Neuston, also known as pleuston, are organisms that live at the surface of the ocean or an estuary, or at the surface of a lake, river or pond. Neuston can live on top of the water surface or may be attached to the underside of the water surface. They may also exist in the surface microlayer that forms between the top side and the underside. Neuston have been defined as "organisms living at the air/water interface of freshwater, estuarine, and marine habitats or referring to the biota on or directly below the water’s surface layer." The word neuston comes from the Greek ''neustos'', meaning "swimming" + -on (as in plankton). This term first appears in the biological literature in 1917. The alternative term pleuston comes from the Greek ''plein'', meaning "to sail or float". The first known use of this word was in 1909, before the first known use of neuston. In the past various authors have attempted distinctions between neuston and pleuston, but these distinctions have not been widely adopted. As of 2021, the two terms are usually used somewhat interchangeably, and neuston is used more often than pleuston.

Overview

Portuguese Man-O-War (Physalia physalis)

The neuston of the surface layer is one of the lesser known aquatic ecological groups. The term was first used in 1917 by Naumann to describe species associated with the surface layer of freshwater habitats.Naumann, E. (1917) "Beiträge zur Kenntnis des Teichnannoplanktons. II. Über das Neuston des Süsswassers", ''Biologisches Zentralblatt'', 37: 98–106. Later in 1971, Zaitsev identified neuston composition in marine waters.Zaitsev, Y. P. (1971) "Marine Neustonology". ''National Marine Fisheries Service'', ''NOAA'' and ''NSF'', Washington DC. These populations would include microscopic species, plus various plant and animal taxa, such as

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. ...

and

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

, living in this region. In 2002, Gladyshev further characterised the major physical and chemical dynamics of the surface layer influencing the composition and relationships with various neustonic populations" The neustonic community structure is conditioned by sunlight and an array of

endogenous Endogenous substances and processes are those that originate from within a living system such as an organism, tissue, or cell. In contrast, exogenous substances and processes are those that originate from outside of an organism. For example, ...

(organic matter, respiratory, photosynthetic, decompositional processes) and

exogenous In a variety of contexts, exogeny or exogeneity () is the fact of an action or object originating externally. It contrasts with endogeneity or endogeny, the fact of being influenced within a system. Economics In an economic model, an exogen ...

(atmospheric deposition, inorganic matter, winds, wave action, precipitation, UV radiation, oceanic currents, surface temperature) variables and processes affecting nutrient inputs and recycling. Furthermore, the neuston provides a food source to the

migrating from deeper layers to the surface,Hempel, G. and Weikert, H. (1972) "The neuston of the subtropical and boreal North-eastern Atlantic Ocean. A review". ''Marine Biology'', 13(1): 70–88. as well as to

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envir ...

s roaming over the oceans. For these reasons, the neustonic community is believed to play a critical role on the structure and function of

marine food web Compared to terrestrial environments, marine environments have biomass pyramids which are inverted at the base. In particular, the biomass of consumers (copepods, krill, shrimp, forage fish) is larger than the biomass of primary producers. Th ...

s. Yet, research on neuston communities to date focused predominantly on geographically-limited regions of the ocean or coastal areas. Consequently, neuston complexity is still poorly understood as studies on the community structure and the taxonomical composition of organisms inhabiting this ecological niche remain few, and global scale analyses are yet lacking.

Types

There are different ways neuston can be categorised. Kennish divides them by their physical position into two groups: * ''epineuston'': organisms living on the water’s surface * ''hyponeuston'': organisms within a region of specified depth directly below the surface layer To this can be added the organisms living in the microlayer at the interface between air and water: * ''microlayer neuston'': organisms (microorganisms) living in the surface microlayer sandwiched between the upper and under surface. Marshall and Burchardt divide neuston into three ecological categories: * ''euneuston'': organisms with maximum abundance in the vicinity of the surface on which they reside day and night * ''facultative neuston'': organisms concentrating at the surface only during certain hours of the day, usually during darkness * ''pseudoneuston'': organisms with maximum concentrations at deeper layers but reaching the surface layer at least during certain hours.

Freshwater neuston

Freshwater neuston, organisms living at lake or pond surfaces or slow moving parts of rivers and streams, include

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s (see whirligig beetle),

protozoans Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Hist ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

and

spiders Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species di ...

(see fishing spider and diving bell spider).

Springtail Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called ...

s in the genera '' Podura'' and ''

Sminthurides ''Sminthurides'' is a genus of globular springtails in the family Sminthurididae. There are more than 30 described species in ''Sminthurides''. Species These 32 species belong to the genus ''Sminthurides'': * '' Sminthurides annulicornis'' Axe ...

'' are almost exclusively neustonic, while '' Hypogastrura'' species often aggregate on pond surfaces. Water striders such as '' Gerris'' are common examples of insects that support their weight on water's

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) t ...

. File:Gyrinus natator.JPG, Whirligig '' Gyrinus natator'' File:Courtship ritual of Sminthurides aquaticus.webm, '' Sminthurides aquaticus'' File:Water spider 2.jpg, Water spider File:Gerris by webrunner.JPG, Waterstrider '' Gerris commun'' File:Wolffia-Spirodela.jpg,

Duckweed Lemnoideae is a subfamily of flowering aquatic plants, known as duckweeds, water lentils, or water lenses. They float on or just beneath the surface of still or slow-moving bodies of fresh water and wetlands. Also known as bayroot, they arose f ...

on a pond
By size: greater duckweed, lesser duckweed and rootless dwarf duckweed

Floods

There are different terrestrial environmental factors such as flood pulses and droughts, and these environmental factors affect species such as neuston, whether the effects lead to more or less variations in the species. When flood pulses (an abiotic factor) occur, connectivity between different aquatic environments occur. Species that live in environments with irregular flood patterns tend to have more variations, or even decrease species and variations; similar idea to what happens when droughts occur.

Marine neuston

The marine neuston, organisms living at the ocean surface, are one of the least studied planktonic groups. Neuston occupies a restricted ecological niche and is affected by a wide range of endogenous and exogenous processes while also being a food source to zooplankton and fish migrating from the deep layers and seabirds. CC-BY icon

Material was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
The neustonic animals form a subset of the zooplankton community, which plays a pivotal role in the functioning of marine ecosystems. Zooplankton are partially responsible for the active

energy flux Energy flux is the rate of transfer of energy through a surface. The quantity is defined in two different ways, depending on the context: # Total rate of energy transfer (not per unit area); SI units: W = J⋅s−1. # Specific rate of energy transf ...

between superficial and deep layers of the ocean. Zooplankton species composition, biomass, and secondary production influence a wide range of trophic levels in marine communities, as they constitute a link between primary production and secondary consumers.

Copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have ...

s constitute the most abundant zooplankton taxon in terms of

biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...

and diversity worldwide. Consequently changes in their community composition can impact the

biogeochemical cycle A biogeochemical cycle (or more generally a cycle of matter) is the pathway by which a chemical substance cycles (is turned over or moves through) the biotic and the abiotic compartments of Earth. The biotic compartment is the biosphere and th ...

s and might be indicative of climate variability impacts on ecosystem functioning. File:Portuguese man-o-war Physalia sp.png, Portuguese man-o-war ''Physalia'' sp. File:By-the-wind sailor Velella sp.png, By-the-wind sailor '' Velella'' sp. File:Blue button Porpita sp.png, Blue button '' Porpita'' sp. File:Flying fish from the family Exocoetidae.png, Flying fish from the family

Exocoetidae The Exocoetidae are a family of marine fish in the order Beloniformes class Actinopterygii, known colloquially as flying fish or flying cod. About 64 species are grouped in seven to nine genera. While they cannot fly in the same way a bird do ...

File:Buoy barnacle Dosima fascicularis.png, Buoy barnacle ''Dosima fascicularis'' File:Blue sea dragons Glaucus sp.png, Blue sea dragons '' Glaucus'' sp. Historically, zooplankton assemblages research has focused mainly on taxonomic studies and those related to community structure. However, recently, research has veered toward an alternative trait-based approach, providing a perspective more focused on groups of species with analogous functional traits. This allows individuals to be classified into types characterized by the presence/absence of certain

alleles An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chrom ...

of a

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

, into size classes, ecological guilds, or

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

s (FGs). Functional traits are

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...

s affecting organism fitness, growth, survival, and reproductive ability. These are regulated by the expression of genes within species, and the expression of traits regulate, in turn, the species fitness under contrasting biotic and abiotic circumstances. Moreover, a specific functional trait can also develop from the interactions between other traits and environmental conditions, leading to a given trait grouping being favoured under certain conditions. Zooplankton traits can be classified in accordance to ecological functions – feeding, growth, reproduction, survival, and other characteristics such as morphology,

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemic ...

, behaviour, or life history. Particularly, feeding strategies and trophic groups are relevant to establish feeding efficiency and associated predation risk. Additionally, they facilitate the understanding of ecosystem services associated with zooplankton, such as the distribution of fisheries or biogeochemical cycling while also allowing the positioning of zooplankton taxa in the food web. File:Paper nautilus Aurgonaut sp.png,

Paper nautilus The argonauts (genus ''Argonauta'', the only extant genus in the family Argonautidae) are a group of pelagic octopuses. They are also called paper nautili, referring to the paper-thin eggcase that females secrete. This structure lacks the gas-f ...

''Aurgonaut'' sp. File:Sargassum sp. seaweed.png, ''

Sargassum ''Sargassum'' is a genus of brown (class Phaeophyceae) macroalgae ( seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral ...

'' sp. seaweed File:Hippolytidae shrimp.png, Hippolytidae shrimp File:Marine snail Recluzia sp.png, Marine snail '' Recluzia'' sp. File:Violet snail Janthina sp.png, Violet snail ''

Janthina ''Janthina'' is a genus of small to medium-sized pelagic or planktonic sea snails, marine gastropod molluscs in the family Epitoniidae.Gofas, S. (2011). Janthina Röding, 1798. Accessed through: World Register of Marine Species at http://www.ma ...

'' sp. File:Floating anemone Actinecta sp.png, Floating

anemone ''Anemone'' () is a genus of flowering plants in the buttercup family Ranunculaceae. Plants of the genus are commonly called windflowers. They are native to the temperate and subtropical regions of all continents except Australia, New Zealand an ...

''Actinecta'' sp. Coral-treaders are a genus of quite rare wingless marine bugs known only from coral reefs in the Indo-Pacific region. During low tide they move over water surfaces around coral atolls and reefs similar to the more familiar water-striders, staying submerged in reef crevices during high tide.

References

External links

* {{aquatic organisms Aquatic ecology Ecology terminology