a b s t r a c tSpatial and temporal biodiversity patterns of free-living marine nematodes were studied in Cienfuegos Bay, a tropical semi-enclosed basin in the Caribbean Sea. Taxonomic (to species level) and functional (biological trait) approaches were applied for describing the assemblage structure and relating it to abiotic environment based on a sampling scheme in six subtidal stations and three months. Biological trait approach added relevant information to species pattern regarding relationships between diversity patterns and the abiotic environment. The most common morphotypes were deposit feeding nematodes, with colonising abilities of 2-3 (in a scale from 1 to 5), tail conical cylindrical or filiforme and body slender; and their abundance were correlated with depth, organic matter and silt/clay fraction. In spite of a high turnover of species, functional diversity of assemblages did not change notably in space and time. A result probably due to sampling of the habitat pool of species and to low heterogeneity of the studied muddy bottoms. Chemical pollution (organic enrichment and heavy metals) and hydrodynamic regime possibly drove the biodiversity patterns. Spatial distribution of assemblages support the existence of two well differentiated basins inside the bay, the northern basin more polluted than the southern one. The low hydrodynamic regime would determine a poor dispersion of nematodes resulting in high spatial variance in the assemblage structure; and also the associated hypoxic conditions and pollutants in sediments can explain the dominance of tolerant nematode species such as Daptonema oxycerca, Sabatieria pulchra, Terschellingia gourbaultae, and Terschellingia longicaudata. A comparison of spatialtemporal patterns of biodiversity between Cienfuegos Bay and other semi-enclosed bays in temperate regions suggests several similarities: nematode assemblages are strongly influenced by anthropogenic disturbance, temporal trends are weak or overridden by spatial ones, and few cosmopolitan genera/ species tolerant to pollution and hypoxic conditions are dominant.

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In Cuba, ciguatera poisoning associated with fish consumption is the most commonly occurring non-bacterial seafood-borne illness. Risk management through fish market regulation has existed in Cuba for decades and consists of bans on selected species above a certain weight; however, the actual occurrence of ciguatoxins (CTXs) in seafood has never been verified. From this food safety risk management perspective, a study site locally known to be at risk for ciguatera was selected. Analysis of the epiphytic dinoflagellate community identified the microalga Gambierdiscus. Gambierdiscus species included six of the seven species known to be present in Cuba (G. caribaeus, G. belizeanus, G. carpenteri, G. carolinianus, G. silvae, and F. ruetzleri). CTX-like activity in invertebrates, herbivorous and carnivorous fishes were analyzed with a radioligand receptor-binding assay and, for selected samples, with the N2A cell cytotoxicity assay. CTX activity was found in 80% of the organisms sampled, with toxin values ranging from 2 to 8 ng CTX3C equivalents g −1 tissue. Data analysis further confirmed CTXs trophic magnification. This study constitutes the first finding of CTX-like activity in marine organisms in Cuba and in herbivorous fish in the Caribbean. Elucidating the structure-activity relationship and toxicology of CTX from the Caribbean is needed before conclusions may be drawn about risk exposure in Cuba and the wider Caribbean. Key Contribution:This study constitutes a first investigation of fish contamination with ciguatoxines (CTXs) in Cuba. CTXs were present at all levels of the food web, including in widespread Caribbean herbivores generally considered safe for consumption. We discuss remaining analytical challenges to assess exposure and hence to develop effective management strategies for the associated foodborne disease. Supplementary Materials:The following are available online at http://www.mdpi.com/2072-6651/11/12/722/s1: Figure S1: Toxicity of sampled fish and invertebrate specimens. Horizontal bars represent median RBA analysis among specimens, boxes extend from the 25th to 75th percentiles and whiskers represent min to max specimens RBA values. The horizontal line corresponds to the RBA limit of quantification (LOQ = 1.5 ng CTX3C equiv. g-1). RBA-specimens are not shown. Shaded areas indicate fish species banned by Cuban regulation. Author Contributions: Conceptualization, C.M.A.-H.; Data curation, L.

Marine nematodes from subtidal tropical sediments of Cienfuegos Bay were subjected to organic enrichment in a microcosm experiment for 32 days. Nematode abundance and diversity decreased, and the taxonomic and trophic structure was altered. The results suggested that the nematodes were not food limited in the microcosms or in their natural environment. Chemical stressors such as ammonia and hydrogen sulfide derived from reduced conditions in sediments may be important factors affecting the assemblages. Hypoxic conditions occurred in all experimental units, as well as in the field, suggesting a nematode assemblage adapted to naturally enriched sediments. However, tolerant species showed a grade of sensitivity to reduced conditions. In agreement with the model by Pearson and Rosenberg (1978), we predict that further organic enrichment in sediments from Cienfuegos Bay may cause a phase shift into a strongly depleted benthic fauna and reduced conditions in water and sediments.

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