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Chuck Amsler, Ph.D.
Mission Co-Investigator

Intertidal collections

Journal By C Amsler

Posted On 2/22/2004 8:54:07 AM

A few hours before we arrived at Palmer on the Laurence M. Gould I gathered the team together in the ship’s lounge meeting area to discuss our priorities upon arrival. We talked about how we’d set up our labs and our section of the aquarium building and about what our top priorities for collections would be.

One of the top three field collecting priorities was making sure that we took advantage of the first good low tide to collect in the intertidal. All the species of marine plants and animals that our work focuses on live subtidally. That means that they live below the lowest of the low tide levels and are never exposed to air. But we do use one species of macroalgae (seaweed) that lives in the lower part of the intertidal. The intertidal is the part of the shore that is covered at high tide but exposed to air at low tide.

The tides at Palmer are very irregular. Many places in the world there is a predictable one or two high tides and one or two low tides every day. Not here. Sometimes there is one low and one high, sometimes two of each, and sometimes one of one and two of the other. Plus, some months very low tides are rare or occur only after dark.

The one intertidal species we use in our work is a small green alga called Cladophora repens. It lives in the lower part of the intertidal that is only exposed on the lowest low tides. We freeze dry it, grind it into a fine powder, and then use it to make artificial foods that we use in feeding bioassays. We’ll have more about those experiments in future posts.

We were fortunate that a series of very good (that is, very low) low tides was predicted for the afternoons this week. Thursday we did our equipment check out dives at the dock in the morning and planned to head out to collect Cladophora in the afternoon. Unfortunately, strong winds blew up right after lunch and so we had to cancel the afternoon trip.

Friday morning we awoke to much improved weather and we made our first collecting dives. The weather held so we headed out after lunch to take advantage of the low tide predicted for 2:30.

Our destination was Laggard Island. Laggard is one of the most distant islands from Palmer that we are allowed to travel to in the zodiac boats. Like many of the islands here it is long and narrow with the long axis running east and west. Laggard has two narrow inlets coming in opposite one another from the north and south sides that almost cut the island in two. There are lots of good spots to collect Cladophora there that are relatively protected from waves. That is why we go there to collect.

We arrived at Laggard about 2:00 and went to work. Maggie, Anne, Kevin, and I all wore our dry suits so that we didn’t have to worry about getting wet when a small wave did come through. Hla collected from the upper part of the alga’s range so that she didn’t have to worry about them at all.

The Cladophora was very abundant and it took less than an hour of collecting to fill up several large plastic bottles with the plants. The plants grow in cracks and crevices in the rocks so we use long forceps to pick them out. It is a slow and inefficient process, but there was so much material there that the small fraction of it that we could get this way was still plenty for our needs.

Before we knew it, we were ready to head back home to the station. Another successful day in the field complete!


TitleFromClick here to change to descending sortDate Posted
Re: Intertidal collectionsDarrius Robinson2/23/2004 10:11:19 AM

Dr. Amsler,
I enjoyed reading your journal about collecting green algae. You said you freeze dry it, grind it into powder, and then use it as food in experiments. What kind of animals will you feed it to?

From C Amsler, Posted On 2/23/2004 10:11:19 AM

Darrius -- We will add the powder to alginate, which is also an algal product. It is made from kelps and used in lots of human foods too. If you have ever heard that there is seaweed in ice cream, that is what they are talking about. We'll make something similar to a really really thick jello out of the mix and feed it to sea stars, amphipods (tiny shrimp-like animals), and fish. I'm sure that we'll have one or more journal entries about that process later on. Thanks for writing!. -- Chuck

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