Biodiversity boosts ecosystem function

Posted on June 26, 2010

Although several studies have shown that the richness of invertebrate species in an ecosystem tends to have a positive effect on primary production, few researchers have examined whether larger-bodied vertebrate species can have a similar impact.  In principle, increases in the richness of fish assemblages should increase primary production because the combined effects of species with different feeding strategies are beneficial – for example in reducing the abundance of grazing invertebrates, increasing the flow of nutrients from land to water by eating insects, increasing nutrient flow by foraging on drifting organic matter, and redistributing nutrients by disturbing the sediment.  A study inOklahomaused experimental channels containing zero to six local fish species selected randomly from a larger pool of twelve species.  In all channels containing fish, total fish density was kept constant.  Primary production over a 42 day period was measured by reference to algal growth on clay tiles placed in each artificial stream, and had a significant positive relationship with the number of fish species.  These results suggest that fish assemblages composed of species with different feeding strategies tend to  show more complementary or facilitating interactions than more uniform assemblages, and support the idea that ecosystem functions and services are likely to be damaged by species extinctions.

Reference:  Hargrave, C.W.   2009.  Effects of fish species richness and assemblage composition on stream ecosystem function.  Ecology of Freshwater Fish 18, 24–32.