Wednesday, July 11, 2012

Tsunami Debris and Pelagic Species

Written June 27, 2012, published July 2014

As massive amounts of floating debris begins to wash ashore from the tragic earthquake and tsunami in Japan, March, 2011, the possibility that species local to Japanese waters could be transported to our coast in debris went abruptly from speculation to reality when a floating dock and boats arrived on beaches from BC to Oregon. With it is an opportunity to track estuarine and pelagic drift species, to determine biologically how long a floating object has been in the water.

Growing on the dock were dozens of species native to Japan, including a few that might be considered invasive. Species found and removed from the dock’s surfaces included: brown, green and red seaweeds; gooseneck and encrusting barnacles; snails; crabs; clams; several worms; bryozoans; and starfish.  Likewise the small boat that washed up on our beach was well colonized with a number species. These were in Japanese waters before the earthquake. 

A brown plastic beverage bottle and a small float both were colonized by pelagic gooseneck barnacles, Lepis anatifer, a widespread oceanic barnacle. Photo by Kathleen Sayce

Land-based floating debris carries a different set of organisms; these are typically from oceanic waters. Open water species are called pelagic, from the Greek word for open sea. A very common animal on marine debris that arrives on our beach is Lepis anatifera, the Pelagic Gooseneck Barnacle. These barnacles are often seen in the company of bryozoans and filamentous diatoms on floating objects; these species are widespread, and are found on drifting objects all over the world. 

Gooseneck barnacles are so named because they have long pedicles, or necks, which attach to subtidal rocks, and to driftwood, floats, water bottles, docks, boat hulls and soccer balls. All barnacles are hermaphrodites with internal fertilization. Eggs are held inside the shell of the adult barnacle until the larvae hatch. As drift moves across the ocean, barnacle larvae swim with it, and like many marine invertebrates, the young animals settle near or on adults of the same species. Thus multiple generations of pelagic gooseneck barnacles live on drift that has been in the water for a year or more, and only one generation of barnacles lives on drift that recently entered marine waters. 

On a recent cleanup ride with Russ Lewis, a beachcomber and volunteer with Grassroots Garbage Gang, we picked up plastic debris from Oysterville Road into Leadbetter State Park. In three hours we gathered bags of debris from the 2011 tsunami:  Numerous foam pieces, white, orange-yellow and light blue to light green, some with black roofing on it; several water bottles with Japanese logos; and fishing floats, small to large. 

This closeup of a clump of gooseneck barnacles shows that several generations of barnacles have lived on this float, indicating that it has been in the water for many months. Photo by Kathleen Sayce

One fishing float had oysters more than two inches long, encrusting barnacles, filamentous diatoms and gooseneck barnacles; this float was probably in the water before the tsunami.  The largest gooseneck barnacles we found were more than four inches long, with shells one and a half inches long. Attached to these adults were tiny gooseneck barnacles less than one half inch long. 

We did not see the numerous coastal species associated with the floating dock. Most of the debris we found was probably colonized by pelagic species after it was dragged offshore.  

Normally the biggest beach cleanup of the year is the 5th of July cleanup, when more than fifteen tons of fireworks and party debris is removed. This year and for several years to come, no one knows how much extra debris will be removed from local beaches due to the 2011 tsunami. We treasure our local beaches. If you do too, join the cleanup team on the 5th, or better yet, pick out your own mile, half mile, or quarter mile section and keep it clean year round, as dozens of Grassroots Garbage Gang volunteers already do.