The effect of cattle grazing on the abundance and distribution of selected macroinvertebrates in west Galveston Island salt marshes
Abstract
The effect of cattle grazing on the abundance and distribution of vegetation, burrowing crabs (Uca rapax, Uca pugnax, and Sesarma cinereum), marsh periwinkles (Littoraria irrorata), horn snails (Cerithidea pliculosa), and salt marsh snails (Melampus bidentatus) was evaluated over four seasons (summer 2000, fall 2000, winter 2001, and spring 2001) in grazed and ungrazed treatments. A Galveston Island salt marsh adjacent to Snake Island Cove was sampled at five elevations, from the water's edge to the high tidal flats. Data were analyzed for statistical differences using a two-way ANOVA in SAS. Cattle grazing may affect the vegetation and macroinvertebrate communities in salt marshes through trampling and herbivory. Vegetation resources available to other herbivores are decreased by the direct consumption of plant material by cattle. Spartina alterniflora and Salicornia virginica heights were significantly greater in ungrazed treatments than grazed for every season in the edge, upper, and middle elevation zones. Total aerial vegetative cover was also reduced significantly in grazed treatments, with the greatest impact in the edge and upper marsh. In the ungrazed treatments, S. alterniflora stem density was significantly greater in edge elevations, while both S. virginica percent cover and stem density in the edge elevation was greater. Burrowing crab populations were greater in the upper marsh and edge habitat of ungrazed treatments, while significantly greater in most of the middle marsh habitats of the grazed treatment. Size of burrowing crabs was generally significantly greater in ungrazed treatments. Cerithidea pliculosa size decreased in grazed treatments, but population had an overall increase in grazed treatments. Littoraria irrorata had very few differences between treatments, although few specimens were found. Melampus bidentatus populations were too small to evaluate thoroughly. Macroinvertebrate populations could be used to assess the overall health of grazed salt marshes.
Subject
grazingsalt marsh
Spartina alterniflora
Salicornia virginica
Salicornia bigelovii
Batis maritima
Uca rapax
Uca pugnax
fiddler crabs
Sesarma cinereum
marsh crab
Cerithidea pliculosa
horn snail
Littoraria irrorata
marsh periwinkle
Melampus bidentatus
salt marsh snail
Citation
Martin, Jennifer Lynn (2003). The effect of cattle grazing on the abundance and distribution of selected macroinvertebrates in west Galveston Island salt marshes. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /179.
Related items
Showing items related by title, author, creator and subject.
-
Whaley, Shannon Diann (Texas A&M University, 1997)The relative importance of edge and elevation on infaunal distribution patterns within an intertidal collecting infauna on the nonvegetated intertidal and within the marsh at tina Iterniflora salt marsh was examined by ...
-
Chesnut, John Kent (Texas A&M University, 1989)Not available
-
Sipocz, Andrew Vincent (Texas A&M University, 1993)Wetlands of the San Bernard National Wildlife Refuge (SBNWR) were sampled to investigate environmental factors which influence aquatic macroinvertebrate standing crop and diversity. Sampling occurred monthly between ...