Nutrient Reference Conditions in New Jersey Lakes Based on Analysis of Sediment Cores: Research Project Summary
Date
2016-08
Date Removed
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Trenton, N.J. : New Jersey Department of Environmental Protection, Division of Science, Research and Environmental Health
Abstract
This project was conducted to more accurately quantify reference water-quality conditions in New Jersey (NJ) lakes. An
accurate quantification of reference conditions is required to support the development of numeric nutrient and other
biological criteria needed in setting realistic targets for protection and restoration plans. This project provided data on
historic lake nutrient conditions, including undisturbed natural conditions characteristic of the pre-European settlement
period. The project had two main objectives: 1) quantify reference (pre-European settlement) trophic conditions and 2)
assess the amount of change induced by anthropogenic activities on lake nutrient concentrations using diatom-based
inference models. To reach these objectives, sediment cores have been collected and analyzed for diatom species
present in the top core interval (present-day conditions) and bottom core interval (past lake conditions, could represent pre
– or post-European). The field crew aimed to obtain 1-m long cores, which based on scientific literature should reach preEuropean time in lakes from the northeastern USA. Two steps were used to determine if core bottom intervals
represented the pre- European time period for each specific site: 1) pollen composition and relative abundance of
Ambrosia pollen; and 2) radioisotope dating. Pb-210 radio isotope dates were used to determine if the core bottom
intervals were older than ~100 years, which is the oldest age that Pb-210 can provide. Results suggest the core bottom
sediments in most of the lakes were deposited at least 100 year ago; these core bottoms, may or may not reach preEuropean time period. The Ambrosia pollen is a well-known chronomarker for the European settlement. Since settlement
was marked by extensive forest clearing and replacement of clear-cut areas by Ambrosia plants, pollen counts of
Ambrosia were used to determine if the bottom core was deposited before or after the European arrival. Bottom sediment
samples from a few cores had Ambrosia pollen as high as 36 percent suggesting that they did not represent a time period
prior to European settlement, while other bottom intervals had pollen assemblages atypical from today, without invasive
species and with very low concentrations of Ambrosia pollen suggesting they represent the pre-European settlement time
period . A total of 122 diatom samples were analyzed in top and bottom core intervals. Overall, top core sediment
samples (representing current conditions) are rich in Fragilaria crotonensis, Asterionella formosa and Fragilaria capucina.
These species are indicators of eutrophic conditions. Core bottom sediment samples are dominated by Cyclotella
michiginana, a species indicative of low total phosphorus concentrations. The average diatom-inferred total-phosphorus
concentration from all surface samples is 48 µg/L. The historic average diatom-inferred total-phosphorus concentration
determined from all core bottom samples is 24 µg/L, just less than half of the current water quality standard for NJ. Total
phosphorus estimates in bottom sediment samples were typically higher in impoundments than from natural lakes.
Description
Prepared by Mihaela Enache, Ph.D.
Keywords
New Jersey, Lakes - New Jersey