Recruitment and growth of the xylophagous bivalve Bankia martensi ( ) with different levels of wood biofouling species cover

Abstract

Teredinid bivalves (shipworms) are the main wood degraders in marine environments. However, little is known about the biological interactions between these marine wood borers and wood-associated biofouling species. Filter-feeding species and seaweeds are frequent biofoulers on the submerged wood. Using the marine xylophagous bivalve Bankia martensi (Stempell, 1899) as a model, we hypothesized that increasing the abundance of biofouling species on wood will decrease the recruitment and subsequent growth of the shipworm B. martensi. During the springs of 2020 and 2021, experiments manipulating biofouling cover were carried out using pine panels in Bahía Metri, southern Chile. Three experimental levels of biofouling cover were established (low: 0%–10%, intermediate: 40%–50%, and high: 90%–100%). After five months, the number of B. martensi perforations (as proxy as larval settlement density) and specimen sizes (length, width and volume) in the panels were measured. An inverse relationship between the perforation densities of B. martensi and biofouling cover on the wooden panels was observed. The most frequent biofouling species were mussels and seaweeds which tended to settle on the upper and lateral surfaces, while acorn barnacles and bryozoans were more frequent on the lower surface. Bankia martensi perforations were reduced with increasing biofouling cover. The number of perforations varied according to the panel surface, higher density on the upper and lateral surfaces and lower on the underside. Bankia martensi specimens were larger, both in length and in volume, in panels with low biofouling compared to intermediate and high biofouling cover, while width did not vary with treatment. Our results suggest that the biofouling cover decreases B. martensi recruitment and growth rates, which in turn reduces the wood degradation rate caused by this teredinid. Future manipulative experiments with selected biofouling species (filter-feeders, such as mussels and barnacles), as well as incorporating measurements of reproductive traits of shipworms could help in understanding the biological interactions between these marine communities of wood-boring and biofouling species.