Artificial habitats host elevated densities of large reef-associated predators

Abstract

Large predators play important ecological roles, yet many are disproportionately imperiled. In marine systems, artificial reefs are often deployed to restore degraded reefs or supplement existing reefs, but it remains unknown whether these interventions benefit large predators. Comparative field surveys of thirty artificial and natural reefs across~200 km of the North Carolina, USA coast revealed large reef-associated predators were more dense on artificial than natural reefs. This pattern was associated with higher densities of transient predators (e.g. jacks, mackerel, barracuda, sharks) on artificial reefs, but not of resident predators (e.g., grouper, snapper). Further analyses revealed that this pattern of higher transient predator densities on artificial reefs related to reef morphology, as artificial reefs composed of ships hosted higher transient predator densities than concrete reefs. The strength of the positive association between artificial reefs and transient predators increased with a fundamental habitat trait-vertical extent. Taller artificial reefs had higher densities of transient predators, even when accounting for habitat area. A global literature review of high trophic level fishes on artificial and natural habitats suggests that the overall pattern of more predators on artificial habitats is generalizable. Together, these findings provide evidence that artificial habitats, especially those like sunken ships that provide high vertical structure, may support large predators.

eDNA metabarcoding of small plankton samples to detect fish larvae and their preys from Atlantic and Pacific waters

“…In contrast with coast samples, most non-zooplankton OTUs detected from West African open waters were large vertebrates that are not part of plankton in any life stage (Supplementary Table 3 ). The samples were taken from RV Polarstern and it is well known that ships attract many large predators that feed on food leftovers and benefit from other species that surround ships 71 , 72 . Metabarcoding detects only DNA molecules, and expectedly large individuals shed more DNA than small species do 73 .…”

Fitting ecological principles of artificial reefs into the ocean planning puzzle

“…Artificial reefs can host cryptic demersal fish, such as blennies and gobies, as well as bottom‐associated reef fish from a variety of trophic groups, including invertivores and herbivores (Cresson, Ruitton, Ourgaud, & Harmelin‐Vivien, 2014; Paxton, Newton, et al, 2020). These structures can also support high concentrations of pelagic fishes, including planktivores (Arena et al, 2007; Champion et al, 2015) and piscivores (Ajemian et al, 2015; Paxton, Newton, et al, 2020). And, similar to energy infrastructure, artificial reefs form habitat for large predators (Figure 1d), like sand tiger sharks ( Carcharias taurus ), which have been observed to exhibit site fidelity to artificial reefs (Paxton, Blair, et al, 2019), as well as top predators, including white sharks ( Carcharodon carcharias ) (A. Paxton, personal observation, 2015).…”

“…For example, an observational field study in the southeast United States revealed that while metal ships hosted higher fish abundance than concrete modules, the abundance was similar on concrete modules and natural rocky reefs (Lemoine et al, 2019). Other studies have demonstrated differences in fish community metrics with artificial reef materials, too, yet there are usually location‐specific nuances that require regional assessments of how particular materials relate to ecological communities (see Paxton, Shertzer, et al, 2020). For example, benthic invertebrate colonization patterns have been linked not only to reef material but also to factors including reef size, proximity to nearby reefs, hydrodynamics, and the orientation of the artificial reef (Higgins et al, 2019).…”

“…Pete was ahead of his times, practicing marine spatial planning before it was an established practice (Foley et al, 2010). Throughout his career, Pete conducted research related to siting and understanding ecological functions of artificial structures, ranging from wind turbines (Taylor et al, 2016;Voss et al, 2013) and hardened shorelines (Gittman et al, 2014(Gittman et al, , 2015 to artificial reefs (Lemoine et al, 2019;Paxton et al, 2017Paxton et al, , 2018Paxton, Newton, et al, 2020;Paxton, Peterson, et al, 2019;Peterson et al, 2003;Powers et al, 2003;Rosemond et al, 2018); so, this manuscript prescribes a path forward for incorporating ecological principles into planning for artificial reefs that is in line with Pete's visions. We thank Pete for his invaluable mentorship.…”

New Insight Into the Mechanism of Ecological Effects of Artificial Habitats: Elucidating the Relationship Between Protists Associated With Artificial Reefs and Adjacent Seawater

“…To clarify the role of artificial habitats in global fisheries management, a large number of studies have been carried out, including studies on the influence of artificial habitats on marine environmental factors (Falcao et al, 2007;Yu et al, 2015), the trapping effect on fish and other marine organisms (Folpp et al, 2020;Paxton et al, 2020;Hall et al, 2021), the provision of spawning substrate for fish that produce sticky eggs (Sandström and Karås, 2002;Guo D. et al, 2020), the provision of refuges for juvenile fishes (Bolding et al, 2010;Höjesjö et al, 2015), the phenotypic responses of specific organisms adapted to artificial habitats (Dias et al, 2021), the impact of the introduction of alien species on local species (Rumbold et al, 2020;Janiak and Branson, 2021), and the protection effect of endangered species (Claassens and Harasti, 2020).…”