Using Long-Term Data From Antarctica to Teach Ocean Acidification

There is a mystery to be solved! This lesson plan asks students to identify the Who, What, When, Where, Why, and How of ocean acidification (OA). Global oceans have absorbed approximately a third of the CO2 produced by human activities, such as burning of fossil fuels, over the past decade (Sabine et al. 2004). This accumulation of CO2 in the ocean has lowered average global ocean pH and decreased the concentration of carbonate ions (CO32-) (Fabry et al. 2008). As a result of this OA, the carbonate chemistry of the global ocean is rapidly changing and affecting marine organisms (Orr et al. 2005). Pteropods (open-ocean snails) are considered bioindicators of OA due to the vulnerability of their aragonitic shells dissolving under increasingly acidic conditions from a changing climate (Figure 1) (Orr et al. 2005; Bednarsek et al. 2014). This lesson plan can be found at: >https://www.vims.edu/research/units/centerspartners/map/education/profdev/VASEA/lessons.php .


INTRODUCTION
There is a mystery to be solved! This lesson plan asks students to identify the Who, What, When, Where, Why, and How of ocean acidification (OA). Global oceans have absorbed approximately a third of the CO 2 produced by human activities, such as burning of fossil fuels, over the past decade (Sabine et al. 2004). This accumulation of CO 2 in the ocean has lowered average global ocean pH and decreased the concentration of carbonate ions (CO/ ) (Fabry et al. 2008). As a result of this OA, the carbonate chemistry of the global ocean is rapidly changing and affecting marine organisms (Orr et al. 2005). Pteropods (open-ocean snails) are considered bioindicators of OA due to the vulnerability of their aragonitic shells dissolving under increasingly acidic conditions from a changing climate (Figure 1) (Orr et al. 2005;Bednarsek et al. 2014). This lesson plan can be found at: https://www.vims.edu/research/units/centerspartners/ map/education/profdev/VASEA/lessons.php.
The Southern Ocean is particularly vulnerable to OA because it is more chemically sensitive to increases in anthropogenic CO 2 and is projected to become completely undersaturated with aragonite by 2100 (Doney et al. 2009). The ongoing Palmer Antarctica Long-Term Ecological Research (PAL LTER) study, which began in 1993, monitors how environmental changes, such as OA are significantly affecting the marine ecosystem including pteropods (Figure 2; Thibodeau et al. 2019). Students will utilize real long-term data collected by the PAL LTER to learn about OA.
OA is a pertinent topic when discussing the general concepts of seawater chemistry as well as broader topics including climate change and human impacts. Hence, this lesson plan uses OA as a method to apply more traditional chemistry concepts (i.e., solubility, acids-bases) within the context of global climate change. The lesson focuses on a case study in Antarctica and the potential effects of OA on an open ocean plankton, the pteropod (tero-pod) species Limacina helicina antarctica, whose shell is easily dissolved in ocean acidification conditions. With this lesson plan, students will be able to : 1.) outline ocean chemistry processes; 2.) identify key points of Antarctic geography and biology of polar species; 3.) synthesize scientific information from the internet and reproduce in their own words; 4.) record and graph real scientific data using excel; and 5.) interpret graphs and make predictions about future trends based on graphical information.
The lesson plan is approximately 135 minutes or three, 45-minute classes. The different components of the lesson plan can be easily differentiated and function independently as mini-lessons if the full 135 minutes is not available. Content is intended for grades 9-12 but can be modified for use in grades 6-8. The lesson achieves Next Generation Science Standards including 1.) Earth and Space Science standards HS-ESS2-2 Earth's Systems, HS-ESS2-4 Earth's Systems, and HS-ESS3-6 Earth and Human Activity; 2.) Life Sciences standards HS-LS2-2 Ecosystems: Interactions, Energy, and Dynamics and HS-LS4-6 Biological Evolution : Unity and Diversity; and 3.) Physical Sciences standards Chemical Reactions HS-PSl-5 and HS-PSl-6. The class will begin with an OA gallery walk in which students work in pairs or small teams to scan QR codes with iPads/ iPhones. Students will be directed to visit specific websites and record their findings on a provided worksheet and then report their findings as a class. This starter activity will cover the "What is ocean acidification?" (Figure 3). This activity is suitable for grades 6-12.
The teacher will then show a presentation to review the concept of OA (What and When) and explain Why OA is happening. The presentation also discusses OA in Antarctica and how it could affect a species of pteropod, Limacina helicina antarctica (Where and Who) (Figure 4).
The major component of the lesson plan is a data nugget activity in which students will answer the question, "How is OA happening?" (Figure 5). For higher level classes, students can graph these data on their own using the provided teacher's guide. For lower level classes, teachers can provide students with the premade graphs available within the lesson plan for them to interpret. Data are sourced from the PAL LTER publicly available data archive : http://pal.lternet.edu/data. Class will conclude by students reviewing the 5 W's of OA with a think-pair-share activity ( Figure 6). By learning about important scientific concepts related to oceans and utilizing real scientific data, students will better understand the processes governing our oceans and be prepared in answering important scientific and societal questions. ... ,~--  Temperature (left y-axis) and pteropod abundance (right y-axis) both oscillate overtime (x-axis) with moderate summertime temperature ( ~ 1 °C) corresponding to higher pteropod abundance (A). Aragonite saturation (left y-axis) and pteropod abundance (right y-axis) also oscillate overtime (x-axis) with high aragonite saturation corresponding to high pteropod abundance (B). We would expect to see this positive relationship between aragonite saturation and pteropod abundance because aragonite is the building block of pteropod shells. Introduce some of lhese wo,ds In the t<>acher graphioe demo: oscillatine. varylne., variability.
The!>e are c:-omrnon voe: bu ta,v (o descri~ Lronds in t1me----seoe:s da ta. Students should identify vea f s of high/low pteropod abundance In relation to the graphlnQ variable.
b. What oou ld be your independent and independent va riables? Why? current Discuss wh-y pteroi>0d abundance al"'ld the environmental variable are both dependent va riables (answer: they' re both varying as a tul'lc.tlon of time, the i ndependent variable). To expand upon lhls que,$llon and add ii higher order of lhinking, ask $\udenls how they would Interpret a graph of ptcropod abundance v.s . cnvlronmcmal v,niable (ariswer: ptcropod would be depcndcn varfdble beuus.e we1re i:l!iSurn1og that the envnonmental v.1ri.tble m.ty be controlling pteropOd ,1bundance in some wayJ , Th is concept could also be ex~nded to address correlation by as.kine s.tudents to graph these variables against each other, graph a trend line, .and calculate a correlation coefficient.
c. AP LEVEL ONLV: Whal ways could you graph lhese data? Wha t type of graph bes·1 shows the data? Whv?
This question is getting at lhe type of graphs us~d to interpret data. Ask studen1s why lhey were asked to make a combi11ation plot of lhe va riables rather than tw'o bar graphs or two-lioc plots (answer: w.ant to :show data .JS clearly as possible, when two lines are used it c.an be diffiC"ull to pilna apart the two variables, especially if rhey are h1ghty variable). To expand upon lh is ques1i-on, <;1sk j l ui;ients 10 p lav oilround wit h dlffert>nl gr.;1phing optlons nd makt> a 'bettE'r' gr,1ph th,1n tho orisin.i l one presc-nted. What m~kes it better? Is thNc one rieht way to present data araphicallv (answer: nol).

FIGURE 6.
Subset of differentiated discussion questions from the Teacher's Guide with suggested answers in red. Discussion questions can be shared with students as a class or as a thinkpair-share activity.