Assessment of the Chemical Diversity and Potential Toxicity of Benthic Cyanobacterial Blooms in the Lagoon of Moorea Island (French Polynesia)

Abstract

In the last decades, an apparent increase in the frequency of benthic cyanobacterial blooms has occurred in coral reefs and tropical lagoons, possibly in part because of global change and anthropogenic activities. In the frame of the survey of marine benthic cyanobacteria proliferating in the lagoon of Moorea Island (French Polynesia), 15 blooms were collected, mainly involving three species—Anabaena sp.1, Lyngbya majuscula and Hydrocoleum majus-B. Their chemical fingerprints, obtained through high performance liquid chromatography combined with UV detection and mass spectrometry (HPLC-UV-MS) analyses, revealed a high extent of species-specificity. The chemical profile of Anabaena sp.1 was characterized by three major cyclic lipopeptides of the laxaphycin family, whereas the one of L. majuscula was characterized by a complex mixture including tiahuramides, trungapeptins and serinol-derived malyngamides. Toxicity screening analyses conducted on these cyanobacterial samples using Artemia salina and mouse neuroblastoma cell-based (CBA-N2a) cytotoxic assays failed to show any toxicity to a degree that would merit risk assessment with regard to public health. However, the apparently increasing presence of blooms of Lyngbya, Hydrocoleum, Anabaena or other benthic cyanobacteria on coral reefs in French Polynesia encourages the implementation of ad hoc monitoring programs for the surveillance of their proliferation and potential assessment of associated hazards.

Thirtieth Anniversary of the Discovery of Laxaphycins. Intriguing Peptides Keeping a Part of Their Mystery

“…Like their cyclic structural analogues, laxaphycin A2 and [D-Val 9 ]laxaphycin A, these new acyclolaxaphycins A were not found in samples of Anabaena sp. collected by Bonnard et al for their study on the toxicity of cyanobacterial blooms, thus highlighting that laxaphycin production might be seasonally affected or dependent on the environmental conditions [28]. In 2015, upon examination of an extract of A. torulosa, Bornancin et al also found two acyclic laxaphycins, B and B3, that differ from their cyclic homologs by an m/z value 18 amu higher [32].…”

“…These two new cyclic laxaphycin A were not found in other samples of Anabaena sp. collected at different locations in the lagoon of Moorea [ 28 ]. The production of these peptides cannot yet be explained.…”

“…Like their cyclic structural analogues, laxaphycin A2 and [ d -Val 9 ]laxaphycin A, these new acyclolaxaphycins A were not found in samples of Anabaena sp. collected by Bonnard et al for their study on the toxicity of cyanobacterial blooms, thus highlighting that laxaphycin production might be seasonally affected or dependent on the environmental conditions [ 28 ].…”

“…These two new acyclolaxaphycins B were not found in other samples of Anabaena sp. collected at different locations in the lagoon of Moorea, as in the case of the new laxaphycins A mentioned above [ 28 ]. Recently, two acyclolaxaphycins were isolated from the sea hare Stylocheilus striatus that feeds on the cyanobacterium A. torulosa , producing laxaphycins [ 33 ].…”

“…However, the ecological role of laxaphycins remains unclear [ 9 ]. Laxaphycin A, hormothamin A, and lyngbyacyclamides are non-toxic on brine shrimp Artemia , while laxaphycin B is lethal [ 28 , 29 , 39 ]. Hormothamnin A is, on the other hand, toxic on the goldfish Carassius carassius with an LD50 of approximately 5 μg/mL [ 29 ].…”