Term 1 2023 Questions Flashcards
why is the new lithosphere isostatically most buoyant
there’s a direct relationship between depth + age (so newest is lightest)
what subsections are marine biology subdivided into
functional biology, ecology and biodiversity
what were the earliest life forms
methane-producing Archea, 4.5 bn years ago
what’s an example of a divergent plate margin
Mid-Atlantic Ridge
what is an example of a convergent plate margin
Mariana Trench or NW Pacific
How do tectonics help reefs develop
through isostasy (gravity+buoyancy act on outers crust)
what features occupies the majority of the ocean floor
continental slope and ocean ridges (33%)
How much of earth is water
97%
What are the main properties of water
its a solvent, it has high covalent (allows things to stick), high thermal inertia (latent heat capacity), high viscosity (requires morphology that increases laminar flow)
What are the 2 properties that determine the physical (+chemical) ocean’s structure
Temperature and salinity (+depth+pressure)
how does ocean depth temperature profiles vary
spatially, temporally and with depth
what factors influence an ocean’s depth temperature profiles
seasonality, sunlight intensity, temperature
what are the 3 distinct zones of the ocean’s temperature
surface zone (mixed 25-500m), thermocline (200-1000m) and deep zone (>1000m)
how is the pycnocline (based on density) made
with the thermocline (temperature) and the halo cline (salinity)
what makes the ocean stratified
the temperature determining the density of the water, splitting it into layers that don’t mix often
why does the mixed layer deepen in winter
due to wind mixing (remove pycnocline)
what are the 3 important nutrients for phytoplankton
nitrogen, phosphorus, silicon
what is the global salinity for seawater
34.7% or 34.7ppm
why is salinity more important in colder areas
salt is key for deep waters and drives circulation
what are the properties of salt
non potable, highly corrosive, harmful to many terrestrial plants
why are the subtropics salty
they’re warmer so there’s more evaporation
why are equatorial waters fresher
more precipitation and stronger hydrometeorlogical cycles
why are the poles fresher
less evaporation, glacial melt and very cold so dense salt sinks
why is the Atlantic salty
the continents shapes limit circulation and lots of mineral deposits from rivers
what are the effects of water when salinity is increased
density increases, boiling point increases and freezing point is lowered
how is salinity measured in the ocean
directly: Niskin bottle samples indirectly: CTD (electronic sensors)
what store has the longest residency times in the global water cycle
the ocean - ~3,000yrs
how are ocean currents driven
by wind currents (surface) or global overturning circulation (density-driven), Coriolis force
What is the only gyre that circumvents the whole earth
Antarctic Circumpolar Current
What current carries warm water to the UK
Gulf Stream
what type of flow is caused in cyclonic wind (low pressure)
divergent flow causing upwelling due to surface divergence
what type of flow is caused in anticyclonic wind (high pressure)
convergent flow causing downwelling due to surface convergence
what is the features of the Pacific Ocean circulation
2 subtropical gyres with dominant equatorial countercurrents
what are the 2 categories to organise pelagic organisms
nekton and plankton
what are the types of phytoplankton
diatoms, dinoflaggelates, coccolithophorids, cyanobacteria
what are the types of zooplankton
viruses + bacteria (pico), ciliatiates, dinoflagellates + metazoan larvae (micro), copepods (meso), and gelatinous (macro)
what are the pelagic reigns of the ocean
epipelagic, mesopelagic, bathypelagic, abyssal pelagic, hadalpelagic
what are the benthic regions of the ocean
littoral, sublittoral, bathyal, abyssal, hadal
how is the pelagic realm defined
based on depth and proximity to land
what is plankton defined by
size and broad ecological role
why do marine systems only have 4/5 levels
inefficient eating (>70% lost as heat), long food chains are unstable, predator design is limited, omnivory popular
what is a good predictor of trophic level in marine organisms
body size (energetic demands increase with size) +PP are very small and numerous
why are marine food webs more complex
low levels of specialism (omnivores), opens of system, large sizes changes along life history, long lifespans (ontogenetic shifts)
what was evidence of top-down control
Overfishing of cod in N.Atlantic, increase in crustacea
evidence of trophic cascades
removal of sea otters= increased sea urchins and kelp decreased
example of mesopredator release
removal of cape fur seals led to large predatory fish dominance, depleting stocks
why does carbon form the backbone of life on earth
has intermediate electronegativity (can form several covalence bonds), it’s less reactive and has 4 valence electrons (form rings + chains)
what is the Redfield ration
106:16:1 (C:N:P)
how do nutrients cycle
remobilising: currents, upwellings, upwards migration of organisms. Sinking and dead o C: marine snow, waste and dead organisms
what do seafloor carbon stocks do
cycle, bury and redistribute nutrients eg. photosysnthesis, trapping sediment
what are human-influenced disruptions to marine nutrient cycles
ocean acidification, hypoxia (Gulf of Mexico dead zone), SST temps increasing
are the root adaptations for mangroves
shallow roots, aerial roots, elongation (<9mm/day), aerenchyma, branching, pneumatophore, roots have negative hyrdostatic pressure
where are mangroves distributed
20C isotherms of sea temp
why are mangroves so important
create coastline stability, nursery grounds + provide source of PP
how much of seagrass biomass is underground
20-60%
why are seagrasses important
reduce turbidity, trap suspended sediments (increasing photosynthetic pot. + carbon sequestration
what are the adaptations of seagrasses due to lower light
have a thin, porous cuticle to absorb CO2 , large gas lacunae, single layer chloroplasts in epidermis, grow >20m generally
ow much carbon burial is seagrass responsible for
10-12% (~0.2% coverage)
what is the seagrass ecosystem threatened by
fungal wasting disease, physical damage, coastal development + reduced water quality
what challenges must seagrass overcome
submergence, CO2 limitations and O2 limitations in sediments
what are the subdivisions of the rocky shore
supra littoral, eulittoral and sublittoral
why is the rocky shore important
high species diversity and habitat complexity, + lots of interspecific competitions
what was a test for interspecific competitions
removal of Balanus that then favorured Chthamalus growth
what are the gradients of the rocky shore
wet-dryness, wave action, particle size + salinity
what conditions allow organisms to live in the upper limit (high intertidal) in the rocky shore
its mobile, has a shell and has high metabolic rates
what pressures influence the lower limit (low intertidal) in the rocky shore
competition and predation