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Chains & Webs

Bayou-Diversity (17 March 2019) The field of ecology has its own bag of words and terms used to describe the relationships between plants and animals and their environment. Food chain is one such term. Most folks grasp the basic meaning as “the big fish eats the little fish,” which is pretty much the simplified truth. A more thorough definition might be a “chain of organisms in a community through which energy is transferred.” An ecological community consists of the plants and animals living in a particular habitat. Each animal link in the chain obtains energy by feeding on the link below it, and in turn passes the energy on when it is eaten by the next link. A chain typically begins with a green plant (a producer) that gets its energy from the sun and proceeds through herbivores and then carnivores (consumers). Along a Louisiana bayou, a chain might begin with cattails that are eaten by a muskrat, which then falls prey to an alligator whose destiny ends in a jambalaya for the local Lion’s Club annual fundraiser. Since every living organism is a link, there are many food chains in a community. Cumulatively, all of these food chains comprise a food web in the given area.

Energy is not the only thing that passes through food chains and circulates within the strands of a food web. Contaminants and pollutants, if present in the environment, often tag along for the ride and become more concentrated in each successive link of the chain. The process almost led to the demise of bald eagles when levels of DDT became so elevated in adult birds that reproductive failure ensued until the pesticide was banned. In Louisiana, mercury poison advisories are ubiquitous on state water bodies in some fish, usually large, predaceous species at the hot end of the food chain. Globally, oceans are being swamped with an estimated 600,000 tons of plastic microfibers annually from a variety of sources, and plankton at the critical lower end of the marine food chain are eating them. Their journey in time up through the links of “little fish and bigger fish” and finally into humans is a logical progression.

Within the broader scope of this topic, however, the greatest danger to our species is for the majority to get out of bed every morning oblivious to the fact that each of us is an inescapable link in a multitude of chains comprising a myriad of webs. Our well-being is welded hard to the health of the others. It is also worth noting that in the big picture, ours is the only unnecessary link.


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