Chemical and Physical Environment

Adaptive responses of marine organisms

  1. Behavioral - Change at organismal level

  2. Physiological - systemic cellular changes

  3. Biochemical - changes of chemicals ex. ions within specific cell types

  4. Gene regulation

Acclimation - Response followed by new equilibrium

Regulation - maintenance of constant internal state despite environmental change → regulators

Conformance - Internal state changes to match external environmental change → conformers

Temperature - Temperature changes a lot in marine environments.

Homeotherms regulate body temps, temperature is usually higher than ambient.

  • Pro: More activity - reactions go faster.

  • Con: Takes more energy to maintain temperature

Poikilotherms do not regulate body temperature.

  • Pro: More energy efficient - needs less food

  • Con: Limited adaptability

Issues with temperature

  • Heat gain - Issue for poikilotherms in intertidal zones at low tide. Can circulate body fluids which brings heat to the surface of the body, can also evaporate

  • Heat loss - Issue for homeotherms, can use insulation (ex. blubber) and countercurrent heat exchange.

Poikilotherms can acclimate to a wide range of temperatures by stabilizing their metabolic rate. Fish that have specialized to a certain temperature/light/salinity are called physiological races or ecotypes. They have to be differentially acclimated and genetically adapted.

Extreme Temperature Adaptations

  • Freezing: Glycoproteins and glycopeptides - essentially Antifreeze in the cell. At low concentrations they can bind to ice crystals to prevent freezing (ex. Pagothenia borchgrevinski)

  • Heat shock: Heat shock proteins and ubiquitin. Heat shock proteins keep the cell working. Ubiquitin binds to degraded proteins and recycles them to make heat shock proteins.

LD50: Measurement of mortality to show physiological differences.

Salinity - Salinity varies. Ex: Estuaries and tide pools

Echidnoderms, Protobranch bilvalves, vertebrates, and open ocean populations are intolerant to salinity change.

Diffusion - regulation of ion concentration

Osmosis - regulation of cell volume crossing a selectively permeable cell membrane, mostly water. When salt content differs on either side of a membrane, osmotic pressure is created.

  • Ions in organisms want to go out into the dilute world.

Ion regulation: Osmolytes are organic substitutes for inorganic ions. Allows regulation of cell volume and maintenance of inorganic ion concentrations. Ex. Free amino acids

  • Freshwater fish vs marine fish: Marine fish have too much salt so it has concentrated salty urine and secretes salt through its gills. Freshwater fish need more salt so they pee a lot and absorb salt.

  • Reptiles and sea birds: Secrete salt through tears

Oxygen

Use of oxygen yields ATP (energy currency of cells). Low oxygen is common in sediments. Rich oxygen is common in surface waters and near phytoplankton.

Oxygen Uptake mechanisms

  • Diffusion - thin skin

  • Feathery gills - maximizing surface area. Also have countercurrent exchange uptake

  • Mammals have lungs

  • Larger animals have circulatory systems and oxygen carrying blood pigments

Anaerobic pathways - only 10% as efficient

  • Glycolysis generates energy - breakdown product is lactic acid which makes muscle. Mostly used by vertebrates

  • Alanine and succinic acid - makes ATP but is less efficient. Used by invertebrates

Blood Pigments: key substances in transporting oxygen via blood

  • Hemocyanin - protein contains Copper, mollusks and arthropods

  • Hemerythrin - protein contains Iron

  • Chlorocruorin - protein contains Iron

  • Hemoglobin - iron-bearing unit

Bohr effect: Hemoglobin’s ability to hold oxygen decreases with decreasing pH.