Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Environmental Characteristics• of the Epipelagic Zone Three dimensiorality-no cues for orientation No solid substrate-no shelter and no support Characteristic Features of Nektonic Species Great speed Great sensory abilities especially where navigation is concerned Counter-shading camouflage Buoyancy adaptations-swim bladders, accessory air sacs, reduced bone content, high lipid content Characteristics Features of Nektonic Species (2) Both r-selected (tunas, marlins, ocean sunfish, which produces millions of eggs, and grow extremely rapidly), and K-selected forms (sharks, which may produce only a few to tens of embryos and grow and mature quite slowly) Epipelagic Nekton Holoepipelagic forms (spend their entire life in the upper water column of the open ocean): flying fishes, tunas, marlins, swordfish Meroepipelagic forms (spend a part of their life in the upper part of the water column in the open ocean): herrings, salmon, halfbeaks, mammals, turtles, penguins Growth Growth rates are usually very high in epipelagic forms. However, longevity is usually not great (Example: r-selected large tunas live for only 510 years, while K-selected sharks may live for 20-30 years, and mammals may live for even longer periods). •• Migration Many pelagic organisms migrate very long distances. Why should they do this? Possible explanations include:(1) Exploit different food supplies in areas where food is abundant; (2) spawn young in warm waters where growth rates will be high; and (3) spawn where predators are less abundant. How to hide in the sea ) • • • • Transparency Mirroring Cryptic coloration Counter-illumination Transparency (jellies, etc.) Light passing through is about the same as the downwelling ambient Reflection and refraction from animal exceeds upwelling light Cryptic coloration and mirrored surfaces mirrored fish •White ventral surface is best under all situations •Dorsal surface never perfectly cryptic Diagram showing how a keel on the ventral surface of an animal eliminates he dark shadow normally cast downward by an unkeeled animal. The presence of the shadow means that an animal living deeper and looking upward would see the unkeeled nektonic animal due to the shadow, but would not see the keeled animal, which would blend into the lighted background. (Modified from Y. G. Aleyev, Nekton, Dr. W. Junk BV., 1977. Reproduced by permission of Kluwer Academic Publishers.) Fast swimming fishes with warm bodies have streamlined bodies and heavily muscled tails with crescent shaped caudal fins. The ones illustrated here are three tunas: the bluefin (a), the skipjack (b), and the wahoo (c), and a mackerel shark, the mako (d). Typical adaptations of epipelagic fishes. Three views of a tuna showing the adaptations necessary for fast movement. (A) Front view. (B) Side view. (C) Top view. Life in the mesopelagic and deep sea is linked to plankton and light intensity in the water. Animal Adaptations in the Mesopelagic Mid-water Realm Vertical Migrations of Animals Diel (daily) vertical migrations: cycle is coupled to downwelling light (the ‘Zeitgeber’ or ‘time-giver’) Three kinds of migrations... 10 New moon Z (m) Full moon 200 DAY NIGHT DAY Nocturnal migrations Three kinds of migrations... 10 Z (m) 200 DAY NIGHT DAY Twilight migrations Three kinds of migrations... 10 Z (m) 200 DAY NIGHT DAY Reverse migrations Why vertically migrate? Reduce light-dependent mortality Metabolic advantage • Light damage avoidance • Minimize horizontal advection (use deep counter-currents) • Prevent over-grazing • Maximize genetic exchange • Minimize competition Adaptations of Vertical migrators like the Lanternfish on left and non-migrators like dragonfish on right. 1. Well developed muscles and bones 2. Swim bladder of air or fat 3. Withstand extreme temperature changes O2 Minimum Layer Torres et al. Reduced with depth Tuna Vent fish Measured at 10 C Fish activity decreases with depth Theusen and Childress Only visual predators show this decrease in activity Oxygen binding capacity of OMZ animals Summary of Low oxygen adaptations Reduced oxygen consumption with depth Results in reduced athleticism Oxygen binding high Mesopelagic Crustaceans Photophores Specialized light structures that make “living light” or bioluminescence. Typical Mesopelagic Fish Rectangular midwater trawls used to collect mesopelagic organisms. Net has remote control to open only at certain depths. As more shallow fish are over fished other deeper fish like this black scabbord fish are being caught. This is one way that we have learned more about fish from deeper depths. Viperfish Large hinged jaw that can accommodate large prey Viperfish Chauliodus macouni (depth 80-1600m) 33 Many non-migrators like this Rattrap Fish eat the more muscular migrators because they have more protein! Tubular eyes like this midwater bristlemouth fish, with acute (great) upward vision. Coloration and Body Shape •Midwater predators rely on sight. •Midwater prey cannot afford energy cost of swimming fast, spines, or scales so they… •Camouflage with countershading (dark on top, light bottom or sides) •Transparency = see through them (in upper mesopelagic – jellies, shrimp, etc) •Reduce the silhouette (bioluminescence on bottom) With blue-green light they control! Value of Photophores Photophores on lower or ventral surface makes the silhouettes hard to see when they are viewed through water. Bioluminescence Living light is used for… 1) Counterillumination to mask silhouette 2) Escape from Predators with confusing light 3) Attract or see prey 4) Communication and Courtship Summary Typical Characteristics of deep-sea pelagic fish Tremendous pressure of 1,000 atmospheres or 14,700 psi 1. Tough to visit and bring fish back alive 2. Metabolism affected by pressure 3. Molecular adaptations to allow enzymes to work under extreme pressures. Sex in the Deep Sea Finding mates is a problem in the dark So animals use… 1. Bioluminescence 2. Chemical signals 3. Hermaphroditism 4. Male Parasitism Benthic Fish Nature of Life in the Deep Sea Benthos Reduced eyes or are completely blind (Live in complete darkness) Huge mouths to eat prey larger than themselves (Scarce food -less than 5% from higher waters) No vertical migrations to richer surface waters (small to reduce metabolic demands; flabby muscles, weak skeletons, no scales, and poorly developed respiratory, circulatory, and nervous systems) Nature of Life in the Deep Sea Benthos Slow Pace (Save Energy) Low Temp and High Pressure (slow pace) Live Long and Large (up to 100 years) Produce fewer larger eggs (a lot of food for larva) Dominated by Deposit Feeders (eat marine snow) Marine Snow Particles Marine Snow Particles Discarded feeding houses Marine Snow Particles ‘Comets’ Aggregates Contribution of Marine Snow to Vertical Flux Narrow window of particle sizes which are large enough to sink but numerous enough to be widely distributed. Cells Snow Bodies 2 200 20,000 (um) cell chain plankton feces aggregates Willie X 1-10 m 50 m Available to water column processes 100 m 2000 m Reduction in Vertical Flux over Depth 1 The Martin Curve 50% losses by 300 m 75% losses by 500 m 90% losses by 1500 m Martin and Knauer 1981 2 3 Explanations for the Shape of the Martin Curve • Bacterial decomposition = remineralization of Carbon • Cryptic swimmer distribution • Smaller, slower sinking particles at depth Composition of Marine Snow Once living material (detrital) that is large enough to be seen by the unaided eye. Described first by Suzuki and Kato (1955) High C:N makes for poor food quality. • Senescent phytoplankton • Feeding webs (e.g., pteropods, larvaceans) • Fecal pellets • Zooplankton molts Formation of Marine Snow Type A: Mucous feeding webs are discarded individually. Type B: Smaller particles aggregate into larger, faster sinking particles. Aggregates Extreme Deposition: Food Falls • Rare events (not recorded in traps) • Deposit large amounts of high quality organic materials to sea floor (low C:N) • Rapid sinking, reach 1000s of meters in few days • Large bodies that remain intact (whales, fish, macroalgae, etc) Amount of nutrients at different depths is controlled by photosynthesis, respiration, and the sinking of organic particles. Nutrients are recycled but sink! Deep water originates at the cold surface at the poles. Cold water sinks and spreads out along the bottom. Sound Scatterers Who are they? Fishes (e.g., myctophids or lanternfish) Crustaceans (copepods, krill) Jellies (siphonophores, medusae) 63 Animal Adaptations in the Mesopelagic Food • Oxygen • Light 64 Mesopelagic 65 Animal Adaptations in the Mesopelagic Mid-water Realm Bioluminescence Production of light by organisms through chemical reaction (kind of chemiluminescence). ALL PHYLA of animals have luminescent members (Know the difference between bioluminescence and fluorescence and phosphorescence) 66 Adaptations for Bioluminescence Decoys: Long duration, broad wavelength, intense False sense of size: Peripherally located, broad wavelength Blind/confuse predator: Bright flash, broad wavelength Blink and Run: Bright flash or luminescent cloud Lure Prey: located near or in mouth Burglar alarm: bright, long duration How does duration, intensity and wavelength serve an adaptation? 67 Barreleye Macropinna microstoma (Depth 100-900m) 68 Headlightfish Diaphus theta (depth 0-800m) Northern Pearleye Benthalbella dentata (depth 500-1000m) 69 Robust Blacksmelt Bathylagus milleri (depth 60-1000m) 70 71 Animal Adaptations in the Bathypelagic Mid-water Realm Conservation of Energy •Loss of muscularity and skeletal mass •Low protein content in muscle •Reduced eyesight Blob sculpin(b) Psychrolutes phrictus 72 Eelpout 73 Giant grenadier Albatrossia pectoralis Gigantism 74