SeaWiFS The Meaning of Ocean Color The Role of Phytoplankton The Carbon Absorbing Oceans

What is ocean color? Why is ocean color important? How is ocean color measured? Global view of phytoplankton concentrations. Red areas contain the most life, while the purple areas are nearly empty of life. Regional view of phytoplankton concentrations. Photo taken of the North Eastern United States. Regional view of phytoplankton concentrations. Photo taken of Long Island, NY and Boston, MA. Why is ocean color important? The major reason scientists measure ocean color is to study phytoplankton, the microscopic ocean plants which form the base of the oceanic food web. Phytoplankton use sunlight and carbon dioxide to produce organic carbon. This process, called photosynthesis, is possible because plants contain chlorophyll, green-colored compounds which trap the energy from sunlight. Chlorophyll is also responsible for giving most marine and land plants a green color. Because different types of phytoplankton have different kinds of chlorophyll, measuring the color of an area of the ocean allows us to estimate the amount and general type of phytoplankton in that area. Looking at ocean color also tells us about the health and chemistry of the ocean. In addition to light and carbon dioxide, phytoplankton also require nutrients such as nitrogen and phosphorus. Phytoplankton are found where nutrient levels are high. Areas of the ocean where there is little phytoplankton shows where pollutants have poisoned the ocean and prevented plant growth. Other conditions can also affect phytoplankton growth, such as seasonal changes. Since phytoplankton depend on specific conditions for growth, they frequently become the first to be affected by a change in their environment. Comparing images taken at different times tells us which changes occur over time. Because phytoplankton drift with the water, patterns in ocean color can also be used to study ocean currents. Why are phytoplankton so important? These small plants are the beginning of the food chain for most of the planet. As phytoplankton grow and multiply, small fish and other animals eat them as food. Larger animals then eat these smaller ones. The ocean fishing industry finds good fishing spots by looking at ocean color images to locate areas rich in phytoplankton. Ocean color has proved to be a valuable research tool for the study of ocean biology, chemistry, and physics. Covering about seventy percent of the Earth's surface, oceans are central to the continued existence of life on our planet. The oceans are where life first appeared on Earth. The largest creatures on Earth (whales) and the smallest (bacteria and viruses) live in the oceans. We rely on the ocean for many things, including food: water, transportation, recreation, minerals, and energy. When ocean currents change, they cause changes in global weather patterns which can cause droughts, floods, and storms.

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