EE 144 Exam 4 Review (Preliminary) Fall 2024 PDF

EE 144 Exam #4 Review List Fall 2024 The exam will be a combination of multiple choice, matching, fill in the blank, etc. You may also be asked to interpret diagrams or sketch a diagram. Any calculations will be nice round numbers and will n...

EE 144 Exam #4 Review List Fall 2024 The exam will be a combination of multiple choice, matching, fill in the blank, etc. You may also be asked to interpret diagrams or sketch a diagram. Any calculations will be nice round numbers and will not require a calculator. You do not need to memorize equations. The format will be similar to the first three exams. Exam 4 will cover lectures 26-34 (Wednesday, Dec 4). You will not be asked questions from any reading on topics that I do not cover in class. The following list covers most of the topics that I consider important from the last few weeks of class: **NOTE this version is incomplete and was written before lecture 34. I’ll finish it and post a final version Wednesday evening. Lecture 26 Make sure you understand the concept of limiting factors for new productivity. Can be light in some cases, or nutrients. Macronutrients that can be limiting to marine productivity are nitrogen (in it’s “fixed” or biologically available forms, nitrate, nitrite, ammonia), phosphate, and silica (esp. for diatoms) Work in the mid-20th century by Redfield showed that the ratio of C:N:P in phytoplankton is 106:16:1. When diatoms are involved the “Redfield Ratio” becomes C:N:P:Si 106:16:1:16 Liebig’s Law of the Minimum states that phytoplankton growth is regulated not by the TOTAL amount of nutrients available but by the amount of the scarcest resource. So if plankton require 16x as much fixed N as P, and the ratio of N:P in the water is 12:1, N is the “limiting nutrient” Micronutrients can also sometimes limit productivity (Fe, Mn, Cu, Zn, B, Mo). Mostly metals. Biological requirement is very small but in some cases isn’t met and Fe for example can be the limiting nutrient. Make sure you’re familiar with sources of nutrients to marine ecosystems. N & P. Respiration is photosynthesis in reverse. Respiration by decomposers consumes oxygen, produces CO2, and “regenerates” nutrients back to seawater. The N:P ratio of seawater is typically close to 16:1 since most of the nutrients aren’t “new” (from river runoff or N-fixation locally) but are regenerated by respired organic matter. “Marine snow” is sinking organic matter. Can be sampled in the water column with a sediment trap. Lecture 27 This lecture focused on the carbon cycle and the relationship between climate, carbon, and marine productivity. Data from polar ice cores shows that atmospheric CO2 goes up during interglacial periods and down during glacial periods (like the most recent, the Last Glacial Maximum). During glacial periods, more carbon is “pumped” out of the atmosphere and into the deep ocean (below the thermocline). During interglacials, this carbon is returned to the atmosphere. We investigated two “pumps” that account for this, solubility pump and biological pump. Industrialization and fossil fuel burning has caused CO2 to increase well above levels typical of an interglacial. We can see this in Mauna Loa CO2 record, which is continuous back to 1958. As much as half of the CO2 released by human activities has been taken up by the ocean, and it’s largely in the deep North Atlantic (via North Atlantic Deep Water production). The annual cycle in atmospheric CO2 concentration reflects the balance between photosynthesis and respiration (about ½ and ½ land vs ocean). The “pumps”: “Solubility pump” is chemistry and physics. CO2 dissolves in seawater, or is released by seawater depending on temperature, salinity, pH, carbonate chemistry (the chemical part). Dissolved CO2 is carried below the thermocline by deep water formation and brought back to the surface by upwelling. That’s the physical part. Temperature matters a lot (CO2 is more soluble in cold water) so polar regions tend to be sinks (CO2 removed from atmosphere to ocean) while equatorial regions tend to be sources of CO2 from the ocean to the atmosphere. “Biological pump” is uptake of CO2 by photosynthetic phytoplankton, and then “export” of that carbon to the deep ocean as marine snow (largely as fecal pellets produced by heterotrophs that eat the phytoplankton). The strength of this “pumping” will depend largely on availability of nutrients delivered to the photic zone. Most of the sinking carbon will be regenerated by heterotrophs (largely bacteria) living below the photic zone. Only about 0.1% of sinking organic matter actually makes it into sediment for long-term storage. HNLC (high nutrient – low chlorophyll) regions are parts of the ocean where there are high concentrations of nutrients (typically fixed N) at the surface. Plankton aren’t taking them up. Why not? Iron (Fe) limitation is the general explanation for HNCL regions. Seen in places far from land where there are no local sources to meet the small biological requirement for Fe. In these places small amount of soil “dust” may be the only source of Fe, and it doesn’t amount to much. Oceanographer John Martin (1990) “Iron Fertilization Hypothesis) proposed that lower atmospheric CO2 during glacial periods reflected a stronger biological pump as Fe limitation in HNLC regions is overcome by higher delivery of Fe from atmospheric dust. Some support for this hypothesis but there are other factors at play controlling glacial CO2. Martin’s ideas spurred a lot of interest in one type of “geoengineering”. Can we add Fe to Fe-limited parts of the ocean, stimulate productivity, boost the “biological pump”, and draw down some of the CO2 added to the atmosphere by industrial activities? The answer seems to be sort of. Fe fertilization experiments seem to result in increased productivity (i.e. a short term phytoplankton bloom) but the evidence for significant “export” of carbon is weak. The plankton mostly get regenerated in the surface ocean and CO2 is released back to the atmosphere. It’s not clear this type of geoengineering would help with the atmospheric CO2 problem and it faces a lot of opposition because it could have unforeseen negative consequences. Lecture 28 We talked about Stellwagen Bank, designated in 1992 as part of the US National Marine Sanctuary program, and whale feeding ground in our backyard (Massachusetts Bay). Stellwagen Bank is an important summer feeding ground for Humpback whales due to factors from all 4 branches of oceanography (geological, physical, chemical, biological) Geological: “banks” are shallow areas in the coastal ocean. We’re on continental crust here (continental shelf). While deeper areas of the shelf can be up to 500m deep, banks are 16:1 indicating strong nitrogen limitation here. Biological: tagged whales can be tracked and are seen feeding in waters exhibiting the “deep scattering layer” representing high abundance of zooplankton (and small fish) over the bank feeding on phytoplankton supported by upwelling nutrients Lecture 29 This was Prof. Buston’s lecture. This was really a research talk, so there is a LOT of information here that we don’t expect you to fully digest. You’re responsible for the highlights: Coral reefs are the among the most biodiverse marine ecosystems. Biodiversity refers to the number of marine taxa (fishes, invertebrates, etc) comprising the ecosystem. High biodiversity tends to be associated with ecosystem services (recreation, food in the case of coral reefs). Loss of biodiversity due to human activities is a concern for most marine ecosystems. One approach to conservation of marine biodiversity is establishment of a global network of marine reserves (protected areas). Metapopulation ecology: a metapopulation refers to a larger population (of fishes for example) made up of many local populations. A stable metapopulation is one made up of large numbers of individuals that are well connected. Understanding the connectivity of metapopulations is important to managing biodiverse marine reserves. This is what Buston’s lab is focusing on. Old assumption on connectivity of reef fish metapopulations: larval fish (zooplankton!) are carried thousands of km by ocean currents. Recent work on connectivity shows that most fish grow up on the reefs where they were born, and that dispersal drops off to zero over distance scales around 30-40 km. These dispersal patterns are refered to as kernals, and they vary between fish species. Prof Buston described his work trying to characterize the dispersal kernal for a Belize reef fish called Goby, which live in Bikini Bottom yellow sponges. Research protocol is to catch the fish, take a clipping of fin, measure the genotype (gene sequencing) to determine relatedness, match babies to parents. Results: median dispersal of babies only 1.7km, max 15km, consistent with newer ideas on reef fish metapolulation connectivity. One implication is that the “connected” series of marine reserves along the Belizian reef aren’t really connected, at least not for all reef fish. A possible conservation solution is to establish “stepping stone” reserves between the major reserves to connect them. Lecture 30 We looked at mid-ocean ridge hydrothermal vents and the communities they support. Like the Stellwagen lecture, the idea was to look at geological, physical, chemical factors that support the biology. First mid-ocean ridge hydrothermal vents were discovered in 1977 at the Galpagos Rift by a group from WHOI using the HOV Alvin. The vents themselves were not too surprising, the group was looking for them based on several previous observations: -measurements of very hot water in the Red Sea, along with colorful, metal-rich sediments. -early ocean drilling project cores showed such metal-rich sediment was consistently found directly on top of ocean crust basalt, suggesting origin near mid-ocean ridges. -Rocks dredged and cored from the Mid-Atlantic Ridge showed evidence of hydrothermal alteration, reactions between seawater and basalt rock at temperatures way above expected for deep sea. -Ophiolites, sections of ocean crust emplaced on land by convergent tectonics also contained high concentrations of metals (iron, copper) and evidence of high temperature water-rock interaction. -measurements of heat flow from ocean floor indicated that the ocean crust was cooler than expected simply from conductive cooling. Best explained by loss of heat to seawater through seawater circulation through the hot crust. What was very surprising upon discovery of seafloor vents was the biological community they supported. Clams, worms, crabs, bacteria, all independent of energy from the sun. Vents are the exit points for seafloor hydrothermal circulation. Seawater enters fractures in the ocean crust, is heated to 350-400°C by the magma below the ridge that supports mid-ocean ridge volcanic activity, reacts chemically with the rocks making up the crust, loses oxygen, becomes acidic, and collects H2S and dissolved metals, exits the crust in vents where this hydrothermal water mixes with water that is cold, oxygenated, high pH. These huge chemical gradients supply the energy that supports the seafloor ecosystems. The black “smoke” is metal-sulfide minerals that form when hydrothermal water mixes with seawater. The whole ocean gets circulated through mid-ocean ridge hydrothermal vents on a 10-20 million year timescale. This has a big effect on seawater chemistry, perhaps as important as the effects of rivers. Chemosynthesis is a process that uses energy from reaction between chemical components that are inherently out of equilibrium (H2S from vent fluid + O2 from seawater) to produce organic matter (sugars). Compare to photosynthesis, which takes energy from the sun to drive a reaction that produces chemical components that are out of equilibrium (organic matter and O2). Either way, the result is a food source for heterotrophs. Most famous members of the hydrothermal vent community are the tubeworm Riftia. It takes in H2S and O2 from the water, transports these to its gut (the trophosome) where symbiotic chemosynthetic bacteria live. The bacteria make sugar which the worm feeds on. Vents and vent communities are transient. A variety of measures indicates that they are active only for a few decades before the vent stops emitting hydrothermal water or shifts to a different location along the ridge. What about population connectivity then? How does the community move to the new location. Some work indicates that deep sea whale carcasses can serve as a temporary home as stepping stones moving towards new active vents. Decomposing whales release a lot of H2S! Lecture 31 Coastal ocean and coral reefs. Started by revisiting a few terms and defining a few new ones. Pelagic refers to the water column as opposed to Benthic, referring to processes and organisms that live in or on the sediment at the seafloor. Oceanic province is deep water, seaward of the continental shelf. Neritic province is the shallow ocean, inclusive of the continental shelf up to the low tide line (so always underwater) Littoral province is the part of the ocean that is between the high and low tide lines, so periodically underwater or exposed to air. Also called intertidal zone. The open ocean (oceanic province) tends to be biologically sparse because nutrient concentrations are low. Most of the life in the oceanic province is in the top 200 meters (Epipelagic zone) where there is light. The coastal ocean is full of life, lots of biodiversity and lots of productivity. Diversity is a result of large gradients in light, nutrients, temperature, tides, sediment, salinity, etc. Big diversity in ecosystem/community types in coastal zone too, including coral reefs, seagrass meadows, kelp forests (all neretic), beaches, tidal flats, mangroves, salt marshes (all littoral). Estuaries are coastal zones typically at the mouths of river where freshwater and seawater mix. Chesapeake Bay and Delaware Bay are two very large estuaries on the east coast of US, and there are many smaller estuaries up and down the coast including Massachusetts. Barrier islands are sandbars that develop seaward of the coast. Lagoons are quiet water environments behind barrier islands. The islands serve as storm barriers protecting the mainland. Movement of sand absorbs storm energy. In the US and elsewhere extensive development (condos, hotels) of these vulnerable landforms is an issue. We can divide benthic environments by high energy vs low energy. Mostly dependent on water depth, does wavebase intersect bottom? But you can also find low energy environments in shallow water when protected by barriers. Benthic communities differ based on substrate: hard-bottom vs soft-bottom Muddy soft-bottom communities have more deposit feeders. Sandy soft-bottom communities have more filter feeders. Hard-bottom communities feature seaweeds, filter feeders, grazer, predators Coral reefs are high energy, neritic, hard bottom benthic communities Found in warm water, so usually between 30°N to 30°S, full salinity, clear water, shallow. Corals are sensitive to sediment, nutrient loading, acidification, temperature. Coral reefs are changing rapidly due to these pressures. 50% of tropical reef coverage lost since 1950. Most dramatic mechanism is “bleaching” where high water temperature causes corals to eject zooxanthellae (colorful symbiotic photosynthetic dinoflagellates). Solitary (non-reef building) corals are found in colder waters, including New England. These are of interest to biologists because they are more resilient, and some are capable of living either with or without zooxanthellae. Corals are animals, related to jellyfish. A coral reef is built by colonies of individual corals known as polyps. Polyps secrete calcium carbonate, building the hard reef structure over time. The calcium carbonate structure that the polyp sits in is called a corallite. The polyp has tentacles that capture food (mostly small zooplankton) and deliver it to the gut. The tentacles have stinging cells (nematocysts) as do jellyfish. Coral reefs are large platforms built up of calcium carbonate (limestone) over thousands of years. The reef-top is flat and shallow (5-10 meters). The reef face drops off into much deeper water. The reef grows upward keeping pace with rising sea level. Individual polyps lift off of their corallite bases, secrete new CaCO3, elevating the reef. There are several additional slides at the end of this lecture deck that I didn’t cover in class and won’t test you on, but worth looking at if you want a fuller picture of coral reefs, especially the videos! Lecture 32 Cat’s coastal biogeochemistry lecture Lecture 33 Sea level Lecture 34 Climate change and mitigation