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RESOURCES AND WORKING DRAFTS ONLY

Life on Europa[edit]

Europa, one of the moons orbiting Jupiter, is slightly smaller than the Earth's moon. It has a water-ice crust


Europa has the smoothest surface of any known solid object in the Solar System.[1] The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably harbour extraterrestrial life.[2] The predominant model suggests that heat from tidal flexing causes the ocean to remain liquid and drives ice movement similar to plate tectonics, absorbing chemicals from the surface into the ocean below.[3][4] Sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the sea floor. This may be important in determining whether Europa could be habitable.[5] In addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturn's moon Enceladus, which are thought to be caused by erupting cryogeysers.[6] In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated critical analysis of data obtained from the Galileo space probe, which orbited Jupiter from 1995 to 2003. Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon.[7][8][9][10]

In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated critical analysis of data obtained from the Galileo space probe, which orbited Jupiter between 1995 to 2003. Galileo flew by Europa in 1997 within 206 km (128 mi) of the moon’s surface and the researchers suggest it may have flown through a water plume.[7][8][9][10] Such plume activity could help researchers in a search for life from the subsurface European ocean without having to land on the moon.[7]

Conjectures regarding extraterrestrial life have ensured a high-profile for Europa and have led to steady lobbying for future missions.[11][12] The aims of these missions have ranged from examining Europa's chemical composition to searching for extraterrestrial life in its hypothesized subsurface oceans.[13][14] Robotic missions to Europa need to endure the high-radiation environment around itself and Jupiter.[12] Europa receives about 5.40 Sv of radiation per day.[15]

Evolution of jaws[edit]

Microscopic cross section through the pharynx of a larva from an unknown lamprey species

"One of the great events in the history of vertebrates was the appearance of jaws. This was beneficial for many reasons including:

  • New lines of adaptations
  • New possibilities for evolutionary advancement
  • Ability for territorial defence

The first jawed fishes were known as Placoderms and developed in the Devonian Period. The Placoderms had bony armour that covered the head and forepart of the body. In many, a movable joint between the head and body armour let the head rock back to open the mouth wide. The primitive jaws had jagged bony edges that served as teeth. The tail end usually lacked protection."[4]

"a revised jaw structure that freed up bones to form our inner ear..."

Acellular bone[edit]

Reconstruction of a long extinct jawless fish, Arandaspis, that lived in the Ordovician period about 480 to 470 million years ago. "The dermal bones of arandaspids consist of aspidine (acellular bone)"[16]
"the fin skeleton in the African lungfish Protopterus annectens consists of acellular bone.[17]:15
The bonefish (Albula vulpes) is the only vertebrate known to have both cellular and acellular bone.[17]:24[18]
A spotted gar larva at 22 days stained for cartilage (blue) and bone (red).
  • Khanna, Bhavna (2004) Ichthyology Handbook] Springer Science & Business Media. ISBN 9783540428541.

"acellular bone" is "bone that is not supported by or contain living cells".[5]

  • Arandaspida
  • Mineralized tissues
  • Halstead Tarlo, L. B. (1963). Aspidin: the precursor of bone. Nature, 199, 46-48.
  • Ruben, J. A., & Bennett, A. A. (1987). "The evolution of bone". Evolution, 41 (6): 1187–1197. PDF
  • Donoghue, P. C. J., Sansom, I. J., & Downs, J. P. (2006). Early evolution of vertebrate skeletal tissues and cellular interactions, and the canalization of skeletal development. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 306(3), 278–294. PDF
  • Currey, John D. (2013) Bones: Structure and Mechanics Princeton University Press. ISBN 9781400849505.
  • Hall, Brian K (2005) Bones and Cartilage: Developmental and Evolutionary Skeletal Biology Academic Press. ISBN 9780080454153.
  • Sire, J. Y., Donoghue, P. C., & Vickaryous, M. K. (2009). Origin and evolution of the integumentary skeleton in non‐tetrapod vertebrates. Journal of Anatomy, 214(4), 409-440. Full text

"One of the features of fish bone that has been discussed fairly extensively is the fact that most fish skeletons are characterized by acellular bone, lacking the osteocytes that comprise the majority of bone cells in tetrapods. Although there is variability within fish orders, cellular bone tends to be restricted to a portion of the Clupeiformes (herring and anchovies), Elopomorpha (eels, bonefish and tarpons) and Osteoglossomorpha (bonytongues and mooneyes)"[19][20]

"The functional and adaptive significance of acellular as opposed to cellular bone in fish is unclear; comparative studies of material properties have also been inconclusive".[21]

"Acellular bone is defined as bone which does not contain osteocytes. While with one exception—the bonefish Albula vulpes—a given species will contain a single type of bone, the variation between species and, for that matter, for different

"In two major groups of vertebrates, however, bone acellularity is the rule, not the exception. The two are extant teleost fishes and a group of Ordocician jawless vertebrates, the Heterostracans."[17] :24–30</ref>

References[edit]

  1. ^ "Europa".
  2. ^ Tritt, Charles S. (2002). "Possibility of Life on Europa". Milwaukee School of Engineering. Archived from the original on 9 June 2007. Retrieved 10 August 2007.
  3. ^ "Tidal Heating". geology.asu.edu. Archived from the original on 29 March 2006.
  4. ^ Dyches, Preston; Brown, Dwayne; Buckley, Michael (8 September 2014). "Scientists Find Evidence of 'Diving' Tectonic Plates on Europa". NASA. Retrieved 8 September 2014.
  5. ^ Dyches, Preston; Brown, Dwayne (12 May 2015). "NASA Research Reveals Europa's Mystery Dark Material Could Be Sea Salt". NASA. Retrieved 12 May 2015.
  6. ^ Cook, Jia-Rui C.; Gutro, Rob; Brown, Dwayne; Harrington, J.D.; Fohn, Joe (12 December 2013). "Hubble Sees Evidence of Water Vapor at Jupiter Moon". NASA.
  7. ^ a b c Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S. (14 May 2018). "Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures". Nature Astronomy. 2 (6): 459–464. Bibcode:2018NatAs...2..459J. doi:10.1038/s41550-018-0450-z.
  8. ^ a b McCartney, Gretchen; Brown, Dwayne; Wendel, JoAnna (14 May 2018). "Old Data Reveal New Evidence of Europa Plumes". Retrieved 14 May 2018.
  9. ^ a b Chang, Kenneth (14 May 2018). "NASA Finds Signs of Plumes From Europa, Jupiter's Ocean Moon". The New York Times. Retrieved 14 May 2018.
  10. ^ a b Wall, Mike (14 May 2018). "This May Be the Best Evidence Yet of a Water Plume on Jupiter's Moon Europa". Space.com. Retrieved 14 May 2018.
  11. ^ David, Leonard (7 February 2006). "Europa Mission: Lost In NASA Budget". Space.com.
  12. ^ a b Friedman, Louis (14 December 2005). "Projects: Europa Mission Campaign; Campaign Update: 2007 Budget Proposal". The Planetary Society. Archived from the original on 11 August 2011.
  13. ^ Chandler, David L. (20 October 2002). "Thin ice opens lead for life on Europa". New Scientist.
  14. ^ Muir, Hazel (22 May 2002) Europa has raw materials for life, New Scientist.
  15. ^ Ringwald, Frederick A. (29 February 2000) SPS 1020 (Introduction to Space Sciences) Course Notes Archived 20 September 2009 at WebCite, California State University, csufresno.edu.
  16. ^ Janvier, Philippe (1997) Arandaspida The Tree of Life Web Project.
  17. ^ a b c Hall, Brian K. (2005) Bones and Cartilage: Developmental and Evolutionary Skeletal Biology" Academic Press. ISBN 9780080454153.
  18. ^ Parenti, L. R. (1986). "The phylogenetic significance of bone types in euteleost fishes" Zoological journal of the Linnean Society, 87(1): 37-51.
  19. ^ Cite error: The named reference Fleming1967 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Parenti1986 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Horton2009 was invoked but never defined (see the help page).

Evolution of bone[edit]

The principle of homology illustrated by the adaptive radiation of the forelimb of mammals. All conform to the basic pentadactyl pattern but are modified for different usages. The third metacarpal is shaded throughout; the shoulder is crossed-hatched.
Hox gene expression in bones from tetrapod limbs. Bones in a tetrapod limb, shown here in a human arm (left), are produced following two waves of Hox gene activation during the early development of the limb (red and blue, middle left). At a comparable developmental stage, fish fins show only one domain of Hox gene expression (middle right), which subsequently generates complex bony patterns. Is this fish domain homologous to the proximal or to the distal expression domain in tetrapods? Can the underlying regulatory mechanisms help establish such evolutionary relationships? A study in PLOS Biology addresses these questions: doi:[https://doi.org/10.1371%2Fjournal.pbio.1001773 10.1371/journal.pbio.1001773

]

Fish and tetrapod HoxA and HoxD clusters are regulated by 3′ and 5′ regulatory landscapes, represented here as triangles due to their correspondence to topological domains.[2][3] Enhancer (indicated with colored shapes) interactions within these domains (indicated by arrows) occur with the neighboring parts of the Hox clusters, resulting in a regulatory partition between 3′ and 5′ parts of the clusters. In fishes, this mechanism may be used for patterning the fin proximal (red) to distal (orange) (P-D) polarity, through the potential function of these two landscapes in slightly different fin domains. Variation in the regulatory balance between these 3′ and 5′ landscapes through the acquisition of novel enhancers potentially explains interspecies differences in P-D fin morphology, as for instance between zebrafish and species such as coelacanth, which possesses a more elaborate fin skeleton. Although these regulatory landscapes may underlie the P-D patterning of fin skeletons, they both elicit a proximal response when assessed in transgenic mice, and hence the fish 5′ landscape is indicated as “proximal” (orange). In tetrapods, the 5′ domain (blue) has acquired new enhancers or modified existing ones, thereby evolving a novel, more distal autopodial identity, perhaps as a response to preexisting signals emanating from the apical ectoderm.

The main function of bone is to be stiff.[1]

Only vertebrates have bones.[2]

"Whereas cartilage may be found in vertebrates and many invertebrates, bone is a unique, typically vascularized skeletal tissue found only in vertebrate animals".[3]

Several hypotheses have been proposed for how bone evolved as a structural element in vertebrates. One hypothesis is that bone developed from tissues that evolved to store minerals. Specifically, calcium-based minerals were stored in cartilage and bone was an exaptation development from this calcified cartilage.[4] However, other possibilities include bony tissue evolving as an osmotic barrier, or as a protective structure.

[5] [6] [7] [8] [9]

References[edit]

  1. ^ Currey, John D. (2013) Bones: Structure and Mechanics, pages 27-28, Princeton University Press. ISBN 9781400849505.
  2. ^ Linzey, Donald W. (2012) Vertebrate Biology p.83, JHU Press. ISBN 9781421400402.
  3. ^ Cite error: The named reference Hall2005 was invoked but never defined (see the help page).
  4. ^ Donoghue PC, Sansom IJ (2002). "Origin and early evolution of vertebrate skeletonization". Microsc. Res. Tech. 59 (5): 352–72. doi:10.1002/jemt.10217. PMID 12430166.
  5. ^ Horton, J. M. and Summers, A. P. (2009). "The material properties of acellular bone in a teleost fish". Journal of Experimental Biology, 212 (9): 1413-1420. doi:10.1242/​jeb.020636. Full text
  6. ^ Fleming, W.R. (1967). "Calcium Metabolism of Teleosts". American Zoologist, 7: 835-842.
  7. ^ Moss, M.L. (1961). "Osteogenesis of acellular teleost fish bone". American Journal of Anatomy, 108: 99–109.
  8. ^ Parenti, L.R. (1986). "The phylogenetic significance of bone types in euteleost fishes". Zoological Journal of the Linnean Society, 87: 37-51.
  9. ^ Huttenlocker AK, Woodward HN and Hall BK (2013) "The Biology of Bone" In: K Padian and E-T Lamm, Bone Histology of Fossil Tetrapods: Advancing Methods, Analysis, and Interpretation, pp. 13–34, University of California Press. ISBN 9780520273528.

Fish teeth[edit]

Teeth of the lower and upper jaws of the seawolf (Anarhichas lupus)
Denture of Trichiurus lepturus[1][2]
Jaw of the bowmouth guitarfish,Rhina ancylostoma


From Tooth...

Some animals develop only one set of teeth (monophyodont) while others develop many sets (polyphyodont). Sharks, for example, grow a new set of teeth every two weeks to replace worn teeth... Teeth are not always attached to the jaw, as they are in mammals. In many reptiles and fish, teeth are attached to the palate or to the floor of the mouth, forming additional rows inside those on the jaws proper. Some teleosts even have teeth in the pharynx. While not true teeth in the usual sense, the denticles of sharks are almost identical in structure, and are likely to have the same evolutionary origin. Indeed, teeth appear to have first evolved in sharks, and are not found in the more primitive jawless fish - while lampreys do have tooth-like structures on the tongue, these are in fact, composed of keratin, not of dentine or enamel, and bear no relationship to true teeth.[3] Though "modern" teeth-like structures with dentine and enamel have been found in late conodonts, they are now supposed to have evolved independently of later vertebrates' teeth.[4][5]"

Seagrass[edit]

"Seagrasses are flowering plants that live in the ocean. The evolutionary trajectory is something like this: Green algae lives in the ocean. It adapts to freshwater, then eventually colonizes land and evolves into a a plant similar to moss which reproduces by airborne spores, then later gains height and eventually develops xylem and phloem to transport water and nutrients, becoming a vascular plant. Later come seeds and after a tough evolutionary slog, over a hundred million years after seeds, flowering plants show up. Whew. Finally, perhaps toward the end of the Cretaceous, the earliest seagrasses shift from living in freshwater to living in the ocean, perhaps moving down the rivers in a reversal of their origination hundreds of millions of years earlier. A fabulous evolutionary success. What does it tell us about evolution’s failures? Well, a species can only evolve into a new niche if either it has an advantage over the current inhabitants—or if the niche is empty. I believe that seagrasses evolved to occupy an empty niche that no marine algae already occupied. Seagrasses compete with microscopic algae, but large algae doesn’t grow where seagrasses do. Multicellular red algae has existed for at least 1,200 million years. Green algae fossils are known from the Cambrian, over 500 million years ago. So, with red and green algae having had opportunity over geological time, how could the seagrass niche remain empty? Or if the niche wasn’t empty, then how did a land plant outcompete some algae that was on its home ground and should have been ideally adapted? Evolution has the weakness that it can only operate in small steps. Life walks to the edge of its fitness limit, but it can’t look beyond. There is a long sequence of short steps that runs from green algae to seagrasses—we know because seagrasses took them—but there may not exist any such sequence that stays entirely in the ocean. You can’t get from there to here without taking a detour to collect different adaptations."[6]

"Seagrasses are ancient plants that evolved from land plants when dinosaurs roamed the earth. They are not seaweeds (marine algae). Seagrasses are unique plants that flower underwater and have colonized all but the most polar seas. There are only 60 species of seagrass globally. Seagrasses grow under sea ice as well as adjacent to coral reefs. They live in shallow water along exposed coasts and in sheltered lagoons and estuaries."[6]

"Seagrasses are unique plants; the only group of flowering plants to recolonise the sea. They occur on every continental margin, except Antarctica, and form ecosystems which have important roles in fisheries, fish nursery grounds, prawn fisheries, habitat diversity and sediment stabilisation."[7]

"Seagrasses occur in coastal zones throughout the world in the areas of marine habitats that are most heavily influenced by humans. Despite a growing awareness of the importance of these plants, a full appreciation of their role in coastal ecosystems has yet to be reached."[8]

"Seagrasses, a group of about sixty species of underwater marine flowering plants, grow in the shallow marine and estuary environments of all the world's continents except Antarctica. The primary food of animals such as manatees, dugongs, green sea turtles, and critical habitat for thousands of other animal and plant species, seagrasses are also considered one of the most important shallow-marine ecosystems for humans since they play an important role in fishery production. Though they are highly valuable ecologically and economically, many seagrass habitats around the world have been completely destroyed or are now in rapid decline."[9]

"Seagrass: A marine grass that grows in the intertidal and shallow subtidal zones."[10]

"Seagrasses are flowering plants that have evolved to live in sea water".[11]

"Seagrass is a taxonomic group of about 60 species worldwide likely evolving from a single monocotyledonous flowering plant ancestor (70-100 million years ago), divided into three independent lineages: Hydrocharitaceae, Cymodoceaceae and Zosteraceae.[12] Seagrass species have strong physiological similitude and low interspecies diversity."[13] In: Andrew J. Price and Jessica A. Kelton (Eds) Herbicides - Current Research and Case Studies in Use, Chapter 14, InTech. ISBN 978-953-51-1112-2. doi:10.5772/55973</ref>

"Scientists say a patch of ancient seagrass in the Mediterranean is up to 200,000 years old".[14]

"Seagrass is the only flowering plant that lives in the sea".[15]

"Stems of seagrass creep a few centimetres beneath the mud and become so interwoven with those of adjacent plants that a firm mat develops. This anchors the plants and helps stabilise shifting sediments during the tidal cycle. Over time, sediments build up within and behind seagrass beds, and other flowering plants colonise the higher ground."[16]

Species[edit]

Evolution[edit]

Evolution of seagrasses, showing the progression onto land from marine origins, the diversification of land plants and the subsequent return to the sea by the seagrasses.

Threatened species[edit]

"In a recent study, 15 of the 72 known species of seagrasses were listed as 'Endangered', 'Vulnerable' or 'Near Threatened' on the International Union for Conservation of Nature (IUCN) Red List."[7][8]

"Seagrass researcher at the University of Technology Sydney, Peter Macreadie says there are multiple factors that make seagrass vulnerable, but the biggest threat is the creation of anoxic dead zones by algal blooms. “Seagrass are plants that grow on the seafloor, so when nutrient runoff is taken up by the algae, the algae become dense and it blocks the sunlight from reaching the seagrass.” There is also direct damage done by humans via dredging or by boat propellers. If some plants are disturbed in the middle of a meadow, the ‘hole’ will actually get bigger and bigger, eating away the meadow from the inside. “We know we’ve lost 30% of the world’s sea grasses already,” says Macreadie.Many seagrass scientists are now concerned about changes in water temperature caused by the apparent effects of climate change, he added. “Seagrass is changing its range and distribution, but they can only tolerate a certain set of temperatures.” [9]

"Past director of the University of Western Australia’s Oceans Institute, Gary Kendrick says restoration can get expensive. “I’ve been working on a five-year restoration project and the chances of full recovery are still slim, as restoration is high risk and high expenditure. The seagrass restoration itself can cost anywhere from AU$8,000 a hectare to hundreds of thousands of dollars per hectare,” he says. “There are studies of a field that cost $1 million a hectare to restore. That’s about ten times what it costs to restore a forest. It is much easier to conserve the seagrass habitats we already have in the first place, rather than trying to restore them after the fact"[10]

References[edit]

  1. ^ Diekwisch Lab: Evolution and Development
  2. ^ [site:https://commons.wikimedia.org ribbonfish "Trichiurus lepturus" search]
  3. ^ Cite error: The named reference VB was invoked but never defined (see the help page).
  4. ^ McCOLLUM, MELANIE; SHARPE, PAUL T. (July 2001). "Evolution and development of teeth". Journal of Anatomy. 199 (1–2): 153–159. doi:10.1046/j.1469-7580.2001.19910153.x.
  5. ^ nature.com, Fossil scans reveal origins of teeth, 16 October 2013
  6. ^ Seagrasses: Prairies Of The Sea
  7. ^ Larkum AWD, RRJ Orth, CM Duarte (Eds) Seagrasses: Biology, Ecology and Conservation Springer. ISBN 9781402029837.
  8. ^ Larkum AWD, MacComb AJ and Shepherd SA (Eds) (1989) Biology of seagrasses Elsevier Science Limited. ISBN 9780444874030.
  9. ^ Green EP and Short FT (Eds)(2003) World Atlas of Seagrasses University of California Press. ISBN 9780520240476. Full text
  10. ^ Schwartz M (2006) Encyclopedia of Coastal Science Springer. ISBN 9781402038808.
  11. ^ Seagrasses Australian Institute of Marine Science. Retrieved 12 October 2013.
  12. ^ D. H Les, M. A Cleland, M Waycott, Phylogenic studies in the Alismatidea, II: Evolution of the marine angiosperm (seagrasses) and hydrophily. Systematic Botany 199722443
  13. ^ Devault, A. Damien and Hélène Pascaline (2013) "Herbicide Impact on Seagrass Communities"
  14. ^ 'Oldest living thing on earth' discovered The Telegraph, 7 February 2012.
  15. ^ Maggy Wassilieff. 'Estuaries - Plants of the estuary', Te Ara - the Encyclopedia of New Zealand, updated 9-Jul-13 URL: http://www.TeAra.govt.nz/en/photograph/4624/seagrass
  16. ^ [1]

Seagrass meadow[edit]

Marine habitats
Sanc0209 - Flickr - NOAA Photo Library.jpg
Seagrass meadows are highly productive ecosystems and nurseries to many marine species. They are major carbon sinks.

As a nursery[edit]

As a carbon sink[edit]

Blue carbon[edit]

"Blue carbon is the carbon captured by the world’s oceans and represents more than 55% of the green carbon. The carbon captured by living organisms in oceans is stored in the form of sediments from mangroves, salt marshes and seagrasses. It does not remain stored for decades or centu- ries (like for example rainforests), but rather for millennia... the coastal ocean also contains vast areas covered by algal beds. Most macroalgal beds (including kelp forests) do not bury carbon, as they grow on rocky substrates where burial is impossible.... For instance, es- timates of the area covered by mangroves, probably the best constrained amongst vegetated coastal habitats, ranges from 0.11 to 0.24 million sq km (Bouillon et al., 2008). Estimates of the area covered by seagrass meadows, the least constraint estimate, range from a documented area of 0.12 million sq km (Green and Short, 2003), to an upper estimate of 0.6 million sq km (Duarte and Chiscano, 1999) as the South East Asian archipelagos, such as Indonesia, are likely to hold vast, un- charted seagrass meadows (Duarte et al., 2009). Indeed, the coastal area with sufficient submarine irradiance as to support seagrass meadows has been estimated at 5.2 million sq km (Gattuso et al., 2006). Hence, a thorough inventory of blue carbon sinks may well yield a cover twice as large as the mean area considered in current, conservative global assessments (Table 1)... Restoring lost seagrass meadows is more complex, as the labour required to insert transplants under the water in- creases cost. Seagrass restoration projects have consequently remained comparatively limited in size (a few hectares) and number. However it is a viable option provided the benefits of seagrass restoration can be used strategically, for example to catalyze the great potential for natural recovery.... The ocean’s vegetated habitats, in particular mangroves, salt marshes and seagrasses, cover <0.5% of the sea bed. These form earth’s blue carbon sinks and account for more than 50%, perhaps as much as 71%, of all carbon storage in ocean sediments. They comprise only 0.05% of the plant biomass on land, but store a comparable amount of carbon per year, and thus rank among the most intense carbon sinks on the planet.... Vegetated coastal habitats – mangrove forests, salt­marshes and seagrass meadows – have much in common with rain forests: they are hot spots for biodiversity, they provide important and valuable ecosystem functions, including a large carbon sink capacity, and they are experiencing a steep global decline (Duarte et al., 2008, Duarte, 2009). Indeed, the world is losing its coastal habitats four times faster than its rain forests (Duarte et al., 2008, Duarte, 2009) and the rate of loss is accelerating (Waycott et al., 2009). However, whereas society is well informed of the benefits and threats associated with rainforests, there is a comparative lack of awareness on the status and benefits of vegetated coastal habitats. This is perhaps because of a “charisma” gap, where these often submerged, out of sight coastal habitats, are not as appealing to the public as their terrestrial counterparts (Duarte et al., 2008). ... The remaining excess production of mangrove forests, salt-marshes and sea- grass meadows is buried in the sediments, where it can remain stored over millenary time scales (Mateo et al., 1997), thereby representing a strong natural carbon sink. This is most evident in the case of seagrass meadows, which accumulate enough materials as to significantly raise the seafloor, forming mats that can exceed 3 metres in depth. In addition to burying a fraction of their own production, blue carbon sinks reduce flow, alter turbulence and attenuate wave action (Koch et al., 2006), thereby promoting sedimentation and reducing sediment resuspension (e.g. Gacia and Duarte, 2001). Recent research has shown that the canopies of seagrass meadows trap particles entrained in the flow, which lose mo- mentum upon impacting on the leaves, thereby promoting the sedimentation of suspended material to the seafloor (Hendriks et al., 2007). Isotopic analyses of the organic carbon accumu- lated in sediments of vegetated coastal habitats have shown that a significant fraction derives from plankton (Gacia et al., 2002).... they are disappearing faster than anything on land and much may be lost in a couple of decades. These areas, covering features such as mangroves, salt marshes and seagrasses, are responsible for capturing and storing up to some 70% of the carbon permanenty stored in the marine realm.... A recent assessment indicates that about one-third of the glob- al seagrass area has been already lost, and that these losses are accelerating, from less than 0.9% year–1 in the 1970’s to more than 7% year–1 since 2000 (Waycott et al., 2009)....".[1]

"We are really only just starting to discover the exact amounts of CO2 released. Linwood Pendleton of Duke University, North Carolina has produced a paper, [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0043542 "Estimating Global "Blue Carbon" Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems", with a large group of fellow-scientists which elucidates this large calculation. While these coastal strips cover 6% of the earth's forests, they make up a massive 20% of the deforestation carbon... The marginal value of damage from climate change that can be caused by one ton of carbon in the atmosphere in 2020 is one heck of an estimate, but it comes out at $41."[2]

Reports...

Other...

Families

Zosteraceae|Hydrocharitaceae|Posidoniaceae|Cymodoceaceae

Genera

Phyllospadix|Zostera|Enhalus|Halophila|Thalassia|Posidonia|Amphibolis|Cymodocea|Halodule|Syringodium|Thalassodendron

IMAGES...

[11]

Gallery[edit]


Sources[edit]

Videos

Seagrass: Pastures of the sea

Articles












Organisations
Recovery
sea otters
Lucinidae


Dugongs, manatees and seagrass

"Seagrass was an important dietary resource for these animals from early in their evolution, as is evident by the association of sirenian fossils with deposits containing fossilised seagrasses. The sea cows' use of seagrass meadows probably brought about substantial changes in the structure and dynamics of this ecosystem, and it has been suggested that "the close herbivore-plant connection between sirenians and seagrasses over the past 50 million years may have led to significant co-evolution" (Clementz et al. 2006, Journal of Vertebrate Paleontology, vol. 26, p. 365)."[3]

Reports
  • Koch, E.W., L.P. Sanford, S.N. Chen, D.J. Shafer and J.M. Smith (2006) [el.erdc.usace.army.mil/elpubs/pdf/tr06-15.pdf Waves in seagrass systems: review and technical recommendations] US Army Corps of Engineers Technical Report. Engineer Research and Development Center, ERDC TR-06-15.
  • Waycott, Michelle et al. (2007) Vulnerability of seagrasses in the Great Barrier Reef to climate change Pages 193–236 of a report by the Great Barrier Reef Marine Park Authority and Australian Greenhouse Office.
handbook
Books
Manuals

See also[edit]

References[edit]

  1. ^ Blue Carbon - The Role of Healthy Oceans in Binding Carbon
  2. ^ Blue Carbon estimates up! Earth Times, 10 September 2012.
  3. ^ [Agriculture in dugongs] Map of Life, University of Cambridge. Retrieved 13 October 2013.

Marine biology[edit]

"Marine biology is the study of life in the oceans and other saltwater environments such as estuaries and wetlands. All plant and animal life forms are included from the microscopic picoplankton all the way to the majestic blue whale, the largest creature in the sea—and for that matter in the world... It wasn't until the writings of Aristotle from 384-322 BC that specific references to marine life were recorded. Aristotle identified a variety of species including crustaceans, echinoderms, mollusks, and fish..."[1]

"The study of marine biology includes a wide variety of disciplines such as astronomy, biological oceanography, cellular biology, chemistry, ecology, geology, meteorology, molecular biology, physical oceanography and zoology and the new science of marine conservation biology draws on many longstanding scientific disciplines such as marine ecology, biogeography, zoology, botany, genetics, fisheries biology, anthropology, economics and law."[1]

Sub fields of marine biology include:

  • Microbiology: The "study of microorganisms, such as bacteria, viruses, protozoa and algae, is conducted for numerous reasons. One example is to understand what role microorganisms play in marine ecosystems. For example, bacteria are critical to the biological processes of the ocean, as they comprise 98% of the ocean's biomass, which is the total weight of all organisms in a given volume. Microbiology is also important to our understanding of the food chain that connects plants to herbivorous and carnivorous animals. The first level in the food chain is primary production, which occurs at the microbial level. This is an important biological activity to understand as primary production drives the entire food chain. Scientists also study marine microbiology to find new organisms that may be used to help develop medicines and find cures for diseases and other health problems."[1]
  • Fisheries and Aquaculture: to "protect biodiversity and to create sustainable seafood sources because of the world's dependence on fish for protein. There are many areas of study in this field.
    • The ecology of fisheries includes the study of their population dynamics, reproduction, behavior, food webs, and habitat.
    • Fisheries management includes studies on the impact of overfishing, habitat destruction, pollution and toxin levels, and ways to increase populations for sustainability as seafood.
    • Aquaculture includes research on the development of individual organisms and their environment. The objective is most often to develop the knowledge needed to cultivate certain species in a designated area in open water or in captivity in order to meet consumer demand. Technological advances have enabled seafood "farms" to produce high-demand products that traditional commercial fisheries cannot meet. This is a controversial area however, and an issue that will become of greater importance as our fish stocks continue to decline."[1]
  • Environmental marine biology: includes "the study of ocean health. It is important for scientists to determine the quality of the marine environment to ensure water quality is sufficient to sustain a healthy environment. Coastal environmental health is an important area of environmental marine biology so that scientists can determine the impact of coastal development on water quality for the safety of people visiting the beaches and to maintain a healthy marine environment. Pollutants, sediment, and runoff are all potential threats to marine health in coastal areas. Offshore marine environmental health is also studied. For example, an environmental biologist might be required to study the impact of an oil spill or other chemical hazard in the ocean. Environmental biologists also study Benthic environments on the ocean bottom in order to understand such issues as the chemical makeup of sediment, impact of erosion, and the impact of dredging ocean bottoms on the marine environment."[1]
  • Deep-sea ecology: "advances in technology of equipment needed to explore the deep sea have opened the door to the study of this largely unknown space in the sea. The biological characteristics and processes in the deep-sea environment are of great interest to scientists. Research includes the study of deep ocean gases as an alternate energy source, how animals of the deep live in the dark, cold, high pressure environment, deep sea hydrothermal vents and the lush biological communities they support."[1]
  • Ichthyology: is "the study of fishes, both salt and freshwater species. There are some 25,000+ species of fishes including: bony fishes, cartilaginous fishes, sharks, skates, rays, and jawless fishes. Ichthyologists study all aspects of fish from their classification, to their morphology, evolution, behavior, diversity, and ecology. Many ichthyologists are also involved in the field of aquaculture and fisheries."[1]
  • Marine mammology: "This is the field of interest to most aspiring marine biologists. It is the study of cetaceans—families of whales and dolphins, and pinnipeds (seals, sea lions, and the walrus). Their behaviors, habitats, health, reproduction, and populations are all studied. These are some of the most fascinating creatures in the sea; therefore, this is an extremely competitive field, and difficult to break into because the competition for research funding is also quite heavy. One area of research currently being conducted on whales is the impact of military sonar on their health and well-being. The scientific community believes that high frequency sound waves cause internal damage and bleeding in the brains of whales, yet the military denies this claim. Military sonar can also interfere with the animal's own use of sonar for communication and echolocation. More research is needed; however, in recent years science has proven the claims to be valid and the military has begun limiting its use of sonar in specific areas."[1]
  • Marine ethology: "The behavior of marine animals is studied so that we understand the animals that share the planet with us. This is also an important field for help in understanding how to protect endangered species, or how to help species whose habitats are threatened by man or natural phenomena. The study of marine animal behavior usually falls under the category of ethology because most often marine species must be observed in their natural environment, although there are many marine species observed in controlled environments as well. Sharks are most often studied in their natural habitat for obvious reasons."[1]

"Advances in technology have opened up the ocean to exploration from the shallows to the deep sea. New tools for marine research are being added to the list of tools that have been used for decades such as:"[1]

  • Trawling - "has been used in the past to collect marine specimens for study, except that trawling can be very damaging to delicate marine environments and it is difficult to collect samples discriminately. However when used in the midwater environment, trawls can be every effective at collecting samples of elusive species with a wide migratory range."[1]
  • Plankton nets - plankton nets have a very fine weave to catch microscopic organisms in seawater for study."[1]
  • Remotely operated vehicles (ROVs) - have been used underwater since the 1950s. ROVs are basically unmanned submarine robots with umbilical cables used to transmit data between the vehicle and researcher for remote operation in areas where diving is constrained by health or other hazards. ROVs are often fitted with video and still cameras as well as with mechanical tools for specimen retrieval and measurements."[1]
  • Underwater habitats - "the National Oceanic and Atmospheric Administration (NOAA) operates Aquarius external link, a habitat 20 external link m beneath the surface where researchers can live and work underwater for extended periods."[1]
  • Fiber optics - Fiber optic observational equipment uses LED light (red light illumination) and low light cameras that do not disturb deep-sea life to capture the behaviors and characteristics of these creatures in their natural habitat."[1]
  • Satellites - are "used to measure vast geographic ocean data such as the temperature and color of the ocean. Temperature data can provide information on a variety of ocean characteristics such as currents, cold upwelling, climate, and warm water currents such as the Gulf Stream. Satellites are also used for mapping marine areas such as coral reefs and for tracking marine life tagged with sensors to determine migratory patterns."[1]
  • Sounding - "hydrophones, the microphone's counterpart, detect and record acoustic signals in the ocean. Sound data can be used to monitor waves, marine mammals, ships, and other ocean activities."[1]
  • Sonar - "similar to sounding, sonar is used to find large objects in the water and to measure the ocean's depth (bathymetry). Sound waves last longer in water than in air, and are therefore useful to detect underwater echoes."[1]
  • Computers - "sophisticated computer technology is used to collect, process, analyze, and display data from sensors placed in the marine environment to measure temperature, depth, navigation, salinity, and meteorological data. NOAA implemented computer technology aboard its research vessels to standardize the way this data is managed."[1]

"The difference between the terms "marine biology" and "biological oceanography" is subtle, and the two are often used interchangeably. As mentioned above, marine biology is the study of marine species that live in the ocean and other salt-water environments. Biological oceanography also studies marine species, but in the context of oceanography. So a biological oceanographer might study the impact of cold upwellings on anchovy populations off the coast of South America, where a marine biologist might study the reproductive behavior of anchovies."[1]

History[edit]

Taxonomy[edit]

  • "Marine Taxonomy MarineBio.org. Retrieved 30 April 2011. Updated 26 Novemver 2010.

Fishing down[edit]

"‘Fisheries in Balance’ (FiB) indices were also computed and plotted against time. All someone needs to estimate the mean trophic level of the catches derived from a marine region are the individual catch weight and trophic level values of all species participating in the local catches. In this case, the mean trophic level of the catch in a particular year is estimated by multiplying the trophic level of each species by its catch weight; add these across all species participating in the catches and divide this by the total catch of all species in this particular year (PAULY et al., 1998)."[2]

"The FiB index is used to track the ‘fishing down the food web’ process (PAULY & PALOMARES, 2005). Given a time-series of catches and their mean trophic levels, the FiB index is calculated for each year of a time-series, as the ratio, at a log scale, between: (a) the total annual catch, multiplied by the energy transfer efficiency between trophic levels (an ecosystem property, having a mean value of 10%) after the latter has been raised to the mean trophic level of the catch and (b) the estimate of (a) above for the first year of a time-series as a reference (PAULY & PALOMARES, 2005). The FiB index (PAULY & PALOMARES, 2005): (a) attains a value of 0 for the first year of the series; (b) does not vary during periods in which trophic level and catches change in opposite directions; and (c) increasing or decreasing FiB values indicate a geographic expansion or contraction (or collapse) of the underlying fishery, respectively."[2]


"any authors - fisheries scientists and others- have pointed out that modern marine fisheries tend to operate lower in the food web and had given various names to this trend ("biomass fishing", "industrial fishing", "exploiting forage fish", etc).

This trend was recently quantified, and given what might become its definite name - "fishing down marine food webs" (FDMFW) in a report of the same name published in Science on February 6, 1998.

FDMFW, authored by Daniel Pauly and Johanne Dalsgaard of the Fisheries Centre, and V. Christensen, R. Froese and F. Torres Jr. of ICLARM relied on two sets of data:

1) Estimates of trophic levels of major species groups in global fisheries landings; and

2) Global fisheries catches, as compiled by the Food and Agriculture Organization of the United Nations as also incorporated in FishBase, the global database on fish.

The trophic levels in (1) were estimated from 60 ECOPATH models.

Colleagues interested in replicating the results on FDMFW are free to use the trophic levels on the file linked with this text, while the required catch statistics may be obtained from FAO or from FishBase 97 (see also Fig. 4). Our trophic level estimate may be also used for more local studies, in combination with national catch series. In either case, the trophic level estimate may be cited as:

Pauly, D. and V. Christensen. 1997. Trophic levels of fishes. Box 16, p. 127 In R. Froese and D. Pauly (eds) FishBase 97: concepts, design and data sources. ICLARM, Manila."[3]

Food webs[edit]

An ecological pyramid.

Trophic level[edit]

Forage fish occupy central positions in the ocean food webs. The position that a fish occupies in a food web is called its trophic level (Greek trophē = food). The organisms it eats are at a lower trophic level, and the organisms that eat it are at a higher trophic level. Forage fish occupy middle levels in the food web, serving as a dominant prey to higher level fish, seabirds and mammals.

Ecological pyramids are graphical representations, along the lines of the diagram at the right, which show how biomass or productivity changes at each trophic level in a ecosystem. The first or bottom level is occupied by primary producers or autotrophs (Greek autos = self and trophe = food). These are the names given to organisms that do not feed on other organisms, but produce biomass from inorganic compounds, mostly by a process of photosynthesis.

In oceans, most primary production is performed by algae. This is a contrast to land, where most primary production is performed by vascular plants. Algae ranges from single floating cells to attached seaweeds, while vascular plants are represented in the ocean by groups such as the seagrasses. Larger producers, such as seagrasses and seaweeds, are mostly confined to the littoral zone and shallow waters, where they attach to the underlying substrate and still be within the photic zone. Most primary production in the ocean is performed by microscopic organisms, the phytoplankton.

Level 1
Seawifs global biosphere.jpg

Thus, in ocean environments, the first bottom trophic level is occupied principally by phytoplankton, microscopic drifting organisms, mostly one-celled algae, that float in the sea. Most phytoplankton are too small to be seen individually with the unaided eye. They can appear as a green discoloration of the water when they are present in high enough numbers. Since they increase their biomass mostly through photosynthesis they live in the sun-lit surface layer (euphotic zone) of the sea.

The most important groups of phytoplankton include the diatoms and dinoflagellates. Diatoms are especially important in oceans, where they are estimated to contribute up to 45% of the total ocean's primary production.[4] Diatoms are usually microscopic, although some species can reach up to 2 millimetres in length.

Level 2

The second trophic level (primary consumers) is occupied by zooplankton which feed off the phytoplankton. Together with the phytoplankton, they form the base of the food pyramid that supports most of the world's great fishing grounds. Zooplankton are tiny animals found with the phytoplankton in oceanic surface waters, and include tiny crustaceans, and fish larvae and fry (recently-hatched fish). Most zooplankton are filter feeders, and they use appendages to strain the phytoplankton in the water. Some larger zooplankton also feed on smaller zooplankton. Some zooplankton can jump about a bit to avoid predators, but they can't really swim. Like phytoplankton, they float with the currents, tides and winds instead. Zooplanktons can reproduce rapidly, their populations can increase up to thirty percent a day under favourable conditions. Many live short and productive lives and reach maturity quickly.

Particularly important groups of zooplankton are the copepods and krill. Copepods are a group of small crustaceans found in ocean and freshwater habitats. They are the biggest source of protein in the sea,[5] and are important prey for forage fish. Krill constitute the next biggest source of protein. Krill are particularly large predator zooplankton which feed on smaller zooplankton. This means they really belong to the third trophic level, secondary consumers, along with the forage fish.

Together, phytoplankton and zooplankton make up most of the plankton in the sea. Plankton is the term applied to any small drifting organisms that float in the sea (Greek planktos = wanderer or drifter). By definition, organisms classified as plankton are unable to swim against ocean currents; they cannot resist the ambient current and control their position. In ocean environments, the first two tropic levels are occupied mainly by plankton. Plankton are divided into producers and consumers. The producers are the phytoplankton (Greek phyton = plant) and the consumers, who eat the phytoplankton, are the zooplankton (Greek zoon = animal).

Level 3

Typical ocean forage fish are small, silvery schooling oily fish such as herring, anchovies and menhaden, and other small, schooling baitfish like capelin, smelts, sand lance, halfbeaks, pollock, butterfish and juvenile rockfish. Herrings are a preeminent forage fish, often marketed as sardines or pilchards.

The term “forage fish” is a term used in fisheries, and is applied also to forage species that are not true fish, but play a significant role as prey for predators. Thus invertebrates such as squid and shrimp are also referred to as "forage fish". Even the tiny shrimp-like creatures called krill, small enough to be eaten by other forage fish, yet large enough to eat the same zooplankton as forage fish, are often classified as "forage fish".[6]


Forage fish utilise the biomass of copepods, mysids and krill in the pelagic zone to become the dominant converters of the enormous ocean production of zooplankton. They are, in turn, central prey items for higher trophic levels. Forage fish may have achieved their dominance because of the way they live in huge, and often extremely fast cruising schools.

Though forage fish are abundant, there are relatively few species. There are more species of primary producers and apex predators in the ocean than there are forage fish.[7]

Level 4

Tuna, billfish

Level 5

Marine trophic index[edit]

"The Marine Trophic Index has been endorsed by the Convention on Biological Diversity as a measure of marine biodiversity. It measures overall ecosystem health and stability, but also serves as a proxy measure for overfishing. The word trophic means “of or relating to nutrition,” so the index is a measure of the richness and abundance of large, higher-trophic-level fish species."[8]

"By examining the change in the Marine Trophic Index over time, the degree to which a county is altering fish stocks in the marine ecosystem is revealed. If the change is negative, it means the overall trophic structure of the marine ecosystem is becoming depleted of larger fish higher up the food chain, and smaller fish are being caught. However, if the change in the Marine Trophic Index is zero or positive, the fishery is either stable or improving. The change in the index is thus an indicator of the sustainability of each country’s fish resources."[8]

"To calculate the Marine Trophic Index, each fish or invertebrate species is assigned a number based on its location in the food chain. Carnivores are assigned high numbers, and herbivores lower ones. The index is calculated from datasets of commercial fish landings by averaging trophic levels for the overall catch.[8][9]

"The term ‘Marine trophic index’ is the Convention on Biological Diversity’s name for the mean trophic level of fisheries landings [and one primary marine biodiversity indicator]. Trophic level measures the position of a species in a food web, starting with ‘producers’ (eg phytoplankton, plants) at level 0, and moving through primary consumers that eat primary producers (level 1) and secondary consumers that eat primary consumers (level 2), and so on. In marine fishes, the trophic levels vary from two to five (top predators)."[10]


Fishing down aquatic webs[edit]

Fishing Down the Food Web
The Problem[11]
  • After decades of over-exploiting fish stocks, the commercial fishing industry is now threatening the very basis of the marine food chain.
  • Having exhausted catches of larger, longer-lived species (e.g., tuna, cod, snapper), fishing fleets are increasingly concentrating on catching smaller, shorter-lived, plankton-eating species (e.g., squid, mackerel and sardines, and invertebrates such as oysters, mussels, and shrimp), which are nearer the bottom of the food chain.
  • As predatory fish are selectively removed from the ocean, they must increasingly rely on lower trophic level species for food. However, the seasonal abundance of these smaller, fast-reproducing species fluctuates greatly and the remaining larger fish are thus exposed to greater variability in their food supply. When commercial fisheries then target these vital species at the base of the food chain, adding to this already delicately balanced situation, they push the entire ecosystem to the brink of collapse.
  • A classic example of such a situation recently occurred in Europe’s North Sea. Norway cod were so overfished that fisherman focused on catching pout. Pout, however, feed on copepods and krill. Krill feed on copepods but so do juvenile cod. As pout were removed, krill populations increased and copepod numbers declined. With the decline of copepods, young cod lost a food source making their path to recovery even more difficult.
  • Ultimately, then, fishing down the food web causes two problems:
    • Lower-level competitors can take advantage of the removal of top-level predators as predatory pressure and competition for food is reduced;
    • As fisheries then target lower-level organisms (i.e., prey fish and invertebrates) predators are increasingly deprived of much of the very food source necessary for population re-establishment.
The Causes[11]
  • On one level, the cause is relatively simple: For decades the world’s commercial fishing fleets have been taking unsustainable amounts of fish and marine life, to the extent that many fish stocks are now declining or even collapsing.
  • The more underlying causes are somewhat more complex. Although it is frequently argued that increases in the global fish catch are the result of a “growing world population,” little of the increased catch from the world fishing fleet finds its way to those peoples where population is increasing most dramatically and where hunger is most marked. Indeed, foreign fishing fleets generally remove fish from the marine waters of those countries for export to the industrialized world.
  • In essence, over-fishing is largely caused by a combination of factors, of which growing human populations is but one. Others include:
    • Consumer demand for more and different fish;
    • Increased technological efficiency in terms of location and catching methods;
    • The globalization of much of the fishing industry and the markets for fishery products;
    • The continuing failure on the part of elected officials, fishery managers and the public to heed scientific warnings about recommended catch levels or the impact of fisheries policies;
    • Government subsidies that encourage the continued building and deployment of greater numbers of larger fishing vessels with ever-more destructive gear;
    • Illegal, unreported and unregulated (IUU) fishing.
The Context[11]
  • The problems of fishing down the food web are but the latest manifestations of a global commercial fisheries industry that has been responsible for over-exploitation of fish populations for decades.
  • According to the Food and Agriculture Organization (FAO) of the United Nations, 47 per cent of major fish stocks are “fully exploited,” with no possibility for expansion; 18 per cent are “over-exploited,” and 10 per cent are “depleted.”
  • A 2003 paper in the prestigious science journal Nature stated that the biomass of predatory fish -- both open ocean species including tuna, swordfish, marlin and large groundfish such as cod, halibut, skates and flounder -- has been reduced to a mere 10% of pre-industrial levels.
  • In addition to direct impacts on target species, commercial fishing fleets continue to damage or obliterate habitat (e.g., by bottom trawling), catch non-target species of marine wildlife (i.e., bycatch or bykill), including non-target fish, sea turtles, seabirds, and marine mammals, and, as explained above, cause breakdowns in broader marine ecosystems.
Further Reading
  • Pauly, D. et al. 1998. Fishing down marine food webs. Science 279: 860-863.
  • Pauly, D. and Watson, R. 2003. Counting the last fish. Scientific American, July: 42-47.
  • Sala, E. et al. 2004. Fishing down coastal food webs in the Gulf of California. Fisheries, March: 19-25.
Definition

Trophic level: Position in the food chain, determined by the number of energy-transfer steps to that level - FishBase.


Fishery collapses[edit]

Collapsed fisheries


Canadian fishing disasters
Some Greenpeace articles
Aquaculture
Timeline
Sustainable fishing


Present situation

"Is rather grave. The marine resources, especially in the north Atlantic, but also in other parts of the world, are in dire strait. In the north Atlantic they have declined very strongly since the mid 70s. For this reason, the fishing fleets have expanded towards low latitudes into the Southern hemisphere. In Europe, about 80 percent of the supplies come from other countries or continents. The expansion of fisheries which became necessary since the 70s and 80s took place along three axes

  • into low latitudes in the Southern hemisphere
  • towards greater depth. Fisheries now deploy trawler at very great depth, beyond one kilometre.
  • the third expansion was into non-traditional species. All kind of things are being landed and marketed now, which people didn't know and didn't use before. This offers the trade opportunities to largely fool people in that they offer substitutes for the species that people expect to find."[12]
Consequences for developing countries

"For or developing countries the implications are very severe. They have the choice between either allowing foreign fleets to fish in the exclusive economic zone, or to export to the developed countries, or they can supply the local markets. they have chosen, and I guess many countries don't have the choice, to supply the markets in the north. This means that fish is not available anymore, with an increasing population, and this is a real problem.[12]

"I don't believe personally that aquaculture can substitute for these missing fish. Outside China, where two-thirds of the world's aquaculture production is generated, aquaculture is mainly based on carnivorous fish. These carnivorous fish are expensive and are consumed mainly in the West. So I don't think aquaculture can substitute at the level of food security for developing countries, and thus I am rather pessimistic about the food security implications of the development in fisheries."[12]

Solutions to preserve the oceans fish stocks.

"Among the solutions about the state of the stock, obviously people have to allow for the stock to rebuild itself, and that means setting up marine protected areas. However the fisheries industry don't like marine protected areas, because they perceive this as a reduction in the fishing grounds. Other sectors of the public will have to be involved. The NGO community will have to be involved in helping towards creating marine protected areas."[12]

"Another thing that will have to be allowed is the modification of the governance of fisheries wherein people will have to get privileged access to fisheries so that they don't act on a competitive basis. This is very true for artisanal fisheries which, right now, are always competing against foreign industrial fleets. If these industrial fleets were removed it would be possible to restructure the artisanal fisheries to supply local markets with good quality fish. That would address the food security question."[12]

The dialogue between fishermen and scientists

"I believe that in the dialogue between fishers and scientists there has been a perception that the fishers are not heard. But actually the problem is that they are heard too much, at least by politicians, and other voices are not heard at all. For example, one voice that is not heard is that of the people who want to maintain, the public at large wants to maintain biodiversity. And the fishers, in effect, don't. Thus the NGO community, the NGOs that argue for the conservation of biodiversity, ought to have a voice as much as the fishing community, which up to now are the only one heard about fisheries problems."[12]

Conclusions

"The conclusion of all this is that we cannot count on the seas to solve our problems on land. This problem of a growing human population, with growing needs and growing incomes and growing appetites for fish, is not a soluble problem. The true solution doesn't have a technical solution. The true solution is that these demands on the sea and on the wild animals are reduced. And that is a question of a change of culture, and eventually in a reduction of our number."[12]

From jellyfish

There is very little data about changes in global jellyfish populations over time, besides "impressions" in the public memory. In most places in the world, scientists have no quantitative data about what jellyfish populations used to be like, or quantitative data about what is happening in the present.[13] Recent speculation about increases in jellyfish populations have been based on no "before" data.

According to Claudia Mills of the University of Washington, increasing frequency of jellyfish blooms globally might be attributed to humans' impact on marine systems. She says that in some locations jellyfish may be filling ecological niches formerly occupied by overfished creatures, but notes that we lack data to show that is indeed true.[13] Jellyfish researcher Marsh Youngbluth further clarifies that "jellyfish feed on the same kinds of prey as adult and young fish, so if fish are removed from the equation, jellyfish are likely to move in."[citation needed]

Some jellyfish populations that have shown clear increases in the past few decades are "invasive" species, newly arrived from other parts of the world: examples of regions with troublesome non-native jellyfish include the Black Sea and the Caspian Sea, the Baltic Sea, the eastern Mediterranean coasts of Egypt and Israel, and the American coast of the Gulf of Mexico.[citation needed] Populations of some invasive species expand rapidly because there are no natural predators in the ecosystem to check their growth. Such blooms would not necessarily reflect overfishing or other environmental problems.

Increased nutrients in the water, ascribed to agricultural runoff, have also been cited as an antecedent to the proliferation of jellyfish. Monty Graham, of the Dauphin Island Sea Lab in Alabama, says that "ecosystems in which there are high levels of nutrients ... provide nourishment for the small organisms on which jellyfish feed. In waters where there is eutrophication, low oxygen levels often result, favoring jellyfish as they thrive in less oxygen-rich water than fish can tolerate. The fact that jellyfish are increasing is a symptom of something happening in the ecosystem."[14]

By sampling sea life in a heavily fished region off the coast of Namibia, researchers found that jellyfish have overtaken fish in terms of biomass. The findings represent a careful, quantitative analysis of what has been called a "jellyfish explosion" following intense fishing in the area in the last few decades. The findings were reported by Andrew Brierley of the University of St. Andrews and his colleagues in the July 11, 2006 issue of the journal Current Biology.[15]

Areas which have been seriously affected by jellyfish blooms include the northern Gulf of Mexico. In that case, Graham states, "Moon jellies have formed a kind of gelatinous net that stretches from end to end across the gulf."[14]

Marine trophic level[edit]

The Marine Food Web[edit]

Notes[edit]

  1. ^ a b c d e f g h i j k l m n o p q r s t What is Marine Biology? MarineBio.org". MarineBio.org. <http://marinebio.org/oceans/marine-biology.asp>. Retrieved: 30 April 2011. Updated: 26 November 2010.
  2. ^ a b Cite error: The named reference Stergiou was invoked but never defined (see the help page).
  3. ^ Fishing Down Marine Food Webs Fishbase.
  4. ^ Mann, D. G. (1999). The species concept in diatoms. Phycologia 38, 437–495.
  5. ^ Biology of Copepods at Carl von Ossietzky University of Oldenburg
  6. ^ Marine Fish Conservation Network: Forage fish: The Most Important Fish in the Sea
  7. ^ Cite error: The named reference NCMC was invoked but never defined (see the help page).
  8. ^ a b c Marine Trophic Index
  9. ^ Yale Center for Environmental Law and Policy: Environmental Performance Index: Marine Trophic Index 2008.
  10. ^ A users’ guide to biodiversity indicators Page 38. European Academy of Science, Advisory Council, 2004.
  11. ^ a b c Ocean briefings: Fishing Down the Food Web SeaWeb.
  12. ^ a b c d e f g Pauly, Daniel (2009) The sea without fish, a reality ! Interview with the project leader of the Sea Around Us Project, University of British Columbia.
  13. ^ a b Mills, C.E. 2001. Jellyfish blooms: are populations increasing globally in response to changing ocean conditions? Hydrobiologia 451: 55-68.
  14. ^ a b The Washington Post, republished in the European Cetacean Bycatch Campaign, Jellyfish “blooms” could be sign of ailing seas, May 6, 2002. Retrieved November 25, 2007.
  15. ^ Lynam, C. and six other authors, 2006. Jellyfish overtake fish in a heavily fished ecosystem. Current Biology 16, no. 13: R492-R493.