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Qatar and other Gulf States have a diverse range of marine vegetation that is adapted to the stressful environmental conditions of seawater. The industrial wastewater produced by oil and gas activities adds further detrimental conditions for marine aquatic photosynthetic organisms on the Qatari coastlines. Thus, these organisms experience severe stress from both seawater and industrial wastewater. This review discusses the biodiversity in seawater around Qatar, as well as remediation methods and metabolic pathways to reduce the negative impacts of heavy metals and petroleum hydrocarbons produced during these activities. The role of microorganisms that are adjacent to or associated with these aquatic marine organisms is discussed. Exudates that are released by plant roots enhance the role of microorganisms to degrade organic pollutants and immobilize heavy metals. Seaweeds may have other roles such as biosorption and nutrient uptake of extra essential elements to avoid or reduce eutrophication in marine environments. Special attention is paid to mangrove forests and their roles in remediating shores polluted by industrial wastewater. Seagrasses (Halodule uninervis, Halophila ovalis, and Thalassia hemprichii) can be used as promising candidates for phytoremediation or bioindicators for pollution status. Some genera among seaweeds that have proven efficient in accumulating the most common heavy metals found in gas activities and biodegradation of petroleum hydrocarbons are discussed.

Ochratoxin A (OTA) is a toxic fungal metabolite produced by some Aspergillus and Penicillium species. This work was designed to explore the presence of OTA and ochratoxigenic fungi in feed grains marketed in Qatar and their biological control by a bacterium (Burkholderia cepacia). Significantly higher levels of OTA were detected in mixed grains samples (144.59 ± 6.63 μg/kg), compared to the maize (25.27 ± 1.89 μg/kg) and wheat (3.37 ± 0.11 μg/kg). OTA-producing fungi (A. niger, A. ochraceus, A. westerdijkiae, A. carbonarius and P. verrucosum) were identified on the basis of their morphological features as well as through polymerase chain reaction (PCR). Putative ochratoxigenic polyketide genes in these isolates were evidenced by using primers AoOTA-L/AoOTA-R (in A. ochraceus and A. westerdijkiae), AoPks1/AoPks2 (in A. niger and A. ochraceus) and PenPks1/Penpks2 (in P. verrucosum). On synthetic media, A. westerdijkiae showed the highest OTA synthesis (5913 ± 576 μg/kg) than the closely related A. ochraceus (3520 ± 303 μg/kg), A. carbonarius (3064 ± 289 μg/kg) and P. verrucosum (3030 ± 710 μg/kg). Burkholderia cepacia cells and culture extract showed promising biological control potentials against OTA producing fungi. On the basis of these findings, it can be concluded that animal feed samples are generally contaminated with OTA-producing fungi as well as OTA, and Burkholderia cepacia CS5 exhibits promising antifungal activities.

The Arabian Gulf ranks among the world’s most arid and warm regions; the land has high salinity levels with many Sabkhas and receives little precipitation. This region holds about one-third of the world’s oil supply. Qatar is the leading gas producer worldwide, which raises many concerns about the pollution of the sea, groundwater, and soil. Thus, the Arabian Gulf area has paid particular attention to environmental studies since the environmental status of this region imposed unique biological diversity, and microbial ecology has gained special importance following the identification of promising roles of microorganisms. This review article discusses the microbial ecology at the main habitats of the State of Qatar. We discuss important principles for successful ecological restoration and future perspectives of using biological approaches to solve many problems related to health, the economy, and agriculture. There are at least five microbial communities that have been recognized at the Qatari habitats: marine environment, salt marshes and mangrove forests, the arid lands (including dune communities), wetlands (including pond communities), and Rawdahs (including the Ghaf tree communities). Although, the environmental conditions of this region are almost the same, these habitats are compared with those at other countries of the Arabian Gulf whenever necessary, as each habitat has its own peculiar characteristics. Some case studies are presented to describe the biochemical characterizations of bacterial isolates from soils and leaf surface of native plants, including halophytes and xerophytes at these habitats. These studies rarely went beyond the general identification at species levels. There is a discussion about the possible roles of microorganisms at the rhizosphere, non-rhizosphere, and phyllosphere, and using plant exudates to control microbial activity. However, modern approach (culture-independent methods) addressing these topics has opened the door for deeper investigations, and to explore the roles played by microorganisms at these habitats. These methods have already begun during the last decade as serious step to solve many environmental issues. In the future, it is very likely that microorganisms will be used to tackle many pollution issues, as well as health, agricultural, and economic problems.

Many halophytes are considered to be salt hyperaccumulators, adopting ion extrusion and inclusion mechanisms. Such plants, with high aboveground biomass, may play crucial roles in saline habitats, including soil desalination and phytoremediation of polluted soils and waters. These plants cause significant changes in some of the soil’s physical and chemical properties; and have proven efficient in removing heavy metals and metabolizing organic compounds from oil and gas activities. Halophytes in Qatar, such as Halopeplis perfoliata, Salicornia europaea, Salsola soda, and Tetraena qatarensis, are shown here to play significant roles in the phytoremediation of polluted soils and waters. Microorganisms associated with these halophytes (such as endophytic bacteria) might boost these plants to remediate saline and polluted soils. A significant number of these bacteria, such as Bacillus spp. and Pseudomonas spp., are reported here to play important roles in many sectors of life. We explore the mechanisms adopted by the endophytic bacteria to promote and support these halophytes in the desalination of saline soils and phytoremediation of polluted soils. The possible roles played by endophytes in different parts of native plants are given to elucidate the mechanisms of cooperation between these native plants and the associated microorganisms.

Forests strongly affect climate through the exchange of large amounts of atmospheric CO2 (ref. ). The main drivers of spatial variability in net ecosystem production (NEP) on a global scale are, however, poorly known. As increasing nutrient availability increases the production of biomass per unit of photosynthesis and reduces heterotrophic respiration in forests, we expected nutrients to determine carbon sequestration in forests. Our synthesis study of 92 forests in different climate zones revealed that nutrient availability indeed plays a crucial role in determining NEP and ecosystem carbon-use efficiency (CUEe; that is, the ratio of NEP to gross primary production (GPP)). Forests with high GPP exhibited high NEP only in nutrient-rich forests (CUEe = 33 ± 4%; mean ± s.e.m.). In nutrient-poor forests, a much larger proportion of GPP was released through ecosystem respiration, resulting in lower CUEe (6 ± 4%). Our finding that nutrient availability exerts a stronger control on NEP than on carbon input (GPP) conflicts with assumptions of nearly all global coupled carbon cycle-climate models, which assume that carbon inputs through photosynthesis drive biomass production and carbon sequestration. An improved global understanding of nutrient availability would therefore greatly improve carbon cycle modelling and should become a critical focus for future research. [ABSTRACT FROM AUTHOR]

Rosmarinus officinalis is a dominant shrub species of calcareous Mediterranean communities that has increased its presence in wide areas due to fire frequency increase and field abandonment. We aimed to study the capacity of adult shrubs to respond to nutrient pulses such as those produced by fires and human driven eutrophycation. In a 5 years old post-fire Mediterranean shrubland we conducted an experiment to investigate the effects of irrigation and N and P fertilisation on the growth, nutrient status and flowering effort of adult plants of the dominant shrub R. officinalis in a post-fire shrubland. The responses were monitored during the immediate 3 years after fertilisation. P fertilisation increased plant growth, produced a great increase in P aerial mineralomass and P concentration in leaf and stems and had a slight positive effect on flowering effort. Irrigation increased plant growth, but did not have significant effects on nutrient contents and flowering. The results show that adult individuals of the Mediterranean shrub R. officinalis have a notable capacity to positively respond in growth and in nutritional status to a sudden increase of the limiting nutrient, in this case P, and in a lesser extent, to an increase of water supply. These capacities may be important under the more unpredictable nutrient and water availability conditions expected for the near future; they will allow to take advantage of the pulses of higher nutrient and water availability in the middle of dry periods, thus increasing the community capacity to improve the nutrient retention in the ecosystem. [Copyright &y& Elsevier]

A response form the author for two articles including one related to effects of nutrient availability on carbon balance of global forest and another on data quality and role of nutrients in carbon-use efficiency of forest, which appeared in a previous issue is presented.

A correction to the article "Nutrient availability as the key regulator of global forest carbon balance," that was published in the April 6, 2014 issue is presented.

A correction to the article "Nutrient availability as the key regulator of global forest carbon balance" by S. Vicca, I. A. Janssens, J. Sardans and colleagues that was published in the previous issue is presented that inadvertently failed to include some texts of the acknowledgement section.

Abstract: Nutrient availability is increasing in the Mediterranean Basin due to the great number and intensity of fires and higher levels of anthropomorphic pollution. In the experiment described in this paper, we aimed to determine the effects of N and P availability and of the removal of competing vegetation on resprouter capacity, biomass, and nutrient accumulation in Erica multiflora. Plants of the resprouter species E. multiflora were clipped to 0% of aerial biomass in a post-fire Mediterranean shrubland and fertilisation experiments and removal of competing vegetation were established in a factorial design. The resprouting of clipped plants was monitored during the first year after clipping and at the end of the year, all plant resprout populations were harvested and their resprout structure, biomass and N and P content measured. N fertilisation had no significant effect on leaf biomass either at plant level or on the total aerial biomass per stump unit area; however N concentration in resprout biomass did increased. P fertilisation slightly increased resprouting vigour and had a significant effect on P content of the leaf biomass. The removal of competing vegetation increased the ratio between leaf biomass and stem biomass, the lateral expansion of resprout, the hierarchy of resprouts branching, and the P content of stems, above all when P fertilisation was applied. These results show that as a response to decreased competition E. multiflora has the capacity to modify the relative proportions of the nutrients in the aerial biomass. All these characteristics allow E. multiflora to persist in increasingly disturbed Mediterranean ecosystems and contribute to the retention of nutrients in the ecosystem during early resprouting phases. [Copyright &y& Elsevier]

Atmospheric deposition was studied through measurements of bulk deposition, throughfall and stemflow at two sites of contrasted exposure to pollution in the Montseny mountains (Northeastern Spain). To explore the contribution of local or distant sources at both sites, concentration data and precipitation amounts (log transformed) for both bulk deposition and net throughfall were fitted by linear regression. These models indicated the more important contribution of washout scavenging processes and dry deposition at the pollution exposed site. This is relevant in the context of Mediterranean holm oak forests: up to now, most of the studies have been conducted in protected remote sites and were little representative of the fluxes in forests close to industrial activity, traffic, agriculture and residential areas. [Copyright &y& Elsevier]