Stressors

Question 1

Hvad er en stressor?

Answer 1

What is a stressor (for an ecosystem/organism): En eller flere faktorer som påvirker en eller flere organismer negativt kort eller længervarigt.

Stressors re any physical, chemical or biological parameters or entities that directly or indirectly result in biotic responses of concern.

Question 2

Hvilke stressors findes i marine environments?

Answer 2

What stressors is in the marine environment: Temperature rise, lower oxygen/hypoxia, chemicals (fx oil pollution) , noise pollution, shipping, constructions, waste-water, heavy loads of nutrients, overfishing, acidification, invasive species transportation, solcreme, hormonforstyrrende stoffer, heavy metals, ødelæggelser af bund, habitat destruction,

Question 3

Interaction types of multiple stressors:
Stressor A + Stressor B
Forklar

Answer 3

Interaction types of multiple stressors:
Stressor A + Stressor B
Kan blive til;
Additive A+B
Synergistic > A + B
Antagonistic < A + B

Question 4

I relation til interactions mellem multiple stressors.
Stressor A + Stressor B
Forklar hvad betyder hvis de er antagonistiske?
Kom med et eksempel of a real life example på dette

Answer 4

Antagonistic < A + B
the combined effect is less than the expected additive effect

Real life example på antagonitisk :
Growth of algal turf (græs) in a coral reef
Stressor A - Removal of herbivores
Stressor B - Addition of nutrients

Question 5

I relation til interactions mellem multiple stressors.
Stressor A + Stressor B
Forklar hvad betyder hvis de er synergetic?
Kom med et eksempel of a real life example på dette

Answer 5

Synergistic > A + B
the combined effect of the two stressors is greater than the expected additive effect

Nogle kemikalier kan være synergetic

Ofte kan en 3. stressor faktisk være grunden til syngergi effekter

Syngergi kan tit være overestimeret

Question 6

I relation til interactions mellem multiple stressors.
Stressor A + Stressor B
Forklar hvad betyder hvis de er additive?
Kom med et eksempel of a real life example på dette

Answer 6

Additive A+B

The combined effect of two or more stressors is additive when equaling the sum of the individual effects

Real life example på additive:
Growth of algal turf (græs) in a coral reef
Stressor A - Addition of nutrients
Stressor B - Addition of sediments

Question 7

Hvad er en discrete stressor et discrete stressor event?

Answer 7

Stressor magnitude:
- Fast on-set. Slow dissipation (Stiger hurtigt, falder langsomt. Spids parabel)
- Slow on-set. Slow dissipation (parabel)
- Oscilliating (mange højdepunkter på kurven)
- Slow on-set. Fast dissipation (stiger langsomt, falder hurtigt)

Event. Kan være nutrient pollution om sommeren.

Question 8

Hvad er en continiuos stressor og et continious stressor event?

Answer 8

Stressor magnitude:
- Consistent (vandret konstant graf)
- Ramped (stigende lineær kurve)
- Oscillating (bølget stigende kurve, mange højdepunkter)
- Stepwise (trappetrin kurve)

Event. Kan fx være global warming som er et continiuos stessor event.

Question 9

An organisms life history matters når den møder stressors / stressor events.
First stressor encounter - hvordan kan organismen reagerer 2. gang den møder denne stresser?

Answer 9

Søjle diagram. 1. stressor har en vis højde:

• Same sensitivity (søjle har samme højde som 1. stressor event)
• Acclimation with lower sensitivity (lavere end 1. stressor event)
• Induced sensitivity (højere reaktion end første gang)

Stressors do not need to overlap in time to have
cumulative effects, since the ‘legacy’ of previous stressors can alter the response of the ecosystem
(and its component populations) to future stress

Question 10

Eksperimenter med stressorer. Er det nemt at sætte op? Hvad er svært?
Discuss at least four challenges of planning and conducting experiments with multiple
stressors

Answer 10

• > 2 stressors are huge experimental set-ups
• Complex interactions between multiple stressors  hard/impossible to predict
• Challenging to interpret the mechanisms of interactions
• Realistic combinations?
• Timing of stressors: simultaneous vs. in sequence
• Duration and magnitude of stressors
• Adaptation potential of organisms

Question 11

Timing of stressors. Explain why the duration and timing of stressors matter..
Forklar simultaneous vs. in sequence.

Answer 11

Tidspunktet og varigheden af både de første virkninger af og genopretningen fra stressfaktorer er særligt kritisk, og mindst lige så vigtigt som den rumlige komponent, der har været primært fokus for størstedelen af forskningen hidtil.

Tid er afgørende, fordi stressfaktorer sjældent, hvis nogensinde, virker i perfekt synkronitet, og rækkefølgen og overlapningen af varigheden vil forme deres kombinerede virkninger.

Desuden behøver stressfaktorer ikke at overlappe i tid for at have kumulative virkninger, da ‘arven’ fra tidligere stressfaktorer kan ændre økosystemets respons (og dets komponentpopulationer) til fremtidige stressorer.

Question 12

Which type of interactions are assumed to be most common in the marine environment?

Answer 12

The interaction of organisms of different species is referred to as interspecific relations and can include
symbiotic interactions,
competition,
parasitism, and
infectious disease.

When two organisms occupy the same ecological niche, competition for resources can occur

Question 13

Hvad er ecological memory? Hvordan kommer det til udtryk og nævn et eksempel med marine sticklebacks (Gasterosteus aculeatus)

Ecological memory can alter our ability to detect and predict multiple stressor impacts: even if a past stressor has long since disappeared, its legacy may still be playing out in a system facing new stressors

Answer 13

Ecological memory – the influence of past stressors on future ecological
responses – from genes to ecosystems.

The ability of past stressors to influence the future ecological responses of a population, community, or ecosystem.

This can include acclimation, parental effects, and species sorting due to past stress, including lagged indirect legacy effects.

For instance, a recent single-stressor study found that marine sticklebacks (Gasterosteus aculeatus) exhibit carry-over effects of a high CO2 environment, causing offspring to perform poorly under conditions that differ from those experienced by their parents (even if these new
conditions were actually less ‘stressful’).

Question 14

Organisms with different generation times will experience multiple stressors (and the degree to which they overlap in time) in different
ways.
Forklar hvorfor (tidsramme, reaktioner, stofskifte, forskel på store og små organismers akklimatisering)

Answer 14

Dette skyldes, at generationstiden sætter den karakteristiske tidsramme, hvor individer oplever og reagerer på miljømæssige forstyrrelser.
Organismer, der opererer i forskellige tidsrammer, vil derfor reagere forskelligt på en given sæt stressorer over en bestemt absolut tidsramme.
Stofskiftehastighed og de livshistoriske træk, det driver (og især generationstid), har derfor stor potentiale for at hjælpe os med at forudsige, hvilke stressorer der er relevante for en given organisme, samt hastigheden og omfanget af dens respons.

For eksempel viste en nylig undersøgelse, at størrelse kan forklare betydelig variation i hastigheden af termisk akklimatisering (tilvending) på tværs af mange taxa, hvor mindre organismer tilsyneladende akklimatiserer sig hurtigere, men til en mindre grad, end større organismer

Question 15

Hvad forårsager variation in generation times across species

Answer 15

Largely determined by their body sizes
and (physiologically) operational temperatures.

There is a general inverse relationship between generation time and mass-specific metabolic rate

Question 16

Har større dyr faster eller slower metabolic rate end alger?

Answer 16

Jo mindre man bliver - jo højere metabolic rate. Jo hurtigere generation time.

Compare the response in a ‘slow’ community
comprising large, long-lived organisms (i.e., a forest of trees) versus a ‘fast’ community dominated by smaller, short-lived organisms.

one would expect fundamentally different community-level ecological memory

Question 17

To predict responses to multiple stressors from individuals to the whole ecosystem, what is the first thing to look into (hos de dyr man undersøger)

Answer 17

Their metabolic rate and generation time

their metabolic rate which determine the timescales at which individuals operate and therefore, ultimately, the ecological memory at different levels of ecological organization

Question 17

the spatial component of stressors has been the primary focus of most research to date. What is also super import to consider ?

Answer 17

the timing and duration of both the initial impacts of and recovery from stressors are particularly critical, and at least as important as the spatial
component

timingen og varigheden af både de indledende påvirkninger af og genopretning fra stressfaktorer er særligt kritiske og mindst lige så vigtige som den rumlige komponent

Question 17

Hvis man skal finde ud af, om et dyr oplever en stressor som continious eller discrete - hvad skal man så kigge på / kortlægge hos dyret først?

Answer 17

Metabolic rates and lifespan/generation times

Question 17

Forklar at en stressor kan have “lagged” effects

Answer 17

Reaktioner på en stressor der sker længe efter den måske er væk.

Fx trophic cascades eller lavere antal arter et sted flere år efter

For instance, lichen diversity remained unchanged 2.5 years after
adjacent forest clearance, but declined after a further 14 years [8] due to dispersal limitations.
Another example is the Nitrogen Cascade, whereby increased soil nitrogen content (from deposition) causes changes in plant composition, which then causes lagged changes in herbivore,
and subsequently predator, communities.

These studies demonstrate that ecological memory can alter our ability to detect and predict multiple stressor impacts: even if a past stressor has long since disappeared, its legacy may still be playing out in a system facing new stressors.

Question 18

Forklar hvad “adaptation” til en stressor er

Answer 18

refers to the relatively well-known process of natural selection over multiple generations, where species’ adapt to function better in the face of environmental challenges

Question 19

Når man snakker om stressorer - forklar hvad the spatial component er (i test forsøg med stressorer)

Answer 19

comparing locations with and without a stressor

Question 20

Agricultural nutrient pollution is often a discrete stressor that oscillates
over time - hvad betyder det?

Answer 20

At det kommer “i bølger”
fx seasonal spikes in run-off reflecting farming activity

Question 21

climatic warming can be considered as an umbrella or master
stressor - hvorfor?

Answer 21

fordi under climate change

all other stressors, which are increasingly prevalent across the world, play out

Question 22

Hvad er mest common ? additive effects af en stressor eller non-additive effects?

Answer 22

Non-additive effects.

Så tit er stressorer ikke A + B

men nok nærmere enten antagonistic eller synergetic

Question 23

Når man skal determine the ecological memory of the ecosystem as a whole - hvad er så det vigtigste at kigge på

Answer 23

The distribution of generation times of different species in a community is critical in determining the ecological memory of the ecosystem as a whole

This is because generation time sets the characteristic timescale at which individuals experience, and respond to, environmental perturbations

Organisms operating at different timescales will do so in different ways to a given set of stressors over a particular absolute timescale. Therefore, the taxonomic composition of species with different generation times in an ecosystem should arguably shape overall ecological memory

Question 24

Predict generation times of different species - hvordan gør man så lige det ?

Answer 24

To this end, Ecological Metabolic Theories (EMTs),
drawn from both the Dynamic Energy Budget and the Metabolic Theory of Ecology (MTE) frameworks provide a good starting point.

På det mest fundamentale niveau beskriver EMT’er, hvordan hastigheder af metaboliske processer i celler forudsiger
- hvordan individuelle organismer optager ressourcer fra miljøet,
- omdanner dem til andre former for stoffer til vækst og reproduktion
- og excreter affaldsstofferne.

Dette sætter scenen for forudsigelsen af metabolisme hastigheder
og på en måde på højere niveauer af biologisk organisering forudsige: biomasse og diversitet

Question 25

The simplest way to go from individuals, through populations, to ecosystem-level responses to stressors is to

Answer 25

assume that the ecosystem response is a weighted sum of the individual populations’ responses
to one or more stressors

Hvis man altså kan måle arten/arternes response på stressoeren.

Her assumer man dog, at biomassen af arten er konstant gennem den tid som stressoren påvirker (hvilket jo ikke altid er sagen).

Denne tilgang er dog begrænset i øjeblikket at den ikke kan rumme realistiske trofiske og ikke-trofiske interaktioner mellem arters populations. For virkelig at gå fra multistressor-reaktioner fra individuelle organismer til hele samfund og økosystemer, skal kompleksiteten af tidsvarierende, ikke-lineære artsinteraktioner (dvs. food-web medieret) overvejes

Question 26

(ikke spørgsmål)
Ikke-lineariteter og kaskadeeffekter kan generere uforudsigelige udsving i størrelsen af interagerende populationer og derfor udbredelse af stressor-inducerede forstyrrelser på tværs af fødenettet (f.eks. fra primærproducenter til topforbrugere).
Ydermere dæmpes eller ændrer virkningerne af stressfaktorer sig ofte, når de bevæger sig gennem fødenettet pga af systematiske forskelle i tidsskalaer eller interagerende arter.

Answer 26

For eksempel i akvatiske systemer, hvor den primære
producenter er (lille krop og hurtigtlevende) alger, kan man observere meget hurtige reaktioner ved bunden af føde-nettet, med tidsforsinkelser og mere aggregerede effekter på de højere trofiske niveauer (som er større og længelevende).
Føde-Nettets kropsmassestruktur driver denne dynamik via metaboliske hastigheder og generationstider

Question 27

How do the order, frequency, and
duration of multiple stressors affect
their cumulative ecological impact on
species’ populations?

Answer 27

Rækkefølgen, hyppigheden og varigheden af flere stressfaktorer kan have betydelige konsekvenser for deres kumulative økologiske virkning på populationsniveau for arter.

Rækkefølgen, som stressfaktorer påvirker en population, kan ændre den samlede respons. For eksempel kan en stressor, der forekommer først, svække en populations modstandskraft og gøre den mere sårbar over for efterfølgende stressorer. Omvendt kan en stressor, der kommer senere, have mindre effekt, hvis populationen allerede er påvirket af tidligere stressorer.

Hyppigheden af stressfaktorer, dvs. hvor ofte de forekommer, kan også påvirke populationens evne til at tilpasse sig og komme sig efter påvirkninger. Hyppige stressorer kan forhindre en fuldstændig opsving mellem påvirkninger og føre til akkumulerede negative effekter på populationen.

Varigheden af stressorer, hvor længe de varer, kan have betydning for, hvor lang tid en population har til at tilpasse sig eller komme sig. Langvarige stressorer kan have mere alvorlige og langsigtede konsekvenser for populationen sammenlignet med kortvarige stressorer.

Samlet set er det komplekse samspil mellem rækkefølgen, hyppigheden og varigheden af flere stressfaktorer afgørende for at forstå deres samlede økologiske virkning på arternes populationer.

Question 28

Fra et andet spørgsmål skriver jeg det her om vigtigheden af rækkefølgen af stressorer: Omvendt kan en stressor, der kommer senere, have mindre effekt, hvis populationen allerede er påvirket af tidligere stressorer.
Hvad mener du med det eller kan du give et eksempel fra havets økosystemer fx?

Answer 28

Forestil dig en situation, hvor et marine økosystem allerede er påvirket af overfiskeri, hvilket resulterer i en betydelig reduktion af rovdyrbestanden. Som et resultat er der en overflod af byttedyr, såsom småfisk og rejer, i økosystemet. Dette skaber en midlertidig stigning i byttedyrsbestanden.

Senere, når denne situation allerede er etableret, oplever økosystemet en pludselig forureningsepisode, hvor giftige kemikalier spildes i havet. Disse kemikalier forurener vandet og påvirker direkte de tilbageværende organismer i økosystemet, inklusive både byttedyr og rovdyr.

I dette eksempel har den tidligere stressor, overfiskeri, allerede ændret dynamikken i økosystemet ved at reducere rovdyrbestanden. Når forureningen sker senere, kan dens direkte virkning på både byttedyr og rovdyr være mindre alvorlig end hvis det var sket i et mere intakt økosystem med en sund rovdyrbestand. Dette skyldes, at der allerede er færre organismer til stede, som kan påvirkes af forureningen, på grund af den tidligere stressors virkning.

Så den senere stressor, forureningen, har en mindre effekt på populationerne, fordi de allerede er blevet påvirket af den tidligere stressor, overfiskeri.

Question 29

Does previous exposure to a particular
stressor promote or erode resilience to
future stressors (through ecological
memory) and does this response
depend on stressor similarity?

Answer 29

Absolutely! Previous exposure to a particular stressor can have significant implications for the resilience of a population or ecosystem to future stressors. This concept is often referred to as ecological memory.

Promoting Resilience:
If a population or ecosystem has previously been exposed to a stressor and has successfully adapted or developed mechanisms to cope with it, this can enhance its resilience to similar stressors in the future. For example, if a population of fish has previously experienced high levels of water pollution and has evolved physiological adaptations to detoxify their bodies or behavioral adaptations to avoid polluted areas, they may be more resilient when faced with similar pollution events in the future.

Eroding Resilience:
On the other hand, repeated exposure to stressors can also erode resilience over time. If a population or ecosystem is continually stressed by the same or similar stressors without adequate recovery periods, it may become more vulnerable to additional stressors. This can lead to a decline in population numbers, loss of biodiversity, or degradation of ecosystem services. For example, if a forest ecosystem is repeatedly subjected to drought conditions without sufficient time for recovery, the trees may become weakened, making them more susceptible to disease outbreaks or insect infestations.

Dependence on Stressor Similarity:
The response of a population or ecosystem to future stressors may depend on the similarity between the previous stressor and the new stressor. If the new stressor is similar to the previous one, the adaptations or mechanisms developed in response to the previous stressor may confer some degree of resilience to the new stressor. However, if the new stressor is significantly different from the previous one, the adaptations may not be effective, and resilience may be compromised. For example, if a population of plants has adapted to withstand high temperatures during heatwaves, they may not be resilient to sudden flooding events caused by heavy rainfall, as these require different adaptive strategies.

Question 30

Do temporally asynchronous multiple
stressor events have outcomes
(e.g., dominance of nonadditive affects)
comparable with those of stressors
acting in perfect synchrony?

Answer 30

Temporally asynchronous multiple stressor events can have outcomes comparable to those of stressors acting in perfect synchrony, particularly if their effects interact in nonadditive ways or if there are delayed responses in the ecosystem. Understanding these interactions and their implications is essential for predicting and managing the impacts of multiple stressors on ecosystems and populations.

The key aspect to consider is the cumulative effect of these stressors on the ecosystem or population.

Nonadditive Effects:
Temporally asynchronous stressors may interact in ways that are nonadditive, meaning the combined effect of multiple stressors is not simply the sum of their individual effects. Instead, their interaction may amplify or diminish the overall impact. For example, if a population of fish is exposed to overfishing followed by habitat destruction due to pollution at a later time, the cumulative effect on the population may be greater than if the stressors occurred independently. This nonadditive effect could lead to a more significant decline in population numbers or biodiversity loss.

Delayed Responses:
Another important consideration is the potential for delayed responses to stressors. Even if stressors do not occur simultaneously, their effects may accumulate over time, leading to delayed or lagged responses in the ecosystem or population. For instance, if a coral reef ecosystem experiences bleaching due to high water temperatures followed by nutrient runoff from land-based sources, the full extent of the damage may not become apparent until some time after the stressors have occurred. This delayed response can make it challenging to attribute changes in the ecosystem to specific stressors.

Context Dependency:
The outcomes of temporally asynchronous stressor events can also depend on the context of the ecosystem or population. Factors such as the resilience of the ecosystem, the adaptability of the species involved, and the availability of resources for recovery can influence the overall impact of stressors. In some cases, the cumulative effect of temporally asynchronous stressors may be comparable to that of stressors acting in perfect synchrony, while in other cases, it may differ significantly.

Question 31

If we rescale responses in terms of
generation time (rather than absolute
time), do we see a consistent response
across species of different lifespans?

Answer 31

Rescaling responses in terms of generation time rather than absolute time can provide insights into how different species, with varying lifespans, respond to stressors.

Consistency Across Species:
Rescaling responses based on generation time allows us to compare how different species respond to stressors on a more equal footing. This approach accounts for the fact that organisms with shorter generation times may experience and adapt to environmental changes more rapidly compared to those with longer generation times. Thus, it provides a common metric for evaluating responses across species.

Relative vs. Absolute Time:
Rescaling responses in terms of generation time shifts the focus from absolute time scales to relative time scales. This is particularly useful when comparing responses among species with different lifespans. By normalizing responses to generation time, we can identify patterns or trends that may not be apparent when using absolute time scales.

Understanding Adaptation Rates:
Examining responses relative to generation time can help us understand the rate at which different species can adapt to environmental changes. Species with shorter generation times may exhibit faster adaptive responses to stressors, while species with longer generation times may show slower responses. By analyzing responses in this context, we can gain insights into the adaptive capacity of different species.

Implications for Conservation and Management:
Rescaling responses in terms of generation time can have implications for conservation and management efforts. It can help prioritize species or populations that may be more vulnerable to environmental changes based on their generation time and adaptive capacity. By considering these factors, conservation strategies can be tailored to address the specific needs of different species or ecosystems.

Question 32

How do we scale up population-level
responses to temporally variable
stressors of organisms operating at different timescales to entire ecosystems?

Here are some steps and considerations for this process:

Answer 32

Scaling up population-level responses to temporally variable stressors of organisms operating at different timescales to entire ecosystems involves considering the interactions and feedbacks between populations, communities, and environmental factors.

Identify Key Species and Trophic Interactions:
Begin by identifying the key species within the ecosystem and understanding their roles in trophic interactions, nutrient cycling, and habitat structuring. Consider how different stressors affect these species and their interactions with each other.

Account for Temporal Variability:
Recognize that stressors may vary in timing, duration, and intensity, and different species may respond differently to these variations. Account for temporal variability by studying long-term data sets, conducting experiments across different time scales, and using models to simulate ecosystem dynamics under various stressor scenarios.

Evaluate Ecological Memory and Resilience:
Consider the concept of ecological memory, which refers to how past environmental conditions and disturbances influence ecosystem responses to current stressors. Evaluate how populations with different generation times and adaptive capacities contribute to ecosystem resilience and recovery from stressors.

Integrate Multiple Stressors:
Recognize that ecosystems are often exposed to multiple stressors simultaneously or sequentially. Understand how interactions between stressors influence ecosystem dynamics and resilience. Consider both additive and non-additive effects of stressors on population dynamics and community structure.

Model Ecosystem Responses:
Use ecological models to simulate how populations and communities respond to temporally variable stressors over different time scales. Incorporate feedback loops, trophic interactions, and environmental feedbacks into these models to capture the complexity of ecosystem dynamics.

Validate Models with Empirical Data:
Validate ecosystem models with empirical data from field observations, experiments, and long-term monitoring programs. Compare model predictions with observed ecosystem responses to stressors to ensure that the models accurately represent real-world dynamics.

Predict Future Ecosystem States:
Use validated ecosystem models to predict how ecosystems may respond to future stressor scenarios, such as climate change, habitat loss, or pollution. Consider how changes in population dynamics and community structure may cascade through the ecosystem and affect ecosystem services and functions.

Inform Management and Conservation:
Use the insights gained from ecosystem modeling to inform management and conservation strategies aimed at mitigating the impacts of stressors on ecosystems. Develop adaptive management approaches that account for the dynamic nature of ecosystems and the uncertainties associated with future environmental changes.

Question 33

(ikke et spørgsmål)

There is a need to move beyond current overly simplistic scenarios of perfectly overlapping stressors: future research needs to consider stressor sequences, the degree of stressor overlap, and how these change for organisms of different generation times in ‘fast’ versus ‘slow’ communities

Answer 33

Most of our current knowledge on multiple stressor interactions is based on unrealistic synchronous scenarios.
We argue that ecological responses will change dramatically under realistic asynchronous scenarios due to ecological memory, with implications for the prevalence of additive versus nonadditive effects
and, by extension, the management and conservation of natural ecosystems