LEC 33 - HUMAN THREATS TO ECOSYSTEMS Flashcards
how do dead zones in the ocean arise?
rivers carry eutroph water out to the ocean, where the local region has an algal bloom and then becomes devoid of oxygen
in the gulf of mexico, when was hypoxia thought to have started? how did we hypothesize this?
things began to change in 1950s, w widespread hypoxia in the 1970s. we used paleolimentic analysis to come to this concl
what makes sediment disturbance such a problem? (3 outlined)
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)
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?
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
what did the agricultural transect case study in new zealand tell us?
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)
what is the IBI, and what does it measure?
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