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Disturbances often cause the disproportionate loss of foundation species but understanding how the frequency and severity of disturbance to such organisms influence biological communities remains unresolved. This gap in knowledge exists in part because of the rarity of ecologically meaningful studies capable of disentangling different elements of disturbance. Hence, we carried out a long-term (9 yr), large-scale (2,000 m² plots), spatially replicated (4 sites) field experiment in which we manipulated disturbance to a globally distributed marine foundation species, the giant kelp Macrocystis pyrifera, and tracked community responses over time. To distinguish the effects of disturbance frequency and severity on the biodiversity and composition of temperate rocky reef communities, we simulated the repeated loss of giant kelp from destructive winter waves across a background of natural variation in disturbance. By following the response of over 200 taxa from the surrounding community, we discovered that the frequency of disturbance to giant kelp changed the biomass, diversity, and composition of community guilds in a manner commensurate with their dependence on the physical (i.e., benthic light and space), trophic (i.e., living and detrital biomass), and habitat (i.e., biogenic structure) resources mediated by this foundation species. Annual winter disturbance to giant kelp reduced living and detrital giant kelp biomass by 57% and 40%, respectively, enhanced bottom light by 22%, and halved the seafloor area covered by giant kelp holdfasts. Concomitantly, the biomass of understory algae and epilithic sessile invertebrates more than doubled, while the biomass of rock-boring clams, mobile invertebrates, and fishes decreased 30–61%. Frequent loss of giant kelp boosted understory algal richness by 82% and lowered sessile invertebrate richness by 13% but did not affect the biodiversity of mobile fauna. In contrast to changes driven by disturbance frequency, interannual variation in the severity of disturbance to giant kelp had weaker, less consistent effects, causing only modest changes in assemblages of sessile invertebrates, mobile invertebrate herbivores, and fishes. Our results broaden the foundation species concept by demonstrating that repeated disturbance to a dominant habitat-forming species can outweigh the influence of less frequent but severe disturbances for the surrounding community.

Cryopreservation of receptacles or fertilized eggs is the main method for the preservation of indoor germplasm resources for the economic seaweed Sargassum fusiforme . However, none of these methods can achieve long-term preservation of germplasm resources. The holdfast represents the asexual reproductive organ of S. fusiforme and has a dense tissue that can be regenerated into seedlings under suitable conditions. Therefore, in this study, the holdfast was used as the experimental material to analyze the effects of different temperatures (8 °C, 10 °C, 13 °C) and salinities (29‰, 24‰, 19‰, 14‰) on the preservation of S. fusiforme germplasm. The results showed that 29‰ and 14‰ were not suitable for the long-term preservation of holdfasts regardless of temperatures, since both photosynthesis and growth rates of the holdfast decreased after 30 days of preservation at these salinities. However, 8 °C and 19‰ were found to be suitable for the long-term in vitro preservation of holdfasts, with a survival time being as long as 120 days. During the experiment, the photosynthesis activity of the holdfast also displayed less fluctuation in this experimental condition than in the others. After 120 days, the content of malondialdehyde in the holdfasts was the lowest, and the morphology remained intact. 8 °C and 19‰ could be suitable for long-term indoor preservation of S. fusiforme . These findings might provide technical support for solving the problem associated with the difficulty of preserving the germplasm of superior strains in the breeding process. They might also have important significance for crossbreeding and for establishing a germplasm resource bank for S. fusiforme in the future.

Giant kelp Macrocystis pyrifera is a foundational species that forms a 3-dimensional habitat and supports numerous high-value fisheries species. Constant grazing of kelp holdfasts by overabundant sea urchins causes catastrophic ecological and economic impacts on rocky reefs worldwide. Overgrazing creates urchin barrens that persist for decades in the absence of ecological forcing that would shift the ecosystem back to a kelp-dominated state. Annual surveys of kelp forest and urchin barren sites in the Southern California Bight were performed from 2011 to 2020 to assess changes in kelp forest communities as a result of restoration efforts through sea urchin culling. However, that time period also encompassed a sea urchin mass mortality event. Following drastic reductions of sea urchin densities, rocky reefs returned to a kelp-dominated state within approximately 6 mo and remained stable through the remainder of the study. Benthic cover, fish, and kelp and macroinvertebrate communities inside former urchin barrens became more similar to that of kelp forest reference sites and continued to do so for the next 5 yr. Giant kelp density increased significantly compared to existing kelp forests, while benthic indicators of urchin dominance (i.e. crustose coralline algae and bare rock cover) decreased. Kelp restoration through sea urchin culling essentially mimics sea urchin mass mortality events. If culling can produce similar declines in urchin density, it may be a viable management tool to rapidly restore persistent urchin barrens at moderate spatial scales, while a mass mortality event can drive recovery of kelp forest communities at more extensive spatial scales.

Because the informative Burgess Shale-type preservation is uncommon in the Ediacaran, mouldic Ediacara-type preservation provides insight into the early evolution of organisms like metazoans (including typical fronds), protists, and algae. Here, we report the Burgess Shale-type preservation from the new Tongshan Lagerstätte ( ~ 551–543.74 ± 0.87 Ma), in carbonaceous mudstones/shales of the terminal Ediacaran Dengying Formation in Tongshan, Hubei, South China. The preservation of a high diversity of organisms indicates rapid, likely in situ burial in the marine photic zone below the storm wave base, revealing deep-water biodiversity coeval with the Nama Assemblage of Ediacara Biota. These are the first records, to our knowledge, of typical Ediacaran rangeomorph fronds with Burgess Shale-type preservation. The presence of Burgess Shale-type preservation of fronds reflects the rarity of fine-grained deposits in the Ediacaran Period and bridges an important gap between traditional Ediacara-type preservation, Ediacara-type preservation with organic remains, and Burgess Shale-type preservation. Here, the authors present Ediacaran fossils from the Tongshan Lagerstätte (South China), including Burgess Shale-type rangeomorphs preserved both with fronds and holdfasts. They use sedimentary and chemical evidence to suggest that fast burial and early diagenetic mineralization produced excellent preservation.

Aim: In marine ecosystems, habitat-forming species (HFS) such as reef-building corals and canopy-forming macroalgae alter local environmental conditions and can promote biodiversity by providing biogenic living space for a vast array of associated organisms. We examined community-level impacts of observed climate-driven shifts in the relative abundances of two superficially similar HFS, the warm-water kelp Laminaria ochroleuca and the cool-water kelp Laminaria hyperborea. Location: Western English Channel, north-east Atlantic Methods: We compared algal and invertebrate assemblages associated with kelp stipes and holdfasts, across multiple sites and sampling events. Significant differences were recorded in the structure of assemblages between the host kelp species at each site and event. Results: Assemblages associated with stipes of the cool-water HFS were, on average, >12 times more diverse and supported >3600 times more biomass compared with the warm-water HFS. Holdfast assemblages also differed significantly between species, although to a lesser extent than those associated with stipes. Overall, assemblages associated with the warm-water HFS were markedly impoverished and comprised far fewer rare or unique taxa. Main conclusions: While previous research has shown how climate-driven loss of HFS can cause biodiversity loss, our study demonstrates that climate-driven substitutions of HFS can also lead to impoverished assemblages. The indirect effects of climate change remain poorly resolved, but shifts in the distributions and abundances of HFS may invoke widespread ecological change, especially in marine ecosystems where facilitative interactions are particularly strong.

Why large and diverse skeletons first appeared ca 550 Ma is not well understood. Many Ediacaran skeletal biota show evidence of flexibility, and bear notably thin skeletal walls with simple, non-hierarchical microstructures of either aragonite or high-Mg calcite. We present evidence that the earliest skeletal macrobiota, found only in carbonate rocks, had close soft-bodied counterparts hosted in contemporary clastic rocks. This includes the calcareous discoidal fossil Suvorovella, similar to holdfasts of Ediacaran biota taxa previously known only as casts and moulds, as well as tubular and vase-shaped fossils. In sum, these probably represent taxa of diverse affinity including unicellular eukaryotes, total group cnidarians and problematica. Our findings support the assertion that the calcification was an independent and derived feature that appeared in diverse groups where an organic scaffold was the primitive character, which provided the framework for interactions between the extracellular matrix and mineral ions. We conclude that such skeletons may have been acquired with relative ease in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. The trigger for Ediacaran biomineralization may have been either changing seawater Mg/Ca and/or increasing oxygen levels. By the Early Cambrian, however, biomineralization styles and the range of biominerals had significantly diversified, perhaps as an escalating defensive response to increasing predation pressure. Indeed skeletal hardparts had appeared in clastic settings by Cambrian Stage 1, suggesting independence from ambient seawater chemistry where genetic and molecular mechanisms controlled biomineralization and mineralogy had become evolutionarily constrained.

Seaweed-associated microbiota experience spatial and temporal shifts in response to changing environmental conditions and seaweed physiology. These shifts may result in structural, functional and behavioral changes in the host with potential consequences for its fitness. They, thus, may help the host to adapt to changing environmental conditions. The current knowledge of seasonal variation of seaweed-associated microbiota is however still limited. In this study, we explored temporal and spatial variation of microbial communities associated with the invasive brown seaweed S. muticum. We sampled in northern and southern Portugal, in September, March and July-August (summer). In addition, as (pseudo-)perennial seaweeds display seasonal reproductive phenology, we sampled various parts of the individuals to disentangle the effect of temporal changes from those due to structural development variations. The diversity and structure of associated microbial communities were determined using next generation sequencing of the variable regions V5-7 of the 16S rDNA. We expected to find differentiation in associated microbial communities between regions and sampling months, but with differences depending on the seaweed structure examined. As expected, the study revealed substantial temporal shifts in S. muticum microbiome, for instance with large abundance of Rhodobacteraceae and Loktanella in September-March but prevalence of Pirellulales during the summer months. Variations between regions and tissues were also observed: in northern Portugal and on basal structures, bacterial diversity was higher as compared to the South and apical parts. All examined seaweed structures showed temporal differences in associated microbial community structure over time, except for holdfasts between September and March. Bacteria contributing to these changes varied spatially. Conversely to all other structures, the holdfast also did not show differences in associated community structure between southern and northern regions. Our study highlights the importance of structural microscale differentiations within seaweeds hosts with regard to their associated microbial communities and their importance across temporal and spatial dimensions.

Understanding the structure and richness of natural communities is a fundamental goal of marine ecology, and foundation species such as large macroalgae have a disproportionate role in structuring biodiversity. However, high-resolution information on assemblages associated with macroalgae is lacking for many species and regions. Saccorhiza polyschides is a warm-temperate kelp with a relatively short lifespan (12–18 months), large thallus and bulbous holdfast offering habitat for diverse assemblages. In the UK, S. polyschides populations are thought to have proliferated recently. Here, we quantified the density and habitat structure provided by S. polyschides along a gradient of wave exposure within Plymouth Sound, and examined the composition and diversity of associated faunal assemblages. Density varied significantly between sites but not by wave exposure, while biometric measurements were generally highly variable. Senescing holdfasts from sporophytes offered valuable habitat, with high abundance and richness of associated assemblages, although these varied markedly between sporophytes and sites. Faunal abundance, taxon richness and diversity were significantly higher at fully exposed sites than at moderately exposed sites. Internal volume of holdfasts was positively correlated with faunal abundance and taxon richness. We recorded more than 27 distinct taxa and up to ~600 individuals within a single holdfast. Taxa included three fish species, including a novel observation of the pipefish Nerophis lumbriciformis. Further work is needed to examine seasonality in habitat structure and associated diversity patterns but our study demonstrates that even remnant holdfasts from decaying sporophytes represent a valuable microhabitat that may provide shelter, protection and food during winter.

Silicified fossils are ideal for taxonomic studies because they can be extracted without damage using acids. However, permineralization commonly introduces taphonomic biases: as silica neomorphism occurs, silicified fossils are also susceptible to loss of microstructural fidelity and diagnostic characters useful for taxonomic determination. These processes are studied in the traditional ‘lower‒middle Cambrian’ transition of the Iberian Chains, where the macrofossil content includes variable abundances of trilobites and linguliformean brachiopods. In contrast, acid etching of partly silicified limestone interbeds offers a quite different biodiversity pattern, dominated by trilobite larvae, chancelloriids and sponge spicules, accompanied by locally abundant calcite- and phosphate-walled brachiopods, echinoderm holdfasts, and psammosphaerids and serpulids encrusting disarticulated sclerites. Petrographic, geochemical (chondrite-normalized REE, gull-wing patterns), cathodoluminescence (prominent yellow emission bands between 560 and 580 nm, and weaker blue bands between 440 and 500 nm) and Raman spectral data (main peak at 465.2 cm −1 and secondary ones at 205.5 and 128.1 cm −1 ) yielded by silicified microfossils reveal that quartz precipitation was induced by a distinct episode of acidic hydrothermal activity, close to 100 °C. The event is linked to a broadly penecontemporaneous tectonic breakdown event, where fissures served as conduits for silica fluids.

Comparing divergence in quantitative traits and neutral molecular markers, such as Q ST–F ST comparisons, provides a means to distinguish between natural selection and genetic drift as causes of population differentiation in complex polygenic traits. Onithochiton neglectus (Rochebrune, 1881) is a morphologically variable chiton endemic to New Zealand, with populations distributed over a broad latitudinal environmental gradient. In this species, the morphological variants cluster into 2 geographically separated shell shape groups, and the phenotypic variation in shell shape has been hypothesized to be adaptive. Here, we assessed this hypothesis by comparing neutral genomic differentiation between populations (F ST) with an index of phenotypic differentiation (P ST). We used 7,562 putatively neutral single-nucleotide polymorphisms (SNPs) across 15 populations and 3 clades of O. neglectus throughout New Zealand to infer F ST. P ST was calculated from 18 shell shape traits and gave highly variable estimates across populations, clades, and shape groups. By systematically comparing P ST with F ST, we identified evidence of local adaptation in a number of the O. neglectus shell shape traits. This supports the hypothesis that shell shape could be an adaptive trait, potentially correlated with the ability to live and raft in kelp holdfasts.