LEC 33 - HUMAN THREATS TO ECOSYSTEMS Flashcards

1
Q

how do dead zones in the ocean arise?

A

rivers carry eutroph water out to the ocean, where the local region has an algal bloom and then becomes devoid of oxygen

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2
Q

in the gulf of mexico, when was hypoxia thought to have started? how did we hypothesize this?

A

things began to change in 1950s, w widespread hypoxia in the 1970s. we used paleolimentic analysis to come to this concl

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3
Q

what makes sediment disturbance such a problem? (3 outlined)

A

prevents macrophytes from taking root, decr light pen fucks w prim prod ability to photosynth

also when sediment does settle, it fills in the gaps where inverts and fish live in/spawn, which harms them (EPT are very sensitive)

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4
Q

the effects of urbanization are felt after storms. what is this effect, and how do know urbanization is the cause? how can we measure this?

A

following storms, urbanized areas experience way higher runoff discharge than otherwise. the mechanism by which non-urbanized areas combat this is through percolation into soil, which urbanized areas no longer have (they got concrete n shit)

we can measure this through the runoff coefficient, which measures imperviousness of ground to the proportion of a storm event that ends up in the stream

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5
Q

what did the agricultural transect case study in new zealand tell us?

A

agriculture inputs are directly correlated to the health of a system

high agriculture inputs at 50-100km away from headwaters was correlated with:
- low chla
- dip in EPT (due to higher sediment)

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6
Q

what is the IBI, and what does it measure?

A

the Index of Biological Integrity is an organism based metric of ecosystem health not unlike the EPT, but its more comprehensive

measures multiple stressors, species diversity, prevalence of tolerant/intolerant species, etc

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