The integrated aquaculture of the tetrasporophyte of Asparagopsis armata Harvey (Falkenbergia rufolanosa) using fish farm effluents may be viable due to the species high capacity of removing nutrients and its content of halogenated organic compounds with applications on the pharmaceutical and chemical industries. In order to optimize the integrated aquaculture of F. rufolanosa, we followed the daily variation of the potential quantum yield (Fv/Fm) of PSII on plants cultivated at different biomass densities and different total ammonia nitrogen (TAN) fluxes to check if they are photoinhibited at any time of the day. Moreover, the photoinhibition under continuous exposure to highly saturating irradiance and its potential for subsequent recovery in the shade was assessed. The potential for year round cultivation was evaluated by measuring rates of O2 evolution of plants acclimated at temperatures ranging from 15 to 29 °C, the temperature range of a fish farm effluent in southern Portugal where an integrated aquaculture system of F. rufolanosa was constructed. Photoinhibition does not seem to be a major constrain for the integrated aquaculture of F. rufolanosa. Only when cultivated at a very low density of 1.5 g fresh weight (FW) l−1 that there was a midday decrease in maximal quantum yield (Fv/Fm). At densities higher than 4 g FW l−1 , no photoinhibition was observed. When exposed to full solar irradiance for 1 h, F. rufolanosa showed a 33% decrease in Fv/Fm, recovering to 86% of the initial value after 2 h in the shade. A midday decline of the F. rufolanosa Fv/Fm was also observed under the lowest TAN flux tested (∼6 μM h−1 ), suggesting that this fast and easy measurement of fluorescence may be used as a convenient diagnostic tool to detect nutrient-starved unbalance conditions of the cultures. Maximum net photosynthesis peaked at 15 °C with 9.7 mg O2 g dry weight (DW)−1 h−1 and remained high until 24 °C. At 29 °C, the net oxygen production was significantly reduced due to a dramatic increase of respiration, suggesting this to be the species' lethal temperature threshold. Results indicate that F. rufolanosa has a considerable photosynthetic plasticity and confirm it as a good candidate for integrated aquaculture at temperatures up to 24° C and cultivation densities of at least 5 g FW l−1 . When cultivated at these densities, light does not penetrate below the first few centimetres of the surface zone. Plants circulate within the tanks, spending around 10% of the time in the first few centimetres where they are able to use efficiently the saturating light levels without damaging their photosynthetic apparatus.
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Eutrophication has been considered to be undoubtedly one of the key factors stimulating phytoplankton growth, since it involves the enrichment of a water mass with both inorganic and organic nutrients supporting plant growth. Nutrient enrichment as a result of anthropogenic activity occurs in estuaries and coastal waters as well as in lakes and freshwater impoundments, and blooms of phytoplankton are one of the effects of such an accelerated process of nutrient enrichment. This paper presents the results of a two-year survey of the nutrients and phytoplankton at 3 stations in Junk Bay, Hong Kong, carried out from 1997 to 1998. The relationships between nitrogen, phosphorus, and their ratio, with phytoplankton abundance have been studied. The results show that the highest nitrogen concentration was in Station 2 which is close to a sewage input, whereas the highest phosphorus concentration was in Station 1 which is close to a landfill area. The mean N:P ratios at the three stations were between 8 and 14. The diatoms were the dominant group during most of the year but it seems that diatoms were more sensitive than dinoflagellates and other algal groups to the increase in nutrients.
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Uptake rates of nitrate and phosphate were measured for four species and one variety of Porphyra from Long Island Sound (USA) at two temperatures and two nutrient medium concentrations at increasing intervals over a 24- or 48-h period. Maximum uptake rates found were: V 30 AM 0–1 h =73.8 Amol NO3 g 1 DW h 1 and V 3 AM 0–1 h =16.7 Amol PO4 g 1 DW h 1 , in the two thinnest Porphyra. We found that the nitrate uptake rates were significantly greater at 30 AM than 3 A MN O3 concentration, and that the uptake rates decreased with time of exposure. Temperature (5, 15, and 25 8C) did not have as strong an effect on nitrate uptake rates as did nutrient concentration. Q10 values and uptake rates at four different nitrate concentrations indicated that nutrient uptake at 5 8C was initially an active process. After 24 h, the processes involved appeared passive as Q10 values were between 1.0 and 1.3 and nitrate uptake curves were linear. Nitrate uptake rates correlated positively with the surface area/ volume (SA/V) ratio. No coherent trends were found for uptake of phosphate, except that the uptake rates were significantly higher in 30 A MN O3 medium as opposed to 3 A MN O3. We did not find any significant difference in uptake rate and pattern between the summer species Porphyra purpurea (Roth.) C. Agardh, the eurythermic Porphyra suborbiculata Kjellm., the winter species Porphyra.
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The red alga Gracilaria vermiculophylla, a species native to the waters of Korea and Japan, has invaded marine coastal areas of Europe and the Americas, thriving in conditions that differ from those of its native habitat. In recent years, G. vermiculophylla has been discovered in the Long Island Sound (LIS) estuary growing alongside the native congener Gracilaria tikvahiae. The goal of this study was to determine whether the two strains of G. vermiculophylla from different regions of the world have evolved genetic differences (i.e., ecotypic differentiation) or if the physiological performance of the strains simply reflects phenotypic plasticity. Two strains of G. vermiculophylla (isolated in Korea and LIS) and a strain of the LIS native G. tikvahiae were grown for four weeks under temperatures ranging from 20 to 34°C using a temperature gradient table (all other environmental conditions were kept constant). At the end of each week, wet weight of each sample was recorded, and thalli were reduced to the original stocking density of 1 g L-1 (excess biomass was preserved for tissue carbon and nitrogen analysis). Generally, the growth rates of Korean G. vermiculophylla > LIS G. vermiculophylla > G. tikvahiae. After one week of growth G. tikvahiae grew 9.1, 12.0, 9.4, and 0.2% d-1, at temperatures of 20, 24, 29, and 34°C, respectively, while G. vermiculophylla (LIS) grew 6.6, 6.2, 5.7, and 3.6% d-1. G. vermiculophylla (Korea) grew 15.4, 22.9, 23.2, and 10.1% d-1, much higher than the two strains currently inhabiting the LIS. On average, the LIS G. vermiculophylla strain contained 4-5% DW N, while the Korean strain and G. tikvahiae had more modest levels of 2-3% N DW. However, tissue N content declined as temperature increased in LIS and Korean G. vermiculophylla. The non-native haplotype may have evolved genetic differences resulting in lower growth capacity while concentrating significantly more nitrogen, giving the non-native a competitive advantage.
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Josh Goldman runs a fish farm, but the hangar-size facility in the western Massachusetts town of Turners Falls looks a lot less like a farm than a factory. Thousands of one-third-pound barramundi — an omnivorous fish native to Southeast Asia and Australia — swim in a 36-ft.-diameter tank that resembles a supersize kiddie pool. They spend their days fattening up on feed pellets under the watchful eyes of factory workers — farmers, if you must — who grade them for size.
After several weeks of careful feeding, the fish are moved via an industrial waterslide — the pescalator, Goldman calls it — to a larger tank in the plant's next cavernous room. The assembly line runs until the barramundi have been raised to market weight, about 2 lb., after which they're sent off to white-tablecloth seafood restaurants and sustainability-minded retail outlets across the U.S.
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Assuring environmental sustainable bioenergy production is an international priority nowadays. The objective of this study was to identify the environmental consequences of feedstock selection in biogas production. Two real biogas plants were assessed and compared from a life cycle perspective. Plant A performs the co-digestion of energy crops (78%) and animal waste (22%) while Plant B consumes energy crops (4%), food waste (29%) and animal manure (67%). According to the results, electricity production from biogas implied lower impacts in climate change compared to the existing electric mix. Maize silage (650 Nm3 /TVSfed) and food waste (660 Nm3 /TVSfed) appeared as an interesting source of bioenergy. However, the cultivation of energy crops was identified as the main hotspot in Plant A. Finally, the use of organic substrates with lower energy potential and high nutrients concentration such as animal manure (450 Nm3 /TVSfed) produced higher amounts of digestate, producing impacts in acidification and eutrophication categories. In order to improve the environmental sustainability of bioenergy, specific guideless should be established to achieve harmonised life cycle studies. In addition, environmental policies should promote the use of waste streams and prevent the use of energy crops as well as include goals related with acidification and eutrophication impacts.
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Cultivation of kelp has been well established throughout Asia, and there is now growing interest in the cultivation of macroalgae in Europe to meet future resource needs. If this industry is to become established throughout Europe, then balancing the associated environmental risks with potential benefits will be necessary to ensure the carrying capacity of the receiving environments are not exceeded and conservation objects are not undermined. This is a systematic review of the ecosystem changes likely to be associated with a developing seaweed aquaculture industry. Monitoring recommendations are made by risk ranking environmental changes, highlighting the current knowledge gaps and providing research priorities to address them. Environmental changes of greatest concern were identified to include: facilitation of disease, alteration of population genetics and wider alterations to the local physiochemical environment. Current high levels of uncertainty surrounding the true extent of some environmental changes mean conservative risk rankings are given. Recommended monitoring options are discussed that aim to address uncertainty and facilitate informed decision-making. Whilst current small-scale cultivation projects are considered ‘low risk,’ an expansion of the industry that includes ‘large-scale’ cultivation will necessitate a more complete understanding of the scale dependent changes in order to balance environmental risks with the benefits that seaweed cultivation projects can offer.
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Seaweeds (marine macroalgae) are autotrophic organisms capable of producing manycompounds of interest. For a long time, seaweeds have been seen as a great nutritional resource,primarily in Asian countries to later gain importance in Europe and South America, as well as inNorth America and Australia. It has been reported that edible seaweeds are rich in proteins, lipids anddietary fibers. Moreover, they have plenty of bioactive molecules that can be applied in nutraceutical,pharmaceutical and cosmetic areas. There are historical registers of harvest and cultivation ofseaweeds but with the increment of the studies of seaweeds and their valuable compounds, theiraquaculture has increased. The methodology of cultivation varies from onshore to offshore. Seaweedscan also be part of integrated multi-trophic aquaculture (IMTA), which has great opportunitiesbut is also very challenging to the farmers. This multidisciplinary field applied to the seaweedaquaculture is very promising to improve the methods and techniques; this area is developed underthe denominated industry 4.0.
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Since 2007, Ulva macroalgal blooms have occurred along the coastal areas of the Yellow Sea, China. These blooms are dominated by fragments of Ulva prolifera in the early stages of development. The objectives of this study were to identify the primary mode of asexual reproduction for U. prolifera and to evaluate the contribution of these thalli fragments to the formation of blooms. Four different growth and reproductive strategies of U. prolifera segments were found including: 1) tubular diameter becoming larger; 2) formation of new branches; 3) release of zoids; and 4) polarized growth. This is the first report showing the development of numerous blade-lets from a single segment, which is remarkably different from previous studies on other Ulva species. The results in the present study provide critical information to understand how this species is able to support its explosive growth during a bloom.
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Six cultured `strains' of Eucheuma denticulatum and E. alvarezii, from which stocks can be selected for the development of a Eucheuma `seedling bank', were tested for their carrageenan quality from June to November 1988 . Percent yield of all the varieties taken together was apparently higher in June, becoming lower in November (regression, r -0.785, probability,p 5 0.001). Stepwise regression analysis was done to determine the existence of any relationship between any of the following parameters : gel strength, viscosity, sulfate content, month of sampling, and yield, whether taken individually or in combination . Results show variations of the yield with the month of sampling . ANOVA was performed to test whether there are differences in sulfate levels, gel strength, and viscosity between the Eucheuma alvarezii morphotypes. There was no significant difference between the green and the brown types.
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