|Assessing invader roles within changing ecosystems: historical and experimental perspectives on an exotic mussel in an urbanized lagoon|
Crooks, J.A. (2001). Assessing invader roles within changing ecosystems: historical and experimental perspectives on an exotic mussel in an urbanized lagoon. Biological Invasions 3: 23-36
In: Biological Invasions. Springer: Berlin. ISSN 1387-3547, more
It is often difficult to accurately assess the long-term effects of invaders because of a lack of data and the changing nature of ecosystems. However, available historical information can be used to make comparisons with current conditions and generate hypotheses that can be tested experimentally. This approach was used to examine changes in the bivalve community of Mission Bay, San Diego, California, USA.A20-year dataset on subtidal bivalves shows a marked increase in abundance of the exotic mussel Musculista senhousia, and concomitant declines in species richness and the abundance of the native Solen rostriformis. Currently, Musculista also dominates the tidal creeks of a remnant salt marsh and an adjacent restored marsh, and is 100 times more abundant than any native bivalve species. A comparison of the bivalves now present in the remnant marsh creek to the community present 35 years ago demonstrates that while Musculista increased in abundance, the native Chione fluctifraga disappeared from the creek. In the same time frame, two other natives, Macoma nasuta and C. undatella, appeared in the system. Experiments demonstrate that the growth and survivorship of the surface-dwelling, suspension-feeding Chione spp. significantly decrease in the presence of Musculista, whereas the deeper-dwelling, deposit-feeding Macoma nasuta shows no such inhibition. Viewing these results in the broader context of physical change within the wetland explains some patterns of observed change and suggests effects due at least in part to Musculista, but also demonstrates the complexities associated with assessing long-term patterns in systems affected by multiple factors.