Lecture8Temperature, Nutrients, Transport

Lecture8Temperature, Nutrients, Transport - Physical and...

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Unformatted text preview: Physical and Biological Factors and Processes That Affect Life in the Ocean Ocean 1. 2. 3. 4. 5. 6. 7. 8. Light Temperature Dissolved Nutrients Diffusion, Osmosis, Passive & Active Transport Salinity pH Dissolved Gases Hydrostatic Pressure 2. Temperature 2. Ocean temperature varies with depth and Ocean latitude (why?) latitude Warmest water in the illuminated surface layer; Warmest coldest in deep ocean coldest Temperature impacts metabolic rate (rate at Temperature which energy-releasing reactions proceed); other physiological functions (e.g. photosynthesis) photosynthesis) Q10 is a factor that describes how rates change with a 10°C rise or fall in temperature (for with rise example, if Q10 = 2, then rates would double with example, a 10°C rise in temperature) 10 Scientists use the metric scale; SI approved unit Most marine organisms are ectothermic “cold blooded” meaning they match their internal temperatures to their surroundings Mammals, marine birds are endothermic (stable, high internal temps) Adaptations allow endotherms to tolerate a wide range of temperatures (fur, lipid stores, shunting of blood from extremities) 3. Dissolved Nutrients 3. Nutrient = compound required for the production of Nutrient organic matter or structural parts (cell walls) organic Organisms are composed of many elements, but mostly C, O, H, N, P Nitrate, Ammonium, Phosphate, Silicate, Bicarbonate, Trace Metals (Fe) Compare to fertilizer composition C:N:P 106:16:1 (Redfield Ratio) Phytoplankton are most productive where nutrients are most abundant…regions include: •Coastal areas (runoff, rivers) •Upwelling regions •(Deep oceans are also nutrient rich due to decomposition of organic matter; recycling) Photosynthesis provides the “carbon skeleton”; nutrient uptake provides other components necessary for the construction of lipids, proteins, etc. “Growth” = result of photosynthesis and nutrient uptake processes Chlorophyll a from SeaWiFS satellite 1997-98 “Limiting” Nutrients Most elements are present in abundances sufficient for growth The one that is most limiting determines the rate of growth Is not necessarily the element in lowest concentration, but the one that is supplied at the lowest rate relative to the need In most ocean regions, nitrogen is the limiting nutrient In some regions (the Southern Ocean), iron is the limiting nutrient (receives little atmospheric dust) Surface Area to Volume Ratio Surface Assuming they are the same shape, the smaller the cell the higher the SA to Volume ratio. Higher SA to Vol means that material can be transported more efficiently across the cell membrane. (e.g. more SA to permit gas exchange, more transporters per unit volume than a large cell) Biomass and Surface Area Biomass Biomass may be small, but small cells have a proportionally larger surface area What are the implications for materials exchange? SA:vol =? How materials (including nutrients) cross membranes … cross Diffusion - the movement of “particles” from a region of higher concentration to a region of lower concentration Osmosis - the movement of water across a selectivelypermeable membrane from a region of higher concentration to a region of lower concentration Passive Transport – diffusion of water soluble substances through a protein channel (down concentration gradient) Active Transport – Dissolved substances (ions, small molecules) are transported against concentration gradients; requires energy (ATP) Selective Permeability oxygen, carbon dioxide, and other small, nonpolar molecules glucose and other large, polar, water-soluble molecules; ions (e.g., H+, Na+, K+, Ca++, CI–) [Interactive exercise on CD – Ch 5 Page 2] Diffusion – a physical process, dye distributes evenly; energy comes from heat (random vibration of molecules) Occurs faster at warmer temperatures Oxygen, CO2, water may enter or leave cells through diffusion across cell membrane Osmosis Osmosis • Osmosis is important to all aquatic organisms, fresh or saltwater • The skin and cell membranes act as a semi-permeable membrane • For most marine organisms, their body fluids have the same salinity as seawater (isotonic) • If body fluids are less salty than seawater, then they are hypotonic • If body fluids are more salty than seawater, then they are hypertonic Marine fish (not sharks) – body fluids are less salty (hypotonic) as compared to the surrounding water 1. Tend to lose water by osmosis but the kidneys are modified in such a way that very little water is extracted from the blood, produces concentrated urine. 2. Water is still being lost by the gills and this cannot be stopped, to replace the water as quickly as it is lost marine fish drink water 3. However, drinking water cannot solve the problem because they are drinking salt water and therefore, Na + and Cl- ions will accumulate; special cells in the gills called chloride cells move these ions out of the body Some membrane crossing mechanisms Concentration gradient high ATP low Diffusion of lipid-soluble substances Passive transport of water-soluble substances, e.g glucose Active transport through ATPase, e.g. Ca++ From the photosynthesis lecture… sunlight THYLAKOID COMPARTMENT H2O photolysis second electron transfer chain e– e– STROMA PHOTOSYSTEM II first electron transfer chain NADP+ PHOTOSYSTEM I ATP SYNTHASE NADPH ADP + Pi ATP WHY DO WE NEED TO KNOW ALL THIS STUFF ??? Active Transport Systems maintain concentration and electric gradients concentration across membranes; vital to cell activities and physiological processes and For our purposes: Nutrient uptake, gas For exchange – critical for life in the ocean exchange 5. Salinity 5. Water on Earth contains minerals, creates Water “saltiness” “saltiness” Salinity varies due to rainfall, evaporation, runoff Salinity from land from Generally, salinity increases with depth Organisms need to adjust osmotically to Organisms variations in salinity in the environment or risk changes in protein structure, cell membrane damage damage Euryhaline vs. stenohaline 6. Acid-Base Balance (pH) 6. pH describes the acidity or alkalinity of a pH solution solution 8.1 Seawater pH ~ = ? Enzymes have pH optima, or can become Enzymes denatured denatured CO2 in seawater forms carbonic acid then rapidly dissociates to bicarbonate or carbonate depending on pH carbonate The oceans absorb “excess” CO2 The -ours! -ours! There is no doubt that atm CO2 no concentrations are increasing. concentrations What we don’t know is the impact this What has on the ocean (or terrestrial) ecosystems. ecosystems. Atmospheric CO2 at Mauna Loa Observatory, Hawaii Annual fluctuations = seasonal cycle of photosynthesis; reflects asymmetry of land mass area between northern and southern hemispheres Long term trend = Our contribution! Air bubbles in ice cores give us a longer term perspective Air Atm CO2 increase is coincident with industrial revolution in late 1800’s late Burning of fossil fuels is largely to blame The climatic consequences of increasing atm CO2 are well known increasing CO2 is a “greenhouse gas” Excess CO2 in the atmosphere IS CAUSING IS (sometimes unpredictable) shifts in global climate (sometimes Sometimes called “global warming” Not today’s topic What is less often discussed is the What fact that the ocean absorbs ~30-50% absorbs of anthropogenic CO2 emissions of Projections over the next millennium say the ocean Projections over the next millennium say the ocean will absorb ~90% of anthropogenic CO2 emissions (Archer et al. 1998). In other words, the chemistry of the oceans is being altered; oceans are becoming increasingly acidified. becoming From Doney et al. 2006 Normal sea water pH ~8.0 – 8.3 From: Millero text, thanks to Ben Twining Absorption of CO2 has already caused a pH decrease of ~ 0.1 Absorption of CO pH units (Feely et al. 2004); at current fossil fuel use, pH will decline by an additional 0.3 units by 2100. Note that no current predictions have the ocean becoming “acidic”…only less basic Does this pH shift matter? Does pH shifts will greatly affect marine organisms that build pH their shells out of calcium carbonate (the calcifiers) their Includes…coccolithophores, foraminifera, pteropods, Includes…coccolithophores, pteropods hermatypic corals, coralline algae; organisms that use the corals coralline organisms mineral forms of calcium carbonate (calcite, aragonite, Mg aragonite calcite) for their shells calcite Cliona limacina http://www.sfos.uaf.edu/research/arcdiv/waterc olumn/pteropod/cliona_limacina.htm Coccolithophore (E. huxleyi) bloom in the Bering Sea Pteropods are important players in Arctic and Antarctic food webs…serve as food for fish. Chilly! Global Distribution of Coral Reefs Solubility of CaCO3 depends on CO3­2 (pH), temperature and depth. Calcification rates decline and dissolution rates increase (shells dissolve) as saturation horizon for calcite and aragonite shallows Shallow water is warm, low pressure, and “supersaturated” in calcite and aragonite 50­200m Since 1800’s (Feely et al. 2004) Deep, cold waters are acidic and “undersaturated”; will dissolve CaCO3 shells Predictions for Pteropods (Seibel and Fabry, 2003) “Aragonite­secreting polar pteropods may disappear by the end of this century or they may migrate to lower latitudes” [Calcite­based organisms (calcareous phytoplankton and zooplankton) declines are expected to come decades later… calcite is a less­soluble form of calcium carbonate.] Major Benthic Calcifiers Coralline algae Reef­building coral Halimeda Benthic forams deep­water coral Bryozoan Outlook for corals Outlook • As carbonate ion concentration decreases, production of coral skeletons slows, “reef building” vs “reef erosion” balance shifts negative (Kleypas et al. 2001). Average response of corals to a doubling in pCO2 is a 30% decline in calcification (3-60% all benthos) 30% Coral reef problems are compounded by climate change, overfishing, habitat destruction stressors “The potential impacts of increased CO2 on planktonic and benthic ecosystem structure and function are unknown” and (Organism interactions, food web responses, (Organism survival, carbon and nitrogen cycling, carbon export, adaptations (?)) export, Topic of a recent workshop Topic Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L. Sabine and L.L. Robbins. 2006. “Impacts of ocean acidification on coral reefs and other marine calcifiers: A guide for future research”, report of a workshop held 18-20 April 2005, St. Petersburg, FL, sponsored by NSF, NOAA, and the US Geological Survey, 88 pp. US Biological reactions may alter pH slightly 7. Dissolved Gases 7. Plants and Animals require CO2 & O2 CO2 is soluble in ocean, not so for O2 is Ocean is a “sink” for CO2 = holds more than atmosphere (60 x more); marine plants usually don’t run out usually Deep water holds more CO2 than surface water due to cold temps, solubility water CO2 concentrations are highest in cold water; cold CO waters are dense, sink at poles, pull CO2 to deep waters ocean (high pressure keeps it in solution) ocean Thermohaline Conveyor Belt Respiration by animals in deep water further increases CO2 content as does organic matter decomposition CO O2 does not dissolve easily in sea water Is more O2 in atmosphere than in ocean Is Concentrations of O2 are highest at the surface Concentrations (increased by photosynthesis), decrease with depth (due to respiration) respiration) May have hypoxic (< 2 mg/l O2) or anoxic (no O2) zones May or 10. Hydrostatic Pressure 10. Water is heavy; organisms that live deeper in the ocean are Water subjected to pressure from the constant weight on water subjected Marine organisms are adapted to deal with this just as we are Marine adapted to atm pressure (1 kg per cm2, or 14.7 psi at sea adapted or level) level) Organisms equalize their pressure (in/out) “Deep Ocean”: gas solubility increases, enzymes may deactivate, metabolic enzymes rates are slightly elevated (but organisms adapt); problematic when collecting deep-sea specimens ...
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