Abundance Of Epifauna Research Articles

Variability of marine epifauna assemblages in response to the microhabitat type and thermal stress

Anthropogenic activities like overfishing, urban and industrial developments, and coastal pollution are some of the stressors affecting the marine environment. Thermal pollution from coastal industries like power plants represents the main cause of increased temperatures in water bodies, which can affect the marine community structure and function. The aim of this study was: 1) to compare the epifaunal communities associated with three different types of microhabitats: articulated coralline algae around coral colonies (CWC), articulated coralline algae in the absence of coral colonies and other benthic organisms (CNB), and the seaweed Ecklonia cava (ECK); and 2) to determine the potential changes in epifaunal communities in acute response to the increased water temperature resulting from coastal power plant activities in Jeju Island, South Korea. Our findings revealed a strong association between epifaunal abundance and microhabitat type, with CNB exhibiting the highest abundance while ECK showed the lowest. Additionally, an increase in temperature of 0.5–1.5 °C was observed to not alter the overall abundance of epifauna at the impact site, however, it did lead to a shift in the community composition. There was a notable decline in the abundance of amphipods-caprellids, polychaetes, gastropods, and bivalves with their densities nearly halving in response to thermal stress. Furthermore, there was a shift in dominant taxa, transitioning from amphipods-caprellids to amphipods-non-caprellids. Conversely, other taxonomic groups such as isopods and copepods showed a remarkable surge in abundance following the temperature rise. These findings highlight the relationship between rising temperatures and epifaunal community composition while emphasizing taxa’s different responses to thermal stress.

Habitat traits and predation interact to drive abundance and body size patterns in associated fauna.

Habitat-forming organisms provide three-dimensional structure that supports abundant and diverse communities. Variation in the morphological traits of habitat formers will therefore likely influence how they facilitate associated communities, either via food and habitat provisioning, or by altering predator-prey interactions. These mechanisms, however, are typically studied in isolation, and thus, we know little of how they interact to affect associated communities. In response to this, we used naturally occurring morphological variability in the alga Sargassum vestitum to create habitat units of distinct morphotypes to test whether variation in the morphological traits (frond size and thallus size) of S. vestitum or the interaction between these traits affects their value as habitat for associated communities in the presence and absence of predation. We found morphological traits did not interact, instead having independent effects on epifauna that were negligible in the absence of predation. However, when predators were present, habitat units with large fronds were found to host significantly lower epifaunal abundances than other morphotypes, suggesting that large frond alga provided low-value refuge from predators. The presence of predators also influenced the size structure of epifaunal communities from habitat units of differing frond size, suggesting that the refuge value of S. vestitum was also related to epifauna body size. This suggests that habitat formers may chiefly structure associated communities by mediating size-selective predation, and not through habitat provisioning. Furthermore, these results also highlight that habitat traits cannot be considered in isolation, for their interaction with biotic processes can have significant implications for associated communities.

Facilitation of animals is stronger during summer marine heatwaves and around morphologically complex foundation species.

Foundation species create biogenic habitats, modify environmental conditions, augment biodiversity, and control animal community structures. In recent decades, marine heatwaves (MHWs) have affected the ecology of foundation species worldwide, and perhaps also their associated animal communities. However, no realistic field experiment has tested how MHWs affect animals that live in and around these foundation species. We therefore tested, in a four-factorial field experiment, if colonisation by small mobile marine animals (epifauna) onto plates with attached single versus co-occurring foundation species of different morphological complexities, were affected by 3-5°C heating (that mirrored a recent extreme MHW in the study area) and if the heating effect on the epifauna varied within and between seasons. For this experiment mimics of turf seaweed represented the single foundation species and holdfasts of seven common canopy-forming seaweed represented the co-occurring foundation species with different morphological complexities. We found that the taxonomic richness and total abundance of epifauna, dominated by copepods, generally were higher on heated plates with complex seaweed holdfasts in warmer summer trials. Furthermore, several interactions between test-factors were significant, e.g., epifaunal abundances, were, across taxonomic groups, generally higher in warmer than colder summer trials. These results suggest that, in temperate ecosystems, small, mobile, short-lived, and fast-growing marine epifauna can be facilitated by warmer oceans and morphologically complex foundation species, implying that future MHWs may increase secondary production and trophic transfers between primary producers and fish. Future studies should test whether these results can be scaled to other ecological species-interactions, across latitudes and biogeographical regions, and if similar results are found after longer MHWs or within live foundation species under real MHW conditions.

Habitat Provision and Erosion Are Influenced by Seagrass Meadow Complexity: A Seascape Perspective

Habitat complexity plays a critical role in shaping biotic assemblages and ecosystem processes. While the impacts of large differences in habitat complexity are often well understood, we know less about how subtle differences in structure affect key ecosystem functions or properties such as biodiversity and biomass. The late-successional seagrass Posidonia australis creates vital habitat for diverse fauna in temperate Australia. Long-term human impacts have led to the decline of P. australis in some estuaries of eastern Australia, where it is now classified as an endangered ecological community. We examined the influence of P. australis structural complexity at small (seagrass density) and large (meadow fragmentation) spatial scales on fish and epifauna communities, predation and sediment erosion. Fine-scale spatially balanced sampling was evenly distributed across a suite of environmental covariates within six estuaries in eastern Australia using the Generalised Random Tessellation Structures approach. We found reduced erosion in areas with higher P. australis density, greater abundance of fish in more fragmented areas and higher fish richness in vegetated areas further from patch edges. The abundance of epifauna and fish, and fish species richness were higher in areas with lower seagrass density (seagrass density did not correlate with distance to patch edge). These findings can inform seagrass restoration efforts by identifying meadow characteristics that influence ecological functions and processes.

Effect of Depth across a Latitudinal Gradient in the Structure of Rhodolith Seabeds and Associated Biota across the Eastern Atlantic Ocean

Rhodolith seabeds are ‘ecosystem engineers’ composed of free-living calcareous red macroalgae, which create extensive marine habitats. This study addressed how depth influenced the structure (size and morphology) of rhodoliths and the abundance of associated floral and faunal epibionts across the Eastern Atlantic Ocean. Sampling was carried out at two sites within five regions (Brittany, Galicia, Madeira, Gran Canaria, and Principe Island), from temperate to tropical, covering a latitudinal gradient of 47°, in three depth strata (shallow, intermediate and deep), according to the rhodolith bathymetrical range in each region. Depth typically affected the rhodolith size at all regions; the largest nodules were found in the intermediate and deep strata, while rhodolith sphericity was larger at the shallow depth strata. Higher biomasses of attached macroalgae (epiphytes) were observed at depths where rhodoliths were larger. The abundance of epifauna was variable across regions and depth strata. In general, the occurrence, structure, and abundance of the associated biota across rhodolith habitats were affected by depth, with local variability (i.e., sites within regions) often displaying a more significant influence than the regional (large-scale) variation. Overall, this study showed that the rhodolith morphology and associated epibionts (flora and fauna) were mostly affected by depth, irrespective of latitude.

Seasonal effects of edge and habitat complexity on eelgrass epifaunal assemblages

Habitat degradation and fragmentation reduce habitat structural complexity (e.g. amount of physical features) and increase habitat edges. While many studies have focused on the effects of habitat edges or complexity on biodiversity, relatively few have disentangled them or investigated their effects over time. We investigated how proximity to the edge of eelgrassZosterasubg.Zostera marinaLinnaeus, 1753 habitat, shoot density and their interactions across seasons can influence the diversity pattern of epifaunal assemblages in meadows situated in a Mediterranean lagoon (France). We used a combination of field sampling andin situmanipulations with artificial seagrass units (ASUs) mimicking low and high shoot densities. During autumn and spring, we found that shoot density, Z. marina biomass and leaf area index (LAI) were higher inside the meadows than at the edge, while epiphyte load was the highest in spring at the edges. Epifaunal abundance and diversity were higher at the edge than inside the meadow for both natural shoots—regardless of the epiphyte load—and ASUs in spring. In autumn, epifaunal abundance varied positively with ASU density, regardless of the position in the meadow. Our results also showed that edges and habitat complexity affect the epifaunal structure differently across seasons. Therefore, we suggest that recruitment of macrofauna is the main mechanism explaining a positive edge effect during spring. This work highlights the need to consider seasonal dynamics in the assessment of habitat fragmentation and degradation.

Could the annual Saccorhiza polyschides replace a sympatric perennial kelp (Laminaria ochroleuca) when it comes to supporting the holdfast-associated fauna?

Kelp forests dominate temperate rocky shores worldwide but are declining globally with consequences for organisms that depend on them. In NW Iberia, the golden kelp (Laminaria ochroleuca) commonly occurs alongside a fast-growing annual that, unlike the golden kelp, does not seem to have receded in recent times (Saccorhiza polyschides). Here, we assessed whether the bulbous holdfast of S. polyschides could replace the intricate holdfast of L. ochroleuca as epifaunal habitat provider. Richness, diversity and total abundance of epifauna was similar in both seaweeds, while colonial/encrusting fauna was more abundant in L. ochroleuca. More importantly, each host supported a distinctive assemblage structure, indicating that S. polyschides seems an unsuitable replacement for L. ochroleuca as habitat provider for holdfast epifauna. Therefore, while S. polyschides may contribute substantially to the kelp forest canopy in some seasons, a regional decline of L. ochroleuca will likely alter the patterns of biodiversity within kelp stands.

Meta-analysis of ecosystem services associated with oyster restoration.

Restoration of foundation species promises to reverse environmental degradation and return lost ecosystem services, but a lack of standardized evaluation across projects limits understanding of recovery, especially in marine systems. Oyster reefs are restored to reverse massive global declines and reclaim valuable ecosystem services, but the success of these projects has not been systematically and comprehensively quantified. We synthesized data on ecosystem services associated with oyster restoration from 245 pairs of restored and degraded reefs and 136 pairs of restored and reference reefs across 3500km of U.S. Gulf of Mexico and Atlantic coastlines. On average, restoration was associated with a 21-fold increase in oyster production (mean log response ratio=3.08 [95% confidence interval: 2.58-3.58]), 34-97% enhancement of habitat provisioning (mean community abundance=0.51 [0.41-0.61], mean richness=0.29 [0.19-0.39], and mean biomass=0.69 [0.39-0.99]), 54% more nitrogen removal (mean=0.43 [0.13-0.73]), and 89-95% greater sediment nutrients (mean=0.67 [0.27-1.07]) and organic matter (mean=0.64 [0.44-0.84]) relative to degraded habitats. Moreover, restored reefs matched reference reefs for these ecosystem services. Our results support the continued and expanded use of oyster restoration to enhance ecosystem services of degraded coastal systems and match many functions provided by reference reefs.

Habitat‐complexity regulates the intensity of facilitation along an environmental stress gradient

Positive interactions between foundation species and their associated species are expected to be influenced by the degree of environmental stress as well as trait variations of the species involved. However, there is scarce empirical evidence regarding how these two factors interact and shape the intensity of facilitation. To test how facilitation varies with stress, a colonization experiment using artificial algal units that varied in a functional trait (morphological complexity) was conducted at different intertidal height levels. The isolated effects of shore‐height and host‐complexity are as expected: the number of species and overall abundance of epifauna decreased with lower complexity host units and greater exposure to environmental stress. However, in contrast to the initially proposed model, based on the stress gradient hypothesis, the magnitude of positive interactions increased at lower tidal heights (those levels with, presumably, milder environmental conditions). An additional predation exclusion experiment ruled out the effects of predation pressure as a major factor driving the structure of mobile epifaunal assemblages in these intertidal habitats. Thus, further studies are needed to identify the factors that explain the patterns of facilitation intensity found in the present study.

Spatiotemporal and ecological distribution of megabenthic non-crustacean invertebrates in an ultra-oligotrophic gulf, the eastern Mediterranean Sea

Megabentic non-crustacean invertebrates which play crucial important role in the ecosystem were spatiotemporally studied in an oligotrophic water mass of the eastern Mediterranean shelf-shelf break. The samples were collected with an Otter fishery trawl on three regions, each having five different seafloor depths. The samplings were repeated seasonally in four different months during year 2014–2015, being aimed to provide baseline ecological information on their bathymetric and seasonal distribution and biodiversity patterns. A total of 7 megabenthic non-crustacean phyla were found including 90 species composed mainly of 38 mollusks, 20 echinoderms, and 12 sponges. Three non-crustacean species recorded alien species for the Mediterranean Sea. Number of species for each phylum changed with the seafloor depth. Number of species increased overall from the shallow water to the intermediate water, and then decreased down to the shelf break. The westernmost Mediterranean Sea was incomparable so rich and high in the number of species, biomass and abundance as compared with the easternmost Mediterranean Sea. In general, abundance and biomass increased in summer and decreased in winter in the Mediterranean Sea, particularly at the shallower waters, continental shelf depending mainly on a series variety of organisms' behaviors and environmental conditions. The abundance of epifauna was differentiated by the status of the grounds: fishing and non-fishing grounds. Conomurex persicus changed remarkably the spatiotemporal trends in contrast to no regular seasonal pattern in the faunistic characters in very shallow waters after its introduction. The depth-related gradient was owing to a number of biogeochemical and physical factors interacted with sedimentary characters, light intensity, nutritional condition availability, and temperature. With an exception of few species, the characteristic species for spatio-temporal similarities, the species composition were rather different between the easternmost and westernmost Mediterranean Sea.

The invasive seaweed Asparagopsis taxiformis erodes the habitat structure and biodiversity of native algal forests in the Mediterranean Sea

Invasive seaweeds are listed among the most relevant threats to marine ecosystems worldwide. Biodiversity hotspots, such as the Mediterranean Sea, are facing multiple invasions and are expected to be severely affected by the introduction of new non-native seaweeds in the near future. In this study, we evaluated the consequences of the shift from the native Ericaria brachycarpa to the invasive Asparagopsis taxiformis habitat on the shallow rocky shores of Favignana Island (Egadi Islands, MPA, Sicily, Italy). We compared algal biomass and species composition and structure of the associated epifaunal assemblages in homogenous and mixed stands of E. brachycarpa and A. taxiformis. The results showed that the biomass of primary producers is reduced by 90% in the A. taxiformis invaded habitat compared to the E. brachycarpa native habitat. The structure of the epifaunal assemblages displayed significant variations among homogenous and mixed stands. The abundance, species richness and Shannon-Wiener diversity index of the epifaunal assemblages decreased by 89%, 78% and 40%, respectively, from homogenous stands of the native E. brachycarpa to the invasive A. taxiformis. Seaweed biomass was the structural attribute better explaining the variation in epifaunal abundance, species richness and diversity. Overall, our results suggest that the shift from E. brachycarpa to A. taxiformis habitat would drastically erode the biomass of primary producers and the associated biodiversity. We hypothesize that a complete shift from native to invasive seaweeds could ultimately lead to bottom-up effects on rocky shore habitats, with negative consequences for the ecosystem structure, functioning, and the services provided.

Indirect effects shape macroalgal epifaunal communities.

We tested the response of algal epifauna to the direct effects of predation and the indirect consequences of habitat change due to grazing and nutrient supply through upwelling using an abundant intertidal rhodophyte, Gelidium pristoides. We ran a mid‐shore field experiment at four sites (two upwelling sites interspersed with two non‐upwelling sites) along 450 km of the south coast of South Africa. The experiment was started in June 2014 and ran until June 2015. Four treatments (predator exclusion, grazer exclusion, control, and procedural control) set out in a block design (n = 5) were monitored monthly for algal cover for the first 6 months and every 2 months for the last 6 months. Epifaunal abundance, species composition, algal cover, and algal architectural complexity (measured using fractal geometry) were assessed after 12 months. Predation had no significant effect on epifaunal abundances, while upwelling interacted with treatment. Grazing reduced the architectural complexity of algae, with increased fractal dimensions in the absence of grazers, and also reduced algal cover at all sites, though the latter effect was only significant for upwelling sites. Epifaunal community composition was not significantly affected by the presence of herbivores or predators but differed among sites independently of upwelling; sites were more similar to nearby sites than those farther away. In contrast, total epifaunal abundance was significantly affected by grazing, when normalized to algal cover. Grazing reduced the cover of algae; thus, epifaunal abundances were not affected by the direct top‐down effects of predation but did respond to the indirect effects of grazing on habitat availability and quality. Our results indicate that epifaunal communities can be strongly influenced by the indirect consequences of biotic interactions.

Pertumbuhan Api-Api (Avicennia alba) dan Kelimpahan Epifauna Bentik di Kawasan Rehabilitasi Mangrove Desa Kedaburapat Kabupaten Kepulauan Meranti

The research was conducted in July - October 2020. Collection of data A. alba growth and abundance of benthic epifauna was carried out in the mangrove rehabilitated area of Kedabupat village, Kepulauan Meranti Regency. The aims of this study was to analyze the growth (stems height and diameter) of the mangrove A. alba species as a result of rehabilitation and abundance of benthic epifauna in the area. The method used in this research was a survey method, where data was obtained by directly to the research location. The data collected was data on the height and diameter of A. alba stems, density of macro epifauna species, and water quality in the field, then followed by analysis of water and sediment samples in the laboratory. The results showed that the average increace in height of the stem by zone was 6.45-12.93 cm/month, meanwhile the average value of the increase in stem diameter by zone is 1.53-1.85 mm/month. There were 13 epifauna benthic species from 2 classes namely Gastropod and Malacostraca from mangrove rehabilitation. Gastropod class that was Littoraria melanostoma, Nerita balteata and Sphaerassiminea miniata; from the malacostraca class that was Uca coarctata, Metopograpsus latifrons, Ceonobita cavipes, and Clibanarius longitarsus. Benthic epifauna abundance values average ranged from 31.33-52.22 ind/m2.

Comparing the Performance of a Remotely Operated Vehicle, a Drop Camera, and a Trawl in Capturing Deep-Sea Epifaunal Abundance and Diversity

Deep-sea ecosystems provide services such as food, minerals, and nutrient recycling, yet baseline data on their structure is often lacking. Our limited knowledge of vulnerable deep-sea ecosystems presents a challenge for effective monitoring and mitigation of increasing anthropogenic threats, including destructive fishing and climate change. Using data from two stations differing in total epifaunal abundance and taxonomic composition, we compared the use of imagery collected by two non-invasive tools [remotely operated vehicle (ROV) and drop camera] and data collected with a trawl system, commonly used to quantify epibenthic megafauna in the deep sea. Imagery and trawl data captured different epifaunal patterns, the former being more efficient for capturing epifauna, particularly Pennatulacean recruits. The image-based methods also caused less disturbance, had higher position accuracy, and allow for analyses of spatial structure and species associations; fine-scale distributions could not be elucidated with a trawl. Abundance was greater for some taxa, and diversity accumulated faster with increasing sample size for the drop camera than the ROV at one station. However, there are trade-offs between these tools, including continuous and discrete sampling for the ROV and drop camera, respectively, which can affect follow-up analyses. Our results can be used to inform monitoring frameworks on the use of appropriate sampling tools. We recommend further research into tool sampling biases and biometric relationships to help integrate datasets collected with different tools.

Fine-scale responses of mobile invertebrates and mesopredatory fish to habitat configuration

As habitat-forming species continue to decline globally, it is important to understand how associated communities respond to habitat loss and fragmentation. Changes in the density and spatial configuration of habitat have important consequences for associated communities. However, tests of these factors are often confounded by morphological variation of habitat-formers, which can be resolved by using standardised habitat-mimics. Furthermore, few studies have incorporated the role of predators in mediating the observed effects. To test whether predators mediate the abundance of invertebrates among algal habitats of varying configuration (isolated vs patches, and positions within patches), we placed macroalgal mimics into subtidal estuarine habitats for one month to sample epifaunal communities. At the same time, we conducted underwater video surveys of fish communities to quantify fish communities and their feeding behaviour among the artificial habitats. Isolated habitats did not differ from patch habitats, however, patch edges had the highest epifaunal abundance, where fish were least commonly observed. Observed fish feeding was highest in the middle of patches and increased fish observations and feeding in habitats with reduced epifaunal communities suggest that mesopredatory fish are mediating epifauna in patches, with predation pressure altered by the spatial configuration of the habitat. This contrasts to previous studies that focus on predators that congregate outside patches and suggest that fragmentation leads to reduced invertebrate abundance at habitat edges in contrast to centres. However, this study highlights that in habitat patches housing small mesopredators that also benefit from the increased structure, the centre of the patch experiences higher predation and therefore fewer epifauna in contrast to patch edges and individual algal mimics.

Habitat Primarily Structures Seagrass Epifaunal Communities: a Regional-Scale Assessment in the Chesapeake Bay

Epifaunal invertebrates play an important role in seagrass systems, both by grazing epiphytic algae from seagrass blades and by acting as a major food source for higher trophic levels. However, while many studies have described epifaunal community properties at small spatial scales (1–10 m2) and across very large gradients (from continental coastlines to the entire globe), few have examined regional-scale (100–1000 km2) patterns or, more importantly, disentangled the drivers of these patterns. Here, we synoptically sampled the epifaunal invertebrates of 16 sites dominated by eelgrass (Zostera marina) across the lower Chesapeake Bay estuary to describe differences in epifaunal community abundance, biomass, richness, and composition. We then used complementary spatial and environmental data to identify potential drivers of these patterns. We found no significant associations between any variable and epifaunal abundance or biomass, but differences in epifaunal species richness correlated most strongly with water temperature, and differences in community composition were best explained by seagrass cover and the biomass of algal resources. Further exploration revealed the relationship between cover and community structure was driven by three specific species of peracarid crustaceans. Furthermore, when only species with direct development were included in the analysis, geographic distance, rather than seagrass cover, became a significant predictor of community composition, suggesting that species with particular traits (i.e., direct developers) are more likely to be found closer together in space.

Sargassum epifaunal communities vary with canopy size, predator biomass and seascape setting within a fringing coral reef ecosystem

Tropical seascapes are comprised of a range of patch habitat types, yet we have only a partial understanding of how local patch condition and seascape position may influence patterns of marine biodiversity, particularly for invertebrate taxa. We investigated how the epifaunal abundance and biomass of tropical Sargassum varied with canopy size (volume, total length and dry weight), local patch conditions (macroalgal composition, canopy structure and invertivorous fish biomass) and seascape setting (nearshore, lagoon and back reef) within the Ningaloo fringing reef ecosystem, Australia. A total of 49431 epifauna, dominated by crustaceans and molluscs, were extracted from the thalli of 81 tropical Sargassum polycystum individuals. Epifaunal abundance and biomass were most strongly correlated with host Sargassum canopy volume and dry weight, respectively. Epifaunal abundance and biomass also varied significantly among separate Sargassum meadow patches, with a significant interaction between canopy size and seascape position. Considerable site-level variations in epifaunal biomass density (mg per g Sargassum dry weight) were best predicted by either seascape context or local invertivorous fish biomass. Sargassum within meadows furthest from the back reef tended to have the highest epifaunal biomass (dominated by molluscs), while meadows closest to the back reef were dominated by crustacea. Sargassum within meadows with a high local abundance of invertivorous labrids and serranids tended to have the lowest epifaunal biomass. Strong Sargassum canopy size-epifauna relationships indicate that even small differences in canopy extent have major flow-on effects for the trophic function of tropical marine ecosystems by affecting the epifaunal secondary productivity available to higher-order consumers, such as fishes.

Facilitation cascades create a predation refuge for biodiversity in a novel connected habitat

AbstractCommunities structured via facilitation cascades whereby one habitat‐forming species promotes a secondary habitat‐forming species with synergistic effects on biodiversity are increasingly documented. Habitat‐formers can also extend the realized niche of other habitat‐forming species by facilitating their recruitment into novel environments across heterogeneous landscapes. However, further understanding of whether secondary habitat‐formers in these novel environments differ in their structure or support different communities from those settled in their natal habitat is required. Here, we investigated whether abiotic and biotic conditions in a novel connected habitat influence biodiversity within a secondary habitat‐former facilitated outside its natal habitat. We contrasted the morphology of the habitat‐forming alga, Sirophysalis trinodis, and its associated fish and epifaunal community occurring on rocky reef (natal habitat) and on nearby a biogenic hard substrate, live clam shells (novel habitat) in soft sediments. The algae on clams had a different morphology to those on the rocky shore and supported increased abundance of some epifaunal species. A reciprocal transplant experiment of S. trinodis individuals among habitats found that differences in the abundance of epifauna were explained by the increased abundance and consumption rates of predatory fish on the reef habitat compared to soft‐sediment habitats, and not by differences in algal morphology between habitats. We demonstrate that facilitation promotes a secondary habitat‐former into a novel habitat, which then enhances the abundance of associated epifauna by providing a predation refuge. This study contributes to a small but growing body of research demonstrating landscape‐scale effects of facilitation cascades, and that basal habitat‐formers can extend the realized niche of secondary habitat‐formers and their associated communities.

Habitat variability in an underwater forest: Using a trait‐based approach to predict associated communities

Abstract By providing food, living space and reducing biotic and abiotic stress, habitat‐formers support diverse communities. The characteristics that mediate their value to associated organisms, however, are not always clear. Traditional assessments of habitat‐former and associated community relationships use broad‐scale classifications to group habitat‐formers according to identity or gross morphology. Trait‐based approaches instead measure traits at the level of the individual and in doing so allow for predictions that are not constrained to taxonomic groups. By measuring at the level of the individual, trait‐based approaches have the potential to capture not only interspecific variability, but also the intraspecific variation that is often ignored by traditional approaches. Trait‐based approaches may therefore provide a novel way to link the characteristics of habitat‐formers to ecosystem functioning. Here we quantified inter‐ and intraspecific variation in six macroalgal species and tested the relative importance of morphological traits and species identity in predicting the abundance of associated fauna. All species of macroalgae displayed substantial intraspecific morphological variation. Morphological traits were more important than species identity in predicting epifaunal abundances. Total surface area was the most important trait when predicting total abundance per thallus, whilst mean frond length was the most important predictor for abundance per gram algal biomass. This suggests that traits that describe the quantity of available habitat were the most important predictors of community abundance, but the shape or architecture of the habitat also contributes to structuring these communities. Our results indicate that trait‐based approaches may be more useful than traditional species‐based approaches when predicting the abundances of fauna associated with habitat‐forming species. A free Plain Language Summary can be found within the Supporting Information of this article.

Effects of macroalgal morphology on marine epifaunal diversity

AbstractMacroalgae play important ecological roles, including as hosts for a wide range of epifauna. However, the diversity relationships between macroalgae and epifauna are poorly understood for most tropical host species and algal morphologies. This study aims to characterize and analyse the diversity of invertebrates present amongst macroalgae with three distinct morphologies (three-dimensional, filamentous and foliose) across different tropical intertidal sites in Singapore. Morphological and DNA barcoding tools were employed for epifaunal species identification, and ordination statistics and multiple linear regression were used to test the effects of algal morphology, species and site on community structure and diversity of epiphytic invertebrates. Overall, epifaunal communities were distinct among sites and algal morphologies, and diversity was affected significantly by algal morphology. In particular, filamentous macroalgae hosted the highest abundance of epifauna dominated mainly by amphipods, which were able to take advantage of the high surface area to volume ratio in filamentous algal mats as a consequence of their thinner forms. Foliose species showed a significantly negative effect on invertebrate diversity. Our findings highlight the diverse associations between intertidal macroalgae and invertebrates with high turnover between algal morphology and sites that contribute to the high biodiversity of tropical shores. Future studies should consider the effects of the host habitat, seasonality and more algal species on epifaunal diversity.