Where the River Meets the Sea

The simplest definition of an estuary is the place where salt and fresh water mix, typically at the mouth of a river. These transition zones between riverine and marine environments are among the most productive natural habitats in the world. Many ocean-going fish species spend their youth in estuaries, enjoying protection from large predators and an abundance of nutrients from the inflow of both freshwater and seawater.

They are popular with humans as well. Currently about 60% of the world's population lives along estuaries and the coast. Consequently, they are also subject to degradation from sedimentation, pollutants present in agricultural, domestic, and industrial runoff, and eutrophication due to nutrient overload.

Students visited the mouth of the Pajaro River to see where their watershed ends and the Monterey Bay National Marine Sanctuary begins. We pulled out our water quality kits again and tested for dissolved oxygen, nitrates, and phosphates.

Compared to test results from Grizzly Flat (upper watershed) and the junction of Corralitos and Salsipuedes Creeks (lower watershed), oxygen levels were lower and both nitrate and phosphate levels were higher. Students hypothesized that the cumulative impact of agricultural practices in the region is negatively affecting the quality of the Pajaro River.

This estuary is also home to a population of Western Snowy Plovers, a threatened shorebird that nests on the beach.