Habitat-forming Species Research Articles

Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54ºS-56ºS).

In this study we provide an updated checklist of benthic Cnidaria from SW Atlantic Ocean that comprised the Marine Protected Areas Namuncurá I and II, located at Burdwood bank, and other neighbouring locations. A total of 88 taxa was recorded: 36 hydrozoans and 52 anthozoans from which 32 were octocorals, 10 scleractinian corals, 8 sea anemones and 2 zoanthids. Burdwood bank presented the highest richness considering that 87% of the recorded species inhabit this plateau or its slope. Besides some common species widely distributed in the studied sub-areas, at least 24 species represent new distributional records while few were exclusively recorded at Burdwood bank. The inventory here provided will help to identify key habitat-forming species in a complex habitat where marine animal forests and vulnerable marine ecosystems were previously detected. It will be also a very valuable tool for the management and monitoring of the sub-areas under protection.

Multiple stressors and disturbance effects on eelgrass and epifaunal macroinvertebrate assemblage structure

Multiple forms of environmental change and anthropogenic pressure co-occur in coastal marine ecosystems. These external forces affect ecosystem structure, functioning, and, eventually, services to humans. Studies that include more than 2 simultaneous stressors are still needed to understand potential interactions among multiple stressors. We evaluated single and interactive effects of density reduction of Zostera marina L. (a habitat-forming species), shading, and sediment nutrient enrichment on the response of Z. marina and its associated epifauna over 10 wk. Shading had the greatest effect on reducing the eelgrass relative leaf elongation rate (RLE), non-structural carbohydrate reserves, and eelgrass shoot density. A reduced eelgrass density sustained higher epifaunal densities and increased the eelgrass RLE. Sediment nutrient enrichment increased eelgrass shoot density but decreased epifaunal richness, diversity, and total abundance. Our disturbance and pair of stressors differed in their influence on diversity measures, but all affected assemblage structure. Most of the changes to the epifaunal assemblage and diversity likely occurred due to altered habitat availability and epiphytic algae load. We observed additive, antagonistic, and negatively synergistic interactions among our treatments, while most of the cumulative effects showed dominance by one stressor over another. Our results highlight the importance of field experiments that are based on multiple disturbances and stressors to determine their interaction type on communities.

Native and Invasive Macrophytes Differ in Their Effectiveness as Nurseries for Juvenile Endangered Salmon

For marine biogenic habitats, such as kelp and seagrass, declines and local extinction events cause concern because of the loss of ecosystem services they provide. Many of these habitats function as valuable nurseries, but this function may be eroded when invasive species alter the structure of the habitats. For anadromous salmonids along the northeast Pacific, there is little known about the nursery role of coastal habitats, which presents a challenge for scientists to fully understand their complex life histories necessary for informing resource managers in decision-making processes regarding habitat protection and restoration. To address these issues, we ran a 3-week experiment testing the nursery functions of seagrass (Zostera marina), the invasive alga Sargassum muticum, mixed seagrass-Sargassum, and bare sand plots on the growth, survival, and prey availability for endangered Chinook salmon (Oncorhynchus tshawytscha) smolts. We found mixed effects of each habitat type when compared with each other. Chinook salmon smolts grew less in seagrass when compared with the three other habitats (bare sand, Sargassum, mixed seagrass-Sargassum). However, fish survival was lower in Sargassum habitat compared with seagrass and bare sand. Prey availability was greatest in mixed seagrass-Sargassum habitat compared with bare sand, Sargassum, or seagrass. We used a principal components analysis (PCA) to develop a nursery index using the smolts’ growth rate, percent survival, prey availability, and density of prey in gut contents. The nursery index showed that mixed seagrass-Sargassum habitat had the most positive effects on nursery performance. These results suggest that invasive species can serve positive habitat functions, but only when in the presence of a habitat-forming native species. Our study supports the theory that habitat diversity leads to greater nursery function of coastal ecosystems.

Local Conditions Influence the Prokaryotic Communities Associated With the Mesophotic Black Coral Antipathella subpinnata.

Black corals are important habitat-forming species in the mesophotic and deep-sea zones of the world’s oceans because of their arborescent colony structure and tendency to form animal forests. Although we have started unraveling the ecology of mesophotic black corals, the importance of the associated microbes to their health has remained unexplored. Here, we provide in-depth assessments of black coral-microbe symbioses by investigating the spatial and temporal stability of these associations, and make comparisons with a sympatric octocoral with similar colony structure. To this end, we collected samples of Antipathella subpinnata colonies from three mesophotic shoals situated along the Ligurian Coast of the Mediterranean Sea (Bordighera, Portofino, Savona) in the spring of 2017. At the Portofino shoal, samples of A. subpinnata and the gorgonian Eunicella cavolini were collected in November 2016 and May 2017. Bacterial communities were profiled using 16S rRNA gene amplicon sequencing. The bacterial community of E. cavolini was consistently dominated by Endozoicomonas. Contrastingly, the black coral microbiome was more diverse, and was primarily composed of numerous Bacteroidetes, Alpha- and Gammaproteobacterial taxa, putatively involved in all steps of the nitrogen and sulfur cycles. Compositional differences in the A. subpinnata microbiome existed between all locations and both time points, and no phylotypes were consistently associated with A. subpinnata. This highlights that local conditions may influence the bacterial community structure and potentially nutrient cycling within the A. subpinnata holobiont. But it also suggests that this coral holobiont possesses a high degree of microbiome flexibility, which may be a mechanism to acclimate to environmental change.

Spatial patterns of continental shelf faunal community structure along the Western Antarctic Peninsula.

Knowledge of continental shelf faunal biodiversity of Antarctica is patchy and as such, the ecology of this unique ecosystem is not fully understood. To this end, we deployed baited cameras at 20 locations along ~ 500 km of the Western Antarctic Peninsula (WAP) at depths from 90 to 797 m. We identified 111 unique taxa, with mud bottom accounting for 90% of the dominant (≥ 50% cover) habitat sampled. Amphipoda comprised 41% of the total maximum number of individuals per camera deployment (MaxN) and occurred on 75% of deployments. Excluding this taxon, the highest MaxN occurred around King George/25 de Mayo Island and was driven primarily by the abundance of krill (Euphausiidae), which accounted for 36% of total average MaxN among deployments around this island. In comparison, krill comprised 22% of total average MaxN at Deception Island and only 10% along the peninsula. Taxa richness, diversity, and evenness all increased with depth and depth explained 18.2% of the variation in community structure among locations, which may be explained by decreasing ice scour with depth. We identified a number of Vulnerable Marine Ecosystem taxa, including habitat-forming species of cold-water corals and sponge fields. Channichthyidae was the most common fish family, occurring on 80% of all deployments. The Antarctic jonasfish (Notolepis coatsorum) was the most frequently encountered fish taxa, occurring on 70% of all deployments and comprising 25% of total MaxN among all deployments. Nototheniidae was the most numerically abundant fish family, accounting for 36% of total MaxN and was present on 70% of the deployments. The WAP is among the fastest warming regions on Earth and mitigating the impacts of warming, along with more direct impacts such as those from fishing, is critical in providing opportunities for species to adapt to environmental change and to preserve this unique ecosystem.

Seagrass Cymodocea nodosa across biogeographical regions and times: Differences in abundance, meadow structure and sexual reproduction

Seagrasses are key habitat-forming species of coastal areas. While previous research has demonstrated considerable small-scale variation in seagrass abundance and structure, studies teasing apart local from large-scale variation are scarce. We determined how different biogeographic scenarios, under varying environmental and genetic variation, explained variation in the abundance and structure (morphology and biomass allocation), epiphytes and sexual reproduction intensity of the seagrass Cymodocea nodosa. Regional and local-scale variation, including their temporal variability, contributed to differentially explain variation in seagrass attributes. Structural, in particular morphological, attributes of the seagrass leaf canopy, most evidenced regional seasonal variation. Allocation to belowground tissues was, however, mainly driven by local-scale variation. High seed densities were observed in meadows of large genetic diversity, indicative of sexual success, which likely resulted from the different evolutionary histories undergone by the seagrass at each region. Our results highlight that phenotypic plasticity to local and regional environments need to be considered to better manage and preserve seagrass meadows.

Assessing the environmental status of selected North Atlantic deep-sea ecosystems

The deep sea is the largest biome on Earth but the least explored. Our knowledge of it comes from scattered sources spanning different spatial and temporal scales. Implementation of marine policies like the European Union’s Marine Strategy Framework Directive (MSFD) and support for Blue Growth in the deep sea are therefore hindered by lack of data. Integrated assessments of environmental status require tools to work with different and disaggregated datasets (e.g. density of deep-sea habitat-forming species, body-size distribution of commercial fishes, intensity of bottom trawling) across spatial and temporal scales. A feasibility study was conducted as part of the four-year ATLAS project to assess the effectiveness of the open-access Nested Environmental status Assessment Tool (NEAT) to assess deep-sea environmental status. We worked at nine selected study areas in the North Atlantic focusing on five MSFD descriptors (D1-Biodiversity, D3-Commercial fish and shellfish, D4-Food webs, D6-Seafloor integrity, D10-Marine litter). The objectives of the present study were to i) explore and propose indicators that could be used in the assessment of deep-sea environmental status, ii) evaluate the performance of NEAT in the deep sea, and iii) identify challenges and opportunities for the assessment of deep-sea status. Based on data availability, data quality and expert judgement, in total 24 indicators (one for D1, one for D3, seven for D4, 13 for D6, two for D10) were used in the assessment of the nine study areas, their habitats and ecosystem components. NEAT analyses revealed differences among the study areas for their environmental status ranging from “poor” to “high”. Overall, the NEAT results were in moderate to complete agreement with expert judgement, previous assessments, scientific literature on human-pressure gradients and expected management outcomes. We suggest that the assessment of deep-sea environmental status should take place at habitat and ecosystem level (rather than at species level) and at relatively large spatial scales, in comparison to shallow-water areas. Limited knowledge across space (e.g. distribution of habitat-forming species) and the scarcity of long-term data sets limit our knowledge about natural variability and human impacts in the deep sea preventing a more systematic assessment of habitat and ecosystem components in the deep sea. However, stronger cross-sectoral collaborations, the use of novel technologies and open data-sharing platforms will be critical for establishing environmental baseline indicator values in the deep sea that will contribute to the science base supporting the implementation of marine policies and stimulating Blue Growth.

Species Distribution Modeling Predicts Significant Declines in Coralline Algae Populations Under Projected Climate Change With Implications for Conservation Policy

Anthropogenic climate change presents a major challenge to coastal ecosystems. Mass population declines or geographic shifts in species ranges are expected to occur, potentially leading to wide-scale ecosystem disruption or collapse. This is particularly important for habitat-forming species such as free-living non-geniculate coralline algae that aggregate to form large, structurally complex reef-life ecosystems with high associated biodiversity and carbon sequestration capability. Coralline algal beds have a worldwide distribution, but have recently experienced global declines due to anthropogenic pressures and changing environmental conditions. However, the environmental factors controlling coralline algal bed distribution remain poorly understood, limiting our ability to make adequate assessments of how populations may change in the future. We constructed the first species distribution model for non-geniculate coralline algae (focusing on maerl-forming species but including crustose coralline algae associated with coralline algal beds) and showed that bathymetry, temperature at the seabed and light availability are the primary environmental drivers of present-day non-geniculate coralline algae distribution. Our model also identifies suitable areas for species presence that currently lack records of occurrence. Large-scale spatial declines in coralline algal distribution were observed under all IPCC Representative Concentration Pathways (ranging from 38% decline under RCP 2.6 up to 84% decline under RCP 8.5), with the most rapid rate of decline up to 2050. Refuge populations that may persist under projected climate change were also identified – informing priority areas for future conservation efforts to maximise the long-term survival of this globally important ecosystem.

Evidences of human impact on megabenthic assemblages of bathyal sediments in the Alboran Sea (western Mediterranean)

Megabenthic assemblages in deep-sea sedimentary environments receive far less attention than those occurring on rocky environments, despite they have been widely impacted by destructive trawling activities, mainly due to their association with important commercial species. ROV dives conducted on bathyal muds of the Alboran Sea continental slope (western Mediterranean) were used to characterize megabenthic assemblages, as well as assess their response to trawling and benthic litter. We identified a multispecific assemblage, dominated by the isidid Isidella elongata, and two monospecific assemblages composed by the sea-pens Funiculina quadrangularis and Kophobelemnon stelliferum. These assemblages are defined as vulnerable marine ecosystems by international institutions. Trawled areas exhibit significant low densities of habitat-forming species and a striking impoverishment of habitat complexity and diversity. Plastic debris and lost fishing gears were the most abundant components of the marine litter. This study highlights the destructive effects of human activities on bathyal muds, emphasizing the need for urgent conservation measures.

Local Scale Thermal Environment and Limited Gene Flow Indicates Vulnerability of Warm Edge Populations in a Habitat Forming Macroalga

Species inhabiting warm-edge populations of their distribution are suggested to be at the forefront of global warming due to reduced fitness, limited gene flow and living close to their physiological thermal limits. Determining the scale that governs thermal niche and the functional responses of habitat-forming species to environmental stressors is critical for successful conservation efforts, particularly as coastal ecosystems are impacted by global change. Here, we examine the susceptibility of warm-edge populations to warming, in the habitat-forming macroalga, Hormosira banksii, from south-eastern Australia. We use a quantitative breeding design to quantify intraspecific variation in thermal performance (growth, ontogenic development and photosynthetic efficiency) of different genotypes sourced from sites at the equatorward distributional edge (warm-edge) and those towards the center of its distribution (non-edge). The genetic diversity and structure of H. banksii was also examined using microsatellite markers amongst the same sites. Our results found variable responses in thermal performance for growth and development. Warm-edge germlings grew optimally in lower temperatures tested and had narrower thermal breadth compared to non-edge germlings which grew in higher and more broader temperatures. Warm-edge germlings however, showed greater plasticity to tolerate high light indicated by a greater proportion of energy being dissipated as regulated nonphotochemical quenching (Y(NPQ)) than nonregulated nonphotochemical quenching (Y(NO)). Overall genetic diversity was lower at the warm-edge location with evidence of increased structuring and reduced gene flow in comparison to the non-edge location. Evidence of genetic structuring was not found locally between high and low shore within sites. Together, these data suggest that non-edge populations may be “thermally buffered” from increased temperatures associated with ocean warming. Warm-edge populations of H. banksii, however, may be vulnerable to warming, due to narrower thermal breadth and sensitivity to higher temperatures, with genetic impoverishment through loss of individuals likely to further reduce population viability.

Consumer control and abiotic stresses constrain coastal saltmarsh restoration

Die-off of coastal wetlands has been reported worldwide. Planting habitat-forming species is an important strategy to reverse the decline of coastal wetlands. However, how abiotic environmental stresses and consumers affect the establishment of the planted vegetation species is unclear. We reported a large-scale restoration project in the Liaohe estuary, China, where native pioneer plant Suaeda salsa was planted. We evaluated the growth performance of the planted S. salsa, and identified the constraints on the establishment of planted S. salsa. Results showed that the growth performance (density, coverage and survival rate) of planted S. salsa was better in the low restored marsh than that in the high restored marsh. The death of planted S. salsa was primarily driven by crab herbivory, followed by abiotic stresses (low soil moisture and high salinity) in the high restored marsh, whereas plant death was only driven by crab herbivory in the low restored marsh. Herbivory strength in the high marsh was significantly higher than that in the low marsh. Our findings challenge the bottom-up paradigm used as the foundation for coastal restoration, and highlight the overlooked role of consumers. Therefore, protection measures against consumer pressure, especially in physically harsh conditions, should be considered to enhance the success of coastal wetland restoration.

Habitat forming species explain taxonomic and functional diversities in a Mediterranean seamount

Complexity provided by habitat-forming species in marine ecosystems has been linked to higher species richness and biodiversity as well as enhancing ecosystem functioning. This study assesses how the presence of biogenic component of benthic habitats affects the taxonomic richness and functional diversities of a seamount benthos. We used a variety of complementary metrics on abundance data and quantitative community analyses to detail the composition, structure, diversity and functionality of eight biogenic and five non-biogenic benthic habitats across the Seco de los Olivos Seamount, located to the south of the Iberian Peninsula, in the western Mediterranean. This study shows that the presence of habitat-forming species in benthic habitats increases richness and enhances α and functional diversities. Their influence is more evident in soft and mixed bottoms, where the multiplying effect on structural complexity is proportionally greater than in rocky habitats. Biogenic habitats hosted a higher number of single species in comparison with non-biogenic habitats. The presence of habitat-forming species also determines β diversity among habitats at similar depth and type of substrate, with variation in species richness responsible for the most β diversity; turnover, however, dominated β diversity among habitats of different environments. Species richness hotspots were also associated to biogenic structures and were found restricted to the summit of the central guyot and other areas located on the surrounding ridges. Different functional composition of these benthic habitats also suggested differences in ecosystem functioning: biogenic habitats resembled more stable or at advanced stages of successional maturity than non-biogenic habitats and are characterized by biological traits that allow them to better promote benthic-pelagic coupling. From aconservation perspective an increased functional redundancy was found related to the occurrence of habitat-forming species in high abundance, which favours functional replacement and makes communities less vulnerable to environmental changes. The results of this study can help managers to develop specific management tools to ensure the future evaluation and monitoring of benthic communities.

Know Thy Anemone: A Review of Threats to Octocorals and Anemones and Opportunities for Their Restoration

In studies of habitat-forming species, those that are not spatially dominant are often considered ‘non-primary’ habitat and may be overlooked. This is despite the fact that minority habitat formers can provide critical complexity, food, and other services that underpin ecosystem biodiversity. Octocorals and anemones are found in marine and estuarine habitats across all climate zones. Despite their potentially important ecological roles, to date there have been few studies of their specific threats and stressors or attempts at their restoration. Here we review studies of the ecology of octocorals and anemones with a focus on threats and restoration. We identify many threats including habitat damage, collection and trade, disease, predation, pollution, and the most wide-spread – climate change. While evidence suggests that some octocorals and anemone populations may be more resilient to disturbances than stony corals because they often recruit and grow quickly, resilience is not guaranteed. Instead, resilience or susceptibility within this large group is likely to be site and species specific. We find that the loss of octocorals and anemones has been difficult to quantify as most species have no hard structures that remain following a mortality event. Only through long-term monitoring efforts have researchers been able to document change in these populations. Due to the increasing extent and severity of human impacts in marine ecosystems, restoration of habitat forming species is becoming increasingly necessary after disturbance events. To illustrate the challenges ahead for octocoral and anemone restoration, we present two examples of ongoing restoration efforts assessed against the International Standards for the Practice of Ecological Restoration. Restoration planning and implementation progress are documented for the Mediterranean red coral Corallium rubrum and the temperate Australian cauliflower soft coral, Dendronephthya australis. This review and the detailed case studies demonstrate that while some octocorals and anemones can provide resilient habitat within reef systems, a greater research focus on their ecology, threats, and restoration potential is urgently required.

Interacting effects of habitat structure and seeding with oysters on the intertidal biodiversity of seawalls.

The construction of artificial structures, such as seawalls, is increasing globally, resulting in loss of habitat complexity and native species biodiversity. There is increasing interest in mitigating this biodiversity loss by adding topographic habitat to these structures, and/or seeding them with habitat-forming species. Settlement tile experiments, comparing colonisation of species to more and less complex habitats, have been used to inform eco-engineering interventions prior to their large-scale implementation. Most studies have focused on applying one type of intervention (either adding habitat structure or seeding with native organisms), so it is unclear whether there are greater benefits to biodiversity when multiple interventions are combined. Using a fully orthogonal experiment, we assessed the independent and interactive effects of habitat structure (flat vs. crevice/ridges) and seeding with native oysters (unseeded vs. seeded) on the biodiversity of four different functional groups (sessile and mobile taxa, cryptobenthic and pelagic fishes). Concrete tiles (flat unseeded, flat seeded, complex unseeded and complex seeded) were deployed at two sites in Sydney Harbour and monitored over 12 months, for the survival and colonisation of oysters and the species density and abundances of the four functional groups. The survival of seeded oysters was greater on the complex than flat tiles, at one of the two sites, due to the protective role of crevices. Despite this, after 12 months, the species density of sessile invertebrates and the percentage cover of seeded and colonising oysters did not differ between complex and seeded tiles each of which supported more of these variables than the flat unseeded tiles. In contrast, the species density of mobile invertebrates and cryptobenthic fishes and the MaxN of pelagic fishes, at 1 month, were only positively influenced by seeding with oysters, which provided food as well as habitat. Within the complex seeded and unseeded tiles, there was a greater species density of sessile taxa, survival and percentage cover of oysters in the crevices, which were more humid and darker at month 12, had lower high temperature extremes at months 1 and 12, than on the ridges or flat tiles. Our results suggest that eco-engineering projects which seek to maximise the biodiversity of multiple functional groups on seawalls, should apply a variety of different microhabitats and habitat-forming species, to alter the environmental conditions available to organisms.

Shipwrecks help invasive coral to expand range in the Atlantic Ocean

The invasive coral Tubastraea tagusensis (sun coral) is a habitat-forming species currently increasing its geographical range into the Atlantic Ocean, thereby causing negative ecological and socioeconomic impacts. Scuba divers observed this coral in the western equatorial Atlantic in January 2020, growing at high densities on a shipwreck from World War II (sunk in 1943) at a depth of approximately 32 m. Available footage from the beginning of the decade (2012–2018) shows no obvious signs of sun coral on this shipwreck, suggesting recent colonization and range expansion. The recent evidence of expansion was found 200 km east of the last record, which was also found on a WWII shipwreck (sunk in 1942) in 2016. We have identified hundreds of overlooked WWII shipwrecks, as well as new wrecks in shallow and mesophotic waters, that may provide stepping-stone habitats for this coral to expand its distribution in the Atlantic. We discuss the role of shipwrecks as a network of stepping stones for the sun coral spread, creating complementary paths for the invasiveness by overcoming physiological traits and the short lifespan of the coral larvae. Previous research underestimates the importance of these artificial stepping-stone patches in sustaining crucial dispersal events and range expansion of invasive species. These results are a call to action to manage the invasive Tubastraea corals at a national and international scale in the Atlantic basin.

Sublethal effects of contaminants on marine habitat-forming species: a review and meta-analysis.

ABSTRACTContaminants may affect ecosystem functioning by reducing the fitness of organisms and these impacts may cascade through ecosystems, particularly if the sensitive organisms are also habitat‐forming species. Understanding how sub‐lethal effects of toxicants can affect the quality and functions of biogenic habitats is critical if we are to establish effective guidelines for protecting ecosystems. We carried out a global systematic review and meta‐analysis critically evaluating contaminant effects on properties of habitat‐formers linked to ecosystem functioning. We reviewed a total of 95 publications. However, 40% of publications initially captured by the literature search were identified as having flaws in experimental design and ~11% did not present results in an appropriate way and thus were excluded from the quantitative meta‐analysis. We quantitatively reviewed 410 studies from 46 publications, of which 313 (~76%) were on plants and seaweeds, that is macro‐algae, saltmarsh plants and seagrasses, 58 (~14%) studied corals and 39 (~10%) looked at toxicant impacts on bivalves, with 70% of those on mussels and the remaining studies on oysters. Response variables analysed were photosynthetic efficiency, amount of chlorophyll a (as a proxy for primary production) and growth of plants, seaweeds and corals as well as leaf area of plants. We also analysed filtration, growth and respiration rates of bivalves. Our meta‐analysis found that chemical contaminants have a significant negative impact on most of the analysed functional variables, with the exception of the amount of chlorophyll a. Metals were the most widely harmful type of contaminant, significantly decreasing photosynthetic efficiency of kelps, leaf area of saltmarsh plants, growth of fucoids, corals and saltmarsh plants and the filtration rates of bivalves. Organic contaminants decreased the photosynthetic efficiency of seagrass, but had no significant effects on bivalve filtration. We did not find significant effects of polycyclic aromatic hydrocarbons on any of the analysed functional variables or habitat‐forming taxa, but this could be due to the low number of studies available. A meta‐regression revealed that relationships between concentrations of metal contaminants and the magnitude of functional responses varied with the type of metal and habitat‐former. Increasing concentrations of contaminants significantly increased the negative effects on the photosynthetic efficiency of habitat‐formers. There was, however, no apparent relationship between ecologically relevant concentrations of metals and effect sizes of photosynthetic efficiency of corals and seaweeds. A qualitative analysis of all relevant studies found slightly different patterns when compared to our quantitative analysis, emphasising the need for studies to meet critical inclusion criteria for meta‐analyses. Our study highlights links between effects of contaminants at lower levels of organisation (i.e. at the biochemical and/or physiological level of individuals) and ecological, large‐scale impacts, through effects on habitat‐forming species. Contaminants can clearly reduce the functioning of many habitat‐forming marine species. We therefore recommend the adoption of routine measures of functional endpoints in monitoring and conservation programs to complement structural measures.

Predicting the Impact of Climate Change on the Distribution of the Key Habitat-Forming Species in the Ne Baltic Sea

Torn, K.; Peterson, A., and Herkul, K., 2020. Predicting the impact of climate change on the distribution of the key habitat-forming species in the NE Baltic Sea. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 177–181. Coconut Creek (Florida), ISSN 0749-0208.Macrophytes provide food, shelter and habitat for a multitude of other species and are therefore considered as important habitat-forming species. Loss or decrease of habitat-forming species severely affects biodiversity and functioning of coastal marine ecosystems. In the brackish Baltic Sea, such special, structuring species are large perennial macroalgae Fucus vesiculosus and Furcellaria lumbricalis on hard seabed and eelgrass Zostera marina and charophytes (Chara spp.) on soft substrates. The Baltic Sea is expected to face severe changes in environmental conditions due to climate change by the end of the 21st century, e.g. decrease in salinity and increase in temperature, wind speed, and storminess. It is essential to forecast changes in the distribution of valuable species in order to provide data for marine environmental protection and management decisions. Boosted regression trees modelling method was used to produce current species distribution models and predict the potential changes based on future climate scenario. Data from over 10 000 benthic sampling sites were used as an input for distribution models. Following the influence of the water depth, the next major drivers of species distribution were substrate type for Fucus, temperature for the charophytes and Furcellaria, and salinity for Zostera. Based on the model predictions, the climate change may cause a significant reduction of the distributional range of Zostera and Furcellaria. Slight decline of Fucus was also detected. Unlike the other habitat-forming species, charophytes are potential winners by probably increasing their distribution in the future. However, charophytes are not able to replace the niche of the other key habitat-forming species due to different substrate, wave exposure and salinity preferences.

Long-term changes (1800–2019) in marine vegetational habitats: Insights from a historic industrialised coastal area

Macrophytes play an important structural and functional role in marine ecosystems but are experiencing a considerable decline in many areas of the Mediterranean Sea. Despite the long tradition of studies on vegetated marine habitats in the Gulf of Naples (Italy), a gap of knowledge on their long-term dynamics has recently been highlighted, mainly in the most anthropised areas. This work aimed to provide insights from the historic industrialised coastal area of the Site of National Interest (SIN) Bagnoli-Coroglio (Gulf of Pozzuoli, Italy), after decades of chemical contaminations and coastal transformation, to build a baseline for the next remediation and restoration programs. Historical occurrence of macroalgae and seagrasses before, during and after the industrial period was assessed; in particular, we focused the attention mainly on habitat-forming species, due to the vital function played in the trophic net. We observed no differences in the macroalgal diversity between the SIN district and the other parts of the Gulf of Pozzuoli, except for the Gulf of Pozzuoli during the industrial period, where the biodiversity showed a decreasing trend. However, a substantial regression of the largest macrophytes (Fucales) on rocky coasts and of marine monocots on sandy bottoms, all over the area, has been recorded. A loss of about 70% has concerned seagrass cover, mainly Posidonia oceanica, in the contaminated area of the SIN: at present, this engineering species is missing on the bottom, facing the industrialised area. The human-made coastline transformation, the lack of natural substrates and the spatial remoteness among donor populations seem to be the leading causes of the significant decrease, over time, of marine forests in this study area. These factors should be taken into account to establish conservation priorities and for plant restoration.

Heat wave intensity can vary the cumulative effects of multiple environmental stressors on Posidonia oceanica seedlings

Climate change is introducing new stressors into already stressed ecosystems. Among these, extreme events such as heat waves play a crucial role in determining the structure of ecosystems. We tested single and combined effects of overgrazing, burial and heat waves on the seedlings of the habitat-forming species Posidonia oceanica. At current heat wave temperatures, overgrazing in isolation had more deleterious effects than seed burial, and effects were synergistic and additive when both factors co-occurred. The combined effect of overgrazing and seed burial with current heat waves could hamper P. oceanica seedling development, with similar or even higher levels than the sole effect of heat waves in the near future (29 °C). The effects of overgrazing and seed burial are expected to be overridden if heat waves temperatures exceed 29 °C. These results suggest that co-occurring environmental stressors, in combination with current heat waves, could compromise the sexual recruitment of this seagrass.

Distribution and Suitable Habitat of the Cold-Water Corals Lophelia pertusa, Paragorgia arborea, and Primnoa resedaeformis on the Norwegian Continental Shelf

Cold-water corals are habitat-forming species that are also classified as indicators of Vulnerable Marine Ecosystems (VMEs) due to the threat of various anthropogenic impacts e.g. fisheries and oil/mineral exploration. To best protect VMEs, knowledge of their habitat requirements and distribution is essential. However, comprehensive sampling of the deep sea is difficult due to access and cost constraints, so species distribution modeling (SDM) is often used to predict overall distributions and ecological preferences of species based on limited data. We used Maximum Entropy (Maxent) modeling to predict the probability of presence of the reef-building scleractinian Lophelia pertusa and the octocorals Paragorgia arborea and Primnoa resedaeformis using a total of 2149 coral presence points and 15 environmental predictor variables. The environmental variables used in the analysis were processed to 176m resolution and included bathymetry, depth, geomorphometric characteristics (slope, aspect and bathymetric position index (BPI)), oceanography (temperature, salinity, current directions and speed), surface chlorophyll a concentration, sediment type, and marine landscape type. Comparing presence points with environmental data showed that the temperature and depth range for Lophelia was narrower compared to the gorgonians, and it occurred in shallower, warmer water. Observations showed that Lophelia had a broad, bimodal response to Broad BPI, while the predicted model indicated a more narrow response. Paragorgia tolerated the greatest range of sloping according to the model. All three species were observed with a bimodal pattern along a wide range of mean current speed, while the models indicated a high response to faster current speed. Jackknife tests showed that sediment type was an important predictor for gorgonian corals, while BPI and minimum temperature were more important for Lophelia. The spatial precision of the models could be further increased by applying environmental layers with a higher and uniform spatial resolution. The predicted distribution of corals and their relation to environmental variables provides an important background for prioritizing areas for detailed mapping surveys and will aid in the conservation efforts for these VMEs in Norwegian waters and beyond.