Question

Diatoms are mostly asexual members of the phytoplankton. They obtain their nutrition from functional chloroplasts, and each diatom is encased within two porous, glasslike valves. Which question would be most important for one interested in the day-to-day survival of individual diatoms?

Diatoms are mostly asexual members of the phytoplankton. They obtain their nutrition from functional chloroplasts, and each diatom is encased within two porous, glasslike valves. Which question would be most important for one interested in the day-to-day survival of individual diatoms?

How do diatoms get transported from one location on the water's surface layers to another location on the surface?

How do diatoms with their glasslike valves avoid being shattered by the action of waves?

How do diatom sperm cells locate diatom egg cells?

How do diatoms with their glasslike valves keep from sinking into poorly lit waters?

How does carbon dioxide get into these protists with their glasslike valves?

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Answer 1

1. Transportation of diatoms from one location to other on the water's surface:

Generally the diatoms have a higher density than water due to the dense cell wall which means they have no buoyancy and readily sink. But they also exist in the planktonic form i.e they can float on water. For such behaviour they usually rely on the turbulence caused by the wind which leads to the mixing of upper layers of the ocean waters. Diatoms can grow in colonial chains known as flake by adhering to each other with the help of extracellular polymeric substance.This increases the surface area to volume ratio and allows the diatoms to stay suspended in the water column longer. Single diatomic cell may regulate buoyancy via an ionic pump. The locomotion/transfer of diatoms form one location to another on the water surface is still in speculation as the suspension of diatoms on the water surface is not for longer duration. But it is hypothesised that a type of locomotion called as gliding allows these diatoms to move across the water surfaces aided by the adhesive mucilage which is secreted by the raphe. But in order for a diatom cell to move it must adhere itself to a solid substrate.

2. Diatoms contain a silica cell wall known as frustule or shell which is made up of two valves overlapping each other. This unique cell wall is composed od biogenic silica from dissolved silica in water and is very strong. The shell protects these diatomic cells from predators as well as from powerful action waves. Therefore, these silica cell walls are required for the survival of the diatoms for preventing the predators and powerful action waves. But if the diatoms are grown in a stagnant water in vitro then also their survival rate matters even though there would be no predator or action waves as such.

3. Usually the reproduction in these organisms is asexual which results in the foemation of 2 daughter cells which receives one of the two frustule from the parent. After the binary fission there is usually a decrease in average cell size of the population as one of the daughter cell receives a larger frustule while the other receives the smaller one. So to prevent this reduction in the cell size the siatoms undergo sexual reproduction and auxospore formation. This means that the diatoms can even survive without sexual reproduction and hence does not require it to survive the day to day life.

4. For a cell to survive the most important factor is their ingestion and digestion. If these two factors are satisfies the cell will remain healthy and hence can protect itself from the predators as well as the action waves. It has been suggested through research that the silica cell wall affects the ingestion as well as digestion of the diatomic cell. In low lit regions of the oceans these cells cannot survive and requires to float on the water surface which is also aided by the frustule by adhering to a substrate. Therefore, this is the main point for the survival of the diatomic cell.

5. Diatoms fix carbon by removing it from the atmosphere. As the diatoms are photosynthetic in nature they convert the carbon dioxide to organic carbom in the form of sugar and oxygen released. This mechanism of carbon fixation is a secondary function of diatoms which means even without fixing carbon the diatoms can survive.

Therefore, the answer to the question is for the survival of diatoms the most important question is:

How do diatoms with their glasslike valves keep from sinking into poorly lit waters?