ENVS 202 1st Edition Lecture 13 Outline of Last Lecture I. Carbon and other Greenhouse GasesII. Climate ChangeIII. Nitrogen and FertilizersOutline of Current Lecture I. Marine EcosystemsII. Oceanography and HypoxiaCurrent LectureI. Marine EcosystemsWhat issues are there with marine ecosystems?During the process of eutrophication, an influx of nutrients support algae, which consume all the dissolved oxygen in the waterPlastics and pollutionOcean acidificationEndangered and invasive speciesDead zonesOverfishingCoral bleachingSea level riseFisheries managementRenewable energyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Oceanography and HypoxiaWhat are dead zones?Areas of low (hypoxic) or no oxygen (anoxic) that cause severe degradation of the marine ecosystemMost hypoxic zones of concern occur in enclosed estuaries and mouths of “polluted” riversLarge scale ocean circulation is wind-driven Why don’t ocean currents look like wind patterns then?Coriolis effect: rotating Earth – large scale ocean currents are driven to the right of the wind in the Northern hemisphereThis only has a significant effect on large scale weather and ocean currentsCalifornia Current System goes southward, is an Eastern boundary current (EBC)Why are EBC regions so productive? Upwelling brings nutrients to the surfaceWhat is upwelling?Deeper ocean water upwells to replace the surface water that is moving towards thewestCoastal upwelling: wind driven effect where surface water near the coast is pushed offshore and is replaces by deep waterThis is a seasonal feature on the PNW shelf, where deep waters are drawn up onto the shelf (affected by large scale ocean circulation, wind strength, Coriolis effect)Deep waters: these upwelled waters are cold and nutrient rich, driving high productivity in EBC areas like the California Current SystemSo how does low oxygen water form? Deep waters are already low in oxygen compared to surface waters Respiration on the shelf lowers oxygen levels even moreHigh nutrient, low oxygen water upwells, drives growth, that sinks, respiration occurs using up oxygenThis is a natural process, but in recent years there are more hypoxic zones than everDead zones on the OR shelf: hypoxic areas controlled by a combo of ocean currents, seasonal winds, oxygen cycling This is fundamentally different than dead zones elsewhereNot primarily caused by excess nutrient input by humans – eutrophicationHypoxia occurs when. . . Oxygen utilization (respiration) > Processes bringing new oxygen into the