The things you find in algae

My big herbivory experiment is done, and the summer is coming to a close - classes start in less than two weeks! There's still plenty that needs to get done - yesterday we did a trip down to Connecticut and Rhode Island to collect some algae. Similar to what I was doing at the start of the summer, we are trying to quantify the species composition of algal communities in different locations, where the invader is present.

So I am back to sorting algae out of bags, which is long and somewhat mind-numbing, but there are many happy distractions in the form of little critters hiding out in the algae.

Today is arthropod day...

A little spider crab sitting on the tip of my finger.

Itty bitty little crab - it looks like an Asian Shore Crab, which is also invasive to this region. For scale: it is sitting on a microscope slide.

A very pretty pycnogonid (sea spider) on the same microscope slide.

Terrestrial invasion

Last week we put aside our stinky wetsuits and scuba gear to explore terrestrial Galapagos for a few days. We went out into the highlands of Santa Cruz with Heinke, a postdoc at Brown, and her two Ecuadorian field assistants. Heinke studies the impacts of an tree species (Cinchona pubescens, the quinine tree) that was introduced to Galapagos from mainland Ecuador, and has been doing research here for many years.

Introduced/invasive species are a particularly big concern in island ecosystems like the Galapagos. In the Galapagos National Park, there have been huge efforts to control the spread of invasive species and protect native Galapagos species. The results of these control efforts can be clearly seen where the national park borders private/agricultural land.

National park land on the left, agricultural land on the right. The plot on the left is full of the native Galapagos miconia plant, while you can see plenty of non-native elephant grass on the right.

Miconia robinsoniana, an endemic shrub that grows at high elevations. The 'miconia zone' at ~600m is named for it.

We had a beautiful, mostly clear day at Media Luna, which is unusual - the highlands have been rainy even when the coastal areas are clear and sunny. But when they are not shrouded in clouds, the view from the highlands is incredible - 180º of ocean - and you can see all the way to Puerto Ayora!

A clear view all the way to the ocean, with Puerto Ayora and Tortuga Bay in the south.

The Cinchona trees are very conspicuous against the native shrubs of the highland 'miconia zone' - they tower over everything else. Equally conspicuous is the park management's aggressive attempts to control it - around the Media Luna crater itself, they have cut most of the Cinchonas and locally applied chemical herbicides, leaving behind bare trunks.

Cinchona trunks as far as the eye can see.

One of the big questions that people tend to ask when looking at an invasive species is: what effects does it have on the ecological community? It is a question I have been asking as well, with respect to my own algal invader. Because Cinchona is a tree in a community that previously had no trees, it has the potential to shade out other plants and limit the light available to them for photosynthesis. Heinke's experimental set-up aims to figure out exactly what the effects of Cinchona shading are, using artificial shades to control the amount of light available to the native shrubs. It will be cool to see how this affects the species diversity and composition of the plant community.

Two different shade treatments: total shade in the centre and partial shade on the left. On the right you can see a Cinchona forest that hasn't been managed by the national park - a really different-looking plant community compared to the short, shrubby one in the foreground.

For the past year, I've thought of invasive species mostly in terms of the marine algal species I study. It was interesting to look at it in a terrestrial system, particularly an island one. It gives me a slightly broader perspective on things before I return to the invasion happening in the shallow subtidal zone of New England.

The W's of a species invasion

When people go beyond the typical "oh you are studying marine biology that really cool" talk (something that I should write about at some point) and want to know exactly what I am doing with my summers, I usually say that I am studying a species of seaweed that is not where it's supposed to be. Most people have never heard of the concept of introduced or invasive species before, so the conversation usually turns in that direction and only occasionally goes back to my research.

But these conversations makes me wonder how I can talk about what I do in a bit more depth, while keeping it interesting enough for people who think algae is sushi and muck on fish tanks. I am going back to a primary school English composition framework because I realised that studying a new species invasion is a bit like the compositions we were taught to write as seven year olds - you have to address the same spread of questions. Also, if you can explain your science to a seven year old then you either have a brilliant seven year old or you have achieved relatively good communication of your science. (Which is why you probably have to test it out on more than one seven year old.)

So here is a brief summary of the questions we are asking, in terms of the good old 5 W's:

1. Who

Who is the invasive? - This question is a little bit out of order, since we had to figure out what the algal species was in order to determine that it was a new invasive species. This question was answered last summer, thanks to Craig Schneider at Trinity College who first documented the presence of Heterosiphonia japonica in southern New England.

Mr. Hetsiph makes friends with a kelp stipe.

2. Where

Where is it now? - We have some idea of this from last summer and a tentative northern range limit, and there are people further south who are looking out for its spread.

Where did it come from? - Most likely from European waters, where it is also invasive, but possibly from its native region in the North Pacific. This could probably be figured out using genetic comparisons of the New England populations with potential source populations from different places, but that is out of this lab's area of expertise so it is probably a question for someone else to answer.

3. When

When did it get here? - Still unknown, but certainly sometime before summer 2009, when it was first found and identified in New England. We don't know if it was introduced only once and just spread rapidly, or if it was introduced multiple times in multiple locations.

4. What

What is it doing here? - This is where we're at now. What kind of interactions does our invasive species have with the native community of algae (competition for space and nutrients, maybe?) and the herbivores like snails and amphipods? To try and answer some of these questions, we are conducting field surveys of algal species and abundances, which will lead into field and lab experiments later on.

"What does this mean for me?"

5. Why

Why does this matter? - Probably the most important question of all. Why should anyone care? Well, invasive algae have been an issue in the western Atlantic for some time and some have significant negative impacts (e.g. Codium fragile). Coastal management agencies are interested in knowing the potential impacts of the invasion on coastal health, water quality, etc. And because of the relatively early stage of this species invasion, what we learn about Heterosiphonia could contribute to a more general understanding of what makes an invasive species successful, and how invasions spread.

That's it for now, tomorrow I shift gears completely and head for somewhere a little more exotic. I fly from Boston to Quito, Ecuador, and then take a domestic flight into Baltra in the central Galapagos archipelago on Thursday. Hopefully there will be more blogging from the land of the tortoises.

So what exactly am I doing with all this algae?

This is what I have been doing for the past week.

We've gone diving at sites in Nahant and in Rye, NH and put down 0.5m x 0.5m PVC quadrats like the one below. First, we visually identify each species of algae and record the approximate percentage of the quadrat that it takes up. Then we collect all the algae in the in the quadrat, put it in a bag and take it back to the lab. We collect about 10 bags per site.

This is a quadrat (pre-collection) from Nahant last year. I haven't yet taken my camera underwater this summer.

In the lab, we sort the algae by species and clean it - i.e. remove little critters like amphipods, isopods, little crabs, little starfish*. The result is something like in the picture - neat piles of algae on a lab tray. Then we weigh the algae by species in two ways: 'fresh weight' which is just spinning it down in a salad spinner to remove excess water and then putting it on a scale; and 'dry weight' which is putting it in an oven at about 65ºC so that it is completely dried out, and then weighing it (this destroys the algae so you can't do anything with it after).

This is all the algae from one (0.5 m x 0.5 m) quadrat from our Rye, NH collection site. I am pretty sure that if I cleaned up the algae up a bit better and arranged everything a bit more prettily, I could convince someone that it is some kind of Japanese delicacy that they should try.

This whole long process gives us estimates of two things:
1. How many species of algae are out there, and what they are
2. How much of each species is out there, in absolute terms and relative to the others. This can be measured by percentage cover of the quadrat or by weight. We are doing both to see how well the two agree (i.e. if one is an accurate proxy for the other).

These two things can then be used to tell us plenty of other things such as how diverse the algal community is, and which species we should use in lab experiments.


*This is described in one sentence, but is the longest, most tedious part of the whole process. It took us <1 hour of underwater time to collect 10 bags of algae, and a full day to clean, sort and weigh only 7 of those bags. During the process I wrote this song.

The Algae Song
(to the tune of "Daisy Bell")
Algae, Algae, give me your answers true
I've gone crazy, just from sorting you
The amphipods are too many
And Desmarestia is nasty
But soon I'll find
If Hetsiph might
Influence diversity