Benthic foraminifera: Paleoclimate, marine bioinvasions, and pollution.

摘要

Foraminiferal abundances, stable carbon and oxygen isotopes, and Mg/Ca ratios suggest that the climate of south San Francisco Bay over the past 3900 years has oscillated numerous times between warm and dry, and cool and wet conditions. A colder-water Elphidium excavatum association dominates the core for most of the last four millennia, punctuated by a warmer-water Ammonia beccarii-Elphidium gunteri association which prevailed for about 650 years. Climatic shifts coincident with the onset of the Medieval Warm Period and the Little Ice Age are evident. The nonindigenous foraminifer T. hadai is present in the core-top sediments, and may have been introduced by ballast sediment from a transoceanic vessel.; Analysis of sediment from fully-ballasted and no-ballast-on-board vessels from San Francisco Bay, California, Prince William Sound, Alaska, the Great Lakes, and Chesapeake Bay, Virginia, reveal that foraminifera are indeed entrained with ballast sediment. As many as 17,000 living foraminifera/gram dry sediment were recovered from one ballast sediment sample. The presence of T. hadai in two samples from a vessel that last traveled between the Netherlands and the Great Lakes suggests that not only can a vessel's ballast tanks carry live organisms from its last port of call, but also from previous ports. The species may have been taken up in ballast sediment on a previous journey through China and Taiwan. This has important policy implications for maritime regulatory agencies worldwide.; Also under scrutiny by regulatory agencies are wastewater and sludge discharged into bays near urban settings, such as Los Angeles. Although T. hadai is known to inhabit the ports in the region, analysis of surface and core sediments reveals that the species does not live in shallow water along the coast. A time series of foraminiferal assemblage distributions in Santa Monica Bay suggests that the benthic microfauna has been greatly affected by discharges from the Hyperion Treatment Plant, and that faunal trends improved following remediation. However, not all species have recolonized areas they previously occupied. Temporal variations in foraminiferal abundances, diversity, and spatial distribution of dominant species suggests that foraminifera are a useful tool in defining areas impacted by waste discharge.