Tuesday, August 13, 2013

To see a World in a sample of Pond Scum

The strange and weird things one learns from the most mundane circumstances.

The green growths on a stone fished out of the Moira River are colonies of – I'm still not entirely clear which – either a blue-green cyanobacterium called Nostoc parmelioides, or an algae composed of the bacteria.

This organism is symbiotic with a tiny species of midge called Cricotopus nostocicola, the larvae of which develop in the algae, changing its form from small round growths to a semi-circular shapes; both versions can be seen in this picture. The Cricotopus larvae are supposed to be visible within the semi-circular colonies – how large are they, and is my camera's macro good enough to capture an image?

Ancient ancestors of cyanobacteria oxygenated our planet's atmosphere about 2½ billion years ago. Prior to the "Great Oxidization Event" Earth's early atmosphere was believed to consist of gases much like Saturn's moon Titan, hardly conducive for life on Earth as we know it today. The oxygen in the atmosphere also combined with the extant minerals to form new mineral species.

Some cyanobacteria play a role in nitrogen fixation, some are symbionts in lichens, they live in the fur of sloths, and on the negative side they can cause toxic algal blooms. It isn't stretching the truth to say that cyanobacteria were a major force in the shaping of this planet and the life upon it – we literally wouldn't be here without them – and they continue to play significant roles in the tangled webs of its ecosystems.

Re-visting the river a couple of days later in the hopes of finding some Cricotopus larvae, or whatever midge larvae are called ... midge maggots?

Blue-green algae or cyanobacteria ... other than that I have no idea what this stuff is, or even if it's all the same species. Sometimes it's found growing in tangled masses of filaments, or it may be organized in lacy branches.

Still hard at work after billions of years ... the bubbles trapped within this mass of blue-green algae are presumably oxygen. There was also evidence of lots of decayed algae, the decomposition process presumably using up the some of the aforementioned oxygen. Increased amounts of nutrients such as phosphates can cause the cycle of phytoplankton growth and decay to spiral out of control, initiating a process know as hypertrophication.

Getting back to the Nostoc parmelioides cyanobacteria and their Cricotopus spp. insect partners – I removed and examined some of the bracket-shaped growths and the midge larvae are naked-eye visible within the algae. The insect is coiled in a spiral with its head near the center of the circled area. The roughly circular shapes are about 5 to 6 mm across, and the larvae fully stretched out are 3 mm long at the most.

I also dissected a couple of the growths and managed to acquire some half decent macros of the Cricotopus larvae. It's no mean feat to peel the algae apart without damaging or killing the tiny insects using a jack-knife as a dissecting tool.

While studying and photographing the algae it was impossible to miss the uncountable numbers of what appeared to be very small, perhaps 4 mm long, caddis fly casings attached to the rocks at the bottom of the river. The closest match at BugGuide.Net is Brachycentrus appalachia, but it's pushing it to identify these diminutive insects to the species level based on the paucity of detail visible in the pictures.

All this "R&R" – research and reading – because I paused for a moment to indulge my curiosity and photographed some "scum" sprouting on a rock in the river ...