Return of the petri dishes

So far this semester has been: 2.5 days Brown - 4 days Nahant - 3 days Brown - 4 days Nahant. Last Friday-Monday I was back up there running a full isopod herbivory experiment. Basically, the trial we ran the week before showed that isopods might actually graze enough to be important, so we should look at their grazing patterns in greater detail.

 Multiple-choice petri dish setup: we have 6 species in there. You can just see an isopod in front of the rubber band on the far chamber.

 

70 petri dishes, 210 isopods, 63 grams of freshly collected algae.

Here we go again...

More fun with herbivory

School started on Wednesday, which means that I had to leave Nahant and go back to Providence and actually sit in classes. My classes this Fall are fairly interesting - Conservation Biology, Methods of Applied Math, an Introduction to GIS - plus I'm auditing an experimental design class. Still, interesting classes are less exciting than actual research, especially actual research that still needs to be done. I have a very nice 3-day class schedule (Tues-Thurs) so Friday found me right back at the Marine Science Center working, again.

This summer I ran a big herbivory experiment looking at Lacuna snail preferences among different species of subtidal algae. This weekend I'm trying to figure out if other herbivores like isopods may also be important in grazing the algae.

The baltic isopod, Idotea balthica. This is a fairly large individual; the ones we find in our algae are generally around 1 cm in length.

To do this we're running a much smaller-scale pilot experiment with just a couple of algal species and only 6 replicates each. The isopods go in little modified petri dishes with a similar structural theme to the containers I used for the Lacuna experiment - identical amounts of algae in both chambers of the dish, herbivores in one chamber.

One of my petri dishes. The right chamber has herbivores; you can just see an isopod at the top-right of the tag number 08. The left chamber is herbivore-free to account for loss/gain of mass that is not due to herbivory.

The overall setup. Petri dishes are zip-tied down to the aqua mesh to keep them submerged. You can see that they are arranged nonrandomly because my arms are short and I can't reach the area in the middle right of the water table. They are interspersed, though...

Scuba Smurf did a dive to check that everything was well attached and working.

Scuba Smurf approves of this experimental setup.

Introducing...Scuba Smurf!

Today I got a new dive buddy: Scuba Smurf.

Scuba Smurf was a gift from my five-year-old friend Caden. He is all decked out in his flashy dive gear, complete with octopus, power inflator and dive gauge/computer. Scuba Smurf is going to have great adventures, but first he needs a check-out dive in the lab touch tank...

Scuba Smurf meets our resident blue lobster (newly moulted!!)

You can follow the adventures of Scuba Smurf here, on his photo album.

The things you find in algae, part 2

Sometimes when it is 11pm and I am still in the lab and I have been sorting algae for 8 hours, I need something to remind me why I love marine science. Sometimes that thing is an itty bitty brittle star.

:)

It is 5 millimetres long. To this brittle star, the one little piece of algae I am holding in my hand is a forest.

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.

Summer in Nahant: a first alphabet

This came out of a random conversation with Kylla - the kind of conversation you have when you are both still! in the lab on a Sunday evening - about intertidal Latin name ABCs. I have modified the idea somewhat.

Things that make my life easier

One of the projects I'm working on in this last month of summer is a repeat of an intertidal experiment we ran last year, with an additional control treatment. In our lab's various studies of rocky intertidal communities, a general method is to conduct regular surveys of the number and abundances of algae and invertebrates like snails.

Two of the most abundant intertidal herbivorous snails. The little snail is Littorina obtusata, the smooth periwinkle (and my favourite intertidal snail!) and the larger snail is Littorina littorea, the common periwinkle.

Survey method: 1. Place PVC quadrat on spot; 2. Record all algae and invertebrates found in quadrat

For field experiments, we set up permanent plot using bolts and washers so we can survey the same plot and track changes over time. However, the markers can be frustratingly hard to find again under all the algae, even if you know where the plot is.

One of my plot markers from last summer. When the tide comes in and out it vanishes under a canopy of algae.

So, the thing that has made my life better: pretty, eye-catching fluorescent zip-ties on the plot market bolts! They significantly reduce search time and make it possible to find and survey 40 plots in a low tide.

Bright yellow zip-tie tag on one corner of a permanent quadrat, labelled washer on the other.

They are so visible among the algae!! You can see more in the background...

Fun with herbivory

This blog has been awfully quiet as of late, mostly because I've been insanely busy. I've been back in Nahant for about two weeks now and am working hard to get all the planned research for my algae project done before class starts on the 7th of September and I need to be back in Providence. I've also been helping out with other projects in the lab. But I just got a big experiment up and running, so things will be a little less hectic for a couple of days - mostly simple maintenance and checking up on it.

When I last wrote about the algae project I talked about the big question of "what is it doing here?" We're trying to figure out how the invader is impacting the ecological community. In any introductory ecology class you learn that two of the main interactions between species are consumption (e.g. herbivory, predation) and competition (for space, light, food). My experiment is looking at the first interaction and asking, do the native herbivores in the community eat the invader? How much of it do they eat in comparison to other native algal species? Could this impact growth and survival of the invader relative to other species?

In this case, the herbivore is a tiny little snail, Lacuna vincta, that can occur in relatively high densities on the algae. It is found mostly at shallow subtidal depths, though I have seen it on algae in the low intertidal zone.

Here it is on a ruler. awww.

To see if it has significant preferences for the invader or for the native algae, I put a bunch of Lacuna in a little snail mesocosm (=a food container with holes drilled and mesh glue gunned on) and offer it a choice of the invader, plus five other common algal species. At the same time, I have other snails in other mesocosms that have only one species of alga, so I can compare how much of each species they eat when they have 6 choices vs. no choice over about 3 days.

Multiple-choice mesocosm. There are 6 species in each chamber, and the one on the left has 30 Lacuna snails. The one on the right is a control for any loss/gain of algal mass not due to herbivory.

I have 10 replicates of everything, so 10 x 6 species for single-choice + 10 multiple choice = 70 mesocosms. This means 240 pieces of algae which had to be collected and individually portioned/weighed and 2100 snails which had to be collected and counted. You can see why I've been busy.

Hours and hours of collecting and sorting snails...

Final experimental setup on two seawater tables at the MSC:

5 AM field days...

...bring great intertidal sunrises :)

5:25 AM at 40 Steps Beach

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

Return to Cunner Ledge!

I've been working hard on collecting and sorting algae from morning to night for the past few days, but this morning I found some free time to walk around Nahant's East Point, which is always nice. It was just after low tide, so I went out to my old field site next to Cunner Ledge. Here it is, marked with the yellow arrow in the picture and on the Google map for East Point. You can also see the Marine Science Center on the map.


I am a little less sure-footed than I was last summer (especially since I was climbing the rocks in flip-flops this morning) but I went back down and looked for my 0.5 m x 0.5 m plots. We set up 30 plots along that seaweed-covered ledge last July. My plot markers are still around :)

This was the very first field experiment that was truly my own - Matt helped me set up the plots at the start, but I collected the data and maintained the plots for the 8 weeks that it ran. It was a small-scale manipulation of the diversity of basal species, i.e. species that bring energy into the system. Seaweeds do this through photosynthesis and filter feeders like barnacles and mussels do this by consuming plankton from the ocean.

And while we're on the topic of my field site, I finally got round to digging up the screencap of Cunner Ledge in the movie Shutter Island. The movie was partly filmed in Nahant, and my field site makes a half-submerged appearance. So here we have Leonardo DiCaprio pointing a gun at a guard, which is all very interesting, but LOOK THERE IS MY SITE IN THE BACKGROUND. Which is really the best part of the entire movie.

The great escape

Living and working in a marine lab is always interesting because things like this happen.

I am sitting in the lobby of the building at night, working on my laptop. Out of the corner of my eye, I catch movement in the dark, empty main lab. An escaped green crab scuttles out into the lobby in a small burst of speed, then pauses to see if anyone has noticed.