Photos of the Long Island Sound

Research & Monitoring

Status and Trends: LISS Environmental Indicators

Increases in Population and Sewage

Johan Varekamp, Wesleyan University.

Increases in Population and Sewage
C PERF (#/gr) Forams (#/gr)
1996 1400
1992 9083.33
1988 880 5800
1984 1300 5413.79
1975 780 29428.57
1965 330 9857.14
1955 310 21000
1940 250 16692.31
1910 130 16000
1880 150 10000
1850 17428.57
1837 1 5093.75
1820 6 2727.27
1754 6 1559.52
1695 2520.83
1652 1888.89
1594 13 618.78
1530 1 307.89
1462 1 294.91
1382 1 922.48
1311 1 2166.67
1229 6 606.94
1141 23 703.95
1049 33 1048.54
951 62 883.33


Clostridium perfringens (Cperf), a bacterial spore found in sediments, is an indicator of the amount of sewage (treated or untreated) input to the Sound. The bacteria that produce these spores live in the guts of mammals and are capable of surviving sewage treatment. Foraminifera (Forams) are microscopic plants that feed on nitrogen-rich sewage (untreated).


The increase in Cperf reflects the increase in sewage (treated or untreated) entering the Sound as a result of the increase in human population. The increase in foraminifera (forams) is an indicator of more eutrophication, likely fueled by nitrogen-rich, untreated sewage. A decrease in the concentration of forams indicates a decrease in the amount of untreated sewage entering the Sound.


This is a historic indicator which shows a drastic increase in Cperfs and Forams at the end of the Colonial period and at the start of the Industrial period most likely caused by increases in population and sewage producing industries before sewage treatment plants were widespread technology. In recent times Cperfs concentrations have continued to increase due to continual increases in population. Whereas, Forams concentrations has declined most likely due to the building of sewage treatment plants and recent improvements to those plants to lessen the amount of untreated and nitrogen- rich sewage reaching the Sound.


Sediment samples were collected off the Norwalk coast.

Since sewage in coastal waters is often a major source for other contaminants (such as silver, copper, and mercury), measuring spore concentrations is a valuable screening technique for predicting the magnitude and distribution of other contaminants in sediments. (

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