life in the deep: the ocean depths (the mesopelagic, bathypelagic and abyssopelagic zones)

LIFE

IN

THE

DEEP:

THE

OCEAN

DEPTHS

(the mesopelagic, bathypelagic and

abyssopelagic zones)

Alvin

© Rod Catanach/MCT/Landov

Living Conditionson the Deep-Sea Floor

– Most of the seafloor is covered with thick accumulations of fine sediment particles:

– mineralized skeletal remains of planktonic organisms, known as oozes, that sink to the deep sea and accumulate very slowly (about 1 cm every 1000 years).

Living Conditions on the Deep-Sea Floor

• Two types of seafloor samplers: (a) bottom dredge, which skims the surface of the sediment, and (b) grab sampler, which removes a quantitative “bite” of sediment and its inhabitants.

Living Conditions on the Deep-Sea Floor

• Fine-grained bottom sediments off the Oregon coast disturbed by the impact of a current-direction indicator.

Living Conditions on the Deep-Sea Floor

• Manganese nodules scattered on the surface of the seafloor

in the Pacific Ocean.

© Woods Hole Oceanographic Institution

• Part 1 “reminder:”

WHERE ARE WE?

(1)Mesopelagic

(2)Bathypelagic

(3)Abyssopelagic

Marine zones

MESOPELAGIC:

1. Below the epipelagic zone

2. No primary photosynthesis, but there is still productivity (i.e. still in the photic zone but it is disphotic)

3. 200-1000 m depth

BATHYPELAGIC, ABYSSOPELAGIC

1. The “deep sea,” aphotic, twilight zone

2. After 1000 m in depth (to ocean floor)

• Part 2 “reminder:”

WHAT IS THE “WATER CHEMISTRY” IN THIS LAYER?

Living Conditions on the Deep-Sea Floor

Deep wateroriginates near

the surface

Deep water oxygen is circulated and replenished w/open ocean circulation from the surface

Wheredoesthe

oxygencomefrom?

Transfer of Oxygen and Energy to the Deep Sea

– The diffusion and sinking of cold, dense water masses are the chief mechanisms of O2 transport into the deep sea.

– Dissolved O2 is slowly diminished by animals and bacteria, leaving an O2 minimum zone at intermediate depths.

– Below this zone, dissolved O2 gradually increases to just above the sea bottom.

• Part 3 (new)

(a) WHO LIVES THERE?

(b) WHAT SPECIAL ADAPTATIONS DO THEY HAVE (and why)?

Living Conditions on the Deep-Sea Floor

Life on Abyssal Plains

• Comparison of deep-sea species diversity (for

polychaete annelids and bivalve mollusks) with three other marine environments.

Adapted from Sanders, H. L., Am Nat. 102 (1968): 243-282.

Living Conditions on the Deep-Sea Floor

• Gigantism is surprisingly common in the deep sea. The Greenland shark,

Somniosus, a dogfish that occurs down to at least 1200 meters, can

exceed 6 meters in length unlike its diminutive relatives.

© WaterFrame/Alamy Images

Mesopelagic (lantern vs. dragonfish)

Mesopelagic fish

• Mesopelagic, Bathypelagic and Abyssopelagic zone species have many unique characteristics to adapt to their “extreme environment.”

(1) Fish start to show different characteristics…

(a) Based on light availability:

--higher eyes; 2 fields of vision

--photophores; bioluminescence, countershading

(b) “other” adaptations:

-- musculature changes

-- jaw adaptations

Where are we? Light????

(mesopelagic) Bristlemouth w/ tubular eyes

w/o photophores

w/o photophores

• …DEEP SEA FISH…

• Everything has a BIG MOUTH

• Everything is LONG and “SKINNY”

• Everything is BIGGER

viperfish

Rattrap fish

Swallower eel

Stomias deep-sea bioluminescent fish.

Credit: © HBOI/Visuals Unlimited

Angler Fish (Melanocetus johnsonii) uses lights to attract prey, an example of bioluminescence.

Credit: © HBOI/Visuals Unlimited

The Fangtooth (Anoplogaster cornuta) is a bioluminescent fish found in the deep sea.

Credit: © HBOI/Visuals Unlimited

Some still live on the bottom…

A bait can quickly attracts mobile scavenging fishes

© Scripps Institution of Oceanography Archives, UCSD

• Not everything is a “fish,” but adaptations are still very similar!

Deep Sea Amphipod (1’!)

Mesopelagic shrimp

Mesopelagic squid

Vampyroteuthisinfernalis

BENTHOS TOO: Fine-grained bottom sediments disturbed by a current direction indicator

Life on Abyssal Plains

• A shift in dominant taxonomic groups occurs in deeper water

– echinoderms, polychaete worms, pycnogonids, and isopod and amphipod crustaceans become abundant

– mollusks and sea stars decline in number

Life on Abyssal Plains

– Most benthic animals in the deep sea are infaunal deposit feeders, extracting nourishment from the sediment in much the same manner as earthworms.

– Croppers have merged the roles of predator and deposit feeder by preying heavily on populations of smaller deposit feeders and bacteria.

Sea-floor images showing the deposition of phytodetritus (marine snow)

Deep-sea cucumber

© David Wrobel/Visuals Unlimited

Slower invertebrates at the bait can

© Scripps Institution of Oceanography Archives, UCSD

• The “Deep” even contains an entirely new (and very different) Marine Community –

Hydrothermal vents!

An artist's rendition of the research submersible Alvin exploring the deep-sea floor

© Phototake, Inc./Alamy Images

Vent and Seep Communities

–Deep-sea hot springs, recently discovered along the axes of ridge and rise systems, support unique communities of deep-sea animals and bacteria.

–Seep communities are more dispersed in areas where hydrocarbons, particularly methane or other natural gases, are percolating up through deep-sea sediments.

Vent and Seep Communities

• Hydrothermal Vent Communities

– Dissolved H2S emerging from seafloor cracks is used as an energy source by chemosynthetic bacteria

– These bacteria become the source of nutrition for dense populations of the unique animals clustered around these springs.

Importance of Vent Ecosystem Discovery

1. Life in extreme environments

2. Life independent of sun

Chemosynthesis = a type of primary production

Photosynthesis uses sunlight + carbon dioxide coverts to foodChemosynthesis uses sulfur + carbon dioxide converts to food

Photosynthesis reaction:CO2 + H2O + sunlight CH2O + O2

 Chemosynthesis reaction:

O2 + CO2 + H2O + H2S   CH2O + H2SO4

  where H2S is hydrogen sulfide, H2SO4 is sulfuric acid, and

CH2O is “food” or organic material

PHOTOSYNTHESIS

+

CO2 + H2O O2 + [CH2O]

CHEMOSYNTHESISCO2 + H2O + H2S + O2 [CH2O] + H2SO4 CO2 + H2O + H2S + O2 [CH2O] + H2SO4

Importance of Vent Bacteria

• Base of vent ecosystem -- chemosynthesis

• Possible origin of life on Earth

• Illustrate link between biology and habitat

Vent and Seep Communities

• Diversity of Vent Inhabitants

– Just as the geology of hydrothermal vents is dissimilar in the eastern Pacific versus the North Atlantic, so too is the assortment of organisms living around the vents in each ocean

– To date, six major seafloor provinces have been defined

Approximate locations of confirmed hydrothermal vents and cold seeps

Cross-section of a ridge axis and the plumbing connected to a vent chimney

Sidescan sonar image overlaid onto multibeam bathymetry

A black smoker on the Galápagos Rift Zone.

Courtesy of UCSB, University S. Carolina, WHOI/NOAA

“Black Smoker”Hydro-thermalVent(at aMidOceanRidge)

Red-plumed tube worms

Courtesy of Monika Bright, University of Vienna, hydrothermalvent.com

External appearance of Riftia

© Dr. Ken MacDonlad/SPL/Photo Researchers, Inc.

Internal anatomy of Riftia

Aggregations of large vent crabs

Courtesy of Dr. Ana I. Dittel, University of Delaware

Aggregations of large vent clams

Courtesy of Dr. Ana I. Dittel, University of Delaware

Hydrothermal Vent Crab: Galtheid Crab (“Pinchbug”)

Vent and Seep Communities

• Diversity of Vent

• Inhabitants

Eyeless vent shrimp, Rimicaris, dominate deep hydrothermal

vents in the North Atlantic Ocean.

© Tim Shank, Woods Hole Oceanographic Institution

• Final Thought:

??? Connection to our “earliest life forms?”

Paleodictyon (500 million yr. old fossil)

Paleodictyon, 1976

• For more information on Paleodictyon, hydrothermal vent communities and deep sea research try the following web page link:

http://www.naturalhistorymag.com/0904/0904_feature.html

Covering: Dr. Peter Rona (Rutgers) and his Alvin research team

Film: “Volcanoes of the Deep” (IMAX)