Marine Biology - Lecture notes 5 PDF

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Dr. Kris Karnauskas...

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Marine Biology Monday, July 27, 2020

14:48

Life in the Ocean is a continuum of size, from very teeny to very large Definitions • Plankton - drift or swim weakly • Nekton - actually swim • Phytoplankton - plant ○ Most are photosynthetic autotrophs (plant; flee-floating; takes light in; makes their own energy) • Zooplankton - animal Commonalities • Inability to move themselves horizontally, consistently • Not an evolutionary classification, but a way of life Big Concepts: Life in the Ocean • Life has surprising unity, despite diversity • Life and complexity is all about energy flows • Life is also about cycling a few elements around • Primary productivity is where it all begins • Life has a close dependence on the environment • Life is classifiable in many useful ways What Distinguishes Life From Non-life? • Ability to capture, store, and transmit energy • Ability to reproduce • **Not composition or outward appearance … but the ability to manipulate energy A Few Observations About the UNITY of Life • All species share underlying mechanisms for ○ Capture and storage of energy ○ Manufacturing proteins ○ Transmitting information between generations • 99% of all biomass on Earth is made up of C, N, O, and H Key Points about Evolution • Generation after generation (over ~4 bn years), organisms… ○ Change to fit the physical and chemical environment ○ Become more efficient at extracting energy from the environment ○ Colonize virtually every location on Earth capable of sustaining them ○ Study themselves through scientific logic • Adaptation: the accumulation of beneficial, inheritable, structural, or behavioral traits over generations • Species: group of inter-breeding organisms that are reproductively isolated (new species form via isolation) • The environment isn't right for the organisms; rather, the organisms are right for the environment! Darwin & Natural Selection • In any group of organisms, more offspring are produced than can survive to reproduction age

• Random variations occur in all organisms. Some of these traits are inheritable - they can be passed onto offspring • Some inheritable trait s make an organism better suited to its environment (but most do not) • Because bearers of favorable traits are more likely to survive, they are also more likely to reproduce successfully than bearers of unfavorable traits. Favorable traits tend to accumulate in the population - they are selected. Unfavorable traits are weeded out by competition • The physical and biological (natural) environment itself does the selection. Favorable traits that constitute to the organism's success show up more often in succeeding generations (if the environment stays the same). If the environment changes, other traits will become favorable Natural Selection • Mutation creates variation • Unfavorable mutations selected against • Reproduction and mutation occur • Favorable mutations more likely to survive • ..and reproduce ○ Process ▪ Overproduction □ Every species tends to produce more individuals that can survive to maturity ▪ Variation □ The individuals of a population have many characteristics that differ ▪ Selection □ Some individuals survive longer and reproduce more than others do ▪ Adaptation □ The traits of those individuals that survive and reproduce will become more common in a population

Convergent Evolution • Similar traits (including physical features) selected for independently in different species by a common/shared environment • Results in superficially similar (looking organisms) Primary Productivity • The synthesis of organic material from inorganic substances by photosynthesis (or chemosynthesis) • Immediate product is glucose (carbohydrate) • Source of carbon is CO2 • Units are grams of C per square meter per year (gC/m^2/yr) • Phytoplankton -> produces 90-96% of all carbohydrates in the ocean ○ When a producer binds C into a carbohydrate, it's consumed or metabolized by the producer itself, or its consumed by heterotrophs that grace on the primary producers • Oceanic productivity: the incorporation of carbon atoms into carbohydrates - is measured in grams of carbon bound into carbohydrates per square meter of ocean surface are per year (gC/m^ 2/yr) Sea-to-Air Exchange of CO2 • Air/sea CO2 flux is a function of temperature, surface concentration, and circulation • CO2 more soluble in cold water • The tropical Pacific is an area of natural CO2 outgassing to the atmosphere, but is an important sink of anthropogenic CO2 The Marine Carbon Cycle • Respiration, volcanic eruptions; burning of fossil fuels

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CO2 in the atmosphere CO2 flux across air-sea surface Primary production "fixes" CO2 Primary producers consumed by heterotrophs ○ Incorporated into body for growth (~45%) ▪ Dies and sinks (~99% of turned back into CO2 before it even reaches the sea floor) ○ Respired by heterotrophs (~45%) ○ Excreted/wasted (DOC) (~10%)

Periodic Table of the Elements • 23/107 elements make up all of life on Earth • Only 4 elements make up 99% of all biomass on Earth: C, H, N, O • These elements make up classes of biological chemicals common to all life on Earth: carbohydrates, lipids, proteins, and nucleic acids (i.e. DNA) The Ocean C Pumps • Biological pump (pumps Carbon downward in ocean through several levels of productivity) • Carbonate pump (ends with photosynthesis of shell-growing of marine organisms --> carbon hidden and sequestered from atmosphere for a while. Takes CO2 out of the atmosphere, out of the surface ocean, and bury it into the bottom) • Solubility pump (moves Carbon downward) ○ If the world ocean were to warm, it would be a positive feedback loop (warmer water means less absorbed CO2 --> less CO2 in the ocean) The Redfield Ratio • Tells us the relative abundance of carbon and some key macronutrients • C:N:P = 106:16:1 • Empirically determined by chemical measurements around the world • Extremely useful - helps us understand what is "limiting" productivity in a marine environment Defining Characteristics of Marine Organisms • Autotrophic vs. heterotrophic ○ Auto: "takes care of itself" ○ Hetero: "needs something else for help" • Ectothermic vs. endothermic ○ Ecto: cold blooded, internal body temp ~ water temp (i.e. sharks) ○ Endo: warm blooded, internal body temp > water temp (i.e. whales) How and Why Do We Study Phytoplankton? • Systemic, large-scale study of plankton goes back to the German "Meteor" Expedition (1925) • Primary tool: plankton nets • Also need to now the volume of water sampled (if you want to know plankton species concentrations) • CLASSIFY BY SIZE Phytoplankton • Phytoplankton only occupy "one trillionth" • Cut an inch a million times… • Cannot see in light-based microscopes • Small, but very abundant (100 million in every liter of seawater - just about everywhere) • Cyanobacteria --> "naked photosynthesis machines" • Able to absorb dim, blue light deeper within the photic zone • Coccolithophores have plates (coccoliths) to reflect light (if shallow)

Compensation Depth • Photosynthesis - PRODUCTION of carbs and O2 • Respiration - CONSUMPTION of carbs and O2 Zooplankton • Heterotrophic plankton (drifters that eat primary producers) • Thus, they're primary consumers • Most numerous of all primary consumers in the ocean • Graze on ○ Larger cyanobacteria (picoplankton) ○ Diatoms (microplankton) ○ Dinoflagellates (microplankton) ○ Other phytoplankton • The total biomass of zooplankton is only ~20% of that of phytoplankton Copepods • Tiny, shrimplike, crustacean animals • About 1/2 mm • Comprise ~70% of the larger zooplankton • Most abundant and widely distributed animal in the world Planktons • Holoplankton ○ Spend all of life as plankton (drifter) ○ Most zooplankton are holoplankton • Meroplankton ○ Plankton as juveniles ○ Eventually adopt either benthic or nektonic lifestyle ○ Examples: crabs, barnacles, clams, sea stars, tuna Krill • Pelagic (open-water) arthropods ○ Arthropods: invertebrate, exoskeleton, segmented body, jointed appendages • One of the most important zooplankton

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Keystone species of Antarctic ecosystem Grazes on diatoms in Southern Ocean Eaten by big whales (filter feeders) More biomass than Earth's human population! Vertical migrations ○ Krill move up and down daily, 10-100 meters ○ This movement can mix nutrients up from below the nutricline!

Seaweed • Multicellular • Primary producers (photosynthetic) • 1-5% of world ocean primary productivity • Up to 200 feet long (extreme case) • Can grow 20 inches in a day • Must live Euphotic zone • Extremely high productivity (even leaks 1/2) • Environmental difficulties ○ Strong currents ○ Intertidal -> drying, sunlight ○ Lashed against rocks • Adaptations ○ Flexible ○ Slick ○ Able to absorb shock ○ Streamlined (aerodynamic) ○ Strong Zones by Location • Classifying marine organisms by location (and light*) ○ Pelagic (open water) ▪ Neritic (over continental shelf) ▪ Oceanic (beyond continental shelf) □ Epipelagic (photic zone) □ Mesopelagic (aphotic zone) □ Bathypelagic (aphotic zone) □ Abyssopelagic (aphotic zone) Benthic (ocean bottom) ○ ▪ Littoral (intertidal) ▪ Sublittoral □ Inner (near shore) □ Outer (to edge of continental shelf) ▪ Bathyal (the slopes) ▪ Abyssal (deep ocean floor) ▪ Hadal (trenches) Physical Factors • Any aspect of the physical or chemical environment that affects living organisms • Some factors for marine life ○ Temperature ○ Acidity (pH) ○ Toxin levels ○ Light ○ Dissolved nutrients

○ Salinity ○ Dissolved gases ○ Hydrostatic pressure (the weight of the still water above you) • Some "biological factors" ○ Diffusion (passive) ○ Osmosis (a form of diffusion) ○ Active transport • "Limiting" factors ○ Anything that is too much or too little to support the function of an organism Light • Necessary for photosynthesis by autotrophs • Tough journey for sunlight from the very get-go • WHERE THERE'S MORE PHOTOSYNTHESIS = EUPHOTIC DEPTH IS SHORTER Temperature • Influences the metabolic rate of organisms • Rate at which chemical reactions (releasing energy) occur depends on molecular vibrations (which is a def. of temperature) since agitation brings reactants together • For every 10 degree Celsius warmer, a marine organism's metabolic rate doubles ○ Ectothermic --> "cold-blooded" --> same T as surroundings --> majority of marine organisms. Raise temperature --> grow faster, faster HR, reproduce earlier, swim faster, shorter life ○ Endothermic --> "warm-blooded". Thermal regulation mechanisms (shivering, sweating, etc.). Wide range of environments with little variation in body/internal temperature Dissolved Nutrients • Required for the production of organic matter • Inorganic nutrients required for primary productivity (PP) are N and P (actually, nitrate and phosphate) • Recall the extremely useful Redfield Ratio • N and P depleted by autotrophs during times of high PP Why Does CO2 Increases with Depth? • Less photosynthesis ○ Based on total CO2 and water, more photosynthesis in Hawaii b/c lower concentration of CO2 at that latitude • The colder water is, the greater the solubility of gases like CO2 • Respiration by animals • Lack of photosynthesis to remove it • Low temperature • High pressure • CO2 dissolved in water --> carbonic acid (acid, so lower pH)

Seawater Acidity (pH) • Influenced directly by dissolved CO2 • Distort the shape of enzymes (large protein molecules that speed up the rate of chemical reactions) • Recall the pH scale… Hydrostatic Pressure • Pressure of the weight of all the water above • Decreases linearly with depth • Increases by the equivalent of one atmosphere for every 10 m of depth

• Rarely a "limiting" factor in the ocean for most organisms • Not a problem for most organisms • Chemistry: gases more soluble, some enzymes inactivated, faster metabolism Osmosis • A form of passive diffusion Active Transport • Reverse diffusion **Law of the Sea - U.S. has never signed off on it. Good b/c not buying into agreement whereby you can give away mining rights in international water.** International Seabed Authority...