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. Response • Environmental change • Receptors (antennae, tentacles, protein systems) • Transfer systems - nervous connections to muscle systems, endocrine systems • Response must be a response to change that maximizes fitness

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

4. Acclimation, Regulation, and Conformance • Acclimation: response followed by new equilibrium • Regulation: maintenance of constancy despite environmental change • Conformance: internal state changes to match external environmental change

5. Acclimation, Regulation, and Conformance

6. Scope for Growth • Physiological condition reflected in resources available for growth • Metabolic cost • Measure of energy reserves: Scope for growth minus excess energy beyond that needed for maintenance

7. Widdows, J. et al. 1988, Marine Ecology Progress Series Scope for Growth A mussel has less scope for growth with less food and higher temperature

8. Dahlhoff et al. 2002 Integrative and Comparative Biology 42:862-71 Scope for Growth Results from experiment with a marine mussel RNA is a measure of protein synthesis or vigor of growth-activity

9. Mortality Differences Show Physiological Differences

10. Temperature • Temperature variation is common in marine environment: Latitudinal temperature gradient, regional differences Seasonal temperature change Short term changes (e.g., weather changes, tidal changes)

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

12. Temperature • 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

13. Temperature • 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

14. Temperature • 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

15. Temperature Countercurrent heat exchange machine

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

18. Tuna use countercurrent exchange of arterioles and veinlets to retain heat:

19. Temperature Poikilotherms - can compensate for temperatures by means of acclimation; can stabilize metabolic rate over a wide range of intermediate temperature

20. Temperature • 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 • 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 and glycopeptides, which function as antifreeze but at very low concentrations (no effect on osmotic pressure), bind to incipient ice crystals to prevent further growth

22. Pagothenia borchgrevinski

23. Temperature • 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)

24. Temperature • Heat Shock - 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

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

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

27. Temperature • Survival and reproductive effects at ends of a latitudinal range of a species

28. Salinity • Variation of salinity: estuaries, tide pools • Many marine groups intolerant of salinity change (low salinity): echinoderms, protobranch bivalves • Populations in open ocean often less tolerant of salinity change: e.g., pelagic planktonic organisms • Regulation of vertebrates of ionic concentrations to very narrow variation, other groups show more variation and response to external change

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

30. Salinity • 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

31. Salinity • 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

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

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

34. Salinity • 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

35. Salinity • Most marine organisms have ionic concentrations of cell constituents similar to seawater. Why?

36. Recap • Diffusion - problem of regulation of ion concentration • Osmosis - problem of regulation of cell volume

37. Salinity Methods of Response to Salinity • Ion regulation • Cell volume regulation • Combination of ion and cell volume regulation • Or: poor ion or cell volume regulation

38. Salinity Ion Regulation • Done by many species, but best by crustacea (e.g., crabs), vertebrates • Accomplished when isolation of body possible (e.g., crab carapace) so exchange and regulation localized • Poorly accomplished by species with poor isolation (e.g., echinoderms, sea anemones)

39. Salinity Cell Volume Regulation • Osmolytes: organic substitute for inorganic ions - allows regulation of cell volume and maintenance of inorganic ion concentrations Free amino acids used by many invertebrates, bacteria, hagfishes. Use uncharged 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

40. Salinity Crab Salinity Responses • Blue crab Callinectes sapidus and shore crab Carcinus maenas  Above 25 o/oo blood ion concentration tracks ambient water, uses osmolyte variation to regulate cell volume  Below 25 o/oo, strong regulation of Na and Cl, down to low salinities, probably hormone regulated  Gill is the focal organ involved in regulation and the various Na pumps are crucial regulators

41. Regulation of sodium in hemolymph in an estuarine crab like the blue crab Callinectes sapidus. Notice that Na is regulated above external concentration (red line) at low concentration but converges to ambient (1:1 line) at higher external concentrations. See Mantel, L.H., and Farmer, L.L., 1983 in L. H. Mantel, Biology of Crustacea, v. 5, pp. 53-161, Academic Press

42. See Towle, D.W. 1997 Amer. Zool. 37:575-584

43. Salinity • Bony fishes - osmotic regulation: cell fluids = 1/3 strength of seawater

44. Oxygen • oxygen - synthesis 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 Seasonaloxygen changes as in estuaries: hypoxic zones, “dead zones”

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

46. Oxygen • Nearly all animals are obligate aerobes, but many animals have a mix of metabolic pathways with and without use of oxygen ANAEROBIC PATHWAYS: • Vertebrates and some invertebrates use glycolysis - breakdown product is lactic acid, which accumulates in muscle tissue • Many invertebrates have alanine and succinic acid as anaerobic breakdown products

47. Oxygen • Oxygen uptake mechanisms: diffusion - organisms a few mm thick feathery gills - 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

48. Oxygen Countercurrent exchange uptake In fish gills

49. Oxygen • 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, arthropods, annelids, nematodes, flatworms, protozoa)

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