Climate and Life on Earth: Marine ecology 1 Flashcards
Describe the global ocean
Earth’s largest habitat
List some oceans
- Pacific Ocean
- Gulf of California
- Gulf of Mexico
- Hudson Bay
- Caribbean Sea
- Atlantic Ocean
- Mediterranean Sea
- Southern Ocean
- Red Sea
- Persian Gulf
- Caspian Sea
- Black Sea
- Indian Ocean
- Arctic Ocean
Describe the structural features of the global ocean
- continental shelf
- continental slope
- oceanic trench
- abyssal plain
- mid-ocean ridge
- seamount
seamount
remains of dead volcanoes
mid-ocean ridge
volcanically active areas that can include deep-sea vents
Describe oxygen in water and air
- 40 times less oxygen in a litre of water than in a litre of air
- diffuses around 1000 times more slowly
- creates an oxygen minimum zone where respiration exceeds photosynthesis and diffusion from the air
Describe the establishment of a thermocline
- in the tropics and in summer at temperate latitudes a thermocline is established
- because warm water is less dense, it prevents vertical mixing and leads to nutrient depletion in surface waters
- in the tropics the thermocline is a permanent feature
List the light zones of the global ocean
- euphotic
- dysphotic
- aphotic
Describe the euphotic zone
- above 200m
- sunlight rarely penetrates beyond
- tuna
- aka sunlight zone
Describe the dysphotic zone
- above 1000m
- sunlight decreases rapidly with depth
- photosynthesis impossible
- shrimp, swordfish, hatchet fish
- aka twilight zone
Describe the aphotic zone
- lower than 1000m
- sunlight does not penetrate at all
- angler fish, giant squid, tripod fish
Where does most photosynthesis occur vertically speaking in the global ocean?
top 50m
Describe light penetration in the global ocean
- blue and green light penetrates much better than either red or violet wavelengths
- coastal waters are generally more turbid, so light attenuates more rapidly
Describe deep-sea fish
eyes which area adapted to see bioluminescence.
How far can violet light penetrate in the open ocean?
100m
How far can blue-green light penetrate in the open ocean
200m
How far can red light penetrate in the open ocean?
25m
How far can violet light penetrate in the coastal waters?
<10m
How far can blue-green light penetrate in coastal waters
50m
How far can red light penetrate in coastal waters?
15m
Roughly 1/3rd of the CO2 produced by humans since the industrial revolution has been
absorbed by the oceans
Describe a time series of carbon dioxide and ocean pH at Mauna Loa, Hawaii since 1955
- atmospheric CO2 increasing from 320ppmv to 400ppmv
- seawater pCO2 increasing from 320muatm to 380muatm
- seawater pH decreasing from 8.13 to 8.05
… current emissions continue to be absorbed by the oceans
1/2
Describe carbonate removal in the global ocean
- hydrogen ions react with existing carbonate ions in the ocean, forming bicarbonate
- poses problems for organisms with skeletons made from calcium carbonate
List some organisms with skeletons made of calcium carbonate
corals
Describe organisms that have skeletons made of calcium carbonate
- rely on carbonate being saturated
- as the ocean acidifies, their skeletons start to dissolve
- at a pH <7.5, this becomes critical
Surface currents
redistribute thermal energy
Describe surface currents
- rapid timescales
- driven by wind
- enormously important to Europe, as the NA drift brings warmer waters to us and prevents the freezing of the N Atlantic
- gyres have static centres – e.g. Sargasso Sea in Atlantic and the Great Pacific garbage patch.
List some surface currents
- Greenland current
- Labrador current
- North Pacific drift
- Gulf Stream
- California current
- north equatorial current
- south equatorial current
- Peru current
- South Pacific current
- Benguela
- canary current
- North Atlantic drift
- agunas
- west Australian current
- antarctic circumpolar current
- east Australian current
- Kuroshio current
- Kamchatka current
Great Ocean Conveyor belt
- redistributes nutrients
- much slower-moving but moves enormous volumes of water
- takes 100 years to move water N to S under the Atlantic Ocean. - thermohaline circulation
Describe thermohaline circulation
driven by differences in salinity and hence buoyancy, not by winds
How does the Great Ocean Conveyor Belt work?
- cold, high salinity seawater sinks
- warm shallow (surface) currents
- cold deep currents
Describe carbon fixation in the global ocean
50 billion tonnes per year
Describe some producers in the open ocean
- bacterioplankton (30 – 50%)
- phytoplankton
Describe bacterioplankton
- cyanobacteria
- e.g. Prochlorococcus
Describe phytoplankton
- diatoms
- dinoflagellates
- coccolithophores
Describe diatoms
skeletons made from silica
Describe dinoflagellates
2 flagellae
Describe coccolithophores
calcium carbonate skeleton
Define deep subsurface
marine subseafloor sediment and the oceanic crust, as well as the terrestrial substratum deeper than 8 m, excluding soil
Describe marine vs terrestrial biomass in Gt C
- marine = 6
- deep subsurface = 70
- terrestrial = 470
Marine ecosystems are characterised by (relative to terrestrial and deep subsurface)
- few fungi
- lots of protists
- lots of animals
- few bacteria and archaea
archaeplastida
red and green algae
List some marine protists
- phytoplankton
- brown algae (e.g. kelps)
Describe marine animal biomass
dominated by fish and crustaceans
Break down marine biomass in Gt C
- protists: 2
- animals: 2
- bacteria: 1.5
- plants: 0.5
- fungi: 0.3
- archaea: 0.3
- viruses: 0.03
List some marine consumers in order of biomass (Gt C)
- animals
- protists
- bacteria
- archaea
- fungi
List some marine producers in order of biomass (Gt C)
- protists and plants
- bacteria
Describe food webs in the open oceans
- vary dramatically
Describe small zooplankton
- excrete tiny faecal pellets
- forms POM
- nutrients are rapidly returned by heterotrophic bacteria
- vertical movement during the 24-hour cycle ‘pumps’ carbon to the depths
Describe the microbial loop
- hugely important for recycling DOM
- massive, due to prevalence of viruses in ocean (10 million per millilitre of seawater)
Describe upwellings
support large phytoplankton (e.g. large diatoms) can be grazed directly by small fish, leading to massive fish biomass (e.g. anchoveta)
POM
- particulate organic matter
- sinks
DOM
dissolved organic matter
What limits primary production in the open ocean?
light in temperate and polar regions
Describe temperature latitudes
- high productivity
- major boom in spring
- smaller boom in autumn
North polar peaks in
July
Upwellings of nutrient-rich water can create
- hotspots of high productivity in coastal waters
- common along the W coasts of continents: e.g. in California, Chile, Peru
Describe the effects of strong vertical mixing and the lack of a thermocline in winter
temperate and polar waters are nutrient-rich
Describe the effect of the permanent thermocline in the tropical oceans
prevents vertical mixing and the return of nutrients to the euphotic zone
Describe the Peruvian anchoveta
most heavily exploited fish in the world.
Describe the coastal ocean at mid-latitudes
- roughly 60% of the human population (4Bn people) live within 100 km of the coast.
- coastal seas lie above the continental shelf
- highly productive because of strong vertical mixing (especially the W coasts of continents)
- heavily exploited and heavily polluted
- oil spills are a constant threat
Describe the pollution of the coastal ocean
agricultural run-off has created enormous dead zones that expand every year.
… of coastal fisheries are responsible for nearly … of the world’s wild-caught seafood
40%, 40%
Describe the kelp forest
- major temperate coastal ecosystem
- economically important
- directly harvested
- supports important fish and shellfish
Describe mid-latitude kelp forests
- abundant
- support a high diversity of life
- ecologically unstable
- sensitive to over-harvesting of key animals
Describe kelp
- multicellular brown algae
- often annual
- no true vascular system
- differentiation into multiple cell types
- can be highly productive
- support enormous biodiversity (30 to 70 species can live just within a single holdfast)
- significant 3D structure
- ecosystem engineer
- nurseries for commercially important fish species
- very high C:N ratio
- chemical compounds deter grazers
List some kelp genera
- Laminaria
- Macrocystis
- Nereocystis
- Lessonia
- Ecklonia
Which are the dominant kelp genera?
- Laminaria
- Macrocystis
Describe the multiple cell types of kelp
- holdfast
- stipe
- blades
Describe Macrocystis
- can grow up to 30cm/day
- reach a height of 30 m
- dense underwater forest.
Describe kelp stipe
- supports many epiphytes
- e.g. Phycodrys rubens.
Phycodrys rubens
red alga
Describe red algal communities
- flourish under the kelp forest
- 40-180 spp around the UK
- support large numbers of invertebrates
List some of the invertebrates supported by red algal communities
- brittle stars
- anemones
- crabs
- jellyfish
Which commercially important fish species to kelp nurture?
- US rockfish
- European lobsters
Describe sea urchins on kelp
- if reach a high enough population density and following a disturbance, can prevent kelp from regenerating
- convert a kelp forest into an urchin barren (does not then recover)
Describe kelp specialists
- blue-rayed limpet (found at low tide around the UK)
- sea-urchin (specialises on eating the holdfast)
Describe sea urchins
very high reproductive rates
Describe urchin population control
- top-down controlled
- by predators, rather than by food
Describe Enhydra lutris
- Sea-otters
- marine mammals
- feed on shellfish and echinoderms (sea urchins)
Describe sea otter hunting for fur
- began in Russia in the 18th Century
- spread down the W coast of N America during the 19th Century
- by 1911, reduced to around 2000 animals
- hunting banned
Describe Sea otters and kelp
- around Alaska, significant recovery of kelp forests occurred as sea otters expanded their range
- pattern repeats along much of the W coast of the US
- otter = keystone species
- control urchins
- allow kelp forests to flourish
Describe kelp forests in N California
- collapsed
- warmer waters, strong El Nino events and a disease of the sunflower sea star
El Niño events
block coastal upwellings
Pycnopodia helianthoides
sunflower sea star
Describe urchin barrens
‘alternative stable state’ phase shift
