Marine Flashcards
1
Q
What are the different parts of the ocean?
A
Litoral zone: the area that generally gets uncovered on a daily basis (when tides go out).
Neritic = near shore waters; oceanic = waters in ocean.
Pelagic: the whole water region (neritic + oceanic)
There are subtidal regions and then continental slope, then deeper regions.
Anything that chooses to live at the bottom = Benthic.
Planktonic: free-swimming in oceans; Benthic on the bottom (Attached or free living)
Photic: the photic zone is often measured to find out the level of light penetration; it varies in depth dep on location, could be deeper, ~1% light level 200m down.
2
Q
why is water an excellent solvent?
A
It dissolves more substances and in greater quantities than any other common liquid: salts, sugars, acids, alkalis, and some gases including oxygen and carbon dioxide
Cell components such as polysaccharides, proteins and DNA are dissolved in water and derive their structure and activity from interactions with water
3
Q
What are the key nutrients that cause the most problems in the ocean?
A
These key nutrients arrive through river run off (sometimes nitrogen from rain + snow)
- Hydrothermal vents might also add sulfide + chlorides
- These all contribute to salinity of oceans + you can use a refractometer to measure salinity of our oceans.
4
Q
how many ions make uo 99% of the ocean?
A
Six ions make up ~99% of the salts dissolved the ocean with Na and Cl making up 85%
5
Q
why is borate important?
A
without low concs, a lot of things can’t survive - this is in trace concentrations.
6
Q
how is a Rosette of submersible water samplers with probes used to measure the salinity / other things about the ocean?
A
There are collumns you can detach from the core, and when you send a messenger, it will trigger one of them to close. This means that at a certain depth you will trap water at intervals by operating a different column each time í depth profile of the oceans. You can also get temperature info etc.
7
Q
how are oxygen minimum zones replenished?
A
by ocean circulation
Oxygen circulation solves most problems with oxygen minimum zone
8
Q
how can light penetration in oceans be measured?
A
- Secchi disc( - simple, painted areas of black / white, put on cable + lower it into water column until disappears, used a lot in FW) , or submersible ‘photocells’ or quantum metres - needed in oceans: they measure wavelengths of light / or just measure at the top + lower at intervals + get the attenuation of light in the water column.
- Photocells with colour filters allow you to work out wavelengths: in oceans blue light penetrates deeper than red. UV attenuated quickly, at low levels dissolved organic carbon will stop it going which is good because this is dangerous
- In FW more green light.
9
Q
What are the different light levels in the ocean? how is light penetration different in oceanic + coastal waters?
A
euphotic or photic is zone where there is enough light for photosynthesis (more or less down to 1% of surface light).
- Disphotic or dysphotic zone has enough light for organisms to see and aphotic does not.
- Water penetrates much further in clear oceanic than in turbid coastal waters : in clearest oceanic waters, penetrates to over 1000m in sunlight, but in coastal waters only to 200m.
10
Q
why are salinity ocean profiles variable?
A
due to rainfall, evaporation and river run off
11
Q
why do seasonal thermoclines arise and why are they bad?
A
- Surface layer (warm); intermediate layer (permanent thermocline) + Deep layer (very cold but generally a constant temperature)
- Temperature and density are mirror images of each other
- In temperate and polar waters a ‘seasonal thermocline’ may develop: during the summer there can be another thermocline that happens much higher up - temporary thermocline causes layering of water in the upper layer - pink region. - when you get a T gradient, hard to break it down (water lower down doesn’t mix), orgs trapped in layers can run out of nutrients because of this lack of nutrients)
12
Q
What is the Coriolis effect?
A
Currents + winds are:
- Deflected to the right in the northern hemisphere
- Deflected to the left in S. hemisphere
13
Q
Why does the polar zone only have a late spring boom?
A
dark much of the year until late spring: - only a narrow opportunity.
14
Q
What makes regions of coastal upwelling good fishing grounds?
A
- Prevailing wind blows parallel along coast + Ekman transport carries surface water away from shore at 90 degree angle
- Deep, nutrient-rich water is upwelled to fill the gap, making it very productive
- This fuels the fisheries + birds.
15
Q
How do organisms cope with wave action?
A
o Mobile organisms can shelter from wave action (or ‘clamp down’)
o Low profile
o Sessile organisms can adapt to withstand wave action
o Giant green sea anemone (Anthopleura xanthogrammica)
o Compact shape reduces area exposed to wave action and water moves easily over them
16
Q
Adaptations to wave action in kelp (brown seaweeds) - how?
A
o Flexible stipe
o Streamlined shape
o Strong holdfast
o Might lose photosynthetic blades but meristem helps them regenerate
17
Q
Coping with wave action - Going it alone or in groups(mussels)? (advantage vs disadvantage)
A
- Large single exposed mussles tron away
- Clusters reduce exposure, water flows over
- Too large cluster, too much strain on those attached to the rock –> torn away
Subtle balance to survive on the rocky shore
18
Q
Name challenges of Variable periods of immersion and emersion
A
o Variable periods of desiccation + of time in light
o Exposure to UV and exposure to salinity gradients (rain)
o Wind activity (important for desiccation
o Lack of food ~12h without water if at the top (~3h in the middle, ~30min at the bottom) í shot window of opportunity
19
Q
When are the largest tide-greatest tidal amplitudes?
A
New moon and full moon
Spring tides = greatest gravitational pull (march and September have the strongest tides)
Every day tide advances ~1h: differences in exposure every day
20
Q
Define Supralittoral/Littoral fringe/Splash zone, Intertidal/Eulittoral zone/Midlittoral and Sublittoral
A
The supralittoral zone, also known as the splash zone, spray zone or the supratidal zone, is the area above the spring high tide line, on coastlines and estuaries, that is regularly splashed, but not submerged by ocean water. Seawater penetrates these elevated areas only during storms with high tides.
The intertidal zone, also known as the foreshore and seashore and sometimes referred to as the littoral zone, is the area that is above water at low tide and under water at high tide (in other words, the area between tide marks).
The sublittoral is the environment beyond the low-tide mark and is often used to refer to substrata of the continental shelf, which reaches depths of between 150 and 300 metres.
21
Q
How do Littorina cincta (periwinkle) protect themselves at low tide?
A
o Periwinkle: Move to moist crevice, clamp to rock and seal shell with operculum (part of exoskeleton that will close over hole to avoid desiccation)
22
Q
What are Zonation Patterns?
A
o Typical vertical zonation patterns
o Tend to follow a predictable pattern
o Different zones dominated by different organisms
o The pattern may shift due to turbidity, degree of exposure, pollution, temperature, etc.
23
Q
What happens after an oil spill?
A
o Surfactant killed organisms, recolonization was observed
o Pioneers that could capitalise on bare surfaces took over: Enteromorpha (green seaweed) (renamed as Ulva now)
o Animals come back later (limpets, Patella spp.); start grazing on the weeds and biomass overall goes down
o Ca. 10 years to recover from oil spill estimated
24
Q
Removal experiments: what happens when you remove starfish?
A
Starfish as a structuring force (predation): they are voracious predators.
o Spring 1963 to summer 1968 manually removed sea stars (Po) in Mukkaw Bay o Mussels (Mc) colonise further down shore, replacing barnacles (Pp)
Starfish maintain the diversity of the mid-intertidal region (see text book pp. 258). Without sea stars to eat the mussels, the mussels outcompete everything and dominate the shore (=keystone species).
25
Explain the Intermediate Disturbance Hypothesis
The intermediate disturbance hypothesis (IDH) suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct.
o Initially it was thought that there were 'predictable' zones on the rocky shore
o But zones are not fixed in position and species can migrate up and down
o When a clear patch occurs, patterns of recolonization and regrowth (or succession) can be difficult to predict
o What regrows may depend on what reaches the space, the time of year, size of space, etc.
26
What are some biological differences between Antartica and the Artic?
6x the species found in the Antarctica.
Very high biomass in the Antarctic: indication that it must be much harsher in the Arctic.
In antartica: • High diversity of soft and hard benthic habitats --> High diversity of epifaunal and infaunal benthos - because there is Different substrates enabling different sorts of attachment/nutrients/gradients of gases
Biotic disturbance high in the Artic (bioturbation of sediment (sandy sediment very easy to disturb)
27
What are the different types of feeding of benthic organisms?
Filter feeding: suspension feeding in which water is actively pumped or filtering structures are swept through the water
Passive suspension feeding: no active pumping of water but use of cilia + mucus to move particles to mouth.
Deposit feeding: feeding on particulate organic matter that settles on the botom
Biological differences – the Arctic
28
What are some physical differences between Antarctica + the artic?
Narrow shelf and exchanges with the deep ocean in the Antarctic; Less connectivity in the Arctic.
Big difference in the river output (there is none in the Antarctic). Can be negative but also nutrients: less stable salinity in the Arctic, changes as river water comes in.
Cooling at the poles (water has greater density), but in Antarctica, clear run all around (circular). In arctic, limited strait and transpolar currents.
Euphoric zone nutrients: in Antarctic, no limitation in primary productivity during summer (experienced in temperate regions).
High seasonality in pack ice in Antarctic, cover and thickness of ice vs little seasonality in the Arctic.
29
What are the two straits in our oceans?
The Fram Strait is the passage between Greenland and Svalbard
The Bering Strait is a strait of the Pacific, which borders with the Arctic to north. It is located between Russia and the United States.
30
What may climate change lead to in terms of our oceans + the movement of organisms?
huge impact of climate change here because there all the ice free conditions in the Canadian artic that lead to connectivity between oceans impact on primary producers.
31
What are some features of the Southern Ocean?
* Deep water and pelagic marine ecosystems open to Pacific, Indian and Atlantic Oceans.
* Species reliant on the continental shelf are isolated.
* Two circumpolar surface currents.
* Deep or open water species are well distributed
* Creates a convergence zone = upwelling of nutrient rich deep water.
32
why can there be high summer productivity in the southern ocean?
* Phytoplankton blooms occur along convergence zone (upwelling of nutrient rich deep water) and ice margins.
* Biomass at any given depth in Southern Ocean are 10x to 100x that of the same depth in the Arctic Ocean.
33
Where are the coldest waters on Earth?
• Antarctic continental shelf waters coldest anywhere on Earth = 0 to -1.9°C
34
What are some differences in ice cover between the artic + Antartica?
Arctic
• Arctic pack ice is more persistent, harder and thicker than Antarctic.
• Central Arctic permanent ice cover.
• Average age 10 years.
Antarctic
• Antarctic pack ice cover more seasonal.
• During winter cover ~19 million km2 of ocean = 2x USA.
• Dramatic year-year variations in pack ice extent (significant changes: due to climate change?)
35
what are the different types of ice?
* Sea ice (pack ice): Formed from saltwater - freezing onto base of pack ice
* Icebergs are chunks of ice shelves or glaciers that calve into the ocean
* Ice shelf (continental ice sheet or glacier – i.e. formed on land – extends onto the sea.) Formed from snow = freshwater
36
why is sea ice a rich feeding ground?
High species richness in the zooplankton communities: are waiting for ice to melt to release organisms such as diatoms.
Sea ice and primary productivity
• As sea ice melts in Spring it provides a “seed” population for plankton blooms along the ice edge.
37
What make the southern Ocean food current possible?
* Simple, short & efficient.
* Primary producers & Primary Consumers, then whales
* Based predominantly on a single zooplankton species, Antarctic Krill
* Dependant to organisms like diatoms
* Circumpolar current and upwelling make this possile
38
What happens in the oceans in the absence of krill?
salps can exploit spring phytoplankton bloom and undergo explosive population growth.
• High densities in years following low ice cover.
• Tolerate warmer water than krill.
39
What are ice sours and how are they produced?
Caused by icebergs or hard pack ice, physical force that will strip off everything on the bottom. Seabed gouging by ice is a process that occurs when floating ice features (typically icebergs and sea ice ridges) drift into shallower areas and their keel comes into contact with the seabed. As they keep drifting, they produce long, narrow furrows most often called gouges, or scours.
40
What are the effects of ice sours on a regional + local scale?
• Local scale:
o high faunal mortality
o skewed population structures
o dominance by mobile secondary consumers (e.g. echinoderms, crustaceans).
• Regional scale:
o promotes biodiversity & habitat heterogeneity
41
What is the relationship between Polynyas and penguins? Why is this so?
90% of Adélie and Emperor penguin colonies are sited next to recurrent coastal polynyas. Ep breeds on fast ice cover.
Polynyas: ‘sea ice factories’ = an area of open water surrounded by sea ice. Able to receive benefit for all of the upwelling water (far more productive) and represents important feeding area. Can be produced by katabatic winds
42
Define Estuaries
Estuaries - semi-enclosed areas where rivers meet the sea (Chesapeake Bay, Delaware River, Cape Hatteras)
Many types of estuary; Drowned river valley estuaries; Bar-built estuary
43
What is a Fjord?
Fjord - a long, narrow, deep inlet of the sea between high cliffs, as in Norway, typically formed by submergence of a glaciated valley.
Much clearer and much deeper, less turbidity than estuaries (Milford Sound, New Zealand)
44
What are the 6 Physical Characteristics of Estuaries?
1) Salinity (v variable)
2) Tides (tidal inundation)
3) Oxygen (concentration v variable bc of organic matter in estuaries)
4) Nutrients
5) Sediments
6) Turbidity(much harder to live in water column)
45
How does the salinity in estuaries vary, why is that and what effect does that have?
Salinity: typical salt-wedge type estuary;
--> Saltwater is denser than the freshwater (river) and flows along the bottom
o Salinity is highly variable; the salt wedge can move up & down the estuary with the tides
o Also, daily and seasonal variations in tides and river flows
o Huge amount of osmotic stress on organisms
o Actual volume of water coming from the river very variable
46
What is the sediment in estuaries made out of and what is the Estuarine Turbidity Maximum?
Sediment =Large amounts of organic (& non-organic) particles associated with the tide and river flow. Organic matter will flocculates.
Estuarine Turbidity Maximum - organic matter flocculates where it meets the salt wedge (form part of the sediment).
o Maximum aggregation of particles where seawater and freshwater meet
o Settles to form a nutrient rich mud, but turbidity reduces light penetration reducing photosynthesis
47
What are the 4 types of organisms with different salinity tolerances called?
o Stenohaline - narrow tolerance to salinity changes (marine species; 30 parts/1000)
o Euryhaline - broad tolerance to a range of salinities
o Truly estuarine =blackish water species (brackish water = intermediate salinity and contains stenohaline & euryhaline organisms)
o Freshwater species
--> Organisms can move and avoid, or seal themselves away, from extremes of salinity. But euryhaline organisms need a physiological response.
48
What is a Perfect osmoconformer and a
| Perfect osmoregulator ?
Perfect osmoconformer - salinity of blood matches that of water (salmon).
Perfect osmoregulator - salinity of blood (ionic concentration) stays constant even though external salt concentrations varies (crab).
49
Define mudflats and what properties do they have?
Mudflats: deposits of sediment in sheltered intertidal areas (like estuaries)
--> Salinity changes are less dynamic in interstitial water, more stable environment within the mud.
--> Plentiful nutrients and though biodiversity may be low, primary production may be very high…
o Sediments can be anoxic (only top few cm oxygenated, with anaerobic bacteria living underneath)
o Hydrogen sulphide accumulates in mud and can be toxic
o Anaerobic bacteria can thrive
50
What are the Primary producers in estuaries?
```
o Phytoplankton (e.g. dinoflagellates, bc they have flagella, they can ride the salinity layers and capitalise on that í don't need to tolerate big osmotic fluxes)
o Macroalgae (seaweed)
o Macrophytes (seagrass)
o Benthic biofilms (microphytobenthos)
o Saltmarsh plants (halophytes)
```
51
On the energy budgets in estuaries What are the 2 Carbon supply extremes?
Carbon supply can be (2 extremes)
o Allochthonous: depend on external sources e.g. Dollard (in the Netherlands, 46% coming from North Sea and River Ems, too dark for phytoplankton so less production)
o Autochthonous: fixed by primary producers within estuary e.g. Barataria estuary (39.6% of carbon input from saltmarshes at edge of estuary --> American estuary: greater intertidal properties)
52
Define infauna in estuaries
Infauna: benthic organisms that live within the bottom substratum of a body of water (i.e. capitalise on the mud)
```
o Snails (live in burrows, capitalising
on the organic water falling down
in the water column: scavenging)
o Polychaete worms
o Clams
o Crustaceans
```
53
What are the temporary visitors in estuaries?
```
Atlantic medhaden (Brevoortia tyrannus) uses the estuary as a nursery but breeds at sea as do many other fish and shrimps.
Blue crab (Callinectes sapidus) females can undergo long migrations to spawn at sea, before their young move into the estuarine environment
```
54
What are the 2 migration types?
Anadromous: migration from sea to freshwater to spawn e.g. salmon
Catadromous: migration from freshwater to sea to spawn e.g. eels
55
What are saltmarshes?
Saltmarshes: upper intertidal zone between land and open salt water or brackish water that is partially flooded by high tides. Get colonized predominantly by cordgrass (stabilization of sediment, allow higher plants to move in)
o Dominated by salt tolerant plants
o Like mangroves & mudflats, saltmarshes often associated with estuaries
o Saltmarshes are replaced by mangroves in tropical regions
56
What organisms live in saltmarshes and what happens to them?
o Barataria Bay ecosystem the extensive salt marshes provide the largest source of carbon
o Saltmarsh can be critical to estuary ecosystems
o In the US they tend to be more extensive, dominated by cordgrass;
o Major plants in the saltmarsh are unpalatable
o Get broken down physically and biologically (changes proportion of carbohydrate and protein, increase protein proportion)
o Colonized by bacteria and fungi, facilitating break down?
o Converted into detritus
o Carbon : Nitrogen ratio changes (increasing N)
o Carbohydrate falls, protein increase - making them more nutritious
57
What species has been found to feed on cordgrass (found in saltmarshes)?
Ragworm Hediste diversicolor: Lives in mud flat and saltmarsh area: can feed on cordgrass.
Sprouting as a gardening strategy to obtain superior supplementary food.
Worm is taking grass down into burrow from mud surface (washed down from saltmarsh)
58
What species is known as the 'saltmarsh assassin'?
Periwinkles, the spiral-shelled snails commonly found along rocky U.S. shorelines, play a primary role in the unprecedented disappearance of salt marsh in the southeastern states.
o Strong top-down control exerted by crabs and terrapins
o Snails recruit better in tall grass zones where Nitrogen availability is higher
o Marsh plants grow better in regions of high N and this is where adult snails were more abundant
59
Name 2 types of feeding in estuary species
o Deposit feeder - feed on detritus (and associated microorganisms) in sediment
o e.g. California hornsnail Cerithedia californica
o Suspension feeders - catch falling detritus still suspended in the water column
o e.g. spaghetti worms; terebellid worms
60
Name 4 species living in saltmarshers
Ribbed Horsemussel (Geukensia demissa) lives in saltmarsh, half buried in sediment - it is a suspension feeder. It can 'gape' at low tide to take in oxygen
Macoma genus of clams buried in the mud, and extends two narrow siphons to the bottom surface. Through the siphons, it feeds on organic matter on the sediment surface or in the water. Density of the clam Macoma reach 3,500 m-2 in Bay of Fundy
Hydrobia genus of snails responds to eutrophication and reaches very high densities of 34,000 m-2 , it is a grazer and breathes via gills, feeds on diatoms, bacteria and mucus
Lugworm (Arenicola marina) annelid worm that lives in a characteristic burrow and ingests sediment to feed on detritus and micro-organisms within. Produce the distinctive casts on beaches.
61
What are sea grass beds?
Made out of Seagrasses which are flowering plants (angiosperms) belonging to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the order Alismatales (in the class of monocotyledons), which grow in marine, fully saline environments. There are 12 genera with some 60 species known.
62
What animal do seagrasses provide an important food source to?
o Seagrasses provide an important food source for dugongs and manatees
o Hypothesized that the dugong, grazing on seagrass beds in Australia, could reduce the biomass by 96% (Preen, 1995)
o Seagrass beds themselves threatened by seagrass wasting disease (see Pg 296 in text book), eutrophication & boat damage
63
What is a top-down effect?
o Top-down effects - predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function
64
What is a trophic cascade?
when predators limit the density and/or behavior of their prey and thereby enhance survival of the next lower trophic level (powerful indirect interactions that can control entire ecosystems)
65
How is the depth of the ocean floor measured?
Historically, depth measured by lowering rope on a steam winch. Effective method of working (even with 10km of rope) í Discovered "Challenger Deep" (11,022m).
Our knowledge of the ocean floor
o Topography crudely known
o Bare idea of what organisms are there
Sonar signals that bounce back and give you a 3D image of the ocean floor.
Multibeam echosounder: Attached to submersibles to map the ocean floor.
66
What do we know about continental shelves?
o Under neritic zone
o Under water during interglacial periods
o End at the shelf break (or shelf edge
o UK on the European continental shelf
o Estimated 8% of sea surface area (cyan)
o Important because accessible for fisheries (and trawling), shipping (because sheltered), hydrocarbons (oil, gas), renewable energy (wind farms, tidal barrages), aquaculture, recreation (sailing).
67
What are the types of continental shelf communities?
a) Soft bottomed benthic
b) Seagrass beds
c) Hard bottomed benthic
d) Kelp forests
68
What do we know about Soft bottomed benthic habitats?
o Characterised by vegetation-free, sediment rich habitats
o Sediment type determined by water movements (waves, currents, upwelling) and geological history (glacial deposits)
o Typically coarser sediments are found closer to shore
o Suspension feeders: sponges, some molluscs
o Macrofauna (>0.5mm), meiofauna (0.065-0.05mm) and microfauna (bacteria, dinoflagellates, diatoms)
o Infauna (in substrate) and epifauna (emergent)
69
What do we know about the Seagrass bed habitat?
o Species normally prefer either cool waters or tropical/subtropical waters, but not both normally
o Density of seagrass plants tends to be very high - see right
o Support a diversity of epiphytic species, as well as free living
o Seagrasses form the basis of complex food webs
70
What do we know about Hard bottomed benthic/ sublittoral habitat
o Harder / shelly substrates harder to burrow into (used to being underwater all the time)
o Communities dominated by rich epifauna, but poor infauna
o Sessile species: sponges, hydroids, anemones, bryozoans, polychaetes, barnacles, sea squirts
o Motile species: urchins, limpets, abalones, chitons
o Hard-bottomed sublittoral habitats have complex food webs
71
What do we know about kelp forest habitats?
```
o Dominant in temperate waters
o Rapid growth
o Canopy forming
o Attached by holdfast (up to 40m deep)
o Giant kelp: grow 60 cm/day
```
72
Give an example of A "top down" ecological interaction from the change in behaviour in killer whales.
Shift in killer whale behaviour resulted in declining sea otter numbers. This resulted in an explosion ins sea urchin numbers which overgrazed the kelp (decrease in density)
and Example of sea cow: Was abundant until hunted along the sea otters
Sea otter hunted first which then lead to and increase in sea uchrins í decrease in kelp which led to lack of resources for the sea cows?
73
What do we know about the Deep sea benthos?
o Organic rich, soft-sediment "ooze" dominates (organisms tend to be light and not disturb the sea floor)
o Only 1-3% of primary productivity reaches sea floor
o Very few suspension feeders (slow water movement, scarce food), most filter feeders
o Many more deposit feeders (80%+), eating 'marine snow'
74
What are benthis infauna?
meiofauna (<0.5mm such as nematides and copepods) + macrofauna (>0.5mm such as bivalves and polychaetes)
75
How does Macrofaunal community structure change with depth?
o Sessile species less common
o Scavengers become more common
o e.g. Holothurians, such as the sea pig (Scotoplana globosa)
76
Is there a relation between size of organism and depth?
o Most organisms (infauna, meiofauna) show a reduction in size with increasing depth, reflecting food supply.
o But scavengers show the reverse…
o An adaptation to intermittent food supply?
77
What do we know about sea mounts?
o Seamounts rise >1km above the abyssal sea floor
o Knolls rise 0.2 to 1km above the sea floor.
o Often extinct volcanoes
o ~33,400 seamounts known, ~138,000 knolls
o Typically between 3km and 5km below the sea surface
Tend to be geographically structured (along the mid-Atlantic ridge). In volcanic active areas or underwater volcanoes.
Global distribution of seamounts, often chains (e.g. along fault lines)
o Interact with ocean currents, driving eddies over the seamount
o Can promote upwelling (increased nutrients)
o Provides hard substrate for sessile macrofauna
o A high diversity of benthic and bentho-pelagic species present (shelter and breeding opportunities)
78
What is an eddy?
In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object.
79
Sessile filter-feeding benthos near seamounts, give 2 examples
e.g. deep water coral (Lophilia pertusa): can live for over 200 years (relatively undisturbed habitat)
And widely distributed deep water fish e.g. orange roughy (Hoplostethus atlanticus): Can live ~150 years, mature 20-30 years
80
Are seamounts used by large pelagics? (sharks, billfishes, tuna)
Highest diversity closest to the sea mounts (important to the structural habitat of benthic as well as pelagic organisms)
81
What do we know about hydrothermal vents?
o Found along fault lines (mid ocean ridges)
o Discovered in 1977 (Alvin submersible)
o Diverse and endemic faunas, often huge biomass
Critically, hydrogen sulphide (H2S) is the basis for metabolism of chemoautotrophic bacteria and the food web
Sulphur-oxidising bacteria (e.g Beggiatoa)
2H2S + O2 í 2H20 + 2S (white)
Sulfide used as energy source in Sulphur-oxidising bacteria.
-->First taxon in the food chain
82
Name 3 organisms that live in hydrothermal vents/have Sulphur-oxidising bacteria
Vestimentiferans (polychaete) tube worm
o Riftia pachyptila ~1.5m long
o No digestive tract, depends on symbiotic bacteria in "trophosome" tissue
o Specialised haemoglobin to bind H2S, and to transport it to bacteria
Bathymodiolus thermophylus (vent mussels)
o Dominate vents in Atlantic
o Depend on symbiotic bacteria on gill filaments
o Can filter feed too
o Must live close to sulphides to "feed" bacteria
Heterotrophic polychaete - Alvinella (Pompeii worm)
o Up to 13cm, aggregates, paper-thin tubes
o hairy (cultures of bacteria = insulation?)
o Feeds on filamentous chemoautotrophic bacteria
o Most thermally-tolerant eukaryote (regular >65°C, sometimes >100°C)
83
Name other chemosynthetic based systems (other than hydrothermal vents)
o Lipids in bones create anoxic high sulphide environments (yellow=waste sulfur)
o Sulfur-dioxide using bacteria, with tube worms and mussels living in close
proximity that are cloes relatives to the ones living in the hydrothermal vents
o Mats of sulphur-oxidising bacteria (like vents)
o Specialist vestimentiferans, mussels etc. form food web
o Also "bone feeding" Osedax tube worms
84
What is a Hydrocarbon "cold" seeps?
A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool.
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What is a brine pool (in relation to a cold seep)?
A brine pool is a large area of brine on the ocean basin. These pools are bodies of water that have a salinity three to eight times greater than the surrounding ocean. For deep-sea brine pools, the source of the salt is the dissolution of large salt deposits through salt tectonics. The brine often contains high concentrations of methane, providing energy to chemosynthetic animals that live near the pool. These creatures are often extremophiles.
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"Foodchain"/organisms living in hydrocarbon cold seeps?
o Successional environments (rather transitory)
o Initially bacterial mats, using H2S
o Then Bathymodiolus (with gill bacteria)
o Calcium carbonate produced by bacteria = hard substrate
o Then tubeworms, more mussels, soft corals
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What does the term coral reef describe?
Term describes both
• Biological “coral” community
• Geological “reef” formation
Built from the accumulated skeletons of calcium carbonate (CaCO3) -secreted from animals and plants, inc seaweeds
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Why /how are Tropical surface waters are stratified and nutrient poor?
* Permanent, steep thermocline
* Strong pycnocline (density / salinity gradient)
* Generally low biomass except upwelling regions and coral reefs
* Compare with rates of primary productivity: the amount of carbon coral reefs fix is the highest of any of the pelagic / terrestrial / benthic environments we have been considering.
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what is the most productive ocean or terrestrial area?
500-3750gC/M2/yr for coral reefs + shallow estuaries only on par with swamplands + intensely developed agricultural areas (which aren’t a natural comparison)
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what are Coraline algae? why are they important in the food chain?
Coraline algae: red algae but CaCo3 secreted in the walls which mean they look pink; green algae can also have dense deposits of Caco3 in their walls this means they are harder to consume: defence against predation.
A lot of their material gets broken off + turns into detritus and is indirect support of the food web.
Seastars. + crabs target the corals; grazers target seaweeds (direct)
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what are the two types of corals? give an example of each
A. Ahermatypic = not reef-building. E.g. soft coral. Do not produce a rigid calcareous skeleton. ( more vulnerable to predation) But Can produce sclerites (CaCO3 needles)
B. Hermatypic = reef-building. Produce massive skeletons of CaCO3 (calcium carbonate). Dominant group are Scleractinian coral (“stony corals”). Grow reasonably fast: 25cm in a year
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how can corals surive in acidified environments?
skeleton-producing corals grown in acidified experimental conditions are able to sustain basic life functions, including reproductive ability, in a sea anemone-like form and will resume skeleton building when reintroduced to normal modern marine conditions
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Why are symbionts important to corals?
90% of energy required by tropical coral.
• Cells of algae leaky: so fixed organic material will leak out + then can be consumed by the corals (in turn the algae get nitrates + phosphates + plenty of CO2 so they can photosynthesise)
• Explains distribution of tropical coral in shallow well-lit marine environments that are generally very nutrient poor.
• CO2 and nutrients are continually recycled between a coral polyp and its symbiotic algae.
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Why is it beneficial for dinoflagellates to be symbiont with algae?
• Dinoflagellates are normally free-living but this gives them an advantage: as long as the water is clear, tenticles wave around (Good for gas exchange), plenty of nutrients to absorb because of proximity to coastal margins and don’t need to swim because they are in a matrix where they can move around passively because of the tentacles: they lose their flagella when they’re inside the flagella.
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what are some ways in which corals could live without algae?
1) Prey-capture of zooplankton using stinging cells (cnidocytes – stinging cells in the tentacles of polyps). – not nutritionally useful unless in large quantities.
2) Mesenterial filaments – tubes attached to the wall of the gut that are extruded through the mouth to digest food outside body. (secrete enzymes + anything in the immediate vicinity of that polyp can be consumed) (SLIDE 16)
3) Mucus threads secreted over colony surface to capture passing plankton, then gathered into mouth. (can trap anything going over): ‘Mucus trap’ released into reef water.
a. Acropora sp. can exude up to 4.8 litres/m3
b. Food source for benthic bacteria
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How does the growth rate of cold water corals differ to that of warm water corals? why is this?
* Can get cold water corals (4 or 5 degrees )
* Both colonies >100 years old.
* The skeletal growth rate of tropical coral is much faster than cold water coral due to symbionts. – doubling of metabolic rate with 10 degree rise in temperature
* Calcification is 3 x higher during day, when symbiotic algae are photosynthesising, than at night. (if you’re living in colder environment + not ps as much: won’t grow as much so can’t calcify as much)
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do cold water corals build reefs?
no, they are • Ahermatypic, although can build mounds on top of seamounts ( huge secretions CaCO3 + mud) – this can enable them to get enough light Not restricted by water temperature and light – instead restricted by oxygen and food (Particulate Organic Matter).
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When will corals bleach? why?
• Coral will ‘bleach’ if temperatures reach ~1°C > average seasonal maxima: they will eject all of these endosymbionts. These might grow flagella again / build up dep. on environments
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what are some of the Alternative energy sources for
| bleached coral?
o Lipid reserves
o Night-time mesenterial filament feeding on neighboring algal turfs (dense collections of filaentous alge + the coral secrete enzymes to digest the contents of the turfs growing on the rocks
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what is the Adaptive bleaching hypothesis ?
Adaptive bleaching hypothesis = shuffling the population of symbiotic algae may increase the threshold temperature of bleaching.
(Aclimatisation)
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Why are Crustose coralline algae important?
• Can be responsible for 50% of the hard surface of a reef.
• Why are they important?
o Acts like mortar for the reef by forming an encrusting cement of Mg-rich CaCO3. (bind everything together + contribute overall to structure of the reef)
o Stability + Surface aids the settlement of coral recruits and other reef invertebrates.
o So they can create an environment that is attractive for other animals to establish there.
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What are teh different types of coral reef eroders?
1. bioeruders: internal (borers; microbores; macroborers) + exteral (grazers) e.g. parrot fish
Crown of thorns starfish: Acanthaster planci (have stomach wider than their body: evert their body; spread over corals, secrete loads of enzymes + then take it in --> massive top down control on the coral reef. )
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Wh is overfishing a risk to coral reefs?
• overfishing removes the top predators which will have an impact on planktivorous fish: eventually you are fishing down the food chain.
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What are some adaptations of pelagic macrofauna
buyancy - swim bladders / accesory air sacs /lipids
Locomotion - streamlined
defence - shoaling; camouflage, sensory systems - electrolocation + v. sensitive olfaction, reproduction (spawning migrations)
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What are the migrations of pelagic species?
• Migrations typically for locating food, mates and/or to release eggs and young in in the vicinity of suitable nursery grounds. – most oceanic sp have some kind of migration, bc of the heterogeneity of the environment. – need to find a nursery ground to raise young.
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What has the Northwest passage meant for bowhead whales?
Canada + Iceland + the iceshelves: these are typically pushing right down +over the last few millennia they have been closed: so separated Greenland + Alaskan population. You can see that in 2006, each whale wasn’t able to go to either side; but now it is the northwest passage + used by boats and also whales: the whales are now reunited
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what is an optimal strategy when searching complex prey landscapes?
may be “Levy flight”
• Many small movements, fewer larger movements.
• Using the frequency distributions of movement events it is possible to calculate the Levy exponent – ideally μ = 2.
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how do movements depend on habitat use?
Species moving primarity in open oceans = more ballistic movements (towards 0, don’t tend to go back on themselves + don’t vear off); indivs in coastal are more random, go left / right / back on themselves etc.
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What is depth zones are considered to be the deep pelagic zone?
Bathypelagic – 1000 to 4000 m
Abyssopelagic – 4000 to 6000 m
Hadopelagic – 6000 to 11,000 m
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Where does the deep water come from?
* Deep waters are "formed" where the air temperatures are cold and where the salinity of the surface waters are relatively high. The combinations of salinity and cold temperatures make the water denser and cause it to sink to the bottom.
* Deep waters formed as sea ice freezes in polar regions
* These waters are dense, saline, cold and oxygen rich
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What is the Thermohaline conveyor belt?
There is a large-scale pattern to the way that seawater moves around the world ocean. This pattern is driven by changes in water temperature and salinity that change the density of water. It is known as the Global Ocean Conveyor or thermohaline circulation. It affects water at the ocean surface and all the way to the deep ocean. It moves water around the world --> deep ocean circulation, moves water between the deep and surface ocean worldwide.
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What are the Temperature profiles deep sea?
* Deep sea typically stable
| * Strong temperature and density gradient in the mesopelagic zone
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What is an Oxygen Minimum Zones (OMZ)?
Oxygen Minimum Zones (OMZ) are the places in the world ocean where oxygen saturation in the water column is at its lowest. This zone typically occurs at depths of about 200 to 1,000 meters
--> Organic decomposition depletes O2
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What is does Allochthonous mean?
In limnology, allochthonous sources of carbon or nutrients come from outside the aquatic system (such as plant and soil material).
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How do fish deal with the pressure in the deep sea +Give an example ?
* Sebastes rockfish have “closed” swim bladders
* Liquid swim bladder --> Liquids compress too, but a lot less.
* Barophilic “pressure loving” animals have pressure resistance proteins proteins (evolved to be more efficient under pressure e.g. fish muscles, using pressure-resistant 3D structures).
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Why do deep water species have broader ranges
because of homogeneity of deep waters (broad adaptations)
| but Species groups differ in depth occupancy
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What is a photophore?
A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods (a light-producing organ in certain fishes and other animals). The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors.
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What is a photophore used for in deep sea animals?
The character of photophores is important in the identification of deep sea fishes. Photophores on fish are used for attracting food or for camouflage from predators by counter-illumination.
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How is bioluminescence produced in deep sea animals?
The bioluminescence can variously be produced from compounds during the digestion of prey, from specialized mitochondrial cells in the organism, called photocytes ("light producing" cells), or, similarly, associated with symbiotic bacteria in the organism that is cultured.
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What are photophores used for in deep sea animals?
The character of photophores is important in the identification of deep sea fishes. Photophores on fish are used for attracting food or for camouflage from predators by counter-illumination.
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How have deep pelagic and benthic species evolved in regard to 'food collection'?
* Specialised for low energy lifestyle
* Density reduction of all tissues (low bone density)
* Most “benthopelagic” so use both habitats
* Active scavenging
* Brain olfactory regions highly developed
* Some sit-and-wait predators (e.g. tripod fish)
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Name 5 deep sea adaptations
1) Vertical migrations (Follow the zooplankton up and down) --> major way of food entering into mesopelagic zone = source of the marine snow
2) Camouflage
3) Bioluminescence
4) Vision
5) Trophic morphology (teeth, jaws)
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How do animals use camouflage in the mesopelagic vs the deep pelagic
Camouflage (mesopelagic)
* Transparent
* Red is a common colour (no red light, so actually they appear dark)
Camouflage (deep pelagic)
* Often just black (contrasts with bioluminescence, important because it’s the only light available).
* Transparency is common (but hard to achieve)
* Body structure and chemicals need to be transparent
* Refractive index of tissue needs to match water
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What uses does bioluminescence have for deep pelagic animals?
Bioluminescence (camouflage)
* Most mesopelagic animals are bioluminescent
* Ventral bioluminescence hides silhouette from below
* Most photophores are on the belly to camouflage against predators.
* Mesopelagic shrimp match light output to ambient light shadow is broken up and if body colour matches as well, then good camouflage (see figure).
Bioluminescence (other uses)
• Startle predators
• Escape from predators (luminescent ink)
• Lures (e.g. anglerfish, dragonfish)
• Species recognition, intraspecific communication (even sexual selection?)
o Species-specific photophores
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How has vision evolved in deep pelagic animals?
* Evolved big eyes to capture as much light as possible
* Mesopelagic species, visual capabilities often very specialised (bioluminescence and residual ambient light)
* “Deep pelagic” species visual capabilities poor (only bioluminescence)
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How has vision evolved in mesopelagic animals?
* Mesopelagic viperfish
* Some species have “tube eyes” e.g. barreleyes (Opisthoproctidae): These fish are named because of their barrel-shaped, tubular eyes, which are generally directed upwards to detect the silhouettes of available prey; however, according to Robison and Reisenbichler, these fish are capable of directing their eyes forward, as well.
* One species, two functional eyes (refractive and reflective optics)
* Spookfish: each eye is split into two connected parts, so the animal looks like it actually has four. One half points upwards and gives the spookfish a view of the ocean above. The other points downwards into the abyss below and it’s this half that makes the spookfish unique. The eyes of all other back-boned animals use a lens to divert the path of incoming light and focus it onto a specific point of the retina. But the spookfish’s downward-facing eye uses mirrors instead, forgoing a lens in favour of hundreds of tiny crystals that collect and focus light.
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What is the Pace and Pattern of Change in temperature of oceans?
Ocean temps rising by 0.1°C per decade (1960-2009) – not spatially consistent: relatively little in southern ocean compared to places like the North Sea.
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what is the cascade of CC on oceans?
- Individual organisms: more or less fit: changes in body size, repro, primary production, habitats
- Population level: changes in pop growth, abundance + species distribution
- Community / ecosystem: changes in community structure, trophic interactions, biodiversity
- Fisheries economics: changes in fisheries catch, economics of fishing, fisheries management
- Global issues: human pop growth, migration, development, global food supply + energy price (Some countries have high dep on marine fisheries so if these change they might move)
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What sort of Biogeographic shifts have copepods + zooplankton shown?
- Warm temp sp have gone more north
- Temperature sp have also moved north
- Subartic sp have virtually disappeared from survey area.
- See this because they have many generations per year so can move.
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Wy may fish show lower poleward distributions shifts than expected – they may be constrained by “essential” habitat?
Fish have slow life histories + dependent on habitat: needs food supply + nursery grounds: if doesn’t have this, it won’t shift north + will stay where it is (+ potentially suffer).
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Why will warming seas result in changes to body size?
Warming seas are energetically expensive bc contain less oxygen + obtaining oxygen is an expensive thing to do. At warmer temperatures, due to greater metabolic costs we expect smaller maximum body sizes
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Why will CC result in changes in phenology?
* Phenology is the study of the timing life history events
* Climate determines the timing of seasonal marine events: zooplankton appearcenes, algal blooms, breeding of bony fish
* Most species studied show earlier phenology latitudinal shifts
* Strong evidence that warmer waters = earlier plankton blooms
* Edwards et al 2004: Nature
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How is CC + cod related to the abundance of copepods?
North Sea cod recruitment has been linked to changes in the structure the zooplankton community driven by climatic variability
• In the good years, Calanus finmarchicus were present
• In the bad years, Calanus helgolandicus was present, but late by 4 months: cod had nothing to eat and so pop collapsed and this is prob a main reason (As well as fisheries) that the North sea cod are now relatively rare).
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What is the Match-mismatch hypothesis?
Mismatch between prey and critical stages in their life history is known as the match-mismatch hypothesis (developed by David Cushing)
