The work accomplished in the 13-month period of this project combined a literature review, field observations and rigorous laboratory experiments. First a literature review was written, addressing recent developments, in the context of global change, on how hydrodynamic processes modulate biogenically-induced fluctuations in coastal seawater chemistry shaping chemical habitats which can change the responses of subtidal benthic organisms and communities to global change. This seminal article, almost submitted for publication, aims at showing to the scientific community the importance of (1) the local heterogeneity in physico-chemical parameters and (2) the biological shaping in coastal environments to cope with global changes.
In Tasmania, a spot presenting a high density of Phyllospora comosa, one of the most common brown seaweed East Australian species, was monitored during summer 2018, measuring temperature, light and pH fluctuations under canopy. The data acquired informed the design of the experiments developed in the next step of the project. An experiment run in a cutting-edge fully replicated setup investigated the physiology of P. comosa under current and future scenarios of ocean acidification and in the presence or absence of an heatwave. The first results analysed tend to show that P. comosa is not affected by future pH levels. In addition, this alga is also able to resist current and future levels of heatwave without drastic physiological impediment or growth reduction. A second experiment looked at the heterogeneity of micro-environments (i.e. DBL thickness and O2 and pH gradients) at the surface of coralline algae living in understory of P. comosa canopies in different flow conditions. First results show that the presence of epiphytes’ tufts on coralline algae increases the thickness of the DBL. In these micro-habitats, pH and oxygen concentration increase at higher levels than in the surrounding seawater, providing potential shelters for small organisms as abalone larvae which usually recruit on these type of substratum.
