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Biodiversity is crucial for supporting ecosystem functioning, yet some species play a disproportionate role in maintaining complex ecological processes. Ecosystem engineers are species that directly influence ecosystems by modifying biophysical environments, creating novel habitats, altering biogeochemical cycles, increasing biodiversity and/or modulating ecological processes. Although these species may substantially influence ecosystem functioning, their role is often overlooked and difficult to quantify. Understanding the status, dynamics and trends of ecosystem engineers is essential for mitigating biodiversity loss and maintaining healthy ecosystems.This review reveals the common but underappreciated roles that ecosystem engineers play in ecosystem functioning across many different taxa, biomes and ecological processes. We first synthesise how knowledge of ecosystem engineering improves our understanding of species interactions and the ecological processes underlying both ecosystem functioning and BEF relationships. We provide a conceptual model for addressing the effects of ecosystem engineers in BEF research and ecological dynamics.We provide a 'how to' analytical framework for monitoring and quantifying changes in ecosystem engineers and their effects on ecosystem functioning. This framework includes (i) what variables to measure, how and at which scale; (ii) experiments involving species exclusion or removal, introduction and comparative designs when experimental manipulation is not feasible and (iii) statistical, data‐driven and theory‐driven models.We discuss how to leverage ecosystem engineering in the context of current global change and ecosystem restoration efforts. Including ecosystem engineers in conservation and restoration programs, when implemented in the appropriate context and supported by an understanding of ecological mechanisms and processes, may be crucial for sustaining biological diversity and functional ecosystems. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Ecosystem engineers (EEs) strongly influence ecosystems by affecting the abiotic properties of a system to which many biota respond. EEs can, thus, be pivotal species in restoration by helping to move systems toward desired states much faster and more efficiently than direct human intervention on the abiotic state.For EEs to play a central, purposeful role in restoration, it is important to identify guiding principles about how the EEs may best be selected and incorporated.I discuss three important aspects to determine (a) where the utility for EEs is high; (b) where EEs can most easily establish, are easy to handle and scaling‐up their use is possible; and (c) how to recognize and value multiple, coupled and trait‐dependent engineering functions of EEs.Understanding these aspects of EEs should help guide purposeful and efficient choices in our approach to restoration. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Heatwaves have increased in frequency, duration, and magnitude in recent decades, causing mass mortality events in terrestrial and aquatic ecosystems. Arguably, mass mortalities of habitat-forming organisms -- i.e., dominant sessile organisms that define habitats via their own physical structure -- would be amongst the most dramatic impact of heat waves because of their negative, cascading consequences on their associated biodiversity. However, the resistance of habitat-forming organisms to heat waves can be enhanced if they associate with secondary habitat formers able to tolerate and modulate extreme heat levels. Here we show that a seaweed of the Porphyra/Pyropia (P/P) clade can shield primary habitat-forming mussels, Brachidontes rodriguezii, from the impacts of extreme temperatures in a southwestern Atlantic rocky intertidal shore. By means of P/P removal experiments and surveys, we illustrate that P/P cover (a) buffers temperatures in the understory mussel beds during daytime air exposure periods in the summer, (b) reduces mussel mortality and leads to increased mussel body condition during warm summer periods, and (c) can prevent mass mortality of mussels during the course of a heat wave. Additionally, by means of a mussel removal experiment we illustrate that mussel cover is critical for P/P establishment, which is in consonance with the remarkably higher P/P densities and cover observed in mussel beds relative to exposed rock surfaces across a ~70 km coastal range. Collectively, these findings reveal a facultative mutualism where mussels provide a favorable substrate for P/P colonization and P/P attenuates heat mediated mortality on mussels. The ability of P/P to enhance the resistance of mussel beds to extreme heat events and the occurrence of similar P/P-mussel associations during spring-summer at globally dispersed sites suggests a widespread importance of P/P for the stability of mussel beds and their associated communities under warming climates. [ABSTRACT FROM AUTHOR]

Heat waves have increased in frequency, duration, and magnitude in recent decades, causing mass mortality events in terrestrial and aquatic ecosystems. Arguably, mass mortalities of habitat-forming organisms – i.e., dominant sessile organisms that define habitats via their own physical structure – would be amongst the most dramatic impact of heat waves because of their negative, cascading consequences on their associated biodiversity. However, the resistance of habitat-forming organisms to heat waves can be enhanced if they associate with secondary habitat formers able to tolerate and modulate extreme heat levels. Here we show that a seaweed of the Porphyra/Pyropia (P/P) clade can shield primary habitat-forming mussels, Brachidontes rodriguezii, from the impacts of extreme temperatures in a southwestern Atlantic rocky intertidal shore. By means of P/P removal experiments and surveys, we illustrate that P/P cover (a) buffers temperatures in the understory mussel beds during daytime air exposure periods in the summer, (b) reduces mussel mortality and leads to increased mussel body condition during warm summer periods, and (c) can prevent mass mortality of mussels during the course of a heat wave. Additionally, by means of a mussel removal experiment we illustrate that mussel cover is critical for P/P establishment, which is in consonance with the remarkably higher P/P densities and cover observed in mussel beds relative to exposed rock surfaces across a ~70 km coastal range. Collectively, these findings reveal a facultative mutualism where mussels provide a favorable substrate for P/P colonization and P/P attenuates heat mediated mortality on mussels. The ability of P/P to enhance the resistance of mussel beds to extreme heat events and the occurrence of similar P/P-mussel associations during spring-summer at globally dispersed sites suggests a widespread importance of P/P for the stability of mussel beds and their associated communities under warming climates.

Microorganisms interact with all biological components in a variety of ways. They contribute to increase the efficiency of marine food webs and facilitate the adaptation of multicellular organisms to climate change and other human-induced impacts. Increasing evidence suggests that microbiomes are essential for the health of marine species, for maintaining productive marine ecosystems, and thus for the sustainable functioning of the global biosphere. Marine microbiomes are typically species- or habitat-specific and are susceptible to environmental and human-driven changes. The microbiota of seagrasses, macroalgae, mangroves or tropical corals benefits their hosts by increasing their fitness, contributing to the removal of toxic compounds, conferring protection against pathogens, and/or supporting nutrient requirements. Alterations of the microbiomes might have negative consequences on species’ health, survival, and overall ecosystem functioning. Despite the key ecological role of microbiomes in all ecosystems, their potential for the restoration of degraded habitats is still largely unexplored. Here we present a literature survey of the existing information on the microbiota associated with habitat-forming species and suggest that the resilience/recovery of damaged marine habitats can depend largely on the changes in the microbiota. Nature-based solutions relying on microbiome analyses (also through omics approaches) enable health monitoring of transplanted organisms/metacommunities and potential identification/production of probiotics/bio-promoters to stabilize unhealthy conditions of transplants. In the context of international strategies concerning ecological restoration, the use of the scientific knowledge acquired on the marine microbiome deserves to be exploited to assist both traditional and innovative restoration approaches. The success of habitat restoration may depend on our ability to maintain, along with the restored species and habitats, a functional microbiota.

The Mediterranean Sea is one of the main hotspots for the introduction of nonindigenous species in the world. The invasive alga Rugulopteryx okamurae was detected in 2015 along the coasts of the Strait of Gibraltar, the Atlantic entrance to the Mediterranean Sea. This brown seaweed of Asian origin, with an enormous expansion capacity and high survival rate, has spread rapidly across the Alboran Sea (western Mediterranean). Nevertheless, this species continues to show its highest abundance in areas close to the Strait of Gibraltar. We recorded R. okamurae in Punta de la Mona (Granada, northern coast of the Alboran Sea), one of the zones with the highest marine biodiversity in the Alboran Sea. This record is the easternmost point within the Spanish coasts where abundance data for this invasive species are available. Rugulopteryx okamurae demonstrated its highest abundance values at 48 m, an unusual record for this species in the Mediterranean Sea. We found R. okamurae growing on rocky bottoms, multiple coralligenous organisms, artificial substrates and epiphyting the coral Dendrophyllia ramea (an important habitat-forming species). Cold-water corals provide substrate, shelter and habitat for other species and play a critical role in deep water ecosystems. It is crucial to study and quantify the possible effects of invasive species on habitat-forming species, especially in the Mediterranean Sea, where the arrival of exotic organisms is striking; a better understanding of their dispersal capacities is urgently needed, as they can affect key organisms. The results obtained in this study validate the prolific capacity of R. okamurae to colonize new areas, affecting both littoral and deeper coastal areas. This behaviour, coupled with the ability to grow on a wide variety of suitable substrates, creates a strong threat to natural environments. [ABSTRACT FROM AUTHOR]

Trammel nets are one of the least selective fishing gears and are known to catch a variety of species, many of which are discarded, including important invertebrates that are considered habitat-forming species. Although there are few studies focusing on this type of by-catch, these habitat-forming species include corals and sponges that are vulnerable to disturbances from fishing activities using bottom contact gear. Experimental fishing was conducted off the port of Portimão (southern Portugal) from November 2021 to April 2022 using standard and modified trammel nets rigged to be lifted off the bottom with the objective of reducing invertebrate by-catch and impacts on the bottom habitat. The modified lifted net caught 36% less by-catch of invertebrates in numbers than the standard net, with no significant decrease of biomass and value of target species. The results obtained with the two net types are discussed, as well as the necessity for good video recording equipment that can improve sampling accuracy, and the usefulness of interviewing the fishers on net performance after experimental fishing was conducted. [ABSTRACT FROM AUTHOR]

Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change. [ABSTRACT FROM AUTHOR]

The green macroalga Caulerpa filiformis has been spreading on shallow soft sediment habitats along the Peruvian coast, colonizing previously unvegetated sediments to create monospecific meadows. We examined the nature of the impact of C. filiformis meadows on the density, taxonomic richness and assemblage structure of epifaunal and infaunal benthic macroinvertebrates. Specifically, we tested whether the spread of C. filiformis has resulted in different macroinvertebrate assemblages than those formed by the dominant native macroalgae (i.e., Rhodymenia spp.) and unvegetated sediments. Surveys were undertaken in two bays in each of two locations, in central and southern Peru, during winter 2017 and summer 2018. In general, our results show that macroinvertebrate assemblages were similar across all three habitats, although there were some differences, related to location and time, but with no clear patterns observed. Taxonomic richness and density was generally higher in the vegetated habitats than the unvegetated habitat, and where there were differences between the two vegetated habitats there was no consistent pattern of which habitat supported the highest richness or density. Given invading C. filiformis is primarily colonizing unvegetated habitats it would appear that this species is creating a new niche which supports similar assemblages, but higher taxonomic richness and density than unvegetated habitats. While our study suggests that C. filiformis is having a limited ecological impact we recommend that actions be put in place to limit the spread of this invasive species at the same time as increasing monitoring of the ecological impacts of this species as lags in the ecological impacts of invasive species are common. [ABSTRACT FROM AUTHOR]

The introduction and successful expansion of tropical species into temperate systems is being exacerbated by climate change, and it is particularly important to identify the impacts that those species may have, especially when habitat-forming species are involved. Seagrass meadows are key shallow coastal habitats that provide critical ecosystem services worldwide, and they are threatened by the arrival of non-native macroalgae. Here, we examined the effects of Halimeda incrassata, a tropical alga that has recently colonized the Mediterranean Sea, on epifaunal assemblages associated with Cymodocea nodosa seagrass meadows of Mallorca Island (Western Mediterranean Sea). This invasive macroalga is an ecological engineer and thus has a high potential of modifying native habitats. A seagrass meadow colonized by H. incrassata exhibited important changes on associated epifaunal assemblages, with an increase in abundance and diversity, particularly driven by higher abundances of Gammaridae, Polychaeta, Copepoda and Caprellidae. Given the key ecological contribution of epifauna to food webs, these alterations will likely have important implications for overall food web structure and ecosystem functioning of native ecosystems.

Ocean acidification (OA) is expected to impact habitat-forming species (HFS), with cascading effects on the whole marine ecosystem and related services that are seldom quantified. Here, the changes in HFSs biomass due to OA are modeled using a food web ecosystem model, and the trophic and non-trophic cascading effects on the marine community are investigated. The food web model represents a well-studied coastal marine protected area in the NW Mediterranean Sea where coralligenous reefs and Posidonia oceanica meadows constitute important HFS. The model is used to implement 5 scenarios of habitat degradation, that is, reduction of HFS biomass, induced by increasing OA and to quantify the potential changes in ecosystem properties and indicators of ecosystem services over the next 100 years. The changes in ecosystem indicators highlight a decrease in the size of the system and a reorganization of energy flows suggesting a high degree of ecosystem development. All the proxies for ecosystem services show significant decreases in their values. Although representing only a portion of the possible impacts of OA, the findings are consistent with the idea that ecological systems can react to OA effects to maintain the level of ecosystem development, but the new organization might not be optimal from an anthropocentric viewpoint. [ABSTRACT FROM AUTHOR]

The ecological physiology of anthozoans, as well as their resistance to stressors, are strongly influenced by environmental factors and the availability of resources. The energy budget of anthozoans can vary seasonally in order to find an equilibrium between the available resources and respiration, polyp activity, growth, and reproduction processes. The variation in the biochemical composition of the animal tissues in these organisms results from a combination of the productivity processes of the water column coupled with the reproductive effort and potential starvation periods of the anthozoans. Here, the seasonal variation in the polyp activity of a slow-growing passive suspension feeder, the octocoral Alcyonium acaule, as well as their carbohydrate, protein and lipid contents, was investigated in a warm temperate environment using in-situ observations and biochemical analyses. Polyp activity exhibited a significant variability that was moderately dependent on season, while an aestivation phenomenon in A. acaule (i.e., a resting period in which the anthozoan is not capable of any polyp activity) during the warmer months is clearly observed. Carbohydrate concentrations in the coral species showed a significant increase in the late winter and spring seasons, and the lipid content increased during the spring. A higher abundance of lipids and carbohydrates coincided with a higher primary productivity in the water column, as well as with the octocoral reproduction period. In late autumn, there was a depletion of these biomolecules, with protein levels exhibiting great variability across sampling times. Complex alterations driven by climate change could affect the energy fluxes that depend on the dead or alive particles that are intercepted by marine animal forests. The obtained findings show a food shortage in late summer and autumn of the benthic suspension feeder A. acaule through the integrative descriptors of the ecophysiology of these anthozoans. This research contributes to the knowledge of energy storage capabilities in benthic suspension feeders in general, highlighting the importance of understanding the limits of resistance to starvation periods through these indicators. [ABSTRACT FROM AUTHOR]

The ecological physiology of anthozoans, as well as their resistance to stressors, are strongly influenced by environmental factors and the availability of resources. The energy budget of anthozoans can vary seasonally in order to find an equilibrium between the available resources and respiration, polyp activity, growth, and reproduction processes. The variation in the biochemical composition of the animal tissues in these organisms results from a combination of the productivity processes of the water column coupled with the reproductive effort and potential starvation periods of the anthozoans. Here, the seasonal variation in the polyp activity of a slow-growing passive suspension feeder, the octocoral Alcyonium acaule, as well as their carbohydrate, protein and lipid contents, was investigated in a warm temperate environment using in-situ observations and biochemical analyses. Polyp activity exhibited a significant variability that was moderately dependent on season, while an aestivation phenomenon in A. acaule (i.e., a resting period in which the anthozoan is not capable of any polyp activity) during the warmer months is clearly observed. Carbohydrate concentrations in the coral species showed a significant increase in the late winter and spring seasons, and the lipid content increased during the spring. A higher abundance of lipids and carbohydrates coincided with a higher primary productivity in the water column, as well as with the octocoral reproduction period. In late autumn, there was a depletion of these biomolecules, with protein levels exhibiting great variability across sampling times. Complex alterations driven by climate change could affect the energy fluxes that depend on the dead or alive particles that are intercepted by marine animal forests. The obtained findings show a food shortage in late summer and autumn of the benthic suspension feeder A. acaule through the integrative descriptors of the ecophysiology of these anthozoans. This research contributes to the knowledge of energy storage capabilities in benthic suspension feeders in general, highlighting the importance of understanding the limits of resistance to starvation periods through these indicators.

Brown macroalgae within the genus Cystoseira are some of the most relevant “ecosystem-engineers” found throughout the Mediterranean and the adjacent Atlantic coasts. Cystoseira-dominated assemblages are sensitive to anthropogenic pressures, and historical declines have been reported from some regions. In particular, Cystoseira abies-marina, thriving on shallow rocky shores, is a key species for the ecosystems of the Canary Islands. In this work, we analyse changes in the distribution and extension of C. abies-marina in the last decades on the island of Gran Canaria. This alga dominated the shallow rocky shores of the entire island in the 1980s; a continuous belt extended along 120.5 km of the coastline and occupied 928 ha. In the first decade of the 21st century, fragmented populations were found along 52.2 km of the coastline and occupied 12.6 ha. Today, this species is found along 37.8 km of the coastline and occupies only 7.4 ha, mainly as scattered patches. This regression has been drastic around the whole island, even in areas with low anthropogenic pressure; the magnitude of the decline over time and the intensity of local human impacts have not shown a significant correlation. This study highlights a real need to implement conservation and restoration policies for C. abies-marina in this region.

The addition or loss of habitat-forming species may lead to significant changes in the structure and functioning of marine benthic ecosystems as a whole. However, the nature of the impact of invasive macroalgae on native mobile invertebrate assemblage is still hard to predict. In this sense, the degree of morphological resemblance (mainly structural complexity) between native and exotic habitat-forming species has been proposed as a suitable predictor of epifauna response to biological invasions. The recently introduced macroalga Rugulopteryx okamurae is becoming a dominant element in coastal rocky bottoms in the Strait of Gibraltar, where it is sympatric with the native species Dictyota dichotoma. Despite the high morphological similarity between both habitat-forming species, native and exotic macroalgae hosted different macrofaunal assemblages. Dictyota dichotoma showed lower number of species, abundance of individuals, and diversity values than the introduced macroalga. Most shared species showed higher abundance on R. okamurae, but there was high variability in the response to macroalgal identity across higher taxa. Thus, there were no major differences in polychaete assemblage between macroalgal species or among sites, when considering univariate measures (abundance of individuals, number of species and H′ values) or species composition (with the exception of abundance values), while peracarid crustaceans and molluscs showed the opposite pattern. Therefore, our results suggest that morphological similarities among habitat-forming species do not always allow predicting of whether the invasive taxa are functionally equivalent to native ones. They also highlight the relevance of fine taxonomical resolution for revealing complex impacts of invasive macroalgae. In addition, R. okamurae's capacity to determine significant changes on native fauna has been pointed out. [ABSTRACT FROM AUTHOR]

Ecosystem engineers influence the habitat, diversity, and productivity of ecosystems. However, multiple ecosystem engineers may coexist, and because of their dominant influence, how they interact can affect the entire system. In the southeastern US, the eastern oyster, Crassostrea virginica (Gmelin) and coarse cordgrass, Spartina alterniflora (Loisel) are two prominent ecosystem engineers that affect estuarine ecosystem functioning. Despite both species' importance and their proximity to one-another, few studies have focused on bidirectional interactions between these two species. First, we assessed the potential effect of fringing oyster reefs on adjacent cordgrass stands. We found that when tidal creek banks are occupied by oysters, cordgrass horizontally extends towards the water 5.25 m more (often overlapping with the oysters) than adjacent bank areas that were lacking oysters. Ostensibly, the positive effect of oysters to increase cordgrass occupancy is due to known abilities of oysters to stabilize shoreline, baffle hydrodynamic energy, and accrete sediment. Second, we experimentally examined the effects of cordgrass on oysters using the presence and absence of cordgrass and cordgrass-mimic treatments to parse the mechanistic effects of structure and shade provided by cordgrass. We found that oysters recruited 2.4 times more and increased biomass 3.2 times more underneath natural cordgrass and shade mimics compared to plots with cordgrass removal and structure-only mimics. Thus, cordgrass shade is an important mechanism of facilitation, especially on small recruiting oysters that are vulnerable to desiccation. Collectively, the mutualism between these two engineers expands their footprints and amount of overlap, strengthening their presence and thus their ecosystem services to the estuary. • Cordgrass facilitates oysters at the upper edge of their intertidal range. • Cordgrass increases upper-reef oyster recruitment 2.4 times, and biomass 3.2 times. • Cordgrass shading recruiting oysters drive the facilitation. • Oysters are correlated with a 5 m (mean) waterward extension of cordgrass habitat. • Cordgrass and oyster distributions (bird's-eye view) overlap by 1.75 m (mean). [ABSTRACT FROM AUTHOR]

Scleractinian cold-water corals (CWCs) are one of the most important habitat engineers of the deep sea. Although the South China Sea (SCS) abuts the biodiversity center of scleractinian CWCs in the western Pacific, only a few sporadic records are available. We discovered new CWC sites by means of trawl sampling and video observation along the continental shelf of the northwestern SCS. All trawled scleractinian CWC specimens were identified to species level according to skeleton morphology and structure. The living CWCs and associated fauna recorded in the video were -identified to a higher level of classification. Scleractinian corals were identified to genus level, while non-scleractinian CWCs were identified to family level and given general names such as gorgonian corals, bamboo corals and black corals. Associated benthic dwellers were divided into major categories. A total of 28 scleractinian CWC species were identified to 7 families, 15 genera, and 1 additional subgenus. Among them, 13 species were colonial, including important habitat-forming species in the genera Eguchipsammia, Dendrophyllia and Cladopsammia. Non-scleractinian CWCs were identified to 7 families, including 4 families gorgonian corals, 1 family bamboo corals, and 2 families black corals. Gorgonian corals were the most abundant non-scleractinian CWCs in this region. Meanwhile, starfish, sea anemones, fish, gastropods, echinoderms, and other associated benthic fauna were recorded in the CWC habitats, with starfish belonging to the order Brisingida being most common. New scleractinian CWC assemblages were discovered along the continental seabed mounds in the northwestern SCS. This study highlights the remarkable diversity of cold-water scleractinian corals in the whole SCS, and shows the potential widespread distribution and conservation prospect of CWC habitats in this region., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This study investigated the influence of physical and chemical conditions and biotic factors on the distribution and diversity of meiofauna in intertidal zone along a geographical gradient. At 11 sites along the Italian coast, we studied the concurring role of environmental variables, trophic resources and the presence of habitat-forming species (macroalgae vs. mussels) in controlling the meiofaunal communities. The increase of water temperature combined with local thermal conditions was associated with a decrease in nematodes and copepods, with a consequent decrease in meiofaunal abundance towards the south. However, the increase in salinity, as geographical gradient decreases, and local thermal conditions favoured the settlement of a greater number of taxa, influencing communities' composition. The presence of macroalgae or mussels differently influenced the community structure of meiofauna on intertidal substrates and their response to environmental factors. From our results, the presence of macroalgae coverage appeared to reduce the impact of thermal stress on meiofauna and was associated with higher levels of meiofaunal diversity with respect to mussels. This work highlighted the importance of considering the interplay among biotic and abiotic factors, resulting in local combinations of environmental conditions, in order to understand the pattern of diversity and distributions of marine organisms. [ABSTRACT FROM AUTHOR]

Along urbanised coastlines, urban infrastructure is increasingly becoming the dominant habitat. These structures are often poor surrogates for natural habitats, and a diversity of eco-engineering approaches have been trialled to enhance their biodiversity, with varying success., We undertook a quantitative meta-analysis and qualitative review of 109 studies to compare the efficacy of common eco-engineering approaches (e.g. increasing texture, crevices, pits, holes, elevations and habitat-forming taxa) in enhancing the biodiversity of key functional groups of organisms, across a variety of habitat settings and spatial scales., All interventions, with one exception, increased the abundance or number of species of one or more of the functional groups considered. Nevertheless, the magnitude of effect varied markedly among groups and habitat settings. In the intertidal, interventions that provided moisture and shade had the greatest effect on the richness of sessile and mobile organisms, while water-retaining features had the greatest effect on the richness of fish. In contrast, in the subtidal, small-scale depressions which provide refuge to new recruits from predators and other environmental stressors such as waves, had higher abundances of sessile organisms while elevated structures had higher numbers and abundances of fish. The taxa that responded most positively to eco-engineering in the intertidal were those whose body size most closely matched the dimensions of the resulting intervention., Synthesis and applications. The efficacy of eco-engineering interventions varies among habitat settings and functional groups. This indicates the importance of developing site-specific approaches that match the target taxa and dominant stressors. Furthermore, because different types of intervention are effective at enhancing different groups of organisms, ideally a range of approaches should be applied simultaneously to maximise niche diversity. [ABSTRACT FROM AUTHOR]

Many invertebrate species use the microhabitats generated by barnacles to settle and to avoid predation and desiccation. In Argentina, the acorn barnacle Balanus glandula not only colonizes rocky shores but has also successfully invaded soft bottom salt marshes, where it form large three-dimensional structures that facilitate the presence of other invertebrates, thus affecting the whole species assemblage. Artificial barnacles were deployed on a Patagonian salt marsh to reproduce the physical structure of natural aggregates. The experiment included natural and material controls and two levels of structural complexity that represent the variety of aggregates found in nature: (i) aggregates with internal empty spaces and galleries among barnacles and (ii) aggregates without spaces and galleries. After nine months, the macroinvertebrate assemblages were compared between treatments. The results showed that the composition of the assemblage differed significantly between artificial treatments and control plots. However, there was no effect of the mimic barnacles on macroinvertebrate richness and diversity. In this way, our results suggest that the physical structure of B. glandula could modify the composition of macroinvertebrate assemblages. Besides, B. glandula recruits were registered on the mimics highlighting the importance that the physical structure supplied by this species could have on its own persistence within invaded soft bottom salt marshes. [ABSTRACT FROM AUTHOR]

Facilitation cascades are increasingly recognized as key drivers of biodiversity in a variety of habitats, yet their temporal variability remains poorly investigated. On shallow subtidal rocky reefs, positive interactions between the canopy-forming species, Halopithys incurva , and its epiphyte, Jania rubens , enhance the abundance and diversity of the associated mobile invertebrate assemblage. By means of a field experiment manipulating the presence of J. rubens on H. incurva plants, we investigated whether the effects of this facilitation cascade varied over time scales of months. Despite seasonal fluctuations in its biomass, J. rubens enhanced total invertebrate abundance and species richness by 64% and 45%, respectively, throughout the experiment. Our results suggest that the presence of J. rubens , likely by providing novel microhabitats and increasing resource availability, sustains invertebrate biodiversity of shallow macroalgal forests consistently between warm and cold periods. Understanding the temporal dynamics of facilitation cascades and their mechanisms can help inform management strategies targeting biodiversity conservation and restoration under current and future climates. [Display omitted] • The temporal dynamic of a facilitation cascade was tested in a shallow rocky reef. • Positive effects of a subtidal macroalga and its epiphyte on mobile invertebrates. • Seasonal variations in epiphyte biomass did not affect the facilitation cascade. • The presence of the epiphyte sustains patterns of biodiversity over time. [ABSTRACT FROM AUTHOR]

During the summer of 2022, an extensive die-off of Dendropoma cristatum and other marine organisms associated with vermetid reefs was observed in the western Mediterranean Sea (northern coast of Sicily). Quantitative data from more than 300 km of coastal stripe indicated that the percentage of dead D. cristatum specimens, showing empty and/or transversely fractured shells, ranged from 64 to 84 % in populations having a density of 2900–4730 ind./m2, suggesting that millions of organisms had recently died along the Sicilian coast. This high mortality range coincided with prolonged desiccation events during which biogenic vermetid reefs were exposed to extreme warm-air conditions for several consecutive days. This warning report about neglected shallow vermetid reefs raises concern regarding the loss of Mediterranean biodiversity, underlining the need to develop and implement monitoring and conservation efforts on a basin-wide scale. • Widespread mortality affecting the neglected vermetid reef in the western Mediterranean Sea • Prolonged desiccation events impacted millions of Dendropoma cristatum specimens. • Effects of climate change on habitat-forming species in the Mediterranean intertidal environment [ABSTRACT FROM AUTHOR]

The distribution of species is shifting in response to recent climate change. Changes in the abundance and distributions of habitat-forming species can have knock-on effects on community structure, biodiversity patterns and ecological processes. We empirically examined temporal changes in the abundance of the warm-water kelp Laminaria ochroleuca at its poleward range edge in the Western English Channel. Resurveys of historical sites indicated that the abundance of L. ochroleuca has increased significantly in recent decades. Moreover, examination of historical records suggested that L. ochroleuca has extended its distribution from sheltered coasts on to moderately wave-exposed open coasts, where it now co-exists and competes with the assemblage dominant Laminaria hyperborea. Proliferation of L. ochroleuca at its poleward range edge corresponds with a period of rapid warming in the Western English Channel. Preliminary comparisons between L. ochroleuca and L. hyperborea highlighted some subtle but ecologically significant differences in structure and function. In summer, the average biomass of epiphytic stipe assemblages on L. hyperborea was 86 times greater than on L. ochroleuca whereas, on average, L. ochroleuca had a greater stipe length and its blade supported 18 times as many gastropod grazers (Gibbula cineraria). Differences in summer growth rates were also recorded, with L. ochroleuca being more productive than L. hyperborea throughout July. Comprehensive seasonally replicated comparisons are needed to examine the wider implications of proliferation of L. ochroleuca at its poleward range edge, but our study suggests that local biodiversity patterns and ecological processes (e.g. timing of productivity and trophic pathways) on shallow subtidal reefs may be altered by shifts in the relative abundances of habitat-forming kelp species. [ABSTRACT FROM AUTHOR]

This study presents an empirical example of how ES can be incorporated into MSP in developing countries, in particular in the Southern region of Los Lagos (Chile). This paper aims to: (a) assess the overlapping incompatibilities within each zoning area, (b) calculate the importance score of the three key ES selected, (c) assess the importance scores of the ES and develop plausible future scenarios for marine zoning. Here, we use InVEST marine models to spatially map the distribution of marine ES (ecotourism and recreation, wildlife endangered species, and habitat-forming species). Taking the current proposal of the MSP as a baseline scenario, two plausible hypothetical future scenarios were also developed based on policies and decision-making trends, and the results of the ES importance score values within each zoning area. The results of this paper indicate that the environmental conservation-aboriginal development scenario would be considered as the more appropriate future projection in terms of securing the three key ES analysed in the region. However, due to changes in the economic development paradigm for the Inner Sea of Chiloe, decision makers, the scientific community and industry representatives are facing a major challenge in allocating appropriate areas to secure ES which requires a holistic perspective. [ABSTRACT FROM AUTHOR]

Invasive species threaten native ecosystems worldwide. However, these species can interact positively with local communities, increasing their richness, or the abundance of some species. Many invasive species are capable of influencing the habitat itself, by ameliorating physical stress and facilitating the colonization and survival of other organisms. Barnacles are common engineer species that can change the physical structure of the environment, its complexity, and heterogeneity through their own structure. Balanus glandula is a native barnacle of the rocky shores of the west coast of North America. In Argentina, this invasive species not only colonizes rocky shores but it also has successfully colonized soft-bottom salt marshes, where hard substrata are a limiting resource. In these environments, barnacles form three-dimensional structures that increase the structural complexity of the invaded salt marshes. In this work, we compared the composition, density, richness, and diversity of the macroinvertebrate assemblages associated with habitats of different structural complexity in two Patagonian salt marshes where B. glandula is well established. Our results showed differences in the relative distribution and abundances of the invertebrate species between habitats of different complexities. Furthermore, the response of the communities to the changes in the structural complexity generated by B. glandula was different in the two marshes studied. This highlights the fact that B. glandula facilitates other invertebrates and affect community structure, mainly where the settlement substrata ( Spartina vs. mussels) are not functionally similar to the barnacle. Thus, our work shows that the rocky shore B. glandula is currently a critical structuring component of the native invertebrate community of soft-bottom environments where this species was introduced along the coast of southern South America. [ABSTRACT FROM AUTHOR]

Kelp species are ecosystem engineers in temperate coasts, where they provide valuable services to humans. Evidence of the declines of kelp forests exists from several regions, but their effects on fisheries still need to be elucidated. More effective management strategies for sustainable fisheries require a synthesis of research findings and an assessment of how research could be improved to fill current gaps., This review aimed to: (i) summarize the available evidence on the influence of changes in kelp density and/or area on the abundance and diversity of associated fisheries and (ii) examine how research on kelp-fisheries interactions could better support effective management., Most studies (67%) reported data ascribable, directly or indirectly, to a positive relationship between kelp and fishery-relevant variables, 11% provided evidence of a negative relationship, 15% indicated species-specific findings and the remaining found unclear or 'neutral' relationships., Important shortcomings were identified, including the paucity of experimental studies suitable to test for unequivocal cause-effect relationships, the disproportion between North America, which is well-studied, and other regions and between the large number of fish-based investigations and the small number of those focusing on other commercially important organisms, and the general lack of studies carried out over spatial and temporal scales comparable to those of global processes driving patterns of distribution of both kelps and fisheries., Synthesis and applications. The consistency of most studies in showing a positive kelp-fishery relationship supports the protection of kelp habitats stated by current environmental directives. However, achieving their goals requires that the limitations we detect are addressed through better connections between research, management practice and policy. This would require the following: (i) researchers to combine multiple approaches (large-scale experimental studies and modelling) for the analysis of kelp-fisheries relationships; (ii) funding agencies to provide resources needed to fill the existing gaps; and (iii) researchers and institutions from less studied regions to strengthen collaborations with those from regions where there have been more investigations into kelp-fishery systems. This is essential under present and predicted environmental changes, with the ultimate aim of conserving and allowing the sustainable use of critically important habitats and of fishery resources relying on these. [ABSTRACT FROM AUTHOR]