Life-history, thallus ontogeny, and the effects of temperature, irradiance and salinity on growth of the edible green seaweed Gayralia spp. (Chlorophyta) from Southern Brazil

Gayralia K.L. Vinogr. is a monostromatic green alga of commercial importance in the southern Brazil, and its cultivation is being considered. This paper reports some basic aspects of the biology of this poorly known genus. Two populations of Gayralia spp., from outer and inner sectors of Paranagua Bay, showed an asexual life history with a distinct pattern of thallus ontogeny. In one population (Gayralia sp. 1), zooids developed an expanded monostromatic blade directly, while in the other (Gayralia sp. 2) zooids produced an intermediate saccate stage, before giving rise to a monostromatic blade. Thalli of the two species differ in size and in cell diameter. The effects of temperature (16-30 degrees C), irradiance (50-100 mu mol photons m(-2) s(-1)), and salinity (5-40 psu) on the growth of both populations were assessed. Plantlets of Gayralia sp. 1 from in vitro cultures showed a broader tolerance to all salinity and irradiance levels tested, with the highest growth rate (GR; mean 17% day-1) at 21.5 degrees C and 100 mu mol photons m(-2) s(-1). Plantlets of Gayralia sp. 1 collected during the winter in the field showed higher GR, ranging from 5% day(-1) to 7.5% day(-1) in salinities from 20 to 40 psu, and 2.0% day(-1) and 4.3% day(-1) for plantlets collected during the summer. Gayralia sp. 2 from the field showed highest GR at salinity of 15 psu. These results suggest distinct physiological responses of the two species, in accordance with their distribution: Gayralia sp. 2 is limited to the inner areas of the estuary, while Gayralia sp. 1 grows in outer areas, where salinity values are higher than 20 psu. These data indicate that Gayralia sp. 1 has a higher potential for aquaculture than Gayralia sp. 2 due to its larger thalli, higher GR, and wider tolerance to environmental variations.

Present status and changes of the phytoplankton community after invasion of Neosalanx taihuensis since 1982 in a deep oligotrophic plateau lake, Lake Fuxian in the subtropical China

Phytoplankton assemblages in the subtrophical oligotrophic Lake Fuxian, the second deepest lake in China, were investigated monthly from September 2002 to August 2003. A total of 113 species belonging to seven phyla were identified, among them, a filamentous green alga, Mougeotia sp., dominated almost throughout the study period and comprised most of the total phytoplankton biomass. Mougeotia sp. has made a substantial development during the past decades: it was absent in 1957, only occasionally present in 1983, increased substantially in 1993, and became predominant in 2002-2003. It is likely that natural invasion of the Taihu Lake noodlefish (Neosalanx taihuensis) has led to a change of dominant herbivorous zooplankton from small to large calanoid, which has increased grazing pressure on small edible algae, and thus has indirectly favored the development of the inedible filamentous Mougeotia sp.

The effects of fresh and decomposed Microcystis aeruginosa on cladocerans from a subtropic Chinese Lake

We studied in the laboratory the population growth rates of four cladocerans fed both with decomposed Microcystis aeruginosa and with a mixture of fresh colonial M. aeruginosa and Scenedesmus obliquus. The neonates of Diqphanosoma brachyurum and Daphnia carinata were able to develop into adults when they were fed with <64mum decomposed M. aeruginosa, while those of Moina micrura could not use decomposed M. aeruginosa. The population growth rate of the largest species, D. carinata, was less affected by the presence of fresh colonial M. aeruginosa than the other three species. D. carinata obtained the highest growth rate at a biomass level of 10 mg L-1 fresh colonial M. aeruginosa, indicating that, to some extent, it can use colonial M. aeruginosa at a size range of 64-112mum. The population growth rate of M. micrura was negatively correlated with fresh colonial M. aeruginosa within a range of 10-100 mg L-1. The population growth rates of D. brachyurum and Ceriodaphnia cornuta were remarkably decreased by fresh colonial M. aeruginosa, although no significant difference was found within the M. aeruginosa biomass range of 10-100 mg L-1 for either cladoceran. At a biomass level of 50 mg L-1 M. aeruginosa, the population growth rates of the four cladocerans positively correlated with S. obliquus biomass within a range of 0.1-5.0 mg L-1. Our results indicate that the zooplankton community under bloom condition is shaped by the quantity of both M. aeruginosa and other edible algae.

Changes in the structure of a zooplankton community during a Ceratium (dinoflagellate) bloom in a eutrophic fishless pond

The community structure of zooplankton was studied in a eutrophic, fishless Japanese pond. The ecosystem was dominated by a dinoflagellate, Ceratium hirundinella, two filter-feeding cladocerans, Daphnia rosea and Ceriodaphnia reticulata, and an invertebrate predator, the dipteran Chaoborus flavicans. The midsummer zooplankton community showed a large change in species composition (the Daphnia population crashed) when a heavy Ceratium bloom occurred. It is shown that (i) the rapid density decline of D.rosea in mid-May was mainly caused by a shortage of edible phytoplankton, which was facilitated by the rapid increase in C.hirundinella abundance; (ii) the low density of D.rosea in June-July was considered to be mainly caused by the blooming of Ceratium hirundinella (which may inhibit the feeding process of D.rosea), while predation by C.flavicans larvae, the changing temperature, the interspecific competition and the scarcity of edible algae were not judged to be important; (iii) the high summer biomass of the planktonic C.flavicans larvae was maintained by the bloom of C.hirundinella, because >90% of the crop contents of C.flavicans larvae were C.hirundinella during this period. The present study indicates that the large-sized cells or colonies of phytoplankton are not only inedible by most cladocerans, but the selective effect of the blooming of these algae can also influence the composition and dominance of the zooplankton community, especially for the filter-feeding Cladocera, in a similar way as the selective predation by planktivorous fish. The large-sized phytoplankton can also be an important alternative food for ominivorous invertebrate predators such as Chaoborus larvae, and thus may affect the interactions between these predators and their zooplanktonic prey. In this way, such phytoplankton may play a very important role in regulating the dynamics of the aquatic food web, and become a driving force in shaping the community structure of zooplankton.

Growth rate differences between four Chilean populations of edible seaweed Chondracanthus chamissoi (Rhodophyta, Gigartinales)

The effects of temperature, photon flux density and photoperiod on the growth rate of female gametophytic and tetrasporophytic thalli of Chondracanthus chamissoi from four populations along the Chilean coast were studied in vitro. Both reproductive phases survived and grew under all the conditions tested, with growth rates varying between 0.1 and 7.5% day(-1). The results showed higher growth rates with increases in temperature and photon flux density levels. The growth rate was higher in female gametophytic thalli in almost all treatments. The photoperiod did not cause significant differences in the growth rate for either reproductive phases in any of the populations studied. Temperature was the principal factor affecting the growth rate of C. chamissoi.

On reproduction in red algae: futher research needed at the molecular level

[EN]Multicellular red algae (Rhodophyta) have some of the most complex life cycles known in living organisms. Economically valuable seaweeds, such as phycocolloid producers, have a triphasic (gametophyte, carposporophyte, and tetrasporophyte) life cycle, not to mention the intricate alternation of generations in the edible “sushi-alga” nori. It is a well-known fact that reproductive processes are controlled by one or more abiotic factor(s), including day length, light quality, temperature, and nutrients. Likewise, endogenous chemical factors such as plant growth regulators have been reported to affect reproductive events in some red seaweeds. Still, in the genomic era and given the high throughput techniques at our disposal, our knowledge about the endogenous molecular machinery lags far behind that of higher plants.

Arsenic speciation in edible alga samples by microwave-assisted extraction and high performance liquid chromatography coupled to atomic fluorescence spectrometry

Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9 Sargassum fulvellum were analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126 μg g−1. Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography–ultraviolet photo-oxidation–hydride generation atomic–fluorescence spectrometry (HPLC–(UV)–HG–AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22 μg g−1, whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2 μg g−1). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9 μg g−1) and generally high arsenate (As(V)) concentrations (up to 77 μg g−1) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products.

Influence of fatty acid structure on fuel properties of algae derived biodiesel

Physical and chemical properties of biofuel are influenced by structural features of fatty acid such as chain length, degree of unsaturation and branching of the chain. A simple and reliable calculation method to estimate fuel property is therefore needed to avoid experimental testing which is difficult, costly and time consuming. Typically in commercial biodiesel production such testing is done for every batch of fuel produced. In this study 9 different algae species were selected that were likely to be suitable for subtropical climates. The fatty acid methyl esters (FAMEs) of all algae species were analysed and the fuel properties like cetane number (CN), cold filter plugging point (CFPP), kinematic viscosity (KV), density and higher heating value (HHV) were determined. The relation of each fatty acid with particular fuel property is analysed using multivariate and multi-criteria decision method (MCDM) software. They showed that some fatty acids have major influences on the fuel properties whereas others have minimal influence. Based on the fuel properties and amounts of lipid content rank order is drawn by PROMETHEE-GAIA which helped to select the best algae species for biodiesel production in subtropical climates. Three species had fatty acid profiles that gave the best fuel properties although only one of these (Nannochloropsis oculata) is considered the best choice because of its higher lipid content.

Biodiesel production from non-edible beauty leaf (Calophyllum Inophyllum) oil : process optimization using response surface methodology (RSM)

In recent years, the beauty leaf plant (Calophyllum Inophyllum) is being considered as a potential 2nd generation biodiesel source due to high seed oil content, high fruit production rate, simple cultivation and ability to grow in a wide range of climate conditions. However, however, due to the high free fatty acid (FFA) content in this oil, the potential of this biodiesel feedstock is still unrealized, and little research has been undertaken on it. In this study, transesterification of beauty leaf oil to produce biodiesel has been investigated. A two-step biodiesel conversion method consisting of acid catalysed pre-esterification and alkali catalysed transesterification has been utilized. The three main factors that drive the biodiesel (fatty acid methyl ester (FAME)) conversion from vegetable oil (triglycerides) were studied using response surface methodology (RSM) based on a Box-Behnken experimental design. The factors considered in this study were catalyst concentration, methanol to oil molar ratio and reaction temperature. Linear and full quadratic regression models were developed to predict FFA and FAME concentration and to optimize the reaction conditions. The significance of these factors and their interaction in both stages was determined using analysis of variance (ANOVA). The reaction conditions for the largest reduction in FFA concentration for acid catalysed pre-esterification was 30:1 methanol to oil molar ratio, 10% (w/w) sulfuric acid catalyst loading and 75 °C reaction temperature. In the alkali catalysed transesterification process 7.5:1 methanol to oil molar ratio, 1% (w/w) sodium methoxide catalyst loading and 55 °C reaction temperature were found to result in the highest FAME conversion. The good agreement between model outputs and experimental results demonstrated that this methodology may be useful for industrial process optimization for biodiesel production from beauty leaf oil and possibly other industrial processes as well.

Impacts of introduced aquaculture species on markets for native marine aquaculture products : the case of edible oysters in Australia

Economic competition between introduced and native aquaculture species is of interest for industry stakeholders since increased production can affect price formation if both aquaculture species are part of the same market or even substitutes. In this study, we focus on the Australian edible oyster industry, which is dominated by two major species—the native Sydney rock oyster (grown mainly in Queensland and New South Wales) and the non-native Pacific oyster (grown mainly in South Australia and Tasmania). We examine the integration of the Australian oyster market to determine if there exists a single or several markets. Short- and long-run own, cross-price and income flexibilities of demand are estimated for both species using an inverse demand system of equations. The results suggest that the markets for the two species are integrated. We found evidence that the development of the Pacific oyster industry has had an adverse impact on Sydney rock oyster prices. However, our results show that both species are not perfect substitutes. Demand for Sydney rock oysters is relatively inelastic in the long run, yet no long-run relationships can be identified for Pacific oysters, reflecting the developing nature of this sector.

Nearness and revealing : The edible veil of the sensible being.

Taking cues from the fragility and grace enfolded within Asian cuisine, this paper explores recent experimentation of an edible rice paper veil. The veil fashions a 'secondary skin', what Jeffery Schnapp the author of 'The Fabric of Modern Times', calls an "object for prosthetic shelf extension...bearing a uniquely intimate and direct relation to the human body" (Schnapp, 1997:197). The process reveals a layered material mutable to moisture and humidity, changing its elastic state in relation to body and surroundings. The moving, breathing, sweating surface of the body further modifies both veil and bodily experience drawing forth deeper emotional responses. The implications here offer a reciprocal affect, a revealing, where new materiality evokes the threshold to a new sensible being, one aware of the depth of material consciousness and inter-corporeal engagement, and which extends the relations between thinking and being of Heidegger and Shklovsky's seminal works.

Edible materials in design fabrication

Current practice based research explores the organic properties of edible materials such as rice-paper to contemplate possible material usage from garment manufacture, landscape interventions and temporary architectural canopies/facades. Research outcomes have been published through The International Conference on Designing Food and Designing for Food, London 2012, and in Burke, Anthony + Reinmuth, Gerard (Eds.) (2012) 'Formations: New Practices in Australian Architecture.' Australian Pavilion 13th International Architecture Exhibition la biennale di Venezia.

Dewatering of microalgal cultures : a major bottleneck to algae-based fuels

Microalgae dewatering is a major obstruction to industrial-scale processing of microalgae for biofuel prodn. The dil. nature of harvested microalgal cultures creates a huge operational cost during dewatering, thereby, rendering algae-based fuels less economically attractive. Currently there is no superior method of dewatering microalgae. A technique that may result in a greater algal biomass may have drawbacks such as a high capital cost or high energy consumption. The choice of which harvesting technique to apply will depend on the species of microalgae and the final product desired. Algal properties such as a large cell size and the capability of the microalgae to autoflocculate can simplify the dewatering process. This article reviews and addresses the various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies.

Spirulina (Spirulina platensis) algae supplementation increases microbial protein production and feed intake and decreases retention time of digesta in the rumen of cattle

Cattle consuming pastures low in protein have low liveweight gain due to low rumen degradable protein (RDP) supply and thus low microbial crude protein (MCP) production and efficiency of MCP production [EMCP, g MCP/kg digestible organic matter (DOM)]. Nitrogen supplements can increase MCP production and EMCP of cattle grazing low protein pastures. The objective of this study was to compare the effects of supplementation with a non-protein-N source (NPN), in this case urea and ammonium sulfate (US), with a single-cell algal protein source (Spirulina platensis), on intake, microbial protein supply and digestibility in cattle. Nine cannulated Bos indicus steers [initial liveweight 250.1 ± 10.86 (s.d.) kg] were fed Mitchell grass hay (Astrebla spp; 6.1 g N, 746 g NDF/kg DM) ad libitum and were supplied with increasing amounts of US (0, 6, 13, 19 and 33 g US DM/kg hay DM) or Spirulina 0, 0.5, 1.4, 2.5 and 6.1 g Spirulina DM/kg W.day in an incomplete Latin square design. The response of MCP production and EMCP to increasing amounts of the two supplements was different, with a greater response to Spirulina evident. The MCP production was predicted to peak at 140 and 568 g MCP/day (0.64 and 2.02 g MCP/kg W.day) for the US and Spirulina supplements, respectively. The highest measured EMCP were 92 and 166 g MCP/kg DOM for the US and Spirulina treatments at 170 and 290 g RDP/kg DOM, respectively, or a Spirulina intake of 5.7 g DM/kg W.day. Increasing RDP intake from US and Spirulina resulted in an increase in Mitchell grass hay intake and rumen NH3-N concentration and reduced the retention time of liquid and particulate markers and digesta DM, NDF and lignin in the rumen with greater changes due to Spirulina. Total DM intake peaked at a Spirulina supplement level of 4.6 g Spirulina DM/kg W.day with a 2.3-fold higher DOM intake than Control steers. Rumen NH3-N concentrations reached 128 and 264 mg NH3-N/L for the US and Spirulina treatments with a significant increase in the concentration of branched-chain fatty acids for the Spirulina treatment. The minimum retention time of liquid (Cr-EDTA; 23 and 13 h) and particulate (Yb; 34 and 22 h) markers in the rumen were significantly lower for Spirulina compared with US and lower than unsupplemented animals at 24 and 34 h for Cr-EDTA and Yb, respectively. Spirulina could be provided safely at much higher N intakes than NPN supplements. The results suggest that, at an equivalent RDP supply, Spirulina provided greater increases than US in MCP production, EMCP and feed intake of Bos indicus cattle consuming low protein forage and could also be fed safely at higher levels of N intake.

Harmful algae in the planktonic food web of the Baltic Sea

This study deals with algal species occurring commonly in the Baltic Sea: haptophyte Prymnesium parvum, dinoflagellates Dinophysis acuminata, D. norvegica and D. rotundata, and cyanobacterium Nodularia spumigena. The hypotheses are connected to the toxicity of the species, to the factors determining toxicity, to the consequences of toxicity and to the transfer of toxins in the aquatic food web. Since the Baltic Sea is severely eutrophicated, the fast-growing haptophytes have potential in causing toxic blooms. In our studies, the toxicity (as haemolytic activity) of the haptophyte P. parvum was highest under phosphorus-limited conditions, but the cells were toxic also under nitrogen limitation and under nutrient-balanced growth conditions. The cellular nutrient ratios were tightly related to the toxicity. The stoichiometric flexibility for cellular phosphorus quota was higher than for nitrogen, and nitrogen limitation led to decreased biomass. Negative allelopathic effects on another algae (Rhodomonas salina) could be observed already at low P. parvum cell densities, whereas immediate lysis of R. salina cells occurred at P. parvum cell densities corresponding to natural blooms. Release of dissolved organic carbon from the R. salina cells was measured within 30 minutes, and an increase in bacterial number and biomass was measured within 23 h. Because of the allelopathic effect, formation of a P. parvum bloom may accelerate after a critical cell density is reached and the competing species are eliminated. A P. parvum bloom indirectly stimulates bacterial growth, and alters the functioning of the planktonic food web by increasing the carbon transfer through the microbial loop. Our results were the first reports on DSP toxins in Dinophysis cells in the Gulf of Finland and on PTX-2 in the Baltic Sea. Cellular toxin contents in Dinophysis spp. ranged from 0.2 to 149 pg DTX-1 cell-1 and from 1.6 to 19.9 pg PTX-2 cell-1 in the Gulf of Finland. D. norvegica was found mainly around the thermocline (max. 200 cells L-1), whereas D. acuminata was found in the whole mixed layer (max. 7 280 cells L-1). Toxins in the sediment trap corresponded to 1 % of DTX-1 and 0.01 % PTX-2 of the DSP pool in the suspended matter. This indicates that the majority of the DSP toxins does not enter the benthic community, but is either decomposed in the water column, or transferred to higher trophic levels in the planktonic food chain. We found that nodularin, produced by Nodularia spumigena, was transferred to the copepod Eurytemora affinis through three pathways: by grazing on filaments of small Nodularia, directly from the dissolved pool, and through the microbial food web by copepods grazing on ciliates, dinoflagellates and heterotrophic nanoflagellates. The estimated proportion of the microbial food web in nodularin transfer was 22-45 % and 71-76 % in our two experiments, respectively. This highlights the potential role of the microbial food web in the transfer of toxins in the planktonic food web.