Toxicological Perspective on Climate Change: Aquatic Toxins

Abstract

In recent years, our group and several others have been describing the presence of new, not previously reported, toxins of high toxicity in vectors that may reach the human food chain. These include tetrodotoxin in gastropods in the South of Europe, ciguatoxin in fish in the South of Spain, palytoxin in mussels in the Mediterranean Sea, pinnatoxin all over Europe, and okadaic acid in the south of the U.S. There seem to be new marine toxins appearing in areas that are heavy producers of seafood, and this is a cause of concern as most of these new toxins are not included in current legislation and monitoring programs. Along with the new toxins, new chemical analogues are being reported. The same phenomenom is being recorded in freshwater toxins, such as the wide appearance of cylindrospermopsin and the large worldwide increase of microcystin. The problem that this phenomenon, which may be linked to climate warming, poses for toxicologists is very important not only because there is a lack of chronic studies and an incomplete comprehension of the mechanism driving the production of these toxins but also because the lack of a legal framework for them allows many of these toxins to reach the market. In some cases, it is very difficult to control these toxins because there are not enough standards available, they are not always certified, and there is an insufficient understanding of the toxic equivalency factors of the different analogues in each group. All of these factors have been revealed and grouped through the massive increase in the use of LC-MS as a monitoring tool, legally demanded, creating more toxicological problems.

Structural Diversity, Characterization and Toxicology of Microcystins

“…After almost two decades of structural analysis of toxic peptides from the colonial bloom-forming cyanobacterium M. aeruginosa, Botes et al [15][16][17][18][19] and Santikarn et al [20] provided structural details of these toxins with the general structure of: cyclo-(D-Ala 1 -X 2 -D-Masp 3 -Z 4 -Adda 5 -D-γ-Glu 6 -Mdha 7 ) ( Figure 1) in which X and Z are variable L-amino acids, D-Masp 3 is D-erythro-β-methyl-isoaspartic acid, and Mdha is N-methyldehydroalanine. The β-amino acid Adda, (2S,3S,4E,6E,8S,9S)-3-amino-9-methoxy-2,6,8trimethyl-10-phenyldeca-4,6-dienoic acid, is the most unusual substructure, and has not been reported elsewhere in nature apart from in the closely related group of toxic pentapeptides, the nodularins.…”

“…Ion trap CID involves longer time scales and a larger number of lower energy collisions, as well as offering the potential for multiple stages of MS/MS (MS n ). Here, structural elucidation is done by constructing a fragmentation tree where the origin of lower mass product ions can be established in higher order experiments (e.g., MS 3 or MS 4 ) in relation to higher-mass product ions observed in MS 2 . The principal limitation of ion trap dissociation is the 1/3 rule, stating that product ions of less than 1/3 the m/z of a selected precursor ion cannot be isolated for detection.…”

“…There are an increasing number of warnings about toxic cyanobacterial blooms observed worldwide and global warming is thought to stimulate their development in eutrophic waters [1][2][3][4][5]. These blooms are often accompanied by production of a variety of cyanotoxins generally classified according to the target organs: hepatotoxins (liver), neurotoxins (nervous system), and dermatotoxins (skin).…”

Physiological responses of the freshwater N2‐fixing cyanobacterium Raphidiopsis raciborskii to Fe and N availabilities

“…The bloom-forming freshwater filamentous cyanobacterium, Raphidiopsis raciborskii [previously named Cylindrospermopsis raciborskii (Aguilera et al, 2018)], is of increasing global environmental and social concerns because of its adverse effects on the quality of drinking water reservoirs and lakes as a result of the potential generation of toxic metabolites such as cylindrospermopsin (CYN) and saxitoxins (Hoff-Risseti et al, 2013;Lei et al, 2014;Botana, 2016;Martin et al, 2018). In recent decades, this diazotrophic cyanobacterium has spread from its native tropical region to subtropical and temperate zones (Burford et al, 2016;Burford et al, 2018).…”

“…In recent decades, this diazotrophic cyanobacterium has spread from its native tropical region to subtropical and temperate zones (Burford et al, 2016;Burford et al, 2018). The rapid expansion of R. raciborskii may be due to several possibly synergistic factors including global climate change (Botana, 2016), strong physiological adaptability of this microorganism to low light and temperature (Antunes et al, 2015;Kehoe et al, 2015) and flexible acquisition of nutrients, particularly nitrogen (N) (Willis et al, 2016a). Although the N 2 -fixation rate of R. raciborskii is lower than ammonium and nitrate uptake rates and accounts for less than 10% of total N assimilation by this organism, N 2 -fixation by R. raciborskii plays a vital role in regulating the physiological adaptation of this organism in N-fluctuating environments.…”