1 The Concord River is home to many animals that depend on aquatic environments and surrounding habitats for their survival. One way to understand this interrelationship is through a food web. Snapping turtles are common along the Concord River and play important roles in the local food web. Food webs show complex relationships between animals that eat plants (herbivores), animals that eat both plants and animals (omnivores), and animals that will eat other animals (carnivores).
2 This is a food web sample illustrating the complex interrelationships of plants and animals. Plants are consumed by herbivores and omnivores, which are typically found low or in middle parts of the food chain. Carnivores and some omnivores prey on other consumers and are generally ranked higher on the food chain. A food web can be broken down into simple food chains. We can determine a food chain by identifying producers, consumers, and decomposers. For example, a plant gets eaten by an insect, which will be eaten by a fish, which will then be eaten by an osprey. This is a producer, eaten by a primary consumer, eaten by a secondary consumer, eaten by a tertiary consumer. Plant (producer) > Insect (primary consumer) > Fish (secondary consumer) > Osprey (tertiary consumer)
3 Food chains, when in pyramid form often resemble general population counts of organisms. Plant kingdom species, for example, are collectively an enormous group and sit at the bottom of the food chain. Animals toward upper parts of the food chain, like osprey, have a small population in comparison to local plant populations. When plants and animals die, or when scat falls to the ground, the energy and nutrients that make up their bodies become recycled by the decomposers. The decomposers consist of Fungus, Bacteria, and Invertebrates. When something dies the FBI are always there to investigate and without them we would have no nutrient rich soil to support plant growth.
4 Plants Falling leaves collect in calmer areas of the river. As they decompose, they provide food and shelter for macroinvertebrates, fish, amphibians, and mammals. Macroinvertebrates Macroinvertebrates are tiny organisms that do not have backbones, such as worms or dragonflies. They live in water for all or at least part of their lives. Although they are tiny and we can spot them without a microscope, magnification certainly helps us to view them in greater detail. They are essential for a healthy river ecosystem and help to promote good water quality. Macro invertebrates thrive among the leaf litter in and along the Concord River. Macroinvertebrates in the Concord River include various species of insects, crustaceans, leaches, mollusks, aquatic worms, and planarians (or flatworms). These organisms can be collected using simple field equipment. They can be included in river studies, recorded as data to be analyzed as biological indicators of water quality. Different types of plankton and microorganisms also make up a key foundation of the food chain.
5 Scuds (amphipods) may be small invertebrates, but these crustaceans play a huge role in the Concord River food chain. Damselfly adults are common flying insects. As nymphs they live underwater.
6 Metamorphosis Invertebrates such as insects go through a special life cycle called metamorphosis. Insects are characterized as having three pairs of legs (6 legs only) and three body segments, the head, thorax, and abdomen. Many insects have wings. Other arthropods (similar critters) you may encounter along the Greenway are aquatic and terrestrial invertebrates, such as spiders, centipedes, millipedes, sow bugs, and worms. Some insects undergo what is called complete metamorphosis, while others undergo what is called incomplete metamorphosis. Eggs hatch into larvae or nymphs, which then undergo several changes and growth before becoming adults. Larvae and nymphs need to eat a lot, be it decaying plant matter (detritus) or other macro invertebrates, which helps them to grow and collect energy. Complete metamorphosis (ie. mosquito) - Egg > Larva > Pupa > Adult
7 Incomplete metamorphosis (ie. damselfly) - Egg > Nymph > Adult
8 Dragonflies live in the water (as nymphs) when they are young. As adults, they live in the air and on land. Excellent predators, dragonflies love to eat mosquitoes! Caddisfly larvae, one with a case it made out of debris in the water (top).
9 Caddisfly adult. Caddisflies are amazing little critters, which are an abundant food source for many animals. Some caddisflies have the ability to make their own cases that serve as their homes. Other species will seek shelter by clinging onto rocks and spinning webs to catch food flowing downstream.
10 Beginning in late winter, caddisfly adults can be seen along the Greenway resting on snow, tree branches, and near lights. Mollusks and Gastropods Seashells can also be found in rivers. These two shells are from a mollusk called a mussel (sometimes noted as a clam).
11 Aquatic and terrestrial gastropods and mollusks, including slugs, snails, mussels, limpets, and clams can be found in and along the Concord River. They mostly eat vegetation. Slugs (gastropods) and mollusks are invertebrates with soft, nonsegmented bodies. Mollusks have one or more shells covering their bodies. Mollusks are generally found along the river bottom or on rocks and are often eaten by diving ducks, raccoons, and mink. Some snails can live on land or in the water (amphibious). Slugs are often seen moving on rocks and plants.
12 This one-shelled mollusk is an aquatic snail. Fish are animals well-suited for life underwater. Gills allow them to breathe in a lowoxygen environment. Fins help them move through the water with speed and agility. Various adaptations enable fish to see and to smell and to feel vibrations, which is particularly useful for finding food and evading predators. Fish breathe by absorbing dissolved oxygen when water flows in their mouths, though their gills and out their gill covers.
13 Dragonfly nymph. Damselfly nymph.
14 Fish depend on macroinvertebrates, such as dragonfly and damselfly nymphs for food. Fish in the Concord River are abundant. They depend a great deal on macroinvertebrates, such as dragonfly and damselfly nymphs for food. Smallmouth bass. Local anglers enjoy catching fish in the Concord river, including smallmouth bass and common carp. Both are non-native. Carp are considered an invasive species, however, and can cause extensive damage to aquatic vegetation and other wildlife populations.
15 Common carp. Bioaccumulation in Fish According to biological indicators the Concord River s water quality of now good, unlike many years ago when factories, mills, and residents dumped waste products into the river without restraint. Some pollution still enters the waterway and its soils though. These contaminants accumulate and magnify as they reach upper levels of the food chain (bioaccumulation) and may cause health problems in wildlife and humans alike. Anadromous Fish Fish that are anadromous regularly migrate. Although people have long-relied on anadromous fish for food, they also have been making their migration more and more difficult, greatly reducing their numbers. Alewife, for example, used to travel from their winter homes in the Atlantic Ocean, up the Merrimack River, and into areas of the Concord River. Their goal was to get beyond Lowell, where they would spawn (reproduce) during early spring. The high walls of dams built across the rivers in order to power mills and generate electricity, blocked the fish, not only reducing the chances of spawning but also disrupting the food chain.
16 Alewife and other anadromous fish have a difficult time migrating upstream, due to dams that have been laid across rivers. The fish ladder at Wamesit Falls. Red arrows illustrate the path fish take through the ladder to make it over the dam. Mammals The trees that line the Concord River support a wide range of wildlife, including many mammals. These animals are known for producing milk for their young, have sweat gland, and have fur or hair. Many mammals prefer to live in an ecotone, or edge between two ecosystems, a space particularly rich with food and shelter. Raccoons, for example, hunt and gather in forested areas, where they find rodents, insects, and plants to eat. They also hunt and gather food from along the river, including insects, mollusks, and frogs.
17 Raccoons have many different kinds of teeth, which allow for capturing and eating different types of prey as well as crushing and grinding a variety of plants. We call this omnivorous dentition. (Raccoons are omnivores.) The teeth of muskrats are suited for snipping off and grinding plants. We call this herbaceous dentition. (Muskrats are herbivores.)
18 River otters are well-adapted for hunting at night, in the water, and on land, where they feed on fish, turtles, and frogs. They are seldom observed, although their tracks and slides are sometimes visible, especially in winter. Concord River Watershed A watershed is made up of all the water that runs off the land, be it from your kitchen sink, streets, streams, or sewage pipes. The Concord River itself is not a very long river, though the watershed that contributes flow to the Concord River covers many square miles. Two smaller rivers, the Sudbury River and the Assabet River join at their confluence in Concord, Massachusetts and form the Concord River. From there, the Concord River flows from south to north, eventually flowing into the Merrimack River in Lowell. Upstream of Lowell the Concord River is lined by forests, meadows, farms, and suburban towns providing a calm, tranquil flow and a muddy bottom. Shortly after entering Lowell, the landscape changes dramatically, as it becomes surrounded by urban neighborhoods and the river begins a rapid decent over a series of falls before meeting its confluence with the Merrimack.
19 This is the Concord River watershed. The Concord River itself begins near the center of the image and flows north ending near the top-right corner. Dragonfly adult. This change in landscape and terrain has an effect on habitats, as the water flows faster and the river bottom becomes rocky in many places. Fast water flow in particular, impacts locations where wildlife can be found. Dragonfly nymphs are more likely to comfortably survive in calm pool areas between falls.