Gregory Skomal is an accomplished marine biologist, underwater explorer, photographer, and author. Such harmful algal blooms (HABs) cause significant economic loss every year in the seafood industry and in tourist communities, and scientists are working to understand the causes of these blooms and to devise ways to predict and prevent them. Other species produce toxins that cause can cause illness or death among humans and even whales that are either exposed to the toxins or eat shellfish that accumulate toxins. Dense blooms of some organisms can deplete oxygen in coastal waters, causing fish and shellfish to suffocate. Some phytoplankton have a direct impact humans and other animals. Photosynthetic bacteria are especially important in the nutrient-poor open ocean, where they scavenge and release scarce vitamins and other micronutrients that help sustain other marine life. They take up, transform, and recycle elements needed by other organisms, and help cycle elements between species in the ocean. Phytoplankton are critical to other ocean biogeochemical cycles, as well. As a result, many people are discussing plans to fertilize large areas of the ocean with iron to promote phytoplankton blooms that would transfer more carbon from the atmosphere to the deep sea. Phytoplankton growth is often limited by the scarcity of iron in the ocean. Because they take up carbon dioxide from the atmosphere, when they die they sink they carry this atmospheric carbon to the deep sea, making phytoplankton an important actor in the climate system. Through photosynthesis these organisms transform inorganic carbon in the atmosphere and in seawater into organic compounds, making them an essential part of Earth's carbon cycle. In short, they make most other ocean life possible. Phytoplankton also form the base of virtually every ocean food web. They generate about half the atmosphere's oxygen, as much per year as all land plants. Phytoplankton are some of Earth's most critical organisms and so it is vital study and understand them. The group also includes cyanobacteria, which are believed to be among the oldest organisms on Earth and the origin of the photosynthetic organelles in plant cells known as chloroplasts. Scientists now know these bacteria are responsible for half of the ocean's primary productivity and are the most abundant organisms in the sea. Too small to be caught in any net, these organisms were unknown until the 1970s, when improved technology made them visible. These tiny cells, some only a micron across, are invisible but present in numbers of hundreds of thousands of cells per tablespoon of ocean water. The other type of phytoplankton cells, more primitive but far more abundant than algae, is photosynthetic bacteria. Occasionally, these organisms form blooms-rapid population explosions-in response to changing seasons and the availability of nutrients such as nitrogen, iron, and phosphorus. These forms include diatoms and are most abundant near coasts. The larger category include, single-celled algae known as protists-advanced eukaryotic cells, similar to protozoans. Phytoplankton comprise two very different kinds of organisms. The thickness of this layer of the ocean-the euphotic zone-varies depending on water clarity, but is at most limited to the top 200 to 300 meters (600 to 900 feet), out of an average ocean depth of 4,000 meters (13,000 feet). They are what is known as primary producers of the ocean-the organisms that form the base of the food chain.īecause they need light, phytoplankton live near the surface, where enough sunlight can penetrate to power photosynthesis. Like land plants, they take up carbon dioxide, make carbohydrates using light energy, and release oxygen. Phytoplankton are mostly microscopic, single-celled photosynthetic organisms that live suspended in water.
0 kommentar(er)
