BIEB132_L5_TempSalinity

BIEB132_L5_TempSalinity - BIEB 132 Lecture 5 Adaptations to...

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BIEB 132: Lecture 5 Adaptations to environmental temperature and salinity Required reading : Levinton, Marine Biology (3rd ed) Chapter 4, pp 85-108. Recommended reading: Barry et al. 1995. Climate-related, long-term faunal changes in a California rocky intertidal community. Science 267: 672 -675
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Adaptations of marine organisms to changes in temperature and salinity As terrestrial organisms, we are used to rapid changes in temperature and humidity. Such changes are not characteristic of aquatic habitats, especially in the ocean. As a consequence, many marine organisms have narrow physiological tolerances.
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View of deep sea North Pacific South Atlantic ~ 2 o C ~ 2 o C
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Intertidal zone ~ 0-35+ o C One of the exceptions:
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Some marine habitats show great changes in temperature on various time scales Surface waters in some places- seasonal change Gulf of Mexico Altantic coast Intertidal zone - diurnal change Tidepools Mudflats
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FIG. 4.1 (a) Acclimation response of oxygen consumption following a change of temperature. (b) Response of body fluid salt content to environmental salinity variation of a regulator and of a conformer. Organismal Responses to Environmental Change
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Higher temperatures result in higher metabolic rates “Scope for growth” = Energy assimilated - energy needed for (food) maintenance metabolism High scope for growth --> growth and reproduction can occur Negative scope for growth --> animal is consuming reserves and will ultimately die when reserves are depleted FIG. 4.2 Scope for growth of a mussel under conditions of high, medium, and low food rations and varying temperature. Note that, as temperature increases or food decreases beyond a certain point, scope for growth, in terms of energy balance, falls below zero.
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Temperature tolerance Often differs among co-occurring species Often differs geographically within species (closer to thermal limits at geographic extremes) -differences can be genetic -often due to acclimation FIG. 4.3 One can measure differences in temperature tolerance by exposing groups of animals to different temperatures and measuring mortality after 24 hours. The LD 50 is the temperature at which 50 percent cumulative mortality occurs. In this example comparing eastern U.S. arthropods, a mysid shrimp, Neomysis americana , was taken from near the southern end of its geographic range. It proves to be less tolerant of high temperature than the mud crab Rhithropanopeus harrisii . (Modified from Mihursky and Kennedy, 1967.)
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On a seasonal basis, many organisms show adjustments of their metabolic rates (otherwise the rate may be too high in summer or too low in winter). Such acclimation involves a number of mechanisms: changes in gene expression changes in membrane lipids Note: Same metabolic rate at low temp in winter and at high temp in the summer
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Temperature impacts different processes differently: Thermal tolerance data for selected seaweeds (Langford et al 1998) Species Lethal temperature ( ° C) Reproduction limit temperature ( ° C) Chondrus crispus 28 15 Cladophora spp . 30-35 25 Chorda filum 23 15
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