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et al.. The use of stable isotopes to measure the ingestion rate of 1 potentially toxic benthic dinoflagellates by harpacticoid copepods. Journal Abstract 20 2 Phycotoxins synthesized by benthic dinoflagellates are known to bioaccumulate in 21 macrofauna and hence represent a risk for human health. However, the presence of toxins 22 synthesized by benthic dinoflagellates in smaller marine organisms than macrofauna has not 23 been considered despite the fact that such small organisms have an important ecological role 24 in the benthic food web. This present study quantified, for the first time, the trophic 25 relationship between benthic dinoflagellates and meiofauna by using stable isotope enriched 26 dinoflagellates during ingestion experiments. Results showed that harpacticoid copepods were 27 not able to discriminate, during ingestion, between the potentially toxic cells of Ostreopsis cf. 28 ovata and the non-toxic cells of Amphidinium cf. carterae, even when another food resource, 29 such as diatoms (e.g. Odontella sp.), was provided (Kruskal Wallis test, p > 0.05). 30 31 Introduction 32

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For the first time, distribution of epiphytic dinoflagellates was studied in Saint Martin Island (Lesser Antilles) during the cyclonic season (between September 1 st and 3 rd 2015). The present study provides a semi-quantitative analysis because the fresh weight of each macrophyte was estimated around 10 g. The identified genera were: Ostreopsis, Prorocentrum, Coolia, Amphidinium, and Gambierdiscus in order of decreasing abundance. Highest average abundance values of the genera Ostreopsis and Amphidinium were hosted by macrophytes of the Phaeophyceae group with ca. 15,000 and 60 cells g -1 respectively. Epiphytic Coolia cells were mainly observed on seagrasses with the highest average abundance value of ca. 1000 cells g -1 whereas the genera Gambierdiscus and Prorocentrum were principally associated with Florideophyceae with the highest average abundances of ca. 70 and 1500 cells g FW -1 respectively. This preliminary study indicates the most relevant locations to survey the biodiversity of potentially toxic epiphytic dinoflagellates in Saint Martin Island.

Ciguatera fish poisoning (CFP) is one of the most common causes worldwide of marine poisoning associated with fish consumption from tropical areas. Its incidence is underreported. CFP cases seem to increase with grouped cases reported during summer. Exposure to ciguatoxin, the toxin responsible for CFP with sodium-channel agonistic, cholinergic, and adrenergic activities, may result in a large spectrum of manifestations. We aimed to describe the clinical characteristics, management, and outcome of CFP in Martinique, French West Indies. We conducted an observational retrospective single-center study for six years (October 2012 to September 2018) including all CFP patients managed by the prehospital medical services, admitted to the university hospital emergency department, or declared to the regional health agency. One hundred and forty-nine CFP patients (81females/63males; median age, 46 years [interquartile range, 34-61]) were included. Acute features consisted of general (91%; mainly, myalgia pruritus, and asthenia), gastrointestinal (90%; mainly diarrhea, abdominal pain, and nausea), neurological (72%; mainly, paresthesia, dysgeusia, and impairment of hot/cold feeling), and cardiovascular manifestations (22%; bradycardia, hypotension, and heart conduction disorders). Management was supportive. No patient died but symptoms persisted in 40% of the 77 patients with follow-up on day 15. CFP was mainly attributed to the ingestion of trevallies (59%), snappers (13%), and king mackerels (8%) with collective contaminations (71%). Unusual fish (tuna, salmon, and spider conchs) were suspected in rare cases. Ingestion of trevallies was associated with significantly higher persistent symptoms (odds ratio, 3.00; 95% confidence interval, [1.20-8.00]; p=0.03). CFP incidence was 0.67 cases per 10,000 patient-years in Martinique over the study period. To conclude, CFP represents an increasing public health issue in Martinique like in other Caribbean islands. Patients present usual but possibly life-threatening features. The outcome is excellent despite frequently prolonged manifestations.

For the first time, distribution and abundances (cells per gram of fresh macrophyte weight) of potentially toxic benthic dinoflagellates were studied around Guadeloupe (20 sites) and Martinique (six sites) islands (Lesser Antilles, Caribbean Sea). Benthic dinoflagellates were identified at the genus level and cell counts were undertaken on different host species of macroalgae and seagrasses. Abundance values of potentially toxic benthic dinoflagellates were one order of magnitude higher in Guadeloupe than in Martinique. The highest abundances of benthic dinoflagellates were found in the northern part of Guadeloupe Island, while their distribution was more homogeneous in Martinique. Ostreopsis was the dominant genus in Guadeloupe and Martinique. Regarding biotic substrate preferences, Phaeophyceae hosted the highest total abundances of benthic dinoflagellates on both islands, while the lowest total abundances were observed on Ulvophyceae in Guadeloupe and Florideophyceae in Martinique. The genus Gambierdiscus, known as the causal agent of the ciguatera fish poisoning (CFP), developed on all macrophyte groups on both islands without showing any preferences towards biotic substrates. The presence of this potentially harmful dinoflagellate genus in both islands could explain the existence of local cases of CFP in Guadeloupe and Martinique islands.