Arsenic and selected elements in inter‐tidal and estuarine marine algae, south‐east coast, NSW, Australia

Abstract

The cycling of arsenic in marine inter-tidal and estuarine algae was examined by measuring total arsenic concentrations and arsenic species in marine inter-tidal and estuarine algae from the south-east coast, NSW, Australia. A range of elements required for metabolism in photosynthetic organisms were also measured to determine if any relationship between these elements and arsenic concentrations occurred. Total arsenic concentrations varied between classes of algae: red macro algae, 4.3-24.7 µg g −1 ; green macro algae, 8.0-11.0 µg g −1 ; and blue green algae, 10.4-18.4 µg g −1 . No significant relationships were found between arsenic concentrations and concentrations of iron, cobalt, copper, manganese, molybdenum, magnesium, phosphorus and zinc. Distinct differences between algal classes were found for the proportion of arsenic species present in the lipid and water-soluble fractions, with green algae having a higher proportion of arsenic in lipids (19-44%) than red intertidal (5-34%) or estuarine algae (10-24%). Acid hydrolysis of lipid extracts revealed dimethyl arsenic, glycerol arsenoribose and two unknown cation based arsenolipids. Within water-soluble extracts, red macro algae and blue green algae contained a greater proportion of arsenic as inorganic and simple methylated arsenic species compared with green macro algae, which contained predominantly glycerol arsenoribose. Arsenobetaine, arsenocholine and tetramethyl arsonium ion were also present in some water-soluble extracts, but are not normally identified with algae and are probably due to the presence of attached microscopic epiphytes. Residue extracts contained predominantly inorganic arsenic, most likely associated with insoluble constituents of the cell. Marine algae contained lipids with arsenic moieties that may be precursors for arsenobetaine. Specifically, the presence of dimethylated arsenoribose-based arsenolipids can transform to arsenobetaine via intermediates previously identified in marine organisms.

LC–ICP–MS analysis of arsenic compounds in dominant seaweeds from the Thermaikos Gulf (Northern Aegean Sea, Greece)

“…38 Marine algae contain most of their arsenic in the form of arsenosugars. In recent decades, a number 39 of studies have described the mechanisms of the transformation and accumulation of arsenicals, as 40 well as correlations among arsenosugars and algal orders (Thomson, et al, 2007). Furthermore, 41 there have been several reports of the potentially toxic character of such organoarsenic compounds In the present study, total arsenic content and arsenic species are determined in 10 seaweed species 50 collected in three sampling sites in the Thermaikos Gulf (Greece).…”

Cyanobacteria produce arsenosugars

“…Microbes living in marine environments are likely to have an ability to produce arsenosugars, [16,17] and several studies have centred on the role of marine microbes in the possible production and biodegradation of arsenosugars. [18][19][20] Thus, identification of As metabolites in microbes grown in pure culture, such as eukaryotic microalgae and prokaryotic cyanobacteria, has been performed to confirm biotransformation mechanisms of As after experimental exposure to inorganic As species. Previous reports generally indicate that microalgae (not only marine species (Dunaliella tertiolecta and Phaeodactylum tricornutum) [17] but also freshwater ones (Chlorella vulgaris, [21] Chlorella sp., [22] Chlamydomonas reinhardtii [23,24] and Monoraphidium arcuatum [22] ) can produce arsenosugars from incorporated As V by reduction and methylation processes, and that cyanobacteria (freshwater species, Microcystis sp.…”

Concentration and Biomagnification of Heavy Metals in Biota of the Coastal Marine Areas of Tanzania

“…to accumulate arsenic from the environment as compared to other species of macroalgae in other stations. This idea is complemented by discussion given by Thomson, D., et al [43] who reported that arsenic concentration and which are important primary producer in marine food chains. Rahman, M. A., et al [44] reported that total arsenic concentrations varied between classes of algae, and significant differences between algae classes and habitats were found for the proportion of As species.…”

“…Other researchers have reported that arsenic and/or its metabolites is a chemical that bioaccumulates in tissues of aquatic organisms but does not biomagnify, rather it biodilutes in the aquatic food chain [31,[48][49][50]. Yet Thomson, D., et al [43] report that, dietary exposure to arsenic from aquatic foods would not be a serious problem for humans due to its biodiminution and biotransformation to less toxic organo-As species.…”