Crystal Lake IA 02-IOW-781

Hancock County S15T97NR25W at Crystal Lake.

This is a Legacy Assessment. Prior to 2004, assessments were developed under a methodology that pre-dated the Integrated Report guidelines.

Assessment Cycle

1996

Result Period

1992 - 1994

Designations

Assessment Type

Monitored

Integrated Report

Category 0

Trophic

Hypereutrophic

Trend

Stable

Legacy ADBCode

IA 02-IOW-04095-L_0

Overall Use Support

Partial

Aquatic Life Use Support

Partial

Fish Consumption

Not assessed

Primary Contact Recreation

Partial

Documentation

Assessment Comments

Assessment is based on results of lake surveys and surveys by IDNR Fisheries Bureau.

Basis for Assessment

Used assessments of support of the Class A (primary contact) uses (=PS) and the Class B(LW) aquatic life uses (=PS) developed for the 1994 report. This lake was the first Iowa lake to have a population of eurasian millfoil discovered (1993). According to the March/April 1997 Iowa Conservationist, this infestation has been successfully eradicated.

Monitoring and Methods

Assessment Key Dates

Methods

340	Primary producer surveys (phytoplankton/periphyton/macrophyton)
120	Surveys of fish and game biologists/other professionals
222	Non-fixed-station monitoring (conventional during key seasons and flows)

Monitoring Levels

Biological	0
Habitat	0
Physical Chemistry	2
Toxic	0
Pathogen Indicators	0
Other Health Indicators	0
Other Aquatic Life Indicators	0
# of Bio Sites	0
BioIntegrity	N/A

Causes and Sources of Impairment

Causes	Use Support	Cause Magnitude	Sources	Source Magnitude
Algal Grwth/Chlorophyll a	Overall Use Support	Moderate	Internal nutrient cycling (primarily lakes)	Moderate
Algal Grwth/Chlorophyll a	Aquatic Life Support	Moderate	Internal nutrient cycling (primarily lakes)	Moderate
Algal Grwth/Chlorophyll a	Primary Contact Recreation	Moderate	Internal nutrient cycling (primarily lakes)	Moderate
Nutrients	Overall Use Support	Moderate	Agriculture Natural Sources Sediment resuspension	Slight Moderate Moderate
Nutrients	Aquatic Life Support	Moderate	Agriculture Natural Sources Sediment resuspension	Slight Moderate Moderate
Nutrients	Primary Contact Recreation	Moderate	Agriculture Natural Sources Sediment resuspension	Slight Moderate Moderate
Organic enrichment/Low DO	Overall Use Support	Moderate	Agriculture Internal nutrient cycling (primarily lakes) Natural Sources	Slight Moderate Moderate
Organic enrichment/Low DO	Aquatic Life Support	Moderate	Agriculture Internal nutrient cycling (primarily lakes) Natural Sources	Slight Moderate Moderate
Suspended solids	Aquatic Life Support	Slight	Sediment resuspension	Moderate
Suspended solids	Primary Contact Recreation	Slight	Sediment resuspension	Moderate
Exotic species	Overall Use Support	Not Impairing	Source Unknown	Not Impairing
Exotic species	Aquatic Life Support	Not Impairing	Source Unknown	Not Impairing
Exotic species	Primary Contact Recreation	Not Impairing	Source Unknown	Not Impairing