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.

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.

Intrusion intrusion

There is a fishy intruder in my seawater table. I don't know how it got there, but it certainly wasn't there when I set up the experiment yesterday. It most likely got sucked up the pipes for the seawater system, but it looks kind of big for that...

o hai.

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:

Cages and friends

Over the past few days, we have been working hard to get everything ready for our big trip up to Isla Baltra, where we'll be working on multiple big experiments. I am going to be setting up my Pentaceraster cages this week, so I've been pulling together all the necessary materials and tools, and compacting them for transport.

Rolled-up cage sides and a stack of cage tops in the corner.

Someone has been busy in the week since I last worked on the caging material.

Rebar as cage anchors. I bought 6m of it at the construction store for $3.50 and asked them to cut it into 30cm pieces. They must have been very confused - I don't think they have ever cut rebar this small.

At the same time, we'll be setting up concrete bases for a large-scale sea urchin predation experiment that the lab will be running for the next couple of years. The bases will be put in the water this trip to accumulate a mat of turf algae for the urchins to graze on when the experiment actually gets going next summer. We moved them from the hardware/construction store to the loading dock yesterday. I'm excited to start putting them down using lift bags.

Jon on the station dock with his concrete bases.

The marine iguanas really liked them too.

We leave for Baltra tomorrow morning, so we loaded all our equipment into the boat today - there is a lot of it. We piled up all our stuff into a water taxi and it took two trips to get all of it on board our boat, the Pirata (probably the most adorable boat I have ever seen, complete with little pirate flag).

A very full water taxi at the loading dock. You can see: about half my cages, concrete bases, green oxygen box, GoPro camera stands, plenty of rope, quadrat, containers for Hexaplex snails. All our dive gear is in there as well, under the cages and rope.

Loading the concrete bases onto the boat. We were getting stared at by everyone in the passing boats and water taxis.

Will be hard at work for the next few days. There will eventually be photos.

More fun and cagery

When we did our first few dives at Baltra, I set up a single cage for my Pentaceraster starfish as a test to see if (1) the cage would hold up against the current/surge; and (2) if the cage would keep my Pentaceraster enclosed. We visited the site again on the final day of the research cruise, and I was very glad to see that the answer was yes on both counts (with n=1, but I'm okay with that...)

One week later: Inti from the Darwin Station examines my still-caged Pentaceraster.

Now that I know this kind of cage can work as an enclosure/exclosure, I'm going ahead and scaling up cage production in preparation for deployment next week. The test cage had a diameter of 0.5 m, which is a little small for a Pentceraster that can have an arm radius of ~20 cm. The new cages are 1 m in diameter, and I am constructing them from old caging material previously used to enclose sea urchins (yay for recycling old and fouled research gear). I have been working with wire cutters and cage wire and lots and lots of cable ties over the past 3 days.

Fun with cages. About 10 minutes after this picture was taken I switched to actually wearing work gloves.

I also made a few friends, and learnt that baby marine iguanas are small enough to fit through the holes of my cages.

This little guy came by and visited me several times.

Any kind of tedious and/or repetitive job needs a work song, so here is my cage building song:

I've Been Making Starfish Cages
(to the tune of "I've Been Working On the Railroad")
I've been making starfish cages
For hours every day
I've been making starfish cages
And the time just slips away
Hope my predator inclusions
Show me interaction strengths
Hope my starfish cages weather
The storms and surge and waves!

Kludgey science

Over the past couple of days we have been scavenging bits from Jon's piles of old research equipment at the Charles Darwin research station for use in our experiments this summer. If you've worked somewhere for 10 years I guess you accumulate lots of stuff, particularly if you're a macro-ecologist and like doing large scale things. Leslie's project aims to create a demographic model for an ecologically important predatory snail species, Hexaplex, and compare how its populations behave in areas where it is fished, versus areas where fishing is prohibited. To figure out the different parameters of the model (e.g. growth rates, mortality rates for different sizes of snail), she needs to tag a bunch of Hexaplex in their natural habitat and track them over time. So we dug into Jon's stash of barnacle recruitment plates from 2003 (complete with 8 year old barnacle tests) to find tags she can use.

Some scraping with screwdrivers and a few good rinses gave us slightly over 200 tags, all ready to be Z-sparred* onto Hexaplex shells.

Leslie is using plastic calipers for her measurements of Hexaplex, but the starfish I will be studying are a little too big for that. The bigger ones, Pentaceraster and Mithroidia, can have arms up to 17cm long. So I made my own measuring instruments out of an old transect tape, cable ties and old fishing weights. I have no idea what the weights were used for before (we pulled them out of an old box and they were all cable-tied together in fives) and I'm pretty sure that transect tape was hopelessly tangled long before I even knew what an echinoderm** was, but the cable ties were the only new component of my brand new starfish measuring tapes.

And while I had the fishing weights and cable ties on hand, I made a little upgrade to the underwater housing for my camera. The housing is positively buoyant (=it is floaty) when I dive, which is really annoying because it floats up and smacks me in the face when I'm not holding on to it. Canon makes a weight system for the housing, but it costs a whopping $26 for what is essentially a screw and a few pieces of metal. So I cable-tied a fishing weight to the bottom of the housing instead. We'll see how well that works tomorrow, when we do our first Galapagos dive (!!!)


* Z-spar is the name of an underwater epoxy. I think it is probably counted among the holy trinity of field marine ecology: PVC, cable ties and Z-spar.
** Echinoderm means "spiny-skinned" and refers to the group of animals that includes starfish (my study organisms), sea urchins and sea cucumbers.

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

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.