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1.
Ecology ; : e4434, 2024 Oct 01.
Article in English | MEDLINE | ID: mdl-39354801

ABSTRACT

Topographic heterogeneity sets the stage for community assembly, but its effects on ecosystem functioning remain poorly understood. Here, we test the hypothesis that topographic heterogeneity underpins multiple cascading species interactions and functional pathways that indirectly control multifunctionality. To do so, we combined experimental manipulation of a form of topographic heterogeneity on rocky shores (holes of various sizes) with a comprehensive assessment of naturally assembled communities and multifunctionality. Structural equation modeling indicated that heterogeneity: (1) enhanced biodiversity by supporting filter feeder richness; (2) triggered a facilitation cascade via reef-forming (polychaete) and biomass-dominant (macroalga) foundation species, which in turn broadly supported functionally diverse epibiotic and understory assemblages; and (3) inhibited a key consumer (limpet). The model supported that these mechanisms exerted complementary positive effects on individual functions (e.g., water filtration, ecosystem metabolism, nutrient uptake) and, in turn, collectively enhanced multifunctionality. Topographic heterogeneity may therefore serve as a cornerstone physical attribute by initiating multiple cascades that propagate through ecological communities via foundation species, ultimately manifesting disproportionate effects on ecosystem multifunctionality.

2.
Article in English | MEDLINE | ID: mdl-39300809

ABSTRACT

Rhodolith beds are diverse and globally distributed habitats. Nonetheless, the role of rhodoliths in structuring the associated species community through a hierarchy of positive interactions is yet to be recognised. In this review, we provide evidence that rhodoliths can function as foundation species of multi-level facilitation cascades and, hence, are fundamental for the persistence of hierarchically structured communities within coastal oceans. Rhodoliths generate facilitation cascades by buffering physical stress, reducing consumer pressure and enhancing resource availability. Due to large variations in their shape, size and density, a single rhodolith bed can support multiple taxonomically distant and architecturally distinct habitat-forming species, such as primary producers, sponges or bivalves, thus encompassing a broad range of functional traits and providing a wealth of secondary microhabitat and food resources. In addition, rhodoliths are often mobile, and thus can redistribute associated species, potentially expanding the distribution of species with short-distance dispersal abilities. Key knowledge gaps we have identified include: the experimental assessment of the role of rhodoliths as basal facilitators; the length and temporal stability of facilitation cascades; variations in species interactions within cascades across environmental gradients; and the role of rhodolith beds as climate refugia. Addressing these research priorities will allow the development of evidence-based policy decisions and elevate rhodolith beds within marine conservation strategies.

3.
Mar Environ Res ; 202: 106738, 2024 Sep 04.
Article in English | MEDLINE | ID: mdl-39265327

ABSTRACT

Seismic activity, erosion, sedimentation, and extreme temperatures can cause compounding large-scale disturbances to marine organisms, like large intertidal foundational seaweeds. In November 2016, a 7.8 Mw earthquake uplifted 130 km of coastline by 0.5-6 m near Kaikoura, New Zealand and thereby increased intertidal desiccation, aerial temperatures, reef erosion, and water turbidity. Furthermore, stress on uplifted intertidal species was compounded by unprecedented marine heatwaves over the summer of 2017/18. Here we documented altered dominances of large foundational seaweed and possible flow-on effects on seaweed-associated flora and fauna, following the uplift and heatwaves. These compounding disturbances caused instant high canopy loss of the dominant primary foundation species - the large perennial canopy-forming southern bull kelp Durvillaea antarctica - and no post-disturbance recovery, suggesting a maintenance threshold has been exceeded. After canopy loss of the primary foundation species, alternative foundation species - i.e., subordinate competitors under pre-disturbance conditions (the perennial canopy-forming fucoids Carpophyllum maschalocarpum, Cystophora scalaris, and Hormosira banksii) increased in abundance. Furthermore, field observations of attachment interaction networks demonstrated that the primary and alternative foundation species facilitated different sessile and mobile taxa. For example, the smaller and more morphologically complex C. maschalocarpum, H. banksii, and C. scalaris, supported more novel attachment associations, whereas the larger Durvillaea supported longer attachment chains. Overall, our results highlight abrupt and potentially long-lasting ecological changes after compounding disturbances, which altered dominance hierarchies. Alternative foundation species are now more common than the pre-disturbance primary foundation species, with flow-on effects on wider communities that depend on biogenic habitats.

4.
Glob Chang Biol ; 30(8): e17469, 2024 Aug.
Article in English | MEDLINE | ID: mdl-39155748

ABSTRACT

Marine heatwaves (MHWs), increasing in duration and intensity because of climate change, are now a major threat to marine life and can have lasting effects on the structure and function of ecosystems. However, the responses of marine taxa and ecosystems to MHWs can be highly variable, making predicting and interpreting biological outcomes a challenge. Here, we review how biological responses to MHWs, from individuals to ecosystems, are mediated by fine-scale spatial variability in the coastal marine environment (hereafter, local gradients). Viewing observed responses through a lens of ecological theory, we present a simple framework of three 'resilience processes' (RPs) by which local gradients can influence the responses of marine taxa to MHWs. Local gradients (1) influence the amount of stress directly experienced by individuals, (2) facilitate local adaptation and acclimatization of individuals and populations, and (3) shape community composition which then influences responses to MHWs. We then synthesize known examples of fine-scale gradients that have affected responses of benthic foundation species to MHWs, including kelp forests, coral reefs, and seagrass meadows and link these varying responses to the RPs. We present a series of case studies from various marine ecosystems to illustrate the differential impacts of MHWs mediated by gradients in both temperature and other co-occurring drivers. In many cases, these gradients had large effect sizes with several examples of local gradients causing a 10-fold difference in impacts or more (e.g., survival, coverage). This review highlights the need for high-resolution environmental data to accurately predict and manage the consequences of MHWs in the context of ongoing climate change. While current tools may capture some of these gradients already, we advocate for enhanced monitoring and finer scale integration of local environmental heterogeneity into climate models. This will be essential for developing effective conservation strategies and mitigating future marine biodiversity loss.


Subject(s)
Climate Change , Ecosystem , Aquatic Organisms/physiology , Coral Reefs , Animals , Hot Temperature , Acclimatization
5.
Ecol Evol ; 14(8): e70109, 2024 Aug.
Article in English | MEDLINE | ID: mdl-39130096

ABSTRACT

Branching stipe morphologies have evolved multiple times across the kelp (Laminariales) lineage, creating morphological forms that drive the complexity of kelp forest habitats. Although branching is likely a complicated developmental process, it has evolved repeatedly through kelp evolution and the processes facilitating the emergence of branched forms from unbranched ancestors remain unclear. Here I report on abnormally branched individuals (n = 9) from five kelp species found in British Columbia, Canada that had atypical bifurcations in their stipes, creating a single dichotomous branch. One of these species generally lacks branching entirely (Laminaria ephemera) while the other four exhibit some branching but typically lack this stipe bifurcation (Alaria marginata, Laminaria setchellii, Nereocystis luetkeana, Pterygophora californica). These unusually branched individuals exhibited replicated morphological subunits distal to the stipe bifurcation, including more blades, pneumatocysts, and sporophylls than is typical. This suggests that unbranched species possess an inherent developmental capacity for modularity with autonomy in the development of individual modules that may have helped to facilitate the widespread emergence of branched morphologies. Given the role of kelp forests in coastal environments, branching may influence habitat characteristics, potentially influencing community dynamics, and is thus a trait of particular evolutionary interest. These findings highlight the need for experiments that manipulate kelp development to better characterise the ontogenetic processes of these globally important taxa.

6.
PeerJ ; 12: e17697, 2024.
Article in English | MEDLINE | ID: mdl-38993978

ABSTRACT

Rocky intertidal habitats occur worldwide and are mainly characterized by primary space holders such as seaweeds and sessile invertebrates. Some of these organisms are foundation species, as they can form structurally complex stands that host many small invertebrates. The abundance of primary space holders is known to vary along coastlines driven directly or indirectly by environmental variation. However, it is less clear if the invertebrate assemblages associated to a foundation species may remain relatively unchanged along coastlines, as similar stands of a foundation species can generate similar microclimates. We examined this question using abundance data for invertebrate species found in mussel stands of a similar structure in wave-exposed rocky habitats at mid-intertidal elevations along the Atlantic coast of Nova Scotia (Canada). While the most abundant invertebrate species were found at three locations spanning 315 km of coastline, species composition (a combined measure of species identity and their relative abundance) differed significantly among the locations. One of the species explaining the highest amount of variation among locations (a barnacle) exhibited potential signs of bottom-up regulation involving pelagic food supply, suggesting benthic-pelagic coupling. The abundance of the species that explained the highest amount of variation (an oligochaete) was positively related to the abundance of their predators (mites), further suggesting bottom-up forcing in these communities. Overall, we conclude that species assemblages associated to structurally similar stands of a foundation species can show clear changes in species composition at a regional scale.


Subject(s)
Bivalvia , Ecosystem , Invertebrates , Animals , Nova Scotia , Invertebrates/physiology , Bivalvia/physiology , Biodiversity
7.
Environ Sci Pollut Res Int ; 31(34): 47116-47131, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38985418

ABSTRACT

Mining is a major economic activity in many developing countries. However, it disturbs the environment, producing enormous quantities of waste, known as mine tailings, which can have deleterious environmental impact, due to their high heavy metals (HM) content. Often, foundation species that establish on mine tailings are good candidates to study the effects of HM bioaccumulation at different levels of biological organization. Prosopis laevigata is considered a HM hyperaccumulator which presents attributes of a foundation species (FS) and establishes naturally on mine tailings. We evaluated the bioaccumulation of Cu, Pb, and Zn in P. laevigata foliar tissue, the leaf micro- and macro-morphological characters, DNA damage, and population genetic effects. In total, 80 P. laevigata individuals (20/site) belonging to four populations: The individuals from both sites (exposed and reference) bioaccumulated HMs (Pb > Cu > Zn). However, in the exposed individuals, Pb and Cu bioaccumulation was significantly higher. Also, a significant effect of macro- and micro-morphological characters was registered, showing significantly lower values in individuals from the exposed sites. In addition, we found significant differences in genotoxic damage in P. laevigata individuals, between the exposed and reference sites. In contrast, for the micro-morphological characters, none of the analyzed metals had any influence. P. laevigata did not show significant differences in the genetic structure and diversity between exposed and reference populations. However, four haplotypes and four private alleles were found in the exposed populations. Since P. laevigata is a species that establishes naturally in polluted sites and bioaccumulates HM in its foliar tissues, the resulting genetic, individual and population effects have not been severe enough to show detrimental effects; hence, P. laevigata can be a useful tool in phytoremediation strategies for soils polluted with Pb and Cu, maintaining its important ecological functions.


Subject(s)
Bioaccumulation , Metals, Heavy , Prosopis , Soil Pollutants , Metals, Heavy/metabolism , Prosopis/metabolism , Soil Pollutants/metabolism , Biomarkers/metabolism , Mining , Environmental Monitoring/methods
8.
J Environ Manage ; 366: 121887, 2024 Aug.
Article in English | MEDLINE | ID: mdl-39025015

ABSTRACT

The seabed desertification has increasingly highlighted the importance of benthic habitat restoration. Strategically engineered artificial reefs emerges as pivotal in achieving restoration objectives. However, the significant influence of foundation species on biotic components and ecosystem attributes within diverse artificial reefs has been underrecognized. This study collated twenty Ecopath models of artificial reefs and their corresponding natural control ecosystems along the coasts of the Yellow Sea and Bohai Sea, China, categorizing them into five distinct system types predicated on the biomass and productivity of foundational species. Our results suggest that dimensionless indices, rather than actual system values, were posited to facilitate inter-comparative analysis. The comparative analysis revealed differences in biomass distribution, energy utilization, and trophic structure across the five ecosystem types. All the artificial reef systems collectively enhanced the utilization of primary production. Foundation species components formed the cornerstone of system functionality, significantly impacting ecosystem stability through modulation of energy flow dynamics. Distinct impacts were observed from shellfish and macroalgae; the former augmenting the detrital food chain, while the latter bolstering the grazing food chain. Consequently, the model-based integrated analysis enabled a robust comparison among various types of artificial reef ecosystems and confirmed that promoting the colonization of foundation species was a non-negligible factor in the design and deployment of artificial reefs.


Subject(s)
Biomass , Coral Reefs , Ecosystem , Conservation of Natural Resources , China , Animals , Food Chain , Models, Theoretical
9.
Sci Total Environ ; 942: 173784, 2024 Sep 10.
Article in English | MEDLINE | ID: mdl-38851330

ABSTRACT

Forest foundation species, vital for shaping community structure and dynamics through non-trophic level interactions, are key to forest succession and sustainability. Despite their ecological importance, the habitat ranges of these species in China and their responses to future climate change remain unclear. Our study employed the optimal MaxEnt model to assess the range shifts and their essential drivers of four typical forest foundation species from three climatic zones in China under climate scenarios, including Acer tegmentosum, Acer pseudo-sieboldianum (temperate zone), Quercus glandulifera (subtropical zone), and Ficus hispida (tropical zone). The optimal MaxEnt model exhibited high evaluation indices (AUC values > 0.90) for the four foundation species, indicating excellent predictive performance. Currently, we observed that A. tegmentosum and A. pseudo-sieboldianum are predominantly inhabited temperate forest areas in northeastern China, Q. glandulifera is primarily concentrated in subtropical forests in southeastern China, and F. hispida is mainly distributed across the tropical forests in southern China. Climate factors, particularly temperature, emerged as the primary environmental factors influencing the potential range of forest foundation species. Moreover, precipitation strongly influenced the potential range of A. tegmentosum and A. pseudo-sieboldianum, while elevation exhibited a greater impact on the range of Q. glandulifera and F. hispida. Under future climate scenarios, suitable areas for A. tegmentosum and A. pseudo-sieboldianum tend to expand southward, F. hispida tends to expand northward, while Q. glandulifera exhibited a tendency to contract towards the center. This study advances our understanding of the spatial and temporal dynamics of forest foundation species in China under climate change, providing critical insights for conservation efforts and sustainable forest management practices.


Subject(s)
Climate Change , Forests , Quercus , China , Acer , Ecosystem , Ficus , Trees
10.
Front Microbiol ; 15: 1310374, 2024.
Article in English | MEDLINE | ID: mdl-38628870

ABSTRACT

Eutrophication due to nutrient addition can result in major alterations in aquatic ecosystem productivity. Foundation species, individually and interactively, whether present as invasive species or as instruments of ecosystem management and restoration, can have unwanted effects like stabilizing turbid eutrophic states. In this study, we used whole-pond experimental manipulations to investigate the impacts of disturbance by nutrient additions in the presence and absence of two foundation species: Dreissena polymorpha (a freshwater mussel) and Myriophyllum spicatum (a macrophyte). We tracked how nutrient additions to ponds changed the prokaryotic and eukaryotic communities, using 16S, 18S, and COI amplicon sequencing. The nutrient disturbance and foundation species imposed strong selection on the prokaryotic communities, but not on the microbial eukaryotic communities. The prokaryotic communities changed increasingly over time as the nutrient disturbance intensified. Post-disturbance, the foundation species stabilized the prokaryotic communities as observed by the reduced rate of change in community composition. Our analysis suggests that prokaryotic community change contributed both directly and indirectly to major changes in ecosystem properties, including pH and dissolved oxygen. Our work shows that nutrient disturbance and foundation species strongly affect the prokaryotic community composition and stability, and that the presence of foundation species can, in some cases, promote the emergence and persistence of a turbid eutrophic ecosystem state.

11.
Sci Rep ; 14(1): 8958, 2024 04 18.
Article in English | MEDLINE | ID: mdl-38637667

ABSTRACT

Dominant vegetation in many ecosystems is an integral component of structure and habitat. In many drylands, native shrubs function as foundation species that benefit other plants and animals. However, invasive exotic plant species can comprise a significant proportion of the vegetation. In Central California drylands, the facilitative shrub Ephedra californica and the invasive Bromus rubens are widely dispersed and common. Using comprehensive survey data structured by shrub and open gaps for the region, we compared network structure with and without this native shrub canopy and with and without the invasive brome. The presence of the invasive brome profoundly shifted the network measure of centrality in the microsites structured by a shrub canopy (centrality scores increased from 4.3 under shrubs without brome to 6.3, i.e. a relative increase of 42%). This strongly suggests that plant species such as brome can undermine the positive and stabilizing effects of native foundation plant species provided by shrubs in drylands by changing the frequency that the remaining species connect to one another. The net proportion of positive and negative associations was consistent across all microsites (approximately 50% with a total of 14% non-random co-occurrences on average) suggesting that these plant-plant networks are rewired but not more negative. Maintaining resilience in biodiversity thus needs to capitalize on protecting native shrubs whilst also controlling invasive grass species particularly when associated with shrubs.


Subject(s)
Bromus , Ecosystem , Plants , Biodiversity , Introduced Species , California
12.
Ecol Appl ; 34(4): e2968, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38562000

ABSTRACT

Understanding how habitat attributes (e.g., patch area and sizes, connectivity) control recruitment and how this is modified by processes operating at larger spatial scales is fundamental to understanding population sustainability and developing successful long-term restoration strategies for marine foundation species-including for globally threatened reef-forming oysters. In two experiments, we assessed the recruitment and energy reserves of oyster recruits onto remnant reefs of the oyster Saccostrea glomerata in estuaries spanning 550 km of coastline in southeastern Australia. In the first experiment, we determined whether recruitment of oysters to settlement plates in three estuaries was correlated with reef attributes within patches (distances to patch edges and surface elevation), whole-patch attributes (shape and size of patches), and landscape attributes (connectivity). We also determined whether environmental factors (e.g., sedimentation and water temperature) explained the differences among recruitment plates. We also tested whether differences in energy reserves of recruits could explain the differences between two of the estuaries (one high- and one low-sedimentation estuary). In the second experiment, across six estuaries (three with nominally high and three with nominally low sedimentation rates), we tested the hypothesis that, at the estuary scale, recruitment and survival were negatively correlated to sedimentation. Overall, total oyster recruitment varied mostly at the scale of estuaries rather than with reef attributes and was negatively correlated with sedimentation. Percentage recruit survival was, however, similar among estuaries, although energy reserves and condition of recruits were lower at a high- compared to a low-sediment estuary. Within each estuary, total oyster recruitment increased with patch area and decreased with increasing tidal height. Our results showed that differences among estuaries have the largest influence on oyster recruitment and recruit health and this may be explained by environmental processes operating at the same scale. While survival was high across all estuaries, growth and reproduction of oysters on remnant reefs may be affected by sublethal effects on the health of recruits in high-sediment estuaries. Thus, restoration programs should consider lethal and sublethal effects of whole-estuary environmental processes when selecting sites and include environmental mitigation actions to maximize recruitment success.


Subject(s)
Ostreidae , Animals , Ostreidae/physiology , Endangered Species , Estuaries , Population Dynamics , Australia
13.
Mar Environ Res ; 198: 106519, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38678754

ABSTRACT

We examined spatiotemporal variability in the structure of faunal assemblages associated with the warm-temperate pseudo-kelp Saccorhiza polyschides towards its range centre (Western English Channel, southwest UK), to better understand its role as a habitat-former in the northeast Atlantic. A total of 180 sporophytes and their associated fauna were sampled across three months, three sites, and two depths. Assemblage abundance and biomass varied markedly between three morpho-functional sporophyte components (i.e., holdfast, stipe, blade). We recorded rich and abundant macroinvertebrate assemblages, comprising nine phyla, 28 coarse taxonomic groups, and 57 species of molluscs, which consistently dominated assemblages. We observed pronounced seasonality in faunal assemblage structure, marked variability between sites and depths, and strong positive relationships between biogenic habitat availability and faunal abundance/biomass. S. polyschides sporophytes are short-lived and offer temporary, less-stable habitat compared with dominant perennial Laminaria species, so shifts in the relative abundances of habitat-formers will likely alter local biodiversity patterns.


Subject(s)
Biodiversity , Ecosystem , Invertebrates , Animals , Invertebrates/physiology , Biomass , Environmental Monitoring , United Kingdom , Atlantic Ocean , Aquatic Organisms/physiology
14.
Ecol Appl ; 34(3): e2957, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38485492

ABSTRACT

Forest insect outbreaks cause large changes in ecosystem structure, composition, and function. Humans often respond to insect outbreaks by conducting salvage logging, which can amplify the immediate effects, but it is unclear whether logging will result in lasting differences in forest structure and dynamics when compared with forests affected only by insect outbreaks. We used 15 years of data from an experimental removal of Tsuga canadensis (L.) Carr. (Eastern hemlock), a foundation tree species within eastern North American forests, and contrasted the rate, magnitude, and persistence of response trajectories between girdling (emulating mortality from insect outbreak) and timber harvest treatments. Girdling and logging were equally likely to lead to large changes in forest structure and dynamics, but logging resulted in faster rates of change. Understory light increases and community composition changes were larger and more rapid in the logged plots. Tree seedling and understory vegetation abundance increased more in the girdled plots; this likely occurred because seedlings grew rapidly into the sapling- and tree-size classes after logging and quickly shaded out plants on the forest floor. Downed deadwood pools increased more after logging but standing deadwood pools increased dramatically after girdling. Understory light levels remained elevated for a longer time after girdling. Perhaps because the window of opportunity for understory species to establish was longer in the girdled plots, total species richness increased more in the girdled than logged plots. Despite the potential for greater diversity in the girdled plots, Betula lenta L. (black birch) was the most abundant tree species recruited into the sapling- and tree-size classes in both the girdled and logged plots and is poised to dominate the new forest canopy. The largest difference between the girdling and logging treatments-deadwood structure and quantity-will persist and continue to bolster aboveground carbon storage and structural and habitat diversity in the girdled plots. Human responses to insect outbreaks hasten forest reorganization and remove structural resources that may further alter forest response to ongoing climate stress and future disturbances.


Subject(s)
Ecosystem , Trees , Humans , Trees/physiology , Forests , Carbon
15.
Ann Bot ; 133(1): 117-130, 2024 Mar 08.
Article in English | MEDLINE | ID: mdl-37962600

ABSTRACT

BACKGROUND AND AIMS: Large brown macroalgae serve as foundation organisms along temperate and polar coastlines, providing a range of ecosystem services. Saccorhiza polyschides is a warm-temperate kelp-like species found in the northeast Atlantic, which is suggested to have proliferated in recent decades across the southern UK, possibly in response to increasing temperatures, physical disturbance and reduced competition. However, little is known about S. polyschides with regard to ecological functioning and population dynamics across its geographical range. Here we examined the population demography of S. polyschides populations in southwest UK, located within the species' range centre, to address a regional knowledge gap and to provide a baseline against which to detect future changes. METHODS: Intertidal surveys were conducted during spring low tides at three sites along a gradient of wave exposure in Plymouth Sound (Western English Channel) over a period of 15 months. Density, cover, age, biomass and morphology of S. polyschides were quantified. Additionally, less frequent sampling of shallow subtidal reefs was conducted to compare intertidal and subtidal populations. KEY RESULTS: We recorded pronounced seasonality, with fairly consistent demographic patterns across sites and depths. By late summer, S. polyschides was a dominant habitat-former on both intertidal and subtidal reefs, with maximum standing stock exceeding 13 000 g wet weight m-2. CONCLUSIONS: Saccorhiza polyschides is a conspicuous and abundant member of rocky reef assemblages in the region, providing complex and abundant biogenic habitat for associated organisms and high rates of primary productivity. However, its short-lived pseudo-annual life strategy is in stark contrast to dominant long-lived perennial laminarian kelps. As such, any replacement or reconfiguration of habitat-forming macroalgae due to ocean warming will probably have implications for local biodiversity and community composition. More broadly, our study demonstrates the importance of high-resolution cross-habitat surveys to generate robust baselines of kelp population demography, against which the ecological impacts of climate change and other stressors can be reliably detected.


Subject(s)
Kelp , Seaweed , Ecosystem , Kelp/physiology , Biodiversity , Demography
16.
Sci China Life Sci ; 67(4): 789-802, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38057621

ABSTRACT

Foundational cushion plants can re-organize community structures and sustain a prominent proportion of alpine biodiversity, but they are sensitive to climate change. The loss of cushion species can have broad consequences for associated biota. The potential plant community changes with the population dynamics of cushion plants remain, however, unclear. Using eight plant communities along a climatic and community successional gradient, we assessed cushion population dynamics, the underlying ecological constraints and hence associated plant community changes in alpine communities dominated by the foundational cushion plant Arenaria polytrichoides. The population dynamics of Arenaria are attributed to ecological constraints at a series of life history stages. Reproductive functions are constrained by increasing associated beneficiary plants; subsequent seedling establishment is constrained by temperature, water and light availability, extreme climate events, and interspecific competition; strong competitive exclusion may accelerate mortality and degeneration of cushion populations. Along with cushion dynamics, species composition, abundance and community structure gradually change. Once cushion plants completely degenerate, previously cushion-dominated communities shift to relatively stable communities that are overwhelmingly dominated by sedges. Climate warming may accelerate the degeneration process of A. polytrichoides. Degeneration of this foundational cushion plant will possibly induce massive changes in alpine plant communities and hence ecosystem functions in alpine ecosystems. The assessment of the population dynamics of foundation species is critical for an effective conservation of alpine biodiversity.


Subject(s)
Biodiversity , Ecosystem , Plants , Climate Change , Biota
17.
Mar Environ Res ; 194: 106310, 2024 Feb.
Article in English | MEDLINE | ID: mdl-38150788

ABSTRACT

Canopy-forming macroalgae are facing large declines due to climate change worldwide. The foundation species Gelidium corneum (Hudson) J.V. Lamouroux has shown a long-term decline in the Southeastern Bay of Biscay. We conducted an in situ experiment to investigate the combined effect of solar radiation and nutrient availability on the photosynthetic acclimation and growth of this macrophyte, and on the species richness and diversity of the assemblages that it forms. Photochemical stress in G. corneum was found to be greater at the end of the study, probably as a result of a prolonged exposure to high irradiance (PAR and UVR) and due to high temperatures during summer. We found an acclimation of G. corneum specimens to summer light and thermal conditions through dynamic/reversible photoinhibition and a decrease in photosynthetic efficiency. Nutrients may also have had a positive effect in dealing with the negative effects of these stressors. Under ongoing global climate change and projections for the future, further research will be needed to better understand the effects not only on canopy forming species but also on the whole community and thus on the functioning of the ecosystem.


Subject(s)
Edible Seaweeds , Rhodophyta , Seaweed , Ecosystem , Rhodophyta/physiology , Seaweed/physiology , Photosynthesis
18.
Ecol Evol ; 13(11): e10159, 2023 Nov.
Article in English | MEDLINE | ID: mdl-38034328

ABSTRACT

Eelgrass supports diverse benthic communities that ensure a variety of ecosystem functions. To better understand the ecological processes that shape community composition in eelgrass at local and regional scales, taxonomic and functional α- and ß-diversity were quantified for communities inhabiting five meadows in France. The extent to which environmental factors affected local and regional benthic communities was quantified by considering their direct and indirect effects (through morphological traits of eelgrass) using piecewise structural equation modeling (pSEM). Communities supported by eelgrass had higher species abundances, as well as taxonomic and functional diversity compared to nearby bare sediments. No significant differences were found between communities from the center relative to the edges of meadows, indicating that both habitats provide similar benefits to biodiversity. The presence of a few abundant species and traits suggests moderate levels of habitat filtering and close associations of certain species with eelgrass. Nevertheless, high turnover of a large number of rare species and traits was observed among meadows, resulting in meadows being characterized by their own distinct communities. High turnover indicates that much of the community is not specific to eelgrass, but rather reflects local species pools. pSEM showed that spatial variation in community composition (ß-diversity) was primarily affected by environmental conditions, with temperature, current velocity, and tidal amplitude being the most significant explanatory variables. Local richness and abundance (α-diversity) were affected by both environment and morphological traits. Importantly, morphological traits of Zostera marina were also influenced by environmental conditions, revealing cascading effects of the environment on assemblages. In sum, the environment exerted large effects on community structure at both regional and local scales, while plant traits were only pertinent in explaining local diversity. This complex interplay of processes acting at multiple scales with indirect effects should be accounted for in conservation efforts that target the protection of biodiversity.

20.
Mar Pollut Bull ; 196: 115597, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37832500

ABSTRACT

Structurally complex habitats, such as mangrove forests, allow for rich assemblages of species that benefit from the provided space, volume and substrate. Changes in habitat complexity can affect species abundance, diversity and resilience. In this study, we explored the effects of habitat complexity on food web networks in four developmental stages of mangrove forests with differing structural complexities: climax > degrading > colonizing > bare, by analyzing food web structure, stable isotopes and habitat complexity. We found that food webs became gradually more biodiverse (species richness: +119 %), complex (link density: +39 %), and robust (connectance: -35 %) in climax versus bare stages with increasing complexity of the mangrove forest (i.e., number of trees, leaf cover, and pneumatophore densities). This study shows that habitat complexity drives food web network structure in dynamic mangrove forests. We recommend restoration practitioners to use this food web network approach to quantify habitat restoration successes complementary to traditional biodiversity metrics.


Subject(s)
Ecosystem , Food Chain , Biodiversity , Wetlands , Isotopes , Forests
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