Dissolved oxygen (DO) refers to the amount of oxygen that is present in the water. Just like humans and animals on land, all of the Bay's living creatures — from worms to fish to crabs — need oxygen to survive.
Scientists use chlorophyll a to measure the amount of algae present in the Bay. High amounts of chlorophyll a in the Bay's waters are an indicator of nutrient pollution because excess nutrients fuel the growth of algae.
Water clarity is a measure of the amount of sunlight that can penetrate through the water. Clear water is indicative of a healthy Bay, though clarity will always fluctuate naturally depending on weather conditions.
The distribution and stability of the Bay's ecosystem depends on three important physical characteristics of the water: salinity, temperature and circulation. Each affects and is affected by the others.