Life in the Deep Sea. The Deep Sea Environment. 80% of ocean floor =2X total land area above sea level m depth Largest environment on earth

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1 Life in the Deep Sea Angler fish photo The Deep Sea Environment m depth Largest environment on earth 80% of ocean floor =2X total land area above sea level Extremely poorly known even today S 1S 1 S 2S 2 Environmental Zones Of The Deep Sea The Bathyal Zone ( m) Continental Slope Benthic Environments The Abyssal Zone ( m) Continental Rise, Abyssal Plains, Abyssal Hills and Mid Ocean Ridge Benthic Environments The Hadal Zone (>6000m) Benthic Exploration Early explorers noted less O2 with depth, therefore thought deep seas likely to be anoxic/devoid of life. Turned out to be wrongtrend reverses below ~1000m and deepest waters are generally oxygenated Trenches S 3 S 4 The Deep Sea Pelagic Zone S 3 S 1

2 Difficulty of exploration even today Remote sampling using grabs, dredges & nets Hard to know how representative your samples are Sampling and observation with ROVs and manned submersibles S 5 S 6 S 6 Environmental Limitations On Deep Sea Life Oxygen? Generally not limiting Kept high by combination. of Antarctic bottom currents and low oxygen consumption Light No sunlight below ~250m max Bioluminescence (minor) S 7S 7 S 8 S 8 2

3 Temperature/Salinity Very uniform ~-2 near poles to 7-8 C at 1000 m near equator Warmer in Mediterranean (12-13 C) Salinity also very uniform What about seasonal cycles? S 9 Currents & Pressure Currents to 1m/sec Filter feeders orient to currents Pressure 1 atm/10m depth 1000 atm in deep trenches! High hydrostatic pressure slows metabolic activity. Slow growth & long lives! S 10 Currents & Pressure Rate of bacterial decay is reduced under high hydrostatic pressure. Organic material that settles onto the sea floor remains for a long time before it decays. It is thus more likely to be consumed by large scavengers. S 11 Food In The Deep Sea - major challenge! What are the sources? from surface (photosynthesis based) Rains down as particles Transported in laterally in turbidity current from chemosynthesis Hydrothermal vents Cold-seep vents Predation Sediment/deposit feeders S 12 3

4 Food In The Deep Sea - major challenge! What are optimal strategies? Capture particles effectively Take advantage of currents Sticky nets, feeding structures Keep your mouth wide open and pointing upwards Vertical diurnal migration Specialized organs for detection or capture of prey, storage of food Dig in the sediment Be opportunistic (whalefall) Lure prey with light S 13 Avoid capture with optical, camouflage, other strategies Get energy from chemosynthesis (sulfides, methane) Food In The Deep Sea Coastal productivity Transported by turbidity currents Decreases away from coasts to very low levels S 14 Pelagic Rain Pelagic Rain Small particles settle 1-3m/day (i.e. takes 5-10 years to reach abyssal plain) Speed up if in aggregates ( marine( snow ) ) or fecal pellets ~90% is consumed in photic zone-little reaches bottom Food chain over most of ocean floor is based on deposit feeding Windfalls of whales S 15 S 15 S 16 S 16 4

5 Example: Wha New species of worm that feeds exclusively on whale carcasses How to get food? Roots that extend into bone How to find mates? Female incorporates dozens of males, larval/microscopic but making gametes Broadcast larvae widely, in hope that a few will find other whales m deep -Monterey Canyon -Worms and sea cucumbers S 17 Deep-sea coral communities Non-photosynthetic corals Incredible biodiversity of reefs More species of coral than in shallow water! 1100 invertebrates on one reef in N Atlantic Often species are endemic (especially on seamounts) Important role for fisheries Slow growth, reproduction = very old systems and individuals Challenging to study - early days! S 18 Deep-sea coral communities Deep-sea trawling and deep-sea reefs Drag net along bottom Incredibly destructive Nationally restricted; UN considering ban before after Cold water, Widely distributed m depth (or more?) S 19 S 20 5

6 Chemosynthesis on black smokers & other hydrothermal vents/seeps Normal photosynthesis (by photosynthesizing plants and bacteria) vs. chemosynthesis by sulphur bacteria, archaea and other microbes using chemical reducing agents for energy sources Leads to locally exceptionally high biomass and productivity compared to surrounding deep sea Types Of Organisms Encountered Bony & cartilaginous fish, cephalopods Benthic invertebrates mostly deposit or filter feeders, few predators Planktonic invertebrates-tendency towards large body size S 22 S 21 S 21 S 22 Giant squid Up to 60 (18m) long Eaten by sperm whales Can attack humans, but not common Very hard to track and study Adaptations Body features which maximize chances of finding a meal or mate Enormous mouths/ extrusible jaws Very sharp, grasping teeth in fish & body lures Expandable stomachs/body cavities S 23 S 24 S 24 6

7 Fish adaptations S 25 S 26 More Deep Sea Adaptations Ability to find food items at great distances for fish Parasitism in dwarfed males (angler fish) Body photophores for spacing, lures, camouflage Bioluminescence is less common than in photic zone Most deep sea animals are blind Delicate tissues Characteristics of deep ocean life Few in number Year-round reproduction Small broods, slow growth, long life Consistent with very low temperature Surprisingly high diversity Relate to consistent physical environment S 27 S 27 Interesting ecosystems where unusual species cluster: vents, seeps, deep-sea reefs, whalefalls S 28 7