Hester-Dendy Sampler Collection at the Chagrin River and Dipnetting for Macroinvertebrates at a Lentic Pond in the West Woods (3 October 2013)
Our Chagrin River field site
Today we returned to the Chagrin River, which runs through the South Chagrin Reservation of the Cleveland Metroparks, to check on our Hester-Dendy (H-D) samplers from 19 September 2013. It was noted that in the two weeks since we had been to the site to place our H-D samplers, the leaves from riparian vegetation had begun to fall into the river, producing a significant coarse particulate matter (CPOM) input. It was a cloudy, but pleasant day for rounding up macroinvertebrates, with a temperature of 25°C.
Using the flags on the trees as a guide, we search the stream for the flagged bricks anchoring our Hester-Dendy samplers. Good eye, Cameron!
Hester-Dendy samplers consist of wooden block substrates separated by spacers along an eyebolt, which are held in place by a nut. Although researchers utilizing H-D samplers leave them in the environment for longer periods of time (about eight weeks) to allow for a more complete representation of species present in the system, after a brief inspection of our samplers, it was determined that for our class’s purpose, two weeks was adequate for a “decent” colonization of species. Typically, grazers and shredders are the first to colonize the wooden board pieces, with predators moving in afterward. We predicted that a few species of trichopterans would likely be found on the samplers.
Ziploc bags are used to enclose the H-D samplers immediately after they are removed from the water to ensure that specimens do not get the opportunity to escape.
We were able to recover the H-D samplers by finding the orange flags attached to trees along the side of the river and searching the water perpendicular to their location. The samplers were attached to bricks so that they would not be carried away by the current. We were relieved to find that our Boy Scout-approved knots held up and that all of our H-D samplers were recovered.
When a flagged brick with samplers attached was found, the brick was removed from the water first and carried toward the location of the samplers. It was important to have a Ziploc bag ready before taking the samplers out of the water because organisms tend to drop-off once the samplers are removed. Each sampler was placed in its own Ziploc bag and then all the samplers and the attached brick were placed in a garbage bag.
These biologists are not afraid to get their hands dirty rustling rocks to release macroinvertebrates into the seine net.
After we recovered all the samplers, we used a method called kicknetting to sample the riffle zones for more macroinvertebrate species. This method of sampling involves placing a one meter square seine net along the bottom of the river in a riffle zone and disturbing the area immediately upstream by flipping over and rubbing rocks to release attached macroinvertebrates. These macroinvertebrates then flow with the current and get trapped in the seine net. Making sure that the bottom of the net is flush with the sediment and that the net is quickly scooped to the surface after collection is complete are important measures to prevent the loss of specimens. We searched the seine net, gently removed macroinvertebrates with forceps and then placed them in vials containing 70% ethanol.
Our West Woods field site
The next site that we visited was a lentic pond in the West Woods, which is part of the Geauga Park District in Novelty, OH. We expected to find predacious hemipterans and odonates in this non-moving body of water.
A triangle dipnet can be used to collect macroinvertebrates from the substrate and littoral macrophytes
The method we used to collect specimens is called dipnetting, which is ideal for pond sampling, but may also be used in streams. The optimal type of net to use for dipnetting is called a D net, which is shaped like a capital letter D. The flat side of the “D” is used to bump along bottom of the pond to disturb the sediment and vegetation at the benthos to collect macroinvertebrates. Since JCU does not own D nets, we used triangle nets for our collection.
In the photo on the left, biologist Ben is having the time of his life dipnetting for macroinvertebrates! In the photo on the right, Cameron carefully sifts through sediment and vegetation looking for macroinvertebrates in his dipnet haul.
After bumping the net along the bottom to stir up the sediment, it is
quickly scooped to the surface so that specimens do not have a chance to
escape. In addition to the expected odonates and hemipterans, we caught tadpoles in our nets.
Back in the laboratory, the proper method of organism collection from the H-D samplers was demonstrated. First, for convenience, the rope connecting the samplers to the brick was cut. The nut holding the wood blocks to the eyebolt was then removed. Next, the wood block substrates were each systematically searched on both sides for macroinvertebrates, which were removed gently with forceps and placed in a 70% ethanol solution. Alcohol was used to rinse sediment from the substrates to ensure that no specimens were overlooked.
Note the caddisfly cases attached to the wooden block. These cases are made from detritus and allow the caddisflies to withstand the fast-moving current of the riffle zone.
It was observed that several wooden blocks had the cases, or retreats, of caddisfly larvae attached to them. The leaves that were found attached to the H-D samplers were also searched for organisms.
Using a dichotomous key to identify a specimen of family Simuliidae
The specimens were then examined under the dissecting microscopes. Finer taxonomic distinctions of organisms from familiar invertebrate orders were accomplished by the use of dichotomous keys from the Guide to Aquatic Invertebrates of the Upper Midwest. Dichotomous keys use specific morphological characteristics presented in a certain sequential order to distinguish taxonomic rankings.
The flathead mayfly of family Heptageniidae
Ephemeropterans (mayflies), trichopterans (caddisflies) and pelcopterans (stoneflies), which are classified as "pollution sensitive" taxa are used as bioindicators of water quality in a measure called an EPT Index. The EPT Index quantifies the health of a stream by the number of species of these orders present, with healthier streams containing a larger abundance of these orders. The ephemeropteran families collected included Baetidae, the small minnow mayflies, and Heptageniidae, the flathead mayflies. Baetidae are strong swimmers and can have antennae longer than twice the width of their head. Members of Heptageniidae, like their common name implies, have flattened heads, bodies, and legs.
Note the hardened exoskeleton on the head (characteristic of trichopterans) of this member of Philopotamida
A few trichopteran families were also collected, including Hydropsychidae and Philopotamida. Species belonging to Hydropsychidae, the common net-spinner caddisflies, can be distinguished by a conspicuous brush of hairs on the posterior of the abdomen. A defining characteristic of philopotamidans, the finger-net caddisflies, is a T-shaped labrum, which is a structure located between the mouthparts. Philopotamidans are filter feeders that spin nets to trap edible particles from the water and then use the labrum to scrape the food from the net. No plecopteran species were found on the H-D samplers.
Representing Diptera (true flies) was a specimen from family Simuliidae, the black flies. Black flies have a ring of hooks on the posterior of the abdomen that allows them to attach to substrate and withstand the water current. A larval coleopteran (beetles) from family Elmidae, the riffle beetles, was also collected. As their common name suggests, riffle beetles are found in fast-moving and highly oxygenated areas of streams.
Check out this radical anisopteran that we collected from the West Woods!
Finally, a nymph odonate belonging to suborder Anisoptera was collected from the West Woods. As we learned from lecture, anisopertans (dragonflies) are distinguished from damselflies (zygoptera) because in the larval stage their head is the same width or narrower than their thorax and abdomen, they do not have three elongate gills extending from the posterior of their abdomen and in adults, their wings are spread out when resting.
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