What is the Difference Between Neuston and Pleuston

The main difference between neuston and pleuston is that neuston refers to organisms that float on the top of the water (epineuston) or live right under the surface (hyponeuston) whereas pleuston refers to organisms that live in the thin surface layer existing at the air-water interface of a body of water. Furthermore, the floating neuston includes microscopic organisms that rely on the surface tension, while pleuston is a macroscopic organism that floats by buoyancy.  

Neuston and pleuston are two terms used in marine biology to describe different types of organisms that live near the surface of a water body. Generally, these organisms are exposed to harsh environmental conditions such as high-temperature variations, high-light variations, including UV irradiation, marine, and aerial predators, etc. 

Key Areas Covered 

1. Neuston
     – Definition, Characteristics, Examples
2. Pleuston
     – Definition, Characteristics, Examples
3. What are the Similarities Between Neuston and Pleuston
     – Outline of Common Features
4. What is the Difference Between Neuston and Pleuston
     – Comparison of Key Differences  

Key Terms 

Buoyancy, Epineuston, Hyponeuston, Neuston, Pleuston

Neuston – Definition, Characteristics, Examples 

Neuston refers to organisms that live near the surface of the water. Generally, these organisms live in the surface film of lakes, oceans, and slow-moving portions of streams. The two main forms of neuston include epineuston and hyponeuston. Epineuston refers to organisms that live above the water surface but, immersed in the water. In contrast, hyponeuston refers to organisms that live just underneath the water surface. Moreover, increasing turbulence decreases the density of neustonic organisms. As a result, they are confined to lentic habitats or some lateral components of the riverscape. 

Figure 1: Wolffia arrhiza (very small), Lemna minor (medium), Spirodela polyrhiza (large) Floating on the Water Surface

Furthermore, a thin bacterial film primarily supports the neustonic food web on the surface of the water. Besides, the concentration of phytoplankton and allochthonous inputs from trapped terrestrial and aquatic organisms are also present. Protozoa, floating macrophytes, algae, and bacteria are among the common assemblage of the neustonic food web. Also, large neustonic species include springtails (Collembola), some arachnids (mites and water spiders), and various families of true bugs (e.g., water striders, Gerridae). Moreover, these organisms move over the water surface, and are especially, vulnerable to predation from both aquatic and terrestrial predators. Besides, they need to adapt to the higher ultraviolet radiation present near the water surface.  

Pleuston – Definition, Characteristics, Examples 

‘Pleuston’ is generally an old term or a term that describes the subset of macroscopic epineustonic organisms. Thus, pleuston refers to macroscopic organisms that live on the surface of the water by floating. Basically, there are two types of epineustonic organisms floating on the water surface: microscopic and macroscopic. Microscopic epineustonic organisms float on the water surface with the help of the surface tension of water.

Figure 2: Pleustonic Portuguese Man-O-War (Physalia physalis)

On the other hand, macroscopic epinuestonic organisms float on the water surface by buoyancy. Furthermore, pleustonic organisms include macroscopic cyanobacteria, gastropods, ferns such as Azolla and Salvinia, seed plants  Lemna, Wolffia, and Pistia, flying fish, whirligig beetle, spiders such as fishing spider and diving bell spider, water striders, etc. 

Similarities Between Neuston and Pleuston  

• Neuston and pleuston are two terms used in marine biology to describe organisms that live near the surface of the water.  
• These organisms are exposed to harsh environmental conditions such as high-temperature variations, high light variations including UV  irradiation, marine, and aerial predators, etc.  
• Moreover,  the color of these organisms is mainly transparent or blue-violet,  helping to defend from predators.  
• The best method for sampling these organisms is to use a neuston net. 

Difference Between Neuston and Pleuston 

Definition 

Neuston refers to the small aquatic organisms inhabiting the surface layer or moving on the surface film, while pleuston refers to the organisms that live at the air-water interface. 

Significance 

Neuston refers to organisms that float on the top of the water (epineuston) or live right under the surface (hyponeuston), while pleuston refers to organisms that live in the thin surface layer existing at the air-water interface of a body of water. 

Correlation 

Moreover, neusten is the superset of organisms that live near the surface of a water body, while pleuston is a subset of neusten. 

Mode of Floating

The floating neuston includes microscopic organisms that rely on the surface tension, while pleuston is a macroscopic organism that floats by buoyancy.  

Examples 

Some examples of neuston include flying fish, whirligig beetle, fishing spider, springtails, water striders, etc. while some examples of pleuston are some cyanobacteria, gastropods, Salvinia, etc. 

Conclusion 

Neuston is an organism that lives near the surface of the water. Generally, there are two types of neuston: epineuston that floats on top of the water, and hyponeuston that live right under the surface of the water. Moreover, there are two types of epineuston; microscopic and macroscopic. Epineuston, which is microscopic, floats on water by relying on surface tension. And, epineuston, which is macroscopic, floats on water by buoyancy. Besides, the macroscopic epineuston is known as pleuston. Thus, in summary, the main difference between neuston and pleuston is their mode of living near the water surface. 

References:

1. “Neuston.” Neuston – an Overview | ScienceDirect Topics, Available Here.
2. “Pleuston.” Wikipedia, Wikimedia Foundation, 12 Sept. 2019, Available Here.

Image Courtesy:

1. “Wolffia-Spirodela” By Christian Fischer (CC BY-SA 3.0) via Commons Wikimedia   
2. “Portuguese Man-O-War (Physalia physalis)” By Image courtesy of Islands in the Sea 2002, NOAA/OER. – U.S. Department of Commerce, National Oceanic and Atmospheric Administration (Public Domain) via Commons Wikimedia