The pullet carpet shell, Venerupis corrugata, is an important fishery resource, traditionally harvested at the Southwestern and Mediterranean Europe. This species has a high market value (actual global average price over $21USD) and its aquaculture production is now essential to meet the market high demand, warranting natural stocks maintenance under frequent overfishing and high mortalities caused by pathogens and extreme climatic events, that will be more frequent under the climate conditions predicted for a near future. The potential impacts of two major global phenomena ongoing in the world oceans –acidification (OA) and warming (W)– on the performance of V. corrugata early life stages was studied by assessing the development stage and the behaviour exhibited by specimens cultured under 9 experimental scenarios for 14 and 60 days (larvae and juveniles, respectively).
Broodstock collected at the Ria de Aveiro (NW Portugal) was induced to spawn by thermal stimulation. Eggs were incubated to hatch in 1-μm filtered, UV-sterilized artificial saltwater under unmanipulated pH (~8.2) and 18±1°C (control conditions). The D-larvae collected in a 60μm-sieve 48h post-fertilization (48h pf) were exposed to the 9 OA-W scenarios presented in Fig.1, resultant from a factorial design of three pH levels (targeting 8.2, 7.8 and 7.6) at three different temperatures (18, 20 and 22°C). Larval development stage and swimming behaviour (characterized by a 6-stages scale developed for the purpose) were characterized after 14 days of exposure (at T14) and the early juveniles’ burial activity and byssus production were assessed at T60.
As expected, larval development was proved to be accelerated by warming and relatively delayed under acidity. However, larval behaviour was proved to be significantly affected only by temperature, with “searching” and “crawling” behaviours being registered at treatments at which more developed specimens were recorded. In turn, when subject to the presence of sediment, the early juveniles reared under higher acidity (pHtarget 7.6) for 60 days revealed lower ability to bury, as well as reduced capacity to produce byssus, behavioural changes that might compromise both mobility and fixation to the substrate, essential to this clam survival.
Hence, this study suggests that despite warming may reduce the negative effects of OA on V. corrugata larval development, the exposure to lower pH