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.

The quiet beauty of mangroves

Tortuga Bay is a beautiful site about an hour's walk from town - it has a long stretch of shore that surfers go to (="the surfers beach") and a protected bay with calm water (="the swimmers beach"), as well as plenty of rocky intertidal zone, a small forest of Opuntia cactus-trees. It's a popular spot with both the tourists and locals (and with Leslie and me who do not fall into either group).

The first time we visited, it was low tide (which we planned for so we could do some intertidal exploration). But when I noticed that the swimmers' beach was surrounded by red mangroves, I was determined to come back and explore it by snorkel at high tide. So we did, and this series of photos is the result. I have gone snorkelling in mangroves before, though I have explored them above water many times back in Singapore. So this was a bit of an adventure.

Red mangroves in the foreground, Opuntias in the back. I love the Galapagos.

Above the water, the roots form a tangled network. The water is still enough to see them reflected on the surface.

Beneath the surface, the sounds of people from the beach fade away and you can almost hear the trees breathing. The visibility is poor in this soft sediment habitat but if you are still and patient (and keep your fins off the bottom!) it clears out enough to make out the somewhat eerie shapes of the submerged roots, and of the fishes hiding in this silent, flooded forest.

A tiny sergeant major emerges, dwarfed by the submerged mangrove roots.

A little bullseye pufferfish peers outward.

Mangroves are known as important 'nursery' habitat - a relatively benign place with calm water and fewer predators for juvenile fish to grow up (including commercially fished food species like snapper - see below). There is definitely a high abundance of little fish here. But there are also bigger shapes lurking in the shadows of the underwater forest. They fade in and out of the murky water and occasionally emerge from among the roots to say hello and to feed in the carbon-rich sediments of the surrounding water.

Dog snappers play hide and seek with me.

Two diamond rays lurk under the shadows of the overhanging mangrove roots. These guys dig about in the sediment and feed on invertebrates living there - check out a video of that here. In the foreground is another bullseye puffer and a young snapper.

Moving out further from the swimmers' beach, the water gets clearer and you can see just how busy the mangroves are.

A buzz of activity.

Further outside of town, El Garrapatero on the southeast side of Santa Cruz has its own mangrove thickets as well - some were growing through/on the basalt (!)

Lone tree on the rocks. There are Opuntias in the background as well.

Pneumatophore roots coming up through the muddy basalt rubble

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.