As mentioned previously, animals play a complex role in the estuary. Animals can act to increase the height of intertidal zones by their support of grasses and other plants. Estuaries also act as nurseries for many commercially important sports fish (e.g., winter flounder or sea bass).
All living organisms (plants and animals) within the estuary must eat some type of food for survival. Plants make their own food through photosynthesis. Using the energy from the sun, water, carbon dioxide and nutrients from the atmosphere, they chemically create their own food. Since they make or produce their own food they are called producers. Organisms that do not create their own food must either eat plants or other animals. They are called consumers. Some animals get their energy from eating plants while other animals get their plant energy indirectly by eating other animals that have already eaten plants. Animals that eat only plants are called herbivores. Animals that eat both plants and other animals are called omnivores. Animals that eat only other animals are called carnivores. Some animals eat only dead or decaying materials and these organisms are called detrital consumers (derived from the word detritus which means decaying organic material).
Food chains show the relationships between producers, consumers and detrital consumers. For example, small fish can fulfill its energy needs by eating plankton whereas large fish fulfill its energy needs by eating small fish. Finally, bacteria eats the fish after it dies, getting its energy from all fish. The bacteria also returns nutrients back to the environment for use by the phytoplankton.
Thus a marine food chain becomes a complete circle. Animals may eat more than one type of food. They may eat many different types of plants or many different animals. This makes everything more complicated and the food chain becomes a food web. In the marine food web, special producers are found. They are tiny microscopic plants called phytoplankton.
Phytoplankton convert sunlight into chemical energy in a similar manner as terrestrial plants. Since the water is the home for these special tiny plants, it is also the home for tiny microscopic animals called zooplankton. Zooplankton consume phytoplankton. Sometimes zooplankton and phytoplankton are collectively referred to as one group called plankton. There are a number of small fish that eat phytoplankton, as well as a number of small invertebrates, e.g., ribbed clam and oysters. As one move up the food web, larger fish predate on smaller fish. Some animals play more than one role. The fiddler crab, for example, is a consumer as well as detrital consumer. The crab will eat dead things or living things if it can catch them. Also a secondary consumer may eat any number of primary consumers or producers. Animals like shrimp and crabs break the material down to detritus. Then bacteria reduce the detritus to nutrients. Detrital consumers work at every level, setting free nutrients that form an essential part of the total food web.
The food web is a pyramid, with enormous numbers of animals or plants at the bottom and many fewer animals at the top. For example, one liter of water has more phytoplankton than a cubic mile of the ocean has a large sports fish like sea bass.
In a food chain, energy is lost in each step of the chain, in two forms. First by the organism producing heat, the animal doing work, and second, by the food that is not completely digested or absorbed. Therefore, the food web depends on a constant supply of energy from producers and nutrients that are recycled by the decomposition of organisms. As food is passed along the food chain, only about 10% of the energy is transferred to the next level. For example, 10% of the energy phytoplankton received from the sun can be used by zooplankton at the next level. From one level to the next about 90% of the energy used by the previous level is lost. This means that there has to be a lot more organisms at the lower level than at the upper levels.
- Sponges are simple, non-motile animals made of a limited number of cells with no clear distinction into tissues or organs. The framework of a typical sponge is backbone of silicone- or calcium-based spicules and/or the protein collagen. Since the nature of the substrate and strength of water currents influence the shape of sponges, identification is based on spicules that vary between species. Along Long Island Marshes, the most common sponges are in the class Demospongia. These sponges are irregular in shape and have silicone-based spicules. Water passes through inflowing cannels to flagellated chambers (i.e., chambers lined with cells that have hair-like protrusions from their cell surfaces that are flagella) where it is filtered. It then passes through out-flowing channels that come together into a chimney-like structure known as osculum. Sponges can efficiently filter bacteria-sized particles from the water.
- In LIS the most common sponges are Halichondria, Haliclona and Boring Sponges.
- Halichondria is very common off the Connecticut coastline and has upright, finger-like lobe in a yellow-tan or gold color.
- Haliclona is a low growing sponge with rounded chimney like structure, in a tan to a rich salmon color.
- Boring Sponges are found in empty mollosc shells and are a bright sulfur-yellow color. Different species are identified by size of the bored holes. The sponge fills the empty shell and then spreads over both surfaces, eventually destroying the entire shell.
- Members of this phylum are characterized by the possession of stinging cells (nematocysts). Nematocysts are situated on tentacles surrounding a mouth that leads to the only internal cavity, the digestive cavity. There are usually two life forms: non-motile and free-swimming. These animals are usually predators. We will concentrate on two classes of Cnidarians: Scyphoza (jellyfish) and Anthozoa (sea anemones).
- The jellyfish common to LIS: Moonjelly (Aurelia aurita) and Lions Mane Jellyfish (cyanea capillata). The MoonJelly is small (15-25 cm diameter) with a grayish-white bell and quite flat. Very common in LIS during the summer. The Lions Mane Jellyfish is larger than the Moon Jelly (a diameter of up to 25 cm) but obtains diameters of up to 2.5 m in arctic waters. The bell is relatively deep, with the rim divided into eight sections and the stinging tentacles are long and arranged in eight clusters. This is a very common jellyfish in spring in LIS.
- Common sea anemones to LIS: Common Sea Anemone (Metridium senile) large, up to 10 cm high and 7 cm wide, with a yellow-bown to whitish-pink or dark brown color. Pallid Sea Anemone (Diadumine leucolena) common on eelgrass as well as under stones or pilings. Burrowing Sea Anemone (Haloclava producta) these animals bury themselves in the mud or sandy bottom with only their tentacles exposed. It is delicate and transparent.
