EESA11 Lec 9 possible questions

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Environmental Science
Maria Dittrich

EESA11 Lec 9 KNOW + possible questions Know:  Main issue of Lake Erie – area of eutrophication, hotspot for enviro Canada o West – shallow and small, always mixes. NO oxygen problems o East – very deep, no oxygen depletion o Central basin (PROBLEM AREA!!)  Eutrophication most happens here; deep enough to get stratified, not deep enough to get oxygen. Once oxygen depletes, have problems with the sediment. Only the top area of this part gets oxygen  Bottom layer of water does not mix with warmer surface water – no opportunity for oxygen replenishment from the atmosphere  Human impact on freshwater ecosystems: demotechnic concept: o Combined effect of the population as well as of production-consumption in a technological sense  Phytoplankton o Producers take energy from the sun and nutrients from the water and convert them into food  Largest number of producers in the Great Lakes = phytoplankton o Survive as long as they are near water surface and have proper nutrients. Bloom in the spring when the water is warming up and the most nutrients are available. o E.g. Anabena – form chains hundreds of cells long  Pediastrum – collection of small phytoplankton cells that join together in a circle  Cladophora – branching, green filamentous algae. Grows attached to solide substrate  Zooplankton – free-floating animals. Types: o Copepod – all have antennae and a fan tail o Mysis – one of the largest and can move very fast through the water when threatened. Good food for young fish o Rotifer – using small, hair-life fibers, they swirl water by their mouths to gather food for themselves. Once the food is caught, they close their mouths and digest it o Holopedium – for a clear, gooey envelope around themselves where the females carry eggs  Managing Methods – what is TFM and how it deals with invasive species o Barriers + male-stereilization + TFM (currently used by GLFC)  TFM (3-trifuluoromethyl-4-nitrophenol) was effective in controlling sea lampreys without affecting other species – is most effective when it is used to target larval sea lampreys in streams. Is applied to streams – NOT open waters o Emerging alternative method: pheromones and repellants  Alternative managing methods: o Pheromones – secreted or excreted chemical factor that triggers a social response in members of the same species. Impacts the behaviour of the receiving individual o Larval pheromones (migratory odors) – 90% of the time, lampreys head to streams with presence of larval odour o Repellents (dead sea lamprey/spit?) – can be used in combination with pheromones Possible questions 1. What causes the hypoxia problems in Lake Erie? a. Hypoxia problems are only in the central basin of Lake Erie – not the east or west. Bottom layer of water in the central basin cannot mix with warmer, surface water
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