Nutrient spiralling in streams.

Before we consider how stream animals influence the dynamics of nutrient turnover in streams, we have to consider some special features of this ecosystem. As we saw in chapter 3, the most distinctive feature of stream and river ecosystems is water flow. Jack Webster (1975) was the first to point out that because nutrients in streams are subject to downstream transport, there is little nutrient cycling in one place. Water currents move nutrients downstream. Webster suggested that rather than a stationary cycle, stream nutrient dynamics are better represented by a spiral. He coined the term nutrient spiralling to describe stream nutrient dynamics (fig. 20.16).