Sponges growing on bamboo float used to culture Kappaphycus alvarezii
Oysters and Sponges
Biofoulers in Tuticorin Bay, Tamil Nadu, India
Sacred Heart Marine Research CentreSister Avelin Mary, Director
|Sea Anemone||Anemonia sp.|
|Sponges||Cliona celata Grant (boring sponge), Spongia officinalis|
|Plate corals||(species to be determined)|
The barnacle (Balanus amphitrite) is the most serious fouler faced by pearl oyster farmers in India. This barnacle settles and grows on the shells of the pearl oysters, while boring organisms riddle through the shells, rendering them weak and fragile. B. Amphitrite is perhaps the most ubiquitous fouler worldwide having been carried by ships from port to port for millennia. In Karrapad Cove, Tuticorin Bay (India), fouling is year round, with some seasonal trends as shown in the figure below.
Seasonal changes in amount of barnacle, algal and tubeworm fouling on
the surface of 3 inch x 8 inch PVC panels between 2009 and 2010 under
30-day static immersion in Karrapad Cove, Tuticorin Bay, India.
Following the barnacle in terms of fouling are the mollusks, Avicula vexillum and Crassostrea sp. The tubiculous polychaetes (Hydroides sp.) have not been found to be significant, and they appeared in pearl oyster farms only in January.
B.neritina is considered a potential fouling organism. The colonies are erect and brush-like. Each colony is composed of a set of polymorphic individuals. Only these morphs are capable of feeding, and produce gametes. Embryonic development occurs withn a complex brood chambers and larvae are released at the conclusion of the embryonic period in response to an increase in light intensity. B.neritina larvae are released from brood sacks with a visible light shock and concentrated by the attraction to a fiber optic light source. The larvae are non-feeding and free-swimming only a few hours before settlement and metamorphosis. The major organs sensory units are the corona, pyriform groove, internal sac and the apical sense organ. The larva of B.neritina is avoid, about 350 μm high and 250 μm in diameter.
The worm is about 3 inches in length. The crown of the branchiae is long and slender, radiating from the united base. It builds calcareous tube often in coiled masses. The projecting heads have two fan shaped series of branchiae with plume like pinnae fifteen to eighteen in number with a color pattern variegated with pink. A dorsal filament on each fan has been modified into an operculum, one of which is fully developed, the other rudimentary. It is seen to be a double, handsomely patterned structure composed of two super imposed star like discs, the lower being the larger and made up of twenty five or more pieces like a vase or flower cup surmounting a stem. The body of this species is of a reddish orange colour. Hydroides elegans is a tough and cosmopolitan serpulid fouler.
Sea anemones inhabit coastal waters throughout the world but are particularly abundant in tropical oceans. They commonly live attached to rocks, shells and submerged timbers. Some forms burrow in mud or sand. The shape of the body is often related to the habitat in which the sea anemone lives.
Very common on calcareous structures (shell,coral, calcerous algae, barnacles). Excurrent and incurrent papillaeproject out of substratum in living condition, but are highly contractile and only pores on substratum visible out of water. Pores are 0.5-2.0 mm. in diameter but subject to considerable variation. Larger pores accommodate excurrent and smaller, incurrent papillae. Papillae are green, golden yellow or red when live. Chambers found inside substratum are small, 2 to 5 mm. in diameter, but subject to considerable variation. All members, at least in early life, bore into calcareous matter and thus, are a menace to commercially important mollusks and coral reefs. There are 32 species belonging to this family in the Indian seas (Thomas 1979). They cause considerable damage to the pearl, chalk, and oyster beds of the Gulf of Mannar and Palk Bay in India.
The sponge is massive, globular or irregular in the initial state, turning to a flat-topped structure in advanced stages of development. This particular sponge usually grows upright on the hard objects found at the sea bottom. The rough surface of the sponge also attracts foulants and bacteria alike. Hence, to protect them from fishes and foulants, they have to produce icthyotoxic and antifouling compounds. Extensive cavities found in this sponge are utilized by other animals such as amphipods, isopods, and stomatopods as shelter. Bivalve mollusk (Vulsella vulsella Lin) is seen buried into the body of the sponge. Why these animals are unaffected by chemicals produced by this sponge is unknown.
Plate corals have never been observed at the test site until 2010. They appear white and flattened, tending to cover a small area on uncoated or panels coated with protective coatings without antifoulings. The plate corals grow fast for a month and slow down or vanish altogether. Since this is the first year it has been observed, their occurrence may represent some environmental changes in the habitat enabling them to colonize surfaces.
The figure shows the percentage of such panels under immersion testing with coral fouling. Only a small proportion of the panels, at best 200% at peak occurrence in November 2010. The fouling appears seasonal and abruptly terminates. We will update the graph if they reappear again later in 2011.
Incidence of plate corals in control test panels under static
immersion in Tuticorin Bay, India.
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