The Susquehanna River's Food Chain

The Susquehanna River's Food Chain. . , The life cycle in the Susquehanna River begins with bacteria, which are nurtured by organic materials in the water. Microscopic water plants called algae use substances formed by bacteria and replenish the oxygen supply. Protozoa eat algae and provide food for aquatic insects, snails, and other invertebrates. Small fish eat insects and snails, and larger fish eat smaller fish., As one organism eats another, energy originally from the sun is transferred through the food chain to each succeeding consumer. Toxins, either artificial or found in tiny amounts in nature, also grow more concentrated at each level. Humans and animals, such as fisheating hawks and eagles, at the "top" of the food chain accumulate the highest levels of toxins. The disruption or disappearance of any one of these "links" to the food chain may indicate the presence of pollution., Pollution of the river can have disastrous results. A major ecological problem arose in the 1970's when the raw sewage load In the Susquehanna grew too great for the river to handle. It soon became clear that the towns along the river could no longer empty their municipal sewers directly into the water. Dissolved oxygen, even in the upper reaches of the river, became depleted. Many native animals could no longer survive and disappeared, or were replaced by more pollutiontolerant species.