Assessing impacts of changing ocean conditions on three nearshore foundational species
Authors: Young M A , Ierodiaconou D 
Published: September 2017

Climate change is having far reaching impacts across the globe but there is a still a lot of uncertainty in how ecosystems are responding. This uncertainty is much greater in marine ecosystems where our understanding lags behind that of terrestrial ecosystems.
Despite this lag in understanding, marine environments are changing at rapid rates and there is a need to study the effects of how changes in ocean conditions are affecting marine ecosystems. Most studies in the past have looked at how temperature fluctuations are shifting the abundance and
distribution of species; however, climate change is also impacting other aspects of the ocean including circulation and the wave environment. Taking into account all of these changes in the marine environment and focusing on species that are important and foundational members of the community can
give insight into how marine ecosystems are likely to respond to climate related changes. In this study, we looked at three species that structure the nearshore environment and their responses to variations in habitat and oceanic conditions along the Southeast coast of Australia. With rises in ocean
temperatures exacerbated by the strengthening of the East Australian Current, the water off the coast of Southeast Australia is experiencing rapid warming, causing this region to be a hotspot for ocean temperature change. To assess ecosystem response to these changes, we investigated two species of
habitat forming kelps (Ecklonia radiata and Pyllospora comosa) and an ecosystem engineer (blacklip abalone, Haliotis rubra). Using long-term data (2003-2015) on E. radiata and P. comosa percent cover and H. rubra biomass collected using diver transects across 180 sites along the coast of Victoria,
Australia, we assessed the relationship between these species and environmental drivers. These environmental drivers included seafloor habitat characteristics, hydrodynamic information that was downscaled to 500 m resolution and hindcasted over the past 20 years (wave orbital velocities, wave power,
significant wave height, current speed, current direction) and annual and seasonal sea surface temperature data from 2003-2015. We also incorporated annual catch data to account for abalone population decreases due to commercial fisheries. We then related all these variables in generalized linear
mixed effects models (GLMM) for each species with year and sites as random effects. The results from the GLMMs show that these three species have strong habitat associations and complex interactions with changes in sea surface temperature and the hydrodynamic environment. For example, the subsurface
kelp species tend to have a negative response to warming temperatures but this response can be buffered by increasing or consistent wave exposure. Overall, this study helps us to understand the combined effects of habitat and changing oceanographic conditions on these three species, which will help
to facilitate management of these ecologically and economically important nearshore marine ecosystems.