Technical Report No. 25

QUANTIFYING THE IMPACTS OF AN INVADER: THE ASIAN MUD SNAIL BATILLARIA ATTRAMENTARIA ON THE MUD FLATS OF PADILLA BAY, WA.

Mary O'Connor, Marjorie Wonham and Christopher Harley

December 2001

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Bibliographic Citation
O'Connor, Mary, Marjorie Wonham and Christopher Harley. 2001. Quantifying the impacts of an invader: The Asian mud snail Batillaria attramentaria on the mud flats of Padilla Bay, Wa. Washington State Department of Ecology (Publication No. 02-06-016), Padilla Bay National Estuarine Research Reserve Technical Report No. 25. 35 pp.

Abstract
The impacts of biological invasions are costly to human economy and global biodiversity. It is important to measure and understand the ecological impacts of alien species in order to work toward the development of a predictive science of invasions. This study seeks to experimentally quantify the impact of the nonindigenous Asian mud snail Batillaria attramentaria on the soft sediment community of Padilla Bay, Washington. In order to do so, we studied the range, abundance and ecological effect of the invader. Mud snails were excluded from areas of the mud flat using small fences. Two experimental designs were employed, one the included sites throughout most of the bay, and one with replicated treatments concentrated at one site to minimize habitat heterogeneity. Response variables were sediment chlorophyll a concentration, sediment particle size, per cent cover of eelgrass and macrofauna densities. Batillaria removal led to a decrease in Z. japonica cover after five months. Particle size distributions, chlorophyll a concentrations and infauna populations did not change significantly, but apparent patterns suggest complex interactions with the mud snail. Study site data describe parts of Padilla Bay in detail.