Rising anthropogenic CO₂ emissions are anticipated to drive change to ocean ecosystems, but a conceptualization of biological change derived from quantitative analyses is lacking. Derived from ...multiple ecosystems and latitudes, our metaanalysis of 632 published experiments quantified the direction and magnitude of ecological change resulting from ocean acidification and warming to conceptualize broadly based change. Primary production by temperate noncalcifying plankton increases with elevated temperature and CO₂, whereas tropical plankton decreases productivity because of acidification. Temperature increases consumption by and metabolic rates of herbivores, but this response does not translate into greater secondary production, which instead decreases with acidification in calcifying and noncalcifying species. This effect creates a mismatch with carnivores whose metabolic and foraging costs increase with temperature. Species diversity and abundances of tropical as well as temperate species decline with acidification, with shifts favoring novel community compositions dominated by noncalcifiers and microorganisms. Both warming and acidification instigate reduced calcification in tropical and temperate reef-building species. Acidification leads to a decline in dimethylsulfide production by ocean plankton, which as a climate gas, contributes to cloud formation and maintenance of the Earth’s heat budget. Analysis of responses in short- and long-term experiments and of studies at natural CO₂ vents reveals little evidence of acclimation to acidification or temperature changes, except for microbes. This conceptualization of change across whole communities and their trophic linkages forecast a reduction in diversity and abundances of various key species that underpin current functioning of marine ecosystems.
In recent decades, global climate change 1 has caused profound biological changes across the planet 2–6. However, there is a great disparity in the strength of evidence among different ecosystems and ...between hemispheres: changes on land have been well documented through long-term studies, but similar direct evidence for impacts of warming is virtually absent from the oceans 3, 7, where only a few studies on individual species of intertidal invertebrates, plankton, and commercially important fish in the North Atlantic and North Pacific exist. This disparity of evidence is precarious for biological conservation because of the critical role of the marine realm in regulating the Earth's environmental and ecological functions, and the associated socioeconomic well-being of humans 8. We interrogated a database of >20,000 herbarium records of macroalgae collected in Australia since the 1940s and documented changes in communities and geographical distribution limits in both the Indian and Pacific Oceans, consistent with rapid warming over the past five decades 9, 10. We show that continued warming might drive potentially hundreds of species toward and beyond the edge of the Australian continent where sustained retreat is impossible. The potential for global extinctions is profound considering the many endemic seaweeds and seaweed-dependent marine organisms in temperate Australia.
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► Modern seaweed communities have become similar to past communities at lower latitudes ► Temperate species have experienced median shifts of 0.5° to 1.9° latitude poleward ► Given future warming, up to ∼25% of species might retract toward extinction ► Impacts are consistent with observed warming in both the Indian and Pacific Oceans
Ocean acidification is considered detrimental to marine calcifiers, but mounting contradictory evidence suggests a need to revisit this concept. This systematic review and meta‐analysis aim to ...critically re‐evaluate the prevailing paradigm of negative effects of ocean acidification on calcifiers. Based on 5153 observations from 985 studies, many calcifiers (e.g., echinoderms, crustaceans, and cephalopods) are found to be tolerant to near‐future ocean acidification (pH ≈ 7.8 by the year 2100), but coccolithophores, calcifying algae, and corals appear to be sensitive. Calcifiers are generally more sensitive at the larval stage than adult stage. Over 70% of the observations in growth and calcification are non‐negative, implying the acclimation capacity of many calcifiers to ocean acidification. This capacity can be mediated by phenotypic plasticity (e.g., physiological, mineralogical, structural, and molecular adjustments), transgenerational plasticity, increased food availability, or species interactions. The results suggest that the impacts of ocean acidification on calcifiers are less deleterious than initially thought as their adaptability has been underestimated. Therefore, in the forthcoming era of ocean acidification research, it is advocated that studying how marine organisms persist is as important as studying how they perish, and that future hypotheses and experimental designs are not constrained within the paradigm of negative effects.
Marine calcifiers are widely believed to be impaired by ocean acidification, but this concept has been increasingly challenged by recent evidence. This systematic review and meta‐analysis of nearly 1000 studies reveal that many calcifiers are indeed more resistant to ocean acidification than initially thought, which can result from the positive effects of various compensatory mechanisms.
•Ecologists are predisposed to studying change, partly because of the way we define disturbance.•By broadening our recognition of disturbance, we allow the study of seemingly paradoxical situations ...where a disturbance is met by little to no change.•Such research centres on a suite of processes that change in strength to absorb the increasing effects of disturbance.•By understanding such compensatory processes and the point at which they fail we can better anticipate change such that community shifts are less surprising.
Ecologists seem predisposed to studying change because we are intuitively interested in dynamic systems, including their vulnerability to human disturbance. We contrast this disposition with the value of studying processes that work against change. Although powerful, processes that counter disturbance often go unexplored because they yield no observable community change. This stability results from compensatory processes which are initiated by disturbance; these adjust in proportion to the strength of the disturbance to prevent community change. By recognising such buffering processes, we might also learn to recognise the early warning signals of community shifts which are notoriously difficult to predict because communities often show little to no change before their tipping point is reached.
Restoration is criticized as ineffectively small scale, a smoke screen against global-scale action. Yet, large-scale solutions arise from small-scale successes, which inject social values and ...optimism needed for global investment. Human values are central to achieving socio-ecological sustainability; understanding human behavior is now arguably more important than understanding the ecological processes.
The paradigm that climate change will alter global marine biodiversity is one of the most widely accepted. Yet, its predictions remain difficult to test because laboratory systems are inadequate at ...incorporating ecological complexity, and common biodiversity metrics have varying sensitivity to detect change. Here, we test for the prevalence of global responses in biodiversity and community‐level change to future climate (acidification and warming) from studies at volcanic CO2 vents across four major global coastal ecosystems and studies in laboratory mesocosms. We detected globally replicable patterns of species replacements and community reshuffling under ocean acidification in major natural ecosystems, yet species diversity and other common biodiversity metrics were often insensitive to detect such community change, even under significant habitat loss. Where there was a lack of consistent patterns of biodiversity change, these were a function of similar numbers of studies observing negative versus positive species responses to climate stress. Laboratory studies showed weaker sensitivity to detect species replacements and community reshuffling in general. We conclude that common biodiversity metrics can be insensitive in revealing the anticipated effects of climate stress on biodiversity—even under significant biogenic habitat loss—and can mask widespread reshuffling of ecological communities in a future ocean. Although the influence of ocean acidification on community restructuring can be less evident than species loss, such changes can drive the dynamics of ecosystem stability or their functional change. Importantly, species identity matters, representing a substantial influence of future oceans.
Here, we test for global patterns in biodiversity and community structure change to future climate (ocean acidification and warming), using studies from volcanic CO2 vents across four major global coastal ecosystems and studies in laboratory mesocosms. We detected globally replicable patterns of species replacement and community reshuffling under ocean acidification, yet species diversity and other common biodiversity metrics were often insensitive to detect such community change, even under significant habitat loss. Although the influence of ocean acidification on community restructuring can be less evident than net species loss, such reshuffling can alter ecosystem stability and drive functional change.
Inflexible webs
It is clear that human activities are negatively affecting current ecosystems. Predicting how our activities will affect future systems is more challenging because it involves ...estimating the unknown. Nagelkerken
et al.
overcame some of these unknowns by constructing small versions, or mesocosms, of a marine ecosystem that included species representing all trophic levels (see the Perspective by Chown). They then exposed these systems to predicted future levels of carbon dioxide and acidification. The trophic structure was relatively resistant to acidification but not to warming. Warmed systems experienced a reorganization of trophic structure that was not rescued by functional redundancy or other stabilizing responses. Such inflexibility may be a precursor of ecosystem collapse.
Science
, this issue p.
829
; see also p.
770
Experimental marine ecosystems suggest limited resilience in the face of climate warming.
As human activities intensify, the structures of ecosystems and their food webs often reorganize. Through the study of mesocosms harboring a diverse benthic coastal community, we reveal that food web architecture can be inflexible under ocean warming and acidification and unable to compensate for the decline or proliferation of taxa. Key stabilizing processes, including functional redundancy, trophic compensation, and species substitution, were largely absent under future climate conditions. A trophic pyramid emerged in which biomass expanded at the base and top but contracted in the center. This structure may characterize a transitionary state before collapse into shortened, bottom-heavy food webs that characterize ecosystems subject to persistent abiotic stress. We show that where food web architecture lacks adjustability, the adaptive capacity of ecosystems to global change is weak and ecosystem degradation likely.
Disturbance often results in small changes in community structure, but the probability of transitioning to contrasting states increases when multiple disturbances combine. Nevertheless, we have ...limited insights into the mechanisms that stabilise communities, particularly how perturbations can be absorbed without restructuring (i.e. resistance). Here, we expand the concept of compensatory dynamics to include countervailing mechanisms that absorb disturbances through trophic interactions. By definition, ‘compensation’ occurs if a specific disturbance stimulates a proportional countervailing response that eliminates its otherwise unchecked effect. We show that the compounding effects of disturbances from local to global scales (i.e. local canopy‐loss, eutrophication, ocean acidification) increasingly promote the expansion of weedy species, but that this response is countered by a proportional increase in grazing. Finally, we explore the relatively unrecognised role of compensatory effects, which are likely to maintain the resistance of communities to disturbance more deeply than current thinking allows.
The global fall and rise of oyster reefs McAfee, Dominic; Connell, Sean D
Frontiers in ecology and the environment,
03/2021, Letnik:
19, Številka:
2
Journal Article
Recenzirano
Non-native species that act as ecosystem engineers – creating new or reintroducing former habitats – challenge perceptions in conservation and restoration. In the wake of the loss of oyster reefs ...worldwide, non-native Pacific oysters (Magallana gigas) are now spreading extensively across the former distributions of native reef-building oyster species. Here, we show that the coastal expansion of Pacific oysters (approximately 1000 km per year) is occurring across the eradicated distribution (>100,000 km) of native oysters. Where Pacific oysters build reefs, they create conspicuous challenges and opportunities for society. Although their reefs alter benthic habitats and often displace native species, Pacific oysters are one of the world’s most valuable aquaculture species, and they also provide numerous ecosystem services. Whether Pacific oysters are the forerunners of habitat regeneration will challenge natural resource management as well as policy making, as coastal communities weigh the pros and cons of embracing or removing this non-native species.
Accelerating CO2 emissions have driven physico-chemical changes in the world's oceans, such as ocean acidification and warming. How marine organisms adjust or succumb to such environmental changes ...may be determined by their ability to balance energy intake against expenditure (i.e. energy budget) as energy supports physiological functions, including those with adaptive value. Here, we examined whether energy budget is a driver of physiological adaptability of marine calcifiers to the near-future ocean acidification and warming; i.e. how physiological energetics (respiration rate, feeding rate, energy assimilation and energy budget) relates to adjustments in shell growth and shell properties of a calcifying gastropod (Austrocochlea concamerata). We found that ocean warming boosted the energy budget of gastropods due to increased feeding rate, resulting in faster shell growth and greater shell strength (i.e. more mechanically resilient). When combined with ocean acidification, however, the gastropods had a substantial decrease in energy budget due to reduced feeding rate and energy assimilation, leading to the reduction in shell growth and shell strength. By linking energy budget to the adjustability of shell building, we revealed that energy availability can be critical to determine the physiological adaptability of marine calcifiers to the changing oceanic climate.
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•Energetics and shell properties of gastropods were measured under future climate.•Ocean warming increased the feeding rate and hence energy budget of gastropods.•The boosted energy budget was linked to increased shell growth and shell strength.•Ocean acidification caused these positive effects of warming to become negative.•Energy budget determined the adjustability of shell building process in calcifiers.
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