RI intertidalling

This weekend was the first weekend of the semester that I wasn't in Nahant, which was a bit of a relief. I really love being in Nahant and doing research there, but constantly traveling and doing homework on the train/in the lab is a little tiring. Nevertheless, I still got to go out into the field over part of the weekend to help set up an algal transplant experiment in Little Compton, RI.

Field site in Little Compton. I love how you can see the diversity of reds, greens and browns from a distance here.

Intertidal cormorants!

 Kylla's been setting up reciprocal transplants of Fucus vesiculosus (which Wikipedia says is the 'bladder wrack' - I don't know the common names for any algae!) from the low and high limits of its intertidal range, at sites spanning ~500 m of New England coastline to figure out if low and high zone Fucus show different survival rates and nutrient uptake, and if the patterns vary geographically. This weekend we set up the transplant for one 'south of the Cape' site in RI.

This means abducting the algae and re-attaching them either to the same tide height or the other end of their range over the course of 2 days' fieldwork. We have (bright! coloured!) cable ties around the algae to act as anchors into the z-spar on the rock. There are also temperature loggers deployed at the low and high tide height to monitor temperatures experienced by the transplanted Fucus.

 

Scuba Smurf helped out too. Here he is with the numbered setup and Fucus transplanted to the high zone!

Scuba Smurf with the little PVC hut that holds the temperature logger. 

Yay for interspecific variation!!

Old field romping

We're into the second week of Fall classes so things should be settling down somewhat. Yay for classes that have a field trip the second week. And yay for classes that make small sotongs and their marine friends do terrestrial fieldwork.

Yesterday we drove about 45 minutes from Providence and sampled old field communities in Glocester, RI for an experimental design class. I'm always slightly surprised by how big the quadrats for terrestrial work are...I'm not sure if this is a general pattern. We quantified white pine abundances at different distances from the forest edge, and milkweed abundances on 10 x 10 m grids.

Old field with goldenrod and milkweed, and the forest edge in the background.

Counting milkweed in a square metre quadrat on a 10 x 10 grid.

Also, everything was remarkably clean, i.e. there was nothing wet or slimy or particularly smelly. I guess everything is weather-dependent (we got a tiny bit of rain) but still, nothing comparable to algae-covered butt.

Scuba Smurf came along too. Somewhat out of his element, but he quickly made friends with the milkweed.

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.

Off site algae collection

Today we drove slightly over an hour north to Rye, NH to revisit a site from last summer and do some algae collections there. This is a picture of our entry point into the water, and the actual site of collection is just next to/behind the big rock on the left.

The picture is deceptively warm and sunny and hides the fact that the water temperature was still 7ºC/45ºF, which is about where it is in the early winter. So we were freezing in our wetsuits for both dives and I am still cold 7 hours after exiting the water.


But on the way back we got crabcakes at a roadside place and sat in the sun and it seemed like New England summer again.