| The nearshore areas, or littoral zones, of Boreal Shield lakes are areas of enriched diversity and productivity, and depend heavily on input of organic matter from the terrestrial ecosystem to maintain this high productivity. This study used an industrially disturbed watershed near an abandoned metal smelter in Sudbury, Canada; a watershed in the early stages of re-vegetation after decades of severe soil erosion and near barren plant cover, to test the prediction that the increased export of organic matter promotes recovery of nearshore invertebrate communities and key ecosystem functions such as leaf litter decomposition. The response of macroinvertebrates to intensive land reclamation efforts by industrial and community groups (aerial soil liming, fertilizing, seeding) was assessed in a 39 ha experimental catchment where treatments began in 1994. Surveys of stream water quality, particulate matter exports, nearshore macroinvertebrate communities, and leaf litter decomposition were then conducted across a series of catchment areas that differed in forest and soil conditions to develop regression models relating the characteristics of the recovering landscape to patterns in nearshore macroinvertebrate communities.;Discharged water from the experimental catchment provided lower doses of acid and metals to macroinvertebrate communities living at the stream-lake confluence and contributed significantly higher amounts of particulate matter, relative to an adjoining control catchment. Based on stepwise multiple regression models, increased fine particulate organic matter (FPOM) export was associated with increases in the Simpson Diversity of nearshore macroinvertebrates across the nine studied catchment areas. Catchments with more forest area (ha) exported higher total amounts of FPOM, while catchments with more wetland area (ha) exported a higher quality of exported particulate matter in terms of proportion of FPOM in the sediments that were deposited in the confluence sites. Decomposition of leaf litter was mainly by microbial rather than macroinvertebrate activity, and increased with improved drainage water quality from the catchment areas. From these demonstrated terrestrial aquatic linkages, it is clear that biological communities in lakes of smelter impacted watersheds will not fully recover without first restoring the wetlands and forests of the associated catchment areas. |
