Changes in disturbance regimes due to climate change are increasingly challenging the capacity of ecosystems to absorb recurrent shocks and reassemble afterwards, escalating the risk of widespread ...ecological collapse of current ecosystems and the emergence of novel assemblages
. In marine systems, the production of larvae and recruitment of functionally important species are fundamental processes for rebuilding depleted adult populations, maintaining resilience and avoiding regime shifts in the face of rising environmental pressures
. Here we document a regional-scale shift in stock-recruitment relationships of corals along the Great Barrier Reef-the world's largest coral reef system-following unprecedented back-to-back mass bleaching events caused by global warming. As a consequence of mass mortality of adult brood stock in 2016 and 2017 owing to heat stress
, the amount of larval recruitment declined in 2018 by 89% compared to historical levels. For the first time, brooding pocilloporids replaced spawning acroporids as the dominant taxon in the depleted recruitment pool. The collapse in stock-recruitment relationships indicates that the low resistance of adult brood stocks to repeated episodes of coral bleaching is inexorably tied to an impaired capacity for recovery, which highlights the multifaceted processes that underlie the global decline of coral reefs. The extent to which the Great Barrier Reef will be able to recover from the collapse in stock-recruitment relationships remains uncertain, given the projected increased frequency of extreme climate events over the next two decades
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Understanding life history and demographic variation among species within communities is a central ecological goal. Mortality schedules are especially important in ecosystems where disturbance plays ...a major role in structuring communities, such as coral reefs. Here, we test whether a trait‐based, mechanistic model of mechanical vulnerability in corals can explain mortality schedules. Specifically, we ask whether species that become increasingly vulnerable to hydrodynamic dislodgment as they grow have bathtub‐shaped mortality curves, whereas species that remain mechanically stable have decreasing mortality rates with size, as predicted by classical life history theory for reef corals. We find that size‐dependent mortality is highly consistent between species with the same growth form and that the shape of size‐dependent mortality for each growth form can be explained by mechanical vulnerability. Our findings highlight the feasibility of predicting assemblage‐scale mortality patterns on coral reefs with trait‐based approaches.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Quantifying changes in functional community structure driven by disturbance is critical to anticipate potential shifts in ecosystem functioning. However, how marine heatwaves (MHWs) affect the ...functional structure of temperate coral‐dominated communities is poorly understood. Here, we used five long‐term (> 10 years) records of Mediterranean coralligenous assemblages in a multi‐taxa, trait‐based analysis to investigate MHW‐driven changes in functional structure. We show that, despite stability in functional richness (i.e. the range of species functional traits), MHW‐impacted assemblages experienced long‐term directional changes in functional identity (i.e. their dominant trait values). Declining traits included large sizes, long lifespans, arborescent morphologies, filter‐feeding strategies or calcified skeletons. These traits, which were mostly supported by few sensitive and irreplaceable species from a single functional group (habitat‐forming octocorals), disproportionally influence certain ecosystem functions (e.g. 3D‐habitat provision). Hence, MHWs are leading to assemblages that are deficient in key functional traits, with likely consequences for the ecosystem functioning.
Marine heatwaves (MHWs) are altering the structure of temperate coral‐dominated communities worlwide. Yet, the long‐term consequences for ecosystem functioning remain mostly uknown. Here, we quantified changes in functional structure of Mediterranean coralligenous assemblages by conducting a mulit‐taxa, trait‐based analysis. Our results show that MHWs are leading to assemblages that are deficient in key functional traits, with likely consequences for the ecosystem functioning.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Two facets of climate change--increased tropical storm intensity and ocean acidification--are expected to detrimentally affect reef-building organisms by increasing their mortality rates and ...decreasing their calcification rates. Our current understanding of these effects is largely based on individual organisms' short-term responses to experimental manipulations. However, predicting the ecologically-relevant effects of climate change requires understanding the long-term demographic implications of these organism-level responses. In this study, we investigate how storm intensity and calcification rate interact to affect population dynamics of the table coral Acropora hyacinthus, a dominant and geographically widespread ecosystem engineer on wave-exposed Indo-Pacific reefs. We develop a mechanistic framework based on the responses of individual-level demographic rates to changes in the physical and chemical environment, using a size-structured population model that enables us to rigorously incorporate uncertainty. We find that table coral populations are vulnerable to future collapse, placing in jeopardy many other reef organisms that are dependent upon them for shelter and food. Resistance to collapse is largely insensitive to predicted changes in storm intensity, but is highly dependent on the extent to which calcification influences both the mechanical properties of reef substrate and the colony-level trade-off between growth rate and skeletal strength. This study provides the first rigorous quantitative accounting of the demographic implications of the effects of ocean acidification and changes in storm intensity, and provides a template for further studies of climate-induced shifts in ecosystems, including coral reefs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Novel communities are a risky business Dornelas, Maria; Madin, Joshua S.
Science (American Association for the Advancement of Science),
10/2020, Volume:
370, Issue:
6513
Journal Article
Peer reviewed
High turnover leads to novel combinations of species and involves high extinction
As in business, most action in biodiversity happens in turnover. Net changes in balance give us some indication of ...performance. However, knowing the volumes of income and payments that make up that balance conveys much more information about how a business is operating. The same is true of ecological communities: Knowing net changes in the number of species is useful, but the gains and losses of species encapsulated in turnover hold essential information about biodiversity change. High turnover is emerging as the signature of biodiversity patterns in the Anthropocene (
1
–
3
), raising questions as to the causes and consequences of high turnover in biodiversity. On page 220 of this issue, Pandolfi
et al.
(
4
) look into the deeper past to identify when turnover is so increased that it results in completely new combinations of species, known as novel communities.
Coral reefs are biologically diverse and ecologically complex ecosystems constructed by stony corals. Despite decades of research, basic coral population biology and community ecology questions ...remain. Quantifying trait variation among species can help resolve these questions, but progress has been hampered by a paucity of trait data for the many, often rare, species and by a reliance on nonquantitative approaches. Therefore, we propose filling data gaps by prioritizing traits that are easy to measure, estimating key traits for species with missing data, and identifying ‘supertraits’ that capture a large amount of variation for a range of biological and ecological processes. Such an approach can accelerate our understanding of coral ecology and our ability to protect critically threatened global ecosystems.
Characterizing trait variation between species helps quantify fundamental biological, ecological, and evolutionary processes.
Hampered by a paucity of trait data, novel approaches are needed to fill data gaps by prioritizing traits that are easy to measure.
‘Supertraits’ capture a large amount of process variation. Their discovery will accelerate understanding of coral ecology and our ability to protect a critically threatened global ecosystem.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Most marine organisms disperse via ocean currents as larvae, so it is often assumed that larval-stage duration is the primary determinant of geographic range size. However, empirical tests of this ...relationship have yielded mixed results, and alternative hypotheses have rarely been considered. Here we assess the relative influence of adult and larval-traits on geographic range size using a global dataset encompassing 590 species of tropical reef fishes in 47 families, the largest compilation of such data to date for any marine group. We analyze this database using linear mixed-effect models to control for phylogeny and geographical limits on range size. Our analysis indicates that three adult traits likely to affect the capacity of new colonizers to survive and establish reproductive populations (body size, schooling behavior, and nocturnal activity) are equal or better predictors of geographic range size than pelagic larval duration. We conclude that adult life-history traits that affect the postdispersal persistence of new populations are primary determinants of successful range extension and, consequently, of geographic range size among tropical reef fishes.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
A word on habitat complexity Madin, Joshua S.; Asbury, Mollie; Schiettekatte, Nina ...
Ecology letters,
June 2023, 2023-Jun, 2023-06-00, 20230601, Volume:
26, Issue:
6
Journal Article
Peer reviewed
In their recent synopsis, Loke and Chisholm (Ecology Letters, 25, 2269–2288, 2022) present an overview of habitat complexity metrics for ecologists. They provide a review and some sound advice. ...However, we found several of their analyses and opinions misleading. This technical note provides a different perspective on the complexity metrics assessed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Rapid intensification of environmental disturbances has sparked widespread decline and compositional shifts in foundation species in ecosystems worldwide. Now, an emergent challenge is to understand ...the consequences of shifts and losses in such habitat‐forming species for associated communities and ecosystem processes. Recently, consecutive coral bleaching events shifted the morphological makeup of habitat‐forming coral assemblages on the Great Barrier Reef (GBR). Considering the disparity of coral morphological growth forms in shelter provision for reef fishes, we investigated how shifts in the morphological structure of coral assemblages affect the abundance of juvenile and adult reef fishes. We used a temporal dataset from shallow reefs in the northern GBR to estimate coral convexity (a fine‐scale quantitative morphological trait) and two widely used coral habitat descriptors (coral cover and reef rugosity) for disentangling the effects of coral morphology on reef fish assemblages. Changes in coral convexity, rather than live coral cover or reef rugosity, disproportionately affected juvenile reef fishes when compared to adults, and explained more than 20% of juvenile decline. The magnitude of this effect varied by fish body size with juveniles of small‐bodied species showing higher vulnerability to changes in coral morphology. Our findings suggest that continued large‐scale shifts in the relative abundance of morphological groups within coral assemblages are likely to affect population replenishment and dynamics of future reef fish communities. The different responses of juvenile and adult fishes according to habitat descriptors indicate that focusing on coarse‐scale metrics alone may mask fine‐scale ecological responses that are key to understand ecosystem functioning and resilience. Nonetheless, quantifying coral morphological traits may contribute to forecasting the structure of reef fish communities on novel reef ecosystems shaped by climate change.
We investigated the responses of reef fishes to changes in the morphological structure of coral assemblages following coral bleaching. Temporal changes in coral morphology were captured using a continuous fine‐scale morphological trait, coral convexity. Juvenile reef fish density declined with increased coral convexity (i.e., higher dominance of less complex coral growth forms). In particular, juveniles of small‐bodied fishes showed higher vulnerability to changes in coral morphology. Our findings suggest that linking coral morphological forms to ecosystem functions may contribute to forecasting how reef fish communities might fare under novel marine ecosystems induced by future climate change.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Understanding species differences in demographic strategies is a fundamental goal of ecology. In scleractinian corals, colony morphology is tightly linked with many demographic traits, such as ...size-specific growth and morality. Here we test how well morphology predicts the colony size-fecundity relationship in eight species of broadcast-spawning corals. Variation in colony fecundity is greater among morphologies than between species with a similar morphology, demonstrating that colony morphology can be used as a quantitative proxy for demographic strategies. Additionally, we examine the relationship between sizespecific colony fecundity and mechanical vulnerability (i.e., vulnerability to colony dislodgment). Interestingly, the relationship between size-specific fecundity and mechanical vulnerability varied among morphologies. For tabular species, the most fecund colonies are the most mechanically vulnerable, while the opposite is true for massive species. For corymbose and digitate colonies, mechanical vulnerability remains relatively constant as fecundity increases. These results reveal strong differences in the demographic tradeoffs among species of different morphologies. Using colony rhorphology as a quantitative proxy for demographic strategies can help predict coral community dynamics and responses to anthropogenic change.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
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