4 The Chemical and Physical Environment

1. 4 The Chemical and Physical Environment Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton

2. Measures of Physiological Performance • Consider an organism that is faced with an environmental change • First, it must have receptors to sense the change • Information must be transferred to the systems that generate an adaptive response - response that improves fitness

3. Measures of Physiological Performance 2 • Types of adaptive response:  Behavioral  Physiological (cellular changes at large systemic level)  Biochemical (changes of concentrations of enzymes, ions within specific cell types)

4. Acclimation, Regulation, and Conformance • Acclimation: Following an environmental change, organism responds, perhaps strongly, at first, but then internal state changes and organism reaches a new equilbrium - process is acclimation

5. Acclimation, Regulation, and Conformance 2 • Regulation: The organism maintains a constant state within the body, despite variation in the external environment

6. Acclimation, Regulation, and Conformance 3 • Conformance: Environmental change in the external environment might be followed by the internal state of an organism matching the environmental change

7. Acclimation, Regulation, and Conformance 4

8. Scope for Growth 1 • Physiological condition will be reflected in resources available for growth • Greater the cost for metabolism (reactions in cells that cost energy), the less available to invest in growth and reproduction • Scope for growth are the resources available beyond the maintenance metabolism (= a positive energy balance)

9. Scope for Growth 2 A mussel has less scope for growth with less food and higher temperature

10. Mortality differences show physiological differences Rhithropanopeus harisii Neomysis americana Mortality (%) 50 % mortality line Test temperature °C Mortality test: R. harisii is more temperature tolerant than N. americana

11. Temperature 1 • Temperature variation is common in marine environment: Latitudinal temperature gradient can be very pronounced Seasonal temperature change common Short term changes (e.g. weather changes, tidal changes)

12. Temperature 2 • Temperature regulation: Homeotherms - regulate body temperature, usually higher than ambient Poikilotherms - do not regulate body temperature

13. Temperature 3 • Temperature regulation: Homeotherms - advantage of constancy of cellular chemical reactions, disadvantage of heat loss Poikilotherms - advantage of no cost of keeping temperature constant and high, but at the price of metabolic efficiency

14. Temperature 4 • Heat gain - problem for poikilotherms in intertidal zone at low tide or tidal pools on a hot day Circulation of body fluids - brings heat to surface of body so it can be dissipated Evaporation - also allows heat loss to avoid overheating

15. Temperature 5 • Heat loss - problem for homeotherms who maintain high body temperatures Insulation - used by many vertebrates (blubber in whales, feathers in birds) Countercurrent heat exchange - circulating venous and arterial blood in opposite directions while vessels are in contact to reduce heat loss

16. Temperature 6 Countercurrent heat exchange - Heating Chamber 37°C 28 °C 30 °C 32 °C 34 °C 36 °C 27°C 29 °C 31 °C 33 °C 35 °C 37 °C Example of countercurrent heat retention

17. Temperature 7 Countercurrent heat exchange in dolphin limb - artery is surrounded by veinlets, which return heat

18. Temperature 8 Poikilotherms - can compensate for temperatures by means of acclimation; can stabilize metabolic rate over a wide range of intermediate temperature Metabolic rate Stabilization of metabolism over wide range of temperature Temperature

19. Temperature 9 Seasonal acclimation of poikilotherms - shift from winter to summer relation of metabolic rate to temperature Winter-acclimated Metabolic rate Summer-acclimated Temperature

20. Temperature 10 • Evolution of temperature tolerance: Species evolve differences in temperature tolerance, e.g., Antarctic species may not be able to survive waters warmer than 10 C Populations living along a latitudinal gradient might evolve local physiological races, with different temperature responses

21. Temperature 11 • Freezing - a problem in winter in some habitats and in high latitudes where sea ice forms, can destroy cells as cell cytosol freezes Some fish have glycoproteins, which function as antifreeze

22. Temperature 12 • Heat Shock - has effects on physiological integration of biochemical reactions in cells, can denature proteins that cannot function at high temperature (unfolding of three-dimensional structure, which destroys binding with substrates)

23. Temperature 13 • Heat Shock 2 - heat shock proteins - are formed during heat stress, which forestall unfolding of protein 3D structure ubiquitin - low molecular weight protein that binds to degraded proteins, which are then degraded by intracellular proteolytic enzymes

24. Temperature 14 • Heat Shock 3 - Disruption of membranes - heat shock disrupts packing of structural phospholipids in cell membranes, which disrupts transport of ions, other cell functions

25. Temperature 15 • Seasonal extremes of temperature affect both activity and reproduction • Effects are different at northern and southern limits of geographic range

26. Temperature 16 • Survival and reproductive effects at ends of a latitudinal range of a species Winter Survival limiting Reproduction limiting Summer High latitude Low latitude

27. Salinity 1 • Salinity change affects organisms because of the processes of diffusion and osmosis

28. Salinity 2 • Osmosis - movement of pure water across a membrane permeable to water, owing to difference in total dissolved material on either side of membrane solute

29. Salinity 3 • Osmosis - movement of pure water across a membrane permeable to water, owing to difference in total dissolved material on either side of membrane • If salt content differs on either side of a membrane, osmotic pressure is created, water moves across in direction of higher salt content

30. Salinity 4 • Example of osmosis problem - animal with a certain cellular salt content is placed in water with lower salinity: water will enter animal if it is permeable - cell volume will increase, creating stress

31. Salinity 5 • Experiment - Place sipunculid Golfingia gouldii in diluted seawater. At first volume increases, but then worm excretes salts through nephridiopores, regulating volume back 5 0 % Body volume change 1 2 Time (hours)

32. Salinity 6 • Diffusion - random movement of dissolved substances across a permeable membrane; tends to equalize concentrations

33. Salinity 7 • Diffusion - random movement of dissolved substances across a permeable membrane; tends to equalize concentrations • Problem - diffusion makes it difficult to regulate concentration of physiologically important ions such as calcium, sodium, potassium

34. Salinity 8 • Most marine organisms have ionic concentrations of cell constituents similar to seawater

35. Salinity 9 • Organismal responses to changing salinity: Organic osmolytes (e.g., free amino acids used by invertebrates) used to counteract osmotic problems. Used to avoid using inorganic ions (e.g., Na) which are physiologically active.

36. Salinity 10 • Osmolytes: Free amino acids used by many invertebrates, bacteria, hagfishes. Use amino acids that have little effect on protein function (e.g., glycine, alanine, taurine) Urea used by sharks, coelacanths Glycerol, Mannitol, Sucrose used by seaweeds, unicellular algae

37. Salinity 11 • Bony fishes - have overall salt concentrations of body fluids of 1/3 strength of regular seawater. Creates continual osmotic problem of water loss Fish must drink continuously Gills actively secrete salts Sharks employ urea to maintain osmotic balance

38. Salinity 12 • Bony fishes - osmotic regulation

39. Oxygen 1 • Most marine organisms require oxygen for manufacture of necessary reserves of ATP, energy source in cells • Some habitats are low on oxygen - Low tide for many intertidal animals Within sediment - often anoxic pore water Oxygen minimum layers in water column - where organic matter accumulates at some depths

40. Oxygen 2 • Oxygen consumption increases with increasing body mass, but weight specific oxygen consumption rate declines with increasing total body mass

41. Oxygen 3 • Oxygen consumption is greater in animals with greater activity

42. Oxygen 4 • Nearly all animals are obligate aerobes, but many animals have a mix of metabolic pathways with and without use of oxygen

43. Oxygen 5 • Many animals use a variety of means of breaking down carbohydrates without oxygen: • Vertebrates use glycolysis - breakdown product is lactic acid, which accumulates in muscle tissue • Invertebrates have alanine and succinic acid as anaerobic breakdown products

44. Oxygen 6 • Oxygen uptake mechanisms: Animals only a few millimeters thick rely upon diffusion for oxygen uptake Larger animals use feathery gills with high surface area to absorb oxygen; mammals have lungs with enormous surface areas to take up oxygen Larger animals have circulatory systems that circulate oxygen to needy tissues. Many have oxygen-carrying blood pigments

45. Oxygen 7 • Blood pigments: substances that greatly increase blood capacity for transporting oxygen

46. Oxygen 8 • Blood pigments: substances that greatly increase blood capacity for transporting oxygen Hemocyanin - copper-containing protein, found in molluscs, arthropods Hemerythrin - iron-containing protein, always in cells, found in sipunculids, some polychaetes, prapulids, brachiopods Chlorocruorin - iron-containing protein, found in some polychaetes Hemoglobin - protein unit (globin) and iron-bearing unit (heme), found in many phyla(chordates, molluscs, arthorpods, annelids, nematodes, flatworms, protozoa)

47. Oxygen 9 • Oxygen binding of hemoglobin (Hb): Hb + O2 HbO2

48. Oxygen 10 • Oxygen dissociation curve showing percent of Hb in blood bound to O2 100 50 0 % saturation of Pigment by O2 0 50 100 Oxygen tension (mm Hg)

49. Oxygen 11 • Hb ability to hold oxygen decreases with decreasing pH - Bohr effect

50. Oxygen 12 • Hb ability to hold oxygen decreases with decreasing pH - Bohr effect • pH is less near capillaries that are starved for oxygen, owing to presence of CO2 released from cells - Hb drops oxygen, which diffuses into cells