Nicole Knight

Student Speaker | Étudiant.e
The effects of seasonal upwelling on tropical organisms are poorly understood. We expect that declines in temperature and changes in resource availability associated with upwelling will elicit physiological responses in feeding and digestion by reef fishes, and that these responses may differ across trophic groups. In particular, the temperature constraint hypothesis (TCH) predicts that low temperatures will disadvantage herbivorous fishes by impairing their ability to digest plant material. We tested this hypothesis by comparing the feeding behaviour and digestive physiology of herbivorous, omnivorous, and carnivorous damselfishes on the Pacific coast of Panama during the warm non-upwelling season and cold upwelling season. If the TCH is correct, we predicted that during the upwelling season a) omnivores will consume more animal prey and less plant material, b) herbivores will exhibit reduced body condition, and/or c) herbivores will exhibit disturbed gut microbiomes. Our results show that all species respond similarly to upwelling: omnivores do not increase uptake of animal prey, and all species exhibit improved body condition, likely due to increased resource availability. Further, fishes' gut microbiota showed no signs of nutritional stress during upwelling. Altogether, our results demonstrate that seasonal upwelling benefits damselfishes regardless of trophic group and is not associated with decreased digestive performance among herbivores.