Transformation of arsenic lipids in decomposing Ecklonia radiata

Abstract

To investigate the release and degradation of arsenolipids present in the marine brown macroalga Ecklonia radiata, tissues were collected in various stages of decomposition from intertidal environments, while tissues were also decomposed in laboratorybased microcosms prepared using combinations of autoclaved and natural (non-autoclaved) seawater and sand. Field collected macroalgae samples contained 20-120 μg g −1 total As of which 1-10% were arsenolipids comprising mainly an arsenic hydrocarbon (AsHC; 3-13% of total arsenolipids) and four di-acyl arsenic phospholipids (AsPLs; 86-95%). Additionally, a mono-acyl AsPL was found in all water-column decomposing samples. Arsenolipid concentrations in live tissues were similar to those in tissues decomposing in the water-column (1.3-2.9 μg g −1 dry mass), which were both up to four times higher than those in decomposing tissues collected from intertidal environments (0.7-1.3 μg g −1 dry mass). In the microcosm experiments, the arsenolipid content of E. radiata decreased substantially as decomposition proceeded. In the majority of microcosms, more than 75% of the arsenolipids present initially disappeared within 5 days with only the AsHC persisting until day 60 (the length of the experiment). This study demonstrates that the habitat in which decomposition occurs influences the release and degradation of arsenolipids with the greatest losses occurring when tissues decompose in intertidal environments. Microbial diversity, biomass, and overall activity are thus likely to play important roles in the persistence of arsenolipids in decomposing algae.

Arsenolipids in Plankton from High- and Low-Nutrient Oceanic Waters Along a Transect in the North Atlantic

“…Microbes may then degrade the arsenolipids to simpler arsenic species that are released into the water. 4 Such a scenario would be consistent with depth profiles of arsenic species in North Atlantic waters, where arsenobetaine and several other small arsenicals were associated mainly with the photic zone but were also found at depths of 200 m and beyond. 29 In summary, we report that arsenolipids were present in all 61 natural phytoplankton samples collected from areas of high-, intermediate-, and low-nutrient contents in the North Atlantic.…”

“…Phytoplankton are constantly being consumed by the oceans’ heterotrophs leading to phytoplankton debris and fecal material, which sink slowly through the water column. Microbes may then degrade the arsenolipids to simpler arsenic species that are released into the water . Such a scenario would be consistent with depth profiles of arsenic species in North Atlantic waters, where arsenobetaine and several other small arsenicals were associated mainly with the photic zone but were also found at depths of 200 m and beyond …”

“…Naturally occurring arsenic-containing lipids (arsenolipids) are abundant in marine algae as a consequence of the uptake and biotransformation of arsenate naturally present in seawater. Research on the various arsenolipids in algae has mostly been performed with macroalgal species and has shown the presence of two main classes, namely, arsenic-containing hydrocarbons (AsHCs) and arsenosugar phospholipids (AsPLs), − whereas in cyanobacteria, only AsPLs have been discovered to date. , …”

Arsenolipids in Cultured Picocystis Strain ML and Their Occurrence in Biota and Sediment from Mono Lake, California

“…This likely reflected the osmoregulatory strategy of this zooplankter, the main consumer of Picocystis, thereby gratuitously obtaining a "salt-out" adaptation capacity by feeding. Arsenolipids were still present in the sediment samples, although at lower percentage levels than that displayed in the phytoplankton, presumably due to microbial degradation in the water column and within the sediment itself, as suggested by Glabonjat et al [22,50]. This is better reflected by the greatly diminished levels of arsenobetaine, which presumably lends itself more readily to anaerobic biodegradation than arsenolipids, analogous to that for glycine betaine [51].…”

Origin of arsenolipids in sediments from Great Salt Lake

“…Despite traces of arsenic eluting in the region of arsenosugar phospholipids, neither these compounds nor their possible O-methyl-analogues could be detected by means of accurate mass measurements. The absence of these compounds in GSL sediment extracts can be explained by rapid degradation of arsenosugar phospholipids in microbial-rich sediment environments (Glabonjat et al 2019). In the four GSL sediment samples, we determined concentrations of three major arsenolipids -two hydrocarbons, 1 (0.1-1.9 ng g À1 ) and 3 (0.9-4.4 ng g À1 ), and the phytyl 2-O-methylriboside, 12 (2.3-65.4 ng g À1 ) -based on reversed phase (RP) HPLC-ICPMS data.…”