Size-dependent photosynthetic performance in the giant clam <Emphasis Type="Italic">Tridacna maxima</Emphasis>, a mixotrophic marine bivalve

Giant clams form a symbiosis with photosynthetic algae of the genus Symbiodinium that reside in clam mantle tissue. The allometry of symbiont photosynthetic performance was investigated as a mechanism for the increasing percentage of giant clam carbon respiratory requirements provided by symbionts as clam size increases. Chlorophyll fluorescence measurements of symbionts of the giant clam Tridacna maxima were measured during experiments conducted in September of 2009 using specimens 0.5–200 g tissue wet weight (3–25 cm long), collected from waters around southern Taiwan (N 21°36′, E 120°47′) from July to August of 2009. Light-dependent decreases in effective quantum yield (∆F/F _m′) calculated as the noontime maximum excitation pressure over PSII (Q _m), relative electron transport rates (rETR), and dark-adapted maximum quantum yield (F _v/F _m) all varied as a quadratic function of clam size. Both Q _m and rETR increased as clam size increased up to ~10–50 g then decreased as clam size increased. F _v/F _m decreased as clam size increased up to ~5–50 g then increased as clam size increased. Chlorophyll fluorescence measurements of rETR were positively correlated with gross primary production measured during chamber incubations. Overall, symbionts of mid-sized clams ~5–50 g exhibited the highest light-dependent decreases in effective photosynthetic efficiencies, the highest relative electron transport rates, and the lowest maximum photosynthetic efficiencies, and symbiont photosynthetic performance is allometric with respect to host clam size.     

Plant extract reduces tobacco smoke harmful effects on alveolar macrophage immune responses

Tobacco smoke is a major factor responsible for lung cancer and chronic obstructive pulmonary disease. Although the best solution to reduce the incidence of these diseases is to quit smoking, there are still a large number of smokers. Thus, given the immunoregulatory properties of plant extracts, their capacity to reduce tobacco smoke harmful effects on alveolar macrophage (AM) functions was investigated. AM were treated with tobacco smoke extract and parenchymata tissue extract (PTE), or mesophyll cell extract (MCE) of Spinacia oleacea. The effects of tobacco smoke extract from PTE and MCE-treated cigarette filters were also investigated. AM production of tumor necrosis factor (TNF), interleukin-10 (IL-10) and macrophage chemoattractant protein-1 (MCP-1), and AM cytotoxicity were measured. Tobacco smoke extract significantly inhibited TNF, IL-10, and MCP-1 release, and AM cytotoxicity. The addition of PTE and MCE to tobacco smoke extract abrogated the inhibition of AM mediator release. However, only MCE restored AM cytotoxicity. Interestingly, tobacco smoke extract of PTE and MCE-treated cigarette filters showed reduced effects on AM functions. Tobacco smoke extract from MCE-treated (0.25%) cigarette filters did not inhibit TNF, IL-10, and MCP-1 release in contrast to tobacco smoke extract from buffer-treated cigarette filters. AM cytotoxic activity was not inhibited by the treatment with tobacco smoke extract from MCE-treated cigarette filters. Our data suggest that the presence of plant extract in cigarette filters reduces the inhibitory effects of cigarette smoke on AM functions. Thus, MCE-treated cigarette filters may help reducing lung diseases associated with smoking.     

Putting transdisciplinarity into practice: a mixed mode procedure for stakeholder participation in natural resource management

The definition of management actions in natural resource management requires the integration of all types of knowledge involved. An appropriate approach for such a challenge is the ideal of transdisciplinarity. A transdisciplinary process can be considered “consultative” when knowledge is simply gathered and collated, or “participatory” when knowledge integration is undertaken collectively. In this paper, we present a mixed mode procedure (i.e., using interviews, questionnaires, and group discussions) that empirically demonstrates the difference between consultative and participatory transdisciplinary processes. The mixed mode procedure is used for identifying the most relevant problems occurring in the coastal system of Praia da Vitória bay, Azores, Portugal. This mixed mode procedure is likely to be useful for other studies, because the results highlight the need to promote face-to-face interaction at the earliest opportunity, and because it allows an understanding to be gained of social learning processes, the influence of power, and participant behaviour during interaction with others.     

Polychlorinated biphenyls (PCBs) in Africa: a review of environmental levels

Several studies have shown an increase in PCB sources in Africa due to leakage and wrongly disposed transformers, continuing import of e-waste from countries of the North, shipwreck, and biomass burning. Techniques used in the recycling of waste such as melting and open burning to recover precious metals make PCBs contained in waste and other semivolatile organic substances prone to volatilization, which has resulted in an increase of PCB levels in air, blood, breast milk, and fish in several regions of Africa. Consequences for workers performing these activities without adequate measures of protection could result in adverse human health effects. Recent biodegradation studies in Africa have revealed the existence of exotic bacterial strains exhibiting unique and unusual PCB metabolic capability in terms of array of congeners that can serve as carbon source and diversity of congeners attacked, marking considerable progress in the development of effective bioremediation strategies for PCB-contaminated matrices such as sediments and soils in tropical regions. Action must be taken to find and deal with the major African sources of these pollutants. The precise sources of the PCB plume should be pinned down and used to complete the pollutant inventories of African countries. These nations must then be helped to safely dispose of the potentially dangerous chemicals.     

Remediation of heavy metals and dyes from wastewater using cellulose-based adsorbents

Environmental Chemistry Letters - Heavy metals and dyes are major pollutants that pose potential threat to the health of humans and ecosystems. Various technologies are available to remediate such...