The effects of rivers and manmade impoundments on freshwater phytoplankton communities.

How does species diversity and density change with habitats and what role do humans play? Specifically, how does phytoplankton diversity and density change with microhabitats and the effects of manmade impoundments? The purpose of this study was to see whether the phytoplankton species for soft algae and diatoms were similar between two lakes (Maple Bay and Lake Kathleen) connected by a river (Maple River) and also to see if the presence of a manmade impoundment (dam) would lessen the decrease in density and diversity versus the natural lake opening. To do this, we collected water samples at four sites (site 1 = Maple Bay; site 2 = Upper Maple River; site 3 = Lake Kathleen; site 4 = Lower Maple River; see Figure 6) and did a plankton tow at each site. The water samples were used to count the absolute density per milliliter of water. We used Palmer-Maloney cells for the absolute density counts. From the plankton tow, we counted and calculated the relative density of soft algae (wet mounts with Lugol's solution) and diatoms (with a permanent mount). By completing a species index for all of the sites we could see that a proportion (0.786) of the soft algae species and a proportion of diatoms species were found in both Lake Kathleen and Maple Bay. We also did a Shannon-Wiener diversity index test, which showed a difference in soft algae and a difference in diatom diversity between Lake Kathleen (soft algae = 0.855; diatom = 0.7809) and Maple Bay (soft algae = 0.395; diatom = 0.9281), with Lake Kathleen having a higher diversity index for soft algae and Maple Bay having a higher diversity index for diatoms. This shows that the two lakes have similar species composition, but that some of the soft algae and diatoms did not flow from Maple Bay to Lake Kathleen going down the Maple River and that there was additional diversity of soft algae at Lake Kathleen. The increase of soft algae diversity at Lake Kathleen was thought to be due to the small swamp that feeds Lake Kathleen. As for the effects of manmade impoundments, our data did not support our hypothesis. There was not a lesser decrease of loss over the impoundment like we predicted. Our diversity indices and our t-tests showed a more significant difference between site 3 and 4 as opposed to the natural lake opening found at site 1 and 2. There was actually an increase in diversity and density going from site 1 to site 2. Overall, we found that Maple Bay and Lake Kathleen did have similar soft alge and diatom species composition, although some species were added or disappeared along the way, and that the manmade impoundment did not lessen the decrease in species diversity or absolute density compared to the natural lake opening (site 1 and 2).http://deepblue.lib.umich.edu/bitstream/2027.42/55064/1/3509.pdfDescription of 3509.pdf : Access restricted to on-site users at the U-M Biological Station