Deep Sea Fauna Zonation and Biogeography SIO 277 L Levin Who Lives in the Deep Sea Bacteria Archaea Protozoa Meiofauna 42 500 m Macrofauna 300 m Megafauna visible 1 cm Giants BACTERIA AND ARCHAEA in sediment in guts on detritus on carcasses as symbionts on hard surfaces Bacteria aerobic anaerobic heterotrophic autotrophic sulfate reducer sulfide oxidizer methane oxidizer Fe Mn oxidizers Protozoa Xenophyophores Foraminifera Komokiacea superfamily Metazoan Meiofauna Nematodes Ostracods Gnathostomulida Harpacticoid copepods Kinorhynchs Oligochaetes Loricifera Macrofauna Peracarid crustaceans Brachiopoda Mollusca Amphipods isopods tanaids cumaceans Annelida polychaetes Bryozoa Priapulida Megafauna Echinoderms Crinoids Holothurians Ophiuroids Echinoids Asteroids Sponges Megafauna Mollusca Cnidarians Crustaceans Annelida Echiura Hagfish Enteropneust Humongofauna Giants pycnogonids giant squid Munopsis Colossendeis bryozoan Eurythenes Kinetoskias ascidians Culeolus Polychaetes often comprise half or more of the macrofauna Site Depth m Substrate N Carolina Margin I 850 NC II NC III Horizon Guyot 1840 Santa Catalina Basin 1130 Central Pacific Seamounts 1480 3150 San Diego Trough 1230 Rockall Trough 2200 HEBBLE 4820 Porcupine Abyssal Plain 4500 Central North Pacific 5500 Aleutian Trench 7298 Polychaetes 34 sand 20 sand 31 sand Foram Sand Mud Calcareous muds Mud 90 mud Red Clay 43 74 66 47 77 66 67 76 59 67 35 55 49 Dominant Scalibregma Chrysopetalid Dorvilleid Paraonid Paraonid Cirratulid Ampharetid Spionidae Key Zoogeographic Features Original view 1 province cosmopolitan species no geographic boundaries Ekman 1953 4 zoogeographic zones Atlantic Indo Pacific Arctic Antarctic Vinogradova 1959 62 79 Species have limited distributions Only 15 of species occur in 1 ocean Only 4 of species occur in all ocean Genetic methods reveal cryptic species cosmopolitanism rare France Kocher 1996 Eurythenes gryllus is many species But there is great similarity among oceans at the generic level Genera are cosmopolitan Of 143 isopod genera in the Pacific 134 are present in the Atlantic Desmosomatidae Isopods North vs South Atlantic same 12 genera North Pacific vs Atlantic Pacific is missing 2 genera and 77 similarity has one not in the Atlantic Asellote isopods Poore et al 94 67 of 98 genera on the SE Australian slope are in the Atlantic Ophiomusium brittle star worldwide at mid slope depths Vinogradova 1979 Zoogeographic divisions of the abyssal and hadal zones of the world Distinct hadal fauna Belyaev 1959 1989 more amphipods polychaetes bivalves echiurids holothurians Origins of Deep Sea Fauna Antarctic or shallow water origins then submergence Deep origins and Antarctic emergence Ilyarachnid isopods in taxa with diversity centers in the deep sea Isolated basins have endemics only at species level suggesting invasion from shelves and recent evolution Red Sea and Sea of Japan have eurybathic species from Indian Pacific oceans A C C High lat Equator Mid lat What is Zonation Pattern of uniform change in species Step like boundaries between regions of homogeneous composition Current usage Non repeating sequential pattern of species replacement measurable as changes in the overall rate of change in faunal composition Why should we care about zonation Resource exploitation is increasing fisheries petroleum Sound management demands understanding of distributions Key to interpreting diversity patternsns Zonation Terminology meters 200 Shelf 500 Epipelagic euphotic Mesopelagic disphotic Upper Slope Bathyal Bathypelagic aphotic 1000 Lower Slope 3000 Continental Rise 4000 6000 Benthopelagic Abysssal Hadal Zonation in the Past Since Challenger Expedition Scientists have recognized that species change much more rapidly with depth down the continental margin than horizontally Depth related changes in the ocean are considered one of the greatest environmental gradients on this planet Gage and Tyler What can generate zonation in the Ocean Challenger Sars expeditions Murray and Hjort 1912 3 ZONES Shelf to 200 300 m Archibenthic transition 600 800 2000 3000 bathyal based on megafauna topography temperature Abyss upper boundary set at 4oC isotherm Bruun 1957 lower boundary at 6000 m topography shelf transition There is little area between 1000 2500 m Yet this is the zone of highest diversity And Most rapid change in composition abyss What can generate zonation in the Ocean Hydrographic Features Light Pressure Temperature Organic Flux Oxygen Salinity Controlling Gradients Light Light present to 1000 m Childress 1995 the use of vision by fishes crustaceans squid above 1000 m elevates metabolic rate and affects forms present Crustaceans Cephalopods Fishes Controlling Gradients Hydrostatic pressure only variable directly related to depth 10 m 1 atm pressure accelerates reactions in which the molar volume of the products are less than the molar volumes of the reactants Pressure retards reactions in which there is a volume expansion Le Chatelier effect Effects of pressure in the deep sea Increased dissolution of calcium carbonate Increasing metabolic cost associated with maintaining carbonate structures at depth molluscs foraminiferans echinoderms show effects Influence on chemosynthesis based on H2S Stability of gas hydrates 450 m Protein structure membrane fluidity lipid content Different properties of gellatinous membranous megafauna A piezo barrier to downward colonization 500 1000 m 2000 3000m Sets recoverability Controlling Gradients Temperature 55oN to 55oS Warm low density upper layer Thermocline may form a barrier Much of the deep sea is 2 4oC Increasing temperature increases chemical reaction rates 2 to 3 x rate increase with 10o C temperature increase Adaptations to cold increasing concentrations of enzymes adopting enzymes effective at low temperatures incorporating modulator compounds that help maintain enzyme reactions over a range of temperatures Are water mass effects the result of temperature Controlling Gradients Organic Flux Since Forbes 1859 importance of food recognized Decreasing food input with depth less than 1 reaches abyss Different rates of mixing within sediment with depth Food effects on zonation may be modified by competitors Effects of OM flux include changes in sediment geochemistry High flux depletes oxygen TROX model foraminifera distributions based on oxygen and food TROX model applied to foraminifera Controlling Gradients Oxygen Oxygen minima at 100 1000 m 0 5 ml l 22 M Sharp faunal changes