Читать книгу Life in the Open Ocean - Joseph J. Torres - Страница 19

As a factor governing the distribution of open‐ocean species, temperature is huge. By far, most pelagic species are ectotherms: their internal temperature matches that of their environment. All invertebrates and all but a very few species of fishes are ectotherms. Because of their internal biochemistry, ectothermic species have a range of temperatures that is optimal for their survival and that in turn dictates their range, or distribution, within the open‐ocean ecosystem. In contrast, marine mammals and seabirds are endotherms: they produce and maintain their own body heat. Endothermy confers some independence from the tyranny of ocean temperature. Many species of marine mammals, particularly the great whales, range over huge distances and experience swings from polar to tropical temperatures each year. A few species of fishes, notably the tunas and mackerel sharks, are regional endotherms or heterotherms: capable of trapping the heat produced in their swimming muscle by using a heat exchanger in their circulatory system. The temperature within the muscle reaches temperatures rivaling that of mammals, allowing regional endotherms to be quite effective swimmers indeed.

Temperature in the ocean varies predictably in both the horizontal (latitude and longitude) and vertical (depth) planes. However, to understand why temperature varies with depth and latitude in the way that it does, we need to know a little about ocean circulation. In turn, to understand ocean circulation, we need to have a clear mental picture of the geography of the ocean basins.

Table 1.1 Characteristics of the ocean basins.

	Ocean
	Atlantic	Arctic	Indian	Pacific	Southern
Ocean area (106 km2)	82.22	14.06	73.48	165.38	20.33
Mean depth (m)	3600	1117	3963	4200	4000–5000
Maximum depth (m)	9560	4440	7725	11 034	7235
Location of maximum depth	Puerto Rico Trench	Eurasia Basin	Java Trench	Marianas Trench	South Sandwich Trench