Transcript 2008, final Lecture 12 deep sea and hydro vents

Deep 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: 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 Production
• 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
> 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
• Sieve size
Faunal Composition
Meiofauna
•
•
•
•
Harpacticoid copepods
Nematodes
Small annelids
Larger protozoa (ciliates, foraminifera)
Dominant groups of
the deep sea floor
macrofauna
• 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.
Cephalopods
• Some with weak
swimming abilities
(plankton)
• Other larger nektonic
species
• Most are
bioluminescent
Crustaceans
• Shrimp, copepods, ostracods and euphausids
• Most are bioluminescent
• Tend to be purple or bright red in coloration
– Bioluminsecence flashes blue
Fishes
• 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 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)
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
Shallow
Biomass
Reduced competition
Increased specialization
Deep
Diversity
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
Diversity
• Currents and deep sea benthic storms
Reshaping
landscape
Velocity
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?
• 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 seafloor 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 superhot 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 sulfides
Toxic metals
Low 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 deepsea 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
The ephemerality of vents (often lasting only a few
years) requires...
• Rapid growth and early maturity
• Overcoming special larval dispersal and recruitment
problems
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 community
Gulf 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 ventlike 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 Thompson
Senior Writer
posted: 22 May 2008
02:00 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
Ephemerality of hydorthermal vents requires...
• Rapid growth and early maturity
• Overcoming special larval dispersal and recruitment
problems
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
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
oxygenated
oxygenated
Varve formation in sediments
Depth Gradients
1 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 nonphotosynthetic food webs found
throughout the oceans