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Distribution and Biomass of Macrophytes and Metaphyton Associated with Streams • Project Goals: • Characterize changes in macrophyte biomass and bed standing crops associated with control and experimental watersheds. • Determine the relationship between nutrient loading, biomass and standing crop. • Monitor changes in percent cover of metaphyton Summer 2002 Participants Isidro Bosch Elizabeth Mis Tom Balzer Eric Caruana Dept. of Biology SUNY Geneseo
The perimeter of Conesus Lake is covered by a narrow but dense band of vegetation consisting primarily of aquatic vascular plants. In some shallow areas, the plants form expansive beds that cover most of the bottom and form thick mats at the water’s surface. Qualitative transects taken from the shoreline to the outer edge (4 m) of these beds revealed that the dominant species in this zone is the invasive “weed” known as Eurasian milfoil (Myriophyllum spicatum) . This milfoil is especially dominant at depths of 1-3 m Sago Pondweed Wild Celery Water Stargrass Depth (m) Coontail Eurasian Milfoil Curly-Leaf Pondweed Wild Celery Common Waterweed Curly-leaf Pondweed Eel-Grass Sago Pondweed Eurasian Milfoil Distance From Shore (m)
Sand Point 1968 Sand Point 1968 Vallisneria Ceratophyllum Vallisneria Heteranthera 17% 20% Myriophyllum Elodea Elodea 13% Ceratophyllum 36% 15% Heteranthera Myriophyllum S and Point 2000 Sago Pondweed Myriophyllum Coontail 1% Sago Pondweed 32% Myriophyllum Coontail 67% From H. Forest Sand Point 2000 These pie charts provide a comparison of species diversity in 1968 and 2000 at the very same site. In ‘00 the bed is dominated by milfoil. In ‘68 a variety of different species are well represented.
During each of the last three years we have mapped the position of milfoil beds (I.e. > 75% milfoil) in Conesus Lake (beds are shown in green for the central part of the lake) using GPS technology. The surface area measurements we obtain by GPS are multiplied by biomass quadrat measures to estimate the standing crops of milfoil at each site. Six of the beds we monitor, including ones at Sand Point and Long Point on this map, are part of our USDA watershed manipulation study Eagle Point Old Orchard Point SandPoint Long Point McPherson Point
Summary data for six Eurasian watermilfoil beds in Conesus Lake . Cottonwood Gully, Sand Point gully and Graywood arethree of the experimental sites. The other sites serve as controls (no BMPs).
In 2002 we went back to the very same sites we sampled in 2001. There was no consistent relationship between the ‘01 and ‘02 biomass. The red line describes the points at which ‘01 and ‘02 values would be equal. This graph shows that in 26 of 32 sites, macrophyte biomass was lower for ‘02. Each point is an average of 3 quadrats taken at depths of 2 and 3 m. The points represent a total of six beds
We used stream loading data collected by Joe Makarewicz and co-workers to explore the relationship between loading of phosphorus and plant biomass. In 2002, total P was an excellent predictor of standing crop in milfoil beds
The Loading of soluble reactive phosphorus by streams was an even better predictor of the standing crop of milfoil beds in areas near the mouths of streams.
Over the next few years of our project, we will continue monitoring changes in milfoil biomass and standing crop near the mouths of our experimental and control streams to determine the efficacy of farm management practices in reducing macrophyte growth
Another way to consider these trends is to examine changes in the relative rank of the beds with respect to loading, biomass and standing crop. We see some interesting trends in the data, but there are shifts in rank from one year to the next that are not clearly related to loading.
Excessive growth of metaphyton (filamentous algae) on or around milfoil beds is another serious problem near streams in Conesus Lake. Area near stream dominated by the metaphyton species Zygnema and Spirogyra which grow on Eurasian milfoil In the summer 2002 we started to monitor metaphyton biomass (as % cover) near streams using a quadrat sampler
The biomass of metaphyton (as indicated by % cover at the water’s surface) is extremely high in some of our experimental sites (see for example Graywood Gully).
The sites fall into three statistically distinct groups in terms of percent cover. There is a good correspondence between cover and phosphorus loading by nearby streams.
Conclusions: The summer 2001 and 2002 data represent the baseline we will use to examine the future effectiveness of agricultural best management practices in reducing the excessive growth of plants near the mouths of streams in Conesus Lake. We predict that changes in metaphyton biomass will be evident within months after the reduction of nutrient loading through BMPs is achieved. Eurasian watermilfoil beds may take longer to respond, but the observed close relationship between phosphorus loading and standing crop provides some hope that macrophyte growth can also be managed.