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Artificial structure density predicts fouling community diversity on settlement panels


Invasions of fouling organisms that colonize artificial structures are modifying coastal environments. Our goal was to assess harbor conditions including dissolved copper pollution, position in relation to open coast, temperature, and artificial structure density (substrate for fouling) as determinants of macroinvertebrate recruitment. Settlement panels were deployed over a gradient of human coastal modification (28 sites in California and 2 in southern Australia). Non-indigenous macroinvertebrates dominated panel cover (overall by six-fold compared to indigenous taxa). Marinas and sites of heavy shipping showed high macroinvertebrate diversity, contrasting with open-coast sites of lower human impact [Santa Catalina Island (SCI) and one mainland coastal site] where there was low macroinvertebrate fouling. At two SCI sites with low vessel traffic, invertebrates that were rare on exposed panels were more common in a protected space between plastic strips indicating larvae amount does not completely explain low invertebrate diversity, suggesting a contributing role of predators or larval recruitment pattern. While dissolved copper levels correlated strongly with artificial structure measured at the water surface, the pollution gradient was not supported as a driver of macroinvertebrate diversity in semi-partial analysis. Density of artificial structure was supported as a better predictor of macroinvertebrate diversity, including separately analyzed non-indigenous and indigenous groups, than dissolved copper, distance from open coast or temperature variation in semi-partial correlation analysis. An artificial structure density measure may therefore increase power in predicting abundance of fouling organisms and could be useful in moderating the influence of non-indigenous species.

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Source: b Schoonmaker Marina (2015)—SM; c Port of Los Angeles outer—LA2; d Harbor Island East inner—HE1; e Avalon Bay inner—AB2

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Many marina and dock operators provided access to survey sites making this project possible. For general assistance we thank Sean Craig (Humboldt State University), Leslee Parr (San José State University), Jeff Honda (SJSU), Krista Kamer [San Francisco State University/Cal. State University Council on Ocean Affairs, Science & Technology (COAST)], Andrew Phan and Niusha Taeidi-Mackie. Nathan Bott (RMIT, Bundoora), Kristian Peters (Department of Environment, Water and Natural Resources, South Australia) and Richard Piola (Defense Science and Technology Group, Australia) conducted the deployment and photography panels in Australia. Claire Till (Humboldt State University) conducted dissolved copper measurements at UC Santa Cruz. Lee Veliz (SJSU, College of Science) supervised panel construction. Shannon Bros-Seemann performed some of the analyses, and her experience and positive support were invaluable. We thank many people for assistance in coordination, fieldwork, or photograph analysis (including Timothy Andriese, Reggie Blackwell, Daniel Corral, Henry Dinh, Ann Ho, Katie Houle, Sunny Leung, Stephanie Luu, Kyle Martin, Matthew L. Nelson, Vannu Nguyen, Danielle Perryman, Seena Sajdieh, Parham Tabar, Shearon Threets, Darren Wostenberg). Bruno Pernet (CSU, Long Beach) read the paper and provided useful feedback. Two anonymous reviewers provided feedback that greatly improved the paper. This work was supported by the California State Lands Commission (award C2014-043) and National Science Foundation (1061695).

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Correspondence to Kent Susick or Joshua A. Mackie.

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Susick, K., Scianni, C. & Mackie, J.A. Artificial structure density predicts fouling community diversity on settlement panels. Biol Invasions 22, 271–292 (2020).

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