Distribution, abundance and diversity of Gambierdiscus spp. from a ciguatera endemic area in Marakei, Republic of Kiribati

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Harmful Algae 34 (2014): 56–68, doi:10.1016/j.hal.2014.02.007.Ciguatera is a serious seafood poisoning syndrome caused by the consumption of ciguatoxin-contaminated finfish from tropical and subtropical regions. This study examined the community structure of ciguatera-associated dinoflagellates and the distribution pattern, taxonomy and toxicity of Gambierdiscus spp. from a high-risk area of Marakei, Republic of Kiribati. The genera Gambierdiscus, Prorocentrum, Ostreopsis, Amphidinium and Coolia were present, and generally the former three dominated the dinoflagellate assemblage. Among these three, Gambierdiscus was the most abundant dinoflagellate genus observed at three of the four sites sampled, two of which (Sites 1 and 2) were on the northern half of the island and two (Sites 3 and 4) on the southern half. The following patterns of abundance were observed among sites: (1) Average Gambierdiscus spp. abundance at the northern sites exceeded the southern sites by a factor of 19-54; and (2) Gambierdiscus spp. abundance at shallow sites (2-3 m) exceeded deeper sites (10-15 m). The distribution of Gambierdiscus spp. at Marakei corresponded with previously observed patterns of fish toxicity, with fish from southern locations being much less toxic than fish sampled north of the central channel. DNA sequencing identified three Gambierdiscus species (G. carpenteri, G. belizeanus, G. pacificus) and three previously unreported ribotypes (Gambierdiscus sp. type 4, Gambierdiscus sp. type 5, Gambierdiscus sp. type 6) in the samples; Gambierdiscus sp. type 4 may represent a Pacific clade of Gambierdiscus sp. ribotype 1. Toxicity analyses determined that Gambierdiscus sp. type 4 isolates were more toxic than the Gambierdiscus sp. type 5 and G. pacificus isolates, with toxin contents of 2.6-6.0 (mean: 4.3± 1.4), 0.010 and 0.011 fg P-CTX-1 eq cell-1, respectively. Despite low densities of Gambierdiscus spp. observed at Marakei relative to other studies in other parts of the world, the presence of low and moderately toxic populations may be sufficient to render the western coast of Marakei a high-risk area for ciguatera. The long history of toxicity along the western side of Marakei suggests that large-scale oceanographic forcings that regulate the distribution of Gambierdiscus spp. along the western side of Marakei may have remained relatively stable over that time. Chronic as well as acute exposure to ciguatoxins may therefore pose an important human health impact to the residents of Marakei.Funding for this work was provided by the Centers for Disease Control and Prevention (U01 EH000421), USFDA (F223201000060C), NOAA NOS (Cooperative Agreement NA11NOS4780060, NA11NOS4780028), National Program on Key Basic Research Project of China (973 Program, 2013CB956503), the Nonprofit Research Project for the State Oceanic Administration (China, 201005006-01), and the National Natural Science Foundation of China (41276110)

Medicating the coast in a metropolitan city: Enantiomeric profiles and joint probabilistic risk assessment of antidepressants and antihistamines

Pharmaceuticals are receiving increasing attention as emerging contaminants in the aquatic environment. Herein, we investigated the occurrence of 11 antidepressants, 6 antihistamines and 4 metabolites in treated wastewater effluents, rivers, stormwater, and seawater in Hong Kong, with special focus on chirality. The average levels of ∑pharmaceuticals ranged from 0.525 to 1070 ng/L in all samples and the total annual mass load of target pharmaceuticals in the marine environment of Hong Kong was 756 kg/y. Antihistamines accounted for >80 % of ∑pharmaceuticals, with diphenhydramine and fexofenadine being predominant. The occurrence and enantiomeric profiles of brompheniramine and promethazine sulfoxide were reported in global natural waters for the first time. Among chiral pharmaceuticals, mirtazapine and fexofenadine exhibited R-preference, while others mostly exhibited S-preference, implying that the ecological risks derived from achiral data for chiral pharmaceuticals may be biased. The joint probabilistic risk assessment of fluoxetine revealed that R-fluoxetine and rac-fluoxetine presented different ecological risks from that of S-fluoxetine; Such assessment also revealed that target pharmaceuticals posed only minimal to low risks, except that diphenhydramine posed an intermediate risk. As estimated, 10 % aquatic species will be affected when the environmental level of diphenhydramine exceeds 7.40 ng/L, which was seen in 46.9 % samples. Collectively, this study highlights further investigations on the enantioselectivity of chiral pharmaceuticals, particularly on environmental behavior and ecotoxicity using local aquatic species as target organisms

Pacific Ciguatoxins in Food Web Components of Coral Reef Systems in the Republic of Kiribati

Ciguatera fish poisoning (CFP) is a foodborne illness caused by consumption of coral reef fishes contaminated by ciguatoxins (CTXs); of the known CTX congeners, the Pacific ciguatoxins (P-CTXs) are the most toxic. Little is known about the trophodynamics of P-CTXs in coral reef systems. The present study explores the distribution, transfer, and trophic magnification of P-CTX-1, -2, and -3 in coral reef systems with high (ciguatoxic) and low (reference) ciguatoxicity in a CFP-endemic nation by use of liquid chromatography-tandem mass spectrometry (LC-MS/MS). In ciguatoxic coral reef systems, P-CTXs were detected in 54% of herbivorous fishes [total P-CTXs <0.500–1670 pg/g wet weight (ww)], 72% of omnivorous fishes (<0.500–1810 pg/g ww), and 76% of carnivorous fishes (<0.500–69 500 pg/g ww), as well as a lobster (Panulirus penicillatus; 2.36 pg/g ww) and an octopus (Octopodidae; 2.56 pg/g ww). The dominant P-CTXs in grazers and piscivorous fishes were P-CTX-2 and -1, respectively. No significant correlation between P-CTX levels and lipid content in three target predatory fishes indicated that accumulation of P-CTXs does not depend on fat content. A weak but significant positive relationship was observed between δ¹⁵N and P-CTX-1 levels, but further investigation is required to confirm its biomagnification potential