Abstract
Shipworms are important decomposers of wood, especially in mangrove forests where productivity is high. However, little emphasis has been given to the activity of shipworms in relation to the export of nutrients from mangroves to adjacent coastal areas. As a first step to obtaining such information, the frequency of colonized mangrove driftwood as well as shipworm density and length were studied by collecting washed up logs during a year at Ajuruteua beach, state of Pará, northern Brazil. A single species, Neoteredo reynei (Bartsch, 1920), was found colonizing driftwood. Although large colonized logs were most common on the beach, shipworm density was higher in small logs, especially during the dry season. In general, however, density was higher during the wet season (January to April) and lowest in July. Overall shipworm mean length was 9.66cm. In large logs, mean length increased between the wet and dry seasons. However, there was no difference in length among log size categories. Mean shipworm length was similar throughout most of the year but tended to be greater in July. Although salinity varied between 10.9 and 40 during the year, no relationship was found between salinity and density or length. The results suggest that shipworm activity in driftwood logs is relatively constant throughout the year. Increased air humidity and rainfall may promote survival during the wet season. Large logs may take longer to colonize and thus have lower densities than small ones which are scarce probably because they are destroyed rapidly by shipworm activity. However, data on the disintegration of logs would be necessary to test this hypothesis. Larger size of shipworms in the dry season may be related to growth after an earlier recruitment period. Shipworms in large logs during the dry season may be better protected from dessication and high temperatures by the insulating properties of the larger volume of wood.
Highlights
Teredinids are common in mangroves in the region (BEASLEY et al, 2005) and as a contribution towards knowledge of the fate of exported mangrove detritus to coastal areas, the present study aims to quantify variation in the frequency of colonized mangrove driftwood logs, and the density and size of shipworms colonizing these, during a one-year period at Ajuruteua beach
Several species of Teredinidae have been recorded from the northern coast of Brazil (RIOS, 1994; MÜLLER & LANA, 2004) but N. reynei was the only shipworm found in mangrove driftwood logs in the present study
Neoteredo reynei is a common species in mangroves of both the Eastern and Western Atlantic and occurs along most of the Brazilian coast (MÜLLER & LANA, 2004)
Summary
At Ajuruteua beach, on the northeastern coast of the state of Pará, northern Brazil, large quantities of mangrove woody biomass containing shipworms are observed after high tide. Teredinids are common in mangroves in the region (BEASLEY et al, 2005) and as a contribution towards knowledge of the fate of exported mangrove detritus to coastal areas, the present study aims to quantify variation in the frequency of colonized mangrove driftwood logs, and the density and size of shipworms colonizing these, during a one-year period at Ajuruteua beach.
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