Article à la Une

Sargassum contamination and consequences for downstream uses: a review

Damien A. Devault, Ronan Pierre, Hélène Marfaing, Franck Dolique & Pascal-Jean Lopez

Abstract

Sargassum spp. are brown algae present in the tropical and subtropical waters of the world’s oceans. Benthic or pelagic, Sargassum spp. represent substantial amounts of biomass when drifted and massive beaching events also named “golden tides” are challenging for environmental and tourism managers. The Sargassum spp. biomass can be regarded as offering economic opportunities; however, micropollutant contamination counteracts this wealth. This review describes the contaminant uptake processes and the concentrations reached by various Sargassum species in regard to national and international norms for a variety of applications. Amongst the heavy metals, perhaps total arsenic content is the most salient: phytoaccumulation of arsenic is due to confusion in the phosphate transporter between arsenic and phosphate, thus leading Sargassum spp. to bioaccumulate arsenic actively. The levels reached could well give cause for concern across all potential applications, in particular for human and animal use. Similarly, there are concerns for the widespread applications or disposal of this biomass due to environmental impacts in the case of storage, landfill or composting. Organic micropollutants are too rarely studied to assert that there is global contamination. However, research studies focused on Sargassum spp. contamination confirmed environmental threats. But, without exhaustive analysis of routine algae contamination, the standard contamination level cannot be defined. Treating beach-cast or drifting Sargassum spp. as a waste is a Gordian knot, in that it involves investment, work and disposal surfaces, whilst not necessarily providing environmental and economic gains. However, Sargassum spp. are a raw material, a resource rich in a broad variety of constituents that could be processed for commercial applications or which could be used for production of energy. In this paper the authors review the diverse applications that can be considered and describe the relevant regulations and norms related to contaminants and effluents that need to be taken into account. However, if valorizing Sargassum spp. is currently valuable and promising, the quality of the raw material is a key starting point because fresh and sand-free algae are required: offshore gathering solutions need to be developed in order to limit Sargassum sp. contamination by pollutants from land so as to hinder algae decay.

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Article à la une

Physical properties of epilithic river biofilm as a new lead to perform pollution bioassessments in overseas territories

Dominique Monti, Cedric Hubas, Xavier Lourenço, Farid Begarin, Alexandre Haouisée, Laurence Romana, Estelle Lefrançois, Alexandra Jestin, Hélène Budzinski, NathalieTapie, Théo Risser, Jean‑Louis Mansot, Philippe Keith, Olivier Gros, Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser. & Béatrice Lauga

Scientific Reports, 2020, 10 (1).

Chlordecone (CLD) levels measured in the rivers of the French West Indies were among the highest values detected worldwide in freshwater ecosystems, and its contamination is recognised as a severe health, environmental, agricultural, economic, and social issue. In these tropical volcanic islands, rivers show strong originalities as simplifed food webs, or numerous amphidromous migrating species, making the bioindication of contaminations a difcult issue. The objective of this study was to search for biological responses to CLD pollution in a spatially fxed and long-lasting component of the rivers in the West Indies: the epilithic bioflm. Physical properties were investigated through complementary analyses: friction, viscosity as well as surface adhesion were analyzed and coupled with measures of bioflm carbon content and exopolymeric substance (EPS) production. Our results have pointed out a mesoscale chemical and physical reactivity of the bioflm that can be correlated with CLD contamination. We were able to demonstrate that epilithic bioflm physical properties can efectively be used to infer freshwater environmental quality of French Antilles rivers. The friction coefcient is reactive to contamination and well correlated to carbon content and EPS production. Monitoring bioflm physical properties could ofer many advantages to potential users in terms of efectiveness and ease of use, rather than more complex or time-consuming analyses.

Lien vers le text intégral: https://www.nature.com/articles/s41598-020-73948-7.pdf