Slide 1
A diatom builds a silica wall around its cell
Diatoms are microscopic algae with walls made largely of silica, a major component of sand and glass. The patterned covering is called a frustule and surrounds the living cell.
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Silica is also a major component of sand and glass, but a diatom constructs its wall biologically. The material's familiar chemistry does not make the organism a manufactured glass object.
Slide 2
Wall patterns help identify different diatoms
Diatom frustules have varied shapes and fine structures. Researchers use those features to help identify organisms in a water sample.
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Some diatoms live as single cells while others form chains or colonies. A long structure under a microscope may therefore contain several cells rather than one exceptionally large individual.
Slide 3
Photosynthesis feeds the wider food web
Diatoms use photosynthesis to build organic material. Grazers consume them and pass some of that production onward to larger animals.
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Diatoms also provide important nutritional compounds, including fatty acids. Their influence on a food web concerns the quality of food as well as the amount of carbon produced.
Slide 4
Light and nutrients influence growth and blooms
Light and nutrient availability influence diatom growth. Suitable conditions can support a bloom, a period of rapidly increasing abundance.
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Silicon supply matters because new cells need material for their walls. A photosynthetic organism can therefore be limited by something other than sunlight or the nutrients usually discussed for land plants.
Slide 5
Preserved walls can record past communities
Diatom remains can accumulate in sediment after the living cells die. Their identifiable structures help researchers reconstruct past environmental communities.
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Different species favour different conditions, so changes through a sediment core can provide environmental clues. Interpretation still depends on preservation and ecological knowledge, not merely counting every shell as equivalent.
Sources
- The Spring Bloom Awakens Long Island Sound
NOAA Fisheries
- An Ode to Diatoms
NOAA Fisheries
- Diatoms as paleoecological indicators
NOAA AOML