Aspects of Stress in the Tropical Marine Environment

Abstract

Publisher Summary This chapter focuses on the aspects of stress in the tropical marine environment. There have been many studies of the tropical environment, many of them concerned with theories of the cause of the high speciation there; most of these have been focused on the land, and particularly the rain forest. The present study arises from the observation that it is much more difficult to keep organisms alive in the laboratory in the tropics than it is in temperate climates. Departure from optimal conditions for one environmental factor tends to reduce the tolerance range of a species for other factors. Throughout this chapter, the terms polar, temperate , and tropical have been used to refer to cold, intermediate, and warm seas without implying correspondence with well-defined zoogeographic regions. Physical aspects—such as temperature, salinity, radiation, and tides along with biological aspects—such as temperature tolerance, intertidal zonation, and critical levels—are discussed. The range of temperature tolerance is low in the tropics. Individual species there occupy a smaller fraction of the intertidal zone, and critical levels are shifted downwards. Tropical growth rates are high but very variable and there is less growth after sexual maturity than in mid-latitudes. The seasonal pattern of tropical growth is very variable. Longevity is less. The proportion of large species is less in the tropics, although there are some giant species there. Adaptation to the tropics may involve slowed growth, great size, and extended vertical intertidal range. Those species that show such adaptation are unable to live outside the tropics. These aspects seem to indicate that tropical seas are regions of increased stress.