Akiko Ogawa’s

EFB516 Ecosystems Notes

April 5, 2001 (Thu)

Disclaimer:

These notes are my personal notes. The course instructor or TAs have no responsibility for the contents or any discrepancies between the materials presented in the classroom and these notes. You cannot use or refer to these notes to support or defend your answers on your exams. I suggest you use these notes to complement your own notes, and not to solely rely on. I would appreciate your feedback on any part of these notes that I may be misunderstanding.

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Lecture topic:

Estuaries (section 3)

Estuaries (section 3)

·        As the season progresses, which tends to be more important - nanoplankton or macrophytoplankton?

·        What charactereizes small things in estuaries, or ecosystems? – High turnover rates. Would it make nanoplankton good food for zooplankton? – Not necessarily because they are so small that they go through zooplankton’s filters. Nanoplankton are abundant and may be especially important for food chains.

·        How do you find out how important little things are? – Measure photosynthesis, and pore the same bottle of water through a plankton net and measure photosynthesis again. Small things are important for the food chain. You tend to get 90% primary production after filtering. Refer to Pomeroy in the reader.

·        You may have very high prod’ty with these little things, but may not end up going through the food chain. A experiment in Scotland, radio actively labeled microbial food chain, and in another experiment, labeled macrophotoplankton, and monitored how much ended up in salmons. Almost none of first ended up in salmon. For nanoplankton to become available in terms of size (as a diatom) for zooplankton, they need two more steps of consumers, such as by microflagellates, and then by micro crustaceans. The amount of primary production that end up in fish isn’t strictly a function of rate of production, but its ability for it to enter into the food chain.

·        Why diversity of birds is so high when diversity of many other organisms is low?

·        If you want to know the diversity of a place, do you want to take a snapshot at one point of time or that of whole year? – Whole year.

·        Why diversity of birds can be so high? They don’t live in the medium. They can fly away.

·        Estuarine animals: alligators (moves stuff around), nutria, snapping turtles.

·        Where you have large environmental stresses, those organisms that can survive there is often enormously abundant because they don’t have competition. For example, below a sewage treatment plant, there are very few species, but they are often incredibly abundant. They tend to have red color, hemoglobin to tolerate low oxygen.

 

Slides

·        John Day and his brother Richard.

·        Louisiana: Culture is different – French from Nova Scotia, mixed with Carribean black people. The culture ahs strongly influence by the richness of the ecosystem. Louisianans tend to be suspicious about outsiders. Things you would notice about Louisiana – in certain sense, it’s homogenous, incredibly flat, incredibly green, roughly half land and half water. Where you have influence from oceans, you have dendritical branching patterns, where the branches of creeks dissipates the tidal energy as it goes inland, and spread the water throughout as the tide goes up and down. The tides tend to be greater from summer to winter.  The wind comes from north and blows the water out of marsh and they become very dry.

·        Tourist map: tells important things about Louisiana

o       Largest producers of seafood except Alaska.

o       Many oil wells. LA may still be the nation’s No. 1 natural gas, and has been No. 4 oil producer. The oil industries came in 1930s. Oil industries destroyed original economy and culture there.

o       Green area=uplands, brown area=marshes. Marsh area is maintained by the interaction of riverine and oceanic and geological forces that generated the dynamic system, in which river is always changing.

o       LA state bird, brown pelican was eliminated from LA by DDT four years ago. LA brought in Florida Pelican once they stopped the use of DDT.

·        Historical map of river course shifts: Basic geology of this area is based on the fact that about every 5,000 years rivers shift from one place to another. 25,000 years ago, sea level was lower, after a delta formed, river found shortest distance, and built a new delta. This is the way it works without human intervention.

·        Lower deltaic plain:

o       Why do we know the geology of this area very well? – because oil industries investigated.

o       Distributary channels. Particle size a river can carry is a function of velocity. Where river is actively flowing, sand is carried and deposited as sandbars. Mississippi river is actually flowing more rapidly than in any place in source, northern Minnesota, and top of Rocky Mountain in Montana up in Yellowstone Park. Next to sandbar is relatively coarse sediments called natural levees. Natural levees are caused when the river overflows in Spring. Water velocity slows down and largest particle falls out immediately and smaller particle are carried farther away, sometimes miles away, generating interdistributary basins. Sediments piles up in a gradient of size from coarse, medium, to fine. Over time, a new distributary will be constructed with the same particle size distribution, along the distance from the river.

o       Also in this basin are huge areas of organic deposits because of rich marshes. Why we find oil and gas in this situation? What are the towers you see in Elizabeth, New Jersey. – Cracking towers, which are taking molecule and cracking them into small pieces. The same thing is happening here with natural energy. Large organic production over 100s of years. When we have one-in-million-year flood, whole area is covered with sand and organic material by inorganic material. When the layer receives enough heat and pressure, OM starts cracking and starts to crate oil and gas. The deeper the more cracked, i.e., the more gas from deep wells. We don’t find oil below 8,000ft because all has been cracked into gas.

·        Mississippi river flood plain: the gradient of particle sizes is observable. Natual levee is the only highland and it’s where cultural features are.

·        Distributary channel: importance of water velocity and retention of materials in suspention.

·        Natural levee: changed by human action with the construction of artificial levee.

·        Disecting the delta: creates highland at the edge of river, low land in between colonized marsh plants such as Spartina.

·        Processes of delta formation over time: New distributary basin building out, depositing sediments, building subdistributaries, creating marshes in between, until it gets so far out that it equilibrate to the sea from some other route. When you have a high spring flood, the river will break through.

·        Vegetation zone map: Spartina alterniflora near the sea->Spartina patens next inland->transition zone-> freshwater swamps noted by cypress trees. You have a fresh water marsh far out at the tip of the delta next to the sea because of volume of freshwater from Mississippi river. Because of artificial levees, fresh water doesn’t spread out.

·        Graph of fisheries yield and primary productivity (in the right - click to blow up.): X: primary productivity in C/sq. m/ yr. Y: fisheries yield in kg/ha/yr. Estuaries are richer in fisheries prodution than freshwater for the reason 1) more primary production, 2) more efficient food chain since it has more fisheries yield from same PP. Estuaries appear to be 7 to 8 times more efficient in turning plant production to animal production. The important reason may be detrital food chain.

·        John Day’s study of estuarine food chain. Most of PP takes place on the marsh. Most of the prod of the marsh goes into respiration of plants and phytoplankton. Half of it is consumed by animals on the marsh, the rest is exported to water. This is joined by aquatic production, of which half is consumed in the tide channel, and half of which is exported to the Gulf of Mexico. This is an example of Outwelling hypothesis - very productive marsh estuarine area export PP with net outflow of water to coastal areas supporting fisheries. Originally idea is to protect from development. Some studies show export and some don’t. Most of fish production in blue water ecosystem was coastal. This is considered to one of the reasons.

·        1400 and 1600 development of Delta

·        1956 and 1978: wetlands in the interdistributary regions are beginning to degrade in 1978. Southern LA is losing 20 sq. miles of coastal region every year. Why?

·        Artificial levee on top of natural levee. Ocean going ship is higher than houses. Artificial levees extend up more than 1000 miles. This means that 1) interdistributary basins are starved of sediments. No long building processes, 2) if there is a flood, it has no place to go. What does that do to the level of the river? Makes it higher. 1-in-100-year floods now comes once in 30 years.

·        Freshwater marsh with cypress tree with pipeline.

·        Cypress marshes with levees that the flow of river water. No water-> anaerobic soil becomes aerobic -> soil is oxidized -> soil decomposition -> kill trees.

·        Dredging for gas extraction. Second reason for land loss in southern LA – dredging for transportation or gas cutting off the sheet flow.

·        All the distributary basins are chopped out for oil and are dieing because they don’t have sediments due to levees. Paul Kemp is devoted to rebuilding southern LA.

·        Artificial levees may cause two things – 1) mississippi shift its course, or 2) artificial levee structure works as a hurricane funnel.

 

 

Last modified: April 11, 2001

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