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Navarro, J. M., Duarte, C., Manriquez, P. H., Lardies, M. A., Torres, R., Acuna, K., et al. (2016). Ocean warming and elevated carbon dioxide: multiple stressor impacts on juvenile mussels from southern Chile. ICES J. Mar. Sci., 73(3), 764–771.
Abstract: The combined effect of increased ocean warming and elevated carbon dioxide in seawater is expected to have significant physiological and ecological consequences at many organizational levels of the marine ecosystem. In the present study, juvenile mussels Mytilus chilensis were reared for 80 din a factorial combination of two temperatures (12 and 16 degrees C) and three pCO(2) levels (380, 700, and 1000 μatm). We investigated the combined effects of increasing seawater temperature and pCO(2) on the physiological performance (i.e. feeding, metabolism, and growth). Lower clearance rate (CR) occurred at the highest pCO(2) concentration (1000 μatm) compared with the control (380 μatm) and with the intermediate concentration of pCO(2) (700 μatm). Conversely, CR was significantly higher at 16 degrees C than at 12 degrees C. Significant lower values of oxygen uptake were observed in mussels exposed to 1000 μatm pCO(2) level compared with those exposed to 380 μatm pCO(2). Scope for growth (SFG) was significantly lower at the highest pCO(2) concentration compared with the control. Mussels exposed to 700 μatm pCO(2) did not show significantly different SFG from the other two pCO(2) treatments. SFG was significantly higher at 16 degrees C than at 12 degrees C. This might be explained because the experimental mussels were exposed to temperatures experienced in their natural environment, which are within the range of thermal tolerance of the species. Our results suggest that the temperature rise within the natural range experienced by M. chilensis generates a positive effect on the processes related with energy gain (i.e. feeding and absorption) to be allocated to growth. In turn, the increase in the pCO(2) level of 1000 μatm, independent of temperature, adversely affects this species, with significantly reduced energy allocated to growth (SFG) compared with the control treatment.
Keywords: high CO2; multiple stressors; mussels; ocean warming; scope for growth; thermal window
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Ramajo, L., Fernandez, C., Nunez, Y., Caballero, P., Lardies, M. A., & Poupin, M. J. (2019). Physiological responses of juvenile Chilean scallops (Argopecten purpuratus) to isolated and combined environmental drivers of coastal upwelling. ICES J. Mar. Sci., 76(6), 1836–1849.
Abstract: Coastal biota is exposed to continuous environmental variability as a consequence of natural and anthropogenic processes. Responding to heterogeneous conditions requires the presence of physiological strategies to cope with the environment. Ecosystems influenced by upwelling endure naturally cold, acidic and hypoxic conditions, nevertheless they sustain major fisheries worldwide. This suggests that species inhabiting upwelling habitats possess physiological adaptations to handle high environmental variability. Here, we assessed the impact of the main upwelling drivers (temperature, pH and oxygen) in isolation and combined on eco-physiological responses of Chilean scallop Argopecten purpuratus. A. purpuratus responded to hypoxia by increasing their metabolic performance to maintain growth and calcification. Calcification was only affected by pH and increased under acidic conditions. Further, A. purpuratus juveniles prioritized calcification at the expense of growth under upwelling conditions. Increasing temperature had a significant impact by enhancing the physiological performance of A. purpuratus juveniles independently of oxygen and pH conditions, but this was associated with earlier and higher mortalities. Our results suggest that A. purpuratus is acclimated to short-term colder, acidic and hypoxic conditions, and provide important information of how this species responds to the heterogeneous environment of upwelling, which is significantly relevant in the climatic context of upwelling intensification.
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Saavedra, L. M., Saldias, G. S., Broitman, B. R., & Vargas, C. A. (2021). Carbonate chemistry dynamics in shellfish farming areas along the Chilean coast: natural ranges and biological implications. ICES J. Mar. Sci., 78(1), 323–339.
Abstract: The increasing shellfish aquaculture requires knowledge about nearshore environmental variability to manage sustainably and create climate change adaptation strategies. We used data from mooring time series and in situ sampling to characterize oceanographic and carbonate system variability in three bivalve aquaculture areas located along a latitudinal gradient off the Humboldt Current System. Our results showed pH(T) <8 in most coastal sites and occasionally below 7.5 during austral spring-summer in the lower (-30 degrees S) and central (-37 degrees S) latitudes, related to upwelling. Farmed mussels were exposed to undersaturated (Omega(arag) < 1) and hypoxic (<2 ml l(-1)) waters during warm seasons at -37 degrees S, while in the higher latitude (43 degrees S) undersaturated waters were only detected during colder seasons, associated with freshwater runoff. We suggest that both Argopecten purpuratus farmed at -30 degrees S and Mytilus chilensis farmed at -43 degrees S may enhance their growth during summer due to higher temperatures, lower pCO(2), and oversaturated waters. In contrast, Mytilus galloprovincialis farmed at 37 degrees S grows better during spring-summer, following higher temperatures and high pCO(2). This knowledge is relevant for aquaculture, but it must be improved using high-resolution time series and in situ experimentation with farmed species to aid their adaptation to climate change and ocean acidification.
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