(¹) Earth & Environmental Sciences, Wesleyan Univ, 265 Church Street, Middletown, CT 06459, fax: 860 685 3651,

(²) Center for Coastal & Marine Geology, U. S. Geol Survey, 384 Woods Hole Road, Woods Hole, MA 02543

Presented at: North Eastern Section, Geological Society of America, Regional Meeting, March 12-14, Burlington, VT, Programs and Abstracts 33 (1): A-83

Benthic foraminifera are useful indicator species for monitoring environmental changes in near shore, environmentally stressed regions such as Long Island Sound (LIS), where severe anoxia/hypoxia was first observed in the early 1970s. We compared faunal and isotope data on benthic foraminifera collected in 1999 and 1996/1997 with (1) published records for the early 1960s (Buzas, 1965) and the late 1940s (Parker, 1952), and (2) faunal data collected in cores in western LIS at depths of 9 and 26m (see below). In both cores the number of foraminifera per gram of dry sediment increased dramatically at around 1850 AD. The sediment character changed at this point, and the abundance of benthic pellets increased strongly, as did the number of molluscan shells per gram. The concentration of a sewage indicator, the bacterial spore Clostridium perfringens, increased and the foraminiferal assemblage changed. In both cores, the relative abundance of the herbivorous species Elphidium excavatum increased at about the same time as the foraminiferal abundance. We suggest that these changes around 150 years ago represent the initiation of anthropogenic eutrophication of LIS and of phytoplankton blooms, with increasing numbers of foraminifera as well as increasing relative abundance of a species that consumes fresh phytoplankton. More recent changes in the foraminiferal faunas started in the 1980s, when the relative abundance of Ammonia beccarii increased greatly in western LIS at depths of less than 15m. The species increased in relative abundance at depths greater than 25m only by the 1990s, at which time overall benthic foraminiferal abundances declined. We are not sure whether the increasing abundance of A. beccarii reflects increasing eutrophication and/or hypoxia, or whether increasing temperatures also play a role, but this recent change in faunal composition is unprecedented over the last few hundreds of years.

for results), with red letters and arrows showing locations of 2 cores studied. A1: 8.6 m depth; A4: 25 m water depth. Age models from data on ²¹⁰Pb, ¹³⁷Cs, and pollen (1650 AD: European settlers, ragweed pollen peak indicating land clearance; 1910: chestnut blight).

The two figures below show the relative abundance of the herbivorous species Elphidium excavatum (increasing with time) at the deeper (A4C1) and shallower (A1C1) core site, and the decrease in abundance of the detritivore Eggerella advena (only observed at the deeper location, where this species lives), which temporarily returned to higher abundances in the 1960, when Buzas collected his data.

E. advena decreased in abundance at the same time as increasing metal pollution (Hg), and increasing abundance of the bacterial spore Clostridium perfringens, an indicator for waste water input.

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IWhy would this species ahve increased in abundance? In our earlier work, we speculated that influx of effluent from wastewater treatnet plants (nutrients, specificaly nitrogen) could have been the main cause of the benthic faunal change and increased abundance of A. beccarii. But what exactly caused this increase in abundance? There are several possibilities. Maybe A. beccarii does well at low oxygen conditions (but Eggerella advena and Elphidium excavatum do as well as A. beccarii in laboratory studies). Maybe A. beccarii eats sewage (very well possible; it eats degraded organic matter in the laboratory and is an omnivore as far as we know). Maybe A. beccarii eats phytodetritus that blooms with sewage influx; also very well possible. But there is another possibility: in the laboratory, A. beccarii needs temperatures at bottom >17^oC for more than 30 days in order to reprodce successfully. E. excavatum is a cold-water species. Maybe recent warming has resulted in making it possible for A. beccarii to survive well in the present of abundant food.

There is some support for that hypothesis: in one of the cores (dating uncertain. however), there appear to be high abundances of A. beccarii at about 1000-1200AD, the Mediaeval warm period.

From the early-mid 1800s we see that in Long Island Sound the following things were happening:

• Increasing sedimentation rates
• Increasing pollution (metals, eutrophication)
• Increasing biological productivity (molluscs, foraminifera), probably caused by anthropogenic eutrophication
• Major ecosystem changes

We thus conclude (for the moment):

• That eutrophication and pollution have affected Long Island Sound ecosystems since early-mid 1800s
• There were additional changes in ecosystems in western LIS since the 1970s. Maybe increased eutrophication, maybe increasing temperatures are the cause of these changes.