Artificial acidification of a non-acidic and an acidic headwater stream in Maine, USA

Two headwater streams with low DOC and different pHs (4.5-4.8 and 5-6.5) were acidified with H2SO4 to pH 4.1 and 4.5, respectively, for 24-h periods. Neutralization of the added acid occurred by protonation of ANC (HCO3-dominated in the higher pH stream), desorption of Ca (< 15 microeq litre(-1)) and Mg (<6 microeq litre(-1)), and desorption and dissolution of AL (<250 microg litre(-1)) from the stream bed. The concentrations of dissolved organic carbon (DOC) remained constant within the experimental reaches. The concentrations of Na, K an H4SiO4 also remained constant, indicating no detectable increase in the rate of chemical weathering in the stream bed. After acid addition was stopped, concentrations of Ca, Mg and Al decreased to below background, indicating reversible ion exchange as the principal mechanism for the mobility of Ca and Mg and to a lesser extent for Al. Repeated acidifications indicated that significant regeneration of cations on the exchange surfaces of the stream substrate occurs rapidly.     

Responses of marine benthic microalgae to elevated CO2

Increasing anthropogenic CO₂ emissions to the atmosphere are causing a rise in pCO₂ concentrations in the ocean surface and lowering pH. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and profoundly affect the structure and function of benthic habitats. The effects of increasing CO₂ levels on the colonisation of artificial substrata by microalgal assemblages (periphyton) were examined across a CO₂ gradient off the volcanic island of Vulcano (NE Sicily). We show that periphyton communities altered significantly as CO₂ concentrations increased. CO₂ enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance although we did not detect any changes in cyanobacteria. SEM analysis revealed major shifts in diatom assemblage composition as CO₂ levels increased. The responses of benthic microalgae to rising anthropogenic CO₂ emissions are likely to have significant ecological ramifications for coastal systems.     

Perceptions of climate change on the Island of Providencia

Climate change-related impacts have the capacity to substantially influence Small Island Developing States (SIDS) in the Caribbean. Currently, many SIDS are engaged in large-scale vulnerability assessments that aim to identify, analyse, and inform solutions to mitigate climate change-related impacts. Many of these assessments, while useful, place little emphasis on the local stakeholders' perceptions of climate change. One such Caribbean community impacted by climate-related change is Providence Island in Colombia. Using a vulnerability assessment framework (Marshall, P.A. et al. 2010. A framework for social adaptation to climate change: sustaining tropical coastal communities and industries. Gland: IUCN Publication Services), researchers interviewed island residents (N = 23) about their perceptions of climate change, impacts on the local environment, and how the island community may adapt. All interviews were transcribed and analysed using a priori and open coding to identify patterns of and relationships between stakeholders' responses. Results indicate that local perceptions of climate change are linked to (1) environmental knowledge, (2) environmental awareness, attitudes, and beliefs, and (3) perceptions of risk. Implications for local adaptive strategies, education, communication, and suggestions for engagement at the local level are discussed.     

Levels of polycyclic aromatic hydrocarbons and dibenzothiophenes in wetland sediments and aquatic insects in the oil sands area of Northeastern Alberta, Canada

An immense volume of tailings and tailings water is accumulating in tailings ponds located on mine leases in the oil sands area of Alberta, Canada. Oil sands mining companies have proposed to use tailings- and tailings water-amended lakes and wetlands as part of their mine remediation plans. Polycyclic aromatic hydrocarbons (PAHs) are substances of concern in oil sands tailings and tailings water. In this study, we determined concentrations of PAHs in sediments, insect larvae and adult insects collected in or adjacent to three groups of wetlands: experimental wetlands to which tailings or tailings water had been purposely added, oil sands wetlands that were located on the mine leases but which had not been experimentally manipulated and reference wetlands located near the mine leases. Alkylated PAHs dominated the PAH profile in all types of samples in the three categories of wetlands. Median and maximum PAH concentrations, especially alkylated PAH concentrations, tended to be higher in sediments and insect larvae in experimental wetlands than in the other types of wetlands. Such was not the case for adult insects, which contained higher than expected levels of PAHs in the three types of ponds. Overlap in PAH concentrations in larvae among pond types suggests that any increase in PAH levels resulting from the addition of tailings and tailings water to wetlands would be modest. Biota-sediment accumulation factors were higher for alkylated PAHs than for their parent counterparts and were lower in experimental wetlands than in oil sands and reference wetlands. Research is needed to examine factors that affect the bioavailability of PAHs in oil sands tailings- or tailings water-amended wetlands.     

Visiting a Climate-Influenced National Park: The Stability of Climate Change Perceptions

Understanding perceptions of global environmental issues, such as climate change, can help inform resource management, policy development, and communication with constituents. Although a considerable amount of research documents citizens’ perceptions of climate change, few have investigated how interactions with climate-impacted parks and protected areas influence these perceptions, and consequently elements of environmental management. Using a mixed methods Instrument Development Approach, the researchers examined the stability of park visitors’ (N = 429) climate change perceptions during a daylong interaction with climate-sensitive and influenced resources at Kenai Fjords National Park in Alaska. Results indicate that global-level beliefs about climate change remained relatively stable during a park experience, but perceptions about climate change at the park-level (e.g., impacts) appeared more malleable. Findings also revealed the type of park experience (terrestrial vs. marine) can influence the degree of change in visitors’ perceptions. Implications for communication, outreach, and park management are discussed.     

A microinjection technique using a pH-sensitive dye to determine the gut pH of Calanus helgolandicus

By applying a microinjection technique previously used in cell biology, a pH-sensitive dye, 2,7-bis(2-carboxyethyl)-5,6-carboxyfluorescein) (BCECF), was injected into the gut of the copepod Calanus helgolandicus to determine pH under a range of feeding conditions. The median gut pH of the fore- and hindguts of starved individuals was 6.86 and 7.19, respectively. This was a consistently lower pH than that observed in copepods feeding on either the diatom Thalassiosira weissflogii, the dinoflagellate Prorocentrum micans, or the coccolithophorid Emiliania huxleyi (Strain 92D), all of which had a median gut pH>7.0. In all treatments, the median pH of the foregut was more acidic than the median of the hindgut, implying that the foregut is the site of acid secretion. The results, which demonstrate pH values down to 6.11, are discussed in terms of coccolith dissolution, pigment degradation and digestive enzyme activity.