103. Biofouling in high-CO2 coastal oceans: importance of multiple stressors interactions

Thiyagarajan Vengatesen (1)*, Chaoyi Li (1), Yuan Meng (1), Chong He (2), Haimin Yao (2) and Vera B. S. Chan (3)

1 The Swire Institute of Marine Sciences and School of Biological Sciences, The University of Hong Kong, Hong Kong SAR.
2 Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR.
3 Department of Biological Sciences, University of Clemson, SC, USA

Background
Consequences of global environmental (and climate) change on calcifying coastal marine invertebrates can be better understood through multi-factor, multi-life stages and multiple end-point studies. However, majority of existing literatures are focused on single stressors, life stages and end-points. Recently, we have been intensively investigating the interactive effect of decreased pH (7.8), warming (29oC) and reduced salinity (27‰) on pre- and post-settlement developmental processes of the calcareous tube-building biofouling worm, Hydroides elegans using a factorial manipulation experiment.

Methods
We have made series of simultaneous measurements using a multidisciplinary approach to understand mechanisms through which tubeworm larvae might adapt or succumb to climate change. Recently, the architecture of the calcareous shells and its mechanical properties in response to OA has also been successfully mapped using tools borrowed from mechanical engineering (nanoindentation and ABAQUS finite element modeling). Using these proteomics and shell mechanical analysis tools, the molecular processes that direct the response of tubeworms to multiple stressors and their fitness in terms of tube mechanics was understood to some extent.

Findings
Tubeworms produce a mechanically weaker tube with less resistance to simulated predator attack under OA (pH 7.8). Warming (29oC) increased tube volume, tube mineral density and tube’s resistance to simulated predatory attack. A weakening effect by OA does not make the removal of tubeworms easier except for the earliest stage, in which warming has the least rescuing effect. Reduced salinity (27 psu) did not affect tubes.

Conclusions
Our research suggests that the biofouling strength of the tubeworm is likely to be enhanced by warming in the future ocean, and more effective antifouling or removal method may be necessary.