# Different processes and constraints drive the assembly of deep-sea hydrothermal vent and sunken wood communities

Joan M Alfaro-lucas, Florence Pradillon, Daniela Zeppilli, Maurício

Shimabukuro, Gauthier Schaal, Loïc N Michel, Pedro Martinez-arbizu, Hayato

Tanaka, Martin Foviaux, Jozée Sarrazin

► To cite this version:

Joan M Alfaro-lucas, Florence Pradillon, Daniela Zeppilli, Maurício Shimabukuro, Gauthier Schaal, et al.. Different processes and constraints drive the assembly of deep-sea hydrothermal vent and sunken wood communities. Ecosphere, 2025, 16, 10.1002/ecs2.70351. hal-05244425

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ARTICLE

Coastal and Marine Ecology

# Different processes and constraints drive the assembly of deep-sea hydrothermal vent and sunken wood communities

Joan M. Alfaro-Lucas<fnref n="1" /> ID

Maurício Shimabukuro<fnref n="2" /> ID

Pedro Martinez-Arbizu<fnref n="5" /> ID

Jozée Sarrazin<fnref n="1" /> ID

Florence Pradillon<fnref n="1" /> ID

Gauthier Schaal<fnref n="3" /> ID

Hayato Tanaka<fnref n="6" /> ID

Daniela Zeppilli<fnref n="1" /> ID

Loïc N. Michel<fnref n="4" /> ID

Martin Foviaux<fnref n="1" /> ID

**Correspondence**

Joan M. Alfaro-Lucas
Email: jmalfarolucas@gmail.com

**Present address**

Joan M. Alfaro-Lucas, School of Biological and Marine Sciences, University of Plymouth, Plymouth, UK.

**Funding information**

Institut Français de Recherche pour l'Exploitation de la Mer; Total Foundation; Agence Nationale de la Recherche, Grant/Award Numbers: ANR-10-LABX-19, ANR-14-CE02-0008-02

**Handling Editor:** Robert J. Miller

**Abstract**

Niche processes mainly dictate the successful establishment and coexistence of species along gradients of community drivers such as energy availability and environmental stress. Deep-sea chemosynthetic habitats such as hydrothermal vents and wood falls show concomitant gradients of energy availability and stress because productivity is fueled by potentially toxic, chemically reduced compounds. However, the specific processes and constraints driving the assembly of these eco-evolutionarily related communities remain poorly understood. Here, we infer community assembly processes from species, functional, and isotopic diversity patterns of vent and wood-fall assemblages using a colonization experiment along a hydrothermal gradient, from vent periphery to diffuse-flow habitats. We hypothesized that despite the high environmental stress, the high productivity of vent diffuse-flow and wood-fall habitats increases niche space due to niche partitioning and/or competitive exclusion processes, allowing more species to coexist in high densities. As predicted, at moderate levels of stress at vent diffuse-flow habitats, productivity increases niche space and supports denser and more species-rich assemblages with many ecological strategies, suggesting niche partitioning and/or competitive exclusion of functionally similar species. However, as stress increases at habitats under higher venting influence, species richness, abundance, and functional diversity decrease, suggesting environmental filtering and/or competitive dominance of better adapted species. Similarly, the vent periphery supports fewer species, individuals, trophic levels, and reduced niche space, suggesting that the scarcer food resources act as an environmental filter. Unexpectedly, food resources at wood substrata at the vent periphery, harboring typical wood-fall communities, support very speciose and dense assemblages of reduced functional diversity. This suggests that compared to vent

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

© 2025 The Author(s). *Ecosphere* published by Wiley Periodicals LLC on behalf of The Ecological Society of America.

<footnote n="1">¹Univ Brest, Ifremer, BEEP, Plouzané, France</footnote>

<footnote n="2">²Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil</footnote>

<footnote n="3">³Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, Plouzané, France</footnote>

<footnote n="4">⁴Animal Systematics and Diversity, Freshwater and Oceanic Sciences Unit of research (FOCUS), University of Liège, Liège, Belgium</footnote>

<footnote n="5">⁵Senckenberg am Meer, German Center for Marine Biodiversity Research, Wilhelmshaven, Germany</footnote>

<footnote n="6">⁶Tokyo Sea Life Park, Tokyo, Japan</footnote>
diffuse-flow habitats, the reduced habitat availability, or longevity, of wood falls reduces niche space and promotes environmental filtering and/or competitive dominance processes. Thus, different processes and constraints appear to drive the assembly of communities along hydrothermal vent gradients and between the eco-evolutionarily related vent and wood-fall communities.

### KEYWORDS

chemosynthesis-based communities, community ecology, competitive exclusion, environmental filtering, functional traits, niche partitioning

## INTRODUCTION

Along environmental gradients of stress and productivity, abiotic and biotic (niche) processes mainly dictate the successful establishment and coexistence of organisms based on species performances as determined by their functional traits (HilleRisLambers et al., 2012; Leibold & Chase, 2018; Mittelbach & Schemske, 2015; Vellend, 2016; Weiher et al., 2011; Weiher & Keddy, 1995). These traits are morphological, physiological, and/or behavioral characteristics determining where and how species persist and grow in relation to other species and the environment (Díaz & Cabido, 2001; Violle et al., 2007). Thus, trait patterns have the potential to inform on the processes driving the assembly of communities (McGill et al., 2006; Mouillot et al., 2013). For instance, strong environmental stress or the dominance of a competitively superior clade could limit colonization to well-adapted species with similar traits, leading to trait convergence of co-occurring species reducing the functional diversity (e.g., Cadotte & Tucker, 2017; Kraft et al., 2015; Violle et al., 2010). Conversely, interspecific competition or a high diversity of resources could promote competitive exclusion between functionally similar species or niche partitioning, leading to trait divergence increasing the functional diversity (e.g., Cisneros et al., 2014; Spasojevic & Suding, 2012).

Habitats in the deep sea (>200 m depth) generally rely on organic matter of photosynthetic origin exported from hundreds or thousands of meters above (Snelgrove & Smith, 2002). Although some habitats receive abundant photosynthetic organic matter (e.g., seamounts, canyons, upwelling areas), large parts of the deep ocean floor, such as abyssal plains, are food scarce, harboring benthic communities of invertebrates with low densities and biomass (Snelgrove & Smith, 2002). Given these low animal densities, biological interactions between species are generally considered rather weak in the deep sea (reviewed in McClain & Schlacher, 2015). Consequently, environmental conditions are thought to be the main filters driving the assembly of deep-sea communities, as

shown for peracarid crustaceans inhabiting sedimentary habitats on continental slopes in the Northwest Atlantic Ocean (Ashford et al., 2018), octocorals from hard-substratum habitats in the Gulf of Mexico (Quattrini et al., 2017), and nematodes of sedimentary habitats in the Clarion-Clipperton Fracture Zone (Macheriotou et al., 2020). However, in situ chemosynthetic productivity at hydrothermal vents, cold seeps, and whale/wood-fall habitats sustains highly specialized fauna, forming communities with densities and biomass orders of magnitude higher than those of surrounding sedimentary and hard-substratum deep-sea environments (Smith et al., 2015; Van Dover et al., 2002). Productivity in these habitats, however, comes with high environmental stress because it is fueled by potentially toxic, chemically reduced compounds (e.g., H₂S) (e.g., Bienhold et al., 2013; Jannasch & Mottl, 1985; Le Bris et al., 2019). Given the concomitant productivity and stress, an unresolved question remains: What are the processes and constraints driving the community assembly and allowing species to coexist in such high densities in deep-sea chemosynthesis-based habitats?

Here, we explore this question in vent and wood-fall communities. These island-like, patchily distributed habitats create regional networks of faunal communities connected by larval dispersal (Mullineaux et al., 2018; Romano et al., 2020; Smith et al., 2015). Vents and wood falls are environmentally different and are colonized by distinct suites of specialist species. However, they also share faunal lineages and some species, highlighting different, yet related, eco-evolutionary histories (Kiel, 2016; Pereira et al., 2020; Shimabukuro et al., 2019; Smith et al., 2015). Vents are characterized by highly dynamic, steep environmental gradients created by the mixing of cold seawater with hot (up to 400°C), acidic hydrothermal fluids that are rich in chemically reduced compounds and heavy metals (e.g., Johnson et al., 1994; Luther et al., 2001). Thus, different processes and constraints could drive the assembly of communities along the concomitant stress and productivity gradients at vents (Govenar et al., 2015; Levesque et al., 2003; Luther
et al., 2001; Micheli et al., 2002). Indeed, the functional diversity could decrease from the dense faunal assemblages in diffuse-flow areas influenced by vent fluids (high stress and productivity habitats) to the low-density assemblages at vent peripheries (low stress and productivity habitats), suggesting community assembly differences along vent environmental gradients (Alfaro-Lucas et al., 2020). Consequently, we hypothesize that in diffuse-flow areas, the increase in niche space (high functional diversity) is mediated by competitive exclusion and/or niche partitioning processes due to higher productivity, allowing species to coexist in high densities despite the associated stress. Moreover, we hypothesize that the reduced niche space (low functional diversity) at the vent periphery is driven by environmental filtering due to food scarcity.

Wood falls are small, short-lived, and organic-rich habitats, where wood is simultaneously the substratum and source of energy for colonizing species (Turner, 1978). Specialist wood-boring bivalves directly exploit wood, which reduces wood longevity as a habitat but allows other specialists and non-specialists to access wood-derived energy (Bernardino et al., 2010; Turner, 1973; Voight, 2015). The microbial anaerobic degradation of both wood and wood-boring-bivalve fecal pellets produces toxic reduced-compound fluxes (e.g., H₂S) supporting chemosynthesis (Bienhold et al., 2013; Kalenichenko et al., 2018). These chemosynthetic niches are exploited by wood specialists, and some taxa also found at vents, which could use wood falls as “stepping stones” to colonize distant vent habitats (e.g., Distel et al., 2000; Pereira et al., 2020; Shimabukuro et al., 2019; Smith et al., 2015). Thus, the diversity of resources in wood falls (i.e., wood organic matter and primary chemosynthetic production) could also promote niche expansion due to competitive exclusion and/or niche partitioning processes, as hypothesized for vent diffuse-flow habitats. This resource diversity and these processes would support the establishment of dense and diverse faunal assemblages of specialists, microbial grazers, predators, generalist sulfide-tolerant fauna, and chemosymbiotic taxa observed at wood falls (Bienhold et al., 2013; McClain et al., 2016).

Here, we focus on the functional diversity patterns of invertebrate assemblages colonizing experimental substrata to assess the processes governing community assembly at vents, from periphery to diffuse-flow habitats and wood falls. We experimentally deployed slate and wood blocks for two years as proxies of vent-like and wood-fall-like substrata, respectively, at four sites along a decreasing hydrothermal vent gradient of environmental stress and productivity, that is, from vent diffuse-flow to peripheral areas (Figure 1A). The restricted spatial extent (~470 m), the same deployment

time, and the long duration of the experiment ensured the colonization by a common regional species pool, minimizing the potential role of dispersal limitation on the assembly of communities. Furthermore, size-standardized substrata allowed us to compare individual counts directly across substrata and to control for the energy availability of wood origin in organic substrata, as well as for area and shape in all substrata, which are major drivers of community assembly (Chase, 2010; Wright, 1983). Based on previous studies, we expected both slate and wood substrata under fluid influence to be colonized by diffuse-flow vent communities and slate and wood substrata at periphery sites to be colonized by vent periphery fauna and typical wood-fall fauna, respectively (e.g., Alfaro-Lucas et al., 2020; Baldrighi et al., 2018; Cuvelier et al., 2014; Plum et al., 2017; Zeppilli et al., 2015).

Moreover, we hypothesized that on slate and wood substrata at diffuse-flow vent habitats, as well as on wood substrata at periphery sites, higher productivity promotes niche space expansion (i.e., increased functional diversity) through niche partitioning and/or the competitive exclusion of functionally similar species, despite the associated environmental stress (Figure 1B,C). Thus, on slate substrata, we predicted an increase in functional diversity from peripheral areas without fluid influence to diffuse-flow areas because of the higher availability of chemically reduced compounds fueling chemosynthesis in diffuse-flow habitats (Figure 1B,C). However, on wood substrata, we did not expect functional diversity to vary along the gradient, as energy sources, either chemically reduced compounds or wood organic matter, are abundant across all sites (Figure 1B,C). Consequently, we also expected similarly high functional diversity on slates in diffuse-flow areas and on wood in peripheral areas, owning to the high-energy availability provided by chemically reduced compounds and wood organic matter, respectively (Figure 1B,C). To test our hypotheses, we performed a detailed taxonomic analysis and assessed functional trait patterns and compared these with null expectations. Additionally, we also measured the stable isotope composition of species (δ¹³C, δ¹⁵N, and δ³⁴S) to infer the diversity of resources exploited by species.

# MATERIALS AND METHODS

## Colonization experiment, substratum sampling, and faunal processing

We deployed a triplicate of wood substrata (wood blocks of 10 × 10 × 10 cm) for two years at four “sampling sites” distinctly influenced by vent fluids within and away from
<figure><img src="image_2.png" /><figcaption>**FIGURE 1** Experimental design: null models and predictions. (A) Experimental set up with slate (gray) and wood (brown) substrata along the concomitant gradient of stress and productivity, that is, from peripheral, low environmental stress-productivity sites without direct vent fluid influence (lower temperature) to diffuse-flow, high stress-productivity sites with direct vent fluid influence (higher temperature). (B) Null model design to compare the functional diversity. Null model 1 randomized species across the four sites for slate and wood substrata separately (shaded purple areas) to test the effect of the stress-productivity gradient on functional diversity while keeping the potential effects of the substratum nature fixed. Null model 2 randomized species occurring on slates under the direct influence of vent fluids and woods at sites without direct vent fluid influence (shaded purple area) to fix the factors driving, respectively, diffuse-flow hydrothermal vent (HV) communities and wood-fall (WF) communities. (C) Predicted functional diversity patterns estimated using the standard effects sizes (SES) of functional dispersion (FDis) along the gradient on slate (gray line) and wood (brown line) substrata and between wood falls (WF) and diffuse-flow hydrothermal vent (HV) communities (see *Material and methods* for details).</figcaption></figure>

the Eiffel Tower hydrothermal edifice in the Lucky Strike vent field (~1700 m depth, Mid-Atlantic Ridge). To compare faunal colonization on wood falls with that on slates, we used data from a parallel experiment where triplicate blocks of slates of the same size were deployed at the same sites and during the same time (Alfaro-Lucas et al., 2020). Temperature at each site was measured using NKE ST 6000 temperature probes to characterize

the gradient along sites (mean temperature [T], temperature range, pH, and hydrothermal fluid [HVF] inputs; Alfaro-Lucas et al., 2020). Both the “active” and “intermediate” sites are located in warm (T = 7.93 ± 2.13°C and 5.79 ± 0.77°C, respectively), fluctuating (T range = 16.91 and 7.67°C, respectively), and diffuse-flow areas (HVF = 1.1 and 0.44%; pH = 6.15 and 6.7) at the base of the Eiffel Tower. These sites are
colonized by the chemosymbiotic ecosystem engineer mussel *Bathymodiolus azoricus*, which forms dense beds. The “periphery” and “far” sites are neither directly influenced by vent fluids nor colonized by *B. azoricus* and are characterized by lower and more stable temperatures (periphery: T = 4.62 ± 0.07°C, T range = 0.49°C, pH = 7.27, HVF = 0.07%; far: T = 4.55 ± 0.07°C, T range = 0.44°C, pH = 7.31, HVF = 0.05%). They correspond to poorly sedimented and bare-basalt areas, respectively. Methods of wood sampling and faunal processing were identical to those in Alfaro-Lucas et al. (2020) for slates. In short, woods were deployed during the MoMARSAT2013 (10.17600/13030040) and retrieved during MoMARSAT 2015 (10.17600/15000200) cruises, using the R/V *Pourquoi Pas*? and ROV *Victor6000*. They were recovered individually in isothermal sampling boxes, washed on board with filtered seawater, and sieved through 20 and 300-µm mesh to easily separate groups typically belonging to meiofauna from those belonging to macrofauna. Typical meiofaunal groups (nematodes, copepods, halacarids, and ostracods) were not considered in this study. We manually sorted all sieved samples under a stereo microscope, counted, and identified each macrofaunal individual to the lowest taxonomic level possible. Larvae and individuals without heads were not considered. For the 20-µm fraction (20–<300 µm), we transferred each sample to 200-mL beakers and obtained three subsamples of 5 mL each. Following Plum et al. (2017), we extrapolated the average number of juvenile individuals of species that typically belong to macrofauna (e.g., polychaetes, mollusks) per subsample to the original sample volume and summed to those found in the 300-µm fraction.

## Species and functional diversity and community structure

For each substratum, we estimated the abundance of individuals (N) and species diversity using Hill numbers (D) of q orders 0 and 2. ⁰D is the number of species, or species richness, and gives equal weight to abundant and rare species, whereas ²D is the Simpson index, giving more weight to the dominant species (Jost, 2006; Roswell et al., 2021). We analyzed diversity patterns along the temperature gradient with regression models using the functions *lm* of the *stats* R package (R Development Core Team, 2020).

For each species, three life-history, “response” traits (sensu Lavorel & Garnier, 2002) related to energy availability and environmental stress (adult mobility, maximum body size, and feeding strategy) were measured and/or obtained from the literature, the sFDVent

database (Chapman et al., 2019) and expert opinions (Appendix S1: Tables S1 and S2). Based on their trait categories, species were classified in unique combinations of traits (UTC) and weighted by species abundances for posterior analyses of the functional structure of assemblages. For each substratum, we estimated the functional dispersion (FDis) using the function *fdisp* of the R package *FD* (Laliberté & Legendre, 2010). FDis is the mean functional distance of species to the functional mean (centroid) of species in a given community (Laliberté & Legendre, 2010). Thus, high FDis equals more dissimilar species within a given community and hence higher functional diversity. FDis is unaffected by species richness and outliers and can be estimated for individual traits (Laliberté & Legendre, 2010). We computed the FDis using all traits and for each trait individually to determine whether distinct assembly processes act on traits related to different niche dimensions (e.g., Cisneros et al., 2017; Spasojevic & Suding, 2012).

To compare species and UTC community structures, we ran a multiple factor analysis (MFA) and computed the RV coefficient, which measures the relatedness of two datasets derived from separate ordinations ranging from 0 (no correlation) to 1 (Robert & Escoufier, 1976), using the FactoMineR package (Lê et al., 2008).

## Null models and standard effect sizes of functional diversity patterns

To inform about the niche space increase/reduction and the underlying community assembly processes, trait diversity patterns were compared to null patterns discounting the effect of species richness. In other words, we determined whether observed values were lower, higher, or as expected based on a null expectation (e.g., Mouillot et al., 2014; Villéger et al., 2008). Typically, values lower than expected, that is, under-dispersed, are considered indicative of niche reduction due to environmental filtering or competitive dominance leading to a convergence of traits. Values higher than expected, that is, over-dispersed, are indicative of niche expansion due to competition exclusion processes or niche partitioning leading to a divergence of traits. Last, values as expected are indicative of no assembly processes acting on traits. To test our predictions properly, we developed two different null models where we fixed different factors to derive null expectations of FDis and compared those with the observed FDis values (Figure 1B,C).

The first null model consisted of randomizing species along the four sites across slate and wood substrata separately (Figure 1B). By doing so, we tested the effect of the stress-productivity gradient on traits while keeping
the potential effects of the substratum nature fixed (Figure 1B). The second null model randomized species occurring on slates under the direct influence of vent fluids and woods at sites without direct vent fluid influence to fix the factors driving, respectively, chemosynthesis-based diffuse-flow vent and wood-fall communities (Figure 1B). Models consisted of randomizations of species across substrata and sites analyzed at each model while maintaining the total species richness per substratum constant, using the function *randomizeMatrix* of the *picante* R package (Kembel et al., 2010). We compared the observed FDis to those obtained from randomizations using the standard effect sizes (SESs) (Gotelli & McCabe, 2002):

$$SES = (FDis_{obs} - FDis_{null mean})/FDis_{null SD}$$

where FDisobs is the observed FDis at a given substrata, and FDisnull mean and FDisnull SD are the mean and standard deviation of simulated FDis for that given substrata, respectively. Negative SES values are indicative of underdispersion, whereas positive values are indicative of over-dispersion. In null model 1, we evaluated the SES trends values along the temperature gradient with regression linear models using the function *lm* of the *stats* R package (R Development Core Team, 2020). The selection of the model was based on Akaike information criterion (AIC). In null model 2, we compared the SES values of wood fall and diffuse-flow vent communities with a t-test using the function *t.test* of the *statst* R package (R Development Core Team, 2020). SES values below -1.96 were considered significantly under-dispersed, whereas values over 1.96 were considered significantly over-dispersed (Gotelli & McCabe, 2002).

## Stable isotope analyses

We measured the δ¹³C, δ¹⁵N, and δ³⁴S isotope ratios of 213 samples belonging to 35 species from wood substrata and complemented them with 102 samples belonging to 16 species from slate substrata obtained from Alfaro-Lucas et al. (2020). For relatively large taxa, muscle tissue was used. Guts and calcareous structures were removed manually whenever possible. “Champagne tests” (sensu Jaschinski et al., 2008) were used to highlight the presence of carbonates in tissues and, when positive, samples were acidified by exposing them to HCl vapors for 48 h in an airtight container to eliminate inorganic carbon (Hedges & Stern, 1984). After acidification, a second “champagne test” series was run. When the second test was still positive, we proceeded with direct acidification (0.2 mL of 10% HCl added directly to the sample in a

silver cup) (Jaschinski et al., 2008). Both vapor and direct acidification procedures efficiently remove carbonates without altering δ¹⁵N values (Jaschinski et al., 2008; Lorrain et al., 2003). Isotope analyses were done at the University of Liege (Belgium) using a vario MICRO cube (Elementar, Germany) elemental combustion system coupled to an IsoPrime100 (Elementar, United Kingdom) isotope ratio mass spectrometer. Isotope ratios were expressed using the widespread δ notation (Coplen, 2010), in per-mille and relative to the international references Vienna Pee Dee Belemnite (for carbon), Atmospheric Air (for nitrogen), and Vienna Canyon Diablo Troilite (for sulfur). IAEA (International Atomic Energy Agency, Vienna, Austria) certified reference materials sucrose (IAEA-C-6; δ¹³C = -10.8‰ ± 0.5‰; mean ± SD), ammonium sulfate (IAEA-N-1; δ¹⁵N = 0.4‰ ± 0.2‰; mean ± SD), and silver sulfide (IAEA-S-1 δ³⁴S = -0.3‰) were used as primary analytical standards. Sulfanilic acid (Sigma-Aldrich; δ¹³C = -25.6‰ ± 0.4‰; δ¹⁵N = -0.13‰ ± 0.4‰; δ³⁴S = 5.9‰ ± 0.5‰; means ± SD) was used as a secondary analytical standard. SDs on multi-batch replicate measurements of secondary and internal lab standards (seabass muscle) which were interspersed with samples (one replicate of each standard every 15 analyses) were 0.2‰ for both δ¹³C, 0.3‰ for δ¹⁵N, and 0.5‰ for δ³⁴S.

The δ¹³C and δ¹⁵N values were obtained for all species and used to identify the diversity of energy acquisition pathways using range values. At vents, δ¹³C values ranging from -16.3‰ to -9.5‰ reflect the reductive tricarboxylic acid cycle (rTCA), while those from -36‰ to -30‰ correspond to the Calvin-Benson-Bassham (CBB) cycle (Portail et al., 2016; Reid et al., 2013). Stable nitrogen isotope values reflect two large inorganic sources with very different signatures, that is, nitrates (δ¹⁵N = 5‰-7‰) and ammonium (δ¹⁵N < 0‰) (Lee & Childress, 1996; Riekenberg et al., 2016). Given insufficient amounts of tissue, δ³⁴S values were only obtained for a total of 27 species from wood and slate substrata and were used to identify resource origin. Values of δ³⁴S around or below 10‰ indicate producers using sulfides (here, organic matter of chemosynthetic origin), while those around or over 16‰ indicate producers using sulfates (here, organic matter of photosynthetic origin) (Reid et al., 2013).

## RESULTS

We identified 67 species colonizing the wood blocks. Including the 42 macrofaunal taxa reported on slate blocks by Alfaro-Lucas et al. (2020), the dataset analyzed here comprised 73 species (Appendix S1: Table S3). On slate substrata, we observed a significant quadratic
(hump-shaped) relationship between the number of species ($^0D$) ($F_{2,9} = 13.82, p = 0.02$) and individuals ($N$) ($F_{2,9} = 86.17, p < 0.001$) with temperature increasing from peripheral sites without direct vent fluid influence (4.55–4.62°C) to diffuse-flow sites directly influenced by fluids (5.79–7.93°C) (Figure 2A,C). On wood substrata, we observed a significant, yet negative, linear and quadratic relationship between $^0D$ ($F_{1,10} = 5.07, p = 0.04$) and $N$ ($F_{2,9} = 11.63, p = 0.03$), respectively, with temperature decreasing from peripheral sites to diffuse-flow sites (Figure 2B,D). Simpson ($^2D$) diversity showed no significant relationship along the gradient both on slate

($F_{1,10} = 0.61, p = 0.45$) and wood substrata ($F_{1,10} = 0.60, p = 0.46$) (Figure 2E,F).

## Species and functional community structure

The multiple factor analysis showed that species and trait combinations (UTC) clustered similarly into three assemblages (Figure 3). The high and significant RV coefficient (0.91, $p < 0.001$) also suggested that species and UTCs were structured in a comparable pattern. The first MFA

<figure><img src="image_3.png" /><figcaption>**FIGURE 2** Species diversity patterns along the concomitant environmental stress and productivity gradient on slate and wood substrata. (A, C, E) Slate substrata. (B, D, F) Wood substrata. $^0D$, species richness; $\log_{10}(N)$, abundance of individuals; $^2D$, Simpson diversity index. Regression lines are shown for significant relationships.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**FIGURE 3** Multiple factor analysis (MFA) of species and unique trait combination (UTC) assemblages along the concomitant environmental stress and productivity gradient on slate and wood substrata. (A) Individual factor map along the first and second MFA axes. Substrata position in partial principal components analyses (PCAs) for species and UTCs are showed with dashed red and green lines, respectively. The positions of substrata on the global PCA is represented with dots (slate) and squares (wood). (B) Correlation circle showing the main taxa and UTCs contributing to the ordination of substrata along the first and second axes. Species: 1, *Branchipolynoe seepensis*; 2, *Protolira valvatoides*; 3, *Pseudorimula midatlantica*; 4, *Lepetodrilus atlanticus*; 5, *Bathymodiolus azoricus*; 6, *Amphisamya lutzi*; 7, *Ophryotrocha fabriae*; 8, *Capitella* sp.; 9, *Idas* sp.; 10, *Strepternos* sp.; 11, Hesionidae sp.; 12, *Coccopigya spinigera*; 13, *Xyloredo* sp.; 14, *Sirsoe* sp.; 15, Flabelligeridae sp.; 16, *Asellota* sp. 2; 17, Liljeborgiidae sp.; 18, *Lurifax vitreus*; 19, *Glycera tesselata*, UTCs: SS, sessile; Fac, facultative; S, slow; F, fast. 1, ≥1 to <5 mm; 2, ≥5 to <10 mm; 3, ≥10 to <15 mm; 4, ≥15 to <20 mm; 5, ≥20 mm. SYc, chemosymbiotic; G, grazer; DF, deposit feeder; P, predator.</figcaption></figure>

axis (43.3% of the total variation) separated wood and slate substrata between those at diffuse-flow sites under direct fluid influence (higher temperature, i.e., 5.79–7.93°C) and those at peripheral sites without fluid influence (lower temperature, i.e., 4.55–4.62°C) (Figure 3A). The second axis (21.1% of the total variation) further separated slate from wood substrata at peripheral sites without fluid influence (Figure 3A).

Assemblages on slate and wood substrata at diffuse-flow sites were colonized by “common” diffuse-flow vent inhabitants and were mainly characterized by annelids, gastropods, and the main vent ecosystem engineer *Bathymodiolus azoricus* mussel (Figure 3B). These assemblages were characterized by various UTCs representing several mobility, size, and feeding categories, including chemosymbiosis and large size, especially on wood substrata (Figure 3B; Appendix S1: Figure S1). Assemblages on slates at peripheral sites without fluid influence were colonized by species typically found at the vent periphery, for example, the annelid *Glycera tesselata*, gastropod *Lurifax vitreus*, amphipods, and isopods (Figure 3B). These peripheral assemblages were characterized by

UTCs showing mainly slow mobility, relatively small sizes (1–10 mm), and deposit feeder and predatory habits (Figure 3B; Appendix S1: Figure S1). Assemblages colonizing wood substrata at sites without fluid influence formed “typical” wood-fall communities, with several species of wood-fall annelids (*Capitella* sp., *Strepternos* sp., and *Sirsoe* sp.), *Idas* mussels, and wood-boring *Xyloredo* species (Figure 3B). These wood-fall assemblages were characterized by overall small-sized UTCs (1–10 mm) with several mobility and feeding trait categories, including both chemosynthetic and heterotrophic symbioses (Figure 3B; Appendix S1: Figure S1).

## Null models of functional diversity

The first null model (Figure 1B) revealed a significant quadratic relationship in the standard effect size of functional dispersion (FDist SES) on both slate ($F_{2,9} = 5.58, p = 0.03$) and wood ($F_{2,9} = 36.01, p < 0.001$) substrata along the hydrothermal gradient, with values increasing from peripheral sites without direct vent fluid influence
<figure><img src="image_5.png" /><figcaption>**FIGURE 4** Standard effect sizes (SES) of functional dispersion on slate and wood faunal communities. (A–H) SES patterns from the first null model (see Figure 1 and *Material and Methods*) based on the functional dispersion calculated using all traits (FDis) and individual traits (FDis mobility, FDis size, and FDis feeding) for slate (A–D) and wood (E–H) communities. Regression lines are shown for significant relationships. (I–L) SES patterns from the second null model based on the functional dispersion calculated using all traits (FDis), and individual traits (FDis mobility, FDis size, and FDis feeding) for wood substrata at peripheral sites forming typical wood-fall communities (WF) and slate substrata at diffuse-flow sites forming diffuse-flow hydrothermal vent (HV) communities. Boxes represent the interquartile range (IQR) containing the middle 50% of the data between the first quartile (Q1, 25th percentile) and the third quartile (Q3, 75th percentile). The horizontal lines inside boxes mark the median (Q2, 50th percentile). The whiskers extend to the smallest and largest data points within 1.5 times the IQR from Q1 and Q3, respectively. Asterisks denote significant differences between WF and HV. Values outside shaded gray areas represent values significantly lower (<−1.96) and higher (>1.96) than expected based on null model randomizations.</figcaption></figure>

to diffuse-flow sites directly influenced by fluids (Figure 4A,E). On slate substrata, only FDis SES for size showed a significant (quadratic) relationship along the gradient ($F_{2,9} = 38.42, p < 0.001$) (Figure 4C). On wood substrata, both FDis SES for mobility and size showed a quadratic relationship along the gradient (FDis SES mobility $F_{2,9} = 12.02, p = 0.004$; FDis SES size $F_{2,9} = 19.65, p < 0.001$), while FDis SES for feeding increased linearly ($F_{1,10} = 8.06, p = 0.018$) (Figure 4F–H).

The second null model (Figure 1C) revealed a significant difference in FDis SES between typical wood-fall communities on wood substrata at sites without direct vent fluid influence and diffuse-flow hydrothermal

vent communities on slate substrata at sites under direct vent fluid influence (i.e., $t_{10} = 5.22, p < 0.001$) (Figure 4I). FDis SES for size also showed significant differences between typical wood-fall and diffuse-flow hydrothermal vent communities ($t_{10} = 13.56, p < 0.001$) (Figure 4K), whereas FDis SES for mobility and feeding did not differ significantly (Figure 4J,L).

## Stable isotope analyses

Across the entire dataset, the $\delta^{13}$C values ranged from −33.09‰ (*Bathymodiolus azoricus* on slate at 5.79°C) to
<figure><img src="image_6.png" /><figcaption>**FIGURE 5** Legend on next page.</figcaption></figure>
-15.45‰ (Divia briandi on wood substrata at 5.79°C) (Figure 5A,B). The δ¹⁵N values ranged from -13.9‰ (B. azoricus on wood substrata at 5.79°C) to 9.89‰ (Lepidonotopodium sp. on slate at 4.55°C) (Figure 5A; Appendix S1: Table S4). The δ³⁴S values ranged from 1.14‰ (Branchipolynoide seepensis on wood at 7.93°C) to 17.84‰ (Coccopigya spinigera on wood substrata at 4.55°C) (Figure 5B).

Species isotopic δ¹³C and δ¹⁵N ranges were broader on substrata at higher temperatures than those at lower temperatures. For instance, slates at 7.93 and 5.79°C showed wide isotopic ranges (δ¹³C range = 13.43‰ and 12.86‰; δ¹⁵N range = 16.21‰ and 14.78‰, respectively), whereas slates at 4.62°C had more restricted ranges (δ¹³C range = 5.38‰, δ¹⁵N range = 4.19‰). Similarly, wood substrata at 7.93 and 5.79°C exhibited broader isotopic variability (δ¹³C range = 10.48‰, 17.45‰; δ¹⁵N range = 16.73‰ and 20.9‰, respectively) than those at 4.62 and 4.55°C (δ¹³C range = 5.55‰ and 6.8‰; δ¹⁵N range = 7.35‰ and 7.73‰, respectively) (Figure 5A).

Species on substrata at higher temperatures (7.93 and 5.79°C) generally showed δ³⁴S values around or below 10‰, consistent with a dominant chemosynthetic production pathway. By contrast, species at lower temperatures (4.62 and 4.55°C) matched values expected for organic matter of photosynthetic origin (Figure 5B). However, exceptions were observed. The wood-boring bivalve *Xylophaga* spp., found on wood at 7.93 and 5.79°C, had δ³⁴S values well above 10‰, suggesting a reliance on photosynthetically derived organic matter, most likely the wood itself (Figure 5B). Conversely, some species on wood substrata at lower temperatures (4.62 and 4.55°C) showed δ³⁴S values lower than 10‰, for example, the polychaete *Sirsoe* sp. (δ³⁴S = 6.84‰) and gastropod *Protolira valvatoides* (δ³⁴S = 4.7‰), rather reflecting reliance on chemosynthetic production (Figure 5B).

## DISCUSSION

Our artificial substrata were successfully colonized by distinct faunal assemblages along the environmental gradient as intended. Nevertheless, we found only partial support for our main hypothesis. We hypothesized that, on slate and wood substrata at vent diffuse-flow habitats and wood substrata at periphery sites, high productivity would promote niche space expansion due to niche partitioning and/or competitive exclusion of functionally similar species, despite the associated environmental stress. Instead, species, trait, and isotopic patterns suggest more complex effects of stress, productivity, and habitat constraints on the assembly of communities along the environmental stress-productivity gradient at vents and at wood falls.

## Different processes and constraints drive the assembly of communities along the concomitant stress and productivity gradient at hydrothermal vents

From vent periphery to diffuse-flow sites, slate substrata were colonized by typical vent periphery and diffuse-flow vent assemblages, respectively (Figures 3 and 6) (e.g., Desbruyères et al., 2001; Sarrazin et al., 2015). The increase in functional diversity from vent periphery to diffuse-flow sites on slate substrata suggests niche space expansion and that different processes and constraints drive vent community assembly along the concomitant environmental stress-productivity gradient, as previously hypothesized (e.g., Alfaro-Lucas et al., 2020; Micheli et al., 2002; Mullineaux et al., 2003). Nevertheless, we found that the species and functional diversity increases along this gradient are hump-shaped, suggesting that vent community assembly processes are driven by a trade-off between stress and productivity (Figures 4 and 6).

**FIGURE 5** Mean isotopic composition of species along the concomitant gradient of environmental stress and productivity on slate and wood substrata. (A) δ¹³C/δ¹⁵N and (B) δ¹³C/δ³⁴S mean isotopic composition of species, with adjunct isotopic ranges (δ¹³C and δ¹⁵N) and boxplots (δ³⁴S) displaying the distribution of values throughout the isotopic space. Species: 1, *Alvinocaris* sp.; 2, *Amphisamytha lutzi*; 3, *Bathymodiolus azoricus*; 4, *Branchipolynoë seepensis*; 5, *Capitella* sp. 1; 6, *Capitella* sp. 5; 7, *Coccopigya spinigera*; 8, *Divia briandi*; 9, *Glycera tesselata*; 10, Hesionidae sp. 3; 11, Hesionidae sp. 4; 12, *Heteromesus* sp.; 13, *Idas* sp.; 14, *Laonice athecate*; 15, *Lepetodrilus atlantica*; 16, *Lepidonotopodium* sp.; 17, *Liljeborgiidae* sp.; 18, *Lirapex costellata*; 19, *Luckia striki*; 20, *Lurifax vitreus*; 21, *Macellicephaloides* sp.; 22, *Mirocaris fortunata*; 23, *Nemertea* sp.; 24, *Ophryotrocha cf. platykephale*; 25, *Ophryotrocha fabriae*; 26, *Paralepetopsis ferrugivora*; 27, *Paramytha* sp.; 28, *Phymorrinchus* sp.; 29, *Prionospio unilamellata*; 30, *Protolira valvatoides*; 31, *Pseudorimula midatlantica*; 32, *Sirsoe* sp.; 33, *Storthyngura* sp.; 34, *Strepternos* sp.; 35, *Turbellaria* sp.; 36, *Xylophaga* spp.; 37, *Xyloredo* spp. Boxplots in B represent the interquartile range (IQR) containing the middle 50% of the data between the first quartile (Q1, 25th percentile) and the third quartile (Q3, 75th percentile) (boxes). The horizontal lines inside boxes mark the median (Q2, 50th percentile). The whiskers extend to the smallest and largest data points within 1.5 times the IQR from Q1 and Q3, respectively. Isotopic values of slate at 4.62°C were not represented in ranges and boxplots because there was only one value available (green dot in A, species 17).
<figure><img src="image_7.png" /><figcaption>**FIGURE 6** Conceptual model of community assembly processes and constraints acting at eco-evolutionarily related wood-fall and hydrothermal vent communities. The high food resources in typical wood-fall communities support very speciose and dense communities characterized by a low functional diversity, suggesting environmental filtering and/or competitive dominance of specific functional groups. Along the concomitant stress-productivity gradient at hydrothermal vent habitats, the hump-shaped patterns of species richness, abundance, and functional diversity suggest that different processes and constraints drive the assembly of communities. Environmental filtering related to food scarcity likely drives the assembly of communities at the vent periphery. At moderate levels of stress at diffuse-flow habitats, productivity supports species-rich and dense assemblages with high functional diversity, suggesting niche partitioning and/or competitive exclusion processes. As stress increases in habitats under higher venting influence, species richness, abundance, and functional diversity decrease, suggesting environmental filtering and/or competitive dominance of certain functional groups. Illustration credit: Joan M. Alfaro-Lucas.</figcaption></figure>

The low functional diversity at the vent periphery suggests that environmental filtering drives the assembly of communities at these sites (Figures 4 and 6). This pattern could also be caused by the competitive dominance of species belonging to a few specific functional groups (Kraft et al., 2015; Violle et al., 2010). However, the low number of species and individuals (Figure 2), and the scarce resource use (narrow isotopic $\delta^{13}$C, $\delta^{15}$N, and $\delta^{34}$S ranges) (Figure 5), suggests that assemblages of only well-adapted species with low-density populations and few trophic levels are sustained in these low-energy regimes (Cadotte & Tucker, 2017; Post, 2002). Indeed, these assemblages were characterized mainly by smaller species, suggesting that the poverty of resources filters for a small body size and does not support the larger species observed in vent diffuse-flow assemblages (e.g., Gollner et al., 2015) (Figure 3). Therefore, it is likely that energetic constraints reduce

niche space, act as a main environmental filter, and drive the assembly of communities at the vent periphery (Figure 6).

As chemosynthetic productivity increases in diffuse-flow sites with moderate levels of environmental stress (i.e., 5.79°C), the functional diversity peaks on slate substrata (Figures 4 and 6). This functional increase indicates that species display a high diversity of ecological strategies. In parallel, the number of species and individuals also peaks, as is usually observed at intermediate diffuse-flow vent assemblages (Cuvelier et al., 2009; Gollner et al., 2015; Sarrazin et al., 2015) (Figure 2). The observed higher use of resources (large $\delta^{13}$C and $\delta^{15}$N ranges) likely supports the many ecological strategies and trophic levels (Post, 2002) (Figure 5), allowing the establishment of speciose and dense assemblages. This niche expansion is thus driven by niche partitioning (e.g., Alfaro-Lucas et al., 2020; Bryant & McClain, 2022;
Govenar et al., 2015; Levesque et al., 2003) and/or competitive exclusion processes of functionally similar species (e.g., Kraft et al., 2015; Mayfield & Levine, 2010). Indeed, it is possible that both processes are acting together and promote the high species richness and densities observed. Competitive exclusion processes could prevent the colonization of certain functionally similar species, while simultaneously, niche partitioning could allow the establishment of other functionally distinct species (e.g., Cisneros et al., 2014; Spasojevic & Suding, 2012).

As environmental stress increases in diffuse-flow areas under higher venting influence (7.93°C), the functional diversity decreases on slate substrata (Figure 4), suggesting a niche reduction due to environmental filtering and/or competitive dominance of specific functional groups (Cadotte & Tucker, 2017; Violle et al., 2010). There, species assemblages are very similar to those in diffuse-flow areas of moderate environmental stress (Figure 3). However, the number of species and individuals declines (Figure 2), despite a similar or even higher use of chemosynthetic resources (larger δ¹³C and δ¹⁵N ranges) (Figure 5). Thus, the higher environmental stress probably benefits species with specific traits that can outcompete lower competitors (Cadotte & Tucker, 2017; Violle et al., 2010), leading to the observed diversity patterns (Figure 6).

The similar hump-shaped functional diversity pattern observed on wood substrata along the gradient was not expected (Figure 4). Wood substrata at sites under fluid influence harbored very similar assemblages to those found on slates from the same sites, that is, fauna mainly belonging to vent diffuse-flow habitats (Figure 3). This suggests, as previously observed elsewhere, a limited role of the substratum nature in community assembly under high environmental stress regimes (e.g., Baldrighi et al., 2018; Cuvelier et al., 2014; Pereira et al., 2022; Plum et al., 2017; Zeppilli et al., 2015). However, wood substrata at diffuse-flow sites also attracted some wood-fall specialists, such as wood-boring bivalves *Xylophaga* spp., and organisms belonging to groups previously found only on slate at the periphery sites, such as amphipods and isopods (Alfaro-Lucas et al., 2020; Cuvelier et al., 2014). Indeed, wood substrata at moderate levels of environmental stress (i.e., 5.79°C) showed the largest δ¹³C range and species with surprisingly high δ³⁴S values (e.g., *Xylophaga* sp.) (Figure 5), suggesting that some species feed not only on organic matter of chemosynthetic origin but also on material derived from wood. This explains why, in addition to body size as observed on slates, the diversity of mobility and feeding strategies also increases (Figure 4). We hypothesize that in the already highly productive vent diffuse-flow habitats, wood substrata represent an addition of resource, allowing species with new ecological strategies to establish in comparison with vent

diffuse-flow assemblages on slates. This would also explain why this wood supports more species and individuals than slate in both high and intermediate stress vent diffuse-flow areas but not why the functional diversity increases on wood substrata from periphery to diffuse-flow sites (see discussion below).

## Wood-fall habitats filter for specific species traits, reducing functional diversity

Wood substrata at periphery sites supported typical wood-fall assemblages (e.g., Bernardino et al., 2010; Bienhold et al., 2013; Gaudron et al., 2010). The number of species and individuals was higher on these wood substrata than on slate substrata at any other site (Figure 2). These speciose and dense wood-fall assemblages were likely supported by the diversity of resources from both in situ chemosynthetic production and wood origin (Bienhold et al., 2013; McClain et al., 2016; Turner, 1978), as highlighted by the large range of δ³⁴S values (Figure 5). There, some species exhibited a strong reliance on chemosynthetic production, for example, the polychaete *Sirsoe* sp. (δ³⁴S = 6.84) and the gastropod *Protolira valvatoides* (δ³⁴S = 4.7) (Figure 5), and some even exploited very similar chemosynthetic niches to those found at hydrothermal vent diffuse-flow sites. For instance, *P. valvatoides* showed remarkably similar δ¹³C, δ¹⁵N, and δ³⁴S compositions between wood-fall assemblages at the periphery and vent diffuse-flow assemblages (Figure 5). Evidence of chemosynthetic niches and their exploitation by vent fauna within typical wood-fall assemblages supports the hypothesis that organic falls could act as ecological stepping stones for the dispersal of some vent and seep species (Distel et al., 2000; Pereira et al., 2020, 2022; Shimabukuro et al., 2019; Smith et al., 2015). In fact, we found 15 species shared between wood substrata at periphery sites harboring typical wood-fall assemblages and typical vent diffuse-flow assemblages on slate (Appendix S1: Figure S2). This represents 33.33% of the total species colonizing wood substrata at periphery sites and 55.55% of the total species colonizing slate at diffuse-flow habitats (Appendix S1: Figure S2). Nevertheless, despite the speciose and abundant assemblages, the functional diversity of typical wood-fall assemblages at the vent periphery was lower than that of both vent diffuse-flow assemblages on slates and woods (Figure 4), contradicting our hypothesis.

Indeed, despite some taxonomic and trophic similarities, the overall species and functional structures differed between typical wood-fall assemblages at the vent periphery and vent diffuse-flow assemblages on slate and wood
(Figure 3). Large flagship ecosystem-engineer vent species, such as *Bathymodiolus azoricus* mussels, were not found in typical wood-fall assemblages at the vent periphery. Instead, the confamilial, also chemosymbiotic yet smaller genus of mussels, *Idas*, was abundant. In fact, species in typical wood-fall assemblages at the vent periphery were mainly intermediate-sized taxa, whereas in vent diffuse-flow assemblages found on slate and wood, larger species were relatively common (Figure 3). There, cognate species such as *B. azoricus* can reach greater sizes because of the higher habitat availability and access to longer lasting, more intense vent-fluid reduced compound fluxes that fuel chemosynthesis (e.g., Duperron et al., 2009; Laming et al., 2018). Larger size would also be advantageous to cope with the more dynamic and stressful vent conditions (Gollner et al., 2015; Vanreusel et al., 2010). Thus, we hypothesize that the smaller colonization surface and shorter longevity of wood-fall habitats have acted as evolutionary filters favoring certain optimal traits, such as smaller body size. This hypothesis could explain why, even if energy is not a limiting factor in typical wood-fall assemblages at the vent periphery, some functional strategies are not observed, while others are disproportionately favored as previously observed in wood-fall habitats (Judge & Barry, 2016; McClain & Barry, 2014; McClain, Barry, & Webb, 2018; McClain, Nunnally, et al., 2018). This leads to the observed lower functional diversity compared to vent diffuse-flow assemblages. Therefore, we hypothesize that although the abundant resources in wood falls support speciose and dense communities, habitat constraints favor species with certain traits, acting as an environmental filter and/or inducing competitive dominance of specific functional groups (Figure 6).

In conclusion, our results suggest that different processes and constraints drive the assembly of communities along hydrothermal vents, from periphery to diffuse-flow habitats, and between the eco-evolutionarily related communities of diffuse-flow vents and wood-fall habitats. Our findings pave the ground to design specific experiments that could potentially distinguish between community assembly processes with similar outcomes, for example, environmental filtering versus competitive dominance and niche partitioning versus competitive exclusion (e.g., Kraft et al., 2015). Future experiments should also aim to disentangle the interacting effects and relative importance of other processes not tested here, such as predation and facilitation, in the assembly of communities at deep-sea chemosynthesis-based habitats (e.g., Micheli et al., 2002; Mullineaux et al., 2003). Moreover, it is also important to highlight that the size of our colonizing substrata was small, and evidence

suggests that larger organic falls enhance chemosynthetic production (Cunha et al., 2013; McClain et al., 2016; Smith & Baco, 2003). Future studies should test whether increases in wood-fall size promote similar community assembly processes to those observed at vent diffuse-flow habitats and enhance species and functional similarities or, alternatively, create even more dissimilar assemblages.

## AUTHOR CONTRIBUTIONS

Joan M. Alfaro-Lucas, Daniela Zeppilli, Florence Pradillon, Loïc N. Michel, and Jozée Sarrazin were involved in the conceptualization, methodology, and resources of the study. Joan M. Alfaro-Lucas and Martin Foviaux were involved in the software, formal analyses, and investigation. Joan M. Alfaro-Lucas, Daniela Zeppilli, Maurício Shimabukuro, Loïc N. Michel, Pedro Martinez-Arbizu, Hayato Tanaka, Gauthier Schaal, and Martin Foviaux were involved in the data curation process. Joan M. Alfaro-Lucas wrote the original draft. All authors were involved in writing—review and editing of the final draft. Daniela Zeppilli, Florence Pradillon, Loïc N. Michel, Gauthier Schaal, and Jozée Sarrazin were involved in supervision, project administration, and funding acquisition.

## ACKNOWLEDGMENTS

We thank the captains and crews of R/V *Pourquoi Pas?*, pilots of ROV *Victor6000*, and technicians and engineers from the Biology and Ecology of Deep Sea Ecosystems lab (Ifremer, Brest) for their assistance at sea and in the lab. We thank Dr. P. Bonifacio (Ifremer, Brest), A. Warén (SMNH, Stockholm), L. Corbari (MNHN, Paris), and C. Romano (USGP, Pollenzo) for their invaluable help with species identifications. We thank Dr. A. E. Bates (UVic, Victoria) and A. Chapman (UCL, London) for access to an early version of the sFDVent database and helpful discussions. Dr. O. Gauthier (IUEM/UBO, Brest) and C. Rommevaux (MIO, Marseille) are acknowledged for helpful advice on early analyses of this manuscript. J. M. A.-L.'s PhD scholarship was supported by the "Laboratoire d'Excellence" LabexMER (ANR-10-LABX-19), co-funded by a grant from the French government as part of the "Investissements d'Avenir" program and by IFREMER. The research program was funded by an ANR research grant (ANR Lucky Scales ANR-14-CE02-0008-02). We also acknowledge the project PIONEER funded by Ifremer and Total Foundation. The project is part of the EMSO-Azores regional node within EMSO-France (http://www.emso-fr.org) and of the EMSO ERIC Research Infrastructure (http://emso.eu/).

## CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.
# DATA AVAILABILITY STATEMENT

Data (Alfaro-Lucas et al., 2019) are available from the SEANOE repository: https://doi.org/10.17882/90419.

# ORCID

Joan M. Alfaro-Lucas https://orcid.org/0000-0001-5725-3218

Florence Pradillon https://orcid.org/0000-0002-6473-6290

Daniela Zeppilli https://orcid.org/0000-0002-0809-2566

Maurício Shimabukuro https://orcid.org/0000-0002-1572-8542

Gauthier Schaal https://orcid.org/0000-0003-3860-1517

Loïc N. Michel https://orcid.org/0000-0003-0988-7050

Pedro Martinez-Arbizu https://orcid.org/0000-0002-0891-1154

Hayato Tanaka https://orcid.org/0000-0003-1237-8855

Jozée Sarrazin https://orcid.org/0000-0002-5435-8011

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## SUPPORTING INFORMATION

Additional supporting information can be found online in the Supporting Information section at the end of this article.

**How to cite this article:** Alfaro-Lucas, Joan M., Florence Pradillon, Daniela Zeppilli, Maurício Shimabukuro, Gauthier Schaal, Loïc N. Michel, Pedro Martinez-Arbizu, Hayato Tanaka, Martin Foviaux, and Jozée Sarrazin. 2025. "Different Processes and Constraints Drive the Assembly of Deep-Sea Hydrothermal Vent and Sunken Wood Communities." *Ecosphere* 16(8): e70351. https://doi.org/10.1002/ecs2.70351