Element concentrations in pelagicSargassumalong the Mexican Caribbean coast in 2018-2019

Abstract

The massive influx of pelagic Sargassum spp. (sargasso) into the Mexican Caribbean Sea has caused major deterioration of the coastal environment and has affected the tourism industry as well as livelihoods since 2015. Species of Sargassum have high capacity to absorb metals; thus, leachates of sargasso may contribute to contamination by potentially toxic metals when they drain into the sea and into the groundwater when dumped in inadequate land deposits. Valorization of sargasso would contribute to sustainable management; therefore, knowledge on potentially toxic metal content is necessary to define possible uses of the algae. We present concentrations of 28 elements measured using a non-destructive X-ray fluorescence analyzer (XRF) in 63 samples of sargasso collected between August 2018 and June 2019 from eight localities along ∼370 km long coastline of the Mexican Caribbean Sea. The sargasso tissues contained detectable concentrations of Al, As, Ca, Cl, Cu, Fe, K, Mg, Mn, Mo, P, Pb, Rb, S, Si, Sr, Th, U, V, and Zn. The element concentration in sargasso varied on spatial and temporal scales, which likely depended on the previous trajectory of the pelagic masses, and whether these had (or had not) passed through contaminated areas. Total arsenic concentration varied between 24–172 ppm DW, exceeding the maximum limit for seaweed intended as animal fooder (40 ppm DW) in 86% of the samples. For valorization, we recommend analyses of metal contents as a mandatory practice or avoiding uses for nutritional purposes. The high arsenic content is also of concern for environmental contamination of the sea and aquifer.

Sargassum Inundations in Turks and Caicos: Methane Potential and Proximate, Ultimate, Lipid, Amino Acid, Metal and Metalloid Analyses

“…The levels detected in this study generally fall within the results reported by Rodríguez-Martínez et al [43], but the levels in this study were considerably higher for iron and lower for manganese in all samples. The levels of both phosphorus and potassium in the 'Mixed Sargassum' were above the maximum levels found by Rodríguez-Martínez et al [43]. The levels of cadmium, chromium, copper, lead and manganese in the current study were similar to those found in S. muticum [86].…”

“…Some elements showed more than a 5-fold difference between their minimal and maximal concentrations [43]. The levels detected in this study generally fall within the results reported by Rodríguez-Martínez et al [43], but the levels in this study were considerably higher for iron and lower for manganese in all samples. The levels of both phosphorus and potassium in the 'Mixed Sargassum' were above the maximum levels found by Rodríguez-Martínez et al [43].…”

“…There has been a range of studies on metalloids in seaweed [69,84,85], but only limited data is available on pelagic Sargassum. However, Rodríguez-Martínez et al [43] recently completed a study on the concentrations of fourteen different elements (Al, As, Ca, Cl, K, Mg, Mn, P, Rb, S, Si, Sr, Th and U) in pelagic Sargassum collected from various sites along the Mexican Caribbean coast, from August 2018 to April 2019, and showed that there was both seasonal and spatial variability in metalloids. Some elements showed more than a 5-fold difference between their minimal and maximal concentrations [43].…”

“…However, Rodríguez-Martínez et al [43] recently completed a study on the concentrations of fourteen different elements (Al, As, Ca, Cl, K, Mg, Mn, P, Rb, S, Si, Sr, Th and U) in pelagic Sargassum collected from various sites along the Mexican Caribbean coast, from August 2018 to April 2019, and showed that there was both seasonal and spatial variability in metalloids. Some elements showed more than a 5-fold difference between their minimal and maximal concentrations [43]. The levels detected in this study generally fall within the results reported by Rodríguez-Martínez et al [43], but the levels in this study were considerably higher for iron and lower for manganese in all samples.…”

“…However, the concentration in the mixed sample (A) was considerably higher (123 mg kg −1 ). Arsenic levels of 13-172 mg kg −1 have been reported in pelagic Sargassum [43], and levels of up to 231 mg kg −1 have been recorded for members of the Sargassum genus [87].…”