Getting Started at Palmer

Photos from UAB in Antarctica group on Flickr, related to this post
By Philip
Posted on 04/07/07

It did not take long to get into work mode upon arrival at Palmer Station.  After only a week I have already made four Antarctic dives where I collected enough material to get my project started.  I have initiated two separate experiments, and I have snapped over 300 pictures.  When you only have 2 months at a research station, time is of the essence.

Allow me to provide a bit of background on my research topics.  As you have been reading in the other team members' journal entries, we are interested in relationships between amphipods and the macroalgae which dominate these communities. Research by former team member Yusheng Huang showed that amphipod grazers often feed upon a shallow water red macroalga called Palmaria decipiens.  Along with being palatable, the Palmaria is host to an small endophytic and epiphytic (living inside and attached to) brown filamentous alga called Elachista antarctica.  This brown algal species is not found growing anywhere else on Earth. 

So why would this brown alga decide to live only on a red alga that grazers love to eat?  To get to the bottom of this I am starting at the beginning of the Elachista's life history, their spores. 

Like many other algae, Elachista reproduces via an alternation of generations.  In this case it is between very tiny plants that produce male and female gametes and an alternate generation of almost as tiny plants which results from the union of those gametes.  These plants in turn release spores, which settle and begin growing back into plants that produces gametes.

Spores of Elachista are released by the hundreds from structures called unilocular sporangia.  It is these spores that (I hope) hold the key to understanding Elachista's settlement on Palmaria. 

There could be a few things going on in this red algae-brown algae relationship.  Perhaps the spores of Elachista antarctica settle on the red alga because Palmaria decipiens possess a chemical property that aids in Elachista’s growth and reproduction. Palmaria might produce organic compounds that attract Elachista  spores  or stimulate them to settle. 

On the other hand, maybe Elachista are deterred from settling on the other macroalgae in the area due to chemical defenses of all macroalgae except Palmaria.  So although this brown alga would colonize other macroalgae if they could, they are shunned away by chemical defenses and left with only one option, to settle on Palmaria. 

Another possibility is that the Palmaria  produces attractants for Elachista spores because they benefit in some way from having the brown alga growing on them.  Perhaps, for example, the Elachista produces chemical defenses that deter larger herbivores. And still, although unlikely, Elachista might settle on other macroalgae besides Palmaria and we simply have not seen it on another host.  I am going to pursue answers to all of these possibilities during my time at Palmer Station.

In order to investigate Elachista antarctica's host choices I need Elachista spores.  For the last year at UAB I have tried numerous manipulations of photoperiods, media transfers, and temperature shocks to induce spore release from the little guys that I grow in a culture incubation chamber. 

While diving here at Palmer, I collected Palmaria decipiens with Elachista antarctica growing on them and used several tactics that others have used with other macroalgae to induce spore release in the lab.  The osmotic shocking combined with temperature shocking seemed to work best. 

After I dissected the Elachista. antarctica off its Palmaria decipiens host, I placed a clump of filaments complete with unilocular sporangia on a slightly damp tissue like material called a kimwipe for an hour to slightly dry out Elachista.  I then dunked the filaments into a dish of filtered seawater that was incubated at the highest possible temperature that this alga would be accustomed to in nature, 3°C. 

As the Elachista released spores I set a piece of Palmaria into the dish after removing the filaments from which the spores originated, in hopes that spores behave in the lab as they would in the field and preferentially settle on the Palmaria.  This is where I am currently at in my research.  Stay tuned sports fans.

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