A checklist of aquatic nematodes from Cuban Archipelago.

The diversity of free-living aquatic nematodes is largely unknown for the Gulf of Mexico and Caribbean Sea. The Cuban Archipelago is an important part of this because of its large area and diversity of habitats. We analyzed the free-living nematodes from 83 sites from seven aquatic habitats around Cuba, to produce a checklist for many habitats, including seagrass meadows, coral degradation zones, algal turf, bare sands, unvegetated muds, freshwater and anchihaline caves, and deep-sea sediments. The checklist contains 469 species, 229 genera, 50 families, and 9 orders. Chromadorida, Enoplida, and Monhysterida were the best represented orders with 112, 100, and 83 species respectively. The most abundant species were Euchromadora vulgaris, Terschellingia longicaudata, Desmodora pontica, Sabatieria pulchra , and Epsilonema sp. Most of the listed species were new records for the region. There were differences in the number of species recorded in each habitat type, with seagrass meadows having 280 species, coral degradation zones having 139 species, deep waters having 116 species, algal turf having 114 species, bare sands having 100 species, unvegetated muds having 78 species, freshwater caves having 19 species, anchihaline caves having 16 species, and freshwater streams having 6 species. The checklist is the most comprehensive recent report of the diversity of free-living nematodes in the regions of Gulf of Mexico and Caribbean Sea. The reported diversity is higher than many other regional checklists likely reflecting the intense sampling effort and the variety of microhabitats in Cuban Archipelago.

Diversity patterns of free-living nematode assemblages in seagrass beds from the Cuban archipelago (Caribbean Sea).

Diversity patterns of free-living marine nematodes in tropical seagrass beds are understudied. Here, we describe the species richness and assemblage composition of nematodes in 13 seagrass sites covering the whole Cuban archipelago. Nematodes were collected from Thalassia testudinum seagrass beds and identified to species level. We provide a checklist of nematode species from seagrass beds. The species richness of nematode assemblages is high, with 215 species, 138 genus, 35 families, seven orders and two classes. That γ-diversity is higher than other studies and points to seagrass beds as diversity hotspots of free-living marine nematodes. Local species richness in seagrass bed sites is about 57 ± 17 species and broadly similar across the sites, despite the environmental heterogeneity. The geographical distance plays a weak, but significant, role on the decay of similarity likely affected by limited dispersal of nematodes. The pairwise similarity values, related to poor-coloniser nematodes, were twice more affected by the distance than those related to good-colonisers, possibly due to differential success of transport and settlement.

Effects of organic enrichment on nematode assemblages in a microcosm experiment.

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.