When fertilizers are used in gardening and agriculture, the excess eventually ends up in the ocean. One result is a “dead zone” — an area with very low levels of oxygen in the water — the size of New Jersey in the Gulf of Mexico during the spring and summer. Since all marine life requires oxygen to live, including fish and shrimp, they must flee the area or die. Many other coastal areas are at risk too. So, use fertilizer sparingly and remember more is usually not better.