Effects of Surface Texture of Articulated Concrete Mattress Blocks on TheirHabitat Value. Lower Mississippi River Environmental Program Report 19

摘要

The effects of minor alterations to the surface of articulated concrete mattress(ACM) blocks, used to protect the banks of the Lower Mississippi River from erosion, were examined with laboratory and field studies. Field studies were conducted at Marshall Point, RM 446.8, Issaquena County, Mississippi, on 18 July 1989 and at False Point Revetment, RM 443.1, Madison Parish, Louisiana, on 5 July 1990. Rough surfaces created a drag on moving water and increased turbulence in a very thin layer just above th surface of the block. Grooved surfaces provided velocity shelters for caddisflies and other macroinvertebrates. Total macroinvertebrate density on grooved blocks (3,882 individuals/sq m) was 2.3 (p < 0.01) and 1.6 (p < 0.01) times greater than on smooth (1,725 individuals/sq m) and rough (2,411 individuals/sq m) blocks, respectively. Density of trichopterans on grooved blocks (2,888 individuals/m2) was significantly greater (p < 0.05) than on rough or smooth blocks. Most trichopteran cases and feeding nets were in the grooves and not the smooth area between grooves. Chironomidae and Trichoptera comprised more than 98 percent of the total macroinvertebrate fauna after the blocks were in the river for 7 days; densities of these two groups equaled 6,972.5 and 8,671.0 individuals/m2, respectively.... Articulate concrete mattress, Macroinvertebrate community structure.