This lab focused on aquatic invertebrate sampling methods and identification. We sampled a section of the Chagrin river at Chagrin Reservations Metropark. The sample site was located at 41° 27' 28 N, 81° 24' 20 W. The section of stream was predominantly riffles, with run/ shallow pool habitat above and below. The weather was about 18°C and cloudy. 
We explored two sampling methods. These were kicknetting and Hester-Dendy Sampler deployment. Kicknetting is a sampling method where a one square meter seine net is held open perpendicular to the current and the stream bottom directly upstream is disturbed. This is usually done by a team of two to three people with team members either holding the net or kicking and shuffling the rocks in front of the net. Disturbing the bottom dislodges aquatic invertebrates from their habitat so that they can be sampled. The net is then removed from the stream and the invertebrates are collected and preserved in 70-90% ETOH.
The second method we used was called a Hester-Dendy sampler. This method of sampling is used to collect aquatic invertebrates over a period of time. The Hester-Deny sampler is a structure consisting of several small wooden plates, separated slightly so aquatic invertebrates can colonize in between the plates. The wooden plates are then tied to a one meter string which is attached to a brick. The brick acts as an anchor in the stream bed to prevent the sampler from floating away. We then will collect the samplers after a period of two weeks, which should be sufficient time for grazers to colonize.
We caught many organisms in the kicknet and were able to identify most to order in the field. The orders we collected were Order Ephemeroptera, Order Trichoptera, Order Odonota, Order Diptera, Order Hemiptera, Order Coleoptera. We also caught individuals from Phylum Annelida, and Class Gastropoda.
Order Ephemeroptera
Mayflies are aquatic insects in Order Ephemeroptera. They are distinguishable by the presence of wingpads on the thorax, conspicuous flat gills on the abdomen, and generally three long tails. Mayflies are predominantly grazers and shredders. The mayfly nymph pictured has lost one tail. 
Order Trichoptera
Caddisflies can be separated into two groups, case building and net-spinning. Case building caddisflies are predominantly grazers and shredders, while net-spinning are primarily collectors. We found only net-spinning caddisflies at our sample site. The picturebelow shows a larva, and the picture to the right shows pupating and newly-hatched adults.
Order Odonata
There are two different suborder of Order Odonata, the dragonflies (Anisoptera) and the damselflies (Zyoptera). Dragonflies do not have gills on their abdomen, where damselflies have three gills sticking out of thier lower abdomen that are elongated and flat. Dragonflies have heads narrower than their thorax and abdomen. Damselflies have the opposite with their thorax and abdomen narrower than their head. Both are predatory as larvae and adults. We only sampled damselfly larvae (left) in the field.
Order Diptera are the true flies. We sampled shredders and collectors at the field site. We caught crane fly larvae (shredder, right), black fly larvae (collector, above right), and watersnipe fly larvae (above, left). They do not have segmented legs on their thorax and no wing pads.
Order Hemiptera
Order Hemiptera are the true bugs. In this order, larvae and adults are predators. Their mouths form a beak-like structure that enabled them to suck bodily fluids out of their prey. We only sampled Family Gerridae. Photo to the right courtesy of www.myrmecos.net.
Order Coleoptera
Order Coleopter are the beetles with it being the most diverse order of insects. The larvae usually have a harden head and thorax. The adults have split protective shell on their backs called the elytra. From this order, we sampled water pennies (left).
We sampled some non-arthropod macro-invertebrates as well, these included Phylum Annelida, Class Hirudinea (leeches, left)and Class Gastropoda (pouch snails).
Overall, it was an educational and fun day at the Chagrin River.
No comments:
Post a Comment