Aquatic Plant Survey

Lake: Blackwater Lake

Vegetation Data Sheet Aquatic Vegetation Assesment Survey Survey Date : Sept. 6, 2005

As of September 2005, Blackwater Lake contains a moderately diverse plant community with no exotic or invasive species such as Curlyleaf pondweed or Eurasian watermilfoil. Of the total three surveys conducted, Chara was found to be most abundant followed by Bulrush, Water lily, and Floating-leaf pondweed. These plants may be causing navigational problems but cause no harm to the ecosystem of the lake and are actually helping to keep the lake healthy and diverse.

Lake: Blackwater LakeVegetation Data Sheet Aquatic Vegetation Assesment Survey Survey Date : Sept. 6, 2005CodeNo Plant Name3 Chara 5 Flatstem pondweed 7 Claspingleaf pondweed 9 Richardsons pondweed 11 Large leaf pondweed 13 Floating leaf pondweed 17 Northern watermilfoil20 Coontail 44 Water Lily 39 Cattail40 Bulrush 41 Wild Rice

Total # Diff. Plants

Aquatic Plant Surveys of September 2005, Blackwater Lake contains a moderately diverse plant community with no exotic or invasive species such as Curlyleaf pondweed or Eurasian watermilfoil. Of the total three surveys conducted, Chara was found to be most abundant followed by Bulrush, Water lily, and Floating-leaf pondweed. These plants may be causing navigational problems but cause no harm to the ecosystem of the lake and are actually helping to keep the lake healthy and diverse.

Total # Diff. Plants

Table of Contents

AVAS 2

Algae 2

Muskgrass 2

Submersed Plants 3

Flatstem pondweed 3

Claspingleaf pondweed 3

Richardsons pondweed 3

Largeleaf pondweed 3

Northern watermilfoil 3

Coontail 4

Elodea 4

Sago pondweed 4

Floating-leaf pondweed 4

Emergent Plants 4

Cattails 4

Bulrushes 5

Wild rice 5

Floating-Leaved Plants 5

Water lily 5

Point Intersect Vegetation Survey 6

Conclusion 6

AVAS

On July 18, 2005 and September 6, 2005 an AVAS vegetation survey was conducted by Professional Lake Management on Blackwater Lake, Cass County, Minnesota. The AVAS method of surveying is a survey that is carried out by sampling individual Aquatic Vegetation Assessment Sites (AVAS’s) throughout a lake’s littoral zone. The locations of AVAS’s are determined by dividing up a lake’s shoreline into segments approximately 100 to 300 feet in length. Each AVAS is sampled by using visual observations; dependent upon water clarity, and weighted rake tows. Each separate plant species found in each AVAS is recorded along with an estimate of each species’ density. Plant species are identified using the numbers designated on the survey map’s plant species list, and densities are recorded by using the following code:

(a) = found: one or two plants of a species found in an AVAS, equivalent to less than 2% of the total AVAS surface area.

(b) = sparse : scattered distribution of a species in an AVAS, equivalent to between 2% and 20% of the total AVAS surface area.

(c) = common: common distribution of a species where the species is easily found in an AVAS, equivalent to between 21% and 60% of the total AVAS surface area.

(d) = dense : dense distribution of a species where the species is present in considerable quantities throughout an AVAS, equivalent to greater than 60% of the total AVAS surface area.

Table 1. Plant Species Found in Blackwater Lake

Common Name Scientific Name

This type of survey allows us to do a quantitative measurement of the vegetation in the lake. With this survey, Professional Lake Management found that the macrophyte community of Blackwater Lake is moderately diverse with nine species of submersed plants, one species of floating-leaved plants, three species of emergent plants, and one species of algae (Table 1). Of these plants, all are native North American Species. These native plant species benefit the lake, performing such functions as stabilizing sediments and providing habitat for fish and other aquatic organisms. If they do become substantially tall and dense, they may cause problems usually in isolated areas.

Algae

Muskgrass

Muskgrass, more commonly called by its scientific name Chara is a mass of light green stem-like branches with forked leaves. It grows entirely under the water. If pulled out of the water, it has a distinct skunk-like smell and a gritty, bristly feeling. This type of algae is found worldwide. It stabilizes bottom sediments and provides food for waterfowl s well as cover for fish. Chara also supports small aquatic animals, which are important food for fish. Chara is represented in the majority of the littoral area of Blackwater Lake. It represented 73.2 percent in July and increased to 76.6 percent by September.

Submersed Plants

Flatstem pondweed

This aquatic plant is identifiable by its large flattened stem with ribbon-like leaves extended upwards. It is a native plant found throughout the United States. The plant aids in providing some cover for bluegills, perch and northern pike, while also providing food for waterfowl. In July the plant represented only 1.1 percent of the littoral area, found generally in the east and southwest bays of the lake. By September the plant had died out naturally, representing zero percent of the littoral area. A littoral area is the area suitable for aquatic plant growth, mainly the shoreline.

Claspingleaf pondweed

Its wide wavy leaves can identify this pondweed. It is often confused with Curlyleaf pondweed, but Curlyleaf pondweed has more waves and small “teeth” along the leaf edges where Claspingleaf does not. This plant is native to the United States and provides habitat for panfish, largemouth bass and northern pike, while walleyes use them for cover. In July the plant represented 3.1 percent of the littoral area decreasing naturally to 1.2 percent by September. This plant was scattered throughout all the littoral area.

Richardsons pondweed

Richardsons pondweed is basically a smaller version of Claspingleaf pondweed. It is also native to the United States and is identifiable by its more tightly bound smaller leaves and its straighter stem than Claspingleaf pondweed. It provides the same habitats as Claspingleaf pondweed and in July the plant represented 4.6 percent of the littoral area, found scattered throughout the lake. By September the plant had naturally decreased to 1.6 percent, still scattered throughout the littoral area.

Largeleaf pondweed

This plant is identifiable mainly by its large oval shaped yet wavy leaves. The plant seldom branches and often looks brown due to mineral deposits on the leaves. It is found mainly in the northern part of the United States. This plant also provides good habitat for panfish, largemouth bass, and northern pike, while also providing cover for walleyes. Largeleaf was found throughout the lake, representing 6.8 percent of the littoral area in July decreasing naturally to 4.7 percent by September.

Northern watermilfoil

Northern watermilfoil is identifiable by its feather-like leaflets arranged around a buff or pink colored stem. It is different from Eurasian watermilfoil because it has less branching and less leaflet pairs. If removed from the water, Northern watermilfoil remains rigid, but Eurasian will fall limp. The plant is native to the United States and provides cover for fish and invertebrates. It also supports insects and other small animals eaten by fish. Northern watermilfoil represented only 1.7 percent of the littoral area in September and decreased naturally to only 0.1 percent by September. The plant was scattered throughout the lake.

Coontail

This plant, found throughout the United States, is similar to milfoil, but its leaves are spiny and forked rather than feather-like. Coontail leaves tend to bunch at the tip giving it a raccoon tail look. It is a food source to many waterfowl species and provides cover for bluegills, perch, largemouth bass, and northern pike. It also supports insects that fish and ducklings eat. This plant if not monitored may grow profusely causing navigation problems. Blackwater Lake, however, is not threatened by overgrowth of this plant. In July and September it only represented 0.1 percent of the littoral area.

Elodea

Elodea is identified by its very small oval-shaped clustered leaves arranged very tightly around branched stems. It is dark green and can form a large mass near the lake’s bottom. It is found in northern and north central states. This plant provides habitat for small aquatic animals, which fish and wildlife eat and is an excellent oxygen producer, needed for fish survival. Elodea only represented 0.1 percent of the littoral area in July and was not found by September. It was only found in the east bay of the lake.

Sago pondweed

This plant is bushy in appearance with narrow thread-like leaves alternately arranged. It is found throughout the United States and is a valuable food source for waterfowl. It also provides some cover for bluegills, perch, northern pike and walleyes. Swans, geese and diving ducks favor the seeds of Sago pondweed. Sago represented 1.2 percent of the littoral area in July and decreased naturally to 0.9 percent by September. The plant was found throughout the lake.

Floating-leaf pondweed

This plant, found throughout the United States, has slightly heart shaped leaves on top of the water, and more slender leaves below the water. On Blackwater Lake it is found mostly mixed in the Bulrush and the Water lilies. It often grows in patches and provides habitat for panfish, largemouth bass, and northern pike. The plant represented 5.9 percent of the littoral area in July and increased to 8.6 percent by September, but should start decreasing with cooler weather.

Emergent Plants

Cattails

A Cattail is recognized mostly by its brown fuzzy flower, but also consists of a long stalk and thick roots. Cattails are found throughout the United States and help stabilize marshy boarders of lakes. Northern pike may spawn along the Cattails, while the plant also serves as habitat for waterfowl. Muskrats and beavers will eat the stalks and roots as well. Cattails represented 6.5 percent of the littoral area in July and probably due to wind and animal damage, decreased to 4.7 percent by September. Navigational difficulties may have also decreased the percent of Cattails due to increased difficulty in viewing the plant during the September survey.

Bulrushes

Bulrush is identified as long, tall stems inhabiting shallow waters along the shoreline. Bulrush is found throughout the United States and is the plant causing the most navigational problems for Blackwater Lake. Although a nuisance for navigation, Bulrush provides and excellent fish habitat good for spawning. Bulrush also provides food for ducks, geese, and swans. This plant represented the second largest percent of littoral area at 40.2 percent in July and 41.9 percent by September.

Wild rice

Wild rice is most easily identified by the red or yellow grains at the tip of the stalk in August, but before that it is recognized by clusters of green, ribbon-like leaves which float on the water surface during late spring and early summer. Wild rice can be found in northern United States. Wild rice is a food source for wildlife and humans and can provide nesting cover for waterfowl. Wild rice was not very prevalent in Blackwater Lake and only represented 0.4 percent of the littoral area in July, and 0.9 percent by September.

Floating-Leaved Plants

Water lily

This plant is recognized by its large floating leaves, purplish-red underneath, and white flowers all attached to an underground system of tubers called rhizomes. Water lilies are found throughout the United States. Lilies provide habitat for largemouth bass and sunfish, while waterfowl eats the seeds. Blackwater Lake had 17.5 percent of its littoral area as Water lily in July, increasing to 18.9 percent by September. This made lilies the third most popular plant in the lake.

Point Intersect Vegetation Survey

Table 2.

Plant Name	Total Number of Sites	% Occurence of all 91 Points	% Occurence of the 43 Points with Vegetation
Chara	38	42%	88%
Flatstem Pondweed	10	11%	23%
Claspingleaf Pondweed	8	9%	19%
Richardsons Pondweed	3	3%	7%
Large Leaf Pondweed	6	7%	14%
Floating Leaf Pondweed	9	10%	21%
Northern Watermilfoil	3	3%	7%
Coontail	7	8%	16%
Water Lily	9	10%	21%
Cattail	1	1%	2%
Bulrush	17	19%	40%
Wild Rice	1	1%	2%

Also on September 6th, a point intercept vegetation survey was conducted. In this survey a grid of 91 points were placed 154 meters apart on a map of Blackwater Lake (Figure 2). Using GPS coordinates, the points were found by the surveyors and a sample of the plants was brought up at each point using an aquatic pull rake. A chart with a list of aquatic plants was then used to identify which plants were present or not present at each site. This survey is not a quantitative or density dependent survey, it allows only seeing what plants are present at specific points.

The results are summarized in Table 2. Of the 91 sites, only 43 sites actually contained vegetation. Chara was found in the largest number of sites, while Wild rice and Cattails were only found in one site. Bulrush came in with the second largest number of sites. These results are similar to the results obtained from the AVAS survey. This survey again only represents the 91 points 154 meters apart rather than the entire littoral area, but it is nice in providing support for the AVAS survey.

Conclusion