![Whisker box plots showing the distribution of DO (A), PO4 3− (B), NO2 − + NO3 − (C), NH4 + (D), and chl-a (E) in the surface water of the Kishon Estuary between 2002-2021. Background colors represent the water quality thresholds as suggested here for small stratified inland estuaries (see Table 2), where red stands for bad water quality, orange for moderate, and green for the good ecological state. The nutrients and chl-a threshold between good ecological status (GES) and non-GES for Haifa Bay coastal water (SE Mediterranean Sea) derived from Kress et al. (2019) [23] are shown as pink lines within the box plots generated for the harbor station (F).](https://www.researchgate.net/profile/Yael-Segal-2/publication/361876551/figure/fig2/AS:1179906885066756@1658323131937/Whisker-box-plots-showing-the-distribution-of-DO-A-PO4-3-B-NO2-NO3-C-NH4_Q320.jpg)
![Relationship between NO2 − + NO3 − (A) or DIN (B) vs. PO4 3− concentrations in surface water at the Kishon harbor during this study, 2002-2021 (black circle) and measurements performed during 1993-2000 (white triangles, [24,25]). The linear regression slopes for this study and 1993-2000 in panel A are 17.3 and 2.6, and in panel B are 11.3 (or 17.6 excluding the high anomalous value) and 4.6, respectively. The anthropogenic N:P load ratio is shown in panel (C) (grey square, calculated from the source: Israel Ministry of Environmental Protection, 2021 Report on pollutants budget; www.gov.il/he/departments/guides/kishon_stream_point_pollution_loads?chapterIndex=5).](https://www.researchgate.net/profile/Yael-Segal-2/publication/361876551/figure/fig3/AS:11431281121943956@1677137139062/Relationship-between-NO2-NO3-A-or-DIN-B-vs-PO4-3-concentrations-in-surface_Q320.jpg)
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Enrichment of nutritional compounds in seaweeds via abiotic stressors in integrated aquaculture
Abstract and Figures
Seaweeds may contain significant amounts of essential proteins, carbohydrates, and minerals, offering an alternative, sustainable, healthy food source from the sea. However, there are yet challenges impending their full exploitation. Our study presents an innovative, two-step aquaculture approach integrating seaweeds and finfish, dedicated to enrich seaweeds with nutritional compounds. The approach involves diverting fish effluents rich in nutrients into a series of seaweed cultivation tanks. Then, the seaweeds were exposed to short-term abiotic stressors (namely, high irradiance, nutrient starvation, and high salinity) to stimulate synthesis of desired ingredients in their tissues. Our methodology enabled high growth rates of up to 25% seaweed biomass increase per day, with significant enhancements in the amount of protein, starch, and minerals within days. Moreover, the seaweeds presented elevated bioremediation capabilities assimilating the ammonia nitrogen, NO3 and PO4 with high uptake rates, and with 50–75% removal efficiencies.
Industrial relevance
The rising public awareness to quality of healthier food products has stimulated growing demand for seaweed supply. Our new approach suggests a promising direction toward the transition from seaweed production of raw, commodity seaweed biomass, to a tailored production of functional seaweeds, enriched with valued compounds that can be utilized in the emerging food and health industries.
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... Interestingly, in the current work, there were no significant differences in the antioxidant capacity between the shaded cultures and those that were exposed to 100% sunlight, in which a higher antioxidant capacity would be expected. We presume that this could have been the result of self-shading and interactive photoprotection by the seaweeds' thalli, which accumulated rapidly due to the optimal combination of culture season (spring bloom) and IMTA conditions [23]. As noted, high salinity was the additional factor that presented the highest antioxidant capacity for all the study's three seaweed species-Ulva rigida, Gracilaria conferta, and Hypnea muschformis. ...
... The integrated mariculture setup used in the current study was designed and installed in a land-based experimental seaweed site at the Israel Oceanographic and Limnological Research center in Haifa, Israel, as described in our earlier work [23]. The integrated system had two components: (1) a culture tank stocked with gilthead sea bream fish (Sparus aurata), and (2) a series of seaweed cultures tanks (n = 6) alternatively stocked with one of three local macroalgae species, the green macroalga Ulva rigida, or one of two red macroalgae, Gracilaria conferta and Hypnea musciformis. ...
Marine macroalgae are considered an untapped source of healthy natural metabolites and their market demand is rapidly increasing. Intertidal macroalgae present chemical defense mechanisms that enable them to thrive under changing environmental conditions. These intracellular chemicals include compounds that can be used for human benefit. The aim of this study was to test cultivation protocols that direct seaweed metabolic responses to enhance the production of target antioxidant and photoprotective biomaterials. We present an original integrated multi-trophic aquaculture (IMTA) design, based on a two-phase cultivation plan, in which three seaweed species were initially fed by fish effluents, and subsequently exposed to various abiotic stresses, namely, high irradiance, nutrient starvation, and high salinity. The combined effect of the IMTA’s high nutrient concentrations and/or followed by the abiotic stressors enhanced the seaweeds’ content of mycosporine-like amino acids (MAAs) by 2.3-fold, phenolic compounds by 1.4-fold, and their antioxidant capacity by 1.8-fold. The Sun Protection Factor (SPF) rose by 2.7-fold, and the chlorophyll and phycobiliprotein synthesis was stimulated dramatically by an order of magnitude. Our integrated cultivation system design offers a sustainable approach, with the potential to be adopted by emerging industries for food and health applications.
... The color of seaweed thallus has been related to tissue nitrogen content (e.g. Nagler et al., 2003;Yu and Yang, 2008;Robertson-Andersson et al., 2009;Ashkenazi et al., 2022;Stedt et al., 2022a). Nitrogen is a major component of the chlorophyll molecule , and changes in chlorophyll content alters the color of the seaweed thallus (Robertson-Andersson et al., 2009). ...
... -Luna et al., 2010;Tewari et al., 2013;Riccardi et al., 2014;Zhang et al., 2022). Even though changes in seaweed thallus color due to changes in tissue nitrogen content have been widely reported for seaweeds (Nagler et al., 2003;Yu and Yang, 2008;Robertson-Andersson et al., 2009;Ashkenazi et al., 2022;Stedt et al., 2022aStedt et al., , 2022b, no previous studies have to our knowledge developed models to quantitatively assess the nitrogen status of seaweeds based on color. Our study showed that all the three band colors R, G, and B can be used in simple and multiple linear regression models to predict the nitrogen content of the seaweed. ...
There is an increasing interest in the cultivation of seaweeds for food and feed, and the seaweed aquaculture industry is rapidly developing. The nutritional status of the seaweeds is important to ensure a good quality crop. Cost-efficient and straightforward methods for farmers to analyze their crop are essential for the successful development of the industry. In this study, we developed non-destructive, labor- and cost-efficient models to estimate the nitrogen content in the crop seaweed Ulva fenestrata by color image analysis. We quantified tissue nitrogen content and thallus color in sea-farmed seaweed every week throughout a whole cultivation season (15 consecutive weeks) and analyzed data with linear regression models. We showed that color image analysis accurately estimated the nitrogen content in the seaweed (R2 = 0.944 and 0.827 for fresh tissue and dried powder, respectively), and through tenfold cross validation we showed that the developed models were robust and precise. Based on these models, we developed a web-based application that automatically analyzes the nitrogen content of U. fenestrata. Furthermore, we produced a color guide that can easily be brought to the farm for onsite crude estimation of the nitrogen content of U. fenestrata. Our results demonstrate that color can be a powerful tool for seaweed farmers (and researchers) to estimate seaweeds’ nutritional status. We anticipate that similar models can be developed for other commercially interesting seaweed species.
... Indeed, seaweeds take up significant amounts of dissolved inorganic carbon (DIC, thereafter) during growth, offering a unique alternative to sequester excessive atmospheric CO 2 . Seaweeds can also deliver important additional benefits to humans, such as food, proteins, minerals, or active natural molecules to alleviate human needs soon (widely addressed in Ashkenazi et al. 2019Ashkenazi et al. , 2022. These aspects of food security have received much attention and are strongly supported by the European Commission. ...
The ongoing climate changes have resulted from high levels of anthropogenic CO2 being released into the atmosphere in the past decades. Carbon-cutting measures have been proposed to reduce global warming by 2 °C, bringing it back to preindustrial levels. There are several options on hand to meet the need for carbon reduction on a global basis, and one such option refers to CO2 sequestration via the photosynthesis of macroalgae. Species of the green seaweed Ulva are ubiquitous throughout the world oceans; they can maintain fast growth during most seasons thanks to their unique photosynthetic capacity combined with high nitrogen and phosphorous uptake rates. High commodity productions of seaweeds, such as green species of Ulva, can also deliver important additional benefits and ecosystem services, including human food, animal feed, proteins, minerals, or active natural molecules, therefore alleviating human needs shortly. Still, whether seaweeds, in general, can trap CO2 for long periods (100 years) is controversial. Technical and biological gaps need to be resolved before an effective and sustainable seaweed-based mass production intended for the sequestration of CO2 is established. This study elaborates on the potential global use of seaweeds in sequestering carbon and addresses the efficient inorganic carbon uptake and fixation traits of Ulva species. This study also overviews the photosynthetic traits and growth of seaweeds in offshore, semi-controlled, and land-based cultivation settings, focusing on total carbon budgets and footprints for Ulva sp. from the Israeli Mediterranean Sea. Altogether this work addresses the potential use of Ulva sp. as a valuable tool to moderate climate changes.
... Marine seaweeds are increasingly used in biological applications, particularly in the pharmaceutical and feed formulation industries, because they contain a diverse range of bioactive and nutritional compounds and primary and secondary metabolites with potential therapeutic activity such as antimicrobial, anticancer, antiviral, anti-inflammatory, and immunomodulatory (Shah et al. 2022;Lomartire et al. 2021;Carpena et al. 2022;Ashkenazi et al. 2022). The marine seaweed-derived polysaccharides can be used for animal nutrition and improved animal intestinal integrity and enhanced immune responses (Leandro et al. 2019;Silva-Brito et al. 2022). ...
The present study investigated the dietary fishmeal replacement by marine red seaweed (Halymenia dilatata) meal (RSM) on growth performance, feed utilization, chemical body composition, hematological constituents, digestive, antioxidant, and metabolic enzymes in freshwater fish Labeo rohita (Rohu) fingerlings. The fish were fed with RSM-free control diet (RSM0) and four experimental diets, which replaced fish meal (FM) with varying levels of RSM (25%, 50%, 75%, and 100%, represented as RSM25, RSM50, RSM75, and RSM100 respectively). After a 60-day feeding trial, the survival rate (SR), growth performance (length gain, weight gain, and specific growth rate), protein efficiency ratio, chemical body composition (protein, lipid, and ash), and digestive enzymes (amylase and protease) were significantly increased (P < 0.05) in the fish fed with RSM50 diet containing 39% protein level. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) revealed a higher staining intensity of muscle proteins in fish fed with the RSM50 diet. However, the hematological constituents (hemoglobin, hematocrit, red blood cell, white blood cell, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration), antioxidant enzyme - superoxide dismutase, and metabolic enzymes (glutamic oxaloacetic transaminase and glutamic pyruvic transaminase) were not significantly altered in RSM50 diet when compared to control. In contrast, hematological constituents were decreased (P < 0.05), and antioxidant and metabolic enzymes were increased in rohu fed with RSM75 and RSM100 (P < 0.05). Furthermore, these findings suggest that RSM might be adopted at a pace of 37% (estimated polynomial second-order regression) and is found to be beneficial for freshwater fish L. rohita diets that enhance growth and immune responses. The current study recommended substituting (50%) of marine red seaweed (Halymenia dilatata) for fish meal significantly improves the growth performance, chemical body composition, and digestive enzymes of L. rohita and this could be a valuable natural replacement for fishmeal to reduce the production cost of aquatic feed.
Eutrophication caused by an excessive presence of nutrients is affecting large portions of European waters with more than 60% of the surface water bodies failing to achieve the primary ambition of water management in Europe, that of good ecological status (GES) with diffuse emission from agriculture being the second most important pressure affecting surface waters. We developed EU wide and regional nutrient targets that define the boundary concentrations between good and moderate status for river and lake total P (TP) and total N (TN) and assessed the gap between actual nutrient concentrations and these targets and considered strategies of nutrient reductions necessary to achieve GES and deliver ecosystem services. The nutrient targets established for rivers ranged from 0.5–3.5 mg/L TN and 11–105 μg/L TP and for lakes 0.5–1.8 mg/L TN and 10–60 μg/L TP. Based on the EU wide targets, 59% of the TN and 57% of the TP river monitoring sites and 64% of the TN and 61% of the TP lake monitoring sites exceed these value and are thus at less than GES. The PCA and step-wise regression for EU basins clearly showed that the basin nutrient export is predominantly related to agricultural inputs. In addition, the step-wise regression models for TN and TP provided the ability to extrapolate the results and quantify the input reductions necessary for reaching the nutrient targets at the EU level. The results suggest that a dual water management strategy would be beneficial and should focus a) on those less polluted rivers and lakes that can easily attain the GES goal and b) on the more highly polluted systems that will improve the delivery of ecosystem services.
The growing world population demands an increase in sustainable resources for biorefining. The opening of new farm grounds and the cultivation of extractive species, such as marine seaweeds, increases worldwide, aiming to provide renewable biomass for food and non-food applications. The potential for European large-scale open ocean farming of the commercial green seaweed crop Ulva is not yet fully realized. Here we conducted manipulative cultivation experiments in order to investigate the effects of hatchery temperature (10 and 15 °C), nutrient addition (PES and 3xPES) and swarmer density (500 and 10,000 swarmers ml−1) on the biomass yield and biochemical composition (fatty acid, protein, carbohydrate, pigment and phenolic content) of off-shore cultivated Ulva fenestrata in a Swedish seafarm. High seedling densities were optimal for the growth of this northern hemisphere crop strain and significantly increased the mean biomass yield by ~84% compared to low seedling densities. Variations of nutrients or changes in temperature levels during the hatchery phase were not necessary to increase the subsequent growth in an open-water seafarm, however effects of the factors on the thallus habitus (thallus length/width) were observed. We found no significant effect of the environmental factors applied in the hatchery on the total fatty acid or crude protein content in the off-shore cultivated Ulva. However, low seedling density and low temperature increased the total carbohydrate content and furthermore, high temperature in combination with high nutrient levels decreased the pigment content (chlorophyll a, b, carotenoids). Low temperature in combination with high nutrient levels increased the phenolic content. Our study confirms the successful and sustainable potential for large-scale off-shore cultivation of the Scandinavian crop U. fenestrata. We conclude that high seedling density in the hatchery is most important for increasing the total biomass yield of sea-farmed U. fenestrata, and that changing temperature or addition of nutrients overall does not have a large effect on the biochemical composition. To summarize, our study contributes novel insights into the large-scale off-shore cultivation potential of northern hemisphere U. fenestrata and underpins suitable pre-treatments during the hatchery phase of seedlings to facilitate a successful and cost-efficient large-scale rope cultivation.
Sustainable development is an integrated approach to tackle ongoing global challenges such as resource depletion, environmental degradation, and climate change. However, a paradigm shift from a fossil-based economy to a bio-based economy must accomplish the circularity principles in order to be sustainable as a solution. The exploration of new feedstock possibilities has potential to unlock the bio-based economy’s true potential, wherein a cascading approach would maximize value creation. Seaweed has distinctive chemical properties, a fast growth rate, and other promising benefits beyond its application as food, making it a suitable candidate to substitute fossil-based products. Economic and environmental aspects can make seaweed a lucrative business; however, seasonal variation, cultivation, harvesting, and product development challenges have yet not been considered. Therefore, a clear forward path is needed to consider all aspects, which would lead to the commercialization of financially viable seaweed-based bioproducts. In this article, seaweed’s capability and probable functionality to aid the bio-based economy are systematically discussed. The possible biorefinery approaches, along with its environmental and economic aspects of sustainability, are also dealt with. Ultimately, the developmental process, by-product promotion, financial assistance, and social acceptance approach are summarized, which is essential when considering seaweed-based products’ feasibility. Besides keeping feedstock and innovative technologies at the center of bio-economy transformation, it is imperative to follow sustainable-led management practices to meet sustainable development goals.
The FAO recently published its biennial State of World Fisheries and Aquaculture up to 2018. The FAO continues to treat the seaweed aquaculture sector as a different category, with separate tables and comments in different sections. As this could lead to a distorted view of total world aquaculture, the statistical information provided by FAO was revisited and data regarding the seaweed aquaculture sector were integrated with data of the other sectors of the world aquaculture production, to reach different conclusions: 1) aquaculture represents 54.1% of total world fisheries and aquaculture production; 2) marine and coastal aquaculture represents 55.2% of total world aquaculture production; 3) seaweeds represent 51.3% of total production of marine and coastal aquaculture; 4) 99.5% of seaweed mariculture production is concentrated in Asia; 5) 8 seaweed genera provide 96.8% of world seaweed mariculture production; 6) 2 seaweed genera are the most produced organisms in mariculture in the world; 7) the value of the seaweed aquaculture sector could be much larger, especially if a monetary value was attributed to the ecosystem services provided by seaweeds; and 8) total extractive aquaculture is slightly larger (50.6%) than total fed aquaculture (49.4%).
Hydrogels based on the polysaccharide ulvan from the green macroalgae Ulva fenestrata were synthesized and evaluated as an adsorbent for heavy metals ions and methylene blue. Ulvan was extracted from Ulva fenestrata using diluted hydrochloric acid and recovered by precipitation with EtOH. The extracted ulvan was converted into ulvan dialdehyde via periodate-oxidation and subsequently combined with gelatin yielding hydrogels. The hydrogels showed good water-uptake capacity with a maximum swelling degree of 2400% in water and 900% in PBS buffer. Adsorption tests of methylene blue showed a maximum adsorption capacity of 465 mg/g. The adsorption data of methylene blue followed the pseudo-second order kinetics and agreed with the Langmuir adsorption isotherm. The maximum adsorption capacity of heavy metal ions was 14 mg/g for Cu²⁺, 7 mg/g for Co²⁺and 6 mg/g for Ni²⁺and Zn²⁺ indicating that the hydrogels have a stronger affinity for Cu²⁺ than for Co²⁺, Ni²⁺, and Zn²⁺.
We investigated the growth and bioremediation potential of five local seaweed species (Codium fragile, Ulva pertusa, Ecklonia stolonifera, Saccharina japonica and Gracilariopsis chorda), using an integrated fish‐seaweed culture system as a biofilter for effluents from black rockfish (Sebastes schlegelii) tanks. The specific growth rate, biomass and net yield values of green algae were higher than those of brown algae. The tissue N and P levels of all species increased at the end of the experiment, but N:P ratios varied among seaweed species. The uptake rate and efficiency of total ammonia nitrogen uptake were the highest in U. pertusa and lowest in S. japonica. The phosphate uptake efficiency among all species ranged from 43% for S. japonica to 30% for G. chorda. These results suggest that all species can efficiently remove enriched nitrogen and phosphorus from fish tank effluents and are suitable for integrated aquaculture and bioremediation. However, inter‐specific differences were observed among seaweeds with regard to the biofiltration performance for different forms of nitrogen. The highest total oxidized nitrogen (ToxN) uptake efficiency was observed in E. stolonifera and S. japonica, while the lowest was observed in U. pertusa. ToxN uptake rates of E. stolonifera and S. japonica was 1.8 times higher than that of U. pertusa. Thus, a seaweed polyculture that included species with varying nitrogen source‐specific biofiltration activities might allow us to remove nutrients from effluents more effectively. These results provide valuable information regarding the selection of optimal seaweed species in fish‐seaweed integrated systems.
Seaweed (macroalgae) is considered as a sustainable bioresource rich in high‐quality nutrients such as protein. Seaweed protein can be used as an alternative to other protein sources. Furthermore, these proteins are natural reservoirs of bioactive peptides (BAPs) associated with various health benefits such as antioxidant, antihypertensive and antidiabetic activities. However, seaweed derived BAPs remain underexploited due to challenges which arise during protein extraction from algal biomass. Coupled with this, limited proteomic information exists regarding certain seaweed species. This review highlights the current state of the art of seaweed protein extraction techniques, e.g., liquid, ultrasound, microwave, pulsed electric field and high hydrostatic pressure assisted extraction. The review also focuses on the enzymatic hydrolysis of seaweed proteins and characterisation of the resultant hydrolysates/peptides using electrophoretic and chromatographic techniques. This includes reference to methods employed for separation, fractionation and purification of seaweed BAPs, as well as the methodologies used for identification, e.g., analysis by mass spectrometry. Furthermore, a bioinformatics or in silico approach to aid discovery of seaweed BAPs is discussed herein. Based on the information available to date, it is suggested that further research is required in this area for the development of seaweed BAPs for nutraceutical applications.
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The estimated marginal cost of U.S. water pollution control often exceeds its marginal benefit. We provide intuition, theory and empirical evidence suggesting that the hedonic property model—a common revealed-preference approach to valuing pollution control—may not capture water’s recreational benefits. Using the case of Tampa Bay, Florida, we estimate willingness to pay (WTP) for water quality improvements by combining a recreation demand model with a hedonic property model. Results indicate that homeowners have significant WTP for both local and regional recreational water quality improvements and suggest that prior hedonic studies may underestimate the benefits of water pollution control.
Seaweed aquaculture is capable of removing large quantities of nitrogen and phosphorus from coastal ecosystems, yet seaweed has gained little traction for its potential role in targeted nutrient assimilation. Marine nutrient pollution is increasing around the world, contributing to expanding eutrophic conditions and co-occurring with other stressors that impact the state and stability of aquatic ecosystems. In the United States, climate change, legacy nitrogen, and nonpoint source pollution make it increasingly difficult to curb growing eutrophication and the associated effects, such as hypoxia (dissolved oxygen < 2 mgL⁻¹). Employing a synthetic semi-quantitative approach, we use the Gulf of Mexico as a case study – a U.S. priority area for aquaculture with substantial nutrient pollution and one of the largest hypoxic zones on the planet – to assess the potential for native seaweed aquaculture to augment upstream pollution control with downstream nutrient assimilation. Results from this analysis suggest that given growing market demand, new product pathways, and nutrient pollution markets, seaweed aquaculture may be a feasible tool for nutrient assimilation that could subsidize, if not pay for itself.
Traditional culinary applications, nutritional benefits, and growing conditions (no need of arable land or fresh water) make seaweeds an attractive alternative and sustainable food source for the future. However, their widespread consumption will require not only their promotion as nutritious and healthy foods but also applications in savory culinary dishes and food product formulations appealing to consumers. This review highlights the relevance of umami components in seaweed species as a source of unique flavors and their role in sensorial and physiological functions. It analyzes current work on texture and flavor in fresh and processed macroalgae. Novel applications of seaweeds are discussed through a portfolio of culinary and food products including fresh and fermented seaweeds, reformulated conventional products, powder ingredients consumed as healthy supplements or salty and flavorful condiments, and gastronomic creations of chefs in high-end restaurants.