Marine Biology (2+1)

Mollusca

Among the molluscs some of the genera such as Mytilus, Modiolus, Perna, Anomia, Saxicava, Ostrea, Cardium, Musculus, Lubitina, Avicula and Patella are represented. Of all the molluscs, the mussels are the most important common and dominant foulers. They settle heavily, especially in the pipe systems carrying sea water on board, and obstruct the flow of water. The constant flow of water is conducive to their large-scale settling and rapid growth. The larvae of these mussels settle inside the pipes especially around the various isolating valves in the system, preventing their proper functioning. This may sometimes enter condenser tubes, refrigerator cooling systems, etc., causing serious trouble. In the lower levels of the intertidal areas, these mussels settle heavily on any of the man-made solid substratum and outcompete all other fouling communities.

Among crustaceans, the barnacles are the most dominant representatives of the fouling community. There are more than 100 species of barnacles which can be called foulers. They are adapted to attach themselves to a very wide range of substrates. It was found that no surface could be devised which is so smooth, so slippery or so soft that a barnacle cyprid could not attach. Important species represented are Balanus amphitrite, B. eburneus, B.tintinnabulum, B.amaryllis, Chthamalus stellatus, Tetraclita purpurascens and Lepas anatifera. Amphipods such as Corophium, Erichthonius, and Gammarus and the isopod Sphaeroma are also represented in the fouling community.

Ascidians are well-represented in the temperate as well as tropical waters. Important genera include Botryllus, Botrylloides, Molgula, Ciona, Polycarpa, Herdmania, Diplosoma and Diandrocarpa.

In tropical waters around India, fouling of underwater surfaces takes place at all times of the year, unlike in the colder waters, where it is more pronounced during the warmer months. Another feature notices among the fouling organisms of these waters is that some of them show distinct seasonal maxima of frequency, whereas in other seasons they are rare or entirely absent. These rhythms are mainly influenced by temperature and reproductive cycles of the concerned species. Heavy accumulations of foulers, particularly balanids can inhibit to some extent the attack of marine borers like teredines, Sphaeroma and Martesia. It is reported that a decrease of foulers is usually attended whit an increase in borer activity