Deep Sea: IntroductionDeep Sea: Introduction

• The deep sea is least understood ocean habitat

• Less productive and more sparsely inhabited than ecosystems in the photic zone

• The deep sea is least understood ocean habitat

• Less productive and more sparsely inhabited than ecosystems in the photic zone

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

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

• Sieve size

Megafauna Rare, Largest animals

Macrofauna > 1mm (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 Polychaets

• Small size• Reduced number of

segments• Reduced parapodia• Reduced coloration• Reduced eyes

Crustacea

• Amphipods

• Isopods

• 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

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/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/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) • 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

Rockall

Lock Etive

High Diversity in Deep-Sea Sediments

• 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

Niche Differentiation

• Habitat creation and modification

Small-Scale Disturbances

• Food falls

Large-Scale Disturbances

• Currents and deep sea benthic storms

Div

ersi

ty

VelocityIn

crea

sing

recr

uitm

ent

Reshaping landscape

Resuspension and burial

Endemism

• High in abyssal plains

• Highest among trench fauna

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 very 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 very 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 fall

• 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.

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 fascinating array of life.

• 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 Islands.

Vents and Tectonic Activity

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

Marine Ecology:The Deep-Sea

• 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 out (form into particles) when the super-hot vent water meets the surrounding deep ocean water, which is only a few degrees above freezing.

• 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 cooler than their cousins’ and often contains compounds of barium, calcium, and silicon, which are white

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) are 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

Hydrothermal Vents

Physical and chemical characteristics of vents

• Single chimneys arranged in a field (a ‘vent field’)• Fields are 25-60 m across• Black smokers (250-400 C)

Rich in sulfidesToxic metalsLow oxygen

• White smokers (5-100 C)• Short-lived (10-20 yrs in Pacific)• Explosive endings

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 these 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°C to 400°C

• All these creatures are dependant on bacteria which 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

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 can transport the ingredients in its blood without this reaction taking place -- and without the toxic 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– 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 on the ocean floor where gases percolate through underlying rock and sediment layers and emerge on the ocean bottom.

• The gases found in the seep 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. – They are estimated to have a life span of 170-250 years

old. – While they are similar in length to their hydrothermal

cousins (~ one-two meters long), they are slow-growing with a rate of one inch or less per year.

Cold seep communityGulf of Mexico

Similarities with vents: similar 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 in a cold seep is a worm.

• The polychaete 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 on methane hydrates. – Many marine worms have a close relationship with

bacteria. • Iceworms do not seem to play host to bacteria, traces of

bacteria in the gust suggest that the worm 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

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.

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

Hydrothermal Vents

History of discovery

1979 ‘Rose Garden’ in the Galapagos Rift region

Black Smokers

Colonization of Hydrothermal Vents

• Rapid growth and early maturity• Overcoming special larval dispersal and recruitment

problems

Ephemerality of hydorthermal vents requires...

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

Possible ‘stepping stones’ between fields?

Secondary Production at Hydrothermal Vents

Riftia pachyptila

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

• The bacteria that thrive in this environment produce enzymes that are essential to industry. Examples of possible uses include: dislodging of oil inside wells; the development heat stable enzymes and culturing bacteria designed to decompose toxic waste.

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

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

• Deposition of one million tons of sulfide ore is something to think about in the future when our more accessible mineral deposits on land are being depleted rapidly.

Deep-Sea Vent Communities

• Around these vent sites live communities of highly specialized animals

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

• All these creatures are dependant on bacteria which use hydrogen sulphide from vent water as a primary energy source

The Deep-Sea: Challenges of Living in the Deep-Sea

• Bacteria utilize chemosynthesis and are primary producers that use carbon dioxide as a carbon source and gain energy through the oxidation of inorganic substances like hydrogen sulfide. This adaptation enables sulfur to be more readily utilized in chemosynthesis.

• The shrimp species that dominate hydrothermal vents in the Mid-Atlantic do not have eyes. Instead, some species have a sensor on their heads that is sensitive to high temperatures thereby enabling the organism to detect heat.

The Deep-Sea: Challenges of Living in the Deep-Sea

• 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.

• The difficulty in maintaining membrane fluidity at high temperatures.

Bioturbation

Varve formation in sediments

oxygenated

oxygenated

Depth Gradients1 order magnitude / 1000 m

Diversity Measures

Rarefaction curves

Species-area curves

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

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