Microbial communities across strong environmental gradients in the intertidal rocky shore
Ontology highlight
ABSTRACT:
PROVIDER: PRJEB45042 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| ERR6752150_1.fastq.gz | Fastqsanger.gz | |||
| ERR6752150_2.fastq.gz | Fastqsanger.gz | |||
| ERR6752180_1.fastq.gz | Fastqsanger.gz | |||
| ERR6752180_2.fastq.gz | Fastqsanger.gz | |||
| ERR6752190_1.fastq.gz | Fastqsanger.gz |
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Project description:Functional diversity is intimately linked with community assembly processes, but its large-scale patterns of variation are often not well understood. Here, we investigated the spatiotemporal changes in multiple trait dimensions ("trait space") along vertical intertidal environmental stress gradients and across a landscape scale. We predicted that the range of the trait space covered by local assemblages (i.e., functional richness) and the dispersion in trait abundances (i.e., functional dispersion) should increase from high- to low-intertidal elevations, due to the decreasing influence of environmental filtering. The abundance of macrobenthic algae and invertebrates was estimated at four rocky shores spanning ca. 200 km of the coast over a 36-month period. Functional richness and dispersion were contrasted against matrix-swap models to remove any confounding effect of species richness on functional diversity. Random-slope models showed that functional richness and dispersion significantly increased from high- to low-intertidal heights, demonstrating that under harsh environmental conditions, the assemblages comprised similar abundances of functionally similar species (i.e., trait convergence), while that under milder conditions, the assemblages encompassed differing abundances of functionally dissimilar species (i.e., trait divergence). According to the Akaike information criteria, the relationship between local environmental stress and functional richness was persistent across sites and sampling times, while functional dispersion varied significantly. Environmental filtering therefore has persistent effects on the range of trait space covered by these assemblages, but context-dependent effects on the abundances of trait combinations within such range. Our results further suggest that natural and/or anthropogenic factors might have significant effects on the relative abundance of functional traits, despite that no trait addition or extinction is detected.
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Project description:Intertidal rocky shores are the most accessible marine habitats and therefore heavily impacted by harvesting. In recent years, they have also been increasingly invaded by alien species, which compounds the effects of harvesting on rocky shore community composition and functioning. Recent survey data, combined with historical data from 1970, were used to assess temporal changes over the intervening period in rocky shore communities at two sites (Wireless Point and Wireless Island). Three kinds of changes emerged: (1) the appearance of alien species; (2) the effects of increased harvesting pressure; and (3) the direct and indirect effects of these changes on other species. A striking result was transformation of mid-shore zones on exposed shores by the appearance of the invasive Mediterranean mussel Mytilus galloprovincialis, and the indirect effects of this on the demography and vertical zonation patterns of the granular limpet Scutellastra granularis. Adult limpets have become excluded by the mussel, whereas juveniles find a secondary home on the shells of the mussel and their abundance has increased. To further disentangle the effects of harvesting from those of alien invasions, a spatial comparison was made between two currently unharvested no-take sites (Scarborough South and Scarborough North) and two regularly harvested sites (Kommetjie and Wireless Point). Harvesting has substantially depleted the granite limpet Cymbula granatina and Argenville's limpet Scutellastra argenvillei. This has led to the proliferation of opportunistic seaweeds, such as Ulva spp. The dual effects of alien invasive species and over-harvesting have major ecosystem effects but do not necessarily diminish biodiversity because the alternative habitats that have developed provide opportunities for colonisation by additional species.
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Project description:In marine ecosystems, most invertebrates possess diverse microbiomes on their external surfaces, such as those found in the pedal mucus of grazing gastropods and chitons that aids displacement on different surfaces. The microbes are then transported around and placed in contact with free-living microbial communities of micro and other macro-organisms, potentially exchanging species and homogenizing microbial composition and structure among grazer hosts. Here, we characterize the microbiota of the pedal mucus of five distantly related mollusk grazers, quantify differences in microbial community structure, mucus protein and carbohydrate content, and, through a simple laboratory experiment, assess their effects on integrated measures of biofilm abundance. Over 665 Amplicon Sequence Variants (ASVs) were found across grazers, with significant differences in abundance and composition among grazer species and epilithic biofilms. The pulmonate limpet Siphonaria lessonii and the periwinkle Echinolittorina peruviana shared similar microbiota. The microbiota of the chiton Chiton granosus, keyhole limpet Fissurella crassa, and scurrinid limpet Scurria araucana differed markedly from one another, and form those of the pulmonate limpet and periwinkle. Flavobacteriaceae (Bacteroidia) and Colwelliaceae (Gammaproteobacteria) were the most common among microbial taxa. Microbial strict specialists were found in only one grazer species. The pedal mucus pH was similar among grazers, but carbohydrate and protein concentrations differed significantly. Yet, differences in mucus composition were not reflected in microbial community structure. Only the pedal mucus of F. crassa and S. lessonii negatively affected the abundance of photosynthetic microorganisms in the biofilm, demonstrating the specificity of the pedal mucus effects on biofilm communities. Thus, the pedal mucus microbiota are distinct among grazer hosts and can affect and interact non-trophically with the epilithic biofilms on which grazers feed, potentially leading to microbial community coalescence mediated by grazer movement. Further studies are needed to unravel the myriad of non-trophic interactions and their reciprocal impacts between macro- and microbial communities.
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Project description:In open ecological systems, community structure can be determined by physically modulated processes such as the arrival of individuals from a regional pool and by local biological interactions. There is debate centering on whether niche differentiation and local interactions among species are necessary to explain macroscopic community patterns or whether the patterns can be generated by the neutral interplay of dispersal and stochastic demography among ecologically identical species. Here we evaluate how much of the observed spatial variation within a rocky intertidal metacommunity along 800 km of coastline can be explained by drift in the structure of recruits across 15 local sites. Our results show that large spatial changes in recruitment do not explain the observed spatial variation in adult local structure and that, in comparison with the large drift in structure of recruits, local adult communities converged to a common, although not unique, structure across the region. Although there is no unique adult community structure in the entire region, the observed variation represents only a small subset of the possible structures that would be expected from passive recruitment drift. Thus, in this diverse system our results do not support the idea that rocky intertidal metacommunities are structured by neutral mechanisms.
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Project description:Environmental fluctuations can generate asynchronous species' fluctuations and community stability, due to compensatory dynamics of species with different environmental tolerances. We tested this hypothesis in intertidal hard-bottom communities of north-central Chile, where a persistent upwelling centre maintains a mosaic in sea surface temperatures (SST) over 10s of kilometres along the shore. Coastal upwelling implies colder and temporally more stable SST relative to downstream sites. Uni- and multivariate analyses of multiyear timeseries of SST and species abundances showed more asynchronous fluctuations and higher stability in sites characterised by warmer and more variable SST. Nevertheless, these effects were weakened after including data obtained in sites affected by less persistent upwelling centres. Further, dominant species were more stable in sites exposed to high SST variability. The strength of other processes that can influence community stability, chiefly statistical averaging and overyielding, did not vary significantly between SST regimes. Our results provide observational evidence supporting the idea that exogenously driven compensatory dynamics and the stabilising effects of dominant species can determine the stability of ecosystems facing environmental fluctuations.
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Project description:The ecological consequences of human-driven overexploitation and loss of keystone consumers are still unclear. In intertidal rocky shores over the world, the decrease of keystone macrograzers has resulted in an increase in the dominance of herbivores with smaller body (i.e., "mesograzers"), which could potentially alter community assembly and structure. Here, we experimentally tested whether mesograzers affect the structure of rocky intertidal communities during the period of early colonization after the occurrence of a disturbance. A manipulative field experiment was conducted to exclude mesograzers (i.e., juvenile chitons, small snails, amphipods, and juvenile limpets) from experimental areas in an ecosystem characterized by the overexploitation of keystone macrograzers and predators. The results of multivariate analyses suggest that mesograzers had significant effects on intertidal community structure through negative and positive effects on species abundances. Mesograzers had negative effects on filamentous algae, but positive effects on opportunistic foliose algae and barnacles. Probably, mesograzers indirectly favored the colonization of barnacles and foliose algae by removing preemptive competitors, as previously shown for other meso- and macrograzer species. These results strongly support the idea that small herbivores exert a firm controlling effect on the assembly process of natural communities. Therefore, changes in functional roles of top-down controllers might have significant implications for the structure of intertidal communities.
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Project description:We investigate the extent to which functional structure and spatial variability of intertidal communities coincide with major biogeographical boundaries, areas where extensive compositional changes in the biota are observed over a limited geographic extension. We then investigate whether spatial variation in the biomass of functional groups, over geographic (10's km) and local (10's m) scales, could be associated to species diversity within and among these groups. Functional community structure expressed as abundance (density, cover and biomass) and composition of major functional groups was quantified through field surveys at 20 rocky intertidal shores spanning six degrees of latitude along the southwest Atlantic coast of Argentina and extending across the boundaries between the Argentinean and Magellanic Provinces. Patterns of abundance of individual functional groups were not uniformly matched with biogeographical regions. Only ephemeral algae showed an abrupt geographical discontinuity coincident with changes in biogeographic boundaries, and this was limited to the mid intertidal zone. We identified 3-4 main 'groups' of sites in terms of the total and relative abundance of the major functional groups, but these did not coincide with biogeographical boundaries, nor did they follow latitudinal arrangement. Thus, processes that determine the functional structure of these intertidal communities are insensitive to biogeographical boundaries. Over both geographical and local spatial scales, and for most functional groups and tidal levels, increases in species richness within the functional group was significantly associated to increased total biomass and reduced spatial variability of the group. These results suggest that species belonging to the same functional group are sufficiently uncorrelated over space (i.e. metres and site-to-site ) to stabilize patterns of biomass variability and, in this manner, provide a buffer, or "insurance", against spatial variability in environmental conditions.
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Project description:Biodiversity loss is driven by interacting factors operating at different spatial scales. Yet, there remains uncertainty as to how fine-scale environmental conditions mediate biological responses to broad-scale stressors. We surveyed intertidal rocky shore kelp beds situated across a local gradient of wave action and evaluated changes in kelp diversity and abundance after more than two decades of broad scale stressors, most notably the 2013-2016 heat wave. Across all sites, species were less abundant on average in 2017 and 2018 than during 1993-1995 but changes in kelp diversity were dependent on wave exposure, with wave exposed habitats remaining stable and wave sheltered habitats experiencing near complete losses of kelp diversity. In this way, wave exposed sites have acted as refugia, maintaining regional kelp diversity despite widespread local declines. Fucoids, seagrasses and two stress-tolerant kelp species (Saccharina sessilis, Egregia menziesii) did not decline as observed in other kelps, and the invasive species Sargassum muticum increased significantly at wave sheltered sites. Long-term monitoring data from a centrally-located moderate site suggest that kelp communities were negatively impacted by the recent heatwave which may have driven observed losses throughout the region. Wave-sheltered shores, which saw the largest declines, are a very common habitat type in the Northeast Pacific and may be especially sensitive to losses in kelp diversity and abundance, with potential consequences for coastal productivity. Our findings highlight the importance of fine-scale environmental heterogeneity in mediating biological responses and demonstrate how incorporating differences between habitat patches can be essential to capturing scale-dependent biodiversity loss across the landscape.
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