Determining trophic state in Lake Whatcom, Washington (USA), a soft water lake exhibiting seasonal nitrogen limitation

Document Type

Article

Publication Date

1-2002

Keywords

lake trophic state, nitrogen limitation, N/P ratios

Abstract

We evaluated an eleven year data set to assess trophic state and nutrient limitation in Lake Whatcom, an oligotrophic, soft water, chain lake located in the Puget Sound lowlands of Washington (U.S.A.). Although total phosphorus (TP) and soluble reactive phosphate (SRP) concentrations were relatively low throughout the lake, there were significant differences between the northern basin (Site 1) and the other sampling sites (Sites 2–4). Nonparametric correlation coefficients (Kendall's τβ) were highest between chlorophyll (CHL), Secchi depth (SD), total nitrogen (TN), and dissolved inorganic nitrogen (DIN). Late summer algal biomass correlated best with DIN and TP. Trophic State Indices based on TP, TN, CHL and SD revealed that although algal growth was most likely phosphorus limited throughout the year, the northern basin of the lake may have developed nitrogen co-limitation during late summer and fall. During this period, N/P ratios were often less than 20, and in 1998 the epilimnetic DIN concentrations dropped below 20 μg l−1 while DIN/TP ratios fell below 4. Reviews of the literature suggest that while co-limitation by phosphorus and nitrogen is fairly common in unproductive lakes, the patterns seen in Lake Whatcom were more similar to those reported for eutrophic lakes experiencing secondary nitrogen limitation resulting from excess phosphorus loading.

Publication Title

Hydrobiologia

Volume

468

First Page

107

Last Page

121

DOI

https://doi.org/10.1023/A:1015288519122

Subjects - Topical (LCSH)

Nitrogen--Environmental aspects--Washington (State)--Whatcom, Lake; Water quality--Washington (State)--Whatcom, Lake; Phosphorus--Environmental aspects--Washington (State)--Whatcom, Lake

Geographic Coverage

Whatcom, Lake (Wash.)

Type

Text

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Language

English

Format

application/pdf

Link to Full Text

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