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Neuston vs pleuston

Neuston vs pleuston



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I was recently reading about the wonderful chondrophores, and came across the terms "neuston" and "pleuston". According to Wikipedia, "neuston" are "the organisms that float on the top of water… or live right under the surface", while "pleuston" are "the organisms that live in the thin surface layer existing at the air-water interface of a body of water".

How are these terms used in the scientific literature? Are pleuston considered a subset of neuston? Some examples of organisms in one category but not the other would be helpful.


The Ocean Cleanup and the Neuston

On January 22, an opinion piece was published in The Atlantic, originally titled “The Ocean Cleanup Project Could Destroy the Neuston.” Since preventing the destruction of ocean ecosystems is the main purpose of the cleanup effort, any potentially significant environmental side-effect is taken very seriously by our team. This post will hopefully shed more light on the neuston and how our system could potentially interact with these organisms.

At The Ocean Cleanup we are on a mission to rid the world’s oceans of plastic. We made this our mission because we believe that the health of our oceans is essential for all life on Earth to prosper. According to the World Economic Forum, with the current trajectory, plastic could outweigh fish in the oceans by 2050. To us, that future is unacceptable.

Our first focus is to clean up the so-called ocean garbage patches of the world’s ocean surface, these are the five areas where plastic accumulates. This means that, even if no more plastic enters the oceans, the plastic trapped in the currents of these accumulation zones will continue to cause harm, as it chokes or entangles countless marine mammals, sea turtles, fish and all other marine life, for decades and possibly even centuries to come. On top of this, ocean plastic carries toxic chemicals, which get carried through the food chain, ultimately making their way into the human diet. This is why we must clean up these ocean garbage patches.

Of course, this mission will not be easy. Designing a cleanup system that can last many years in one of the most challenging environments on this planet, while safely and efficiently collecting plastic, is a grand engineering challenge.
The trickiest part, as is inherent to innovation of this caliber, is that many of the essential aspects of our technology must be tested in real life conditions (i.e. in the ocean). Scale model testing or computer simulations will only teach us so much. Therefore, we follow an iterative development path, through which we learn by doing that includes the testing of our first full-scale cleanup system, which is currently under revision for upgrades, ahead of re-launch.

It is also the reason why we actively welcome and appreciate feedback. With a mission of such complexity, we can use all the help we can get.

After learning of The Atlantic piece, we took this as a potential opportunity to incorporate more feedback. The central thesis to the claims made in the column can be summarized as follows:

  1. The Environmental Impact Assessment (EIA) produced for The Ocean Cleanup didn’t consider the neuston community.
  2. Cleaning up 90% of plastic from the ocean will kill 90% of the oceanic neuston, which will devastate this ecosystem.
  3. This is especially worrying as we don’t have a solid understanding of this ecosystem yet.

Before we delve into this feedback, it might be helpful to provide some background on Environmental Impact Assessments and the neuston.

WHAT IS AN ENVIRONMENTAL IMPACT ASSESSMENT?

An EIA is a decision support tool, providing information on the likelihood of an impact on the local environment in connection to a specific project or activity. Its purpose is to determine the potential environmental, social, and health-related effects (if applicable) of a project so that those who develop and authorize the project can be informed in their decision-making, while it also indicates how these potential impacts can be reduced or mitigated.

Because of the novelty of the cleanup system and the international location of its deployment, The Ocean Cleanup was not legally required to conduct an EIA for System 001. However, as we always want to move forward in our cleanup operation transparently and with the best available knowledge, we chose to voluntarily initiate one.

You can read more about our EIA from our update in July after we had received the conclusions from the independent agency who conducted the assessment.

WHAT IS THE NEUSTON?

Neuston is a term used to describe the organisms that spend a fraction or the entirety of their life on the water surface (epineuston) or right under it (hyponeuston). There is some debate on how to accurately define the group, but for the sake of consistency, we refer to the phrasing from The Atlantic column: “Organisms that live exclusively by floating at the surface of the water are called pleuston, while neuston is a broader term, referring generally to the sea-surface ecosystem”.

One of the most common species of the neuston community is Velella velella, an organism which consists of a colony of polyps that lives throughout the world’s oceans. You may be familiar with them as they frequently strand on beaches across the world.

Velella Beached, Photography by Ingrid Taylar (via Flickr).

Welcoming feedback

The EIA was produced by a group of independent scientists and is the result of a comprehensive analysis of available scientific literature. However, we realize that scientists are humans too, and that there can always be room for improvement. This is why, when the EIA was released on our website, we also opened up the email address [email protected], specifically with the purpose of enabling the wider public – and scientific community – to provide feedback on the EIA to its authors.

Before The Atlantic column was published, we had been in contact with the author of the piece, Dr. Rebecca Helm, following a series of her tweets, in which she expressed her concerns about the impact that our system would have on the neuston community. We proactively reached out via email, inviting her to send a more detailed view of her concerns and some supporting evidence, thus opening the door for a scientific discussion on this topic between peers.
After initial contact was made, a few emails between Dr. Helm and the authors of the EIA were exchanged in the second week of January, during which she shared three peer-reviewed articles with general information on neuston. One article was from 1956 and written in Russian unfortunately, a translation was unavailable (but we are working on it). The other articles, both written in English, were from 1962 and ‘74. These papers referenced a few species within the neuston community that were not mentioned in the EIA, including Janthina, Glaucus and Minyas.

However, these papers did not provide any quantitative data of these neuston. This type of information is required for use in an EIA to determine to what degree a project affects certain species therefore, the articles could not be used to improve the EIA prepared for System 001.

DID THE ENVIRONMENTAL IMPACT ASSESSMENT OMIT THE NEUSTON?

The Atlantic piece contains claims that the neuston was omitted from the EIA. However, this is incorrect species that are part of the neuston ecosystem in the North Pacific have been considered in the EIA, in section 4.3.1.2: Gelatinous Macrozooplankton. In Table 4-2 of this section, all species that have previously been observed near the deployment site of our cleanup system are referenced, including by-the-wind sailors (Vellela vellela), blue buttons (Porpita porpita) and the Pacific Portuguese man o’ wars (Physalia utriculus).

A screenshot of Table 4-2 from the EIA, listing macro-zooplankton known to reside also in the Great Pacific Garbage Patch.

COULD A CLEANUP OPERATION DESTROY THE NEUSTON?

There are strong assertions in The Atlantic column, such as “the project could rob the world of an entire ecosystem that we don’t understand and may never get back” and that, because of our work to rid the oceans of plastic, all of the neuston are “in peril”. These claims are based on the belief that “cleaning up 90 percent of the plastic using the current cleanup method means potentially destroying 90 percent of the neuston” and that “neuston and plastic co-occur: They’re in the exact same spots.”

If there is any evidence that would substantiate this level of impact, we invite it to be shared with us. That being said, neither the literature review conducted for the EIA nor the additional articles that were provided to us contained any data in support of these statements.
For what we know, most of the species that comprise the neuston are ubiquitous and distributed throughout the tropical and temperate zones of all the world’s oceans, an area that measures more than 300,000,000 km 2 about 30x the size of the USA.

Despite this understanding, a drawn map from a 1968 study is referenced in the piece, showing the neuston subdivided into seven distinct zones in the Pacific Ocean, spanning from Alaska all the way to New Zealand one of which is depicted as directly overlapping with the area where the plastic accumulates in the North Pacific Ocean.
Aside from the fact that the validity of using a single, 51-year-old source could be questioned, it might be important to note that the author himself states on page 414 of the article that “it can be considered only as a preliminary chart”.

But assuming this map provides an accurate view of distinct neuston ecosystems, the surface area identified as “Neuston ecosystem 2” measures about 50 million km 2 , while the Great Pacific Garbage Patch is ‘only’ 1.6 million km 2 or 3% of the entire neuston ecosystem 2. The deployment area of our cleanup operations will likely be limited to the area of highest concentration, which measures less than 500.000 km 2 – 1% of this zone’s size.

Size comparison of “Neuston ecosystem 2” and the deployment area of our ocean cleanup system.

Considering the Great Pacific Garbage Patch covers only a small percentage of one of these seven zones, it is clear that neuston and plastic are not equally distributed.

Still, we continued to seek validation for these statements using the shared literature, but, rather than confirmation, we found further support for the opposite. An excerpt from one of the provided articles reads:

Source: The Animal World at the Sea Surface, and its Habits.

In other words, some species within the neuston have developed survival strategies, such as a high reproduction rate, to adapt to losses. Whereas, plastic, on the other hand, does not reproduce the plastic removed from the patch, will not return to the patch. This undermines the idea that a 90% removal of plastic equates to a similar reduction in the neuston.

Professor Gerhard J. Herndl of the Vienna University , whose research group has studied the neuston in the North Atlantic Gyre, an ecosystem very similar to the Great Pacific Garbage Patch, confirmed the following:

“Most plankton and neuston organisms are adapted to high loss rates as they are washed ashore with every wave hitting the shores. Open ocean neuston are less subjected to be washed ashore but there are other stressors such as high turbulence fragmenting these fragile organisms during storm events. Compared to these stressors, the loss of neuston organisms occurring if they are trapped by The Ocean Cleanup’s system is extremely small considering the area covered by the cleanup and the dimensions of the North Pacific gyre. The recruitment of these neuston organisms will definitely compensate by far these losses.”

FURTHERING THE UNDERSTANDING OF THE ECOSYSTEM

The Atlantic column states that “the fact that we don’t have a solid understanding of the neuston ecosystem is even more worrying: we will have very little “before” data to compare The Ocean Cleanup’s impact against”. The scientific understanding of the abundance and population dynamics of neuston species is, in some cases, indeed limited and that this inherently causes uncertainty. However, this is exactly the basis on which our testing and monitoring strategy is built. Rather than deploying the whole fleet of cleanup systems at once, we started with just one system , which not only allows us to optimize the technology before scaling up, but also gives us the opportunity to study the interaction between the system and the local environment.

Beyond the EIA, the agency that conducted the EIA developed an Environmental Management Plan (EMP) which is used during our offshore operations. The EMP is a guideline for monitoring and mitigating any potential impact on the environment around System 001. And in addition to the EMP, for the four months of System 001’s maiden voyage, we have had an on-site monitoring vessel on a near-permanent basis, and one of its main tasks has been to conduct environmental observations. Monitoring the system is fundamental to our testing plan, as it allows us to verify the safety of the cleanup technology, while increasing the available general knowledge of the ecology of the Great Pacific Garbage Patch.

Environmental data collection using a remote vessel during the System 001 offshore mission.

In the 115 days of operation, our marine biologists and independent environmental observers onboard the monitoring vessels have conducted 737+ hours of observational surveys for protected species and marine life in general – including neuston – surrounding the system. More than 150 low-altitude flights with drones equipped with live streaming cameras were performed. There were also 56 inspections with a support vessel and 49 days of remote vessel data collection carried out during this time.

R ather than a threat, The Ocean Cleanup’s project is providing an unprecedented opportunity to collect data and further the understanding of the Eastern North Pacific Ocean, including the neuston ecosystem. We look forward to sharing these observations and data with the wider scientific community.

CONCLUSION

We would like to thank Dr. Rebecca Helm for taking the time to share her concerns and for accepting a dialogue with us. The health of the oceans is clearly a matter that all of us care about and want to collectively solve.

However, based on the available data, we have not found any evidence that supports the idea that the neuston are at risk because of our efforts in developing technology that can rid the oceans of plastic.

Should you have access to any sources that suggest any negative environmental impacts of our system that we have not considered, or if you have any other concerns on the EIA, please share them with us through [email protected]
On the other hand, zooming out to the bigger picture, there is strong evidence that the hundreds of thousands of tons of toxic plastic that is floating in the ocean is damaging ecosystems, which, ironically, may include the neuston.

The threat of extinction is real, and that is for the 117 endangered species that are currently being harmed by plastic pollution in the oceans. A cleanup, done responsibly, can help change that.

  1. The article’s title has since changed to “How Plastic Cleanup Threatens the Ocean’s Living Islands”. Although, not naming the article “Neuston, we have a problem” truly is a missed opportunity. ↩
  2. From the report “The New Plastics Economy” produced by WEF, the Ellen McArthur Foundation and McKinsey & Company in 2017. ↩
  3. Of course, preventing further plastic pollution from reaching the oceans is critical, and will require a combination of material innovation, legislation and infrastructural improvements and innovation. However, none of those things provide a solution to the legacy pollution that is already floating in the ocean today. ↩
  4. During our reconnaissance expeditions in the Great Pacific Garbage Patch in 2015, 1.2 million pieces of plastic were collected for research. Of those identifiable, most stemmed from the 70s, 80s and 90s (while still in recognizable shape), which is strong evidence that the plastic in the patch can persist for long periods of time. Furthermore, modeling studies show that low windage debris does not beach but ends up in the ocean garbage patches (e.g. Maximenko et al. 2018). ↩
  5. https://www.scientificamerican.com/article/from-fish-to-humans-a-microplastic-invasion-may-be-taking-a-toll/↩
  6. Take, for example, the interaction between plastic and the cleanup system. Extensive CFD simulations and scale model tests have been performed, but the highly nonlinear behavior of the screen and surface tension effects inherently causes a higher uncertainty behind the results of such experiments. The only way to get certainty is to test the technology at full scale. ↩
  7. Marshall, H., & Burchardt, L. (2005). Neuston: Its definition with a historical review regarding its concept and community structure. Archiv Für Hydrobiologie, 164(4), 429-448. ↩
  8. The Conversation, 3 September 2014 by Dr. Cathy Lucas. ↩
  9. Evans, F., 1986. Velella velella (L), the ‘by-the-wind-sailor’ in the North Pacific Ocean in 1985. Mar. Obs. 56: 196–200. ↩
  10. The Animal World at the Sea Surface, and its Habits (Weikert, 1974) Factors affecting the distribution of Velella (Chondrophora) (Mackie, 1962) Pleuston of the western part of the Pacific Ocean (Savilov, 1956). ↩
  11. See EIA section 5.1 for methodology. In short: an EIA must consider impacts beyond what may occur simply by the presence of an organism. ↩
  12. Holdway, P., & Maddock, L. (1983). A comparative survey of neuston: geographical and temporal distribution patterns. Marine Biology, 76(3), 263-270. https://doi.org/10.1007/BF00393027 Liparoto, A., Mancinelli, G., & Belmonte, G. (2017). Spatial variation in biodiversity patterns of neuston in the Western Mediterranean and Southern Adriatic Seas. Journal Of Sea Research, 129, 12-21. doi: 10.1016/j.seares.2017.08.007 ↩
  13. See figure 73, page 414 (link) ↩
  14. The Animal World at the Sea Surface, and its Habitat, Weikert, H. Universitas Jan 1, 1974 16, 1 ProQuest pg. 31 ↩
  15. Herndl is Vice-Dean of the Faculty of Life Sciences, Chair of Aquatic Biology and Head of the Dept. Limnology and Oceanography. He is also a member of The Ocean Cleanup’s Scientific Advisory Board ↩
  16. It is also important to clarify that the concerns in The Atlantic column primarily relate to the deployment of a fleet of systems. But, as stated at the beginning of the EIA, this assessment has been produced for only one system, System 001. Before we scale-up, a new EIA will be performed for a fleet of systems. This EIA will also have additional information from at-sea observations of the neuston community that our scientific team has performed during System 001 deployment. ↩
  17. List of monitoring/mitigation activities suggested by the EIA and implemented during offshore deployment: conduct watches for marine mammals, turtles, fish, sharks and sea birds conduct Passive Acoustic Monitoring (PAM) control of bycatch before and during plastic extraction activity control and study of fish aggregation near and far from the barrier. ↩
  18. As always, the results of these monitoring campaigns will be published (open access) once available. ↩
  19. According to the initial observations during the first deployment of System 001, no measurable or evident impacts on the ocean environment (including of the neuston) were registered a thorough report of these findings from our scientists and third-party observers will be released in the near future. ↩
  20. Besides an ADCP current profiler and a wave sensor, our autonomous research vessel is also fitted with underwater cameras and multiparameter environmental sensors that allow us to detect the possible presence of marine life for sustained periods. ↩
  21. Villarrubia-Gómez, P., Cornell, S., & Fabres, J. (2018). Marine plastic pollution as a planetary boundary threat – The drifting piece in the sustainability puzzle. Marine Policy, 96, 213-220. ↩
  22. Gall, S., & Thompson, R. (2015). The impact of debris on marine life. Marine Pollution Bulletin, 92(1-2), 170-179. ↩

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Functional Relationships of Freshwater Invertebrates

Neuston

The term neuston refers to the assemblage of organisms associated with the surface film of lakes, oceans, and slow-moving portions of streams. It generally includes species living just underneath the water surface (hyponeuston), individuals that are above but immersed in the water (epineuston), and taxa that travel over the surface on hydrophobic structures (superneuston or, more properly, a form of epineuston). This name is similar to, or a subset of the older name, pleuston (sometimes neuston is used in reference to the microscopic components of the more encompassing pleuston). The density of neustonic organisms decreases with increasing turbulence. Consequently, most neuston is confined to lentic habitats or some lateral components of the riverscape.

The neustonic food web is primarily supported by a thin bacterial film on the upper surface of the water, a concentration of phytoplankton near the surface, and allochthonous inputs from trapped terrestrial and aquatic organisms. Protozoa are common in this assemblage, which also includes bacteria, algae, and floating macrophytes ( Munster et al., 1998 Butler et al., 2007 ), but other typically planktonic taxa are rare (one exception is the cladoceran Scapholeberis). Neustonic organisms may be entirely aquatic or they may move over the water surface ( Krieger, 1992 ). The latter include springtails (Collembola), some arachnids (mites and water spiders), and various families of true bugs (e.g., water striders, Gerridae). Larger neustonic species are especially vulnerable to predation from both aquatic and terrestrial predators, and all species must be adapted to the higher ultraviolet radiation present near the water surface.


Pleuston and neuston: On the categories of organisms in the uppermost pelagial †

Contribution No. 865 from the Department of Oceanography, University of Washington. The preparation of the manuscript was supported by U. S. Atomic Energy Commission Contract No. AT(45-1)-2225 (ref. RLO-2225-T26-26). Drs. D. M. DAMKAER, D. F. WINTER, and especially D. P. HENRY made helpful comments on the manuscript.

Abstract

The development of the connotations attached to the terms pleuston, neuston, and some of their derivatives is outlined. In the marine literature, the term hyponeuston has presently two principal. quite different meanings: organisms attached from below to the surface film and largely supported by it, and organisms frequenting the upper decimeter of the sea. To reduce the ensuing confusion in the marine realm and to maintain uniformity of aquatic terminology, the term endopleuston is proposed as a replacement for the second, recently acquired meaning of hyponeuston. Another new term, exopleuston, refers to positively buoyant organisms with dry upper surfaces which, however, live principally underwater, in the habitat of the endopleuston. The pleustal is recognized as the habitat of these organisms. It may be useful to regard it as a category. of equal rank the epipelagial or bathypelagial.


O termo neusto (neuston), derivado do adxectivo grego νευστόν neuston, "o que nada", "nadador" (tamén "flotante"), foi introducido en 1917 polo limnólogo E. Naumann (1891–1934). [ 4 ]

Na definición orixinal non se tiñan en conta máis que os organismos en contacto coa tensión superficial da película da superficie e que se encontraban por riba ou por debaixo dela. Pero posteriormente o significado do termo ampliouse e diversificouse. [ 5 ] .

Denomínase epineusto aos organismos que viven na fase aérea (sobre a película de auga), e hiponeusto aos da fase acuosa (por debaixo dela). [ 2 ] [ 3 ]

O adxectivo para cualificar ao relacionado con neusto é neustónico. [ 6 ]

Esta categoría de organismos acuáticos foi dividida en varias subcategorías, [ 7 ] cuxas definicións poden variar segundo os autores e as disciplinas en particular, os usos a miúdo difiren entre a limnoloxía (augas doces) e a oceanografía.

A primeira subdivisión foi a antecitada, referida á posición dos organismos en relación á superficie da película: epineusto, os que viven por riba da superficie, e hiponeusto, referido a aqueles que ocupan a capa superficial do líquido elemento inmediatamente por debaixo da superficie. [ 7 ] O termo supraneusto, moito máis raro, utilízase frecuentemente como sinónimo de epineusto, en particular en hidrobioloxía pero entre os biólogos mariños, e especialmente os microbiólogos, pode referirse ás comunidades de microorganismos que viven na película superficial. [ 8 ] O seu antónimo é infraneusto.

Outra categoría importante é o pleusto ou pleuston, aínda que non hai unanimidade para a súa definición. O termo construíuse co radical pleust-, do grego τό ρλευστόν to pleuston, "navegante", "flotante". [ 9 ] No medio mariño aplícase case sempre aos seres vivos que flotan na superficie e cuxos desprazamentos son pasivos, é dicir, que se rexen polas correntes da auga ou polo vento. [ 10 ] Os animais acuáticos perfectamente adaptados a esta forma de vida teñen flotadores que poden superar a superficie e servir como unha vela, como ocorre na carabela portuguesa (Physalia physalis).

Mais para moitos limnólogos, o neusto non representaría máis que a fracción dos organismos de pequeno tamaño, incluso microscópicos, relacionados coa superficie, mentres que o pleusto correspondería aos organismos de gran tamaño. [ 11 ] Outra clasificación baseada no talle distingue o piconeusto, onde o tamaño pode ser inferior a 2 μm, do microneusto e do macroneusto, cuxos representante poden medir un metro ou máis. [ 12 ]

O neusto pode tamén categorizarse en función dos tipos de organismos que o compoñen. Pódese así falar de bacterioneusto, a fracción bacteriana do neuston, do fitotoneusto (a vexetal), ou do zooneusto (a dos animais) e mesmo do ictioneusto (a constituída só polos peixes).

A partir dos anos 1960 comezou a estudarse en profundidade esta capa e o medio que a compón. [ 13 ] .

Xa que corresponde á superficie de todos os océanos e augas continentais, o dominio do neusto ocupa máis do 70% da superficie do mundo, e a súa biodiversidade conta probabelmente con milleiros de especies. [ 12 ] A maior parte dos taxons de seres vivos están representados, polo menos en certas etapas do seu ciclo biolóxico. Non é necesario forzosamente que un organismo viva permanentemente na veciñanza da superficie das augas para que sexa considerado como integrante deste ecosistema. [ 14 ] Numerosos organismos peláxicos son, en efecto, susceptíbeis de faceren desprazamentos entre a auga e a superficie, e o desenvolvemento dun número considerábel de especies peláxicas e bentónicas pasa por fases (ovos, larvas) que se desenvolven nas capas superficiais das masas de auga.

Entre os organismos máis comúns que compoñen o medio neustónico encóntranse as bacterias, os copépodoss e as algas diatomeas, crisoficeas e xantoficeas. [ 3 ] Entre os depredadores destaca o zooplancto. [ 15 ]

Cómpre sinalar que en ocasións fórmanse na superficie unhas finas películas azuladas constituídas por fitoplancto e bacterias que teñen unha actividade moi elevada, aínda que a súa duración non exceda dunhas poucas horas. Estas formacións esporádicas denomínanse slicks, e poden degradar o petróleo cru en augas contaminadas. [ 2 ]


Neuston habitat

Very special conditions prevail directly on or below the surface of the water to which animals have to be adapted in order to survive here. For example, the proportion of harmful ultraviolet radiation is high, and it is assumed that the blue or violet colorations that often appear in new tones represent a radiation protection. Temperature and salinity are very variable in the course of the day, and strong waves occur during storms. In addition, Neuston species are exposed to predators both from the water and from the air, which is why they often experience the phenomenon of so-called countershading (different colors on the top and bottom). A special form of the new clay is the Epineuston , which only includes organisms that live directly on the water surface. One example is the water strider.

Often the species grouped together as Pleuston are added to the Neuston, as it is difficult to separate the two groups.


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Conclusion

Values of C and N isotopic ratios for the neuston are dependent on the environmental characteristics of the oceanographic regimes of each province. Uptake of atmospheric carbon were found to be associated with high δ 13 C values, whereas upwelling influenced regions or the presence of dinoflagellates and coccolithophores appear to be related with low δ 13 C. Additionally, high δ 15 N is a consequence of nitrogen uptake derived from denitrification processes and NO3 − diffusive fluxes, while nitrogen fixation by diazotrophs resulted in low δ 15 N.

The hypothesis of a common trophic structure of the neustonic community is supported by the general niche overlap between FGs regardless of the province, although chaetognaths and detritivores generally occupied the highest and lowest trophic positions, respectively. The importance of omnivory in oligotrophic regions (the majority of provinces sampled in this study) is consolidated with our results since omnivores and carnivores exhibit varying trophic positions regardless of their nominal trophic category. Environmental conditions were depicted to influence the trophic structure of the FGs, as the size and overlap of isotopic niches were related to changes in some of the variables. Typically, FGs present smaller niche size and overlap as favorable conditions increase whereas disadvantageous conditions promote the opposite. The use of isotopic niche metrics allowed the comparison of the trophic structure of the neustonic community across the tropical and subtropical ocean, which is paramount for understanding neuston interactions and its role in pelagic food web. Further studies exploring additional FGs and/or taxonomical diversity, evaluating temporal variability and impacts on the trophic structure of the community within each province, as well as estimates of neustonic biomass, are required to better understand and improve the knowledge of the trophic structure of the neustonic community in the pelagic ocean.


What is Nekton?

Nekton includes the animals that actively move in the water. Examples include vertebrates such as fish, whales, turtles, sharks and invertebrates include squads. Nekton live throughout the water column and can move faster than water currents. Nekton propel in the water column freely either by swimming or other means.


More Question Set for Fisheries

26. Colour pattern of ornamental fish comes under:
(a) Qualitative variations
(b) Both (a) & (c)
(c) Quantitative variations
(d) None of these

27. The science dealing with the various systems of inland waters, usually freshwater is called:
(a) Limnology
(b) Hydrology
(c) Hypology
(d) Inland geography

28. In soil profile, zone of eluviation is:
(a) O-zone
(b) B-zone
(c) A-zone
(d) C-zone

29. The gap between what is and what ought to be is termed as :
(a) Necessity
(b) Comfort
(c) Demand
(d) Need

30. The degree to which an innovation is perceived as better than the idea it supersede :
(a) Economic advantage
(b) Relativity
(c) Relative advantage
(d) Cost benefit production

31. Which of the following compounds will react with sulphuric acid to form a salt and water :
(a) Na2SO4
(b) NaOH
(c) HCL
(d) CaCl2

32. Scientific name of killi fish :
(a) Osphronemus spp
(b) Aplocheilus spp.
(c) Betta splendens
(d) Xiphophorus spp.

33. Gold fish eggs are:
(a) Pelagic and sticky
(b) Pelagic and non-sticky
(c) Demersal and sticky
(d) Demersal and non-sticky

34. The amount of living tissue per unit area/ volume at a given point in time:
(a) Standing crop
(b) Both (a) & (c)
(c) Total biomass
(d) None of these

35. Organism attaché or clinging to water plants:
(a) Nekton
(b) Periphyton
(c) Neuston
(d) All of these

36. The production of small reservoir is:
(a) 50kg/ha/yr
(b) 11.5kg/ha/yr
(c) 12.3kg/ha/yr
(d) 40kg/ha/yr

37. The organisms surviving at the air –water interface
(a) Nekton
(b) Pleuston
(c) Neuston
(d) None of these

38. It is an animal association where no partner is harmed. One or both the partners are benefited is called :
(a) Symbiosis
(b) Commensalism
(c) Mutualism
(d) None of these

39. National innovation foundation is an autonomous society established in the year :
(a) 2000
(b) 2002
(c) 2001
(d) 2004

40. Production function is the mathematic relationship between:
(a) Input and input
(b) Output and output
(c) Input and output
(d) Production and product

41. The Extension Education section of ICAR was established in the year:
(a) 1971
(b) 1975
(c) 1980
(d) 2005

42. One of the ex-situ conservation method for endangered species is:
(a) Wildlife sanctuaries
(b) Cryopreservation
(c) Biosphere reserve
(d) National park

43. Number of ecological hotspots in India is:
(a) 01
(b) 03
(c) 02
(d) 04

44. Functional status of an organism in its community:
(a) Niche
(b) Ecosystem
(c) Ecotone
(d) Biome

45. The average production of Indian reservoir:
(a) 20kg/ha/yr
(b) 50kg/ha/yr
(c) 30kg/ha/yr
(d) 100kg/ha/yr

46. In tropical fishes, age could be calculated from:
(a) Vertebra
(b) Scales
(c) Otolith
(d) Length frequency analysis

47. The example of colour changing ornamental fish:
(a) Channa blecheri
(b) Badis badis
(c) Chaca chaca
(d) Botia Dario

48. The ornamental fish capital in the world is:
(a) USA
(b) THAILAND
(c) JAPAN
(d) SINGAPORE

49. A life table represents:
(a) Feeding schedule
(b) Reproductive and mortality schedule
(c) Breeding schedule
(d) All of these

50. The first step in freshwater aquarium setting after fabrication:
(a) Planting
(b) Pouring Water
(c) Fixing Plants
(d) Adding Gravels


Watch the video: The Invisible Watery World of Plankton (August 2022).