Recently, there has been a growing concern that climate change may rapidly and extensively alter global ecosystems with unknown consequences for terrestrial and aquatic life. While considerable emphasis has been placed on terrestrial ecology consequences, aquatic environments have received relatively little attention. Limited knowledge is available on the biological effects of increments of seawater temperature and pH decrements on key ecological species, i.e., primary producers and/or organisms representative of the basis of the trophic web. In the present study, we addressed the biological effects of global warming and ocean acidification on two model organisms, the microbenthic marine ciliate Euplotes crassus and the green alga Dunaliella tertiocleta using a suite of high level ecological endpoint tests and sub-lethal stress measures. Organisms were exposed to combinations of pH and temperature (TR1: 7.9[pH], 25.5 °C and TR2: 7.8[pH], 27,0 °C) simulating two possible environmental scenarios predicted to occur in the habitats of the selected species before the end of this century. The outcomes of the present study showed that the tested scenarios did not induce a significant increment of mortality on protozoa. Under the most severe exposure conditions, sub-lethal stress indices show that pH homeostatic mechanisms have energetic costs that divert energy from essential cellular processes and functions. The marine protozoan exhibited significant impairment of the lysosomal compartment and early signs of oxidative stress under these conditions. Similarly, significant impairment of photosynthetic efficiency and an increment in lipid peroxidation were observed in the autotroph model organism held under the most extreme exposure condition tested.

How terrestrial ecosystem responds to global warming has received wide attention. Plant stoichiometry has the potential to reflect ecosystem responses to climate change, thus, investigating the variations in plant stoichiometry with temperature is important and necessary for revealing the responses of terrestrial ecosystem to global warming. Although many studies had explored the relationships between plant N, P stoichiometry and temperature, previous field investigations did not eliminate the interference of precipitation effect with these observed relationships. To minimize the effect of precipitation on leaf N, P stoichiometry, this investigation was conducted across a temperature gradient over broad geographical scale along the 400 mm isohyet, which extends about 6000 km in China. This study showed that leaf N did not vary, whereas leaf P decreased and leaf N:P ratio increased with increasing mean annual temperature (MAT). The responses of leaf N and P stoichiometry to MAT observed in this study might be general patterns; because they were almost ubiquitous across functional groups, genera and species examined, and moreover, they were independent of vegetation and soil type. It could be inferred from this study that global warming in future will have no effect on leaf N, but reduce leaf P and increase leaf N:P ratio. Stable leaf N and varied leaf P with changing MAT suggested that leaf N and P decoupled with changing temperature.

Hydrocarbons, CO, NOx, NH₃, N₂O, CO₂ and particulate matter emissions affect air quality, global warming and human health. Transport sector is an important source of these pollutants and high pollution episodes are often experienced during the cold season. However, EU vehicle emissions regulation at cold ambient temperature only addresses hydrocarbons and CO vehicular emissions. For that reason, we have studied the impact that cold ambient temperatures have on Euro 6 diesel and spark ignition (including: gasoline, ethanol flex-fuel and hybrid vehicles) vehicle emissions using the World-harmonized Light-duty Test Cycle (WLTC) at −7 °C and 23 °C. Results indicate that when facing the WLTC at 23 °C the tested vehicles present emissions below the values set for type approval of Euro 6 vehicles (still using NEDC), with the exception of NOx emissions from diesel vehicles that were 2.3–6 times higher than Euro 6 standards. However, emissions disproportionally increased when vehicles were tested at cold ambient temperature (−7 °C). High solid particle number (SPN) emissions (>1 × 10¹¹ # km⁻¹) were measured from gasoline direct injection (GDI) vehicles and gasoline port fuel injection vehicles. However, only diesel and GDI SPN emissions are currently regulated. Results show the need for a new, technology independent, procedure that enables the authorities to assess pollutant emissions from vehicles at cold ambient temperatures.Harmful pollutant emissions from spark ignition and diesel vehicles are strongly and negatively affected by cold ambient temperatures. Only hydrocarbon, CO emissions are currently regulated at cold temperature. Therefore, it is of great importance to revise current EU winter vehicle emissions regulation.

Recent climate change may be enhancing mercury fluxes to Arctic lake sediments, confounding the use of sediment cores to reconstruct histories of atmospheric deposition. Assessing the independent effects of climate warming on mercury sequestration is challenging due to temporal overlap between warming temperatures and increased long-range transport of atmospheric mercury following the Industrial Revolution. We address this challenge by examining mercury trends in short cores (the last several hundred years) from eight lakes centered on Cape Herschel (Canadian High Arctic) that span a gradient in microclimates, including two lakes that have not yet been significantly altered by climate warming due to continued ice cover. Previous research on subfossil diatoms and inferred primary production indicated the timing of limnological responses to climate warming, which, due to prevailing ice cover conditions, varied from ∼1850 to ∼1990 for lakes that have undergone changes. We show that climate warming may have enhanced mercury deposition to lake sediments in one lake (Moraine Pond), while another (West Lake) showed a strong signal of post-industrial mercury enrichment without any corresponding limnological changes associated with warming. Our results provide insights into the role of climate warming and organic carbon cycling as drivers of mercury deposition to Arctic lake sediments.

Increased plant mortality in temperate seagrass populations has been recently observed after summer heatwaves, although the underlying causes of plant death are yet unknown. The potential energetic constrains resulting from anomalous thermal events could be the reason that triggered seagrass mortality, as demonstrated for benthic invertebrates. To test this hypothesis, the carbon balance of Posidonia oceanica and Cymodocea nodosa plants from contrasting thermal environments was investigated during a simulated heatwave, by analyzing their photosynthetic performance, carbon balance (ratio photosynthesis:respiration), carbohydrates content, growth and mortality. Both species were able to overcome and recover from the thermal stress produced by the six-week exposure to temperatures 4 °C above mean summer levels, albeit plants from cold waters were more sensitive to warming than plants from warm waters as reflected by their inability to maintain their P:R ratio unaltered. The strategies through which plants tend to preserve their energetic status varied depending on the biology of the species and the thermal origin of plants. These included respiratory homeostasis (P. oceanica warm-plants), carbon diversion from growth to respiration (C. nodosa cold-plants) or storage (P. oceanica warm-plants) and changes in biomass allocation (C. nodosa warm-plants). Findings suggest an important geographic heterogeneity in the overall response of Mediterranean seagrasses to warming with potential negative impacts on the functions and services offered by seagrass meadows including among others their capacity for carbon sequestration and carbon export to adjacent ecosystems.

A tropical coastal power plant with a once-through cooling system that pumped sea water along with tiny marine phytoplankton and zooplankton for waste heat discharge recorded reduction in the population density of these organisms by 64% and 93%, respectively, at the discharge site. The depletion of organic carbon is 0.69 tons per annum with loss of 20 to 24 lakhs fish fecundity. The synergistic effect of tropical summer ambiance and waste heat discharge from the power plant considerably reduced the phytoplankton population in the coolant water discharge point during April, June, and July. This resulted in changes in the phytoplankton community structure from Bacillariophyceae > Dyanophyceae > Cyanophyceae to Bacillariophyceae > Cyanophyceae > Dyanophyceae in the Ennore creek system. A unique epibiotic assemblage of the diatoms Licmophora juergensii and Licmophora flabellata was observed on Phormidium sp., a mat-forming Cyanobacterium preharbored along the 4.5-km-long transport channel of the cooling tower blow out of the thermal power plant. These pedunculate fouling diatoms have a symbiotic association with Phormidium sp., which grows few microns high above the substrate, thus creating obstructive flow in cooling water channels of the power plant. Further, loss of fish larvae during zooplankton population reduction creates an impact on the local fishery. However, the emerging scenario of global warming predicts that the migration of fish population toward cooler regions shall further aggravate the fishery reduction near the power plant cooling operation along the tropical coasts. The marine organisms living in tropical coastal waters operated at upper limits of thermal tolerance produce a demand for the regulatory bodies in India to enforce a drop in discharge criteria for coolant water, with the pre-existing power stations permitted to discharge up to 10 °C above the ambient temperature and newer power stations permitted to discharge a maximum of 7 °C. It becomes a requisite for power stations to draw additional seawater along with the plankton. Therefore, an emerging technology of subsurface intake systems called beachwell that resolves the issue of coolant water intake without biota was advocated.

Human-induced global change is expected to amplify the disease risk for marine biota. However, the role of disease in the rapid global decline of seagrass is largely unknown. Global change may enhance seagrass susceptibility to disease through enhanced physiological stress, while simultaneously promoting pathogen development. This review outlines the characteristics of disease-forming organisms and potential impacts of global change on three groups of known seagrass pathogens: labyrinthulids, oomycetes and Phytomyxea. We propose that hypersalinity, climate warming and eutrophication pose the greatest risk for increasing frequency of disease outbreaks in seagrasses by increasing seagrass stress and lowering seagrass resilience. In some instances, global change may also promote pathogen development. However, there is currently a paucity of information on these seagrass pathosystems. We emphasise the need to expand current research to better understand the seagrass-pathogen relationships, serving to inform predicative modelling and management of seagrass disease under future global change scenarios.

Fifteen polycyclic aromatic hydrocarbons (PAHs) were detected in seawater and atmosphere of Bransfield Strait. The concentration of ∑15[PAH] in the atmosphere ranged from 3.75 to 8.53 ng m−3, and three-ring PAHs were the most abundant compounds. Dissolved ∑15[PAH] in seawater ranged from 5.42 to 34.37 ng L−1, and the level of PAHs was markedly different on each side of the strait. The air–sea gas exchange process and molecular diagnostic ratios were calculated, results showed that the environmental behavior of PAHs was net deposition along this cruise. Given the changes in global transport routes of pollutants under global warming, the role of long-range transport (LRT) may be enhanced. Taking the Antarctic as a sink of PAHs due to the LRT and net deposition, PAHs will continue to load into the seawater of this area via atmospheric deposition, which contributes to improving our understanding of the environmental behavior of PAHs.

Sexual reproduction in predominantly clonal marine plants increases recombination favoring adaptation and enhancing species resilience to environmental change. Recent studies of the seagrass Posidonia oceanica suggest that flowering intensity and frequency are correlated with warming events associated with global climate change, but these studies have been observational without direct experimental support. We used controlled experiments to test if warming can effectively trigger flowering in P. oceanica. A six-week heat wave was simulated under laboratory mesocosm conditions. Heating negatively impacted leaf growth rates, but by the end of the experiment most of the heated plants flowered, while controls plants did not. Heated and control plants were not genetically distinct and flowering intensity was significantly correlated with allelic richness and heterozygosity. This is an unprecedented finding, showing that the response of seagrasses to warming will be more plastic, more complex and potentially more resilient than previously imagined.

Global warming is emerging as one of the most critical threats to terrestrial and marine species worldwide. This study assessed the effects of simulated warming events in culture on two seagrass species, Posidonia oceanica and Cymodocea nodosa, which play a key role in coastal ecosystems of the Mediterranean Sea. Changes in fatty acids as key metabolic indicators were assessed in specimens from two geographical populations of each species adapted to different in situ temperature regimes. Total fatty acid (TFA) content and composition were compared in C. nodosa and P. oceanica from natural populations and following exposure to heat stress in culture. After heat exposure, individuals of C. nodosa and P. oceanica adapted to colder temperatures in situ accumulated significantly more TFA than controls. For both species, the proportion of polyunsaturated fatty acids (PUFA) decreased, and the percentage of saturated fatty acids (SFA) increased significantly after the heat treatment. These results highlight that populations of both species living at warmest temperatures in situ were more thermo-tolerant and exhibited a greater capacity to cope with heat stress by readjusting their lipid composition faster. Finally, exposure of seagrasses to warmer conditions may induce a decrease in PUFA/SFA ratio which could negatively affect their nutritional value and generate important consequences in the healthy state of next trophic levels.