Diatoms

Diatoms are microscopic, photosynthetic algae with silica cell walls called frustules. In Earth Systems Science, they are a major part of marine primary production and the carbon cycle.

What are Diatoms?

Diatoms are a type of phytoplankton in Earth Systems Science, tiny photosynthetic organisms that drift in the sunlit ocean and other waters. They make their own food using sunlight, carbon dioxide, and nutrients, so they sit near the base of many aquatic food webs.

What makes diatoms stand out is their shell-like outer wall, called a frustule, made from silica. Think of it like a glassy box with a detailed pattern. That silica structure protects the cell and gives diatoms their distinctive shapes, which is why scientists often identify species by the look of the frustule under a microscope.

Diatoms matter most where light and nutrients overlap, especially in marine surface waters. When conditions are good, they can reproduce quickly and form blooms. Those blooms can turn a water sample full of life, but they can also change water quality and affect how much oxygen and carbon are moving through the system.

In the ocean, diatoms are a major food source for zooplankton, which then get eaten by small fish and larger predators. That makes diatoms a direct link between sunlight and higher trophic levels. If diatom populations rise or fall, the effects can ripple through the whole food web.

They also connect to the carbon cycle in a very Earth-systems way. When diatoms die, many sink out of the surface ocean. Some of that carbon ends up stored in deep water or seafloor sediments, while the silica frustules help them persist long enough to transport material downward. That is one reason diatoms are part of both short-term ecosystem dynamics and long-term carbon storage.

Why Diatoms matter in Earth Systems Science

Diatoms show how marine ecosystems are tied to the atmosphere, hydrosphere, and biosphere all at once. They turn sunlight and dissolved carbon into biomass, so they are one of the main places where ocean primary production starts. Without that first step, the rest of the food web, from zooplankton to fish, has much less energy to work with.

This term also gives you a clean example of biogeochemical cycling. Diatoms do not just live in seawater, they change what is in the water and what sinks out of it. Their growth, bloom cycles, and sinking frustules affect oxygen production, nutrient use, and carbon storage in ways that connect local biology to global Earth systems.

In marine biodiversity topics, diatoms help you explain why certain waters are so productive and how microscopic organisms can shape entire habitats. They also show why ocean science is not just about big animals or visible ecosystems. A single-celled alga can influence food availability, water quality, and carbon movement across large parts of the ocean.

How Diatoms connect across the course

Phytoplankton

Diatoms are one major group of phytoplankton, so this broader term helps place them in the ocean’s base layer of photosynthetic life. When a question asks about primary producers in surface waters, diatoms are often one of the best examples to name. Not all phytoplankton are diatoms, but many diatom features make sense once you know they are drifting photosynthesizers.

Silica

Silica is the material that makes up a diatom’s frustule. That connection matters because the shell affects how diatoms are identified, how they sink after death, and how silica moves through marine systems. If you see a question about mineral cycling in the ocean, diatoms are a good biological example of a silica-based structure.

Food Web

Diatoms sit near the bottom of many marine food webs, where they convert sunlight into energy that moves upward through zooplankton, fish, and larger predators. This is why a change in diatom abundance can shift the whole system. They are a simple way to trace energy flow from primary producers to higher consumers.

zooplankton

Zooplankton often graze on diatoms, so the two are closely linked in marine ecosystems. If diatom blooms increase, zooplankton may get more food, which can affect the populations above them. This relationship is useful for explaining how microscopic changes can influence larger ocean communities.

Are Diatoms on the Earth Systems Science exam?

A quiz question might show a microscope image and ask you to identify the organism by its silica frustule, or it might ask which group forms the base of a marine food web. In a lab, you may compare water samples before and after a bloom and explain why diatoms increased. In a short response or discussion, you could trace how diatom photosynthesis moves carbon from seawater into biomass, then into sinking sediment after the cells die. If a prompt asks about ecosystem change, diatoms are a strong example of how nutrient levels, light, and food availability connect in the ocean.

Diatoms vs Dinoflagellates

Diatoms and dinoflagellates are both common phytoplankton, but they are not built the same way. Diatoms have silica frustules, while dinoflagellates usually have different cell coverings and often move with two flagella. In marine ecology questions, diatoms are often tied to silica and sinking carbon, while dinoflagellates are more often discussed in relation to movement and some harmful blooms.

Key things to remember about Diatoms

• Diatoms are microscopic photosynthetic algae that act as major primary producers in marine ecosystems.

• Their silica frustules are the feature that makes them easy to recognize and helps them influence sinking and sediment formation.

• Diatoms feed ocean food webs by turning sunlight into biomass that zooplankton and fish can eat.

• Their blooms can change water quality, oxygen production, and nutrient use in surface waters.

• When diatoms die and sink, they help move carbon from the surface ocean into deeper water and sediments.

Frequently asked questions about Diatoms

What are diatoms in Earth Systems Science?

Diatoms are single-celled photosynthetic organisms in the ocean and other waters, and they are a major type of phytoplankton. In Earth Systems Science, you usually study them as primary producers that connect sunlight, marine food webs, and the carbon cycle.

What is a diatom frustule?

A frustule is the silica-based outer wall of a diatom. It works like a glassy shell with detailed patterns, and scientists often use those patterns to identify species. The frustule also affects how diatoms sink and how their remains enter sediments.

Are diatoms the same as phytoplankton?

No. Diatoms are one group within phytoplankton. Phytoplankton is the larger category for photosynthetic organisms that drift in water, while diatoms are a specific type with silica cell walls.

Why do diatoms matter in marine food webs?

Diatoms turn sunlight into energy-rich biomass, so they support the organisms that eat them. Zooplankton often feed on diatoms, and that energy can then move to fish and larger marine animals. If diatom abundance changes, the whole food web can shift.