Linking environmental stressors to trait variation in the golden kelp Ecklonia radiata

Organisms respond to environmental stressors in various ways, including moving, adapting, acclimatising or a combination of responses. Urbanisation brings an array of stressors into the environment, such as habitat loss, contaminants, and excess nutrients. Since estuaries are the ecotone between fresh and saltwater environments, resident communities already experience intense natural stressors. With the additional pressure of urbanisation, effects on organisms are likely to be compounded and exacerbated. It is therefore important to understand the eco-physiological characteristics enabling organisms to persist in urbanised estuaries. 

Habitat-forming species such as macro-algae are foundational engineers of underwater communities and ecosystems, yet some are declining due to urbanisation. This project assessed the sources of phenotypic variation in the golden kelp Ecklonia radiata across an urban estuary, Sydney Harbour. We found that kelp morphology differed significantly across the harbour. Kelp individuals were smaller, had fewer laminae, and were devoid of spines in the inner harbour where it was warmer, more contaminated and less light was available. Inner harbour populations were also characterised by lower tissue nitrogen concentrations and higher lead concentrations. 

Investigating the trait variation of E. radiata provides insights into how urbanisation could affect its morphology and physiology, and potential consequences for associated ecological functions.