A plankton net is equipment used for collecting samples of

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

in standing bodies of water. It consists of a towing line and bridles,

nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from pe ...

mesh A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands. Types * A plastic mesh may be extruded, oriented, exp ...

net, and a cod end. Plankton nets are considered one of the oldest, simplest and least expensive methods of sampling plankton. The plankton net can be used for both vertical and horizontal sampling. It allows researchers to analyse plankton both

quantitatively Quantitative research is a research strategy that focuses on quantifying the collection and analysis of data. It is formed from a deductive approach where emphasis is placed on the testing of theory, shaped by empiricist and positivist philoso ...

(cell density, cell colony or biomass) and qualitatively (e.g. Chlorophyll-a as a primary production of phytoplankton) in water samples from the environment. A simple plankton net

An outlet valve with bucket of the plankton net

Components

; Towing line and bridle : The towing line and bridle is the upper part of a plankton net and used to hold it. The towing lines connected to the triangle bridles are made of

rope A rope is a group of yarns, plies, fibres, or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similar ...

and can be adjust to a level suitable for the user. ; Nylon mesh net : The nylon mesh

net Net or net may refer to: Mathematics and physics * Net (mathematics), a filter-like topological generalization of a sequence * Net, a linear system of divisors of dimension 2 * Net (polyhedron), an arrangement of polygons that can be folded up ...

is the middle part of the plankton net and is used to

filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

the plankton in the water sample in accordance with the size of the mesh. In addition, its

funnel A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening. Funnels are usually made of stainless steel, aluminium, glass, or plastic. The material used in its construct ...

shape makes it possible to effectively capture plankton of various sizes. There are various mesh sizes for nets, depending on the target

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

to be collected and the condition of the

water body A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...

. The narrower the mesh size, the smaller the plankton in the water sample. For example, in order to obtain small

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...

measuring 50 to 1500 μm, a net mesh size between 25 and 50 μm

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

should be selected, which is sufficient to effectively

only the target

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

. However, in a

eutrophic Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytoplan ...

water condition, a plankton net with a mesh larger than 100 μm should be chosen to avoid clogging the net. ; Cod end : The cod end is located in the lower part of the plankton net at the end of the funnel. It has a collecting

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

and a valve for opening and closing it.

Use

One common method for collecting a

sample is to tow the net horizontally using a low-speed boat. Before collecting the plankton, the net should be rinsed with the sample water. The user should ensure that the cod end is completely closed by turning the valve into a vertical position. Then the plankton net is then lowered horizontal to the water surface at the side of the slowly moving

boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...

. Sampling is done for 1.5 minutes. After this time, the plankton sample is collected in a sample bottle by opening the cod end above it by turning the valve horizontally. When the sample is collected it can be analyzed using a

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...

to identify the type of

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 ...

or phytoplankton, or a cell count can be undertaken to determine the plankton cell density of the water source.

History

John Vaughan Thompson John Vaughan Thompson FLS (19 November 1779 – 21 January 1847) was a British military surgeon, marine biologist, zoologist, botanist, and published naturalist. Early years John Vaughan Thompson was born in British controlled Brooklyn on Lon ...

developed a plankton net during his return voyage from Mauritius, which reached the UK in 1816. Impressed by marine bioluminescence in small crustacea he later named ''

Sapphirina ''Sapphirina'', whose members are commonly known as sea sapphires, is a genus of parasitic copepods in the family Sapphirinidae. Description Various species of male ''Sapphirina'' shine in different hues, from bright gold to deep blue. This i ...

'', he felt "under great obligations to this beautiful little animal, which by its splendid appearance in the water induced me to commence the use of a muslin hoop-net, which when it failed to procure me a specimen, brought up such a profusion of other marine animals altogether invisible while in the sea, as to induce a continued use of it on every favourable opportunity." He published his research in a series of six memoirs from 1828 to 1834. The second recorded use of a plankton net was by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...

on 10 January 1832, during the ''Beagle'' survey voyage. His diary included a sketch of the net, which appears to have been based on a trawl net described by John Coldstream in a letter to Darwin. It is possible that Thompson's idea had earlier been drawn to Darwin's attention by

Robert Edmond Grant Robert Edmond Grant MD FRCPEd FRS FRSE FZS FGS (11 November 1793 – 23 August 1874) was a British anatomist and zoologist. Life Grant was born at Argyll Square in Edinburgh (demolished to create Chambers Street), the son of Alexander Gra ...

in Edinburgh. Darwin describes this "contrivance" as "a bag four feet deep, made of bunting, & attached to semicircular bow this by lines is kept upright, & dragged behind the vessel". The next day he remarked that "The number of animals that the net collects is very great & fully explains the manner so many animals of a large size live so far from land. — Many of these creatures so low in the scale of nature are most exquisite in their forms & rich colours. — It creates a feeling of wonder that so much beauty should be apparently created for such little purpose."

References

{{Reflist Microbiology equipment Planktology

Components

Use

History

See also

References