Aquaculture is an industry with the capacity for further growth that can contribute to sustainable food systems to feed an increasing global population. Sugar kelp (Saccharina latissima) is of particular interest for farmers as a fast-growing species that benefits ecosystems as a primary producer. However, as a new industry in the U.S., farmers interested in growing S. latissima lack data on growth dynamics. To address this gap, we calibrated a Dynamic Energy Budget (DEB) model to data from the literature and field-based growth experiments in Rhode Island (U.S.A.). Environmental variables forcing model dynamics include temperature, irradiance, dissolved inorganic carbon concentration, and nitrate and nitrite concentration. The modeled estimates for field S. latissima blade length were accurate despite underestimation of early season growth. In some simulations, winter growth was limited by the rate at which the light-dependent reaction of photosynthesis, the first step of carbon assimilation, was performed. Nitrogen (N) reserves were also an important limiting factor especially later in the spring season as irradiance increased, although the low resolution of N forcing concentrations might restrict the model accuracy. Since this model is focused on S. latissima grown in an aquaculture setting with winter and spring growth, no specific assumptions were made to include summer growth patterns such as tissue loss or reproduction. The results indicate that this mechanistic model for S. latissima captures growth dynamics and blade length at the time of harvest, thus it could be used for spatial predictions of S. latissima aquaculture production across a range of environmental conditions and locations. The model could be a particularly useful tool for further development of sustainable ocean food production systems involving seaweed.
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The role of intertidal seaweeds in the primary production of mesotidal and macrotidal estuaries has been examined by means of a model, applied to the Tagus Estuary (Portugal). Special attention was paid to the description of the underwater light climate in intertidal areas, and to the importance of the formation of tidal pools. Two approaches were compared for the simulation of suspended particulate matter (SPM) in the pool areas, using three algal species.The use of an erosion–deposition approach to simulate the distribution of SPM in tidal pools gives an increase in net primary productivity per unit area of between 130 and 1300%, when compared to the more conventional approach where the suspended matter in the overlying water in intertidal areas is considered identical to that in the channels.The upscaled erosion–deposition model was applied to tidal pool areas and combined with the more conventional model for other intertidal areas. Results show that annual carbon fixation by intertidal seaweeds in the estuary exceeds 13,500 t C yr−1, and accounts for 21% of the total carbon fixed by all primary producers. The corresponding nitrogen removal by seaweeds corresponds to the annual nutrient loading of a population of 490,000 inhabitants.
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Phosphorus (P) is an essential non-renewable nutrient that frequently limits plant growth. It is the foundation of modern agriculture and, to a large extent, demand for P is met from phosphate rock deposits which are limited and becoming increasingly scarce. Adding an extra stroke to this already desolate picture is the fact that a high percentage of P, through agricultural runoff and waste, makes its way into rivers and oceans leading to eutrophication and collapse of ecosystems. Therefore, there is a critical need to practise P recovery from waste and establish a circular economy applicable to P resources. The potential of microalgae to uptake large quantities of P and use of this P enriched algal biomass as biofertiliser has been regarded as a promising way to redirect P from wastewater to the field. This also makes the study of molecular mechanisms underlying P uptake and storage in microalgae of great interest. In the present paper, we review phosphate models, which express the growth rate as a function of intra- and extracellular phosphorus content for better understanding of phosphate uptake and dynamics of phosphate pools.
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A 3-dimensional hydrodynamic-ecological model system (SINMOD) was used to estimate the full-scale cultivation potential of the brown alga Saccharina latissima in integrated multi-trophic aquaculture (IMTA) with Atlantic salmon Salmo salar. A previously developed model for the frond size and composition (carbon and nitrogen content) of S. latissima sporophytes was adjusted to data from an outdoor mesocosm growth experiment and then coupled and run online with the 3-dimensional model system. Results from simulations were compared with data from an IMTA field experiment, providing partial validation of the hydrodynamic-ecological-kelp model system. The model system was applied to study the large-scale cultivation potential of S. latissima in IMTA with salmon and to quantify its seasonal bioremediation potential. The results suggest a possible yield of 75 t fresh weight S. latissima ha(-1) in 4 mo (February to June) and about 170 t fresh weight ha(-1) in 10 mo (August to June). The results further suggest that the net nitrogen consumption of a 1 ha S. latissima installation in the vicinity of a fish farm producing approximately 5000 t salmon in a production cycle is about 0.36 (0.15) t NH4+-N, or a removal of 0.34% (0.41%) of the dissolved inorganic nitrogen effluent with a cultivation period from August (February) to June. Due to the differing seasonal growth patterns of fish and kelp, there was a mismatch between the maximum effluent of NH4+-N from the fish farm and the maximum uptake rates in S. latissima.
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Background: The red macroalgae Asparagopsis taxiformisis a potent natural supplement for reducing methane production from cattle. A. taxiformiscontains several anti-methanogenic compounds including bromoform that inhibits directly methanogenesis. The positive and adverse effects of A. taxiformison the rumen microbiota are dose-dependent and operate in a dynamic fashion. It is therefore key to characterize the dynamic response of the rumen microbial fermentation for identifying optimal conditions on the use of A. taxiformisas a dietary supplement for methane mitigation. Accordingly, the objective of this work was to model the effect of A. taxiformissupplementation on the rumen microbial fermentation under in vitroconditions. We adapted apublished mathematical model of rumen microbial fermentationto account for A. taxiformissupplementation. We modelled the impact of A. taxiformison the fermentationand methane production by two mechanisms, namely (i) direct inhibition of the growth rate of methanogens by bromoform and (ii) hydrogen control on sugars utilization and on the flux allocation towards volatile fatty acids production.We calibrated our model using a multi-experiment estimation approach that integrated experimental datawith six macroalgae supplementation levels from a published in vitrostudy assessing the dose-response impact of A. taxiformison rumen fermentation. Results:our model captured satisfactorily the effect of A. taxiformison the dynamic profile of rumen microbial fermentation for the six supplementation levels of A. taxiformiswith an average determination coefficient of 0.88 and an average coefficient of variation of the root mean squared error of 15.2%for acetate, butyrate, propionate, ammonia and methane. Conclusions:our results indicated the potential of our model as prediction tool for assessing the impact of additives such as seaweeds on the rumen microbial fermentationand methane production in vitro.Additional dynamic data on hydrogen and bromoform are required to validate our model structure and look for model structure improvements. We expect this model development can be useful to help the design of sustainable nutritional strategies promoting healthy rumen function and low environmental footprint.
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Biological CO2 capture using microalgae is a promising new method for reducing CO2 emission of coal-fired flue gas. The strain of microalgae used in this process plays a vital role in determining the rate of CO2 fixation and characteristics of biomass production. High requirements are put forward for algae strains due to high CO2 concentration and diverse pollutants in flue gas. CO2 can directly diffuse into the cytoplasm of cells by extra- and intracellular CO2 osmotic pressure under high CO2 concentrations. The flue gas pollutants, such as SOx, NOx and fly ashes, have negative effects on the growth of microalgae. This work reviewed the state-of-the-art advances on microalgae strains used for CO2 fixation, focusing on the modification and improvement of strains that are used for coal-fired flue gas. Methods such as genetic engineering, random mutagenesis, and adaptive evolution have the potential to facilitate photosynthesis, improve growth rate and reduce CO2 emission.
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Polysialic acid (polySia) and polySia glycomimetic molecules support nerve cell regeneration, differentiation, and neuronal plasticity. With a combination of biophysical and biochemical methods, as well as data mining and molecular modeling techniques, it is possible to correlate specific ligand–receptor interactions with biochemical processes and in vivo studies that focus on the potential therapeutic impact of polySia, polySia glycomimetics, and sulfated polysaccharides in neuronal diseases. With this strategy, the receptor interactions of polySia and polySia mimetics can be understood on a submolecular level. As the HNK-1 glycan also enhances neuronal functions, we tested whether similar sulfated oligo- and polysaccharides from seaweed could be suitable, in addition to polySia, for finding potential new routes into patient care focusing on an improved cure for various neuronal diseases. The knowledge obtained here on the structural interplay between polySia or sulfated polysaccharides and their receptors can be exploited to develop new drugs and application routes for the treatment of neurological diseases and dysfunctions.
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The current drive towards renewable energy has led to interest in the use of marine biomass, including seaweed. The presence of readily hydrolysable sugars, low amounts of cellulose and zero lignin enhances the suitability of seaweed for methane production, but this process has so far received little attention. As seaweeds have been shown to contain constituents with antimicrobial properties, understanding the microbial interactions in the system is crucial.
The aim of this study was to investigate the microbial community associated with seaweed anaerobic digestion in order to understand the intricate interaction between the microbial population and process functions. Selected seaweeds (Laminaria digitata, Saccharina lattissima and Fucus serratus) found commonly on the west coast of Scotland were subjected to 50-day anaerobic batch digestion using different inoculum sources. A number of molecular techniques including, denaturing gradient gel electrophoresis, quantitative polymerase chain reaction, cloning and sequencing were employed to study the microbial ecology of the seaweed fed reactors. Results show that marine sediment is a viable microbial source for efficient methane fermentation of L. digitata and S. latissima at seawater salinity level, and indicates that methane production from both seaweeds compares favourably with other types of biomass, including terrestrial crops.
Results obtained suggest that microbial numbers fluctuate during anaerobic digestion, potentially in response to substrates availability. Analysis of microbial community structure highlights temporal and spatial variations in microbial diversity within and across reactors, possibly as a result of process conditions and functions.
Identification of the dominant archaea and methanogens indicate that Methanomicrobiales and Methanosarcinales-related species could dominate sediment and sludge inoculated reactors, indicating the potential for utilisation of a diverse range of substrates. Results from the functional gene clone library, suggest that hydrogenotrophic, acetoclastic and methylotrophic methanogenesis could potentially be involved in methane production.
Overall, this study provides insights into the microbial ecology of seaweed anaerobic reactors and the microbial responses to changing conditions. Results highlight possible routes for optimisation of the anaerobic digestion process, which could help prevent system failure during large-scale seaweed anaerobic digestion. -
Molecular biotechnology of marine algae is referred to as the biotechnology on the identification, modification, production and utilization of marine algal molecules. It involves not only the manipulation of macromolecules such as DNA, RNA and proteins, but also deals with low molecular weight compounds such as secondary metabolites.
In the last decade, molecular systematic researches to investigate the relationship and to examine the evolutionary divergence among Chinese marine algae have been carried out by Chinese scientists. For example, RAPD has been widely used in several laboratories to elucidate genetic variations of the reds, such as Porphyra, Gracilaria, Grateloupia and the greens such as VIva and Enteromorpha. Some important data have been obtained. The study on molecular genetic markers for strain improvement is now in progress.
In 1990s, genetic engineering of economic seaweeds such as Laminaria, Vndaria, Porphyra, Gracilaria and Grateloupia has been studied in China. For Laminariajaponica, the successfully cultivated kelp in China, a model transformation system has been set up based on the application of plant genetic techniques and knowledge of the algal life history. Progress has been made recently in incorporating a vaccine gene into kelp genome. Evidence has been provided showing the expression of gene products as detectable vaccines.
In the present paper, the progress of molecular biotechnological studies of marine algae in China, especially researches on elucidating and manipulating nucleic acids of marine algae, are reviewed.
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Giant kelp, despite the economic and ecological value, is much confused in taxonomy. To discuss possible changes of the current classification system, we introduce published results and newly analysed sequences of both nuclear ribosomal DNA and plastid-encoded RuBisCo spacer. All members of the Alariaceae, Laminariaceae, and Lessoniaceae are grouped into a single monophyletic clade, while each family is not monophyletic. Eight groups are recognized: i) Egregia group, ii) Alaria group, iii) Laminaria group, iv) Hedophyllum group, v) Ecklonia group, vi) Agarum group, vii) Lessonia group, and viii) Macrocystis group. This results appear not to support the current familial system of advanced kelp, and rather suggest that a single family like Laminaria and Kjellmaniella are necessary because of their paraphyly.
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