Please use this identifier to cite or link to this item:
|Title:||Effects of surface texture of articulated concrete mattress blocks on their habitat value|
|Authors:||Environmental Laboratory (U.S.)|
Lower Mississippi River Environmental Program.
Way, Carl M.
Miller, Andrew C.
Bingham, C. Rex.
Payne, Barry S.
|Keywords:||Articulated concrete mattress|
Macro invertebrate community structure
|Publisher:||United States. Mississippi River Commission.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Lower Mississippi River Environmental Program report ; 19.|
Abstract: 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 the 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. Hydropsyche orris was dominated by first instar larvae from May through August, and the population was never dominated by fourth and fifth instars. The midge Rheotanytarsus sp. was dominated by first, second, and third instars during the same time period. The newness of the blocks could have caused larvae to enter the drift soon after attachment, or low water during the study period induced drift followed by recolonization of small instars. In the LMR these blocks provide a stable, hard substrate that is inhabited by macroinvertebrates tolerant of moderate to high velocity water. These organisms on the ACM are important in the diet of fishes and other vertebrates of recreational and ecological value.
|Appears in Collections:||USACE Collection|