Potential of microalgae as biopesticides to contribute to sustainable agriculture and environmental development

The loss of yields from agricultural production due to the presence of pests has been treated over the years with synthetic pesticides, but the use of these substances negatively affects the environment and presents health risks for consumers and animals. The development of agroecological systems using biopesticides represents a safe alternative that contributes to the reduction of agrochemical use and sustainable agriculture. Microalgae are able to biosynthesize a number of metabolites with potential biopesticidal action and can be considered potential biological agents for the control of harmful organisms to soils and plants. The present work aims to provide a critical perspective on the consequences of using synthetic pesticides, offering as an alternative the biopesticides obtained from microalgal biomass, which can be used together with the implementation of environmentally friendly agricultural systems.     

Differential blood counting in fish as a non-destructive biomarker of water contamination exposure

Differential white blood cell counting was performed on blood from the fish species Oreochromis niloticus and was used as an in situ indicator of the species’ exposure to contamination. Ten young fish were collected in an area influenced by the discharge of effluents and from a fish farm (control group). The fish were anesthetized and caudal puncture was used to collect the blood. Differential white blood cell counting was performed, as well as the counting of total leukocytes and thrombocytes (in 2000 cells). Physicochemical parameters of the water from both sites were analyzed. The water from the polluted area was found to have high conductivity and low levels of dissolved oxygen, factors that indicate poor environmental quality. Fish collected from the polluted site presented higher percentages of eosinophils and monocytes and fewer thrombocytes because of exposure to pollution and hypoxic conditions. The differential white blood cell count represents a suitable biomarker of environmental health and provides a tool for biomonitoring water quality.     

Consumption of Ruditapes philippinarum and Ruditapes decussatus: comparison of element accumulation and health risk

Ruditapes philippinarum, a species native from the Indo-Pacific region, was introduced in Europe at the beginning of the 1970s for culture purposes, leading to a massive decrease of the native species Ruditapes decussatus and a high increase of R. philippinarum yields in Europe. Bivalves can accumulate high amounts of metals and thus easily reach concentrations that are toxic not only to themselves but also to consumers. Since differences in the accumulation of pollutants may exist between bivalve species, different health risks may be overcome. For this reason, the level of metals in seafood raises public health concerns, and international organisations like European Food Safety Authority, United States Food and Drug Administration, and Food Standards Australia and New Zealand (FSANZ) set maximum levels (MLs), above which edible seafood cannot be marketed. In order to evaluate the risk associated with the consumption of R. philippinarum and R. decussatus, both clam species were collected in the same site in Ria de Aveiro and the concentration of eight elements determined in organisms before and after a 48-h depuration period. Results evidence that even at low contaminated areas, the MLs for some elements can easily be achieved. The concentrations of As were above the reference values for FSANZ, and the provisional tolerable weekly intake (PTWI) is exceeded for As when more than 0.5 kg of R. decussatus and 0.9 kg of R. philippinarum clam flesh is consumed, in 1 week, by an adult (70 kg). When comparing with other systems worldwide, consumers of depurated clams from this coastal system have a similar or lower risk of exceeding the PTWI for Cd, As, Pb, and Hg. The recently introduced clam, R. philippinarum, accumulates lower amounts of the most health-threatening elements (less than 71 % of Cd, 40 % of As, and 20 % of Hg) than the native R. decussatus, except for Pb. R. philippinarum also reduces more the element burden when subjected to depuration than R. decussatus. Moreover, R. philippinarum allocates a lower proportion of the accumulated elements in the soluble fraction, where they are readily available. Thus, it is safer to consume R. philippinarum than R. decussatus, except when clams come from areas heavily polluted by Pb.     

A framework for understanding climate change impacts on coral reef social–ecological systems

Corals and coral-associated species are highly vulnerable to the emerging effects of global climate change. The widespread degradation of coral reefs, which will be accelerated by climate change, jeopardizes the goods and services that tropical nations derive from reef ecosystems. However, climate change impacts to reef social–ecological systems can also be bi-directional. For example, some climate impacts, such as storms and sea level rise, can directly impact societies, with repercussions for how they interact with the environment. This study identifies the multiple impact pathways within coral reef social–ecological systems arising from four key climatic drivers: increased sea surface temperature, severe tropical storms, sea level rise and ocean acidification. We develop a novel framework for investigating climate change impacts in social–ecological systems, which helps to highlight the diverse impacts that must be considered in order to develop a more complete understanding of the impacts of climate change, as well as developing appropriate management actions to mitigate climate change impacts on coral reef and people.     

Influence of metal resistant-plant growth-promoting bacteria on the growth of Ricinus communis in soil contaminated with heavy metals

The metal resistant-plant growth-promoting bacterial (PGPB) strains PsM6 and PjM15 isolated from a serpentine soil were characterized as Pseudomonas sp. and Pseudomonas jessenii, respectively, on the basis of their morphological, physiological, biochemical characteristics and 16S rDNA sequences. Assessment of plant growth-promoting parameters revealed the intrinsic ability of the strains for the utilization of 1-aminocyclopropane-1-carboxylic acid as the sole N source, solubilization of insoluble phosphate and production of indole-3-acetic acid (IAA). Further, a pot experiment was conducted to elucidate the effects of inoculating metal resistant PGPB on the plant growth and the uptake of Ni, Cu and Zn by Ricinus communis. Inoculation of Pseudomonas sp. PsM6 or P. jessenii PjM15 increased the shoot and root biomass of R. communis grown in non-contaminated and contaminated soil. However, the maximum biomass was observed in the plants inoculated with strain PjM15. This effect can be attributed to the solubilization of phosphate and production of IAA. Inoculation of Pseudomonas sp. PsM6 and PjM15 did not greatly alter the organ metal concentrations except Zn which concentration was higher in root, stem and leaf of inoculated plants. The results of metal extraction with PGPB strains showed that PsM6 was more efficient at solubilizing Zn than PjM15, and that PjM15 was better at solubilising Ni and Cu than PsM6. Owing to its wide action spectrum, the metal resistant PGPB could serve as an effective metal sequestering and growth-promoting bioinoculant for plants in metal-stressed soil. The present study has provided a new insight into the phytoremediation of metal-contaminated soil.     

Electronic scraps--recovering of valuable materials from parallel wire cables

Every year, the number of discarded electro-electronic products is increasing. For this reason recycling is needed, to avoid wasting non-renewable natural resources. The objective of this work is to study the recycling of materials from parallel wire cable through unit operations of mineral processing. Parallel wire cables are basically composed of polymer and copper. The following unit operations were tested: grinding, size classification, dense medium separation, electrostatic separation, scrubbing, panning, and elutriation. It was observed that the operations used obtained copper and PVC concentrates with a low degree of cross contamination. It was concluded that total liberation of the materials was accomplished after grinding to less than 3 mm, using a cage mill. Separation using panning and elutriation presented the best results in terms of recovery and cross contamination.     

Mercury uptake and allocation in Juncus maritimus: implications for phytoremediation and restoration of a mercury contaminated salt marsh

Juncus maritimus is the most abundant macrophyte in Laranjo bay, a Portuguese salt marsh heavily polluted by mercury (Hg). With the aim to elucidate the role of this species in the salt marsh Hg cycling and restoration, plants were harvested between March 2006 and January 2008 from four locations differing in Hg contamination. Metal uptake and distribution between plant organs were evaluated, biomass and Hg pools were also determined. Results showed that J. maritimus may influence the sediment pH and Eh, thus increasing the Hg available for uptake. Most (95-98%) of the absorbed Hg was retained belowground, phytostabilizing the metal and reducing the amount of Hg in the sediments. These results suggest that in salt marshes dominated by J. maritimus the approach could be phytostabilization, where these plants can be used to immobilize metals and store them belowground, reducing the pool of bioavailable Hg within contaminated marshes and acting as a sink rather than a source of contamination to the surrounding areas.