ABOUT THE WHALES
Every Hyannis Whale Watcher cruise is a unique opportunity to experience Cape Cod's most amazing residents - the whales. To help you better appreciate your cruise adventure, we've created a few "primers" outlining the various species of whales you may see, their history and environment, the food they eat and the other creatures that inhabit the Cape Cod waters.

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Whale Species | Marine Life | Stellwagen Bank | Food Webs | more coming soon!

FOOD WEBS
In simplest terms, food webs (or chains) can be thought of as the “Who eats Who” of the natural world. By looking a bit deeper into the science of ecology, an understanding of this phenomenon can be gained. Ecology is simply the study of the relationships of organisms to their environment. In the truest sense, a food web is a model of how energy circulates through an ecosystem. An ecosystem is simply a community of microorganisms, plants, and animals that are linked by energy and nutrient flows and that interact with each other and the physical environment. Let’s look at the food web of Stellwagen Bank.

One of the easiest ways to understand the shape of a food web is to picture the shape of a pyramid (but not the one on your cereal box!). The broad base of the pyramid holds up all of the other levels and is the foundation for the entire structure. The different levels on up the pyramid are known as TROPHIC LEVELS. A trophic level shows an organism’s position in the food chain, determined by the number of energy-transfer steps to that level. Let’s start at the base.

At Stellwagen Bank, the base of the pyramid, or first trophic level, is composed of microscopic plants called phytoplankton. Through a process called photosynthesis, these tiny green plants have the ability to convert the sun’s light into simple sugars or carbohydrates. Since photosynthetic plants produce their own food, they are known as PRODUCERS.

Just above the first trophic level, is the next level of the pyramid where we find the PRIMARY CONSUMERS. All animals that eat only plants are primary consumers. They are also known as HERBIVORES. At Stellwagen Bank, this consists of a large group of tiny animals known as zooplankton. They eat, or consume, the phytoplankton, taking the sun’s energy to the next trophic level. Let’s keep moving up.

The next trophic level is where we find, can you guess it? That’s right, this is where we find the SECONDARY CONSUMERS. These are those animals which eat the primary consumers. Animals which eat other animals (meat) are called CARNIVORES. The sun’s energy has now moved up the food pyramid three times. First, from the photosynthesis of the phytoplankton; second, from the herbivores which ate those plants; and finally as the primary consumers where eaten by the secondary consumers. At this point, the whole business of food webs gets more complicated, but it can still be viewed simply by looking at how the sun’s original energy is being transported through the tropic levels.

Secondary consumers need to eat more food to gain the same amount of energy as a primary consumer or a producer. This means that for a secondary consumer to survive, there must be more food available. Some secondary predators at Stellwagen Bank are large, like the Humpback Whales, while others are small like the Sand Lance. They all fit into the structure of the food pyramid, from very low on the structure, all the way to the top.

Atlantic Herring, for example, are secondary consumers because they eat primary consumers like zooplankton. But their position is low in the food pyramid. The herring may be eaten by a larger secondary consumer, such as an adult Bluefish, which sits higher on the pyramid. That Bluefish may be eaten by a tuna. That tuna may later be eaten by an Orca. The very largest secondary consumers are known as APEX PREDATORS. They sit at the very tip-top of the pyramid, and have few, if any, predators. Orcas are a fine example of an apex predator, and, in places where there are no Orcas, Bluefin Tuna may be considered an apex predator. But wait, it gets even more complicated, can you believe it?

Many species of marine animals host a few parasites, those animals which live off of the energy of others. There are both internal (inside the body) and external (outside the body) parasites. An apex predator like an Orca can host as many as 20 species of parasites. Some of these parasites will even eat other parasites. The Orca’s parasites get their energy from the Orca, which got their energy from the Bluefin Tuna, which got its energy from the Bluefish, which got its energy from the Atlantic Herring, which got its energy from the zooplankton, which got its energy from the phytoplankton, which got its energy from the Sun. Wow, that sure is complicated web!

It should be mentioned that all of the animals mentioned have their own sets of parasites, and that at some point in their life cycle, they may be at a different level on the food pyramid, sometimes by a whole trophic level. This really is a complicated ecological process. This is why scientists prefer to think of predator-prey interactions in terms of a great web of life, where one pull on any strand, can effect the whole structure.

Eventually, the lives of all animals come to an end. At this point, the energy from that animal is released back into the environment. This is assisted by the decomposers, or TERTIARY CONSUMERS. Many types animals and bacteria scavenge from carcasses. This releases energy in the form of nutrients which are used by phytoplankton as they are busy photosynthesizing and creating more energy to fuel this cycle of life at Stellwagen Bank.

Which is the most important trophic level? There is not one. Each level depends on the well-being of the other. Stellwagen Bank is like the game Jenga. The entire structure weakens every time a portion of it is removed. If too many pieces are removed, the whole structure collapses. This is where humans come in. It is the responsibility of all people and their governments to protect the world’s oceans and monitor their health. Places like Stellwagen Bank National Marine Sanctuary gives scientists a chance to look at changes that are under way. By getting a better understanding on how the oceans work, and how humans are affecting them, better decisions can be made in the future.

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