Aggregation of benthic animals in relationship to plant roots, sediments, and four-level spatial scale
A relationship between plant roots and benthic animals was studied in a mesotrophic, dimictic lake. Two field studies were investigated. The first focused on differences in benthic community inside and outside a root zone under selective sampling on three sites. The second tested the same differences but under random sampling in three 9 m plots. All the data were also analyzed against three sediment types. A positive relationship was discovered between presence of plants and num,pers of brown chironomid-related animal groups (chironomids, brown and non-predatory chironomids, chironomid genera and total number of animals) on silty sediment. Also, presence of roots influenced abundance of oligochaetes but with no specific relationship to sediments. Red chironomids and amphipods were related to sediment type when analyzed outside the root zone. Study design influenced results for all the animal groups but especially for predatory chironomids (Tanypodinae). In general, brown and· red chironomids followed different patterns, and distribution patterns of brown chironomid-related groups were similar to ones expected from influence by oxygen released from plant roots. Calculations suggest that the oxygen released from roots could support about 25 chironomids in vicinity of. one plant. It was concluded that brown chironomid-related animal groups might be aggregated around plant roots because of higher oxygen concentrations.