Blog, Boulder Patch, Methods, Science

Gauging the happiness of your kelp

If one is prone to anthropomorphizing, one is often wont to whimsically wonder: How happy is my kelp?

In science land, we can gauge how ‘happy’ a plant is by how productive it is.
There are a few different ways to do this, but one of the main ones is to measure a plant’s biomass. Plants and algae produce biomass through photosynthesis: turning sunlight and carbon dioxide into the sugars that make up their body (phycologists call an algae’s ‘body’ the thallus). You could say that a kelp that produced a lot of biomass in the past year is very ‘happy’ aka got to do a lot of photosynthesis.

Let’s illustrate this by looking at some kelp (Laminaria solidungula, as usual):

This kelp was collected in the Boulder Patch last year (2014). It grew over 30 cm in the 2013-2014 growing season!W1 CB14039

These kelp were collected at the same site a few days ago (2015). They grew less than 5 cm in the 2014-2015 growing season.W1 CB15032 to 34

What’s happening here? Why was the kelp so ‘sad’ this year when it was so ‘happy’ last year?

The major reason is light levels during the summer: more light = more photosynthesis = happy kelp; less light = less photosynthesis = sad kelp.

Very Professional And Scientific depiction of how how light environment affects kelp.
Very Professional And Scientific depiction of how how light environment affects arctic kelp.

Storm activity has a really large effect on light levels in the Boulder Patch, stirring up sediments and blocking the sunlight from reaching kelps. Dirty ice (exactly what it sounds like) can also negatively impact the light conditions.

You can see the effect of storms in the Dunton lab’s long term dataset of kelp growth in the Boulder Patch if you look at 2003 compared to other years. Kelp growth across the Boulder Patch fluctuates year to year, but it’s really low in 2003. That’s because there were a lot of summer storms that year.

(Also see Dunton, K. H., Schonberg, S. V., & Funk, D. W. (2009). Interannual and spatial variability in light attenuation: evidence from three decades of growth in the arctic kelp, Laminaria solidungula. In: Smithsonian at the Poles/Contributions to International Polar Year Science (pp. 271–284)).

Average Laminaria solidungula linear growth per year. Error bars are standard error.
Average Laminaria solidungula linear growth per year. Error bars are standard error.

I hinted in a past blog post that last summer was particularly stormy. Preliminary data from our light sensors in the Boulder Patch show that the light environment over the past year was rather poor. What’s cool is that we can see that in this year’s kelp measurements and, by comparing them to the long term data, we can estimate the relative condition of the light environment.

This makes Laminaria solidungula a particularly good bioindicator for this ecosystem because some simple biological measurements can tell us about the physical environment. A less dramatic (and less fluffy) canary in the coal mine, if you will.

*** you can read more about Laminaria solidungula and how is grows here

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