Sea lion vs. camera

Digging into the backlog of things I've meant to post, here is an excerpt of one of the videos from the fish diversity recordings featuring a curious sea lion trying to eat the camera...




As it swims off it goes right for the transect tape, which is why you see the tape move up into the camera frame. We've seen this kind of demonic intrusion before...

Sharing space

Working on a sheer subtidal wall can be interesting, especially when the wall has exactly two (2) ledges that you can put cameras and research equipment on, and exactly one (1) of them is occupied by a sleepy sea turtle that doesn't want to move.

I have seen and swum with many turtles before, but this is the first time I have ever looked one straight in the (sleepy blue) eye. It is a little bit surreal to be stared at by a turtle.

I see you too.

We wrapped up our last Galapagos dive yesterday, making a total of 48 for this trip. The next week and a half will be some data analysis and a side trip to the western island of Isabela for Leslie and me, then it's back to Nahant and more algae work. The summer goes by quickly.

The camera sees all: Manta ray at Baltra

Over a week after one of our early dives at Isla Baltra, I review the video from the GoPro recordings and see this. None of us knew it, but we were diving with a manta ray. I guess we should look up from working on the bottom once in a while... :)

Does fish diversity matter?

Previous work out of the Witman lab has looked at how sea urchin diversity affects processes like grazing rates in the Galapagos. Now the focus is shifting higher up the food chain to the things that eat sea urchins. More specifically, does the diversity of urchin predators affect the intensity of predation on urchins? Are there interactions between the different urchin predators that may alter predation rates? My own project aims to figure out to what extent seastars such as Pentaceraster are a part of this predation. The other obvious suspects would be predatory fishes.

Whodunit.

To get some preliminary data on the diversity of fishes (with a special interest in species that could potentially eat urchins), we've been deploying a bunch of Hero GoPro cameras at multiple sites around the central Galapagos archipelago to record 3-4 hours of continuous video data on the fish that are present. These little wearable cameras were originally made for filming high-definition extreme sports videos, but work extremely well as our underwater data-collectors - we've made little stands for them that weight them down on the rock (usually we also stick a few rocks on the stand for greater stability).

Deploying the camera system

GoPro in its natural habitat

During our 5-day research cruise, we collected fish diversity data from 11 different sites, deploying 2 cameras per site for a minimum of 1 hour continuous video data per camera. Video data are easy to collect and accumulates quickly, but it will probably take many more hours in the fall and spring to analyse fish diversity from the raw data.

Here is a one of the more exciting excerpts from Rocas Cousins, a site on the north side of Santa Cruz. How many fish species can you spot? (If you're not too distracted by the charismatic trio of ray, sealion and turtle...)

Salty sotong returns

Back from a five-day research cruise around the central Galapagos archipelago. I write about it briefly on the Brown Global Conversation blog, but more will be up here soon. In the meantime, here is my favourite photo from the trip:

My first frogfish!

Here is a picture of it from the top. It was lying in an urchin hole in the rock wall at Daphne Menor, which is just north of Santa Cruz island.

Project Pentaceraster

I wrote before that my research project here involves figuring out the basic feeding relationships of starfish in the Galapagos subtidal system. This fits into a larger framework of understanding the connections between different species in this system, including economically important species such as carnivorous fish and Leslie's Hexaplex snails, and ecologically important species such as grazing sea urchins and herbivorous fish.

A sampling of starfish species, clockwise from top left: Nidorellia armata (chocolate chip star); Phataria unfascialis (blue sea star); Pharia pyramidata (yellow spotted star); and the ever-awesome Pentaceraster cumingi (Panamic cushion star)

I am focusing my efforts on Pentaceraster for now because we have preliminary evidence that it eats sea urchins, making it a potentially important link in the food web. It is also quite abundant, so it makes up a substantial amount of standing biomass. On our dives, I have been overturning Pentaceraster along the transect to (1) take measurements of their size using my amazing starfish-measurers - I've further modified them a little by taking off a weight and adding a clip to the end; and (2) recording what they are munching on, if anything. Pentaceraster eats by everting its stomach onto its lunch, so it's easy to tell if it is feeding when I overturn it. It is not as easy to ID its lunch as it pulls its stomach back in.

Measuring the radial length (=length of one arm) of a Pentaceraster star. The transect tape is just visible in the top right.

Overturned Pentaceraster retracting its stomach. I go digging through all the bits and find out exactly what's in its mouth.

We also ran a cage trial with a recycled cage from an old experiment. Eventually I am planning to use larger cages to test the effects of including vs. excluding Pentaceraster from an area, but I need to know how well these cages will hold a starfish. We'll be back at this site next week, so I'll be able to see if Mr Pentaceraster has escaped from my setup.

Setting up the cage with Jon.

Final cage setup. One Pentaceraster and five Eucidaris sea urchins (two are clearly visible).

Subtidal again

Over the past couple of days we did our first eight research dives in the Galapagos. I was really excited to finally get back in the water (after being dry for 10 days...snorkelling doesn't really count) and start working. The water temperature here has been around 24-27ºC/75-80ºC which is the coldest I have ever seen in the tropics. But coming from 7ºC/45ºF dives in New England, it was marvelous.

Starting the day with what Jon calls "stuffing your advisor into his wetsuit"

Unlike my New England research sites, all Jon's sites in the Galapagos are only accessible by boat, so our underwater time is much more limited. So we aim to get as much out of our underwater time as possible, which means we are usually doing multiple things on each dive. Jon does his long-term monitoring of permanent wall transects and corals at each site, while Leslie and I work on our individual (starfish and Hexaplex snail) projects.

Working the permanent transect at the Guy Fawkes site.

Leslie taking shell measurements of Hexaplex snails. Plastic calipers courtesy of Sal and the Three Seas Program :)

I finally met one of the focal species of my project up close, face-to-aboral surface. Pentaceraster cumingi, the Panamic cushion star, is a large and fairly abundant seastar that hangs out mostly on the sand, rubble and rock-sand interfaces underwater. I'll be collecting observational data on its size distribution and feeding, and also running caging/tethering experiments to figure out its effects on other organisms in the ecological community. I started on this stuff yesterday - more on this in another post.

Mr. Pentaceraster says hi.

And of course, every research dive has its share of distractions. But the ones in the Galapagos are a lot more flamboyant than the ones in New England...

o hai. im in ur transectz, scaring ur fishz

Down to business

The general theme of our lab's research this summer is to elucidate the trophic (=feeding) structure of organisms that live in subtidal habitat in the Galapagos islands. For example, my project aims to figure out what the different starfish species are eating, and what is eating them, in order to establish their role in the food web. One of the ways we are doing this is using these little extreme-sports wearable cameras (with waterproof housings) to record video of starfish (or other study species) that are tethered within the camera's field of view. We can then analyse the video data to determine rates of predation on the starfish (or urchins, or whatever we're tethering) as well as what ate it. The GoPro cameras with extended battery packs are supposed to give us about 4 hours of continuous data.

The past couple of days has just been assembling these camera systems (and the stands) and testing them out to see how well they work, how much area/distance the cameras cover, etc. We've been snorkelling out around the dock in front of the marine research building of the Charles Darwin Station in Puerto Ayora. Here is a picture of a camera housing on its stand, weighted down by rocks. We were checking for stability and the watertight-ness of the housing on this round.

And this is me with the camera setup. I think I was sticking rocks on the base...or something. (Photos by Leslie)
On the way back from deploying the cameras, we ran into an marine iguana nomming on some Ulva (a green, sheety seaweed). I think I am starting to get used to the iguanas (hard not to when you're just about tripping over them every time you get out of the water...) but I still think they are the coolest things ever.

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