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Hilary Term 1 > Climate and Life on Earth: Marine ecology 2 > Flashcards

Climate and Life on Earth: Marine ecology 2 Flashcards

1
Q

List the three major types of coastal tropical ecosystems

A
  • mangroves
  • seagrass meadows
  • coral reefs
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2
Q

Describe mangroves and seagrass beds

A
  • high biomass of primary producers
  • actively sequester huge amounts of carbon
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3
Q

Describe seagrass meadows - the basics

A
  • support high biodiversity
  • bottom-up and top-down controls in their productivity
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4
Q

Describe coral reefs - the basics

A
  • extraordinary biodiversity
  • threatened by overfishing, rising sea temperatures and coastal pollution
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5
Q

Many parts of the tropical oceans are virtual deserts, because

A

the permanent thermocline prevents vertical mixing and the return of nutrients from deep waters.

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6
Q

Describe the hot-spots of productivity throughout the tropics

A
  • sometimes due to upwellings
  • specialised communities of primary producers (e.g. coral reefs)
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7
Q

Describe mangroves

A
  • trees that grow in coastal brackish or saline habitats
  • flowering plants
  • trap sediments around their roots (salt mostly excluded)
  • need special adaptations, such as lenticels or pneumatophores
  • some spp have the ability to excrete salt through the leaves
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8
Q

Describe true mangroves

A

belong to a single genus: Rhizophora

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9
Q

Describe mangrove roots

A

often anoxic

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10
Q

Give an example of a mangrove species

A

Rhizophora mangle at Aldabra Atoll by Seychelles Islands

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11
Q

Describe seagrass meadows - the specifics

A
  • span both temperate and tropical locations
  • flowering plants
  • 72 spp globally
  • 4 families
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12
Q

Describe temperature seagrass beds

A
  • species-poor
  • often dominated by eelgrass: Zostera marina
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13
Q

Describe tropical seagrass beds - the basics

A

more species-rich

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14
Q

Describe seagrass

A
  • no stomata
  • thin cuticle
  • true roots and a vascular system (take up nutrients from the sediment, unlike algae)
  • spread rapidly via rhizomes
  • flower (produce pollen and seeds)
  • can grow at depths of up to around 55 m, mostly < 30m
  • directly grazed by green sea turtles and sirenians
  • world’s oldest plant: 200,000 year-old clones in Med
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15
Q

sirenians

A

manatees and dugongs

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16
Q

Describe seagrass morphology

A
  • roots
  • rhizome
  • flower
  • leaves
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17
Q

Describe small-bodied seagrass

A
  • small, thin leaves
  • small rhizome
  • “Guerrilla strategy”
  • short-lived
  • fas turnover
  • low biomass
  • exploits new space
  • abundant flowering
  • many small seeds
  • seed bank
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18
Q

Describe large-bodied seagrass

A
  • large, thick leaves
  • large rhizome
  • “Phalanx strategy”
  • long-lived
  • slow turnover
  • high biomass
  • holds space
  • patchy flowering
  • few larger seeds
  • seeds germinate rapidly
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19
Q

List some Floridian small seagrasses

A
  • paddle grass (Halophila decipiens)
  • star grass (Halophila engelmannii)
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20
Q

List some intermediate Floridian seagrasses

A
  • widgeon grass (Ruppia martima)
  • shoal grass (Halodule wrightii)
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21
Q

List some large-bodied Floridian seagrasses

A
  • manatee grass (Syringodium filiforme)
  • turtle grass (Thalassia testudinum)
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22
Q

Describe tropical seagrass meadows - the specifics

A
  • high biomass systems
  • high productivity
  • grow in coastal areas (incl. intertidal zone)
  • cope with some water turbidity and brackish water
  • grow alongside other tropical habitats like reefs
  • important nursery grounds for commercially important fish spp.
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23
Q

Describe tropical seagrass meadows and barrier reefs

A
  • protect by trapping sediment, absorbing excess nutrients and reducing turbidity in coastal waters
  • gain protection from wave action
  • synergism
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24
Q

List some estuary seagrass species in the tropical indo-pacific

A
  • Halodule spp.
  • Halophila ovalis
  • Halophila spp.
  • Enhalus acoroides
  • Ruppia maritima
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25
Q

List some shallow coastal/back reef seagrass species in the tropical indo-pacific

A
  • Thalassia hemprichii
  • Syringodium isoetifolium
  • Thalassodendron ciliatum
  • Cymodocea spp.
  • Halodule spp.
  • Halophila spp.
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26
Q

List some deep (70m) coastal seagrass species in the tropical Indo-Pacific

A
  • Halophila stipulacea
  • Halophila decipiens
  • Halophila spinulosa
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27
Q

Where are mangroves associated with seagrasses?

A

at tropical indo-pacific estuaries

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28
Q

Where are marshes associated with seagrasses

A

coastal tropical Indo-Pacific

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29
Q

Where is kelp associated with seagrasses?

A

tropical Indo-Pacific

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30
Q

Where is the sea turtle associated with seagrasses?

A

deep coastal tropical Indo-Pacific

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31
Q

Where is the dugong associated with seagrasses?

A
  • shallow coastal/back reef tropical Indo-Pacific
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32
Q

Where is freshwater input in tropical Indo-Pacific

A

deep coastal region

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33
Q

Describe one of the threats to coastal systems

A
  • eutrophication caused by runoff from agricultural systems
  • can lead to coastal dead zones
34
Q

Seagrass growth inhibits

A

Benthic microalgae

35
Q

Describe eutrophication

A

increased nutrient loading in water leads to blooms of phytoplankton

36
Q

Describe seagrass ecosystem engineering

A
  • Zostera noltii
  • trap silts
37
Q

Describe blue carbon

A
38
Q

Describe coastal wetlands in terms of carbon sequestration

A
  • substantial amounts (50-90% in soils)
  • long‐term carbon sinks
  • potential carbon sources upon conversion
  • managed for their carbon sequestration value
39
Q

Describe some taxa not involved in carbon sequestration

A

coral reefs, kelp, and marine fauna

40
Q

Describe long-term phytoplankton carbon sequestration

A
  • fix CO2
  • sink when dead to the bottom of the ocean
  • deep sediments lock up carbon
41
Q

Describe coastal wetlands

A
  • tidal inundation keeps the soils wet or submerged
  • inhibits microbial action
  • slows decomposition
  • carbon accumulates in soils and remains relatively stable
42
Q

Describe healthy coastal ecosystems

A
  • continuously accrete carbon in the soil
  • allows them to keep pace with sea‐level rise
  • potentially limitless capacity to sequester carbon for long periods of time
43
Q

Describe mangrove forest drainage

A
  • microbial action in the soil (previously inhibited by tidal inundation) oxidises carbon
  • emits it to the atmosphere as CO2
44
Q

Coastal wetland loss and drainage is estimated to be

A

between 0.7–3% per year (depending on vegetation type and location), resulting in 0.23–2.25 billion Mg of CO2 released

45
Q

Describe coral reefs - the specifics

A
  • temperatures between roughly 18 and 30 degrees
  • no sudden changes in salinity
  • high light intensity
  • low turbidity
  • oligotrophic waters
46
Q

Describe the two distinct biogeographic coral regions

A
  • Indo-Pacific (roughly 10x biodiversity)
  • tropical W Atlantic
47
Q

Describe coral spatially

A
  • missing from areas with major river outflows
  • sensitive to freshwater and silt
48
Q

Describe the types of coral reefs

A
  • fringing reefs (Israel)
  • barrier reefs (Australia)
49
Q

Describe fringing reefs

A

found just beyond shorelines

50
Q

Describe barrier reefs

A
  • found just beyond lagoons
  • start as fringing reefs
  • get hollowed out as a lagoon forms and becomes occupied by other life-forms, e.g. seagrass beds
  • reef survives further offshore
  • grows upwards towards the sunlight
51
Q

Describe coral growth

A

build massive structures through the accumulation of their limestone skeletons cemented together with sand

52
Q

Describe atolls

A
  • start growing on the shore of a high volcanic island as a fringing reef
  • island begins to erode and sink
  • weight of the volcano can cause subsidence
  • reef grows upwards, forming a barrier reef further offshore
  • lagoon between barrier reef and high volcanic island becomes wider and deeper
  • peak sinks beneath the water, leaving only the reef in place
  • island becomes an encircling barrier reef: an atoll
  • tens of millions of years to form
  • only kept at the surface through the action of the coral
  • e.g. Aldabra in the Indian Ocean
53
Q

What would happen if the coral of an atoll died?

A
  • continue to erode
  • end up under the sea
54
Q

Describe phylogeny of reef-building corals

A
  • scleractinian (stony) corals
  • within the class Anthozoa
  • within the basal phylum Cnidaria
  • arose during the mid-Triassic The ceonosarc creates a common gastrovascular system so that food can be shared among the polyps – they are all clones.
55
Q

Describe the morphology of reef-building corals

A
  • simple body plan
  • two germ layers: ectoderm and endoderm
  • mesoglea inbetween
  • muscles formed from the epithelial cells (retract and extend the tentacles)
  • secrete calcium carbonate skeletons and a corallite
56
Q

Describe coral ectoderm

A

contains cnidocytes

57
Q

Describe coral endoderm

A

contains photosynthetic algae

58
Q

corallite

A

protective cup

59
Q

Describe the ecology of reef-building corals

A
  • exist as single polyps or as a colony connected by coeonsarc tissue
  • colony can grow for years or decades, forming massive structures
60
Q

Describe Palaeozoic reef-building corals

A

went extinct during the Great Dying.

61
Q

Acropora

A

a branching coral

62
Q

Porites lutea

A

a boulder coral that is resisting coral bleaching quite well

63
Q

Describe coral reef symbiosis

A
  • photosynthetic algae called zooxanthellae in endoderm
  • coral provides protection for the algae and CO2 from respiration
  • also contributes other essential nutrients (e.g. nitrogen) from feeding
  • regulates growth and multiplication of symbionts
64
Q

Zooxanthellae

A
  • dinoflagellates
  • genus Symbiodinium
  • essential for coral growth (carbon provision, aiding calcification)
65
Q

Symbiodinium

A
  • free-living at low density in tropical waters
  • 30% of the biomass of a polyp
  • symbiont cells separated from host cytoplasm by symbiosomes
66
Q

symbiosome

A

specialised membranous structure

67
Q

Describe coral polyp dependence

A
  • on algae for nitrogen as well as carbon
  • symbiont produces amino acids using DIN from water column, and from nitrogenous waste produced by the coral
  • polyp acquires more than 80% of N from the algae when feeding rates are low
68
Q

DIN

A

dissolved inorganic nitrogen

69
Q

Describe carbon and nitrogen dynamics within the coral symbiosis

A

tight recycling

70
Q

Describe coral reef productivity

A
  • very high productivity (similar to the best agricultural systems)
  • corals keep most of the photosynthetic products; channel around 90% of the C fixed by their symbionts into their own growth (much of it is respired away)
71
Q

Describe algae on reefs

A
  • many kinds
  • coralline red algae
  • fleshy green and brown algae
  • provide a ‘turf’ for grazing fish (e.g. herbivorous surgeonfish)
  • herbivorous fish support predatory fish
72
Q

Describe coral reef biodiversity

A
  • probably the most biodiverse ecosystem on the planet
  • take up 1% of the ocean floor
  • support 25% of marine life
  • over ¼ of the world’s fishermen in 99 countries fish on reefs
73
Q

List some marine life that corals support

A

Sponges, echinoderms, nudibranchs, anemones, and lots of fish.

74
Q

Describe fishing on coral reefs

A
  • begin by targeting top predators (groupers, jacks and sharks); easily overfished
  • ‘fishing down the food chain’; targeting smaller herbivorous fish (e.g. parrotfish)
75
Q

Describe Jamaican coral reefs

A
  • chronic overfishing: began by targeting predatory fish, but then herbivores (e.g. parrotfish)
  • sea urchin boom: massive numbers of long-spined urchin Diadema antillarum kept fleshy algae in check, despite loss of herbivorous fish.
  • hurricane damage (1980) destroyed much of the Acropora species (short-lived coral recovery)
  • sea-urchin die-off (’82-’84): pathogen caused the death of 99% of urchins
  • loss of urchins and absence of fish caused dramatic bloom of benthic algae; prevents coral recruitment
  • phase-shift
76
Q

Describe phase-shift

A

reefs can exist in one of two states and that either is stable

77
Q

Describe El Niño/La Niña events

A

large-scale climate phenomenon that occurs every 3-8 years

78
Q

… of the Great Barrier Reef has bleached to death since 1995

A

Half

79
Q

average interval between bleaching events has … between 1980 and 2016

A

halved

80
Q

Coral bleaching occurs when

A
  • corals expel their symbiotic algae
  • exposed to prolonged high temperatures
  • high UV exposure also contributes
81
Q

What are the two main causes of coral bleaching?

A

t is thought to have two main causes:
Oxidative stress – the algae produce reactive oxygen and nitrogen species.
High temperatures cause the algae to become ‘selfish’ and stop exchanging nutrients with the host.

Hilary Term 1 (61 decks)

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