Influence of trophic role and life-cycle duration on timing and magnitude of benthic macroinvertebrate response to whole-lake enrichment

Phosphorus and nitrogen additions over a 3-year period (1991-1993) significantly increased the abundance of most benthic macroinvertebrate taxa collected on artificial substrates in a small oligotrophic lake in insular Newfoundland relative to a nearby control lake. The speed and magnitude of response was related to both the trophic role and the life-cycle duration of the taxa. This created a response continuum with small, fast-growing herbivores such as sphaeriid clams and gastropods demonstrating more pronounced and more rapid abundance responses than longer lived detritivores such as Ephemeroptera, which, in turn, had quicker responses than long-lived predators. These observations support the hypothesis that these benthic communities are controlled by bottom-up resource processes during the initial years of enrichment and provide the basis for expecting future enhancement of benthivorous salmonid populations in the fertilized lake.