Changing consumer strength in a changing climate

• Main Author: Mertens, Nicole Lee
• Other Authors: Connell, Sean Duncan, Russell, Bayden D., School of Biological Sciences
• Format: Thesis
• Language: unknown
• Published: 2016
• Subjects: metabolic rate; species interactions; herbivory; compensation; threshold; Research by Publication; Ocean acidification
• Online Access: http://hdl.handle.net/2440/105074; https://doi.org/10.4225/55/5913bc791a6fb

The intensity at which organisms interact is affected by abiotic conditions. Ocean warming and acidification alter the metabolic demands of organisms and the strength at which they interact with each other. The metabolic costs of changing abiotic conditions vary between interacting pairs of species, and as such, their strength of influence on one another may change with changing climate. Ocean warming and acidification are anticipated to alter competitive dominance among primary producers such as perennial kelp and ephemeral turf algae, increasing the potential for ecosystems to undergo phase shifts, e.g. from kelp-dominated to persistent turf-dominated states. However, in order to meet greater metabolic demands imposed by elevated temperature, herbivorous invertebrates need to increase feeding rates and may counter turf productivity as a result. Whilst strong top-down control of primary productivity is supported by metabolic theory of ecology (MTE), it assumes that consumption rates of herbivores keep pace with metabolism and mirror increased growth of producers. At moderate warming, both metabolic rates and feeding of herbivorous gastropods were elevated, yet as temperature increased further consumption rates peaked earlier than turf growth rates. Imposed costs to resource allocation where consumption does not meet metabolic demands may result in reduced fitness and survivorship. These results suggest that future strength of top-down control is dependent on whether consumer-producer responses are synchronous, with mismatches between interacting pairs producing outcomes not predicted by metabolic theory. Further, moderate increases of temperature and CO₂ lead to reduced herbivore ingestion efficiency, ultimately resulting in reduced growth. Elevated metabolism generally requires increased foraging to meet energetic demands; however, foraging may also need to be mediated by predator avoidance. This thesis identified that the need for greater foraging activity imposed by future warming and ocean acidification was ...