Confederated Tribes of the Colville Reservation

Surface Waters Monitoring Program

Joe Peone, Program Director

Gerry Marco, Fishery Biologist

The Littoral Community of Buffalo Lake: Changes in Macrophytes as an Indication of Trophic Trends with Implications to the Lake Fishery

By

Judith Loescher

Edmond Broch

Department of Zoology

Washington State University

1 June 1996

(17 September 1996 Revision)
The Littoral Community of Buffalo Lake: Changes in Macrophytes as an Indication of Trophic Trends with Implications to the Lake Fishery

By

Judith Loescher

Edmond Broch

INTRODUCTION

Buffalo Lake, a 218.6 ha closed basin, freshwater lake on the

Colville Indian Reservation, has supported abundant growths of aquatic macrophytes in recent years. Harkness, et al. (1974) reported dense growths of an unidentified species of milfoil (Myriophyllum sp.) growing in a band around the lake. In late summer the plant was a nuisance to boating and swimming activities near the shore.

As a result of reports of suspected Eurasian watermilfoil (Myriophyllum spicatum L.) populations, a 1983 survey (Broch, Ahl and Loescher, 1983) of Buffalo Lake was conducted. It confirmed the presence of Eurasian watermilfoil while identifying macrophyte distribution in the lake. A follow-up survey was conducted in 1984 to determine the direction and extent of Myriophyllum spicatum in Buffalo Lake (Broch and Loescher, 1984).

In 1994, while collecting water samples for the continuing monitoring of Buffalo Lake, Edmond Broch observed changes in the aquatic macrophyte populations of the lake. Therefore, on July 17-18, 1995, we conducted a survey of the macrophytes with particular attention to the abundance and condition of Myriophyllum spicatum in the lake.

The Colville Confederated Tribes Monitoring Program provides an extensive database which may shed light on the causes of any change in the macrophyte community as well as on possible changes in the trophic nature of Buffalo Lake. In addition the existence of such a database provides an unusual opportunity to interpret changes in the population structure of Eurasian milfoil within the macrophyte community since the 1984 study.

The database of the Limnology of the Lakes of the Colville Reservation is available on the World Wide Web. The entire database can be viewed at URL (). The Database pertaining to Buffalo Lake can be viewed at .

METHODS

The aquatic plant community was sampled with a spring steel rake head attached to a 15 m Dacron line. The rake was dropped into the water from an Avon SR-4 hard-bottomed inflatable boat equipped with a motor along transects established in earlier aquatic macrophyte studies (Broch, Ahl and Loescher, 1983; Broch and Loescher, 1984), samples were taken at meter depth intervals from depths ranging from 2 to 9 m. Sampling was done parallel to shore along a single depth contour with the boat moving at approximately 2 knots, a speed slow enough to keep the rake dragging on the lake bottom. Sampling depths were measured by Sonar using a Lowrance X-16 and Lowrance 350A depth sounders. The rake was also used to retrieve plant materials from sites not on the established transects. The map of Buffalo Lake (Fig. 1) shows the locations of the sites sampled and the transect locations.

Figure 1. Map of Buffalo lake showing sampling locations (Depth contours are given in feet.)

After collection, the macrophytes were bagged, labelled, and placed in an ice chest for transport to the laboratory. There they were identified within a few days using Hitchcock and Cronquist (1973), Ceska and Ceska (1986), and Imahori and Wood (1965) as primary resources.

After collection, the macrophytes were b

Pressed plant material was deposited in the Marion Ownbey Herbarium of Washington State University, Pullman, Washington.

Measurements of temperature and oxygen concentration were made using a Yellow Springs Instrument Co. Model 58 temperature/dissolved oxygen probe. Secchi disk transparency readings were made at Stations A and B, the same stations used in the ongoing (1990 to present) nutrient monitoring study conducted by Broch.

RESULTS

The aquatic macrophytes found in Buffalo Lake, together with the locations and depths at which each was found, are presented in Table 1 below:

TABLE 1. BUFFALO LAKE TRANSECT SITES BY BAYS.

Data indicates locations (bays) and depths (in meters) at which macrophytes and macroalgae were found. Aquatic plants were not found in transects from bays B, G, and M.

	A	C	D	E	L	N
macroalgae
Chara sp.	<0.3	1-1.2			1.5-2.0	1.0
Nitella sp.	<0.3	1-2.0	1.2	1-2.0	1.5-2.0
unidentified charophytes		1.6		1-2.0
Spirogyra sp.		2.0
emergents
Eleocharis acicularis L. (R. & S.)		1.2
Eleocharis palustris L. (R. & S.)		<1-2.0
Glyceria sp.		<1-2.0
Polygonum sp.	<1
Sagittaria cf. teres Wats.				1.0
Scirpus acutus Muhl.		<1-2.0
submersed macrophytes
Ceratophyllum demersum L.					2.0	1.0
Elodea canadensis Rich.		<1-1.6		0.7-2.0	2.0	1.0
Elodea cf. nuttallii (Planch.) St. John				1.0
Myriophyllum sibiricum Kom.		<1-1.2		0.7-2+	2.0	1.0
Najas flexilis (Willd.) R. & S.		1.6
Potamogeton sp.			<1-1.0
Potamogeton foliosus Raf.		<1-1.6		0.7-2.0
Potamogeton gramineus L.				1.0
Potamogeton pectinatus L.				0.7-1.0
Potamogeton praelongus Wulf.				2+	2.0
Potamogeton pusillus L.				0.7-1.0
Potamogeton richardsonii (Benn.) Rydb.		1-1.2		1.0
Potamogeton robbinsii Oakes					2.0	1.0
Potamogeton zosteriformis Fern.		1.2		1-2.0	2.0	1.0
Ranunculus aquatilus L.					<1-2.0
Tillaea aquatica L.		1.2
Zannichellia palustris L.				0.7

. The results of sampling, presented by bay and transect, follow.

Bay A - Public Launch Bay

At the shore, stems of last year’s growth of the terrestrial plants flannel mullein (Verbascum lanatum) and knapweed (Centaurea sp.) were inundated by approximately 0.6 m of water, indicating that the lake water level was higher at the time of sampling than when those plants were growing.

Transect A3

No living aquatic plants were found in either a long tow extending from 2 m to 9 m water depth or from individual throws at the 2 m and 3 m depths.

Transect A4

No living plant material was found in either a long tow extending from 2 m to 9 m depth or from discrete sampling at the 2 m through 4 m depths.

With the exception of small plants of the charophytes Nitella sp. and Chara sp. in <0.3 m water, and a single emergent plant of Polygonum sp., no living plants were found in Bay A. Even the concrete launch ramp was devoid of visible growths of algae throughout its submerged length. A small amount of brown, decaying Potamogeton and other plant detritus was found in the samples. Amphipods were present in the collected charophytes. Several small (<2.5 cm) crayfish were observed among the charophytes, dead terrestrial plant material and rocks in shallow (<0.3 m) water near the launch ramp.

Bay B - Reynolds Resort Bay

No aquatic plants were found except for the emergent macrophytes which were particularly abundant along the northwest shore of the bay. Samples from 1.0, 1.5, 2.0, 3.0 and 5.0 m on Transect B1 yielded only brown, decaying plant detritus.

Bay C

The emergent aquatic plants Scirpus acutus (hardstem bulrush), Eleocharis palustris (slender spikerush) and Glyceria sp., a grass, were present at the north end of Bay C and in samples from <1 m? to 2 m. At <1.0 m, dense growths of Elodea canadensis approached the water surface. The plants were about to bloom. One strand of Potamogeton foliosus was found. A second sample contained Myriophyllum sibiricum. The bottom sediments were mucky. Plant detritus was found in samples from 3 m and 4 m, but no living plants were found.

A band of emergent macrophytes about 7 m - 9 m long extended about 6-8 m from shore. In the first of 2 samples from 1 m taken just off the band of emergents only a handful of living macrophytes was retrieved. Elodea canadensis and Potamogeton richardsonii, together with a few sprigs of Potamogeton foliosus and a young grass rhizome were identified. The other sample from 1 m contained only a small amount of the charophytes Nitella sp. and Chara sp.

A sample from 1.2 m contained Potamogeton foliosus, Elodea canadensis and fragments of Potamogeton richardsonii, Potamogeton zosteriformis, Myriophyllum sibiricum, Tillaea aquatica, and the charophyte Nitella in fine organic sediments.

A sample from 1.6 m contained Potamogeton foliosus and Elodea canadensis in roughly equal amounts, a strand of Najas flexilis and a small amount of the charophyte Nitella sp.

A sample from 2 m contained only a small amount of Nitella sp., growing in organic sediments.

A collection from 1.5 m in the western part of the bay yielded a handful of Nitella sp.

Bay D

Emergent aquatic plants were present at the north end of the bay. A band of Potamogeton sp., about 10-14 m long and about 3.3 m wide (interrupted in one area), extended from the shore to a maximum depth of about 1 m.

Samples were taken from 1.2 m through 8 m depths in Bay D. The 1.2 m collection contained only the charophyte Nitella sp. Amphipods were present. Collections from 2 m and 3 m contained only fine detritus. The substrate was silty with fine organic matter. Samples from deeper waters contained only plant detritus.

Bay E

Emergent aquatic macrophytes were present along the inflowing stream and along the shore of the lake. Submerged aquatic macrophytes densely covered the lake bottom out to the 2+ m depth level. At the outer limits of plant colonization, the lake bottom was covered with fairly solid turf of Elodea canadensis with individual plants of Myriophyllum sibericum interspersed at approximately 1 to 2 m intervals. In slightly shallower water were dense beds of Myriophyllum sibiricum. The tips of the plants had reached the water surface and were in flower. Inshore there were large, dense beds of Potamogeton pectinatus, also in flower. Small colonies of Potamogeton praelongus were also visible.

A grab sample from 2±m contained one strand each of Potamogeton praelongus and Myriophyllum sibericum.

A collection (E2mE) from 2m from the eastern area of the bay yielded Elodea canadensis and Nitella sp. along with a sprig of Myriophyllum spicatum.

Collection E1mN from 1 m (about 7.2 m off the emergents) contained a moderate amount of macrophytes including Potamogeton pusillus (64%, Elodea cf. nuttallii (16%) and Myriophyllum sibiricum (23%) growing on organic silt.

Collection E2mW from 2 m contained a moderate amount of plant material including Chara? sp.(30%), Nitella sp.(30%), Potamogeton foliosus (20%), Myriophyllum sibericum (20%), and a sprig of Potamogeton zosteriformis (5%).

A large collection (E0.7m#2) from 0.7 m contained 50% Myriophyllum sibericum, 30% Elodea canadensis, 10% Potamogeton pusillus, 8% Potamogeton pectinatus and a few plants of Potamogeton foliosus and Zannichellia palustris on organic sediments.

A moderately large collection from 1 m (E1mE) contained 60% Potamogeton richardsonii and 15% Potamogeton foliosus, 15% Potamogeton pectinatus (about to flower), 5% Elodea canadensis, and a sprig or two each of Potamogeton gramineus, Potamogeton zosteriformis and Myriophyllum sibericum. Also present were Nitella sp., a plant of Sagittaria cf. teres, and an unidentified charophyte. The substrate was silty sand with fine organic matter.

Bay G

Emergent aquatic plants were at the shore, but no submerged plants were found along Transect G2 except for a charophyte fragment from 1 m.

Bay L

A Transect L sample from <1m contained a moderate amount of Ranunculus aquatilus in flower. A collection from 1.5 m contained a small amount of plant material including Ranunculus aquatilus (in early fruit) and the charophytes Chara sp. and Nitella sp.

A collection from ±2 m contained a small amount of plant material. Elodea canadensis comprised 90% and Myriophyllum spicatum and Potamogeton zosteriformis each made up 5%.

A collection from 2 m (L2-2) contained Potamogeton robbinsii, Potamogeton praelongus, Myriophyllum sibiricum, Elodea canadensis, and a small amount of the charophytes Chara and Nitella. Sediments were fine and organic. An additional collection from 2 m contained a moderate amount of Elodea canadensis, together with a couple strands each of Ceratophyllum demersum, Potamogeton robbinsii, Ranunculus aquatilus and Myriophyllum sibericum.

Bay N

A collection from 1 m contained a moderate amount of plant material including Myriophyllum sibericum, Elodea canadensis, Ceratophyllum demersum, Potamogeton robbinsii, Potamogeton zosteriformis and a sprig of Chara, all growing on organic sediments.

DISCUSSION

Nomenclature of Myriophyllum exalbescens and M. sibiricum

The scientific name of the commonly found native northern watermilfoil, Myriophyllum exalbescens Fern., is now known as Myriophyllum sibericum Kom. (Ceska and Ceska, 1986). Most literature refers to the plant as M. exalbescens, but the reader is advised that the two names refer to the same taxon.

Present Survey

On July 17-18, 1995, the aquatic macrophytes of Buffalo Lake were restricted to depths of approximately 2 m and shallower. Buffalo Lake has experienced a catastrophic decline in macrophytes, in abundance as well as in the extent of colonization of the littoral zone. Both were severely reduced as compared with the most recent macrophyte survey (Broch and Loescher, 1984).

Of the eight bays chosen for the 1995 study because each had had abundant aquatic vegetation, only three (C, E, and L) were significantly colonized. Bay E, in the easternmost end of the lake, contains the largest shallow area in the lake. In 1995 as well as in 1983 (Broch, Ahl and Loescher, 1983) and 1984, it also contained the greatest mass of aquatic plants.

In 1995, Bay E contained the greatest diversity (11 species) of submersed macrophytes. Bays C and L each had 7 taxa. Only charophytes and a single amphibious knotweed (Polygonum sp.) plant were found in Bay A (near the public launch). In Bay D, only Nitella sp. and Potamogeton sp. were found. Only 5 submersed macrophytes and Nitella sp. were found in Bay N, all at the 1 m depth. In bays B and G where charophytes, Elodea canadensis and Myriophyllum spicatum had been found in 1984, not a single macrophyte was found.

As surprising as the profound decline in macrophytic biomass is the apparent total absence of Eurasian watermilfoil (Myriophyllum spicatum). In place of M. spicatum, the native milfoil Myriophyllum sibericum Kom. (= M. exalbescens Fern.) was found. Otherwise, the taxa found in each of the surveys

have been fairly consistent.

Table 2 on the next page (p14) lists the vascular macrophytes reported in the surverys of 1983, 1984, and 1985. Myriophyllum spicatum, found in 1984 along all transects except that of Bay S, was not identified in any of the 1995 collections, nor was a single M. spicatum plant observed as we cruised the littoral zone of the lake. Except for the replacement of Myriophyllum spicatum by M. sibericum in 1995, the major taxa found in each of the surveys have been fairly consistent. Presence or absence of the rarer taxa in one or more years might be real or the result of chance sampling.

Plants identified in the 1995 collections but not found in 1984 are Najas flexilis, Potamogeton foliosus, Potamogeton pectinatus, Potamogeton richardsonii, Potamogeton zosteriformis, and Tillaea aquatica. All but Potamogeton zosteriformis, Najas flexilis and Tillaea aquatica were found in 1983. The potamogetons and Najas are all commonly found plants while the tiny T. aquatica is classified as a sensitive plant by the Washington Natural Heritage Program (1990). A plant is labeled sensitive when it is vulnerable or declining. Such a plant could become endangered or threatened in the state unless threats

TABLE 2. COMPARISON OF VASCULAR AQUATIC MACROPHYTES FOUND

IN 1983*, 1984**, AND 1995 SURVEYS OF BUFFALO LAKE

	1983	1984	1995
Ceratophyllum demersum	x	x	x
Eleocharis acicularis	x	x	x
Eleocharis palustris	x	x	x
Elodea canadensis	x	x	x
Elodea nuttallii	x	x	x
Glyceria sp.			x
Isoetes sp.	x
Juncus balticus		x
Limosella aquatica	x	x
Myriophyllum sibericum (=M. exalbescens)		x	x
Myriophyllum spicatum	x	x
Najas flexilis	x		x
Polygonum amphibium	x	x
Polygonum coccineum	x
Polygonum sp.			x
Potamogeton alpinus	x
Potamogeton foliosus	x		x
Potamogeton gramineus	x	x	x
Potamogeton pectinatus	x		x
Potamogeton praelongus	x	x	x
Potamogeton pusillus	x	x	x
Potamogeton richardsonii	x		x
Potamogeton robbinsii	x	x	x
Potamogeton zosteriformis			x
Potamogeton sp.			x
Ranunculus aquatilus	x	x	x
Tillaea aquatica			x
Zannichellia palustris		x	x
* from Broch, Ahl & Loescher (1983)
** from Broch & Loescher (1984)

to its existence are removed or management programs are established to ensure its existence.

Two shallow water macrophytes, Juncus balticus and Limosella aquatica, found in 1984 were not found in the 1995 survey. Each had occupied depths of <1 m in one or two sites. These might have been present in isolated very shallow sites that were not sampled.

Depth of Colonization

In 1995, aquatic macrophytes were restricted to depths of approximately two meters and shallower. In contrast, in 1984 aquatic plants colonized Buffalo Lake to a maximum depth of 9 m. In 1984, Elodea canadensis was the dominant macrophyte in approximately 40% of the littoral zone of Buffalo Lake. Myriophyllum spicatum was dominant in about 30% of the littoral zone. The remaining 30% was occupied by a variety of shallow zone macrophytes and patches of the deepwater potamogetons P. praelongus and P. robbinsii.

In 1984 Myriophyllum spicatum was found along all transects except the Bay S transect which contained only Elodea canadensis and charophytes. Myriophyllum spicatum colonized the 2-5 m depth zone and was the most abundant plant at depths from 3 m to slightly less than 5 m. Elodea canadensis was found at some depth in all of the 24 transects which were distributed among 17 embayments. E. canadensis dominated the 5-9 m depth zone.

Possible Causes for the Decline of Aquatic

Macrophytes in Buffalo Lake

A reasonable although tentative explanation for the decline of aquatic macrophytes in Buffalo Lake can be formulated from (1) data from previous macrophyte studies on Buffalo Lake, (2) observations during lake monitoring, (3) the extensive limnological database on the lake and (4) reports in the literature on causes of macrophyte declines in other lakes.

There appears to be a shift in the primary productivity dominance between the littoral macrophytes and limnetic phytoplankton of the lake. Low Secchi disk transparency readings of 3 m, 4.5 m, and 2.5 m recorded on April 20, 1993, September 9, 1993, and April 18, 1995, respectively with concurrent reduction in macrophyte production below 2.5 meters indicate light as a possible limiting factor. The shading produced by increased population density of algae would inhibit the growth of macrophytes. Since the macrophytes found in 1995 were almost completely restricted to the 0-2.5 m depth zone of the littoral where the shading effect of algae would be minimal, shading by high phytoplankton populations is strongly suggested.

The phytoplankton dominance effect on macrophyte abundance and distribution is not unusual in lakes on the eastern side of the Colville Reservation. Both Little Goose Lake and Owhi Lake have macrophyte productivity limited to depths of less than 3 meters as a result of phytoplankton shading. In these cases heavy blue green algal blooms are responsible for the shading affect.

The key question is what conditions have brought about this rather abrupt and significant change in the primary productivity dominance of Buffalo Lake?

Increases or changes in nutrient levels and/or ratios may favor phytoplankton over macrophyte productivity. Any slight competitive advantage resulting in increased production of phytoplankton would be further enhanced by an increase in shading. The shading would be most critical at depths greater than two to three meters.

Whether the changes in the increased shading by phytoplankton is primarily quantitative due to a simple increase in overall primary productivity or whether there has been a qualitative change in species composition of the phytoplankton resulting in greater shading affect is not known. An earlier study of Buffalo Lake phytoplankton could be used to assess possible changes in the structure of the phytoplankton community. The impact on zooplankton would be of great interest to fishery management of Buffalo Lake.

Buffalo Lake water quality monitoring data from the past 5 years show no readily apparent changes in nutrient availability though a more rigorous analysis is underway. The possibility of nutrient changes should not be discounted. There are other indications of nutrient changes in Buffalo lake. There is no knowledge of any great physical changes occurring in the lake recently.

There is evidence of increased productivity (eutrophication) within Buffalo Lake by the decline in oxygen levels within the hypolimnion of the lake as shown by monitoring data. Buffalo lake nutrient and oxygen-temperature profile data can be accessed through the following World Wide Web address: .

A comparison of the oxygen-temperature profiles toward the end of summer stratification from 1988 to 1995 shows a gradual but consistent increase in the thickness of the anoxic zone within the hypolimnion. The oxygen-temperature profiles can be accessed by the following hyperlink addresses:

1995

1994

1993

1992

1991

1990

1989

1988

The increase in the anoxic zone from < two meters (1990) to >7 (1993) meters takes place during the time of decrease in macrophyte production. The years 1993 to 1995 coincide with the loss of macrophyte production at depths less than three meters. The greatest spread in range can be seen by looking at the oxygen profiles 1989 (lowest) and 1993 (highest). To what extent the increased organic productivity resulting in reduction of oxygen within the hypolimnion is due to decay of macrophytes and/or to increased phytoplankton productivity is not known. However the latter hypothesis is a better fit of the data. Continued monitoring of nutrients and especially oxygen levels may give some idea of the factors responsible.

Other factors, such as poor growing conditions for macrophytes (e.g., cool water temperatures or adverse water level fluctuations) might have permitted phytoplankton and/or periphyton populations to become unusually dense. Continued monitoring of Buffalo Lake may provide alternate hypothesis.

A primary question is this a stable trend or a perturbation with a return to prior conditions? Continued monitoring is essential to determine whether this is a real change in the limnology of Buffalo Lake. Buffalo Lake may alternate between phytoplankton and macrophyte dominance. Only continue monitoring will provide answers to this important question.

Herbivory and non-consumptive clipping by crayfish have been reported to markedly reduce macrophyte biomass in lakes (Letson and Makarewicz, 1994; Lodge, 1991). The crayfish population in Buffalo Lake has increased in recent years as evidenced by the 40 lb of the crustaceans caught in the 1994 gill net survey (Gerry Marco, personal communication). Although crayfish activities might have contributed to the macrophyte decline, it is unlikely that they were the primary cause. Observations by SCUBA have shown that crayfish activity occurs in the 1-3 m zone (Lodge, 1991). Throughout Buffalo Lake numerous species of macrophytes have disappeared from depths greater than 2.5 m. It is unlikely that populations of crayfish are either dense enough or uniform enough to cause the demise of all plants below the 2+ m depth in a lake as large as Buffalo. Also, crayfish are known to prefer certain plants over others (Lodge, 1991).

Insect infestations (Creed and Sheldon, 1994; Kangasniemi, 1983; Painter and McCabe, 1988) and disease (Shearer, 1994) have been implicated in declines of Myriophyllum spicatum, usually after biomass of the weed had been at a high level for about 10 years. Although disease organisms and herbivory by insects might have been factors in the decline of Eurasian watermilfoil, they are unlikely to have affected other taxa because they tend to be host-specific.

It is likely that the loss of aquatic macrophytes from the 2.5 m and deeper area of littoral zone in Buffalo Lake is due to a combination of factors, the primary factor being a shift in the primary productivity dominance between the littoral macrophytes and limnetic phytoplankton of the lake. The shift has resulted in increased shading by phytoplankton and/or periphyton.

Implications of Aquatic Macrophyte Decline in Buffalo Lake

With the profound reduction in macrophytes in Buffalo Lake, the nutrients that had been contained in plant tissues will be released to the water as decay occurs. The increased levels of available nutrients are likely to stimulate either a bloom of phytoplankton and periphyton or increased growths of aquatic macrophytes. If the phytoplankton populations remain very dense throughout the growing season, they will inhibit the macrophytic recolonization of the Buffalo Lake littoral zone by shading. The impact of loss of macrophytes for food and cover for aquatic insects and fish fry is considerable.

Higher phytoplankton numbers may cause decreases in the dissolved oxygen concentration within the hypolimnion during summer stratification and during winter stratification as well. This hypothesis appears to be supported by the monitoring data discussed earlier. It is important to closely monitor changes in the anoxic zone during summer stratification. The oxygen-temperature profiles from past monitoring have been extremely informative as to possible changes in Buffalo lake.

The shift to phytoplankton dominance in Buffalo Lake has important implications to management of the lake as an important fishery. Qualitative and/or quantitative changes in phytoplankton composition could have enormous impact on the fishery by affecting zooplankton diversity and abundance. Zooplankton studies are being initiated to ascertain affect on plankton in Buffalo Lake.

APPENDIX

Summary of Aquatic Macrophyte Observations - 1983-1989

July, 1983

The aquatic macrophytes growing in eight bays (labelled A-G) of Buffalo Lake were sampled. Myriophyllum spicatum was the most abundant plant in the 2-4 m depth zone. The transition to dominance by Elodea canadensis occurred in the 3.5-4 m depth zone. Elodea canadensis or Elodea sp. was either the most abundant plant or the only species present at the 5-9 m depths.

July 10-13, 1984

Myriophyllum spicatum and Elodea canadensis formed two nearly continuous overlapping bands around Buffalo Lake. Myriophyllum spicatum formed the band at the 2-5 m depth. Elodea canadensis grew in deeper water, from 5-8 m and occasionally to 9 m. Myriophyllum spicatum was the dominant species in the 3-4 m zone and Elodea canadensis was dominant in the 6-9 m depths. The change in species dominance occurred in the 4-5 m zone. Myriophyllum spicatum was found along all transects except transect S, while Elodea canadensis was found along every transect. The other macrophytes found in Buffalo Lake had a patchy distribution.

In 1984, 6 emergent macrophytes were found, 13 submerged macrophytes, and several charophytes.

September 14, 1986

The water level in Buffalo Lake was down approximately 1.3-1.6 m from 1984. In all grab collections from depths greater than 3.5 m, Elodea canadensis was the dominant taxon. Myriophyllum spicatum was dominant in all collections from 2-3 m. Myriophyllum spicatum was present around the perimeter of the lake, forming a ring interrupted for short distances in some steep, rocky areas. In shallow zones flowering Myriophyllum spicatum formed an almost impenetrable mass from the lake bottom to the surface.

May 5-6, 1987

Stands of Myriophyllum spicatum were present. Vigorous growth was observed only basally and at the tips of overwintered plants.

May 10, 1988

In Bay B, Myriophyllum spicatum was observed with tips of plants showing new growth but older leaves in poor condition and covered with periphyton.

September 28, 1988

M. spicatum was blooming in 2-3.5 m water depths at Station L, at H; M. spicatum was present at D, C, and P.

Emergent macrophytes Eleocharis sp. and rushes were present at C, D, J, E, F, as usual. Potamogeton praelongus was present in Bay B.

September 11, 1989

M. spicatum was still abundant, though perhaps less abundant than before. Fewer plants reached the water surface than in September of 1988. Much of the Elodea canadensis was covered with algae. The elodea formed a solid understory. Also seen were patches of Potamogeton praelongus, P. robbinsii and a fine-leaved potamogeton, possibly P. pusillus.

In Bay B, M. spicatum looked similar to before, flowering abundantly. Elodea canadensis was still the understory plant, but it was not as visible as before. Potamogeton praetensis beds were dense but the plants appear to be well-grazed, possibly by snails. Leaves were yellowish, missing epidermis, some leaf margins, and there were holes in the leaves.

Literature Cited

Broch, E., J. Ahl, and J. Loescher. 1983. The distribution and abundance of aquatic macrophytes in Buffalo Lake, Okanogan County, Washington. Report to Colville Confederated Tribes. Aquatic Macrophyte Study. October 1983. Department of Zoology, Washington State University. 13 p.

Broch, E., and J. Loescher. 1984. The direction and extent of the Eurasian watermilfoil invasion of Buffalo Lake, Okanogan County, Washington. Report to Colville Confederated Tribes. Buffalo Lake Aquatic Macrophyte Study. December 1984. Department of Zoology, Washington State University. 26 p.

Broch, E., and J. Loescher. 1995. The Limnology of the Lakes of the

Colville Reservation. World Wide Web address:

URL (). The Database pertaining to Buffalo Lake can be viewed at .

Ceska, Oldriska, and Adolf Ceska. 1986. Myriophyllum (Haloragaceae) in British Columbia: Problems with identification. Pp. 39-50. In: Lars W. J. Anderson, ed. Proceedings of the First International Symposium on watermilfoil

(Myriophyllum spicatum) and related Haloragaceae species. Aquatic Plant Management Society. 223 p.

Creed, Jr., Robert, P., and S. P. Sheldon. 1994. The effect or two herbivorous insect larvae on Eurasian watermilfoil. J. Aquat. Plant Manage. 32: 21-26.

Harkness, R. E., D. A. Myers, and G. C. Bortleson. 1974. Water Resources of the Colville Indian Reservation, Washington. Open File Report. United States Department of the Interior Geological Survey. Tacoma, Washington.

Hitchcock, C. L., and A. Cronquist. 1973. Vascular Flora of the Pacific Northwest. University of Washington Press. Seattle. 730 p.

Kangasniemi, B. J. 1983. Observations on herbivorous insects that feed on Myriophyllum spicatum in British Columbia. pp. 214-218. In: Lake Restoration, Protection and Management. Proceedings of Management Society. U.S. Environment Protection Agency. Washington, D. C.

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