Real-time high resolution tracking of coral and oyster larvae

Abstract

Coral and oyster reefs have declined greatly due to anthropogenic stressors. Low recruitment rates from larvae hamper recovery of these important ecosystems. Although much is known about factors affecting larval settlement, a detailed understanding of their swimming and substrate selection behaviour is lacking. Here, we present an approach to study coral and oyster larval behaviour in unprecedented detail, using a high resolution camera, choice chambers and behavourial analysis software. From second-by-second spatial data, we extracted variables such as swimming pattern, swimming speed and distance travelled using larvae between 0.2 and 3 mm in length. We applied this to larvae of the Caribbean brooding coral Favia fragum and show they locate their major settlement cue, coralline algae, within 90 min when placed in a choice chamber. Oyster (Ostrea edulis) larvae exhibited reduced swimming speed with age, suggesting pre-settlement behaviour. With the presented real-time high resolution tracking approach we can address new questions related to the behaviour of coral, oyster and other marine larvae, with applications in ecology, aquaculture and coastal engineering. Most notable is future development of “flypaper” substrates with cues to promote larval settlement on reefs, to aid restoration efforts.