Vertical distribution and feeding types of nematodes from Chetumal Bay, Quintana Roo, Mexico

The vertical distribution and feeding type of nematodes in sediments of Chetumal Bay, Mexico, were studied in five intertidal transects along the urbanized zone in June and December 1995. Sediments were collected with a PVC corer to 6-cm sediment depth and cut immediately into three equal 2-cm depth fractions. Nematode density varied from 7.4 x 10(3) to 5.3 x 10(5) m(-2) in June and from 1.7 x 10(4) to 7.2 x 10(5) m(-)2 in December. In June, the epistrate feeder Pseudochromadora sp. was the most abundant in the deepest sediment fraction (4-6 cm), whereas epistrate feeders, Neotonchoides sp., Desmodora sp., and the deposit feeder Bathylaimus australis were dominant in the top most sediment (0-2 cm). In December, deposit feeders, Desmolaimus zeelandicus, Parodontophora sp., and the epistrate feeder Oncholaimus oxyuris were the most abundant in the deepest sediment, whereas Neotonchoides sp. and Pseudochromadora sp. dominated the first 2 cm of sediments. Highest nematode density was recorded in the uppermost sediment layer (0-2 cm). Feeding types showed different abundance among transects and between months. There was a seasonal change in vertical distribution of nematodes, with the highest abundance in the deepest sediment layer in December, possibly due to the effect of wind waves on sediments of Chetumal Bay. The trophic composition of the nematode fauna in Chetumal Bay showed a dominance of deposit feeders and epistrate feeders, most likely in response to organic enrichment that is typical of eutrophic environments.