The expansion of the global macroalgal aquaculture and climate change creates the need for germplasm preservation of valuable aquaculture strains and maintenance of natural biodiversity. Compared to the large number of studies in fish and shellfish species, relative few studies have been conducted on the macroalgal germplasm cryopreservation. The first cryopreservation of macroalgae to −75 °C was reported on Neopyropia tenera (formerly called Porphyra tenera) in 1964. To date, a total of 34 studies reported germplasm cryopreservation in 33 species, including Chlorophyta (7 species), Ochrophyta (14 species), and Rhodophyta (12 species). The goal of this review was to summarize the published studies on macroalgal germplasm cryopreservation, compare the reported protocols for the cryopreservation process, and identify the factors affecting post-thaw viability. Overall, macroalgal germplasm cryopreservation included haploid or diploid thalli, spores, and gametes. Cryotubes (1.5-ml or 2-ml) have been widely used to package germplasm samples for cooling and storage in most studies, and the 0.5-ml straws and 5-ml cryotubes have been used in several studies. Two approaches (programmable controlled cooling and vitrification) were employed for macroalgal germplasm cryopreservation. A two-step programmable controlled cooling (e.g., from initial culture temperature to a frozen temperature, such as −40 °C, and then directly plunging into liquid nitrogen at −196 °C) was determined to be an effective cooling strategy. Vitrification, a super rapid cooling for a sample to form non-crystalline amorphous solid, was applied on macroalgal germplasm cryopreservation with sample encapsulation and dehydration. Survival of post-thaw samples varied significantly in different studies. Based on research updates, recommendations are made for future research. It is expected that this review can serve as a foundation for future germplasm banking of macroalgae for aquaculture and biodiversity preservation.
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Species of the unicellular alga Dunaliella possess outstanding tolerance of a wide range of salinities. They can adapt to grow in salt media which range from less than 0.5 M to saturated salt solutions and withstand enormous osmotic shocks through a unique osmotic adaptation. The osmoregulating mechanism depends on photosynthetic production of glycerol, whose intracellular concentration varies in direct proportion to the extracellular salt concentration and reaches values in excess of 50% of the total dry weight of the cells. Dunaliella, and another halotolerant glycerol producing alga, Asteromonas gracilis, osmoregulate biochemically by controlling glycerol biosynthesis and degradation. 3 new enzymes, NADPH-dihydroxyacetone-reductase, dihydroxyacetone kinase and glycerol-1-phosphatase seem to be involved in the osmoregulatory response via glycerol in Dunaliella and Asteromonas. A hypothetical scheme of glycerol metabolism in these algae utilizing these enzymes is presented. Growth studies of Dunaliella indoors and outdoors showed that salt concentrations favoring maximal glycerol productivity are not identical with those required for maximal algal productivity. Maximal yield of glycerol occurred around 2 M NaCl while maximal algal productivity occurred below 0.5 M NaCl. Observed yields of glycerol in Dunaliella culture outdoors are compared with theoretically calculated maximal yield.
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The Seaweed Carrier mimics a natural seaweed, moving freely in the sea from a single mooring point. Testing with a small-scale carrier in Frøya in July 2011 reveals promise.
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The seaweeds are a diverse group of large marine macroalgae that are as important to the marine world as land plants are to our terrestrial world. Seaweeds were the precursors to land plants, and like land plants, they are critical primary producers, forming living links between the inorganic and the organic world, using photosynthesis to convert CO2 and nutrients into living biomass. These primary producers support and encourage other marine life through the production of oxygen, contribution to marine food webs, and by providing structure and habitat for refuge, breeding, and nursery grounds for fish and invertebrates. Seaweeds are an important resource for humans. Coastal peoples have always utilized seaweeds for food, minerals, medicine, fertilizer and fodder, and these sea-plants continue to provide for an everincreasing world population. A multi-billion dollar industry worldwide, seaweeds are consumed as nutritious sea vegetables, processed to extract valuable phycocolloids including agar, carrageenan, and alginate, and utilized in the agricultural industries for animal fodder or plant fertilizers.
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Palmaria palmata was integrated with Atlantic halibut Hippoglossus hippoglossus on a commercial farm for one year starting in November, with a temperature range of 0.4 to 19.1°C. The seaweed was grown in nine plastic mesh cages (each 1.25 m3 volume) suspended in a concrete sump tank (46 m3) in each of three recirculating systems. Two tanks received effluent water from tanks stocked with halibut, and the third received ambient seawater serving as a control. Thalli were tumbled by continuous aeration, and held under a constant photoperiod of 16 : 8 (L : D). Palmaria stocking density was 2.95 kg m-3 initially, increasing to 9.85 kg m-3 after a year. Specific growth rate was highest from April to June (8.0 to 9.0°C),1.1% d-1 in the halibut effluent and 0.8% d-1 in the control, but declined to zero or less than zero above 14°C. Total tissue nitrogen of Palmaria in effluent water was 4.2 to 4.4% DW from January to October, whereas tissue N in the control system declined to 3.0-3.6% DW from April to October. Tissue carbon was independent of seawater source at 39.9% DW. Estimated tank space required by Palmaria for 50% removal of the nitrogen excreted by 100 t of halibut during winter is about 29,000 to 38,000 m2, ten times the area required for halibut culture. Fifty percent removal of carbon from the same system requires 7,200 to 9,800 m2 cultivation area. Integration of P. palmata with Atlantic halibut is feasible below 10°C, but is impractical during summer months due to disintegration of thalli associated with reproductive maturation.
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Field cultivation of Gracilaria edulis was carried out in the nearshore areas of Gulf of Mannar and Palk Bay near Mandapam to determine the various environmental factors which affect the growth of this agar yielding seaweed. These culture experiments were conducted in Gulf of Mannar from October to April during the years 1986-89 and in Palk Bay from April to October during the years 1987-88 when the sea was calm at both places. The epiphytes, epifauna, Low light intensity and sedimentation caused by turbulence of water and grazing by fishes were found to be the primary factors hampering the growth of cultured G. edulis. There was no good growth of G. edulis in Palk Bay during the entire period of this study. But in Gulf of Mannar the growth of G. edulis was good between November and March with maximum yield during the months December to February1 March. The suitable period for field cultivation of G. edulis in Gulf of Mannar is from December to March.
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Maximum development of plants occurs in the intertidal region at Kilakarai, southeast mast of India, during March-April and Jan.-Feb. in (i. arcuara var. orcuara and from Nov. to Feb. in G. corticota var. cylindrica. Tetrasporic plants are abundant almost throughout the year in both algae. Peak shedding of spores occurs during the maximum growth period in G. orcuota var. arcuoro while seasonal variations are not observed in the discharge of spores in G. corricata var. cylindrica. Monthly output of tetraspores and carpospores varies from 43 19 28,291 and from 10 to 40,055 spores g -1 fr wt in G. arcuoro var. orcuaro and G. corricoro var. cylindrica respectively. There is no definite rhythm in diurnal output in these algae.
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We examined the gut health potential of the brown seaweed Ecklonia radiata and its polysaccharides. Rats consumed an AIN-93G-based diet without addition (control) or containing 5% (w/w) of ground dried whole seaweed (WS) or dried powdered polysaccharide fraction (PF) of the seaweed for 1 wk. The PF consisted largely of fucoidan and alginate. PF treatment increased cecal digesta weight relative to the control (1.36 ± 0.17 vs 0.60 ± 0.06 g/100 g body weight). Beneficial cecal total short chain fatty acids increased in response to WS (213.25 ± 14.40 μmol) and PF (208.59 ± 23.32 μmol) compared with the control (159.96 ± 13.10 μmol). Toxic protein fermentation product levels were decreased by WS and PF. Cecal numbers of bacteria relevant to gut health were determined using quantitative real-time PCR. Relative to the control, numbers of butyrate-producing Faecalibacterium prausnitzii were increased by PF supplementation, whereas WS decreased numbers of potentially pathogenic Enterococcus. In conclusion, E. radiata-derived polysaccharides have promise as prebiotic supplements.
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While seaweed cultivation is indeed practiced globally, it is by no means a mature industry. In part, this is because that in spite of the tremendous biodiversity available within this “polyphyletic rag bag” of distantly-related photosynthetic organisms, very few species have actually been studied sufficiently to bring them into domestication for production. This is not unlike the situation with terrestrial agronomy.
The history of extensive cultivation of seaweeds is several centuries old. One of the major, global centers for innovation and production of industrial-scale quantities of biomass for processing has been the Philippines and in turn the Coral Triangle.
However, the species and strains of seaweeds currently in cultivation, often clonally propagated on account of their relative ease of producing propagules, have been victim to their own success. Farmers and industry have simply used the same, limited pool of biomass and techniques for too long. This has led to declines in yield and quality of constituents due to loss of vigor and increased incidences of pests and diseases. Innovation is urgently required both in the choice candidate species for cultivation and also the necessary steps and techniques required for the reliable and sustainable production of industrial quantities of biomass.
Once again, the Philippines is at the forefront of leading technologies for the selection of novel candidate species for responsible, phyconomic activities. These species are economically valuable candidates, not only for their colloidal constituents, but also the more innovative applications of biologically active compounds from seaweeds used for the benefit of human, animal, plant and microbial products. Selected examples of these biologically active constituents and their applications are briefly reviewed.
This chapter summarizes advances being made in the Philippines and outlines developments in several candidate species as future cultivated, marine crops.
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The effect of Ocean Acidification (OA) on marine biota is quasi-predictable at best. While perturbation studies, in the form of incubations under elevated pCO2, reveal sensitivities and responses of individual species, one missing link in the OA story results from a chronic lack of pH data specific to a given species' natural habitat. Here, we present a compilation of continuous, high-resolution time series of upper ocean pH, collected using autonomous sensors, over a variety of ecosystems ranging from polar to tropical, open-ocean to coastal, kelp forest to coral reef. These observations reveal a continuum of month-long pH variability with standard deviations from 0.004 to 0.277 and ranges spanning 0.024 to 1.430 pH units. The nature of the observed variability was also highly site-dependent, with characteristic diel, semi-diurnal, and stochastic patterns of varying amplitudes. These biome-specific pH signatures disclose current levels of exposure to both high and low dissolved CO2, often demonstrating that resident organisms are already experiencing pH regimes that are not predicted until 2100. Our data provide a first step toward crystallizing the biophysical link between environmental history of pH exposure and physiological resilience of marine organisms to fluctuations in seawater CO2. Knowledge of this spatial and temporal variation in seawater chemistry allows us to improve the design of OA experiments: we can test organisms with a priori expectations of their tolerance guardrails, based on their natural range of exposure. Such hypothesis-testing will provide a deeper understanding of the effects of OA. Both intuitively simple to understand and powerfully informative, these and similar comparative time series can help guide management efforts to identify areas of marine habitat that can serve as refugia to acidification as well as areas that are particularly vulnerable to future ocean change.
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Marine Agronomy Group, CAFNRM, UH-Hilo
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