Colonization history meets further niche processes: how the identity of founders modulates the way predation structure fouling communities

Exploring foraging preference of local fish species towards non-indigenous fouling communities near marinas: Insights from Remote Video Foraging System (RVFS) trials

Non-indigenous species (NIS) spread from marinas to natural environments is influenced by niche availability, habitat suitability, and local biotic resistance. This study explores the effect of indigenous fish feeding behaviour on NIS proliferation using fouling communities, pre-grown on settlement plates, as two distinct, representative models: one from NIS-rich marinas and the other from areas outside marinas with fewer NIS. These plates were mounted on a Remote Video Foraging System (RVFS) near three marinas on Madeira Island. After 24-h, NIS abundance was reduced by 3.5 %. Canthigaster capistrata's preference for marinas plates suggests potential biotic resistance. However, Sparisoma cretense showed equal biting frequencies for both plate types. The cryptogenic ascidian Trididemnum cereum was the preferred target for the fish. Our study introduces a global framework using RVFS for in-situ experiments, replicable across divers contexts (e.g., feeding behaviour, biotic resistance), which can be complemented by metabarcoding and isotopic analysis to confirm consumption patterns.

Measuring the recruitment and growth of biofouling communities using clear recruitment panels

Ecological monitoring has been recognized as a key tool for guiding biofouling management practices. A two-year study was designed to collect comprehensive data on the biofouling community progression at Port Canaveral, Florida, using clear recruitment panels and a scanner to directly observe organisms attached to the surface. This method allowed for minimal disruption to the natural community development and aided the collection of a suite of metrics to explore environmental relationships. Seasonal changes in community composition and biofouling pressure, especially at earlier stages, were related to abiotic conditions. Interannual variation within seasonal communities was also observed. The type of dominant organism present impacted the rate at which surfaces were covered (e.g. fastest cover with tunicates) and the overall biomass accumulation (e.g. highest rate with tubeworms). Results highlight that understanding the influence of the time of year and the dominant organism identity is ecologically vital for improving biofouling management.

Colonisation after disturbance on artificial structures: The influence of timing and grazing

Artificial structures are poor surrogates of natural rocky shores, meaning they generally support depauperate assemblages. These differences may result from a combination of recruitment processes, biotic interactions, and structuring by environmental factors. In this study, plots were cleared on two seawalls and two natural shores at two separate timepoints - in August 2020 (summer) and February 2021 (winter) - and monitored over one year to determine the influence of timing of disturbance on recruitment and succession. Additional plots were cleared at one of the seawalls at a single timepoint in August 2020, and exclusion cages were installed to determine the influence of grazing pressure on colonisation; these were monitored for 18 months. Disturbance during winter resulted in higher concentrations of all biofilm components up to 3 months, but did not impact benthic community composition beyond this point. Grazer exclusion on artificial structures increased biofilm concentrations and influenced community composition in comparison to plots on artificial structures without exclusion, while communities on natural surfaces differed in terms of species composition to those on artificial plots at 12 months. We conclude that the timing of routine maintenance works on artificial structures may impact initial biofilm abundances. Furthermore, while grazing pressure does influence community structure on artificial structures, this alone is not sufficient to explain biological differences between artificial structures and natural shores.

Biotic interactions shape trait assembly of marine communities across time and latitude

Assembly processes are highly dynamic with biotic filters operating more intensely at local scales, yet the strength of biotic interactions can vary across time and latitude. Predation, for example, can be stronger at lower latitudes, while competition can intensify at later stages of assembly due to resource limitation. Since biotic filters act upon functional traits of organisms, we explored trait-mediated community assembly in diverse marine assemblages from four regions along the Pacific coast of North and Central America. Using predator exclusion experiments and two assembly stages, we tested the hypotheses that non-random trait patterns would emerge during late assembly at all regions due to competition and at lower latitude regions regardless of assembly stage due to predation. As expected, trait divergence occurred in late assembly but only at higher latitude regions, while in tropical Panama, relaxed predation caused trait divergence during late assembly. Moreover, colonizing trait strategies were common during early assembly while competitive strategies were favoured during late assembly at higher latitude regions. Predation-resistant traits were only favoured in Panama during both assembly stages. Our large-scale manipulative study demonstrates that different biotic interactions across time and latitude can have important consequences for trait assembly.

Enduring regardless the conditions: Plasticity in modular growth as a strategy to cope with hydrodynamic variation by the invasive sun-coral (Tubastraea spp.)

The susceptibility of a community to invasions is not the only factor influencing the success of the introduction of non-indigenous species (NIS). Because the conditions of the invaded environment tend to be unpredictable, plastic responses should increase the success of NIS in a new environment. Sun-corals are invaders in the Atlantic Ocean that present a range of strategies and plastic responses to deal with stress and distinct environmental conditions. We experimentally tested the plastic responses of sun-corals when exposed to different predation pressures and hydrodynamics in a recreational marina where sun-corals abundance varies spatially along with the environmental conditions. We separated young sun-coral colonies in two experiments: one controlling the presence of predators and the other manipulating water motion. While predation had no effect, revealing that even small young colonies are somehow protected against predators, corals increased colony area under reduced water motion but grew more polyps under greater water motion. These results highlight that plasticity in modular growth may be important for sun-corals to successfully invade distinct regions despite the hydrodynamic conditions. Increasing the colony area implicate in monopolization of space in calmer waters whilst growing more polyps allows it to have more mouths for feeding in turbulent food-poor waters. This response is particularly interesting as it is similar to the response of another NIS in the same site-the bryozoan Schizoporella errata. Phenotypic plasticity of reproductive strategies, including asexual propagation as observed here, appears to be relevant for modular NIS by facilitating the success on the invasion process in variable habitats.