Aquatic ecosystems like lakes and rivers are home to countless species of aquatic bugs known as benthic macroinvertebrates. These 'bugs' are not seen as commonly as fish as they are much smaller in size and are often burrowed in the mud or under rocks. Benthic macroinvertebrates are aquatic bugs that are big enough (macro) to be seen with the naked eye. They lack backbones (invertebrate) and live at least part of their lives in or on the bottom (benthos) of a body of water.
What are Benthic Invertebrates?
Benthic invertebrates may sound like a complicated term to understand but that’s not quite so. Benthic refers to the bottom of aquatic systems such as lakes and streams and invertebrates are animals that lack a spine and instead have an exoskeleton made from calcium. Quite simply put, these are bugs in the mud. With that in mind, you probably already know of a few bugs that live in the mud around the lakes all across The Land Between (TLB) such as dragonflies (Anisoptera), mayflies (Ephemeroptera), or crane flies (Tipulidae). Under the water, the larvae of all the different groups of invertebrates have different roles in the ecosystem that are integral to the function of our lakes and rivers. Shredders break down dead plant material that hold nutrients that are inaccessible to plants and other organisms. Collectors and gatherers eat algae to prevent large blooms and keep our waters clean for swimming and use in our homes and cottages. There are even predatory invertebrates that help to keep the populations of other invertebrates in check. Some are even big enough to eat small fish. On top of this invertebrates have more roles in our ecosystem that make them even more important.
A Fishy Food Source
Within aquatic food webs invertebrates occupy the very important middle tiers of the food web. Small species and young sport fish are reliant on these invertebrates. One example of this importance is with phantom midges (Chaoboridae). Young Lake trout (Salvelinus namaycush) grow to be big fish eating trout by feasting on these invertebrates during their nightly migration upwards through the water column. Another commonly found invertebrate throughout TLB is the crayfish (Cambaridae). They’re vital to the Smallmouth bass because crayfish make up on average 90% of the diet of the adult fish.
Important Energy Transfer
Most aquatic invertebrates do not spend their whole life in the water. Most invertebrate groups will crawl or break through the surface tension of the water to break out of their exoskeletons and emerge as adults. These adults will live out of the water either inland or around aquatic systems. While these invertebrates fly around to feed or mate, they become important food sources for many different species of birds and bats. Aquatic systems are very productive systems that produce lots of energy which is inaccessible to most animals on land. One of the ways that energy moves from aquatic systems to terrestrial systems is through the emergence of benthic invertebrates being eaten by birds. These invertebrate emergences are so important to many migratory birds, they are one of the main reasons to migrate from warmer, tropical locations each year (3).
The Canary in the Coal Mine
One of the most interesting aspects of benthic invertebrate biology is the range of tolerances to impacts from group to group. Impacts can be a number of different types including pollution, reduced natural habitat, increased wave activity from boats, and reduced visibility from suspended sediments in the water. This means that some groups cannot survive in areas with pollution and other disturbances while others can handle a much greater amount. Due to this, water quality can be assessed by observing which groups are present in the bottom of lakes, rivers, and streams. This can be done in a number of ways when assessing water quality. This can be done by assessing biodiversity or by accounting for the tolerance of the invertebrates in a sample (1). Benthic invertebrates, simply by living in a lake or stream can give us an idea of the health of the system.
Why Benthic Invertebrates are Important
Benthic invertebrates are important food sources for many aquatic creatures, not just fish but they are also an important food for ducks and geese. Due to their change in habitat after becoming adults, the adults become a major food source for many different kinds of birds that call the areas around our lakes home. As ecological indicators, benthic invertebrates can start to show emerging impacts to a system which can help us reverse the issues before other aspects of the ecosystem or even human health are impacted.
What you can do
There are a number of things you can do to keep the numbers of these important links in the food chain healthy. One simple method is by keeping all potential pollutants away from the edge of lakes as much as possible. For example, refuel all boats with removable gas tanks well away from the shore on land. Another way is by reducing impact to the shore habitats of lakes by allowing shore habitat to grow naturally for at least 3m back from the shoreline (2). Their habitat in the lake can be protected by reducing the near shore area used for swimming and boating. Another way to benefit the invertebrates in your area is by adding fire pit ashes to the lake water to boost calcium levels in lakes with low levels.
- Applied Aquatic Ecosystem Concepts. Mackie. 2004
- Wetland and Stream Buffer Size Requirements—A Review. Castelle et al. 1994
- Neotropical Migrant Songbirds. https://www.brooksbirdclub.org/neotropical-migrants.html
Bugs in the Mud is an activity to help you in the collection and identification of benthic macroinvertebrates in your very own lake!
Benthic invertebrates are indicators of lake health, meaning that the presence or absence of certain benthic macroinvertebrate species gives us a general idea of the quality of water. Some benthic macroinvertebrate species are tolerant of pollution, meaning they will survive in lower water quality, while other species need clean and healthy water to survive. When we find species that can only survive in clean water, we can infer that the water they were collected from is good quality. On the other hand, if the only species that are collected are very tolerant of pollution, we can infer that the water is not very clean. Benthics are an interactive, accessible and fun way for kids and community members to monitor lake health. Through Bugs in the Mud, you'll learn about benthic invertebrate identification and what certain species mean about lake health. Let’s get started!
Learn about the cool bugs (benthic invertebrates) that live in the lake and support fisheries and wildlife. The types of bugs that are in your mud can tell you how healthy the lake is and how clean the water is too! Come out for a morning/afternoon of play with the Blue Lake's staff to learn about these fascinating creatures. Nets and magnifying devices are provided. Be prepared to get wet.
workshop is about 3 hours and is best experienced either from
9 am to noon, but times are flexible.
drink and a snack in re-usable containers and sun screen is
donation to the charity is appreciated to support this event.
participant level: 10