PAR. Correlated with Healthy Reef Coral Growth. Environmental Factors. Environmental Factors Affecting Corals and Coral Reefs

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1 Environmental Factors Affecting Corals and Coral Reefs Environmental Factors Correlated with Healthy Reef Coral Growth The Electromagnetic Radiation Spectrum PAR Photosynthetically Active Radiation Light Absorption in the Ocean Light Intensity decreases with depth 100 meter = depth limit of hermatypic corals primarily a result of the overall reduction in light many studies have focused upon how changing light intensities with depth affect the photosynthesis of zooxanthellae of corals Light Absorption in the Ocean Spectral Characteristics red wavelengths absorbed more readily by water than blue wavelenths blue light penetrates deepest in the oceans the change in the spectral characteristics of light with depth likely to influence plant photosynthesis less work has been done to understand the influence of the spectral distribution of light on zooxanthellae photosynthesis in corals 1

2 Light Penetration in the Ocean Primary Productivity The rate of production of organic matter by autotrophs Photosynthesis 6CO 2 + 6H 2 O Æ C 6 H 12 O 6 + 6O 2 Measuring Primary Productivity in the Ocean Standing Crop Estimates weigh out total plant material measure concentration of chlorophyll in the water use satellite imagery Measure Actual Rates of Primary Productivity measure oxygen production and consumption by plants (e.g., light-dark bottle technique) Photosynthesis 6CO 2 + 6H 2 O Æ C 6 H 12 O 6 + 6O 2 Aerobic Respiration C 6 H 12 O 6 + 6O 2 Æ 6CO 2 + 6H 2 O 2

3 Light-Dark Bottle Technique Light Dark Using the Oxygen Light-Dark Bottle Technique to Measuring Primary Productivity O 2start = Starting Oxygen Concentration O 2end = Ending Oxygen Concentration O 2end - O 2start = O 2 O 2 Produced O 2 Consumed Relationships Between Gross Production, Respiration, and Net Production Gross Production (GP) The total amount of oxygen (or organic matter) produced due to photosynthesis Respiration (R) The total amount of oxygen (or organic matter) consumed due to aerobic respiration Net Production (NP) The net amount of oxygen (or organic matter) produced (or consumed) due to the combined effects of respiration and photosynthesis Symbols Used O 2 due to RESPIRATION = O 2R O 2 due to GROSS PRODUCTION = O 2GP O 2 due to NET PRODUCTION = O 2NP Calculating GP from NP and R Photosynthesis as a Function of Light Intensity O 2GP = O 2NP - O 2R productivity rate DO 2 time GP R region of light saturation assumption: respiration continues at a constant rate regardless of whether the light is on or off 0 NP light intensity 3

4 Colony Morphology Responses to Irradiance Photoadaptation in Corals Hemispherical Branching Colonies Plate-Forming Colonies Changes in pigment concentrations and algal densities in response to light intensity Hoover, J.P., 1998) Visable Light Cosmic Rays X Rays UltraRadio Waves Gamma Rays Violet Infrared Absorption of Ultraviolet Radiation by the Earth s Atmsophere X Rays Types of UV and Human Sunburn Responses 400 Visable Light Vacuum UV UVB UVC UVA M idd le- & L on gw a v e U V ( UV B & UV A) Sho r tw a v e U V V is ib l e L ig h t & I n f r a r e d ( UV C ) A bs orbed b y ozone in E arth ' s a t m os p he r e Effects of UV on Living Things damage to DNA resulting in mutations damage to other biological molecules proteins: enzyme inactivation lipids: disruption of cell membranes and membrane transport systems Corals and UV Radiation decreased growth and increased reproductive output decreased rates of calcification transplantion experiments (deep corals brought to the surface) demonstrate corals may be UV-sensitive (exhibit bleaching and increased mortality) coral sperm appears to be UV-sensitive (note spawning normally takes place at night) 4

5 Ultraviolet Absorbing Compounds in Corals mycosporine-like amino acids (MAA s) MAA s apparently produced by zooxanthellae but stored in the animal tissues concentrations greater in shallow water corals than in deeper ones transplation experiments demonstrate adaptional changes in pigment concentrations positively buoyant eggs exhibit higher concentrations of pigments than do negatively buoyant eggs EFFECTS OF UV ON THE CORAL - ALGAL SYMBIOSIS L i g ht E n e r gy PA R + UV Light is necessary for photosynthesis to occur; but certain wavelengths of light can be harmful. Effects of UV on the Coral-Zooxanthellae Symbiosis Some corals have pigments which absorb UV light, exciting certain Coral pigment molecules, which granule in turn emit lower frequency light. Such PAR flourescence can be used for photosynthesis Harmful UV light can be filtered by coral pigments or special UV absorbing chemicals (S-320 compounds) PAR P HO TOSYNT HESIS Zooxanthellae Coral Polyp Ozone in the Atmosphere Temperature Lethal Limits Maintaining Ozone Levels in the Atmosphere Global Distribution of Coral Reefs 5-36 oc physiological effects = bleaching (expulsion of zooxanthellae from coral tissues) Ecological Limits 18-29oC (low limit correlates with 20o N & S latitude limit of reef corals) some exceptions exist reasons for differences between lethal and actual limits secondary effects of temperature on feeding or on reproduction synergistic effects of other environmental factors (e.g., UV irradiance) 5

6 Bleaching Global Climate Change Other Factors Sediments Salinity Sedimentation Aerial Exposure at Low Tide Water Motion Inorganic Nutrients Currents Nutrients and Algae Growth 6