Effect of fire on Benthic Algal Assemblage structure and recolonisation in intermittent streams

Dry biofilm on rocks and other substrata forms an important drought refuge for benthic algae in intermittent streams following the cessation of flow. This dry biofilm is potentially susceptible to disturbance from bushfires, including direct burning and/or scorching and damage from radiant heat, particularly when streams are dry. Therefore, damage to dry biofilms by fire has the potential to influence algal recolonization and assemblage structure in intermittent streams following commencement of flow. The influence of fire on benthic algal assemblages and recolonization was examined in intermittent streams of the Grampians National Park, Victoria, Australia, using a field survey and manipulative field experiment. The field survey compared assemblages in two intermittent streams within a recently burnt area (within 5 months of the fire) with two intermittent streams within an unburnt area. The two burnt streams were still flowing during the fire so most biofilms were not likely to be directly exposed to flames. Considerable site-to-site and stream-to-stream variation was detected during the field survey, which may have obscured potential differences attributable to indirect effects of the fire. The manipulative field experiment occurred in two intermittent streams and consisted of five treatments chosen to replicate various characteristics of bushfires that may influence dry biofilms: dry biofilm exposed directly to fire; dry biofilm exposed to radiant heat; dry biofilm exposed to ash; and two procedural controls. After exposure to the different treatments, rocks were replaced in the streams and algae were sampled 7 days after flow commenced. Differences occurred across treatments, but treatment differences were inconsistent across the two streams. For example, direct exposure to fire reduced the abundance of recolonizing algae and altered assemblage structure in both streams, while radiant heat had an effect on assemblage structure in one stream only. The manipulative field experiment is likely to have represented the intensity of a small bushfire only. Nonetheless, significant differences across treatments were detected, so these experimental results suggest that fire can damage dry biofilms, and hence, influence algal recolonization and assemblage structure in intermittent streams.

Pathways for algal recolonisation in ephemeral streams

Our prior research showed that stream algae regrow rapidly from dry biofilm and suggested that ephemeral streams that lacked any permanent surface water showed much lower algal regrowth once streams recommenced flow. To determine whether the latter was true in a broader range of streams, we: sampled and cultured algae from a range of drought refuges in 9 streams, sampled algae from 18 streams in the week after flow recommenced and conducted a transplant experiment to identify the source of algal colonists. We found little specificity amongst algal taxa for different drought refuges and that the dry biofilm and leaf litter combined accounted for all taxa that regrew after flows recommenced. Regulation of streams with some permanent surface water is associated with increased algal regrowth from dry biofilm, not the presence of permanent surface water alone. Sources of algal recolonization may be dependent on the dominant algal composition within the stream, at a coarse taxonomic level.

Pathways for algal recolonization in seasonally-flowing streams

1. In semi-arid climates, seasonally-flowing streams provide most of the water required for human use, but knowledge of how water extraction affects ecological processes is limited. Predicted alterations in stream flows associated with the impacts of climate change further emphasize the need to understand these processes. Benthic algae are an important base for stream food webs, but we have little knowledge of how algae survive dry periods or respond to altered flow regimes.

2. We sampled 19 streams within the Grampians National Park, south-eastern Australia and included four components: a survey of different drought refuges (e.g. permanent pools, dry biofilm on stones and dry leaf packs) and associated algal taxa; a survey of algal regrowth on stones after flows recommenced to determine which refuges contributed to regrowth; reciprocal transplant experiments to determine the relative importance of algal drift and regrowth from dry biofilm in recolonization; direct measurement of algal drift to determine taxonomic composition in relation to benthic assemblage composition.

3. Algae showed little specificity for drought refuges but did depend on them; no species were found that were not present in at least one of the perennial pool, dry biofilm or leaf pack refuges. Perennial pools were most closely correlated with the composition of algal assemblages once flows resumed, but the loss or gain of perennial pools that might arise from stream regulation is unlikely to affect the composition of algal regrowth. However, regulated streams were associated with strong increases in algal density in dry biofilm, including increased densities of Cyanobacteria.

4. A model for algal recolonization in seasonally-flowing streams identified three pathways for algal recolonization (drift-dependent, dry biofilm-dependent and contributions from both), depending on whether streams are diatom-dominated or dominated by filamentous algae. The model predicted the effects of changes to stream flow regimes on benthic algal recolonization and provides a basis for hypotheses testable in streams elsewhere.

Biofuels from Australian biomass

The data comprises experimental results relating to the characterization of biomass.

Distilled technical cashew nut shell liquid (DT-CNSL) as an effective biofuel and additive to stabilize triglyceride biofuels in diesel

We report distilled technical cashew nut shell liquid (DT-CNSL) as a non-transesterified biofuel and also as an additive to convert triglycerides to biofuel, without the need for the formation of methyl esters. DT-CNSL blends of diesel obey physico-chemical parameters of diesel. DT-CNSL offers stability to blends of straight vegetable oil (SVO) and tallow oil in diesel. Fluorescence studies using charge transfer probes show that the blend of DT-CNSL, triglycerides and diesel is a uniform solution, and fluorescence behavior is similar to that of diesel. The economics for the cultivation of cashew (Anacardium occidentale), its industrial use and rich carbon sink properties indicate that DT-CNSL could complement or replace traditional biodiesel crops like Jatropha and improve income for farmers. © 2014 Elsevier Ltd.

Ultra-small algal chitosan ocular nanoparticles with iron-binding milk protein prevents the toxic effects of carbendazim pesticide

AIM: To fabricate ultra-small algal chitosan nanoparticles (US CS NPs) for efficient delivery of bovine lactoferrin (bLf) to ocular tissues through topical administration to prevent carbendazim-induced toxicity. MATERIALS & METHODS: Rat eye model was used to evaluate the in vivo biodistribution the US CS NPs and bovine eye model was used for evaluating ex vivo biodistribution. Human lens epithelial cell line (HLEB-3) model was used to evaluate the in vitro toxicity, uptake mechanism and in vitro efficacy of the synthesized bLf-US CS NPs over carbendazim-induced ocular toxicity. RESULTS: The in vivo and ex vivo biodistribution results suggest that the ultra-small CS NPs efficiently internalize into the ocular tissues within 1 h after administering topically. Ultra-small algal nanocarriers to encapsulate bioactive antioxidant bLf protein and evaluated its potential in inhibiting carbendazim-induced human lens cell apoptosis and oxidative stress. CONCLUSION: US CS NPs could be explored for their potential for delivering various ocular drugs through topical administration for other eye diseases including cataract, glaucoma and age-related macular degeneration.

Apicoplast-localized lysophosphatidic acid precursor assembly is required for bulk phospholipid synthesis in toxoplasma gondii and relies on an algal/plant-like glycerol 3-phosphate acyltransferase

Most apicomplexan parasites possess a non-photosynthetic plastid (the apicoplast), which harbors enzymes for a number of metabolic pathways, including a prokaryotic type II fatty acid synthesis (FASII) pathway. In Toxoplasma gondii, the causative agent of toxoplasmosis, the FASII pathway is essential for parasite growth and infectivity. However, little is known about the fate of fatty acids synthesized by FASII. In this study, we have investigated the function of a plant-like glycerol 3-phosphate acyltransferase (TgATS1) that localizes to the T. gondii apicoplast. Knock-down of TgATS1 resulted in significantly reduced incorporation of FASII-synthesized fatty acids into phosphatidic acid and downstream phospholipids and a severe defect in intracellular parasite replication and survival. Lipidomic analysis demonstrated that lipid precursors are made in, and exported from, the apicoplast for de novo biosynthesis of bulk phospholipids. This study reveals that the apicoplast-located FASII and ATS1, which are primarily used to generate plastid galactolipids in plants and algae, instead generate bulk phospholipids for membrane biogenesis in T. gondii.

Bioprospecting and discovery of novel micoralgal isolates with multiple product potential.

Bio prospecting of microalgal resources from diverse ecologically distinctive locations and better understanding of the physiological conditions of diverse habitats will enable us to better exploit these organisms for the production of lipid and carotenoids.The potential for coproduction of lipid and carotenoids, that may be benefical to human health have gained interest in recent decades. Methods for co-production and separating higher value compounds such as carotenoids and lipids can offset the cost of algal biofuel production, making this source more commercially viable. 

Colonisation by epibionts and meiofauna of real and mimic pneumatophores in a cool temperate mangrove habitat

The size and pace of change in meiofaunal assemblages suggest that meiofauna make excellent subjects for testing theories about how ecological communities change. A field experiment was performed in which the  abundance and composition of epibionts and meiofauna on natural,  transplanted and mimic pneumatophores were monitored over a 47 wk period. Meiofaunal density increased with growth of algal epibionts, both reaching maximum values after 24 wk, at the end of winter. At this time the assemblages from the 3 substrata were similar, although the combined abundances of meiofauna on transplants and mimics were only 28% of the average on natural pneumatophores. Meiofaunal abundance on all substrata decreased rapidly during spring as algal cover declined due to desiccation. Twenty-three species of nematode were recorded from mimics compared with 8 and 7 from transplants and pneumatophores, respectively. A temporal sequence of feeding groups occurred in the order of epigrowth feeders, deposit feeders, and omnivore/predators, with the latter 2 adding to rather than replacing earlier trophic groups. Scavengers were found only on natural pneumatophores. The turnover rates of nematode species between all census times were similar, peaking at 63%, but there was no trend in the turnover rates with time. We conclude that mimics are more suitable than transplanted pneumatophores for colonisation studies because of their greater persistence and more easily standardised surface area. Moreover, the composition of colonising assemblages on them closely resembled assemblages on natural pneumatophores at the time of peak meiofaunal abundance.

Meiofaunal recruitment to mimic pneumatophores in a cool-temperate mangrove forest: spatial context and biofilm effects

A field experiment was devised to test whether meiofauna that colonised mimic pneumatophores (artificial substrates) resembled the assemblage on adjacent live pneumatophores in three randomly chosen intertidal, estuarine sites. The experiment showed that the close proximity of particular biota on living pneumatophores did not reliably influence subsequent development of assemblages upon mimic pneumatophores within a scale of 10 m during a colonisation period of less than 20 weeks. There was some convergence of the composition of the colonising assemblage of meiofauna on mimic pneumatophores with the local assemblages in sites dominated by barnacles, or where the natural pneumatophores were free from macroscopic epibionts. However, tychopelagic meiofauna from algal epiphytes did not significantly colonise mimic pneumatophores during the 20-week trial, probably due a lack of growing algae. During the conditioning phase suspended in water at a marine site 20 km from the mangroves, mimic pneumatophores acquired an assemblage of meiofauna different from the estuarine assemblage that colonised mimics following implantation in the estuarine mudflat. Enhanced colonisation rates of mimics in suspended bags at the conditioning site may be explained by the absence of benthic macroinvertebrates, and the lack of intertidal exposure. Biofilms aged 2, 7, and 11 weeks had no consistent, different effect on the subsequent colonisation of meiofauna. We conclude that divergence of phytal-based assemblages of meiofauna depends upon the amount of coverage, as well as the type, of fouling macro-epibionts on the pneumatophores. Meiofaunal assemblages on artificial substrates after 20 weeks colonisation displayed less intrinsic patchiness than mature phytal assemblages on natural pneumatophores, and so present a potentially useful way of improving the power of biomonitoring applications using meiofauna.