The Biodiversity of Benthic Invertebrates


        Particular attention has been paid to the role of ponds in sustaining three groups of organisms: aquatic plants, amphibians and aquatic invertebrates. Williams et al. (2003) has shown that ponds are capable of harboring a wider variety of these organisms than any other form of freshwater habitat such as streams, rivers or ditches. Less attention has been paid to pond biodiversity in the United States than in Europe and the UK, and this remains an important area of future research.
        Aquatic invertebrates, discussed here, are not only highly adapted to particular sets of habitat conditions within ponds, but also may depend on their ability to move among ponds. Regional biodiversity is thus optimized by a) creating a range of microhabitats within individual ponds water depths and sediment types), (e.g., by
ecology_fig43.gif

Fig. 43  (a–left) Locations of 18 ponds sampled for invertebrates in summer 1998.

providing a range of plant species, and b) having a regional landscape with sufficient densities of ponds that occasional movement of invertebrates between ponds is possible. Relatively little is known about the invertebrates of constructed ponds in Chester County; however, a study of natural and constructed wetland ponds in the southeast Pennsylvania piedmont (Fairchild et al. 1999) is used here as a summary of what is known at present. The study area is shown in Figure 43. Although the ponds were designed to enhance wetland functions, many of them resembled farm ponds of the region (e.g., Fig. 44).
        It might come as a surprise that invertebrates with aerial adult stages are in fact very good fliers, and may sometimes travel many miles in search of new pond providing better food or opportunities for reproduction. Flying adults captured at blacklight traps are sometimes used as an indication of just which species of aquatic invertebrates are “on the move”, searching for new ponds. (Fig. 46) .
ecology_fig44.gif

Fig. 44  A wetland pond, built as compensation for wetlands lost during construction of the Rte. 30 By-pass in central Chester County.



Colonization of the newly constructed ponds was rapid (within 2-3 years) for many invertebrates, especially those that are quite common in the region. More specialized invertebrates (for example, those that depend on particular food plants), however, were notably missing at more recently constructed ponds, suggesting that assembly of the complete community may require much longer periods of time, perhaps depending partly on the limited flight capability of some species but also on the development of suitable habitat conditions at the new site.
ecology_fig45.gif

Fig. 45a–f  (a) Diving beetle (fam. Dytiscidae), (b) water scorpion (fam. Nepidae), (c) water strider (fam. Veliidae), (d) midge larva (fam. Chironomidae), (e) damselfly larva (fam. Coenagrionidae) and (f) dragonfly larva (fam. Aeshnidae).

ecology_fig46.gif

Fig. 46  West Chester University graduate student Jay Cruz checking a light–trap for aquatic beetles.