Phytoplanktons are algae that are single-celled eukaryotic cells. There are many types of phytoplankton. Among them, diatoms and dinoflagellates are the two most common phytoplankton species that can be found in seawater. They are able to photosynthesize, and they contribute for the food production in marine environments and also for the generation of oxygen.
1. Overview and Key Difference
2. What are Diatoms
3. What are Dinoflagellates
4. Similarities Between Diatoms and Dinoflagellates
5. Side by Side Comparison – Diatoms vs Dinoflagellates in Tabular Form
What are Diatoms?
Diatoms, also called as Bacillariophyta, are a major type of phytoplankton. They include mainly marine species. They are single-celled, eukaryotic algae. The diatoms can be classified mainly based on their shape. There are two categories namely centric diatoms and pennate diatoms. Centric diatoms have a radial symmetrical shape. In contrast, pennate diatoms show bilateral symmetry. Diatoms are good indicators of water quality. The unique feature of diatoms is the presence of a theca. Theca is an external cell wall covering the cell. It consists of silicon dioxide and is a hardened shell-like structure. The theca has two parts that fit nicely with each other. They are the epitheca and the hypotheca. The theca also contains many pores. They appear like thin lines on the external cell wall.
Diatoms have pigments such as chlorophyll and fucoxanthin. These pigments provide characteristic colours to diatoms. There are over 10,000 species of identified diatoms such as Coscinodiscus, Ditylum and Lauderia, etc.
What are Dinoflagellates?
Dinoflagellates belong to the phylum Pyrrhophyta. They are marine, single-celled, eukaryotic algae which are phytoplankton. They have a biflagellated structure. The presence of two flagella limits the mobility of these organisms. Therefore, they are less motile in nature.
The cell wall of dinoflagellates contains cellulose. There are special features of dinoflagellates such as the ability for bioluminescence and the ability to produce neurotoxins. Dinoflagellates can result in algal blooms when present in high numbers. This will lead to the contamination of the fish living in these marine environments. Hence, as a result, it may pose a threat to human populations who consume these contaminated fish. There are many species of dinoflagellates such as Ceratium, Peridinium and Dinophysis, etc.
What are the Similarities Between Diatoms and Dinoflagellates?
- Diatoms and Dinoflagellates are single-celled, eukaryotic algae.
- Both reside in marine environments.
- They are types of phytoplankton.
- Both contain chlorophyll and other pigments.
- They do photosynthesis to produce foods.
- Diatoms and Dinoflagellates generate oxygen.
- They are able to indicate the water quality.
What is the Difference Between Diatoms and Dinoflagellates?
The two most common phytoplankton found in seawater are diatoms and dinoflagellates. Diatoms have a cell wall that comprises silica while dinoflagellates have a cell wall that comprises cellulose. This is the key difference between diatoms and dinoflagellates. Furthermore, another difference between diatoms and dinoflagellates is that though the diatoms and dinoflagellates are able to photosynthesize and generate oxygen, the dinoflagellates can produce neurotoxins and have the ability of bioluminescence, but that is not present in diatoms.
The below infographic presents a side by side comparison to make the difference between diatoms and dinoflagellates more clear.
Summary – Diatoms vs Dinoflagellates
Diatoms and dinoflagellates are types of phytoplankton. They are single-celled algae. Diatoms have a theca covering the cell, which acts as an external cell wall. Dinoflagellates have a bi-flagellated structure. Both are capable of performing photosynthesis and possess pigments. Dinoflagellates have special features such as the ability to produce neurotoxins and ability for bioluminescence. This is the difference between diatoms and dinoflagellates.
1.“Lab11_1 Planktonic Diatoms and Dinoflagellates.” Untitled Document. Available here