Bioremediation and fodder potentials of two Sargassum spp. in coastal waters of Shenzhen, South China

A comparison of physiological responses between attached and pelagic populations of Sargassum horneri under nutrient and light limitation

Large-scale Sargassum blooms have been increasingly observed in coastal zones in recent years. Sargassum horneri (Turner) C. Agardh blooms (pelagic) have been observed in Jeju Island (Korea) and the southwest of the Korean Peninsula, causing serious problems for seaweed and abalone farms as well as for fisheries, tourism and recreational industries. The present study explored the physiological responses of attached and pelagic S. horneri populations cultivated under different nutrient concentrations (HN: 50 μM of nitrogen and 5 μM of phosphorus; LN: 5 μM of nitrogen and 0.5 μM of phosphorus) and photosynthetically active radiation (PAR) (H-PAR: 250; M-PAR: 150; L-PAR: 50 μmol photons m-2 s-1) for 25 days. Relative growth rates (RGR) were significantly lower in the pelagic population than that in the attached population. All thalli from the pelagic population died within 20 days. Chlorophyll a and c, and carotenoids were significantly higher at HN than at LN, and decreased as PAR increased for both populations. For the attached population, photosynthetic rate, tissue nitrogen, and carbon and nitrogen removal were also significantly higher at HN than at LN. These results suggest that high nutrient and lower PAR increased the biomass accumulation of attached populations in coastal areas. Nutrient limitation and high PAR may accelerate senescence of the pelagic populations while traveling on the sea surface from their point of origin.

Mechanistic interaction of ciprofloxacin on zeolite modified seaweed (Sargassum crassifolium) derived biochar: Kinetics, isotherm and thermodynamics

Modification of biochar for efficient removal of antibiotics from water could be a valuable approach in the environmental applications. In this study, a brown seaweed (Sargassum crassifolium) was pyrolyzed at 500 °C and the obtained biochar (SWBC) was modified with zeolite through the slurry method maintaining the ratio at 1:5 (zeolite: biochar) (SWBC-Z). Batch adsorption experiments were conducted to evaluate the adsorption tendency of SWBC and SWBC-Z for the removal of ciprofloxacin (CPX) from water via pH edge, kinetics, isotherm and thermodynamic experiments. The highest adsorption was in the pH range of 6.5-8, supported by the electrostatic attractions and hydrogen bonding with zwitterionic CPX. Experimental kinetics data was well-fitted to the pseudo-second-order and Elovich models (R2 of 0.992 and 0.976, respectively), while the Langmuir and Freundlich isotherm models best described the isotherm data (R2 of 0.954 and 0.976, respectively). The maximum adsorption capacity of 93.65 mg g-1 was recorded for the SWBC-Z. The models predicted chemisorption and physisorption interactions on the heterogenous biochar surface. Well-defined peaks of silanol groups in the FTIR spectrum of SWBC-Z and its electron microscopy confirmed the incorporation of zeolite minerals. Post adsorption FTIR analysis elucidated the changes in the surface functional groups of the SWBC-Z. Thermodynamic data revealed spontaneous and exothermic reaction between CPX and both the biochars. It was concluded that modification of pristine biochar with zeolite imparted greater surface area and additional active sites, which subsequently enhanced the overall CPX adsorption by the SWBC-Z.

Eukaryotic communities in coastal water from Shenzhen in South China

Eukaryotic microorganisms are ubiquitous in the marine environment, and have a wide variety of ecosystem functions. Shenzhen is one of the most developed cities in South China, but the eukaryotic communities in the water along its coastlines remain poorly understood. The study applied 18S rRNA gene ITS (internal transcribed spacer) sequencing to identify the eukaryotic community from twenty sites of Shenzhen coast water. The alpha-diversity of the samples between these sites were significantly different, and the seawater of eastern coast had higher alpha-diversity compared to that of the western coast. The abundance of Chlorophyta was notably higher in the seawater of western coast, but Picozoa was relatively depleted. Specifically, Cryptocaryon, Pseudovorticella, and Cyclotella were significantly higher in the water of western coast, while Guinardia, Minutocellus, and Amoebophrya were increased in eastern samples. The spatially variations of eukaryotic microorganism community in the seawater of Shenzhen coast were associated with the water quality. The results have important significance for the understanding of coastal eukaryotic community, their interaction network, and build a foundation for future management and protection of coastal water quality.

Valorization of pelagic sargassum biomass into sustainable applications: Current trends and challenges

Since long ago, pelagic Sargassum mats have been known to be abundant in the Sargasso Sea, where they provide habitat to diverse organisms. However, over the last few years, massive amounts of pelagic Sargassum have reached the coast of several countries in the Caribbean and West Africa, causing economic and environmental problems. Aiming for lessening the impacts of the blooms, governments and private companies remove the seaweeds from the shore, but this process results expensive. The valorization of this abundant biomass can render Sargassum tides into an economic opportunity and concurrently solve their associated environmental problems. Despite the diverse fields where algae have found applications and the relevance of this recurrent situation, Sargassum biomass remains without large scale applications. Therefore, this review aims to present the potential uses of these algae, identifying the limitations that must be assessed to effectively valorize this bioresource. Due to the constraints identified for each of the presented applications, it is concluded that a biorefinery approach should be developed to effectively valorize this abundant biomass. However, there is an urgent need for investigations focusing on holopelagic Sargassum to be able to truly valorize this seaweed.

Bioremediation potential of Sargassum sp. biomass to tackle pollution in coastal ecosystems: Circular economy approach

During the past years, the ecological integrity and biodiversity of marine ecosystems have been highly threatened due to the controlled or uncontrolled release of high concentrations of pollutants generated through anthropogenic activities. The occurrence of environmentally related hazardous pollutants, such as toxic elements, and recalcitrant compounds in various environmental matrices has raised increasing concern. Different technologies have been developed for efficient removal and complete mitigation or degradation of these toxic elements from the aquatic environment. Among them, biosorption and bioaccumulation by renewable and biodegradable sources are of supreme interest and have not been reviewed much. For instance, the invasive seaweed Sargassum sp. has been spotted as a cost-effective natural material to capture targeted pollutants from the coastal ecosystem, which is currently becoming a pressing problem, around the globe, due to its unusual proliferation near tropical shores. This review is an effort to cover the left behind gap to present the multifunctional potentialities of Sargassum sp. biomass. Herein, salient information is given to highlight the potential of Sargassum sp. biomass for environmental decontamination with particular focus to coastal ecosystems. Bioremediation mechanisms, challenges of implementation and factors involved in adsorption and absorption of pollutants by seaweeds are also discussed in this review. Against this background, a circular economy perspective is given for the integrated use of the algal raw material. The up-taken pollutants can be recovered and reintegrated into the value chain of industrial processes, while residual biomass is refined to obtain added-value products as bioactive compounds with potential applications for biofuel, agriculture, cosmetics, nutraceutical, pharmaceutical industries among others, to make the most of renewable resources.

Baseline study on the levels of heavy metals in seawater and macroalgae near an abandoned mine in Manicani, Guiuan, Eastern Samar, Philippines

Lateritic nickel ore stockpiles are still present in Manicani Island after mining activities were suspended in 2001. This study aimed to assess the water quality in the island by measuring the levels of Pb, Ni and Cu in seawater and Sargassum polycystum samples collected quarterly in 2018. The levels of the three heavy metals in seawater samples were 0.388 ± 0.058-1.508 ± 0.120 mg/L Pb, 0.457 ± 0.003-0.531 ± 0.005 mg/L Cu, and 0.122 ± 0.008-0.628 ± 0.281 mg/L Ni. All values are above the permissible limits recommended by DENR and USEPA. Ni (13.630 ± 7.341-160.120 ± 3.375 mg/kg) had the highest concentration in S. polycystum, significantly higher than Pb ( Collapse

Key Words

• Abandoned mine
• Heavy metals
• Macroalgae
• Manicani Island
• Seawater

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MESH Headings

• Environmental Monitoring/methods
• Metals, Heavy/analysis
• Mining
• Nickel/analysis
• Philippines
• Sargassum/chemistry
• Seawater/analysis
• Seaweed/chemistry
• Water Pollutants, Chemical/analysis

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Grants Collapse

Affiliation(s)

Olga G Corales-Ultra Division of Natural Sciences and Mathematics, University of the Philippines Visayas Tacloban College, Magsaysay Boulevard, Tacloban City, Leyte 6500, Philippines.
Reynaldo P Peja Division of Natural Sciences and Mathematics, University of the Philippines Visayas Tacloban College, Magsaysay Boulevard, Tacloban City, Leyte 6500, Philippines; Environmental Management Department, Visayas State University - Alangalang, Alangalang, Leyte 6517, Philippines
Eulito V Casas Division of Natural Sciences and Mathematics, University of the Philippines Visayas Tacloban College, Magsaysay Boulevard, Tacloban City, Leyte 6500, Philippines

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Analysis of Seaweeds from South West England as a Biorefinery Feedstock

Seaweeds contain many varied and commercially valuable components, from individual pigments and metabolites through to whole biomass, and yet they remain an under cultivated and underutilised commodity. Currently, commercial exploitation of seaweeds is predominantly limited to whole biomass consumption or single product extracts for the food industry. The development of a seaweed biorefinery, based around multiple products and services, could provide an important opportunity to exploit new and currently underexplored markets. Here, we assessed the native and invasive seaweeds on the South West coast of the UK to determine their characteristics and potential for exploitation through a biorefinery pipeline, looking at multiple components including pigments, carbohydrates, lipids, proteins and other metabolites.

Biostimulation of in situ microbial degradation processes in organically-enriched sediments mitigates the impact of aquaculture

Fish farm deposition, resulting in organic matter accumulation on bottom sediments, has been identified as among the main phenomena causing negative environmental impacts in aquaculture. An in situ bioremediation treatment was carried out in order to reduce the organic matter accumulation in the fish farm sediments by promoting the natural microbial biodegradation processes. To assess the effect of the treatment, the concentration of organic matter in the sediment and its microbial degradation, as well as the response of the benthic prokaryotic community, were investigated. The results showed a significant effect of the treatment in stimulating microbial degradation rates, and the consequent decrease in the concentration of biochemical components beneath the cages during the treatment. During the bioremediation process, the prokaryotic community in the fish farm sediment responded to the overall improvement of the sediment conditions by showing the decrease of certain anaerobic taxa (e.g. Clostridiales, Acidaminobacteraceae and Caldilinaceae). This suggested that the bioactivator was effective in promoting a shift from an anaerobic to an aerobic metabolism in the prokaryotic community. However, the larger importance of Lachnospiraceae (members of the gut and faecal microbiota of the farmed fishes) in treated compared to non-treated sediments suggested that the bioactivator was not efficient in reducing the accumulation of faecal bacteria from the farmed fishes. Our results indicate that bioremediation is a promising tool to mitigate the aquaculture impact in fish farm sediments, and that further research needs to be oriented to identifying more successful interventions able to specifically target also fish-faeces related microbes.

Nutrient removal from Chinese coastal waters by large-scale seaweed aquaculture

China is facing intense coastal eutrophication. Large-scale seaweed aquaculture in China is popular, now accounting for over 2/3’s of global production. Here, we estimate the nutrient removal capability of large-scale Chinese seaweed farms to determine its significance in mitigating eutrophication. We combined estimates of yield and nutrient concentration of Chinese seaweed aquaculture to quantify that one hectare of seaweed aquaculture removes the equivalent nutrient inputs entering 17.8 ha for nitrogen and 126.7 ha for phosphorus of Chinese coastal waters, respectively. Chinese seaweed aquaculture annually removes approximately 75,000 t nitrogen and 9,500 t phosphorus. Whereas removal of the total N inputs to Chinese coastal waters requires a seaweed farming area 17 times larger than the extant area, one and a half times more of the seaweed area would be able to remove close to 100% of the P inputs. With the current growth rate of seaweed aquaculture, we project this industry will remove 100% of the current phosphorus inputs to Chinese coastal waters by 2026. Hence, seaweed aquaculture already plays a hitherto unrealized role in mitigating coastal eutrophication, a role that may be greatly expanded with future growth of seaweed aquaculture.

Antioxidant activities of crude phlorotannins from Sargassum hemiphyllum

Brown algae are well known as a source of biologically active compounds, especially those having antioxidant activities, such as phlorotannins. In this study we examined the antioxidant activities of crude phlorotannins extracts (CPEs) obtained from Sargassum hemiphyllum (SH) and fractionated according to the molecular weights. When CPEs were administrated at a dose of 30 mg/kg to Kunming mice pre-treated with carbon tetrachloride (CCl4), the levels of oxidative stress indicators in the liver, kidney and brain were significantly reduced in vivo. All the components of various molecular weight fractions of CPEs exhibited greater scavenging capacities in clearing hydroxyl free radical and superoxide anion than the positive controls gallic acid, vitamin C and vitamin E. Particularly, the components greater than 30 kD obtained from ethyl acetate phase showed the highest antioxidant capacities. These results indicated that SH is a potential source for extracting phlorotannins, the algal antioxidant compounds.

Trophic structure in a pilot system for the integrated multi-trophic aquaculture off the east coast of Korean peninsula as determined by stable isotopes

To assess the potential for nutritional exploitation of caged-fish-derived waste through the use of extractive co-cultured species in a pilot system for an integrated multi-trophic aquaculture (IMTA), we compared their C and N stable isotope ratios with those of uncultured macroinvertebrates in and around the system. Black rockfish were co-cultured with sea cucumber, oyster, and two macroalgae as extractive species. Isotope signatures of the co-cultured sea cucumber at the IMTA site differed from those at the control site, indicating their assimilation of aquaculture wastes. In contrast, δ(13)C and δ(15)N of individual taxa of the cultured oyster and uncultured invertebrates were consistent between sites, suggesting a minor contribution of the aquaculture waste to benthic and pelagic food chains in and around the IMTA system. These results provide evidence of the suitability of using sea cucumber as an extractive species to reduce the impact of a monoculture system on the ambient environment.