A day in the life of an aquatic critter

Laurie Stover
Strawberry Hill Nature Preserve

(8/2013) Nets and buckets in hand, a group of children trek excitedly along the trail to the stream’s edge. I can barely keep them out of the water long enough to give the brief instructions: "Flip over rocks, use your net to find small creatures, look closely, don’t throw the rocks at each other, stay where I can see you. Okay, go have fun!"

The group is participating in our Aquatic Communities program at Strawberry Hill and it is a big hit with preschoolers through highschoolers. Even the adult chaperones don their water shoes and start flipping over rocks, just as excitedly as the children. We educate the children on how to search for the macroinvertebrates living in the stream. The term macroinvertebrates refers to animals lacking a backbone that are large enough to see without the aid of a microscope.

Most of the animals that the children find are in the Phylum Arthropoda family. This Phylum includes the insects, spiders, and crustaceans to name a few. Of course the children are interested in the "big guys." Crayfish are a treasured find. I congratulate them on their catch and then try to redirect them back to looking for the small animals that they may have otherwise overlooked. Slowly they begin to find some things: caddis fly casings, mayfly and stonefly nymphs, and crane fly larvae. Granted, the smaller creatures don’t warrant quite the response from the group as a large crayfish does but nonetheless, these smaller guys are just as interesting.

While the children enjoy getting wet and finding these animals, the bigger lesson to be learned is that we are actually getting a feel for the health of the stream (Swamp Creek in this case). Many of the animals thrive only in high quality freshwater streams. Take the caddisfly, for instance. Caddisflies, from the Order Trichoptera, are often used as the model for fly-tying when catching trout and other fish. The larval stage of the caddisfly is aquatic and known for its clever construction of a casing. The larvae, attached to a rock within its casing of pebbles, pine needles or dead leaves, will feed on small particles flowing through the water. They will undergo a pupal stage and the adult will hatch off the water (sometimes enmass). When I find a rock in the stream covered on one edge by 10-15 caddis fly casings, I am sure to point it out to the children who then venture forth to find more.

The search also begins to turn up another fun little macroinvertebrate, stoneflies. Stoneflies are from the order of insects called Plecoptera (Greek translation, "braided wings") and are some of the most primitive insects. Fossils of certain species date back to the Mesozoic period. The adult stonefly is very short lived and some do not even eat. Their sole purpose is to mate. The female lays hundreds of eggs which she carries on her back and then eventually deposits in the water. The eggs hatch in a few weeks and the nymphs begin their 1-4 year lifespan in the water, undergoing 20-30 molts.

Also if we are lucky we will find a few mayfly nymphs. Mayflies are grouped in the Order Ephemeroptera meaning "short-lived" or "lasting a day." The final adult stage of a mayfly may be commonly known to fly fisherman as a dun.

Scientists sometimes use what is called the EPT index as one way to rate the health of a stream. The EPT index is a count of the number of species from the Ephemeroptera, Plecoptera and Trichoptera families. Since species from these orders are sensitive to pollution and must have clean, well-oxygenated water to thrive, a high EPT index is a very good thing.

The purpose of the Aquatic Communities program at Strawberry Hill is tri-fold. Most importantly, we want the kids to have fun exploring and learning about streams, ponds, and the natural world around them. As Robert Louv describes in his book, "Last Child in the Woods: Saving Our Children From Nature-Deficit Disorder," children are growing up "denatured." The joy of getting your feet wet; getting muddy; or figuring out that a crayfish swims backward to escape danger are things that many children don’t have an opportunity to experience.

Secondly, we want them to begin to understand the concept of relationships within an ecosystem. During the introduction of the program we talk about the communities in which they live; their neighborhoods, schools, and how everyone interacts. Then we brainstorm about what makes up an aquatic community such as a pond or a stream. The children begin yelling out "Frogs!" "Fish!" "Turtles!" Oftentimes I yell back, "What do all those animals eat?" There is a bit of a pause but then I hear "Bugs!" "Plants!" Whether they realize it or not, they are starting to form an idea that even though the bugs and plants may not seem as fun, they are just as important (if not more) to the community as the frogs and fish. Lastly, we want the children to see that if an aquatic community is to stay healthy it will require the help of humans. We talk about pollution sources and how they can help to keep water clean.

Children benefit immensely by spending a few hours in the woods, on a hike, or wading in a stream. The excitement of discovery, the looks of awe when they catch something in their net; seeing a turtle climb out of the water to sun itself; or hearing the songbirds are priceless experiences and ones I never get tired of introducing to them.

Please visit www.StrawberryHill.org for a list of upcoming events for those of all ages in search of a nature adventure.

Laurie Stover lives in Orrtanna, PA and is a naturalist at Strawberry Hill Nature Preserve.