Algae phyla - collection and microscopy (Lab 1)

Dr. Johansen demonstrating how to collect
phytoplankton

Fig. 1 - a plankton tow net

During this lab, Horseshoe Lake, Lower Lake and Doan Brook were visited in order to collect samples of algae. Horseshoe Lake is located in Cleveland near the intersection of South Park Boulevard and Park Drive. Lower Lake is also located at Shaker Lakes along with Horseshoe Lake. Doan Brook is located on South Park Boulevard as well. 

The method of obtaining the algae is called plankton tow. With this method, the algae is obtained by throwing whats called a plankton net (figure 1), into the water. The net that is used is very fine and allows the net to catch the microorganisms, but lets the water pass through easily. In order to successfully execute this procedure, the net must first be thrown into the water. Once the net is in the water, it should be kept there for a few minutes so the water and microorganisms can go into the net. Moving the net around in the water is also a good idea in order to ensure that different types of organisms are brought into the net. After leaving the net in the water for a few minutes, the net should be pulled out and held in a vertical position to allow all the water to drain through the net. The samples will be present in the collection vessel that is located at the bottom of the net. In addition to using the plankton tow, we were able to grab larger samples of algae off the walls and from the surface of the water. At Horseshoe Lake there were floating mats on the water which we were able to grab. Once we were able to look at the sample closely, it was determined that it was Hydrodictyon. When we went to Lower Lake we found some more Hydrodictyon and then we were able to scrape off some samples of periphyton from the walls. At Doan Brook, we used the plankton tow, and also tried to get some algae off of the rocks, but we didn’t have much success because there wasn’t a lot of algae to collect due to the pessimal environment. 

Collecting phytoplankton from
Horseshoe Lake

Upon returning to the lab, we prepared wet mounts from all samples. In total, we recorded 17 genera: 4 genera of phylum Bacillariophyta, 2 genera of Chlorphytes, 2 Charophytes, 3 Cyanobacteria genera, 2 Syrophytes, and 3 genera of Euglenophyta. Out of the three sites sampled, Horseshoe Lake had the highest diversity; we recorded 10 genera from 5 phyla. 

Fig. 2 - Synura, Euglena, and Lepocinclis

Fig. 3 - Pediastrum

Plankton tow samples from Horseshoe Lake were dominated by Mallomonas and Synura (Synurophyta) as well as eutrophication indicators Euglena and Lepocinclis (Euglenophyta, figure 2) and some Chlorophytes including Pediastrum (figure 3).

Fig. 4 - Melosira, Chroococcusand Gloeothece

Fig. 5 - Gomphonema, Chroococcus and Gloeothece

We recorded 3 genera of diatoms from wet wall samples at Horseshoe Lake; Melosira (figure 4) formed long, brown chains. Rhopalodia and Gomphonema species were also abundant in these samples (figure 5). Two dominant genera of cyanobacteria were recorded as well: Chroococcus and Gloeothece (figures 4 and 5), which look very similar, however Chroococcus differs from Gloeothece by cell division in 3 planes instead of 2.

Fig. 6a - Hydrodictyon

Horseshoe Lake was covered in thick mats along the littoral zone, which consisted of mostly the “water net” Hydrodictyon (figure 6a, 6b). This alga was identified in the field when stretched apart.

Fig 6b - Hydrodictyon

Fig. 7 - Spirogyra

Lower Lake was dominated by green algae (Chlorophyta and Charophyta), with three genera recorded. Spirogyra (figure 7) was quickly identified due to its spiral-shaped chloroplasts and formed large mats in the lake. Oedogonium and Scenedesmus (Charophyta, Chlorophyta, respectively) were also found in these samples. Doan Brook appeared to be quite disturbed; few rocks in the stream had mucilaginous diatom colonies but were covered in Platyhelminthes, indicating a degraded water body. The algae collected from this site confirmed this; Pleurosira (Bacillariophyta) were abundant and formed chains connecting at alternating polar nodules (figure 8); Pleurosira is an indicator of elevated conductivity.

 

Fig. 8 - Pleurosira

Dolichospermum (Cyanobacteria, figure 10) was also present. This planktonic alga is potentially toxin producing and capable of living in poorer water quality due to its ability to fix nitrogen via its heterocytes. Ankistrodesmus, another green alga, was found in some of these samples. Trachelomonas (Euglenophyta) was also present. This alga is easily identified because of its hard, loricate shell.

Fig. 9 - Dolichospermum

Because the lab period was shortened, we looked at the same samples on Tuesday, September 17^th, however most of the algae had died and were difficult to identify. No other genera were recorded during this time. This lab was a great introduction to using algae as indicators of water quality; we were able to determine that our sites were somewhat subject to disturbance and eutrophication by identifying important algal bioindicators.