarios predict threatening outcomes to biodiversity. Available empirical data concerning biological response of freshwater fish to climate change remains scarce. In this study, we investigated the physiological and biochemical responses of two Iberian freshwater fish species (Squalius carolitertii and the endangered S. torgalensis), inhabiting different climatic conditions, to projected future scenarios of warming (+3°C) and acidification (ΔpH=-0.4). Herein, metabolic enzyme activities of glycolytic (citrate synthase - CS, lactate dehydrogenase - LDH) and antioxidant (glutathione S-transferase, catalase and superoxide dismutase) pathways, as well as the heat shock response (HSR) and lipid peroxidation were determined. Our results show that, under current water pH, warming causes differential interspecific changes on LDH activity, increasing and decreasing its activity in S. carolitertii and in S. torgalensis, respectively. Furthermore, the synergistic effect of warming and acidification caused an increase in LDH activity of S. torgalensis, comparing with the warming condition. As for CS activity, acidification significantly decreased its activity in S. carolitertii whereas in S. torgalensis no significant effect was observed. These results suggest that S. carolitertii is more vulnerable to climate change, possibly as the result of its evolutionary acclimatization to milder climatic condition, while S. torgalensis evolved in the warmer Mediterranean climate. However, significant changes in HSR were observed under the combined warming and acidification (S. carolitertii) or under acidification (S. torgalensis). Our results underlie the importance of conducting experimental studies and address species endpoint responses under projected climate change scenarios to improve conservation strategies, and to safeguard endangered freshwater fish.

Seagrass ecophysiological performance under ocean warming and acidification.

Seagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, Fv/Fm) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and Fv/Fm (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, ß-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming.

Sensitivity of the invasive bivalve Corbicula fluminea to candidate control chemicals: The role of dissolved oxygen conditions.

The freshwater Corbicula fluminea is a major aquatic nuisance worldwide. Current pest control methods raise cost-effectiveness and environmental concerns, which motivate research into improved mitigation approaches. In this context, the susceptibility of the clams to chemicals under reduced oxygen conditions was examined. Biocides with different mechanisms of toxicity (niclosamide, polyDADMAC, ammonium nitrate, potassium chloride and dimethoate) were tested under normoxic (>7 mg L(-1) dissolved O2) and hypoxic (<2 mg L(-1) dissolved O2) conditions. Hypoxia was observed to potentiate chemical treatment, particularly when combined with non-overwhelming doses that would produce only intermediate responses by themselves. For niclosamide, ammonium nitrate and dimethoate, clam mortality enhancements up to 400% were observed under hypoxia as compared to dosing upon normal dissolved oxygen conditions. For polyDADMAC and potassium chloride, substantially lower mortality enhancements were found. The differences in the clams' sensitivity to the chemicals under hypoxia could be linked to the expected mechanisms of action. This suggests that judicious selection of the biocide is essential if optimized combined control treatments are to be designed and provides an insight into the interference of frequent hypoxia events in the response of natural clam populations to contaminant loads.

Cuttlefish capsule: An effective shield against contaminants in the wild.

Increasing anthropogenic pressures in estuaries are responsible for the rise of contaminants in several compartments of these ecosystems. Species that benefit from the nursery services provided by estuaries are exposed to such contaminants (e.g. metals and metalloids). It is therefore relevant to understand if marine invertebrates that use these areas as spawning grounds accumulate contaminants in their tissues throughout embryogenesis. This study aimed to quantify As, Co, Cr, Cu, Mn, Ni, Se, Pb, V and Zn concentrations in both capsule and embryos of the common cuttlefish (Sepia officinalis) in Sado Estuary (Portugal). Moreover, embryos at their initial, intermediate and final stage of development were collected in sites subjected to different anthropogenic pressures. In general, the capsule accumulated higher element concentration throughout embryogenesis which indicates that the capsule acts as an effective barrier against contaminants uptake by the embryo. Although the capsule becomes thinner throughout embryogenesis, embryo's protection does not seem to be compromised at later development stages. Additionally, the higher concentrations of As, Cu, Se and Zn in the embryo in comparison to the capsule suggests important biological roles during the embryogenesis of this cephalopod mollusc.