Deep Sea: IntroductionDeep Sea: Introduction

• The deep sea is the least understood ocean habitat

• It is less productive and more sparsely inhabited than ecosystems in the photic zone

• Poorly defined, but generally thought of as depths below those of the continental shelf (> 200 m)

• The deep sea is the least understood ocean habitat

• It is less productive and more sparsely inhabited than ecosystems in the photic zone

• Poorly defined, but generally thought of as depths below those of the continental shelf (> 200 m)

Biozones

Vertical Distribution• Epipelagic: upper 200-300 m water column; high diversity, mostly small and

transparent organisms; many herbivores

• Mesopelagic = 300 – 1000 m; larger than epipelagic relatives; large forms of gelatinous zooplankton (jellyfish, appendicularians) due to lack of wave action; some larger species (krill) partly herbivorous with nightly migration into epipelagic regimes 

• Oxygen Minimum Zone: 400 – 800 m depth, accumulation of fecal material due to density gradient, attract high bacterial growth, which in turn attracts many bacterial and larger grazers; strong respiration reduces O2 content from 4-6 mg l-1 to < 2 mg l-1

• Bathypelagic: 1000 – 3000 m depth, many dark red colored, smaller eyes

• Abyssopelagic: > 3000 m depth, low diversity and low abundance

• Demersal or epibenthic: live near or temporarily on the seafloor; mostly crustaceans (shrimp and mysids) and fish

The Deep Sea: Introduction (cont.)

• Bathypelagic Zone– perpetual darkness – 75% of the ocean; the largest habitat on the planet – constant temperature and salinity– organisms dominated by white, red, or black

coloration • some bioluminescence

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.

Variations of Deep Sea Benthos

• By substrate type

• By depth

• By food concentration

Deep Sea: Primary ProductionDeep Sea: Primary Production

• No photosynthesis below 150 m

• Typical organic composition of the sea bed– Continental shelf: 2-5%– Abyss: <0.5%

• No photosynthesis below 150 m

• Typical organic composition of the sea bed– Continental shelf: 2-5%– Abyss: <0.5%

Substrate Type

• Rocky habitats are rare

Substrate Type

• Soft sediments– Epifauna (on top of sediment)

– Infauna (within sediment)

Sampling the Benthos

• Grabs• Cores• Dredges• Trawls• Cameras

Smith-Macintyre Grab

Multi-corer

Cameras

Classification

Megafauna Rare, Largest animals

Macrofauna > 0.5 mm (usually retained on 0.5 mm)

Meiofauna 0.1 – 1 mm (passing 0.5 mm, retained on 0.062 mm

Microfauna <0.1 mm

Faunal Composition

Meiofauna

• Harpacticoid copepods

• Nematodes

• Small annelids

• Larger protozoa (ciliates, foraminifera)

Dominant groups of the deep sea floor

macrofauna

Dominant groups of the deep sea floor

macrofauna

• echinoderms- especially sea cukes and crinoids

• polychaetes

• pycnogonids

• isopods/amphipods

• echinoderms- especially sea cukes and crinoids

• polychaetes

• pycnogonids

• isopods/amphipods

Abyssal Polychaetes

• Small size• Reduced number of

segments• Reduced parapodia• Reduced coloration• Reduced eyes

Crustacea

• Amphipods

• Isopods (Gigantism)

• Tanaids

Molluscs

• Bivalves

• Gastropods

• Scaphopods (tooth shells)

Swimming sea cucumbers

• Enypniastes eximia can be up to a foot in length.

• Enypniastes is one of a small group of swimming sea cucumbers. It also feeds on bottom sediment, which it stuffs into its mouth with the tube feet surrounding the mouth.

CephalopodsCephalopods

• Some with weak swimming abilities (plankton)

• Other larger nektonic species

• Most are bioluminescent

• Some with weak swimming abilities (plankton)

• Other larger nektonic species

• Most are bioluminescent

CrustaceansCrustaceans• Shrimp, copepods, ostracods and euphausids• Most are bioluminescent• Tend to be purple or bright red in coloration

– Bioluminsecence flashes blue

• Shrimp, copepods, ostracods and euphausids• Most are bioluminescent• Tend to be purple or bright red in coloration

– Bioluminsecence flashes blue

FishesFishes• Most are small (2-10 cm)• Large mouths (many are hinged)

– Broad diets (anything they can fit in their mouths)

– Sharp incurved teeth• Coloration

– Tend to be silver-grey or black

• Most are small (2-10 cm)• Large mouths (many are hinged)

– Broad diets (anything they can fit in their mouths)

– Sharp incurved teeth• Coloration

– Tend to be silver-grey or black

Typical Characteristics of deep-sea pelagic fish

Benthic Fish

General characteristics of deep sea fishesGeneral characteristics of deep sea fishes

• low metabolic rate• less muscle mass: gelatinous• adapted for large rare meals:

large mouths and stomachs• use of lighting and

bioluminescence: most common in upper areas of deep (meso- and upper bathypelagic)

• low metabolic rate• less muscle mass: gelatinous• adapted for large rare meals:

large mouths and stomachs• use of lighting and

bioluminescence: most common in upper areas of deep (meso- and upper bathypelagic)

Biodiversity

Biodiversity of the Deep Sea• Each major ocean basin has distinctive fauna • Benthic deep sea is surprisingly diverse (100s of

species per m2 on ocean floor) but small

• Small-scale patchiness created by ephemeral food patches, etc

• Larger-scale upwelling disturbance, bottom boundary currents, slumping from continental shelves all create a diverse habitat

Inverse Relationship Between Biomass and Diversity

Bio

mas

s

Diversity

Reduced competitionIncreased specialization

Shallow

Deep

High Deep-Sea Diversity

High Diversity in Deep-Sea Sediments--Some Explanations

• Competitive co-existence based on niche partitioning and specialization

• Small-scale disturbances creates habitat heterogeneity

• Large-scale effects from currents enhance recruitment/dispersal and re-shape landscape

Endemism• Occurrence of organisms or taxa (termed endemic)

whose distributions are restricted to a geographical region or locality – high in abyssal plains– highest among trench fauna

Small-Scale Disturbances

• Food falls

Deep Sea: Food Sources

• rain of organic matter from above is sole source of food • exceptions - seep and vent communities

– chemosynthetic bacteria (chemoautotrophs)

What from above is eaten and how?What from above is eaten and how?• 30-40% of organic matter is first

absorbed by benthic bacteria, which are consumed by larger deposit feeders.

• Vast majority consumed by deposit feeders

• Small proportion by suspension feeders (~7%): attached to limited hard substrates: little water movement and little suspended food

• 30-40% of organic matter is first absorbed by benthic bacteria, which are consumed by larger deposit feeders.

• Vast majority consumed by deposit feeders

• Small proportion by suspension feeders (~7%): attached to limited hard substrates: little water movement and little suspended food

Whale carcass communities

• Whale carcasses provide a pulse of nutrients to deep-sea benthic communities, which form around them

• significant source of sulfides, methane for primary chemosynthetic producers

• serve as “stepping-stones” for many benthic species also found at hydrothermal vents and seeps

Whale falls

• This polychaete worm, discovered at a whale fall in the Santa Cruz. CA basin, is new to science and may be a whale fall specialist.

Finding mates is a problem in the dark

So animals use…

1. Bioluminescence

2. Chemical signals

3. Hermaphroditism

4. Male Parasitism

Sex in the Deep Sea

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)

Nature of Life in the Deep Sea Benthos

The Deep Sea: Hydrothermal Vents

A hydrothermal vent is a geyser on the seafloor

– It continuously spews super-hot, mineral-rich water that helps support a diverse community of organisms.

– Although most of the deep sea is sparsely populated, vent sites teem with a diverse array of life. (http://www.youtube.com/watch?v=gE0dJnXiHTo)

– Tubeworms and huge clams are the most distinctive inhabitants of Pacific Ocean vent sites, while eyeless shrimp are found only at vents in the Atlantic Ocean

The Deep Sea: Hydrothermal Vents

• The first hydrothermal vent was discovered in 1977, and hydrothermal vents occur in the Pacific and Atlantic oceans.

• Most are found at an average depth of about 2,100 meters (7,000 ft) in areas of seafloor spreading along the Mid-Ocean Ridge system— the underwater mountain chain that extends throughout the world’s oceans.

The Deep-Sea: Where are Hydrothermal Vents Found?

• The Mid-Ocean Ridge is the most volcanically active continuous zone on Earth.

• Vents are normally found along the crests of the Mid-Ocean Ridge

• One famous vent site is on the East Pacific Rise, an underwater mountain range close to the Galapagos Isl.

The Deep Sea: The Origin of Hydrothermal Vents

• How do hydrothermal vents form?

– In some areas along the Mid-Ocean Ridge, the plates that form the Earth’s crust are moving apart, creating cracks and crevices in the ocean floor.

– Seawater seeps into these openings and is heated by the molten rock, or magma, that lies beneath the Earth’s crust. As the water is heated, it rises and returns into the ocean through an opening in the seafloor

The Deep-Sea: Hydrothermal Vents• Hydrothermal vents form when

hot, mineral rich water flows into the ocean floor through volcanic lava on a mid-ocean ridge volcano formed by sea-floor spreading.

• Sulfide minerals crystallize from hot water directly onto the volcanic rocks at the same place where hot mineral rich water flows from the ocean floor.

The Deep Sea: Hydrothermal Vent Structure

• Chimneys top some hydrothermal vents. – These smokestacks are formed from dissolved

metals that precipitate when the super-hot vent water meets the surrounding cold, deep ocean water

• Black smokers are the hottest of the vents. They spew mostly iron and sulfide, which combine to form iron monosulfide. This compound gives the smoker its black color.

• White smokers release water that is somewhat cooler and often contains compounds of barium, calcium, and silicon, which are white

Hydrothermal Vents

Physical and chemical characteristics of vents

• Single chimneys arranged in a field 25-60 m across

• Black smokers (250-400 C)Rich in sulfides and toxic metals; low oxygen

• White smokers (5-100 C); short-lived (10-20 yrs in Pacific), with explosive endings

The Deep Sea: Hydrothermal Vents Impact Ocean Chemistry

• Seafloor hydrothermal systems have a major local impact on ocean chemistry of the ocean– Some hydrothermal tracers (especially helium), found

thousands of kilometers from hydrothermal sources, are used to study deep ocean circulation. Because hydrothermal circulation removes some compounds (e.g. Mg, SO4) and adds others (He, Mn, Fe, H2,

CO2), it plays an important role in governing

seawater mineral composition

Black Smokers

White Smokers

Hydrothermal Vents are Oases in the Deep Sea

• Rich and abundant biological communities, in contrast to most all of the deep sea

• Over 300 spp. described globally

• Some are cosmopolitan species-vestimentiferan worm Riftia pachyptila-mussel Bathymodiolus thermophilus-clams Calyptogena magnifica

Deep-Sea Vent Communities

• Around vent sites live communities of highly specialized animals

• Tube worms, mostly vestimeniferans (Riftia pachptila) & other organisms live in darkness, extreme pressure, and vent water temperatures from 10 to 400°C

• All these creatures depend on bacteria that use H2S from vent water as a primary energy source. These bacteria occur in the tissues of clams and tube worms and utilize the H2S which would otherwise be toxic to other organisms

Primary Production at Hydrothermal Vents

Chemolithoautotrophy= chemosynthesis

CO2 + H2S +O2 +H2O CH2O + H2SO4

• Bacteria do the fixing of carbon from CO2

• Symbiotic with other metazoans or free-living in mats

• CH4 (methane) may substitute in cold seeps

Primary consumers- Filterer and particle grazer

- Symbiotic hosts

Secondaryconsumers- Carnivores

Hydrothermal fluids as sources for material and energy

Primary productivity: MicroorganismsChemosynthesis

- Free-living cloud- and mat-forming organisms- Symbiotic bacteria

Hydrothermal ecosystems; the trophic levels

The Deep-Sea: Challenges of Living near Hydrothermal Vents

• Extremely high pressures affect the stability of enzymes necessary for survival.

• Low concentration of oxygen due to extremely high temperatures of surrounding water. Organisms must be strictly anaerobic.

• Extremely high temperatures may denature proteins/enzymes, destabilize organisms' transfer RNA, biological cofactors and organic intermediates.

Vestimentiferan worms

• Vestimeniferan worms (Riftia pachptila) found abundantly near deep-sea hydrothermal vents

The Deep-Sea: Special Adaptations for life

• In Vestimentiferan worms the Plume is a soft, bright-red structure that functions as a mouth. It takes in oxygen, carbon dioxide, and hydrogen sulfide that microbes living in the worm's body use for growth

• In hot water from the vent, these compounds can react violently. Yet, using special hemoglobins in its blood-rich plume (hence the red color), the tubeworm transports the ingredients in its blood without this reaction taking place -- and without H2S poisoning it

The Deep-Sea: Mutualisms play a role in the persistence of life

• Trophosome is a dark green-brown tissue where microbes (~ 285 billion bacteria per ounce of tissue.) live symbiotically within the worm

– The microbes get a safe place to live and give the worm its food.

– By absorbing CO2,O2 and H2S from the plume and controlling their reaction, the microbes use the chemical energy released from oxidizing sulfide to fix CO2 into organic carbon that nourishes both the microbes and the worm.

Secondary Production at Hydrothermal Vents

Bathymodiolus thermophilus

Secondary Production at Hydrothermal Vents

Calyptogena magnifica

The Deep Sea: Hydrothermal Vent Communities

• Pogonophorans (Vestimentifera)– tube worms

– no mouth, no stomach

• Sea Fans• Crabs• Shrimp• Snails• Clams

Mussel bed communities

Secondary Production at Hydrothermal Vents

Bresiliid shrimps

Bresiliid dorsal organs

Hydrothermal Vents Contained...

1 new class, > 14 new families, 50 new genera

These include mollusks, polychaetes, arthropods, with 93% of species described from vents and 90% restricted to vent habitats. Thus, there is high endemicity at vents

Colonization of Hydrothermal Vents

• Rapid growth and early maturity

• Overcoming special larval dispersal and recruitment problems

The ephemerality of vents (often lasting only a few years) requires...

Calyptogena (mussel) reaches maximum size (~240 mm) in 20 years, but may live as long as 100 yrs.

Possible ‘stepping stones’ between fields?

Cold Seeps

• Cold seeps are shallow areas where gases percolate through underlying rock and sediment layers and emerge on the ocean bottom

• The gases are methane and sulfur-rich gases and

sediments releasing petroleum

• Active seeps are located in subduction zones, which are areas where continental plates are being pushed together, with one diving beneath another

Cold Seep Communities

• One common type of organism that lives in the cold seep is a tubeworm

– These are related to the tubeworms that live in the hydrothermal vents.

• These organisms are the longest living invertebrates we know of.

– Estimated to have a life span of 170-250 years

– While similar in length to their hydrothermal cousins (~ 1-2 m long), they are slow-growing with a rate of one inch or less per year.

Cold seep communityGulf of Mexico

Similarities with vent taxa

White Regions Mark Areas of New Growth < 3 cm in a year = more than 100 yrs old.

Methane seeps• One of the most exciting organisms found at cold seeps is a

polychaete worm.

• This worm, known as an iceworm was found living on methane ice. – The iceworms, a new species of polychaete are the only

known animals to colonize methane hydrates.

– Many marine worms have a close relationship with bacteria. • Iceworms do not seem to play host to bacteria, but

traces of bacteria in the guts suggest that the worms do eat them.

Brine pool 13 m across is 4x saltier than seawater and rich in methane

Ice worms (polychaetes) living on gas hydrates in Gulf of Mexico

Gas hydrate is a crystalline solid consisting of gas molecules, usually methane, each surrounded by a cage of water molecules. It looks very much like water ice.

Methane hydrate is stable in ocean floor sediments at water depths greater than 300 meters, and where it occurs, it cements loose sediments in a surface layer several hundred meters thick.

The Deep Sea: The persistence of vent life

• The irony of vent communities is that, despite their harsh environment, they appear to have survived for many millions of years, and have apparently changed little in that time.

• Vent life appears to be more closely related to ancient animals than anything alive today.

The Deep-Sea: Did life begin at Hydrothermal Vents?

• While periodic mass extinctions have swept the Earth, vent creatures seem to have been unaffected, leading some to suggest that a vent-like environment was the place where life on Earth likely got its start.

• If this could have occurred here on Earth, why not on other planets that have the necessary ingredients, including heat, water, and the right mix of chemicals?

• In the end, there may indeed be a harsher place to live than hydrothermal vents. But it hasn't been found ... yet.

The Deep-Sea: What benefits can come from the study of Hydrothermal Vents

• Bacteria in this environment produce enzymes that may be valuable. Examples of possible uses include: development of heat stable enzymes and culturing bacteria designed to decompose toxic waste.

• Vents are rich in metals such as copper, zinc, iron, and gold.

• The discovery of life in these extreme environments has led to discussions about life on other planets such as Jupiter’s moon Europa.

Extremeophiles

Hydrothermal Vents on Mars Could Have Supported Life By Andrea ThompsonSenior Writerposted: 22 May 200802:00 pm ET

www.space.com/scienceastronomy/080522-mars-silica.html

Chemosymbiotic Bivalves 

Following discoveries at hydrothermal vents and hydrocarbon seeps, chemosymbiosis between bivalve molluscs and sulphide and/or methane oxidising bacteria is known from six different bivalve families. Of these, Lucinidae are most diverse and abundant, living from the intertidal to 2500 metres. All lucinid species harbor sulphide-oxidising Proteobacteria housed in the gills, from which they obtain much of their nutrition.

                                                 

Symbiotic bacteria in the gills of the lucinid Pegophysema philippiana (left), and in

the gills of Solemyarina velesiana (right). Images: John Taylor, NHM.

Large-Scale Disturbances

• Currents and deep sea benthic storms

Div

ersi

ty

VelocityIn

crea

sing

recr

uitm

ent

Reshaping landscape

Resuspension and burial

It is assumed that the biology and ecology of hydrothermal organisms may provide clues to the origins of life on Earth and, possibly, on other worlds.

Conditions in our planet’s primordial seas may have been similar to those surrounding hydrothermal vents, favoring the birth and evolution of extremophilic organisms.

Hydrothermal origin of life?

Extraterrestrial hydrothermal systems?

In the past, Mars had a thicker atmosphere.  Geothermal areas may have been conducive to life. Mars was once awash with great basins of water, but the water is thought to have disappeared or become subsurface ice as the planet cooled.

Photos from the CO2-ice covered polar caps indicate that the C02 ice erodes, adding carbon dioxide to the Martian atmosphere. This greenhouse effect would eventually warm the whole planet enough for water to return to the Martian surface.

Io is the volcanically most active body of our solar system - a possible source of energy for life. However, it seems to lack water.

Extraterrestrial hydrothermal

systems?

Europa’s surface is completely covered with ice. Under the 100 km thick ice sheet the existence of a large ocean is assumed. Europa's surface is -145°C cold. However, it is possible that hydrothermal vents, are spewing energy and chemicals into Europa's ocean.

Photo: NASA

Photo: NASA

Chemosynthetic Food Webs

• Sulfur bacteria in the tissues of clams and tube worms utilize the sulfates which would otherwise be toxic to other organisms

• This forms the basis of a non-photosynthetic food webs found throughout the oceans

Vents and Tectonic Activity

Niche Differentiation

• Habitat creation and modification

Rockall

Lock Etive