The dominance of predatory nematodes at the high water level in an Ecuadorian sandy beach

Abstract:

Free-living marine nematodes were sampled monthly from June 2000 to July 2001 at an exposed sandy beach. Samples were taken in dry and rainy season at high tide level on the beach, in order to study the nematode assemblage composition, temporal distribution and their relationship with the environmental factors. Also a comparison with the nematode species at the lower tide level (previous chapter) was analysed. Forty nematode species belonging to 30 genera and 15 families were found. Total nematode densities ranged from 183±28 ind./10 cm 2 (December 2000) to 1488±100 ind./10 cm2 (June 2000), no significant differences between dry (April-December) and rainy season (January-March) were detected. Predators were the most abundant feeding type at the nematode community (47%), although with fluctuating dominance (20-80%). The predatory nematode Enoplolaimus sp. 1 (14%) and Metachromadora sp. 1 (13%) co-dominated, showing density fluctuations over the sampling period (8-311 ind./10 cm2 and 1-302 ind./10 cm2 respectively), but with the highest densities in June 2000 and July 2001. Two temporal nematode species associations were observed: nematodes collected from May to September and those collected from October-April. The k-dominance curves showed highest diversity in June 2001 and lowest diversity in December 2000. Sea Surface Temperature was positively correlated, while salinity was negatively correlated with the total nematode densities. The taxonomic distinctness analysis showed that nematode species registered at the upper and at the lower station on the beach were closely related to each …

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