Why species matter: an experimental assessment of assumptions and predictive ability of two functional-group models.

Community ecologists use functional groups based on the rarely tested assumption that within-group responses to ecological processes are similar and thus members are functionally equivalent. However, recent research suggests that functional equivalency may break down with human impacts. We tested the equivalency assumption and model predictions of responses to simulated human alterations in nutrients and large herbivores for two models of coral reef algae, the Relative Dominance Model (RDM) and the Functional Group Model (FGM). Results of both mesocosm and field experiments using assembled communities were compared to model predictions, and within- and between-group variability were assessed. Both models' predictions of group response to herbivory matched experimental outcomes, but only the RDM predicted response to nutrients. However, within-group variability was dramatic, because the RDM grouped species with opposite responses to herbivory and the FGM grouped species with unique responses to nutrients. These heterogeneous responses resulted in loss of information and masked strong interactions between herbivory and nutrients that were not included in the models. As humans continue to impact major ecological processes in ecosystems globally, we postulate that functional-group models may need to be reformulated to account for shifting baselines.

Novel materials enable a low-cost temperature-light gradient incubator for microbial studies.

We describe the construction of temperature-light gradient incubator with a novel material: a thermally-conductive graphite foam that is lightweight, chemically resistant, economically competitive with metal, and much cheaper to fabricate. We combined this material with a variable-intensity LED light array to construct a low-cost light-temperature gradient incubator, and demonstrate its use for studies of microbial growth, enrichment, and isolation.

Comparison of algae cultivation methods for bioenergy production using a combined life cycle assessment and life cycle costing approach.

Algae are an attractive energy source, but important questions still exist about the sustainability of this technology on a large scale. Two particularly important questions concern the method of cultivation and the type of algae to be used. This present study combines elements of life cycle analysis (LCA) and life cycle costing (LCC) to evaluate open pond (OP) systems and horizontal tubular photobioreactors (PBRs) for the cultivation of freshwater (FW) or brackish-to-saline water (BSW) algae. Based on the LCA, OPs have lower energy consumption and greenhouse gas emissions than PBRs; e.g., 32% less energy use for construction and operation. According to the LCC, all four systems are currently financially unattractive investments, though OPs are less so than PBRs. BSW species deliver better energy and GHG performance and higher profitability than FW species in both OPs and PBRs. Sensitivity analyses suggest that improvements in critical cultivation parameters (e.g., CO(2) utilization efficiency or algae lipid content), conversion parameters (e.g., anaerobic digestion efficiency), and market factors (e.g., costs of CO(2) and electricity, or sale prices for algae biodiesel) could alter these results.

Evalúan las probables propiedades terapéuticas de la espirulina / Assessment of the probable therapeutic properties of spirulina

La espirulina es un alga verdeazulada (cianobacteria) que ha sido consumida por los seres humanos durante cientos de años en la región Kanem de Chad y en las regiones lacustres de México. Actualmente se comercializa en todo el mundo como alimento terapéutico. Su potencial como tratamiento de varias enfermedades se encuentra en evaluación. El consumo mundial de espirulina ha clarificado tanto sus potenciales efectos adversos como sus acciones beneficiosas. En este artículo se presenta un breve resumen del uso de la espirulina en el área de la salud.

Combinatorial life cycle assessment to inform process design of industrial production of algal biodiesel.

The use of algae as a feedstock for biodiesel production is a rapidly growing industry, in the United States and globally. A life cycle assessment (LCA) is presented that compares various methods, either proposed or under development, for algal biodiesel to inform the most promising pathways for sustainable full-scale production. For this analysis, the system is divided into five distinct process steps: (1) microalgae cultivation, (2) harvesting and/or dewatering, (3) lipid extraction, (4) conversion (transesterification) into biodiesel, and (5) byproduct management. A number of technology options are considered for each process step and various technology combinations are assessed for their life cycle environmental impacts. The optimal option for each process step is selected yielding a best case scenario, comprised of a flat panel enclosed photobioreactor and direct transesterification of algal cells with supercritical methanol. For a functional unit of 10 GJ biodiesel, the best case production system yields a cumulative energy demand savings of more than 65 GJ, reduces water consumption by 585 m(3) and decreases greenhouse gas emissions by 86% compared to a base case scenario typical of early industrial practices, highlighting the importance of technological innovation in algae processing and providing guidance on promising production pathways.

Assessment of plausible bioindicators for plant performance in advanced wastewater treatment systems.

Three full-scale advanced biological systems for nitrogen removal showing different efficiencies were assessed during one year, to investigate the protist communities supported in these wastewater treatment plants (WWTP). The main goal of this research was to explore the differences of these communities from those observed in conventional activated sludge systems. The final objective was to provide background support for the proposal of bioindicators in this type of biological systems, where scarce information was available until now, since only conventional systems had been previously studied from this point of view. Results obtained indicate that, in fact, protist population density and diversity in advanced systems for N-elimination are quite different from other wastewater systems studied before. A statistical approach through multivariate analysis was developed to search for association between protist species and physical-chemical system performance, and specifically N-removal efficiencies. The original hypothesis proposing that previous indicators from conventional systems are not adequate in advanced N-removal mechanisms was proved to be correct. Efficient processes on N-removal, despite what it had been usually found in conventional systems, show important flagellate and amoeba populations and these populations tend to reduce their abundances as nitrogen removal performance decreases (moderate to low). Ciliates are however less abundant in these N-removal efficient systems. Certain groups and genera of protist such as flagellates and small amoebae are thus proposed as indicative of high performance N-removal, while in this case the appearance of certain ciliates were indicative of low performance on N- or high organic matter removal (as COD) efficiencies.

An outlook on microalgal biofuels.

Microalgae are considered one of the most promising feedstocks for biofuels. The productivity of these photosynthetic microorganisms in converting carbon dioxide into carbon-rich lipids, only a step or two away from biodiesel, greatly exceeds that of agricultural oleaginous crops, without competing for arable land. Worldwide, research and demonstration programs are being carried out to develop the technology needed to expand algal lipid production from a craft to a major industrial process. Although microalgae are not yet produced at large scale for bulk applications, recent advances-particularly in the methods of systems biology, genetic engineering, and biorefining-present opportunities to develop this process in a sustainable and economical way within the next 10 to 15 years.

A cost/effective screening method for assessing the toxicity of nutrient rich effluents to algae.

Screening whole effluent toxicity tests are cost/effective methods for detecting the presence of toxic concentrations of unknown pollutants, but the application must solve the problem associated with the effect of high and variable concentrations of nutrients in the effluent on the results of algal toxicity tests. This work proposes a cost/effective test, based on three dilution levels measured at a single point time and a discriminant model for establishing if this kind of complex samples, with difficult interpretation of dilution-response curves, should be considered toxic to algae. This procedure identified properly around 85% of the samples considered toxic by expert judgement.

Potential costs of acclimatization to a warmer climate: growth of a reef coral with heat tolerant vs. sensitive symbiont types.

One of the principle ways in which reef building corals are likely to cope with a warmer climate is by changing to more thermally tolerant endosymbiotic algae (zooxanthellae) genotypes. It is highly likely that hosting a more heat-tolerant algal genotype will be accompanied by tradeoffs in the physiology of the coral. To better understand one of these tradeoffs, growth was investigated in the Indo-Pacific reef-building coral Acropora millepora in both the laboratory and the field. In the Keppel Islands in the southern Great Barrier Reef this species naturally harbors nrDNA ITS1 thermally sensitive type C2 or thermally tolerant type D zooxanthellae of the genus Symbiodinium and can change dominant type following bleaching. We show that under controlled conditions, corals with type D symbionts grow 29% slower than those with type C2 symbionts. In the field, type D colonies grew 38% slower than C2 colonies. These results demonstrate the magnitude of trade-offs likely to be experienced by this species as they acclimatize to warmer conditions by changing to more thermally tolerant type D zooxanthellae. Irrespective of symbiont genotype, corals were affected to an even greater degree by the stress of a bleaching event which reduced growth by more than 50% for up to 18 months compared to pre-bleaching rates. The processes of symbiont change and acute thermal stress are likely to act in concert on coral growth as reefs acclimatize to more stressful warmer conditions, further compromising their regeneration capacity following climate change.

Laboratory-induced endolithic growth in calcarenites: biodeteriorating potential assessment.

This study is aimed to assess the formation of photosynthetic biofilms on and within different natural stone materials, and to analyse their biogeophysical and biogeochemical deterioration potential. This was performed by means of artificial colonisation under laboratory conditions during 3 months. Monitoring of microbial development was performed by image analysis and biofilm biomass estimation by chlorophyll extraction technique. Microscopy investigations were carried out to study relationships between microorganisms and the mineral substrata. The model applied in this work corroborated a successful survival strategy inside endolithic microhabitat, using natural phototrophic biofilm cultivation, composed by cyanobacteria and algae, which increased intrinsic porosity by active mineral dissolution. We observed the presence of mineral-like iron derivatives (e.g. maghemite) around the cells and intracellularly and the precipitation of hausmannite, suggesting manganese transformations related to the biomineralisation.

Genome streamlining and the elemental costs of growth.

Pervasive relationships between growth rate, genome size and RNA content exist. One interesting potential consequence of these interrelationships is that selection for high growth rate should be associated with small genomes and high RNA content. Here, we use phosphorus (P) and nitrogen (N) demands of growth along with nucleic acid production as the currency to explore the interrelationships between growth rate and genome size in eukaryotes. We argue that reallocation of P (and eventually N) from DNA to RNA under sustained selection for rapid growth in nutritionally limited environments can lead to genome streamlining in eukaryotes, and that this mechanism might contribute to the evolution of reduced genome size.

Integrated assessment of river health based on water quality, aquatic life and physical habitat.

The health conditions of Liao River were assessed using 25 sampling sites in April 2005, with water quality index, biotic index and physical habitat quality index. Based on the method of cluster analysis (CA) for water quality indices, it revealed that heavily polluted sites of Liao River are located at estuary and mainstream. The aquatic species surveyed were attached algae and benthic invertebrates. The result showed that the diversity and biomass of attached algae and benthic index of biotic integrity (B-IBI) were degrading as the chemical and physical quality of water bodies deteriorating. Physiochemical parameters, BOD5, COD(Cr), TN, TP, NH3-N, DO, petroleum hydrocarbon and conductivity, were statistically analyzed with principal component analysis and correlation analysis. The statistical results were incorporated into the integrated assessing water quality index, combining fecal coliform count, attached algae diversity, B-IBI and physical habitat quality score. A comprehensive integrated assessing system of river ecological health was established. Based on the systimetic assessment, the assessed sites are categorized into 9 "healthy" and "sub-healthy" sites and 8 "sub-sick" and "sick" sites.

Reduced models of algae growth.

The simulation of biological systems is often plagued by a high level of noise in the data, as well as by models containing a large number of correlated parameters. As a result, the parameters are poorly identified by the data, and the reliability of the model predictions may be questionable. Bayesian sampling methods provide an avenue for proper statistical analysis in such situations. Nevertheless, simulations should employ models that, on the one hand, are reduced as much as possible, and, on the other hand, are still able to capture the essential features of the phenomena studied. Here, in the case of algae growth modeling, we show how a systematic model reduction can be done. The simplified model is analyzed from both theoretical and statistical points of view.

Natural impacted freshwaters: in situ use of alginate immobilized algae to the assessment of algal response.

The objective of this study was to investigate the feasibility of an in situ phytotoxicity test using alginate-immobilized algae for 60 days, in the assessment of water quality in an impacted small peri-urban stream. After laboratory optimization of algae immobilization/de-immobilization processes, the performance of immobilized/de-immobilized algae was compared to the performance of free algae in terms of specific algal growth and sensitivity. This was done by comparing 72 h EC50 values obtained with zinc and the pesticides clomazone and carbofuran. The results showed a similar performance, which allow us to conclude that immobilization for 60 days do not cause any significant alteration in algae physiology. In the field, immobilized algae were exposed at different times (2, 4 and 7 days) to water samples in both disturbed and undisturbed sites. Both laboratory and field experiments indicated that alginate-immobilized algae for 60 days were sufficiently sensitive for use in the in situ assessment of water quality.

A whole sample toxicity assessment to evaluate the sub-lethal toxicity of water and sediment elutriates from a lake exposed to diffuse pollution.

The impact of diffuse pollution in aquatic systems is of great concern due to the difficult to measure and regulate it. As part of an ecological risk assessment (ERA), this study aims to use a whole sample toxicity assessment to evaluate the toxicity of water and sediment from Lake Vela, a lake that has been exposed to diffuse pollution. In this way, standard (algae: Pseudokirchneriella subcapitata; cladoceran: Daphnia magna) and local species (algae: Aphanizomenon flos-aquae; cladoceran: Daphnia longispina) were exposed to surface water, and sediment elutriates were collected seasonally from two sites at Lake Vela: one near the east bank (ES), surrounded by agricultural lands; and the other near the west bank (WS), surrounded by a forest. The results confirmed the seasonal contamination of both environmental compartments by pesticides, including organochlorine pesticides, and the presence of high concentrations of nutrients. Although both sites were contaminated, higher levels of pesticides and nutrients were detected in ES, particularly in the sediments. Bioassays showed that water samples (100% concentration) collected in summer and autumn significantly affected the growth rate of P. subcapitata, which could be attributed to the presence of pesticides. Likewise, they revealed an apparent toxicity of elutriates for P. subcapitata and for both daphnids, in summer and autumn. In fact, although pesticides were not detected in elutriates, high levels of un-ionized ammonia were recorded, which is considered highly toxic to aquatic life. By comparing the several species, P. subcapitata was revealed to be the most sensitive one, followed by the daphnids, and then by A. flos-aquae. Results obtained in this study underlined the importance of whole samples toxicity assessment for characterizing the ecological effects of complex mixtures from diffuse inputs, in the ERA processes.

Microalgae for oil: strain selection, induction of lipid synthesis and outdoor mass cultivation in a low-cost photobioreactor.

Thirty microalgal strains were screened in the laboratory for their biomass productivity and lipid content. Four strains (two marine and two freshwater), selected because robust, highly productive and with a relatively high lipid content, were cultivated under nitrogen deprivation in 0.6-L bubbled tubes. Only the two marine microalgae accumulated lipid under such conditions. One of them, the eustigmatophyte Nannochloropsis sp. F&M-M24, which attained 60% lipid content after nitrogen starvation, was grown in a 20-L Flat Alveolar Panel photobioreactor to study the influence of irradiance and nutrient (nitrogen or phosphorus) deprivation on fatty acid accumulation. Fatty acid content increased with high irradiances (up to 32.5% of dry biomass) and following both nitrogen and phosphorus deprivation (up to about 50%). To evaluate its lipid production potential under natural sunlight, the strain was grown outdoors in 110-L Green Wall Panel photobioreactors under nutrient sufficient and deficient conditions. Lipid productivity increased from 117 mg/L/day in nutrient sufficient media (with an average biomass productivity of 0.36 g/L/day and 32% lipid content) to 204 mg/L/day (with an average biomass productivity of 0.30 g/L/day and more than 60% final lipid content) in nitrogen deprived media. In a two-phase cultivation process (a nutrient sufficient phase to produce the inoculum followed by a nitrogen deprived phase to boost lipid synthesis) the oil production potential could be projected to be more than 90 kg per hectare per day. This is the first report of an increase of both lipid content and areal lipid productivity attained through nutrient deprivation in an outdoor algal culture. The experiments showed that this marine eustigmatophyte has the potential for an annual production of 20 tons of lipid per hectare in the Mediterranean climate and of more than 30 tons of lipid per hectare in sunny tropical areas.

[Lipid biofuel production with microalgae: potential and challenges]. / La production de biocarburant lipidique avec des microalgues : promesses et défis.

Microalgae can accumulate fatty acids up to 80% of their dry weight (Chisti 2007). As a consequence the yield per hectare could be higher by a factor of 30 compared to terrestrial oleaginous species. Biodiversity of microalgae is enormous. It is estimated that there are between 200 000 and several million species. Such diversity is an unexplored potential for research and industry. In comparison to terrestrial oleaginous species, microalgae have many characteristics addressing environmental problems with a drastically enhanced oil production. Microalgae are currently generating mediatic enthusiasm, and many start-ups are investing this niche. Nevertheless there are still locks to undo via upstream search, before the expected returns and costs are met and before these technologies can be developed at a large scale.

A perspective on the biotechnological potential of microalgae.

Microalgae are the untapped resource with more than 25,000 species of which only 15 are in use. In recent years, microalgal culture technology is a business oriented line owing to their different practical applications. Innovative processes and products have been introduced in microalgal biotechnology to produce vitamins, proteins, cosmetics, and health foods. For most of these applications, the market is still developing and the biotechnological use of microalgae will extend into new areas. With the development of sophisticated culture and screening techniques, microalgal biotechnology can meet the challenging demands of both the food and pharmaceutical industries. Genetic improvement should also play an important role in the future development of algal industries. Based on the preliminary research, several therapeutic benefits have been claimed for commercially produced microalgae including AIDS, cancer, and Cerebro vascular diseases. In near future, algal biomass will serve as a renewable energy source through commercial production of hydrocarbon by Botryococcus throughout the world.

Community-level assessment of the effects of the broad-spectrum antimicrobial chlorhexidine on the outcome of river microbial biofilm development.

Chlorhexidine is a common-use antibacterial agent found in a range of personal-care products. We used rotating annular reactors to cultivate river biofilms under the influence of chlorhexidine or its molar equivalent in nutrients. Studies of the degradation of [(14)C]chlorhexidine demonstrated that no mineralization of the compound occurred. During studies with 100 microg liter(-1) chlorhexidine, significant changes were observed in the protozoan and micrometazoan populations, the algal and cyanobacterial biomass, the bacterial biomass, and carbon utilization. Denaturing gradient gel electrophoresis (DGGE) in combination with statistical analyses showed that the communities developing under control and 100 microg liter(-1) chlorhexidine were significantly different. At 10 microg liter(-1) chlorhexidine, there was significantly increased algal and cyanobacterial biomass while the bacterial biomass was not significantly affected (P < 0.05). No significant effects on protozoan or metazoan grazing were detected at the 10-microg liter(-1) chlorhexidine level. Fluorescent in situ hybridization indicated a significant reduction in the abundance of betaproteobacteria and gammaproteobacteria (P < 0.05). Archaeal cell counts were significantly reduced by both chlorhexidine and nutrient treatments. DGGE and statistical analyses indicated that 10 microg liter(-1) chlorhexidine and molar equivalent nutrient treatments were significantly different from control communities. In contrast to community level observations, toxicological testing with a panel of cyanobacteria, algae, and protozoa indicated no detectable effects at 10, 50, and 100 microg liter(-1) chlorhexidine. Thus, community level assessment indicated a risk of low levels of chlorhexidine in aquatic habitats while conventional approaches did not.