Distribution and abundance of marine nematodes on the kelp Macrocystic integrifolia

The species and distribution of nematodes on the kelp Macrocystic integrifolia Bory, in the Bamfield region of Barkley Sound, British Columbia, Canada were examined. Nine species (belonging to six families) of nematodes were found on the kelp blades. Three species (Monhystera disjuncta, M. refringens and Prochromadorella neapolitana) comprised 91–99% of the nematode fauna and occurred in all monthly samples from July 1978 to November 1979. The three dominant species exhibited seasonal density differences. P. neapolitana occurred mostly in the summer, M. refringens abundance peaked from July to October and M. disjuncta was relatively abundant throughout the year. The other species contributed little to the overall abundance and distribution patterns. All three species occurred in greatest abundance on the lower and middle blades of M. integrifolia in the deep end of the kelp bed. Very few individuals occurred on the upper blades. Nematode distribution on M. integrifolia appeared to be related to blade age and the associated food sources on the blade.