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West Battle Lake Aquatic Vegetation Survey

West Battle Lake Aquatic Vegetation Survey

Introduction
DOW Number: 56-0239-00 Date of inspection: June 26-29, 2017 Observers: Emelia Hauck, Laura Geyen
Date of report: August 7, 2017
West Battle (DOW 56-0239-00) is a large 5,565 acre lake located in Otter Tail County near Battle Lake, MN. According to the Department of Natural Resources, West Battle has a maximum depth of 108 feet and contains a littoral area of about 2,496 acres which permits light penetration and allows plant growth.

West Battle is classified as a eutrophic lake as measured last in 2016 by mean secchi depth of approximately 12.9 feet throughout the lake. Total phosphorus and chlorophyll-a (values that provide a measure of the amount of algae in the water) are considered low with mean values 11.3 and 3.2 ug/L of West Battle (Table 1).

Objectives of Survey
This survey describes the aquatic plant community of West Battle including:
1) Vegetation data to include; sample point number, depth, plant taxa observed, and the
estimated abundance of each taxon.
2) Identification of taxa to the level of species when possible.
3) Frequency of occurrence of each taxon found, stating the number of points used as the
denominator for the calculations.
4) Combined frequency of all aquatic plants found
5) Estimation of maximum depth of submersed vegetation
6) Estimation of abundance of species sampled using MN DNR ranking system
7) Distribution map for common species
8) Determination of any invasive aquatic plants

Methods
The point-intercept survey followed methodology described by Madsen (1999). Geographic Information System (GIS) software was used to generate sample points across the littoral zone in 120 by 120 meter grid resulting in a total of 941 potential survey points on West Battle. In the field, all points were sampled and 10 were added. Vegetation was not found beyond 19 feet in depth. A Global Positioning System (GPS) unit was used to navigate the boat to each sample point. Water depths at each site were recorded in 1-foot increments using an electronic depth finder.
A double-headed, weighted garden rake, attached to a rope (Figure 1 and 2) was used to survey vegetation. Vegetation that was found under the surface by use of the double-headed garden rake was assigned a number between 1 and 4; 1 being rare (≤ 1/3 of the rake head covered), 2 being scattered (>1/3 but ≤ 2/3 of the rake head covered), 3 being common (> 2/3 of the rake head covered), and 4 being abundant (plants over top of rake head). Plant identification followed Blickenderfer (2007).