Sedentary polychaetes are conspicuous with numerous species in marine environments. They can also be a major component of fouling communities. As fouling organisms, they can be divided into four families (Serpulidae, Spirorbidae, Sabellidae and Terebllidae) with a total of 55 species identified, of which the dominant species are Hydroides elegans, H. ezoensis, H. diramphus, H. norvegicus, H. operculatus, Pomatoleios kraussii, Serpula vermicularis, Spirobranchus polytrema, S. tetraceros, Ficopomatus enigmaticus and Thelepus cincinnatus.
Sedentary polychaetes usually live in tubes, which they themselves secrete. Tubes are either attached to surfaces or to each other forming tangled batches; such tubes are difficult to remove even when the occupying worms have died. Their larvae can settle on various underwater man-made substrata, and post-settlement tube growth may cause serious impairment problems such as adding weight to buoys, decreasing ship speed (more fuel consumption, so increasing CO₂ emission), blocking seawater pipelines and aquaculture nets. Fouling sedentary polychaetes are widely distributed in tropical, subtropical and temperate waters. However, they are not homogeneously distributed over the different biogeographical regions. In the Pacific Ocean the common species are Hydroides elegans, H. ezoensis, H. centrospina, H. longistylairs, H. multispinosa, H. prisca, Serpula cf. hartmanae and S. tetratropia. Whereas Ficopomatus uschakovi, Hydroides heterocerus, H. minax and Spirobranchus semperi are only found in the Indian Ocean and Hydroides brachyacanthus, Serpula concharum, Spirobranchus lamarcki and Pseudovermilia occidentalis mainly occur in the Atlantic Ocean.
Fouling sedentary polychaetes range from shallow coastal habitats to deep water. However, most previous work is restricted to coastal waters as studies in the deep ocean are rare. Moreover, different species prefer particular substrata. For example Pomatoleios kraussii and Hydroides operculatus tend to settle on the hulls of ships, whereas H. ezoensis and H. diramphus are generally abundant on quay and aquaculture equipment. Understanding their settlement processes is likely to contribute to the development of novel antifouling technology.
Sedentary polychaetes are appropriate representative animals to evaluate the impact of environmental factors on marine ecological systems and from the viewpoint of antifouling studies, they are also ideal testing models. Therefore, further work should be focused on the aspects of larval development and settlement mechanisms of the dominant species. Moreover, with the increase in oceanic development and utilization activities, more man-made facilities now occur in deeper and colder waters. Lack of information on fouling sedentary polychaetes in such environment means urgent further studies are now necessary.
Due to the limitations of traditional taxonomic methods it is sometimes difficult to identify related polychaete species effectively. Modern genetic technology should provide the answers. Furthermore, some sedentary polychaetes can be easily transported by ship to new environments. As such alien invasive species they can cause serious ecological problems. Based on the reasons mentioned above future work should address the issues of taxonomy and invasive species.