Life in the Open Ocean. Joseph J. Torres

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Life in the Open Ocean - Joseph J. Torres


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important to temperate species that must accommodate changes in temperature associated with seasonal cycles. In most instances, a need for change can be achieved through changes in the biosynthesis of lipids. An example is using enzymes that introduce double bonds into fatty acid chains to make them more suitable for use at cold temperature. Such enzymes are termed desaturases, and they can be up‐regulated quickly (Hochachka and Somero 2002).

Carbon atoms Common name Empirical formula Chemical structure Melting point (°C)
Saturated fatty acids
3 Propionic acid C3H6O2 CH3CH2COOH −22
12 Lauric acid C12H24O2 CH3(CH2)10COOH 44
14 Myristic acid C14H25O2 CH3(CH2)12COOH 54
16 Palmitic acid C16H32O2 CH3(CH2)14COOH 63
18 Stearic acid C18H36O2 CH3(CH2)16COOH 70
20 Arachidic acid C20H40O2 CH3(CH2)18COOH 75
Unsaturated fatty acids
16 Palmitoleic acid C16H30O2 CH3(CH2)5CH=CH(CH2)7COOH −0.5
18 Oleic acid C18H34O2 CH3(CH2)7CH=CH(CH2)7COOH 13
18 Elaidic acid C18H34O2 CH3(CH2)7CH=CH(CH2)7COOH 13
18 Linoleic acid C18H32O2 CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH −5
18 Linolenic acid C18H30O2 CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH −10
20 Arachidonic acid C20H32O2 CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH −50
Schematic illustration of the relationship between adaptation temperature and percentage of unsaturated acyl chains in synaptosomal phospholipids of differently adapted vertebrates.

      Source: Hochachka and Somero (2002), figure 7.27 (p. 372). Reproduced with the permission of Oxford University Press.

Schematic illustration of temperature acclimation and phospholipid class.

      Source: Hazel and Carpenter (1985), figure 4 (p. 599). Reproduced with the permission of Springer.

      Even though pressure is the most predictable variable in the ocean, increasing by 1 atm with every 10 m increase in depth, pressure is probably the variable most difficult to intuitively understand. Ocean pressure evokes thoughts of dark and forbidding depths, of submarine movies in which the captain and heroic crew must take their craft to depths far greater than she was built to withstand, to there lie on the bottom, evade the enemy, and hope to survive. The great pressure causes the sub to creak and groan, bolts to pop like bullets out of the hull, and leaks to sprout before the ordeal can be successfully ended. However, World War II submarines could not get very deep at all, <300 m, and even modern nuclear subs do not get out of the mesopelagic zone (200–1000 m). Our view on pressure from those movies is one where pressure is acting on gas‐filled spaces. A submarine is quite a large gas‐filled space and must be immensely strong to withstand even the modest pressure of a dive to 100 m: 11 atm, 162 psi, or 11 143 kPa. In point of fact, most of the species that live under pressure do not have gas‐filled spaces, and thus the effects of pressure are far more subtle, especially in the upper 1000 m where much of the ocean’s pelagic biomass resides. In our mind’s eye though, the pressure associated with even the average depth of the ocean must be a formidable challenge to


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