Wonderfalls Pond Micro-Life Notes
Big or small, ponds soon become ecosystems teeming with life. Too much light or not enough oxygen will encourage bacteria and algae at the expense of everything else. To achieve shade in the sun, floating plants help greatly and underwater plants such as Anacharis, Cabomba and Parrot’s Feather consume nutrients that feed algae. So shade is good, and water flow, especially over rocks, will mix the water with air and replenish oxygen. Changing the water, or using chemicals to try to control algae will wipe out your ecosystem. On the other hand, the longer the healthy water remains, the greater the diversity of animals and plants within, even if you don’t see them.
These photographs were taken of creatures found in just 50 ml of water from in my pond, using a phase contrast microscope. All photos are phase contrast, except 9 and 12, which are darkfield images. The magnification is shown in the table (“Mag.”). In some (7,9,10) rotifers are attached to small plant stalks, and in the low-power image (9) dozens of rotifers can be seen attached to a stalk. In others (7,8), algae cells are easily seenin the gut of the rotifers, showing how these tiny animals help clean the water.
In most slides many single celled algea (Chrosphytes, Euglanophytes, Chlorophytes and Baccillariophytes) can be seen. Rotifers like to eat them and you can see them in their gut (eg slide 08). Bacteria are visible as dark dots or tubes, but are not abundant, a good sign. Filamentous green or blue-green algea are also not common, another good sign since these are the bacteria that will flourish in poorly oxygenated or overly sunlit water at the expense of everything else. Amoebas and actinods are single-celled organisms, from the Kingdom Protoctista. There are 5 Kingdoms; the Bacteris, Protoctista (single celled eukaryotes), Fungi, Plantae and Animalia. All are represented in your pond! There are 30 phyla of living things, the next division from Kingdom. Rotifers have their own phylum, Rotifera, and there are about 200 described species, mostly found in freshwater. They are among the smallest multicellular animals, not larger than a millimeter. They feed by creating a water current with a ring of hairs (cilia) found at their anterior end (giving them their name), hauling in algea and bacteria which are ground with a muscular pharynx. Next up the food chain, Daphinia is a common genus of ‘water fleas’, which are really more closely related to shrimp than insects. They are filter feeders, which at their size means they will be feeding on algea and larger organisms, including free-swimming rotifers. Daphnia in turn becomes a main food source for larger invertebrates such as water beetles and small vertebrates such as tadpoles and small fish.