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Foundation species define the ecosystems they live in, but ecologists have often characterized dominant plants as foundational without supporting evidence. Giant kelp has long been considered a marine foundation species due to its complex structure and high productivity; however, there is little quantitative evidence to evaluate this. Here, we apply structural equation modelling to a 15-year time series of reef community data to evaluate how giant kelp affects the reef community. Although species richness was positively associated with giant kelp biomass, most direct paths did not involve giant kelp. Instead, the foundational qualities of giant kelp were driven mostly by indirect effects attributed to its dominant physical structure and associated engineering influence on the ecosystem, rather than by its use as food by invertebrates and fishes. Giant kelp structure has indirect effects because it shades out understorey algae that compete with sessile invertebrates. When released from competition, sessile species in turn increase the diversity of mobile predators. Sea urchin grazing effects could have been misinterpreted as kelp effects, because sea urchins can overgraze giant kelp, understorey algae and sessile invertebrates alike. Our results confirm the high diversity and biomass associated with kelp forests, but highlight how species interactions and habitat attributes can be misconstrued as direct consequences of a foundation species like giant kelp.

Aim The two additive components of β‐diversity, namely turnover and nestedness, reflect the two basic mechanisms underlying the overall change in species identities across the landscape, the replacement of species or their loss, respectively. Analogously, functional turnover and nestedness express the replacement or loss of functional traits associated with variations in community composition. However, the extent to which patterns of compositional and functional nestedness and turnover may overlap, or diverge, is still uncertain in marine environments. Here, patterns of turnover and nestedness were quantified in marine benthic assemblages in order to assess their relative contribution to spatial patterns of compositional and functional ‐diversity. Location Mediterranean Sea, NE Ionian Sea, Ionian Archipelago. Methods In this study, we investigated patterns of dissimilarity in species and functional trait composition in subtidal macrobenthic assemblages from Mediterranean islands in order to quantify compositional and functional β‐diversity among islands, determine the relative contributions of turnover and nestedness, and compare β‐diversity patterns occurring in shallow and deeper reefs. Results We found a complex relationship between functional and compositional β‐diversity at varying depth. At 5 m, species and functional trait dissimilarity largely overlapped, with turnover being the dominant component in both cases. At 15 m, compositional β‐diversity was mostly due to turnover, with a negligible contribution of nestedness, whereas the opposite occurred for functional β‐diversity. Partitioning β‐diversity components revealed this discrepancy and the presence of functional hotspots, which would remain unnoticed analysing the overall compositional and functional β‐diversity. Main conclusions Our findings may have profound implications for the optimization of conservation planning, stressing the need for assessing habitat‐dependent idiosyncrasies in components of functional and compositional β‐diversity for a more comprehensive picture of possible protection scenarios that, besides structure, may also allow preserving the functioning of marine communities.

Coastal ecosystems provide numerous services, such as nutrient cycling, climate change amelioration, and habitat provision for commercially valuable organisms. Ecosystem functions and processes are modified by human activities locally and globally, with degradation of coastal ecosystems by development and climate change occurring at unprecedented rates. The demand for coastal defense strategies against storms and sea‐level rise has increased with human population growth and development along coastlines worldwide, even while that population growth has reduced natural buffering of shorelines. Shoreline hardening, a common coastal defense strategy that includes the use of seawalls and bulkheads (vertical walls constructed of concrete, wood, vinyl, or steel), is resulting in a “coastal squeeze” on estuarine habitats. In contrast to hardening, living shorelines, which range from vegetation plantings to a combination of hard structures and plantings, can be deployed to restore or enhance multiple ecosystem services normally delivered by naturally vegetated shores. Although hundreds of living shoreline projects have been implemented in the United States alone, few studies have evaluated their effectiveness in sustaining or enhancing ecosystem services relative to naturally vegetated shorelines and hardened shorelines. We quantified the effectiveness of (1) sills with landward marsh (a type of living shoreline that combines marsh plantings with an offshore low‐profile breakwater), (2) natural salt marsh shorelines (control marshes), and (3) unvegetated bulkheaded shores in providing habitat for fish and crustaceans (nekton). Sills supported higher abundances and species diversity of fishes than unvegetated habitat adjacent to bulkheads, and even control marshes. Sills also supported higher cover of filter‐feeding bivalves (a food resource and refuge habitat for nekton) than bulkheads or control marshes. These ecosystem‐service enhancements were detected on shores with sills three or more years after construction, but not before. Sills provide added structure and may provide better refuges from predation and greater opportunity to use available food resources for nekton than unvegetated bulkheaded shores or control marshes. Our study shows that unlike shoreline hardening, living shorelines can enhance some ecosystem services provided by marshes, such as provision of nursery habitat.

Kelp forests along temperate and polar coastlines represent some of most diverse and productive habitats on the Earth. Here, we synthesize information from >60 years of research on the structure and functioning of kelp forest habitats in European waters, with particular emphasis on the coasts of UK and Ireland, which represents an important biogeographic transition zone that is subjected to multiple threats and stressors. We collated existing data on kelp distribution and abundance and reanalyzed these data to describe the structure of kelp forests along a spatial gradient spanning more than 10° of latitude. We then examined ecological goods and services provided by kelp forests, including elevated secondary production, nutrient cycling, energy capture and flow, coastal defense, direct applications, and biodiversity repositories, before discussing current and future threats posed to kelp forests and identifying key knowledge gaps. Recent evidence unequivocally demonstrates that the structure of kelp forests in the NE Atlantic is changing in response to climate‐ and non‐climate‐related stressors, which will have major implications for the structure and functioning of coastal ecosystems. However, kelp‐dominated habitats along much of the NE Atlantic coastline have been chronically understudied over recent decades in comparison with other regions such as Australasia and North America. The paucity of field‐based research currently impedes our ability to conserve and manage these important ecosystems. Targeted observational and experimental research conducted over large spatial and temporal scales is urgently needed to address these knowledge gaps. The kelp dominated ecosystems of the northeast Atlantic are unique and provide a wealth of goods and services to regional and centralized human populations. However, compared to other regions, such as North America and Australasia, NE Atlantic kelp ecosystems have been understudied in recent decades, resulting in extensive knowledge gaps and insufficient understanding of ecological responses to rapid environmental change.

Fil: Dionisi, Hebe Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina

Different types of benthic habitats likely produce distinct soundscapes due to differences in the physical and biological contributors to ambient sound. Despite their potential importance to ecological processes such as larval settlement, the soundscapes of most coastal and estuarine habitats have not been characterized. We investigated whether an estuarine soundscape is a reliable indicator of habitat type by measuring the sounds of oyster reefs and nearby off-reef soft-bottom areas in Pamlico Sound, North Carolina, USA. Acoustic sampling in 3 areas across the estuary revealed distinct acoustic patterns in oyster reef habitats compared to surrounding off-reef areas, with reef soundscapes dominated by snapping shrimp sounds and the vocalizations of reef-dwelling fish species. Compared to soft-bottom habitat, oyster reefs had significantly higher sound pressure levels in the 2–23 kHz frequency band and higher acoustic diversity index values at each concurrent sampling event. Spectral differences between adjacent reef/off-reef habitats were present throughout the summer and fall sampling season and across 2 sampling years, but the acoustic signal strength differed between reef sites. Passive sound propagation surveys found that the distinct acoustic characteristics of oyster reefs within the 2–23 kHz frequency band were highly localized, with effective source levels of 108.8 to 120.0 dB re 1 μPa @ 1 m and transmission loss approximating a cylindrical geometric spreading model. This soundscape characterization study suggests that spatial heterogeneity in ambient sound could serve as a reliable indicator of habitat type and potentially convey habitat quality information to dispersing organisms.

Two new species of the genus Dorylaimopsis Ditlevsen, 1918 from the subtidal zone of the Yellow Sea are described and illustrated. Dorylaimopsis sinica sp. nov . is characterised by the lateral differentiation in the form of longitudinal rows of larger dots which consisting of three rows of dots in about the anterior 20% and posterior 20% of the total body length and two rows of dots in the rest portion of the body, by the multispiral amphidial fovea having three turns; slender, equal, arcuated spicules; cephalated proximal end with a short median cuticularised lamina; length 1.9–2.2 times the cloacal body diameter; gubernaculum with two geniculate curved apophyses and 14–17 papilliform precloacal supplements; and excretory pore posterior to nerve ring. Dorylaimopsis zhangi sp. nov . is characterised by having cephalic setae 6–7 μm long, amphidial fovea with three turns, lateral differentiation consisting of four longitudinal rows of larger dots in the pharyngeal and tail regions, three longitudinal rows of larger dots in the middle region of body, spicules slender and slightly curved, length 2.0–2.5 times the cloacal body diameter, and 18 small, pit-like precloacal supplements. An updated dichotomous key is provided for the 29 valid species of Dorylaimopsis .

Environmental stress impedes predation and herbivory by limiting the ability of animals to search for and consume prey. We tested the contingency of this relationship on consumer traits and specifically hypothesized that herbivore mobility relative to the return time of limiting environmental stress would predict consumer effects. We examined how wave-induced water motion affects marine communities via herbivory by highly mobile (fish) vs. slow-moving (pencil urchin) consumers at two wave-sheltered and two wave-exposed rocky subtidal locations in the Galapagos Islands. The exposed locations experienced 99th percentile flow speeds that were 2–5 times greater than sheltered locations, with mean flow speeds >33 cm/s vs. <16 cm/s, 2–7 times higher standing macroalgal cover and 2–3 times lower cover of crustose coralline algae than the sheltered locations. As predicted by the environmental stress hypothesis (ESH), there was a negative relationship between mean flow speed and urchin abundance and herbivory rates on Ulva spp. algal feeding assays. In contrast, the biomass of surgeonfishes (Acanthuridae) and parrotfishes (Labridae: Scarinae) was positively correlated with mean flow speed. Ulva assays were consumed at equal rates by fish at exposed and sheltered locations, indicating continued herbivory even when flow speeds surpassed maximum reported swimming speeds at a rate of 1–2 times per minute. Modeled variation in fish species richness revealed minimal effects of diversity on herbivory rates at flow speeds <40 cm/s, when all species were capable of foraging, and above 120 cm/s, when no species could forage, while increasing diversity maximized herbivory rates at flow speeds of 40–120 cm/s. Two-month herbivore exclusion experiments during warm and cool seasons revealed that macroalgal biomass was positively correlated with flow speed. Fish limited macroalgal development by 65–91% at one exposed location but not the second and by 70% at the two sheltered locations. In contrast, pencil urchins did not affect algal communities at either exposed location, but reduced macroalgae by 87% relative to controls at both sheltered locations. We propose an extension of the ESH that is contingent upon mobility to explain species-specific changes in feeding rates and consumer effects on benthic communities across environmental gradients.

Investigating subtidal friction and mass transport is pivotal for examining subtidal dynamics in tidal rivers. Although the behavior of subtidal friction and transport has been discussed in recent years, most studies have been conducted on tidal rivers that are affected by high amounts of river runoff. The aim of this study is to offer an initial understanding of the spatial and temporal behaviors of subtidal friction and subtidal flux in a tidal river channel with limited river runoff. This study utilized the frequency domain and theoretical decomposition analyses to determine the dominant tidal and subtidal mechanisms. Frequency domain analysis indicated the dominance of semidiurnal and diurnal tides in the observed tidal river channel. The rate of energy transfer owing to shallow water interaction was found to be stronger for the current velocity than for the water elevation. Decomposition analysis showed that subtidal friction and flux in a low-discharge tidal river channel were largely influenced by subtidal flow-induced subtidal friction and Eulerian return flux, respectively. The key findings of this study are as follows: (i) the limited amount of river runoff (4–20 m3/s) leads to the vertical variability of subtidal friction contributions from subtidal flow and subtidal-tidal interaction, as well as Eulerian return flux, and (ii) the vertical variability of the aforementioned terms can be associated with the existence of influential longitudinal subtidal density gradients along the tidal river. We believe that these findings advance our understanding of subtidal dynamics in tidal river systems, particularly those with limited discharge.