I.I. Challenges of Life in the SeaChallenges of Life in the Sea

A.A. SalinitySalinity1.1. Diffusion and OsmosisDiffusion and Osmosis

• Diffusion problematic – leads to loss of important Diffusion problematic – leads to loss of important ionsions

• Selectively permeable cell membrane limits Selectively permeable cell membrane limits movement of certain molecules (large, electrically movement of certain molecules (large, electrically charged) but allow movement of small molecules, charged) but allow movement of small molecules, e.g.e.g. water water

• OsmosisOsmosis – Diffusion of water across selectively – Diffusion of water across selectively permeable membranepermeable membrane

• Water diffuses from region of higher water Water diffuses from region of higher water concentration (lower salt concentration) to concentration (lower salt concentration) to region of lower water concentrationregion of lower water concentration

• Possible to move molecules against Possible to move molecules against concentration gradient by using energy to power concentration gradient by using energy to power active transportactive transport

Fig. 4.13

I.I. Challenges of Life in the SeaChallenges of Life in the Sea

A.A. SalinitySalinity2.2. Regulation of Salt and Water BalanceRegulation of Salt and Water Balance

• OsmoconformersOsmoconformers• Energetically inexpensiveEnergetically inexpensive• Limits distribution to areas with stable Limits distribution to areas with stable

salinity (salinity (Where?Where?))• OsmoregulatorsOsmoregulators

• Expend energy to maintain body fluid Expend energy to maintain body fluid compositioncomposition

• Less constrained by salinity in habitatLess constrained by salinity in habitat• EuryhalineEuryhaline vs.vs. StenohalineStenohaline

Fig. 4.14

Fig. 4.15

I.I. Challenges of Life in the SeaChallenges of Life in the Sea

B.B. TemperatureTemperature• Rates of metabolic reactions double for Rates of metabolic reactions double for

each 10 each 10 ooC increase in temperatureC increase in temperature• Most marine organisms adapted to Most marine organisms adapted to

specific temperature rangespecific temperature range• Species distributions often based on Species distributions often based on

temperature of watertemperature of water• PolarPolar• Cold temperateCold temperate• Subtropical (warm temperate)Subtropical (warm temperate)• TropicalTropical

• EurythermalEurythermal vs.vs. StenothermalStenothermal

Fig. 4.16

I.I. Challenges of Life in the SeaChallenges of Life in the Sea

B.B. TemperatureTemperature• EctothermsEctotherms – Body temperature – Body temperature

essentially determined by temperature of essentially determined by temperature of environmentenvironment

• Often Often poikilothermspoikilotherms (“cold blooded”) (“cold blooded”)• Some species warm certain tissues to improve Some species warm certain tissues to improve

performance (tuna, billfish, some sharks)performance (tuna, billfish, some sharks)• EndothermsEndotherms – Maintain elevated internal – Maintain elevated internal

body temperaturebody temperature• Usually Usually homeothermshomeotherms (“warm blooded”) (“warm blooded”)• Energetically expensiveEnergetically expensive• Insulation may help to conserve heatInsulation may help to conserve heat

• BlubberBlubber• FeathersFeathers• HairHair

I.I. Challenges of Life in the SeaChallenges of Life in the Sea

C.C. Surface-to-Volume RatioSurface-to-Volume Ratio• Organisms exchange heat and substances Organisms exchange heat and substances

across body wallacross body wall• NutrientsNutrients• GasesGases• Waste productsWaste products

• Rate of exchange depends on S/V ratioRate of exchange depends on S/V ratio• Ratio decreases as organism size Ratio decreases as organism size

increases, if shape stays the sameincreases, if shape stays the same• Smaller organisms exchange materials by Smaller organisms exchange materials by

diffusiondiffusion• Larger organisms have special systems to Larger organisms have special systems to

exchange materialsexchange materialsFig. 4.17

II.II. ProkaryotesProkaryotes

A.A. BacteriaBacteria• Many shapes - spheres, coils, rods, ringsMany shapes - spheres, coils, rods, rings• Very small cells (usually less than 1 μm Very small cells (usually less than 1 μm

across)across)• Little known until second half of 20th centuryLittle known until second half of 20th century• Exceptions - 570 to 750 μm diameter in sediments Exceptions - 570 to 750 μm diameter in sediments

(filamentous) and fish guts(filamentous) and fish guts• Rigid cell wallsRigid cell walls

• May reach very high densities under favorable May reach very high densities under favorable conditionsconditions

1.1. Heterotrophic BacteriaHeterotrophic Bacteria• Most are Most are decomposersdecomposers (break down organic (break down organic

material)material)• Important in nutrient recyclingImportant in nutrient recycling• Important components of organisms’ diets, Important components of organisms’ diets,

especially for especially for benthicbenthic organisms organisms

II.II. ProkaryotesProkaryotes

A.A. BacteriaBacteria2.2. Autotrophic BacteriaAutotrophic Bacteria

a.a. Photosynthetic (Photosynthetic (PhotoautotrophicPhotoautotrophic))• Obtain energy from sunlightObtain energy from sunlight• Contain chlorophyll or other photosynthetic Contain chlorophyll or other photosynthetic

pigmentspigments• Important primary producers in open oceanImportant primary producers in open ocean

b.b. Chemosynthetic (Chemosynthetic (ChemoautotrophicChemoautotrophic))• Obtain energy from chemical compoundsObtain energy from chemical compounds - Hydrogen- Hydrogen - Hydrogen sulfide- Hydrogen sulfide - Ammonia- Ammonia

Fig. 4.7

II.II. ProkaryotesProkaryotes

A.A. BacteriaBacteria3.3. Cyanobacteria (Blue-green)Cyanobacteria (Blue-green)

• PhotosyntheticPhotosynthetic• Contain chlorophyll + phycocyanin & Contain chlorophyll + phycocyanin &

phycoerythrinphycoerythrin• Some form filaments or matsSome form filaments or mats• Some similarities to eukaryotic algaeSome similarities to eukaryotic algae

• Contain chlorophyll Contain chlorophyll aa• Produce gaseous OProduce gaseous O22

• May have been first photosynthetic organisms May have been first photosynthetic organisms on earthon earth

• Fossil Fossil stromatolitesstromatolites from 3 billion years ago from 3 billion years ago• Calcareous mounds containing sediment Calcareous mounds containing sediment

and cyanobacteriaand cyanobacteria

http://www.fossilmall.com/Science/About_Stromatolite.htm

http://www.fossilmall.com/Science/About_Stromatolite.htm

II.II. ProkaryotesProkaryotes

A.A. BacteriaBacteria3.3. Cyanobacteria (Blue-green)Cyanobacteria (Blue-green)

• Occur in a variety of habitatsOccur in a variety of habitats• Polar bear hairPolar bear hair• EndolithicEndolithic (inside calcareous rocks and coral (inside calcareous rocks and coral

skeletons)skeletons)• Rocky shorelines (black crusts)Rocky shorelines (black crusts)• EpiphyticEpiphytic (on algae or plants) (on algae or plants)• EndophyticEndophytic (inside algal or plant cells) (inside algal or plant cells)

• Many carry out Many carry out nitrogen fixationnitrogen fixation• Very important processVery important process

• Some forms have lost ability to photosynthesizeSome forms have lost ability to photosynthesize• Live as heterotrophsLive as heterotrophs