Pelagic Deep-SeaMARS 345024 September, 2013William Beebe and Otis Barton 1930Bathyscaphe Trieste,1960Jacques and Auguste PiccardPelagic Deep SeaDefinition: The marine environment that lies below the light level necessary for photosynthesis, exclusive of continental shelvesAphoticPhotic•Mesopelagic: upper aphotic;light still present; 200-1000 m•Bathypelagic: no light; 1000-4000 m•Abyssalpelagic: no light; 4000-6000 m•Hadalpelagic: no light; >6000 mBegins where light is nolonger sufficient for photosynthesisTrenchesSea Floor TopographyMid-ocean ridgeTransform FaultTrenchZones of the Ocean(Nybakken 2001)TrenchesAbyssal plainContinental SlopeContinental Shelf(Nybakken 2001)What’s it like in the Deep Sea?•Light•Pressure•Temperature•Oxygen•Food(Castro & Huber 2003)•PressurePressure (atm) = 1 + depth (m)/10Deep Ocean Trenches10,000 m = 1,000 + 1 atm!air pressure at water surfaceAir pressure in a car tire ~32 PSIWater pressure in a hose in Athens ~60 psiAir pressure in a scuba tank ~2,400 psi = 163 atm1 atm = 14.7 psi,therefore1,001 atm = 14,715 psiDeep-sea creatures mostly die when brought to the surfaceRapid decompressionPressure effects on biochemistryThermal shock•PressureThree deep sea shrimp captured at 1157 m (not really very deep)(Koyama et al. 2007)Pressure gradually decreased over 63 daysLarvae hatched; lived for 74 daysAdults moved tobottom of the tank(Castro & Huber 2003)•Temperature •OxygenMesopelagic: ~5oCDeeper: 1-3oCCold and constant1/30th of surface levelsGlobal Distribution of OMZ’s at ~500 m DepthLocation of OMZ’sUpwelling zones, high primary productionVampyroteuthis“vampire squid”Oxygen minimum specialistLowest mass-specific metabolic rateGills have large surface areaHigh content of hemacyanin (binds O2)•Food…What’s to eat?1) Small POC: particulate organic carbon sinks from above2) Large POC: dead organisms sink from above3) Vertical migrators: prey captured in the photic zone, predators return to the deep4) Life-stage migrators: early life stage feed in the photic zone, adults return to the deepNo light, no photosynthesis, no food!Food must come from aboveMammal carcassesFish carcassesSome animals specializeMarine snowFecal pelletsExoskeletons (chitin)Baited line studies (Fig. 4.11)Don’t wait for food to come to youmesopelagic•FoodLife-stage MigratorsSmall POCLarge POCSinking Stuff(Pinet 1992)100 mg C/m2/d x 365 d/y = 36.5 g C/m2/yr1 m20%How much food gets to the deep sea?1%•Food5) Terrestrial InputsFood is scarce and unpredictableThe deep sea is sparsely populatedCharacteristics of Deep Sea Animals•SmallReflects the absence of foodFish only 10-20 cm in lengthInvertebrates also small, but occasionally deep sea “gigantism”•Body colorUpper mesopelagic: transparentLower mesopelagic and deeper: silvery, black, red, purple•MigrationMove into epipelagic at night, return at dawnZooplankton, nektonOnly from mesopelagic – not deep-seaCan’t be seen in blue lightMigration: Deep Scattering LayersSonar scattering caused by swim bladdersLanternfishJellyfishSquidShrimpzooplankton•BioluminescenceEmission of visible light by living organismsReaches pinnacle in marine environmentSpecialized organs: photophoresCharacteristics, continuedLight produced by animalsLight produced by symbiotic bacteriaBacteriaProtistsInvertsPoriferaCnidariaCtenophoraMolluscaArthropodaEchinodermataFishwww.newscientist.comwww.toptenzpictures.com(Castro & Huber 2003)•BioluminescenceWhy be bioluminescent?Characteristics, continued1) Findingmates2) Counter-illuminationunderwater viewMesopelagic•“Seeing but not being seen”•Tubular eyes•PhotophoresBioluminescent ShrimpEvidence that bioluminescentanimals match downwelling light•BioluminescenceWhy be bioluminescent?Characteristics, continued3) Startle predators with flash of light or with bioluminescent cloud4) “burglar alarm” illuminate predators and make vulnerable to their own predators5) Use as lures to attract prey to the mouth regionspewers•AnatomyStreamlining: absent in non-migrating mesopelagic fishpresent in migratingEyes:Larger in mesopelagic fish (maximum light capture)Tubular eyes: very sensitive, good lateral visionBathypelagic and deeper: eyes absent or reducedCharacteristics, continuedMay have two retinas•AnatomyMouth: Large; extreme size in deeper watersTeeth point inwardHinged jawSwim Bladder:Present in migrating mesopelagic fishAbsent in non-migrating mesopelagic fish anddeeper (watery body, weak bones, muscles)Energy intensive to maintainCharacteristics, continuedVampire Squid: ammonium replaces heavier ionsBlobfish – gelatinous mass replaces swim bladderEpipelagicMesopelagicBathypelagicAbyssalpelagicDeep seaBathypelagic, Abyssalpelagic•Large mouth, large teeth•Any size meal will