Exercise Overview - Part 1

Page 1

What are deep sea sediments? What do they contain? How are they dated? How are they sampled? How are they used to understand climate change?

In this exercise, students will understand how deep sea sediments are collected and analyzed to identify various foraminifera species which are used to interpret global paleo temperature/climate change.  This is accomplished using pasta which is substituted for foraminifera which are collected and analyzed in order to develop a paleotemperature/climate change record.  Throughout the activity video clips have been inserted that will help students connect their work with the research of scientists at the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts.

Deep sea sediments are collected in every part of the ocean and analyzed for a number of different parameters, including foraminifera (or forams for short), in order to determine changes in ocean water temperature. Foraminifera are single-celled Zooplankton (protists with shells). The shells are called tests. Adult forams range in size from ~100 microns (0.1 mm or 0.01 cm) to ~2.0 centimeters in length though average the size of sand grains. The largest living species, which grow to ~19 cm have a symbiotic relationship with algae which they "farm" inside their tests. Other species eat foods ranging from dissolved organic molecules, bacteria, diatoms and other single celled phytoplankton, to small animals such as copepods. They move and catch their food with a network of thin extensions of the cytoplasm called reticulopodia, Similar to the pseudopodia of an amoeba, although much more numerous and thinner. Forams live in every ocean and after they die they sink and are deposited on the bottom of the ocean.  As a result, forams are almost always incorporated into the "mud" collected in deep sea sediment cores.  Different individual species of forams have been used to indicate a number of oceanographic indices but more importantly they indicate ocean temperature.  Of the most important are Neogloboquadrina pachyderma (N. pachyderma, Figure 4 and 5) and Elphidium excavatum (E. excavatum, Figure 6).  N. pachyderma are unique in that their tests coil to the left or right depending on ocean temperature with left-handed coiling tests favoring colder water and right-handed coiling tests favoring warmer water. The E. excavatum also favor colder water and grow larger as water temperature decreases. Also important is the foraminifera Globogerinoides rubber which occurs in two varieties.One produces white shells and occurs in all oceans while the other variety produces pink shells and is restricted to the Atlantic. Another single-celled marine organism collected in deep sea sediments are Radiolarians which form very beautiful, unique, and intricately detailed silica-based exoskeletons. They occur throughout all the oceans though are generally most abundant in low-latitude areas with their abundance dependent on the quality of the water, including water temperature.