Project Abstract

<p>&nbsp;            <b>ABSTRACT</b></p><p>&nbsp;Palynology is the study of fossil pollen and spores, and these tiny grains can provide fundamental information about past climates on Earth. Among their many unique and useful properties, pollen and spores are composed of some of the most chemically resistant organic compounds found in nature. They are also produced in vast quantities and are unique to the specific plant from which they originate. All these features make them ideal to reconstruct past climates from both recent history as well as from the ancient past. The purpose of this activity is to get students familiar with palynology and how scientists study climate change. It is based on real palynological data acquired from Antarctic cores obtained recently from the ANDRILL and SHALDRIL drilling campaigns. In order for students to understand this research and its importance, they will separate and identify pollen and spores from a simulated core sample in which different species of plants are represented as different colors of glitter. Students will compare the types and abundance of pollen and spores found in each layer of the core sample and research the climate preferences of the types of plants recovered in order to reconstruct the past climates of Antarctica. KEYWORDS biology, climate, data analysis, Eocene, geology, Miocene, Oligocene, pollen <br></p>

Project Overview

<p> <b>1.0 INTRODUCTION&nbsp;</b></p><p>An ancient mystery awaits us underneath thousands of meters of ice, water, and rock. The clues to unraveling this mystery are hidden in tiny microfossils that have been buried in sediments for millions of years. The study of these fossil pollen and spores is called palynology (pronounced \pal-uh-NOL-uh-jee\), and these tiny grains can provide fundamental information about past climates on Earth. Pollen and spores are particularly useful for the reconstruction of past climates because&nbsp;</p><p>• They are composed of some of the most chemically resistant organic compounds found in nature. Their outer wall is remarkably resistant to microbial attack, to temperature and pressure from burial underground, and to acid digestion.&nbsp;</p><p>• They are produced in vast numbers&nbsp;&nbsp;&nbsp;</p><p>&nbsp;• They are unique to a specific plant, so scientists can make ecological and environmental inferences about the area where they were found.</p><p>&nbsp;• The majority of pollen and spores produced travel and settle rapidly due to their small size. They are ubiquitous in all environments where plants grow but can also be found offshore if carried by rivers, and to a lesser extent, by wind.&nbsp;</p><p>The following activity is based on the latest palynological data from the SHALDRIL (SHALlow DRILling) and ANDRILL (ANtarctic geological DRILLing) projects, which obtained sediment cores from Antarctica that date back to the Eocene epoch as many as 56 million years ago (Ma). This contrasts from existing palynological activities that use pollen data from much younger lake sediments (less than 20,000 years old) and are thus limited to climate reconstruction for the recent past (e.g., Henderson, Holman, and Mortensen 1993). This proposed activity is the only palynological activity focusing on the Antarctic continent. In order for students to understand ongoing Antarctic research and its importance, they will separate and identify pollen and spores from a simulated core sample in which different types of pollen grains are represented as different colors of glitter. Fine glitter is used in order to more accurately represent the size of the pollen grains and the general abundance of these grains recovered from sediment cores. Students will separate the glitter in their sediment samples using methods meant to simulate how palynologists extract pollen from ancient cores (e.g., dissolution and sieving). Last, students will reconstruct the past climates of Antarctica by comparing the types and abundance of the “pollen” found in each layer of the core sample using statistical analyses, thus improving their math and analytical skills. This activity meets several objectives in all three of the dimensions in A Framework for K–12 Science Education (National Research Council 2011). Planning and conducting investigations, using mathematics and computational thinking, analyzing and interpreting data, and communicating information are important scientific practices stressed in this new framework, and all are emphasized in this lesson plan. Crosscutting concepts such as systems and models, stability and change, and patterns are also clearly represented through this activity. The third dimension of the Framework consists of the core disciplinary ideas. Important concepts in the Earth, life, and physical sciences are also addressed through these activities, such as climate change and the Earth’s history, evolution and diversity, and interactions of matter.&nbsp;</p><p><b>1.1 BACKGROUND</b></p><p>&nbsp;The fossil record indicates that the climate has continuously changed over time throughout Earth’s history. For example, time periods such as the Last Ice Age (Wurmian) and the Age of Dinosaurs were dras- ¨ tically different climatically. Because many plants are known to live in particular habitats with specific temperature and rainfall patterns, paleobotanists can make inferences about past climates based on the plants that were living at a geologic or archaeological site at that time. For example, if evidence of an abundance of cacti is found in an area, it can be inferred that the climate was hot and dry, but if gigantic ferns are found along dinosaur bones, it implies that the climate at that time was hot and humid. How do paleobotanists know what types of plants lived in a past environment? Fossils of leaves and trunks would provide excellent clues, but the leaves or trunks are not often found because they decay and, if sedimentary conditions are right, the organic material turns into oil, gas, or coal after being buried for millions of years. Since pollen and spores are very resistant to decay, produced in great abundances, and morphologically unique to each plant, palynologists can isolate and identify the pollen and spores found in sediment cores taken from lakes, riverbeds, and coastal sea beds. Pollen is deposited in the sediments in layers, with the oldest layers found at the bottom and the newer layers on top—–this is known as the law of superposition (see Tedford and Warny 2006, for a related activity on this topic). Geologists have been coring the Earth’s surface layers for centuries to learn about past environments. As mentioned earlier, a thorough Internet search will provide a few examples of activities that use pollen data from more recent lake sediments (e.g., Henderson, Holman, and Mortensen 1993), but the latest frontier to study is Antarctica. To delve further into the past climates of this continent, a consortium of scientists and drillers, along with educators and students from several countries, formed the ANDRILL project (http:// andrill.org), which drilled a sediment core 1,200 m long from beneath the McMurdo Ice Shelf.&nbsp;</p><p>The ANDRILL sediment cores pictured in Figure 1 show layers of Miocene-age rocks that were sampled from below the Ross Sea. Prior to that, the SHALDRIL project drilled in the Antarctic Peninsula; Figure 2 is an artistic&nbsp;</p><p>FIGURE 2 SHALDRIL drilling operations from the RV/IB N.B. Palmer, cutting into the Eocene-age sediments (artwork by A. Fox and S. Warny) (color figure available online).&nbsp;</p><p>TABLE 1 Comparison of the ANDRILL and SHALDRIL Projects ANDRILL SHALDRIL Geography McMurdo Ice Shelf Antarctic Peninsula Drilling method From boat (ice cutter) From platform on ice shelf Age of core sediments Miocene Eocene, Oligocene, Miocene, Plio-Pleistocene References Warny et al. 2009; Feakins, Warny, and Lee 2012 Anderson et al. 2011; Warny and Askin 2011a, 2011b dering of this drilling operation. A comparison of these projects is shown in Table 1. Once a sediment core is obtained, it is sampled every millimeter, centimeter, meter, and so forth, depending on the time frame a palynologist is studying. Some lake cores are examined every millimeter to look for yearly changes, whereas a large core such as from the ANDRILL project may be sampled only every five meters to look at changes on a millennial scale over millions of years. Each sample is dissolved in strong acids (HCl and HF) to remove unwanted particulates such as sand and mud, washed with distilled water, and run through sieves to concentrate microscopic fossils. If needed, a flotation technique can be used to separate particles of the same size but of different weights. The residues left over—–mostly composed of palynomorphs, e.g., pollen, spores, dinoflagellate cysts—–are mounted on microscope slides and examined under high magnification to identify the types of pollen grains and spores. The relative abundance of each type of palynomorph is charted on a pollen diagram to look for patterns of change over time.&nbsp;</p><p><b>1.2 MATERIALS&nbsp;</b></p><p>• 1 L graduated cylinder or other tall container to make a sample sediment core&nbsp;</p><p>• Sand (use coarse sand that will sink, such as play sand sold at hardware stores)&nbsp;</p><p>• Salt&nbsp;</p><p>• Dark brown sugar (in a color easily distinguished from the sand)&nbsp;</p><p>• Coarse grain sugar, such as “raw sugar”</p><p>&nbsp;• Fine glitter in six colors: red, green, gold, blue, purple, and black (colors can be substituted as long as they look different enough to visually distinguish—– e.g., gold and silver are very reflective and are hard to tell apart under a microscope)</p><p>&nbsp;• Sandwich bags with zip closure</p><p>&nbsp;• Measuring spoons: 1 tbsp., 1 tsp., 1/2 tsp., 1/4 tsp.&nbsp;</p><p>• Deep pans or other containers for separating the glitter from substrate (one per group of students)&nbsp;</p><p>• Glass slides and cover slips (at least three for each group of students)</p><p>&nbsp;• Fine mesh sieves, kitchen strainers, and/or filter paper&nbsp;</p><p>• Warm water • Plastic knives or other flat instruments&nbsp;</p><p>• Black construction paper&nbsp;</p><p>• Graph paper&nbsp;</p><p>• Dissecting scope or video microscope.<br></p><p><b><u><i></i></u><i>1.2.1 PREPARATION&nbsp;</i><u><i></i></u></b></p><p>Before understanding how pollen and spores are used to reconstruct past climates, students need an appreciation of the diversity of these grains. Just like human fingerprints, each species of flowering plant has a specific pollen morphology that is unique. By examining the physical characteristics of pollen and spores, palynologists can identify the specific plant from which the pollen or spores arose. It is recommended to begin this activity by familiarizing students with the concept of how palynologists categorize pollen grains by size, shape, ornamentation, and aperture (i.e., characteristics of the pollen wall, such as furrows and pores). A diversity of pollen and spore morphologies is shown in Figure 3. To explore differences in pollen, have students observe real pollen by viewing the anthers of live flowers with dissecting scopes or handheld video microscopes. For example, Figures 4 and Figure 5 show the differences in shape, size, and ornamentation of lily and hibiscus pollens, respectively. To further extend student FIGURE 3 Diversity of pollen morphologies (color figure available online). FIGURE 4 Image of lily pollen taken with the 200× lens of the Scope-on-a-Rope (color figure available online). understanding of pollen and how it is transmitted, your class can collect airborne pollen. Smear glass slides with a thin layer of petroleum jelly and place them outside for a day or two. These slides can be examined using a microscope to look for any pollen grains that were collected. This simple experiment will teach students about “pollen rain” and show how pollen grains are transported by the wind from local flowers; this activity is most productive if done in the spring or early summer. Once students have a basic understanding of the morphological differences in pollen and spores, they are ready to conduct their own investigations on a simulated core. This simulated core consists of four layers that reflect the actual core that was recently acquired FIGURE 5 Image of hibiscus pollen taken with the 200× lens of the Scope-on-a-Rope (color figure available online). <br></p>