"Brown algae Sargassum sinicola and Sargassum lapazeanum were tested as cadmium biosorbents in coastal environments close to natural and enriched areas of phosphorite ore. Differences in the concentration of cadmium in these brown algae were found, reflecting the bioavailability of the metal ion in seawater at several sites. In the laboratory, maximum biosorption capacity (q max) of cadmium by these nonliving algae was determined according to the Langmuir adsorption isotherm as 62.42 ± 0.44 mg g−1 with the affinity constant (b) of 0.09 and 71.20 ± 0.80 with b of 0.03 for S. sinicola and S. lapazeanum, respectively. Alginate yield was 19.16 ± 1.52% and 12.7 ± 1.31%, respectively. Although S. sinicola had far lower biosorption capacity than S. lapazeanum, the affinity for cadmium for S. sinicola makes this alga more suitable as a biosorbent because of its high q max and large biomass on the eastern coast of the Baja California Peninsula. Sargassum biomass was estimated at 180,000 t, with S. sinicola contributing to over 70%."

"Rates of biosorption of cadmium and copper ions by nonliving biomass of the brown macroalga Sargassum sinicola under saline conditions were studied. Batch experiments show that the ability to remove cadmium is significantly diminished (from 81.8% to 5.8%), while the ability to remove copper remains high (from 89% to 80%) at a range of salinity from 0 to 40 psu. Maximum capacity of biosorption at 35 psu was 3.44 mg g−1 for cadmium and 116 mg g−1 for copper. The presence of salt did not significantly affect the rate of biosorption, which was about 90% of saturation in 60 min for both metals. There is an antagonistic effect on biosorption when both metals are present in the solution."

We determined metal contents of co-occurring algae Padina crassa and Sargassum sp. in Port Jackson (Australia), and relationships between metal levels and the abundance of epifaunal amphipods. Copper, lead and zinc concentrations were amongst the highest yet recorded in these algae. Copper, manganese and lead concentrations were far greater in P. crassa than Sargassum sp., possibly due to the low growth of P. crassa in proximity to contaminated sediments. However, in manipulative experiments the proximity of algae to sediments did not explain these differences. The abundance of herbivorous amphipods correlated negatively with the copper content of P. crassa, but not with the lower concentrations in Sargassum sp. The greater contamination of P. crassa led to patchy distributions of metals in algal beds and recolonisation experiments showed Sargassum sp. acts as a refuge from contaminants for epifauna. The contamination of macroalgae may pose threats to epifauna in harbours around the world. The accumulation of metals by macroalgae may pose ecological threats to herbivorous epifauna in ports and harbours worldwide.

We utilized volcanic CO₂ vents at Castello Aragonese off Ischia Island as a natural laboratory to investigate the effect of lowered pH/elevated CO₂ on the bioactivities of extracts from fleshy brown algae Sargassum vulgare C. Agardh. We analysed the carbohydrate levels, antioxidant capacity, antibacterial, antifungal, antiprotozoal, anticancer properties and antimutagenic potential of the algae growing at the acidified site (pH ∼ 6.7) and those of algae growing at the nearby control site Lacco Ameno (pH∼8.1). The results of the present study show that the levels of polysaccharides fucoidan and alginate were higher in the algal population at acidified site. In general, extracts for the algal population from the acidified site showed a higher antioxidant capacity, antilipidperoxidation, antibacterial, antifungal, antiprotozoal, anticancer activities and antimutagenic potential compared to the control population. The increased bioactivity in acidified population could be due to elevated levels of bioactive compounds of algae and/or associated microbial communities. In this snapshot study, we performed bioactivity assays but did not characterize the chemistry and source of presumptive bioactive compounds. Nevertheless, the observed improvement in the medicinal properties of S. vulgare in the acidified oceans provides a promising basis for future marine drug discovery.

International audience | The use of biochars (BCs) and activated carbons as a way of sequestering soil-bound pollutants such as chlordecone (CLD) is increasingly being studied. This study aims at assessing the impact of Sargassum BC/AC particle size and Sargassum BC amendment rate on CLD adsorption in Nitisol and in Andosol. Four different types of carbonaceous matrices were tested: Sargasso carbon activated by phosphoric acid (SargH3PO4), Sargasso carbon activated by steam (SargH2O), biochar of Sargasso (Ch Sarg700), and a commercial activated carbon (ORBO™). In a first experiment, CLD contaminated Andosol and Nitisol were amended with 2% of each carbonaceous matrix divided into four particles size classes (< 50 µm, 50–150 µm, 150–200 µm, and > 200 µm). In a second experiment, the contaminated soils were amended with the biochar of Sargasso at five application rates (0, 0.25, 0.5, 1, and 2% (w/w)). After a 4-month aging, environmental availability tests were carried out on the soils of both experiments. The results of the first experiment showed that the best reductions of CLD environmental availability were obtained in both soils with the biochar of Sargasso and the ORBO™. More specifically, in nitisol, particle size under 50 µm of biochar of Sargasso and AC ORBO™ showed a CLD environmental availability reduction up to 72 ± 2.6% and 79 ± 2.6%. In Andosol, there was no significant difference between the three particle sizes (< 50 µm, 50–150 µm, and 150–200 µm) of the biochar of Sargasso on the reduction of environmental availability (average reduction of 43 ± 2.5%). The results of the second experiment showed that an amendment rate increase improves the immobilization of CLD. When the amendment rate was increased from 0.25 to 2%, the environmental availability was reduced by 43% in Nitisol and 50% in Andosol.

In recent years, the North Atlantic and the Caribbean Sea have experienced unusual and unprecedented pelagic Sargassum blooms, which may adversely affect coastal ecosystems and productive ocean. Sargassum has the potential to scavenge trace elements and radionuclides from seawater, and when bioaccumulated and thus concentrated, can pose a potential threat to higher trophic organisms, including humans that consume impacted seafood. In this study, trace elements and naturally-occurring U/Th-series radionuclides were measured in Sargassum that were collected in the coastal waters of the Caribbean Sea (Antigua/Barbuda, Belize, and Barbados) to better define baseline concentrations and activities, and to assess the scavenging potential for these trace elements and radionuclides. The mean concentration of trace elements observed in Sargassum collected across these three Caribbean Sea are ranked accordingly to the following descending order: Sr > As>Fe > Mn > Zn > Ni > V > C > Cd > Se > Co > Cr > Pb > Ag > Hg. 210-Po and ²¹⁰Pb activities in Sargassum were observed to be more elevated than previously reported values.

This baseline study highlights the ²¹⁰Po and ²¹⁰Pb concentration in seven macroalgae species from the northern Gulf that are frequently washed ashore during the bloom season from February to April. The highest concentrations of ²¹⁰Po and ²¹⁰Pb were 2.947 ± 0.032 and 1.057 ± 0.145 Bq kg⁻¹ wwt, respectively, in brown algae Sargassum boveanum, and the lowest in green algae Ulva prolifera with 1.533 ± 0.058 and 0.170 ± 0.069 Bq kg⁻¹ wwt, respectively. A ²¹⁰Po enrichment was observed in both brown and green algae species, with the ²¹⁰Po/²¹⁰Pb ratio being >1 for all the samples. The mean concentration of ²¹⁰Po in all species was an order of magnitude higher than ²¹⁰Pb, and the difference in mean concentration is statistically significant (p < 0.001). At the same time, the mean concentration of dissolved ²¹⁰Po and ²¹⁰Pb in seawater was 0.28 ± 0.01 and 0.52 ± 0.01Bq m⁻³ with a ²¹⁰Po/²¹⁰Pb ratio of 0.54 ± 0.02 indicating that ²¹⁰Po was absorbed from water and more concentrated by macroalgae. The measured concentration factor (CF) for ²¹⁰Po in these macroalgae for the northern Gulf varied between 5 × 10³–1 × 10⁴, higher than the IAEA recommended value of 1 × 10³ which suggests that a revision of that value may be needed. The field derived CFs for ²¹⁰Pb vary between 3 × 10²–1.8 × 10³, comparable to the ICRP recommended value of 2 × 10³.

Since 2011, tropical beaches from Africa to Brazil, Central America, and the Caribbean have been inundated by tons of sargassum seaweed from a new equatorial source of pelagic sargassum in the Atlantic. In recent years the extraordinary accumulations of sargassum make this a nuisance algal bloom for tropical coasts. In 2018 satellite data indicated floating mats of sargassum that extended throughout the Caribbean to the northeast coast of Brazil with the highest percent coverage over the water yet recorded. A literature review suggests that Atlantic equatorial recirculation of seaweed mats combined with nutrients from several possible sources may be stimulating the growth and accumulations of sargassum. In the western equatorial recirculation area, new nutrient sources may include Amazon River floods and hurricanes; in the eastern equatorial recirculation area, nutrient sources that could sustain the sargassum blooms include coastal upwelling and Congo River freshwater and nutrients.

We investigated the influence of the intertidal geothermal hot spring (GHS) on the biogeochemistry of trace elements in Santispac Bight, Bahía Concepción (Gulf of California). The geothermal fluids were enriched in As and Hg mainly in ionic form. The suspended particulate matter of the GHS had elevated enrichment factor (EF) >1 of As, Bi, Cd, Co, Cu, Mn, Mo, Sb, Sn, Sr, Ti, U and Zn. The sediment core from GHS1 had high concentration of As, Hg, Corg, S, V, Mo, and U and the extremely high EF of these elements at 8cm of the core. The maximum bioaccumulation of As and Hg was in seaweeds Sargassum sinicola collected near the GHS2. The results confirm the input of trace elements to the coastal zone in Bahía Concepción from geothermal fluids and the evident modification of the chemical composition of the adjacent marine environment.

The potential of Indonesian bays as alginate producers was assessed by determining the stock of wild brown algae and exploring their biomass as alginophytes at the scale of entire bay, using a combination of field observations, remote sensing high resolution data and GIS tools. Ekas Bay in Lombok Island presented a stock of brown macroalgae which varied with season and species: for Padina the biomass reached 97.85±12.63 and 79.54±2.53tons in May/June and November respectively; for Sargassaceae species, it reached 669.70±109.64 and 147.70±77.97tons in May/June and November respectively. The best alginate yields occurred during the May/June period: Padina could produce 9.10±0.06tons DW of alginates. Interestingly, Sargassum/Turbinaria together allow 207.61±0.42tons DW of alginates. This study suggests that wild Sargassaceae represent an interesting stock in terms of biomass, alginate yield and M/G ratio.