HUMAN-INDUCED MARINE ECOSYSTEM DEGRADATION: MICROPALEONTOLOGICAL EVIDENCE FROM URBAN EMBAYMENTS

It is widely believed that marine ecosystem degradation accelerated about 1800 A. D. when development and industrialization caused the decline and in some cases the collapse of coastal marine communities. However, interannual biological monitoring records rarely exceed 30 years and are often fragmentary. Thus, it is still difficult to document and quantify the complex ecosystem response to human activity over the last several hundred years. Here we show that high-resolution analysis of benthic microfossils (Ostracoda and Foraminifera) from high sedimentation rate coastal sites reveal detailed histories of shallow-marine benthic ecosystem degradation. We will discuss two well-studied examples, Osaka Bay, Japan, and Chesapeake Bay, USA. These embayments are both adjacent to major metropolitan areas and have been experiencing human-induced eutrophication and oxygen depletion in bottom water. In Japan, environmental stress in Osaka Bay began ~1900 and accelerated during economic growth of the late 20th century. Many non-resistant benthic species declined or disappeared and a few resistant species became dominant in this food-rich, low oxygen environment, leading to a “High-density/low-diversity assemblage”. Similar trends are found in the Chesapeake Bay, where ecosystem degradation began by the mid-to-late 1800s and accelerated in the 1900s. The 100-year-delay of the Osaka Bay ecosystem collapse reflects the delayed Asian industrialization compared to European and North American countries. Our presentation will show how microfossils are important paleoecological tools for marine ecosystem history reconstruction.