Diatoms, while invisible to the naked eye, are essential to the ecosystem and human survival. These tiny microalgae prolifically generate oxygen and are famous for their shining silica shells of many forms. They're the main ingredient in the product diatomaceous earth.
Crucial to the health of people and planet, these tiny, single-celled organisms belong to the group Bacillariophyta. They're a significant part of Earth's biomass.
Diatom shells are found up to 800 meters deep on the ocean floor. Each year, the Amazon basin receives 27 million tons of diatom shell dust carried by transatlantic winds from the African Bodélé Depression, once a region of freshwater lakes.
This pic is a recreation based on a photo by Julie Laurin.
What are Diatoms?
Diatoms are a diverse group of microalgae characterized by their unique silica-based cell walls, known as frustules. These intricate shells come in various shapes and sizes as Nature flexes her architectural finesse. The shells of diatoms are called jewels of the sea.
With over 100,000 species, diatoms are essential to aquatic ecosystems as primary producers. As a eukaryotic organism, a diatom has a defined nucleus and specialized cellular structures. Its ability to photosynthesize enables it to convert sunlight into energy.
Approximately 20 to 50 percent of the Earth’s oxygen supply each year comes from diatoms. These microscopic beings, invisible to the eye as individuals, are essential for sustaining life on our planet.
Habitats of Diatoms
Diatoms enjoy diverse environments from oceans and freshwater lakes to wetlands and soil. They reproduce prolifically in nutrient-rich waters, often forming dense populations in the photic zone where sunlight penetrates.
Here they photosynthesize solar light. Factors such as light, temperature, and nutrient supply significantly influence their distribution.
Depending on the species, diatoms can be found in both pelagic (open water) and benthic (bottom-dwelling) habitats. Some diatoms attach themselves to surfaces such as rocks and aquatic plants, creating vibrant communities seen as glowing layers of biofilm.
Diatoms exist as single cells or form colonies, depending on environmental conditions and species. Colonial behavior includes forming aggregates to improve buoyancy or increase nutrient uptake.
Colonies can manifest as chains, clusters, or form biofilms. Chains help them stay buoyant and closer to sunlight. Cooperative behavior like biofilm formation aids survival, enhances nutrient availability and protects the diatoms from predatory grazers.
How Diatoms Eat
Diatoms are autotrophic, meaning they produce their own food through photosynthesis. Using chlorophyll and other pigments, they convert carbon dioxide and sunlight into organic compounds.
This process not only sustains the diatoms but also forms the base of many aquatic food webs. As primary producers, diatoms play a significant role in regulating carbon cycling in Earth's ecosystems.
They also absorb vital nutrients from their surroundings, including silica, nitrates, and phosphates. In nutrient-rich waters, diatoms can show explosive growth, sometimes resulting in algal blooms that dramatically affect local ecosystems.
Diatoms are also a source of nourishment in aquatic food webs, consumed by organisms like zooplankton and small fish. A single species of diatom, Thalassiosira pseudonana, can support populations of krill, a crucial food source for larger marine animals such as whales.
Diatom Reproduction
Diatoms usually reproduce asexually via binary fission or mitosis. A single diatom divides into two identical daughter cells. Each daughter cell inherits one of the parent’s frustules while producing a new half. This leads to decreases in size over generations.
Due to the constraints of their silica shells, diatoms eventually undergo sexual reproduction, forming gametes to ensure genetic diversity. Sexual reproduction occurs less frequently.
When two diatoms meet they exchange genetic material, creating a zygote. This grows into a larger diatom, creating a large-small cycle prevalent among diatoms. It helps diatoms adapt to changing environments, vital for their survival.
Making Silica and Creating Silica Shells
Diatoms are unique in their ability to assimilate silica from their environment, which they use to construct their characteristic frustules. This process involves the uptake of dissolved silica through their cell membranes.
Inside the cell, a diatom absorbs silica, which is transported to vesicles known as silicalemma. Silicic acid is polymerized to make silica, which then forms intricate shell structures. The elaborate designs of their frustules appear in different geometric shapes.
Functions in Nature and Importance to the Environment
Diatoms are essential to nutrient cycling. They're a food source for numerous aquatic organisms, including zooplankton and small fish. They generate up to 50 percent of the Earth's oxygen supply each year.
Diatoms, like rotifers and other microbial life, are indicators of water quality and ecosystem health. Their presence and diversity reflect environmental conditions.
In carbon fixation diatoms are natural carbon sinks. By absorbing carbon dioxide during photosynthesis and storing it in their biomass, they help mitigate climate change.
Diatoms help cycle essential nutrients throughout aquatic ecosystems. In coastal ecosystems, they contribute to sediment formation and stabilization, creating habitats for marine organisms and promoting rich biodiversity.
Human Uses of Diatoms
Beyond their ecological significance, diatoms have various applications in human industry. Their silica shells are harvested and processed for use in products such as filters, abrasives and toothpaste.
Diatomaceous earth, a natural product derived from fossilized diatom shells, is popular in home pest control and agriculture. It's a food additive due to its high absorbent properties and also used to filter water.
The fine particles of diatomaceous earth are used in household cleaners, polishes, and personal care products as a mild abrasive or exfoliant. Diatomaceous earth, diatomite, celite or kieselguhr is found in natural state as a soft, siliceous sedimentary rock.
It's easily crumbled into a fine white to off-white powder. Diatomaceous earth consists of the fossilized remains of diatoms accumulated over millions of years.
Hazards Associated with Diatoms
While diatoms are generally harmless, some species can produce toxins dangerousl to aquatic life and humans. Harmful algal blooms (HABs) can occur when certain diatom populations explode in number, leading to declines in oxygen levels.
At the same time, toxin release affects marine life and human health. These blooms are often triggered by nutrient runoff. Monitoring diatom populations is crucial in maintaining balanced ecosystems.
In humans and other animals, diatomaceous earth can endanger respiratory health. Wear a mask when using it and keep pets and children away from the area.
Facts about Diatoms
Microscopic Diversity: Diatoms exhibit incredible diversity, with thousands of species ranging from tiny diatom cells to larger, visible colonies.
Oldest Silica Structures: Some diatoms have a fossil record dating back to the Jurassic period, making them among the oldest organisms on Earth. Their shells are found in sedimentary rocks, with some deposits reaching depths of several kilometers.
Movement: A few diatom species can move using tiny hair-like structures, despite most being primarily stationary.
Bioindicators: Scientists use diatom populations to assess the health of freshwater and marine ecosystems, as changes in their communities can signal environmental shifts.
Oxygen Production: Just one cubic meter of water in certain conditions can contain millions of diatom cells, producing significant amounts of oxygen in a short time.
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