Time to consider the shallow-marine environment and the impact of human activities on the critters that live there. Yes, we want to inject a bit about marine biology and ecology into this course, so this is a beginning. In this Lesson we will explore "Dead Zones" and "Bleached Reefs" and evaluate their causes and consequences. We will cruise around a bit, spending some time in the Caribbean Sea on coral reefs, floating out the mouth of the Mississippi River to visit the "dead zone" along the coast of Louisiana, and then sailing up Chesapeake Bay to examine hypoxia there, and, finally, checking out "red tides" off the coast of Florida and Massachusetts. Actually, we'll visit the dead zones first and spend quite a bit of study on Chesapeake Bay. After all, if you like oysters, crabcakes, striped bass and the like you should be concerned about the health of that water body.
By the end of Lesson 7, you should be able to:
As you work your way through these online materials for Lesson 7, you will encounter additional reading assignments and hands-on exercises and activities. The chart below provides an overview of the requirements for this Lesson . For assignment details, refer to the lesson page noted.
Lesson 7 will take us ten days to complete.
LESSON 7 |
||
REQUIREMENT |
LOCATION |
SUBMITTED FOR GRADING |
Activity 1: Chesapeake Bay hypoxia |
page 3 |
Yes- Word file with answers to queries, post blog to discussion area Target deadline: Apr 11th |
Activity 2: Dead zones |
page 4 |
Yes- Word file with answers to queries, post comments and compare/contrast writeup to discussion area. DUE: Apr 14th |
Activity 3: The calcification problem! | page 7 |
Yes - Submit this assignment to the appropriate dropbox DUE: Apr 14th |
If you have any questions, please post them to our Questions? discussion forum (not e-mail), located under the Communicate tab in ANGEL. I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.
Figure 1-1: A "red tide" off the coast of Washington state (source: Buckner, serc.carleton.edu)
We could have subtitled this the "doom and gloom" lesson. Because, yes, it does seem that the future of the marine realm is troubled in a variety of ways. In thinking about the problems facing our oceans, one could consider this quote from Mahatma Gandhi..."you must not lose faith in humanity. Humanity is an ocean; if a few drops of the ocean are dirty, the ocean does not become dirty." This works on various levels, don't you think? We can have hope for the future...alas, more than a few drops of the ocean are dirty now, especially the coastal ocean. Humans have too long thought that "dilution is the solution" to waste products, and we have allowed too much of our waste to escape down rivers and through the atmosphere to accumulate in the ocean and in oceanic sediments. It would appear that we are beginning to pay the price for our profligacy and neglect. Can we make amends? We hope so, right? In educating our youth we do not want to leave them with the impression that "all is lost," "we're hosed," the "system is kaput," etc. On the other hand, it is essential that everyone understand what is going on and what may come in the future.
What are the major environmentally related issues facing the ocean today?
1) many coral reefs are affected by various bacterial and viral diseases that appear to have spread over the past decade or so, impacted by warming of waters (global warming?) beyond the tolerance of corals, which may be the major cause of "bleaching," and, a potential threat to their ability to form skeletons because of the buildup of carbon dioxide in the atmosphere and ocean.
2) "red tides", (sometimes referred to as HABs--harmful algal blooms) dense blooms (not in the flowering sense, but in numbers) of toxic phytoplankton (near surface-dwelling, single-celled photosynthetic floating organisms) are appearing in estuaries, bays and coastal regions. These organisms, typically dinoflagellates, secrete neurotoxins that can accumulate in certain marine organisms (e.g., raw oysters! mmmmmm!) that some humans love to eat, and will cause paralysis or death if consumed. They also cause other problems for the normal marine biota that we will examine later. Red tides have been known for decades, but their frequency and distribution is increasing rapidly.
3) "dead zones" and "hypoxia," regions of estuaries, bays and even the open continental shelves that suffer from oxygen deficiencies. Extreme low oxygen concentrations eliminate benthic organisms (e.g. clams, scallops) and reduce habitat for oysters, crabs, fish and the like. These "dead zones" are likely caused by a surfeit of nutrients, excessive plankton blooms, restricted mixing of surface and deeper waters, and high rates of oxygen consumption by bacteria that break down the falling organic matter. These areas seem to be increasing in number and expanding.
4) oil spills and leakage that harms waterfowl and marine mammals (e.g. the Exxon Valdiz incident). We will not cover this issue in the course. Double-hulled oil transport vessels seem to be the main solution to this issue (that, or stop using oil and gas...?).
5) overfishing and a "jellyfish ocean". This is discussed in the Lesson on fish and fisheries.
These issues (and their possible solutions) are covered in two relatively recent books using the theme "Ocean's End."
We recommend both: Ocean's End by Colin Woodward (2001) is a bit depressing but graphic, whereas Defying Ocean's End (2004) by Linda K. Glover, Sylvia A. Earle (a real force in marine science and diving), and Graeme Kelleher gives the "agenda" for approaching the problems. Also, visit the "Defying Ocean's End" [1]wikipage for other details and updates.
Let's jump right into the Chesapeake Bay story as an example of issue #3 (and #2 to some extent).
Figure 3-1: The Chesapeake Bay watershed and land use map (source: www.whrc.org [2]). Do you live in the watershed?
By way of introduction, please view the power point presentation [3] on the problem of dead zones, hypoxia, eutrophication and the health of Chesapeake Bay. Then go to the assignment below to flesh out your knowledge.
We think that this is a great focus for teaching about the oceans, at least for teachers in the northeastern US, because it is "local," has food chain connections, and involves so many aspects of physical oceanography, nutrients and primary production, marine animals, environmental issues, fisheries--you name it! And, there are so many resources and data sets available for students to work with.
After reading the first assigned article (Brattonetal2003 [4]), which provides an historical overview of Chesapeake Bay hypoxia on the basis of the sedimentary record, and examining the power point presentation above, answer the following questions (in a file to be uploaded to the Angel DropBox). You may simply provide a list of elements, when appropriate. Elaborate if you like. Numbers 6 and 7 will be a basis for discussion, so that will be posted in the "Comments" box below.
For numbers 1 through 5, please put your answers in a file and drop that in the dropbox on Angel.
For number 6 and 7, use the comment box below.
Save your document as either a Microsoft Word or PDF file in the following format:
L7_Activity1_AccessAccountID_LastName.doc (or .pages or .pdf)
For example, student Elvis Aaron Presley's file would be named "L7_Activity1_eap1_presley.doc".
See the grading rubric [8] for specifics on how this assignment will be graded.
Figure 3-1: Wow, note the documented incidences of coastal hypoxia (source: static.guim.co.uk/sys-images/Environment/Pix/pictures/2008/08/14/ocean-map.jpg) as of 2007/8.
Ok, so far you know a bit about hypoxia and dead zones on the basis of your exploration of Chesapeake Bay. In this section, we will explore the Gulf of Mexico "dead zone" a bit more, with a short activity to follow. Go here [9] (the "Blistered Orb Climate Blog") for some links to news items regarding the expansion of "dead zones" (in number and area; related to Fig. 3-1); you will have to scroll down and click on 8.14 and 8.15 which relate to a 2008 Science magazine article--you can read the abstract of the article below, but the news items provide an overview and some quotable quotes. Here's a website [10] (NASA ocean color) that shows satellite imagery of some representative zones with a bit of explanation. And this NOAA [11] website has an interesting historical focus and research plan, including "Public Comments" regarding policy issues (check them out--the public comment period closed in 1999, but some very interesting debate there). If you look these over carefully, you should be able to go to Activity 2. You will now be quite an authority on "dead zones."
Science 15 August 2008: |
Robert J. Diaz1* and Rutger Rosenberg2
1 Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA.
2 Department of Marine Ecology, University of Gothenburg, Kristineberg 566, 450 34 Fiskebckskil, Sweden.
This is the scientific paper published in 2008 by Vaquer-Sunyer and Duarte in PNAS suggests that the severity of hypoxia controls diversity of benthic marine organims and that there are different thresholds for different groups (like we showed in the slideshow for CB at the beginning of this lesson). After reading this short but pithy paper, take on Activity 2.
A and B should be submitted to the DropBox on Angel
A) You have read this PNAS paper. In your own words, summarize the principal points they made and their significance. Do this in less than 100 words.
B) Answer the following questions
1) What do the "L50" parameters mean and what is the "threshold" for low oxygen tolerance?
2) Which organisms are most susceptible to oxygen deficiencies? Least?
3) What strategies can different organisms use to cope with oxygen deficiency? Does this influence their susceptibility as listed in question #2?
C) Provide a paragraph that briefly compares and contrasts the causes and effects of hypoxia in Chesapeake Bay with that in the Gulf of Mexico "dead zone." Post this in the discussion forum below and comment.
See the grading rubric [8] for specifics on how this assignment will be graded.
Figure 4-1: Red tide composite for west Florida red tide in 2003 (source: NASA). It really does color the water.
Have you ever been told "don't eat seafood in months without an "r"? As kids, many of us were told that but never really knew why. Turns out, that the summer months are typical "red tide" months and raw seafood consumption was not a good idea because of PSP (paralytic shellfish poisoning). In fact, California has a state law that allows substitution of punched "ray" fin for scallops in restaurants during those summer months without notifying the consumer for that reason.
Are "red tides" and PSP bad? Well, examine this map [13] and you will see that the incidence of PSP has spread considerably with red tides. Take about a half hour to pore over this fairly self-explanatory slideshow [14] about plankton ecology and HABs (harmful algal blooms). This should give you what you need to understand the food web discussion in Lesson 8, and all about the requirements of photosynthesis in the sea and why nutrients are important and, at times, problematic. Plankton may be responding to global change as indicated in Summary that appeared in Science magazine [15].
There are more resources on HABs on the last page of this Lesson. Any questions? Go on to Coral Reefs!
Figure 6-1: satellite image (source: NASA) of Grand Bahamas Bank, showing islands (brown), shallow marine platforms (light blue to turquoise) and deeper water passages (darker blue). Cuba is just to the SW in this image. There are coral reefs at the edges of platforms.
Figure 6-2: Kure Ikonos, an atoll in the North Pacific (NASA photo) completely surrounded by a fringing reef of coral.
Coral reefs are widespread today in low latitude oceans where mean annual temperature and/or minimum temperatures at the sea surface (SST) are above 20°C. The coral platforms typically form fringing reefs and are barriers to wave energy. In the continental US, our only significant reefs are in the Florida Keys. Perhaps you have visited and snorkled on some of these reefs in Pennecamp State Park. The Hawaiian Island chain also hosts some spectacular reefs, which are, on some island margins, highly pristine.
But, as stated at the outset of this lesson, coral reefs nearly everywhere are imperiled, if not because of boats running aground and or anchoring on them then because of waters that are at times too warm and because of viral and bacterial diseases that are able to take advantage of these stressed organisms. In some cases, too much sediment and nutrients choke out corals and or promote overgrowth of green algae that block sunlight to the coral animals and their essential algal symbionts (stay tuned to learn a bit about these). These reefs are critical elements of the ecosystem, hosting a highly diverse animal and marine plant population as well as protecting adjacent coastal lagoons and and areas from erosion and damage by waves. The shallow oceans would seem sterile and, well, even ugly without them. Take a look at Figure 6-3, for example that shows a reef that is denuded due to disease and algal overgrowth.
Figure 6-3: algal overgrowths on reef, possibly resulting from excess nutrients. Coral reefs prefer rather low nutrient waters and are out competed by non-calcareous algae when nutrient levels rise.
At any rate, before we go any farther, you should check out this short slideshow [16] that will familiarize you with general elements of coral reefs today. There are maps of their distribution and photographs of corals and coral diseases. We recommend that you check out a DVD of "The Blue Planet" [17] (this has a segment of the "coral seas" section) which has some spectacular images of corals, their habits and habitat.
Figure 6-4: One of our students doing "Reef Check" in San Salvador, Bahamas. We periodically take students with dive training and certification (PADI) here at Penn State to San Salvador for studies of the health of selected reef sites around the island.
So, assuming you have looked at the slideshow as suggested, let's go on to the next section for some interesting (we hope) consideration of the interaction between atmospheric chemistry, the oceans and coral reefs. Another connection to "global warming" with a twist.
Figure 7-1: a shot of part of the HUB aquarium at Penn State in which there is a living, thriving coral "reef". Come visit!
Yes, even at landlocked Penn State, we have a piece of shallow-marine environments, right in the midst of the bustle of the Hetzel Union Building (HUB) on campus. Thanks to the class of '99, a dedicated faculty member from Chemistry and a string of dedicated students this aquarium and its denizens continue to thrive. Here [18] is a brief article about the aquarium (2002) with pictures. One of the things learned in maintaining such small ecosystems is the need to buffer changes in certain chemical substrates, particularly dissolved carbon, pH and Calcium ions, all of which are essential to allowing corals to precipitate their aragonite (CaCO3) skeletons. The aquarium maintains a bed of granulated limestone through which fluids are circulated before they enter the tank. This allows some of the limestone to dissolve, if needed, contributing the essential Ca2+ and CO3-2 ions for incorporation by growing, skeletonizing corals. The chemical reaction would be:
Ca2+ + CO32- ----> CaCO3(s) (aragonite) (this reaction is, of course governed by a temperature-sensitive equilibrium "constant")
As you learned in the marine chemistry lesson, solutions must be at or above saturation with respect to a given mineral to allow it to precipitate. Inadvertently, however, we are beginning to lower the level of saturation of the surface ocean with respect to aragonite, and this will make it more difficult for corals and other aragonitic organisms to precipitate shells or skeletons. How does this work?
First, you have probably seen various versions of Figure 7-2.
Figure 7-2: (source: NOAA) Concentration of carbon dioxide in the atmosphere (parts per million; ppm) from 1958-2008 from monitoring atop Mauna Loa on Hawaii.
This record illustrates an increase in the average (the little wiggles are seasonal variations) pCO2 (partial pressure of carbon dioxide in the atmosphere) of about 19 percent over the past half century. Of course, it is this increase that global warming has been attributed to, but there is another issue. Even if we could mitigate global warming by some engineering miracle (mirrors in space, etc.), the increase in pCO2 would probably ultimately get the corals. Why? Because the increase in pCO2 and its penetration into the ocean surface lowers the pH of the ocean, decreasing the carbonate ison concentration and, ultimately, decreasing saturation with respect to aragonite. Figure 7-3 shows how this works with some simple calculations by doubling pCO2.
Figure 7-3: (source: NOAA/PMEL)
Note that through reactions shown (carbonic acid equilibria in seawater) doubling pCO2 from its pre-industrial level (280 ppm) to 560 ppm substantially decreases pH (by 0.24 units) and carbonate ion concentration (by about 34 %); of course, we have not gotten to that point--yet! Note, however, that atmospheric CO2 derived from fossil fuels (how do we know this?) has mixed down into surface waters and penetrated deeper into the ocean (remember the deep circulation?) in some regions as shown in Figure 7-4. This is causing a decrease in pH.
Figure 7-4: (source: Scientific American, 2006).
Chris Langdon (Lamont Doherty Earth Observatory, Columbia University) grew corals artificially in Biosphere 2, Arizona and subjected them to different pCO2 levels. He found that their growth rate decreased with increasing pCO2 as shown in Figure 7-5.
Figure 7-5: calcification rate (precipitation of aragonite) of corals in seawater at constant temperature as a function of atmospheric pCO2 in Biosphere 2 (closed system) experiments performed by Chris Langdon (LDEO). Note decreasing rate of calcification and benchmarks for the future. It looks as though the corals may already be having trouble, at least relative to the pre-industrial world. What do you think?
Let's take some time to reflect on what we've just covered on coral reefs! Here we want you to think about how you would help students understand the principles underlying the conclusion that corals are in trouble because of increasing carbon dioxide concentration in the atmosphere. The underlying chemical equilibria are complex, but must be understood at some level in order to be able to analyze and accept the scientific conclusions. Who or what are we if we take others word alone for such things, or dismiss it because we cannot understand it?
We want you to read and study the following two accessible and (reasonably) short semi-technical papers about the problem of "ocean acidification" and its consequences:
Kleypas and Langdon (2003) Conference Proceedings Summary [19]
Doney (2006) Scientific American [20]
These should give you a feeling for the background, chemical principles and uncertainties in drawing conclusions about the developing trend in ocean acidification.
We then want you to:
1) Outline your strategy for teaching high school students about
ocean acidification. Let's say you have one class period (one
lesson?) to do so. What resources do you need and what can you
assume they already know? For example, will they have learned
about chemical saturation, or...? Could you think of an experiment that
would help with this? Ok, we'll give you (virtual) glassware, some
powdered aragonite, some artificial seawater, a pH meter, and a small,
pressurized tank of carbon dioxide. Design a fairly quantitative
experiment to convince the students that this ocean acidification thing
can happen. What could you do, how would it be quantified?
Put this in a Word file and drop it in the Angel dropbox
2) Yes, the second activity is the dreaded blog...write a 600-word blog on ocean acidification that will engage, interest, and educate the general public. [As an aside: Could your students do this given the same introduction to the topic? How many could/would go home and tell their parents about this issue?]. Post your blog to the discussion area and engage in some editing for others to help improve their stories. I might call mine "It's the Acid Truth" or maybe (apologies for the profane, but I could not resist the visual pun...I'm really sorry, maybe I should remove this, but...)..."pHuking Around with Seawater"
You will be graded on the quality of your participation. See the grading rubric [8] for specifics on how this assignment will be graded.
Have another reading or Web site on these topics that you have found useful? (Or, if you were offended by Mike's edgy, profane pun on the previous page) Share it in the Comment area below!
What can we say? If you are here, you must think that you are done. You are, after you follow the advice below. You are about 7/9ths through this course. Hope you are having some fun. Tired of doom and gloom? Wait until Lesson 8! Hope you don't like seafood!
You have finished Lesson 7. Double-check the list of requirements on the Lesson 7 Overview page to make sure you have completed all of the activities listed there before beginning the next lesson.
If you have anything you'd like to comment on, or add to, the lesson materials, feel free to post your thoughts below. For example, what did you have the most trouble with in this lesson? Was there anything useful here that you'd like to try in your own classroom? Is climate change a topic you and your students are interested in? Do your students have much interest in or opinions about the politics/science of global climate change?
Links:
[1] http://en.wikipedia.org/wiki/Defying_Ocean's_End
[2] http://www.whrc.org
[3] https://courseware.e-education.psu.edu/courses/earth540/priv/ChesapeakeBayShow.ppt
[4] https://courseware.e-education.psu.edu/courses/earth540/priv/Brattonetal2003ChesEutrop.pdf
[5] https://www.e-education.psu.edu/files/earth540/file/Envbroch.pdf
[6] http://www.chesapeakebay.net
[7] http://www.cbf.org
[8] https://www.e-education.psu.edu/earth540/grading_rubric_problemsets
[9] http://blisteredorb.blogspot.com/2008/08/climate-review-august_16.html
[10] http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ocean-color/dead_zones.shtml
[11] http://oceanservice.noaa.gov/products/pubs_hypox.html
[12] https://courseware.e-education.psu.edu/courses/earth540/priv/PNAS-2008-Vaquer-Sunyer.pdf
[13] https://www.e-education.psu.edu/files/earth540/file/PSP_1970-2006_47919_jpg (JPEG Image, 600x700 pixels).pdf
[14] https://courseware.e-education.psu.edu/courses/earth540/priv/HABs.ppt
[15] https://courseware.e-education.psu.edu/courses/earth540/priv/SmetacekandCloernScience2008.pdf
[16] https://courseware.e-education.psu.edu/courses/earth540/priv/CoralReefReview.ppt
[17] http://dsc.discovery.com/videos/blue-planet-coral-seas-reef-at-night.html
[18] http://www.advancedaquarist.com/2002/10/aquarium
[19] https://courseware.e-education.psu.edu/courses/earth540/priv/seawaterchemcorals.pdf
[20] https://courseware.e-education.psu.edu/courses/earth540/priv/doney_sciam_2006.pdf
[21] http://www.gulfhypoxia.net/
[22] http://www.whoi.edu/page.do?pid=11913
[23] http://www.ocean-acidification.net/
[24] http://geo.arc.nasa.gov/sge/coral-health/
[25] http://reefcheck.org/default.php