Assignment Objectives

• Investigate how marine debris becomes trapped by ocean gyres.
• Predict where marine trash will accumulate in oceans.

What are the major ocean currents?

Step 1: Go to the ArcGIS Online map, Marine Debris, and explore the map.

Step 2: Zoom and pan the map to see all the ocean currents.

• Why are some currents red and some marked blue?

Step 3: Turn on the layer, Prevailing Winds. Change the basemap to Dark Gray Canvas. Wind patterns interact with water and land, globally.

Will an ocean current trap marine debris?

Step 4: With the Details pane visible, click the button, Show Contents of Map.

Step 5: Click the checkbox left of the layer, Pacific Markers. Click the Hawaii marker. Click the link to enlarge.

Gyres are sizeable circular ocean currents that redistribute heat and can trap marine debris.

Step 6: Zoom out and pan the map.

• Where are other gyres, potentially trapping debris?

Where does the trash come from?

Researchers estimate that 80 percent of trash comes from land, and 20 percent comes from marine sources. Read this article from the National Geographic Society to learn more about the plastic problem.

• What are the primary sources of land-based trash?

Step 7: Click the button, Bookmarks. Select Spokane.

Step 8: From the Details pane, click the button, Show Contents of Map.

Step 9: Click the checkbox to the left of the layer name, Spokane Downstream Trace.

• How can trash from inland areas, such as Spokane, reach the ocean?

Why are “garbage patches” filled with plastic?

Step 10: Pan the map to see the Pacific Ocean, and click the map marker near the Midway Atoll.

Step 11: In the pop-up window, click the animation of Trash Accumulation.

The trash from the United States coastline may take six years to reach the Eastern Pacific Garbage Patch, while Japanese trash takes about one year.

• One of the main reasons why trash is found in this area is because plastic floats. Biodegradable material decomposes, while plastic only breaks down into smaller pieces, but do not decompose. (T/F)

Step 12: Click the Spokane map marker to see one common source of plastic pollution?

What is the impact of marine debris?

Step 13: Turn on the layer, Blue Whale Concentration.

Step 14: Click the Blue Whale area on the map for more information.

• The impact to whales that ingest microplastics is that it causes malnutrition and intestinal blockage.
• How can you prevent additional marine debris?