3- human impacts and multiple stressors

human impacts to marine ecosystems

- climate change

- coastal habitat destruction

- introduced species

- nutrient enrichment/eutrophication

- pollution (besides nutrients)

- overfishing/harvesting

stressors

- a factor (abiotic or biotic) that acts on an organism or ecosystem to negatively effect their performance in some way

- many stressors are necessary but are a problem when they increase or decrease to levels that are not favorable to the organism or ecosystem in question

- this means one species' negative stressor might not be a problem for another, changing competitive outcomes

multiple stressors

- ecosystems can be subjected to multiple stressors at a time naturally, but increasingly marine ecosystems are subject to multiple human-induced stressors

- in addition, two or more stressors can have complex interactions with each other

stressor interactions

- additive

- antagonistic

- synergistic

synergistic interaction

antagonistic interaction

masking

top-down control

- consumption

- ex. herbivory

- ex. overfishing

bottom-up control

- nutrient enrichment

- herbivory

trophic cascades can lead to regime shift

- long-term shift from one state of an ecosystem to another

- perturbation to environment

algal toughness and palatability

- Physical anti-herbivory defenses induced by increased nutrients

coral reef recovery framework

nutrients --> macroalgae --> resources --> herbivores --> foundation species

coral reef recovery

- in areas where herbivorous fish have increased

- in areas with large fish populations and refugia (cool water) from climate change