Colonization dynamics of algae in small artificial ponds

Abstract

The arrival, establishment, and growth of a variety of algae were studied in a series of newly established, small (48.5 L) artificial ponds located at three sites of differing characteristics in southern Ontario, Canada: open field, edge of woods, and deep woods. Algal colonization was most rapid at the open site, within 4 days of the ponds being filled, and was slowest at the deep woods site, presumably because of a filtering effect of the surrounding terrestrial vegetation. The patterns of algal colonization and subsequent population abundances were consistent among the ponds, despite very considerable variation in both their physical and biological environments (e.g., among ponds over the 2 years of study, conductivity ranged from 20 to 890 μS, pH from 6.4 to 10.7, dissolved oxygen from 0 to 13.5 mg ∙ L−1, and water temperature from 5 to 29.8 °C). The first colonizers were airborne microchlorophytes, particularly a species of Chlorella, which may have been favoured by clear water (high light) conditions, lack of competition, and an ability to tolerate low nutrient levels. Chlorella populations declined within 1 or 2 weeks, depending on site, coincident with an increase in the numbers of a species of Synechococcus, a cyanobacterium. Synechococcus dominated all the pond types at all three sites thereafter, although its abundance was strongly correlated with water temperatures. In their 2nd year, undisturbed mature ponds developed encrusting algae, especially Rhizoclonium and Oedogonium, on their walls. In years 1 and 2, the densities of Synechococcus in both the new and mature ponds, respectively, were positively correlated with the larval densities of the dominant mosquito species Culex restuans. Synechococcus was the primary item in the diet of these insects. Key words: colonization, algae, habitat variability, Synechococcus sp., Chlorella sp., artificial ponds.