Browsing by Author "Duarte, Cristian"

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    Cross-examining the influence of upwelling and seaweed quality on herbivores' feeding behavior and growth
    (2024) Sepulveda, Felipe; Quijon, Pedro A.; Quintanilla-Ahumada, Diego; Vargas, Juan; Aldana, Marcela; Fernandez, Melissa; Varas, Oscar; Zapata, Javier; Pulgar, Jose; Duarte, Cristian
    At the regional scale, upwelling conditions are known to influence ecosystems and communities and their primary and secondary productivity. However, the influence of upwelling on local herbivore-algae interactions is less well understood. We address this question by cross-examining herbivores and seaweeds from sites associated with upwelling and downwelling conditions along the Humboldt Current System. Specifically, we quantified the feeding and benefits attained by the black sea urchin (Tetrapygus niger) and the black sea snail (Tegula atra) while consuming a widespread kelp species (Lessonia spicata). We hypothesized that food quality drives herbivores' preference, consumption, and growth rates, regardless of the origin or "prior" conditions of the consumers. Laboratory trials measured algal consumption rates with (preference) and without a choice, and consumer's growth rates, to assess the influence of food quality (algae from upwelling vs downwelling sites) and the site of origin of the consumers. Our results showed that algal quality was a prevailing factor for both herbivores: they chose, consumed more, and grew faster on high quality (upwelling) algae. By comparison, the origin of the consumer was only significant for sea snails: those coming from an upwelling site, consumed significantly more and grew faster than those from downwelling. The bulk of our results provided strong support to our hypothesis and suggest that the high nutritional quality of algae associated with upwelling centers has a strong influence on consumers' preferences, consumption, and performance (growth). The fact that origin was found to be relevant for one of the herbivores suggests that the conditions in which species grow may dictate some of their efficiency as consumers.
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    Morphological, physiological and behavioral responses of an intertidal snail, Acanthina monodon (Pallas), to projected ocean acidification and cooling water conditions in upwelling ecosystems
    (2022) Duarte, Cristian; Jahnsen-Guzman, Nicole; Quijon, Pedro A.; Manriquez, Patricio H.; Lardies, Marco A.; Fernandez, Carolina; Reyes, Miguel; Zapata, Javier; Garcia-Huidobro, M. Roberto; Lagos, Nelson A.
    Ocean acidification (OA) is expected to rise towards the end of the 21st century altering the life history traits in marine organisms. Upwelling systems will not escape OA, but unlike other areas of the ocean, cooling effects are expected to intensify in these systems. Regardless, studies evaluating the combined effects of OA and cooling remain scarce. We addressed this gap using a mesocosm system, where we exposed juveniles of the intertidal muricid snail Acanthina monodon to current and projected pCO(2) (500 vs. 1500 ppm) and temperature (15 vs. 10 degrees C) from the southeast Pacific upwelling system. After 9 weeks of experimental exposure to those conditions, we conducted three estimations of growth (wet weight, shell length and shell peristomal length), in addition to measuring calcification, metabolic and feeding rates and the ability of these organisms to return to the normal upright position after being overturned (self-righting). Growth, feeding and calcification rates increased in projected cooling conditions (10 degrees C) but were unaffected by pCO(2) or the interaction between pCO(2) and temperature. Instead, metabolic rates were driven by pCO(2), but a significant interaction with temperature suggests that in cooler conditions, metabolic rates will increase when associated with high pCO(2) levels. Snail self-righting times were not affected across treatments. These results suggest that colder temperatures projected for this area would drive this species growth, feeding and calcification, and consequently, some of its population biology and productivity. However, the snails may need to compensate for the increase in metabolic rates under the effects of ocean acidification. Although A. monodon ability to adjust to individual or combined stressors will likely account for some of the changes described here, our results point to a complex dynamic to take place in intertidal habitats associated with upwelling systems.
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    Ocean acidification alters anti-predator responses in a competitive dominant intertidal mussel
    (2022) Jahnsen-Guzman, Nicole; Lagos, Nelson A.; Quijon, Pedro A.; Manriquez, Patricio H.; Lardies, Marco A.; Fernandez, Carolina; Reyes, Miguel; Zapata, Javier; Roberto Garcia-Huidobro, M.; Labra, Fabio A.; Duarte, Cristian
    Widespread intertidal mussels are exposed to a variety of natural and anthropogenic stressors. Even so, our understanding of the combined influence of stressors such as predation risk and ocean acidification (OA) on these species remains limited. This study examined the response of the purple mussel (Perumytilus purpuratus), a species distributed along Pacific southeastern rocky shores, to the effects of predation risk and OA. Using a laboratory 2 x 2 cross design, purple mussels were either devoid or exposed to predator cues from the muricid snail Acanthina monodon, while simultaneously exposing them to current (500 ppm) or projected OA conditions (1500 ppm). The response of purple mussels to these factors was assessed using growth, calcification, clearance, and metabolic rates, in addition to byssus production. After 60 d, the presence of predator cues reduced mussel growth in width and length, and in the latter case, OA enhanced this response making the effects of predator cues more severe. Calcification rates were driven by the interaction between the two stressors, whereas clearance rates increased only in response to OA, likely explaining some of the growth results. Mussel byssus production also increased with pCO(2) but interacted with predation risk: in the absence of predator cues, byssus production increased with OA. These results suggest that projected levels of OA may alter and in some cases prevail over the natural response of purple mussels to predation risk. Considering the role played by this mussel as a dominant competitor and ecosystem engineer in rocky shores, these results have community-wide implications.