Project keywords:Didymoshenia geminata Project purpose:The purpose of the Didymosphenia geminata removal experiment is to determine if the presence of the algae has an effect on the abundance and composition of invertebrates in the East River along the Gothic townsite. The overall goal is to determine what kind of influence and invasion of D. geminata has on the aquatic community. Project methodology:
We
removed the algae, Didymosphenia geminata,
from the stream bottom of 8 plots in the
East River,
in order to manipulate the environment and determine if the presence of D. geminata has an effect on the
abundance and composition of the invertebrate environment. The plots were
placed at two sites in the
East River. Plots
one through four resided 30 meters above Vera falls, and plots five through
eight were placed several hundred meters downstream. In order to prevent bias,
the plots were chosen when in mid June when the river’s water level was high,
(roughly 40 centimeters) and the stream bottom was difficult to see. The plots
at each site were placed two meters away from each other, beginning downstream
and moving upstream. Each plot measured 0.5 m x 0.5 m and had an adjacent
control where no D. geminata was
removed during the experiment. The control plots were placed 1 meter away from
the corresponding experimental plot where the velocity and depth of the water
were similar between the two plots. The upper corners of each plot were marked
two steel bars placed 0.5 meters away from each other. During removals the
plots were defined using a 0.5 m x 0.5 m grid which was placed over the steel
bars and submerged to outline removal area. We used glass viewing box to
identify where in the quadrat D. geminata
was present and metal forceps to eradicate the algae from the substrates of the
removal plots. To control for disturbance, we placed the quadrat over the
adjacent control (non D. geminata
removal) plot and touched each of the rocks within the designated area with the
same forceps without removing any D.
geminata. We visited the sites regularly (every 2 to 4 days) to remove any D. geminata growth in the experimental
plots. The removals took place from July 3rd to July 27th,
just over three weeks.We used a volume
index to determine the amount of D.
geminata growth in each of the plot over the three weeks. To do this, we
placed the 0.5 x 0.5 meter quadrat over the plot. The quadrat is divided into
25 10 x 10 cm squares. We visually determined the amount of D. geminata inside each individual
square at each plot along with the depth of the algae (mm) in the particular
square. The volume index was calculated by multiplying the percent cover by the
depth for each of o the 16 plots. The plots were first scored on July 3rd
(prior to removal) and continued to be scored every 7 to 10 days until July 27th.
On July 28th we sampled the center of each of the 16 plots for
benthic invertebrates using a 31 cm by 31 cm Hoffman sampler with 375
micrometer mesh and electrobug sampling methods (Taylor et al. 2001). We
separated the invertebrates by plot and taxa in the field and preserved the
samples in water. We used a dissecting microscope to identify and count the
invertebrate. Most of the taxa were classified to genus or species using Ward
et al. (2002) and Peckarsky et al. (1985), except for chironomid larvae which
we identified to family. The differences in abundance between plots were tested
using a Hotelling’s T2 test.Species
diversity metrics (e.g., richness, evenness, and dominance) will be rarefied
using EcoSim, pooling across all 16 plots and differences assessed using
generated 95% confidence intervals from EcoSim software (Gotelli and Enstminger
2004).
Project abstract: Data variables arrangement:columns Data variables description:Rows represent the information collected from each .5 x .5 meter plot on a specific day
Project Audit
Have these data been audited?No Who audited these data? Are the metadata and associated data file of sufficient quality to repeat the study?