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What are phytoplankton blooms?
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Phytoplankton blooms occur when certain species of phytoplankton (which are also called algae) grow very fast and accumulate to great numbers. Phytoplankton are microscopic plants that live in oceans or lakes, and they are an important part of the ocean food web. They synthesize energy from sunlight, so they need to live near the surface of the water, what oceanographers call the "photic zone". They also need nutrients to grow, just like land plants. They are present all the time in low numbers, but when there is an abundance of the nutrients they need, such as nitrate, phosphate, light etc., sometimes phytoplankton blooms will occur. When the water is dense with phytoplankton, it can become red, brown, or some other color, depending on the color pigments in the phytoplankton. Although most of the plants we see on land are green, phytoplankton in the ocean are typically red or brown. You may have heard the term "red tide", which is a common name for a phytoplankton bloom caused species with reddish pigments. However, "red tide" is not an accurate name for phytoplankton blooms and is not commonly used by scientists because phytoplankton blooms are not associated with tides, can be other colors, or might not even be visible.
There are several ways a phytoplankton bloom can be harmful. First, densely growing phytoplankton can form a "blanket" at the surface of the water that prevents sunlight from reaching other plants. This lack of light will kill grasses and plants that live along the bottom of the ocean. Also, once the phytoplankton start to decay, they can use up so much oxygen in the water that fish and other marine life suffocate. You might also get sick from swimming in some phytoplankton blooms or eating shellfish because some phytoplankton contain toxins which can be released into the water or accumulate by shellfish.
So, while nutrients which feed phytoplankton aren't harmful themselves, too much drainage of nutrients into the coastal ocean can indirectly lead to harmful phytoplankton blooms. Nutrients are not pollution like trash, oil, or toxic waste, but it can still cause problems. Nutrient pollution is sometimes called eutrophication.
Are there phytoplankton in the water at the Whyville beaches? Is the water turning red? Here's what you can do to help prevent fish and other sea creatures from dying and washing up at our favorite beaches:
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What to do?
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1. Collect a sample of water from the beach by going to the beach and saying, sample. Analyze it under the microscope in this lab to see what's in it. You'll want to compare what you see to the samples in the Culture Collection and figure out what type(s) of phytoplankton might be blooming and what nutrient might be causing this bloom.
2. When you've got a nutrient suspect in mind, borrow one of Sonya's sensors to trace the nutrient pollution to its source. Click on the sensor you wish to borrow, then go to the WhOI dock and jump on a motorboat to hunt down the nutrient source. You'll want to bring along some of Sonya's marsh grass seedlings.
3. While you are in the boat, pay attention to the sensor's readout. It shows the nutrient concentration in microMolar (uM), which is 1/1000000 (one millionth) of a mole per liter. Find the direction in which the concentration increases and head that way to discover the sources of the nutrient pollution, which will be along the shore and very highly concentrated (close to 1000 uM).
4. Once you think you've found the source, plant the seedlings by saying "plant". Marsh grasses soak up the nutrients for their own use, preventing them from draining into the ocean.
If enough seedlings are planted, we can stop nutrient pollution and help prevent phytoplankton blooms in Whyville. One person doing this won't be enough, so spread the word and mobilize our town! When a phytoplankton bloom is stemmed, all the citizens who have contributed to the planting will receive clam rewards.
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