Abstract
Increasing turbidity in coastal waters reduces benthic irradiance levels and consequently poses a fundamental threat to benthic primary producers and the food webs they support. It is therefore necessary to better understand how important primary producers, such as kelp, can adapt both physiologically and morphologically to these declining light conditions. This study examines how variation in turbidity influences the morphology of the kelp Ecklonia radiata , and how this relates to photosynthetic performance, by measuring multiple morphological characteristics, photosynthesis‐irradiance response, and photosynthetic pigments in adult kelp across a large‐scale turbidity gradient. Kelp morphology was strongly related to variation in benthic irradiance among sites, but this was not consistent with morphological acclimation. Kelp at the most turbid sites had short stipes (