Effects of Beach Replenishment on the Nearshore Sand Fauna at Imperial Beach, California.
Abstract
This study evaluates the changes in intertidal and shallow subtidal sand-bottom infaunal populations in response to the addition of approximately 765,000 cubic meters of dredged material added to an eroded beach at Imperial Beach, California. A sampling design utilizing small sampling units and extensive replication was effective in generating reliable numerical estimates of infaunal densities and diversity. The dredged material had a high proportion of fine material with lesser amounts of shell fragments. Fine sediments were rapidly transported offshore while shells persisted on the beach. Measured beach effects were short term (5 weeks or less) involving increases in abundance mostly of motile crustacean species which brood their young. Planktonic recruitment of polychaetes was evident during this period. As the fine sediments worked offshore, silt and fine sand fractions increased in the bottom sediments. At subtidal depths, there was a positive correlation between the silt-clay fraction and number of species and abundance. Overall abundance and diversity of the benthos were not adversely affected by beach replenishment. In response to an unpredictable, changing environment (erosion-deposition), most of the resident biota are short-lived, opportunistic species which are typically patchy in distribution both temporally and spatially. Possible longer term effects longer lived species, such as sand dollar populations, were not determined. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1978
- Accession Number
- ADA067308
Entities
People
- Douglas Diener
- Stephen Lacy
- Terence Parr