The nematofauna from the seaweeds Sargassum polyceratium Montagne, Hypnea musciformis Kiietzing,Padina gymnospora Kiietzing and the seagrass Halodule wrightii Ascherson was studied in March 2001, at Pedra do Xareu, Pernambuco, Brazil, in order to investigate the associations of organisms, as well as the relation between the plant architecture and the associated fauna. Soft sediments adjacent to phytal environments were also investigated. Thirty-eight genera were found, including two new records
(Odontanticoma sp. and Wieseria sp.) for the Brazilian coast. Multivariate analyses were carried out in
order to verify the relation between nematode assemblages on plants and in sediments. The results showed
that these assemblages were different in structure and composition between macrophytes and sediments.
They were different in structure but not in composition among macrophytes, so the nematode biodiversity
was related to the structural features of macrophytes' habitats.