Multi-scale distribution and dynamics of bivalve larvae in a deep atoll lagoon (Ahe, French Polynesia)

Abstract

Bivalve larvae and hydrographic parameters were sampled over a range of spatio-temporal scales in a deep atoll lagoon. Bivalve larvae abundances were very high throughout the year: 18,550 m(-3) in average. Larvae were (i) concentrated at mid-depth with nocturnal ascent and diurnal descent, (ii) heterogeneously dispersed at the lagoon scale, (iii) subject to day-to-day variation in abundance and (iv) transferred between different parts of the lagoon providing evidence of intra-lagoonal connectivity. The primacy of physical factors was seen on large spatial scale with the diluting effect of water renewal and transfers by hydrodynamics. On smaller spatial scale, the primacy of biological processes was recognised, with larval swimming activity leading to dial vertical migration correlated with food concentration. Variations in larval abundance were driven by bivalve reproductive activity correlated with meteorological conditions (i.e. windy periods). Finally, relationship between bivalve larvae patterns and pearl oyster (Pinctada margaritifera) settlement structuring is discussed.

Metazooplankton communities in the Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia): Spatiotemporal variations and trophic relationships

“…15% and 4%, respectively in New Caledonian lagoon; Carassou et al, 2010). In Ahe lagoon, linked to pearl farming, P. margaritifera could constitute a large part of this important bivalve larvae stock, but Thomas et al (2012a) estimated that the contribution of P. margaritifera to this stock would be low (0.5-5%) compared to wild species and in particular to P. maculata (65-91%). This suggests that high bivalve larvae concentration in the lagoon is not drastically modified by pearl oyster farming, despite 10% of the lagoon area dedicated to this activity.…”

“…Even with likely more than a few percent of farmed oysters, the relative abundance of bivalve larvae in the Ahe plankton is probably due to the importance of wild populations. The requirement to know the exact status of the wild population of bivalve has been pointed out by several of the study achieved in Ahe (Thomas et al, 2012a). This will be a priority in subsequent studies.…”

Bivalve larvae transport and connectivity within the Ahe atoll lagoon (Tuamotu Archipelago), with application to pearl oyster aquaculture management

“…In situ observations showed that bivalve larvae follow a dial migration toward the surface during the night and toward the bottom during the day (Thomas et al, 2012). The sub-model of vertical migration coupled to the transport model empirically simulated the vertical migration of the larvae depending on the swimming behaviour observed in situ.…”

“…Better knowledge of factors controlling recruitment variability will also enable to better understand the wild populations structure and to rationalise a collecting strategy for aquaculture. In particular, gametogenesis, spawning and larval growth potential also determine spat collection variability (Fournier et al, 2012;Thomas et al, 2012). Coupling biology and physic-based approaches is now needed to perpetuate the pearl oyster aquaculture.…”

“…In Ahe atoll, French Polynesia, recent studies put in evidence the lagoon-scale spatio-temporal heterogeneity of the bivalve larvae concentrations and the consequences for collection of the targeted black-lip pearl oyster for the local aquaculture industry (Thomas et al, 2012). In French Polynesian atoll lagoons, the black-lip pearl oyster (Pinctada margaritifera cumingii, Linné 1758) farming plays a major socio-economic role since the 1990s (Andréfouët and Charpy, 2012).…”