Brown and green are the colors of the estuary. It is here that the river meets the sea in shallow, protected bays. The estuary serves a banquet of decaying plants, tiny floating plants and animals called plankton, and little fishes. Millions of sea animals get their start in life feeding in the quiet waters of the estuary. They can find shelter in salt marshes, beds of slender eelgrass, or wide mudflats.
An estuary has very little wave action, so it provides a calm refuge from the open sea. Some of the animals, such as flounder, eels, and striped bass are just visitors to the estuary. Small fishes such as stickleback and mummichogs, mud snails, and oysters may spend their entire lives there.
One of the strangest residents of the estuary has four eyes, a spear for a tail, blue blood, and ancestors who walked the earth before the dinosaurs. It is the horseshoe crab! It is called a "living fossil" because it has stayed basically the same for 200 million years. Its nearest relatives are spiders and scorpions. The horseshoe crab bulldozes through the mudflats turning up worms and clams with the front of its shell. It uses its tail as a rudder when it swims, upside down, or to right itself when it gets stranded on its back on the beach. Indians used its tail, or telson, for a spear tip, but the horseshoe crab doesn't consider it a weapon.
The Indians called the estuary "Between-Land", not quite land and not quite water. Each summer, Maine's Native Americans gathered in large groups to camp along its shores. They fished and dug for clams and grew corn on the hillsides overlooking the bay. They had big feasts of oysters, clams, and lobster. The heaps of shells they left behind are called "kitchen middens".
In Colonial times, the settlers used the salt marsh hay to feed their cattle and the tough cord grass to weave seats for their chairs. Many generations of Mainers, especially in downeast Maine, have made a living digging and selling clams and worms from the mudflats. Estuaries are also important for aquaculture, an industry that is just twenty years old in Maine. "Sea farming", as it's also called, raises commercially important species such as mussels, oysters, and salmon in protected bays until they are ready for market.
Collect a gallon of water from as many of these habitats as possible: pond, bog, salt marsh or estuary, and ocean. Use a gallon of distilled water (or tap water) as a control. Allow each water sample to evaporate in individual shallow pans set in a sunny place. Keep a record of how long it takes each to evaporate. What is left behind? What colors are the samples? Weigh them. Taste them. How do the sample differ?