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Ecology

Habitat

Depth range based on 19 specimens in 1 taxon.
Water temperature and chemistry ranges based on 18 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 6.814 - 8.734
  Nitrate (umol/L): 12.249 - 18.655
  Salinity (PPS): 34.080 - 34.286
  Oxygen (ml/l): 6.657 - 6.863
  Phosphate (umol/l): 1.016 - 1.359
  Silicate (umol/l): 5.089 - 6.097

Graphical representation

Temperature range (°C): 6.814 - 8.734

Nitrate (umol/L): 12.249 - 18.655

Salinity (PPS): 34.080 - 34.286

Oxygen (ml/l): 6.657 - 6.863

Phosphate (umol/l): 1.016 - 1.359

Silicate (umol/l): 5.089 - 6.097
 
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Pulled support stalks have low flow stress: algae
 

The support stalk (stipe) of seaweed encounters lower flow stresses because it is pulled rather than bent.

       
  "Consider the example of two species of intertidal seaweeds…Lessonia nigrescens and Durvillea antarctica…both species encounter the same range of flow forces, but they differ in their response. L. nigrescens stipes…are bent…D. antarctica…are pulled by moving water. Calculations indicate that stresses in a bent L. nigrescens stipe are roughly 800 times greater than in a pulled D. antarctica stipe of the same dimensions and bearing the same load. These seaweeds illustrate a general principle about organisms bearing loads: stresses are lower if an organism bears a given load in tension than in bending." (Koehl 1984:64)

"In nature, tensile systems are reasonably common and certainly diverse in biological affinities. Among lower plants, the stipes of some large algae are notable. In the Pacific Northwest some algae whose holdfasts are attached to rocks and whose fronds are on the surface have stipes between them well over 100 feet long, stipes that are loaded in tension by waves and tidal currents. Among the higher terrestrial plants we see tensile systems in various epiphytes, tendrils, and dangling fruits. Mussels attach to rocks entirely through the use of tough byssus threads, mainly made of collagen. Even the setae by which the gecko hangs beneath a rock or ceiling are proper tensile systems…Tensile systems ought to scale in an unusual way, something first pointed out by Galileo. Strength doesn't depend on length, so the thickness of your fishing line doesn't have to be adjusted for the depth at which you hang the bait. Cross-sectional area, though, ought to be proportional to load, so diameter ought to scale with the square root of load--load to the 0.5 power. Peterson et al. (1982) looked at several structures normally loaded in tension--fruit stems, algal stipes, and toe-pad setae. They found that in practice, diameter scales with load to the power 0.3 rather than 0.5; cross section thus goes up in proportion to load to the power 0.6, not the 1.0 that seems intuitively reasonable." (Vogel 2003:437)
  Learn more about this functional adaptation.
  • Steven Vogel. 2003. Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press. 580 p.
  • Koehl, M. A. R. 1984. How do benthic organisms withstand moving water. Amer. Zoologist. 24: 57-70.
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Functional adaptation

Leaves resist tearing: brown algae
 

Leaves of brown algae survive extreme mechanical battering because of their sandwiched structure.

   
  The author, speaking about a visit to the rocky coast of central Chile, says, "Whatever man put forth against the power of the sea--wood, concrete, or steel--was destroyed in the course of time. Nothing seemed able to withstand the waves. There was one exception, however: Precisely at the place where at ebb tide the full force of the surf beat against the rock, a lush vegetation of algae was thriving. With each breaker, a storm of movement ran through the jungle of fanlike or snakelike plants, which reached up to 1-2 meters in length. Their arms whirled and undulated in the suction of the current, but they survived the mechanical stress undamaged for months or years. Why weren't the algae torn off, crushed, and pounded to bits against the sharp rock? Such extreme physical stress could only be conquered by a masterful design. When I first tried to get hold of an alga, I was not able, in spite of the greatest effort, to tear off a single strand no thicker than my finger. Neither could I sever it against an edge of the rock. Only when I cut open the broad arm of a brown alga (Durvillaea antarctica) with a razor blade did its secret come to light. It was ideally constructed according to the sandwich method. Its coarse outer skins were braced against each other by a meticulously structured layer of polygonal honeycombs…Sandwich structures are construction elements in which two thin membranes are linked to each other by a very loosely and lightly built supporting layer. The flexible membranes thus become a mechanical unit which is not only much more stable, but also to a great extent protected against local breaks, cracks, and deformations. The sandwich structure owes all these advantages to the loosely assembled filler, which transmits the mechanical forces and distributes them quite evenly over large areas of the membrane surface. In this way, no stress great enough to destroy the membrane can appear anywhere." (Tributsch 1984:35-36)
  Learn more about this functional adaptation.
  • Tributsch, H. 1984. How life learned to live. Cambridge, MA: The MIT Press. 218 p.
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Wikipedia

Durvillaea antarctica

Durvillaea antarctica or Cochayuyo is a large, robust bull kelp species and the dominant seaweed in southern New Zealand and Chile. D. antarctica has a circumpolar distribution between the latitudes of 29°S (in Chile) and 55°S (on Macquarie Island).[1] It is found on exposed shores, especially in the northern parts of its range, and attaches itself with a strong holdfast. D. antarctica, an alga, does not have air bladders, but floats due to a unique honeycomb structure within the alga's blades, which also helps the kelp avoid being damaged by the strong waves.

Morphology[edit]

This cross-section and cut-away view of dried blades shows the honeycomb structure within

The blades of Durvillaea antarctica are green to golden brown with a leathery texture. The honeycomb structure of the blade gives strength and buoyancy.[2] This novel structure is thought to be responsible for the wide distribution of this genus, as the kelp is able to float when its holdfast fails. It can colonise other coastlines in this manner, and has been shown to carry communities of invertebrates across vast ocean distances from one shore to another.[3] It is thought that this 'rafting' with Durvillaea antarctica and other floating seaweeds allowed a wide range of species to recolonise sub-Antarctic shores scoured clean by ice during the last Ice Age.[4]

The holdfast of D. antarctica is large and is very difficult to remove. D. antarctica has to resist forces equivalent to 1100 km/h on land.[5][clarification needed] The holdfast failing is usually the result of worms and molluscs which feed on the tissue because of the sheltered habitat it creates.[6] It is also common for its host rock to be broken off without the holdfast losing its grip, with this contributing significantly to erosion in some areas.[1] Recruitment rates of this species is very low, therefore the ecological impact of harvesting this species is too great.[6]

Durvillea antarctica. Washed up on Sandfly Bay, Otago, New Zealand

Life cycle[edit]

Durvillaea antarctica reproduces sexually by producing egg and sperm that are released into the water. Eggs and sperm are produced on specific sites of the frond. A large individual can produce 100 million eggs in twelve hours.[6] The season when reproduction occurs varies with location, but is generally during winter months.

Dried D. antarctica in a Chilean market

Chilean culture[edit]

Use in cuisine[edit]

In Chilean Cuisine, the Durvillaea antarctica (Quechua: cochayuyo : Cocha: Lake, and yuyo: weed) stem and holdfast, known as hulte is used for different recipes, like salads and stews.

Expression[edit]

The expression remojar el cochayuyo (lit. to soak the cochayuyo) is used in Chilean Spanish to refer to the sexual act.[7] The expression derives from the fact that this algae, that is harvested along Chile's coast, is preserved by being sun-dried and to prepare it then in a dish it needs to be softened up by being soaked in water.

Taxonomy[edit]

The species was first described in 1822,[8] as Fucus antarcticus, and revised in 1892 as Durvillaea antarctica.[9] The genus name Durvillaea was given in memory of the French explorer Jules Dumont d'Urville, while the Latin derived epithet refers to antarctic.[10] Recently, taxonomic revision led to the recognition of a new species, Durvillaea poha, within what was previously considered Durvillaea antarctica. Durvillaea poha is the only other species in the genus to share the honeycombed structure and buoyancy of D. antarctica. D. poha occurs only in southern New Zealand and on some New Zealand islands (including the Auckland and Snares Islands), whereas D. antarctica has a wider distribution, and is found around New Zealand, Chile and the sub-Antarctic islands. In southern New Zealand, D. poha and D. antarctica can be found growing together, although D. poha normally grows higher up or further back on the rock platforms, or in more sheltered bays, where wave force is weaker.[11] D. poha generally has wider fronds than D. antarctica, and can appear more 'orange' across the frond area.

References[edit]

  1. ^ a b Smith, J.M.B. and Bayliss-Smith, T.P. (1998). Kelp-plucking: coastal erosion facilitated by bull-kelp Durvillaea antarctica at subantarctic Macquarie Island, Antarctic Science 10 (4), 431–438. doi:10.1017/S0954102098000522.
  2. ^ Maggy Wassilieff. Seaweed - Bull kelp’s honeycombed structure, Te Ara - the Encyclopedia of New Zealand, Ministry of Culture and Heritage. Updated 2 March 2009. Retrieved 9 March 2010.
  3. ^ Fraser CI, Nikula R & Waters JM (2011) Oceanic rafting of a coastal community. Proceedings of the Royal Society, B, 278:649-655.
  4. ^ Fraser CI, Nikula R, Spencer HG & Waters JM (2009) Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum. Proceedings of the National Academy of Sciences, USA, 106:3249-3253.
  5. ^ Hurd, C (2003). The Living Reef. Nelson, New Zealand: Craig Potton Publishing. 
  6. ^ a b c Bradstock, M (1989). Between the Tides. New Zealand: David Bateman Limited. 
  7. ^ La Ficha Pop, La Cuarta, 31 October 2006.
  8. ^ Choris, L. (1822). Voyage pittoresque autour du monde. Part I. pp. vi + 17, 12 plates. Paris
  9. ^ Hariot, P. (1892). Complément à la flore algologique de la Terre de Feu. Notarisia 7: 1427-1435.
  10. ^ Guiry, M.D.; Guiry, G.M. (2008). "'Durvillaea antarctica'". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. 
  11. ^ Fraser CI, Spencer HG & Waters JM (2012) Durvillaea poha sp. nov. (Fucales, Phaeophyceae): a buoyant southern bull-kelp species endemic to New Zealand. Phycologia, 51:151–156.
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