Reeling in CTD Data

Understanding Physical and Chemical Parameters of Ocean Water Using CTD Profiles

Overview

A focus of the PolarTREC Southern Ocean Diatoms expedition was to collect water samples and physical profile data using oceanographic technology. Oceanographers rely on the real-time data transferred from the water column to the ship-based computers using a CTD sensor. The CTD measures conductivity (salinity), temperature and depth (based on pressure) along with additional information based on the oceanographer’s scientific questions. These data sets allow oceanographers to make decisions regarding sampling depths and the productivity of the water column. This lesson utilizes CTD profiles from the Southern Ocean Diatoms expedition, as well as open-source data from the California Current Ecosystem Long Term Ecological Research (LTER) database, the Georgia Coastal Ecosystems LTER database and the Hawaiian Ocean Time Series (HOTS) database to encourage analysis and comparison of ecosystems and physical parameters.

Objectives

Students will be able to:
- Interpret physical and chemical characteristics of ocean water using CTD profiles from various ecosystems.
- Report findings related to CTD data to peers.
- Compare CTD data from different ocean regions to select regions of productivity.
- Use appropriate strategies to work cooperatively

Lesson Preparation

Students will complete an engaging Jigsaw activity to analyze data from CTD profiles. Each group is assigned one CTD profile for analysis. Upon completion of the Student Data Sheet, students return to original groups to compare four different CTD profiles. Students finish the lesson by completing a claim, evidence and reasoning activity based on a provided research problem/question. This lesson can be used to engage students before covering topics ranging from variations in the ocean to primary productivity/photosynthesis.

Prior to the lesson, teachers may pre-teach the following vocabulary: water column, salinity, thermocline.

Teachers may also show videos of CTD casts (see resources for an example) to introduce the lesson.

Procedure

1. View CTD cast video and ask students to describe the process and predict the importance of this technology.
2. Divide students into ‘home’ groups of four or five students (depending on class size). NOTE: You can also place group numbers at the top of the handouts prior to class to eliminate forming groups twice.
3. Provide each student in the group with a different CTD profile (five are provided with this lesson, but others may be obtained).
4. Distribute one copy of the Student Data Sheet to each student.
5. Ask students to form ‘expert’ groups by finding other students that have the same CTD profile. These ‘expert’ groups should work together to complete Part A of the Student Data Sheet.
6. Students should return to their ‘home’ groups and share their analysis with group members.
7. Students in the ‘home’ groups complete Part B of the Student Data Sheet.
8. As a group or on an individual basis, students complete the claim, evidence, reasoning section.
9. CER rubric available for formative assessment.

Extension

• Contact oceanographers and find out how they utilize CTD data in their research (potential for classroom presentation)
• Analyze CTD profiles that include additional measurements (oxygen, fluorescence, etc.)

Resources

Southern Ocean Diatoms Expedition Journals related to CTD:
September 11, 2016: First Cast https://www.polartrec.com/expeditions/southern-ocean-diatoms/journals/2016-09-11
September 24, 2016: CTD https://www.polartrec.com/expeditions/southern-ocean-diatoms/journals/2016-09-24
CTD cast video courtesy PolarTREC

Additional CTD profiles: Hawaii Ocean Time Series (HOTS) http://hahana.soest.hawaii.edu/hot/methods/ctdtsod.html

Assessment

Pre-and post-questions
Jigsaw activity (self and peer assessment/collaboration)
Answers to Student Data Sheet questions
Claim/Evidence/Reasoning rubric

Author/Credits

Cara Pekarcik from North Quincy High School in Quincy, MA created this lesson as a follow-up to the 2016 PolarTREC Southern Ocean Diatoms expedition.
email: carapekarcik [at] quincypublicschools.com

Dr. Randelle Bundy is a Postdoctoral Scholar at Woods Hole Oceanographic Institution. Dr. Bundy created the CTD profiles using data from the 2016 PolarTREC expedition and other open-source databases.

CTD Profile Data:
Jenkins, Bethany; Chappell, Phoebe Dreux; Buck, Kristen (2016): September-October Southern Ocean Diatom Cruise. (CTD Antarctica 1, 2 and 3)

Di Iorio, Daniela (2004):  March 2003 CTD, PAR, oxygen and chlorophyll profiles for the Georgia Coastal Ecosystems Altamaha River transect. Georgia Coastal Ecosystems LTER Project; University of Georgia; Long Term Ecological Research Network. http://dx.doi.org/10.6073/pasta/d199091b14cd71b9f67ad0b93a975b4d (CTD Georgia Coast)

Goericke, Ralf (2016):  Conductivity Temperature Depth (CTD) Log of CTD casts from CCE LTER process cruises in the CCE region, 2006 – 2014 (ongoing).. California Current Ecosystem LTER; SIO; Long Term Ecological Research Network. http://dx.doi.org/10.6073/pasta/9b4fd22f289fcb599f285904929c3e37 (CTD California Coast)