Córdova, K. Z. L.1,2,3 ; Fernández, E.2; Flye-Sainte Marie, J.4; Graco, M. 2, 1; Aguirre, A.3
1 Ciencias del Mar, Universidad Peruana Cayetano Heredia
2 Área funcional de Oceanografía Química y Geológica, Instituto del Mar del Perú
3 Laboratorio de Ecofisiología Acuática, Instituto del Mar del Perú
4 LEMAR (UBO/CNRS/IRD), Université de Bretagne Occidentale
There is some evidence that the anthropogenic CO2 modifies the seawater, in particular the pH, increasing the ocean acidity. This change affect the carbonate system and in consequence the calcifying organisms such as scallops (Argopecten purpuratus). Along the Peruvian coast natural conditions of low pH (< 7,9) is a normal condition in the habitat of this species due to the coastal upwelling. In this context, an experiment was performed in order to test the effects of low pH on growth, calcification and dissolution in juvenile scallops (average size: 14 mm height). During one month, scallops were exposed to two different conditions: control with unmanipulated seawater presenting pH conditions similar to those found in situ (pHT mean = 7.8) and the treatment, in which seawater was injected with CO2 lowering the pH (pHT mean = 7.4). Under the control conditions, scallops exhibited a similar growth to those observed in the field (0.3 mm.d-1). Shell height and weight at the end of the experiment, growth and calcification rates were significantly lower in the low pH condition (p < 0.05). The weight of the soft tissues showed no significant difference between treatments. Dissolution rates were significantly higher in the treatment (p < 0.05). The results indicate that the low pH conditions affect the growth of the hard parts of the Peruvian scallop that might induce an increased susceptibility to predation and affect the aquaculture of this species. However, further studies are necessary during ontogeny and incorporate other stressors such as oxygen to better understand and predict responses of this species to environmental variability and global change.
Keywords: Argopecten purpuratus, pH, growth, calcification, dissolution.