Biological Oceanography Midterm #2

grazers

microbial consumers of microbes, small = nanoflagellates, large = ciliates

in oligotrophic (low nutrients) ocean how much of BP do grazers consume

nearly all

in coastal ocean do bacteria or grazers outpace one another

bacteria outpace their grazers

viruses

non-living genetic elements; infect every known lifeform, including bacteria, archaea, and phytoplankton

if phytoplankton eaten where does carbon and energy go

to higher trophic levels (ex. krill than fish)

if phytoplankton get lysed by virus where does carbon and energy go

becomes DOM, which bacteria eat, that are eaten by phytoplankton (ex. ciliates)

viral shunt

resulting ecological process of viral lysis, release cellular contents of bacteria and phytoplankton into microbial loop, recycling nutrients

small single-celled zooplankton grazers

nanonflagellates

holoplankton

animals that spend their entire lives as plankton

meroplankton

animals whose larvae are planktonic but whose adult forms are either nekton or benthic

techniques to sample zooplankton

plankton nets (major; fragile zooplankton may beed to collected by divers or subs/ROVs), dna sequencing

Herbivorous or omnivorous zooplankton

copepods, krill, salps, larvaceans, pteropods

carnivorous zooplankton

arrow worms, jellyfish, comb jellies

scan and trap feeders

copepods and krill

sieve and flux feeders

salps, larvaceans, pteropods

info about copepods

small, 0.5-0.15mm, make feeding current with feeding appendages, channeling into mouth

info about krill

larger, 1-5+cm collect food particles with thoracic legs that make a filter basket, molt back to juvenile size and lose sexual characteristics to survive winter

info about salps

large, up to 10cm long, barrel-shaped body with mucous sieve in the middle, pulls water through the barrel as they swim and pull food into their mouth with cilia, solitary and aggregate forms (female kill salps lay eggs in hollowed body and propel body around to feed larvae)

info about larvaceans

small, only a few mm to cm long, build gelatinous house up to a meter across, pulls water through house to filter and trap particles to eat, abandons house if gets clogged

info about pteropods

look like sea snails, called sea butterflies, small, shell usually < 1cm, makes mucous web that draws in when food captured to ingest

info about arrow worms (chaetognaths)

larger, a few mm to 4 cm long, grasp prey in hooks around their jaws, some inject a toxin they harvest from bacteria

info about jellyfish (medusae)

large, a few mm to 60m tentacles, capture prey with stinging gelatinous zooplankton

info about comb jellies (ctenophores)

large, 1-10ish cm long, egg or barrel-shaped gelatinous zooplankton, prey stick directly to the body or to trailing tentacles of ciliated lobes

challenges zooplankton face in acquiring food in the ocean

food is dilute, rare, and small, pelagic environment is patchy

pros and cons to scan and trap feeders

grasp and handle food, tend to be smaller, clear a volume of water of food much slower, more selective and specialists, larger particles >5um

pros and cons to sieve and flux feeders

collect food with mucous sieves, tend to be larger, clear a volume of water of food faster, non-selective generalists, particles from 0.1-100um

info about natural zooplankton blooms

jellyfish and comb jellies can both reproduce rapidly and build up to bloom-level concentrations under ideal circumstances, occuring on multi-year cycles (5-20years)

anthropogenic structure affecting gelatinous zooplankton blooms

boat docks, ship hulls, oil platforms

how anthropogenic nutrients affect gelatinous zooplankton blooms

more nutrients, more small plankton (not a lot of diatoms (silica)), meaning more food for jellies

other anthropogenic modifications affecting gelatinous zooplankton blooms

overfishing jellyfish competitors and predators, ships can move invasive species in ballast water, climate change and warmer waters

zooplankton mortality

essentially all zooplankton get eaten

zooplankton adaptations to not get eaten

nearly transparent, dart quickly to avoid predation, mucous feeders to release, large schools to confuse visual predators, diel vertical migration

general pattern of diel vertical migration

move up towards the surface at night, down into the deeper water during the day

hypotheses to explain diel vertical migration

predator avoidance, patch selection (moving with ocean current to better feeding ground), metabolic (increase fecundity = ability to produce offspring)

how does diel vertical migration impact the ecosystem

benefits primary producers as they experience less predation, moves carbon and nutrients around and into depths (most digesting and excretion/feces production in deep waters)

DIC

dissolve inorganic carbon, main carbon form in ocean, mostly bicarbonate, HCO₃-, dissolved CO₂

DOC

dissolved organic carbon like molecules like sugars and proteins that are no longer part of a biomass particle but did originate from an organism at one point

POC

particulate organic carbon, biomass that is living or dead, in particle form

PIC

particulate inorganic carbon, calcium carbonate skeletons, no one wants to eat

what drives the solubility pump and what form of carbon does it move

deep water formation (ocean temperature, solubility of CO₂ in seawater, and the thermohaline circulation) drives it, bringing DIC down to the deep ocean

biological pump

more food web processes, remineralization, photosynthesis and respiration, coupled with sinking

what is marine snow

non-living organic particles that are visible to the naked eye (> 0.5mm) and slowly sink through the wayer

what is marine snow made of

dead organisms (mostly plankton), fecal pellets from zooplankton, mucous webs and traps from pteropods, larvaceans, etc., secretions from organisms

how do particle size and composition relate to sinking speed

larger particles sink faster, density, ballasting = increased density from heavy components

sediment traps

a collecting device that you leave out for days to a year and let stuff fall in, short term = simpler tubes, long term = multiple bottles that rotate under the funnel one per month/week/etc.

polyacrylamide gel traps usage

preserve sinking particles for visual examination

in martin curve POC drops off over depth because of what

the particles being consumed, respired, and slower sinking speeds from repackaging

how does particle flux relate to surface primary production

when more surface primary production, generally more particle flux, export ratio = export divided by NPP

why is it important that zooplankton move carbon to depth so quickly (DVM)

prevents carbon from being recycled in the surface waters and ensures its sequestration in the deep ocean

mixing/advection is with what forms of carbon

focused on mixing DOC and some POC from the surface to the deep ocean

seasonal patter of DOC accumulation by mixing

DOC distribution follow ocean circulation, DOC concentrations are higher in surface and lower at depth, accumulate because majority of molecules aren’t tasty, seasonal deep mixing results in DOC export by homogenization

what is the carbonate pump

the sinking out of (PIC) calcium carbonate skeletons (mainly coccolithophores) that no one wants to eat so it sinks rapidly until reaching the carbonate compensation depth; extension of biological pump, but no consumption at depth

carbonate or calcareous ooze

sediments made of calcium carbonate skeletal material; forms within sediments, sequestering it

carbonate (or calcite) compensation depth

depth at which the rate of calcium carbonate dissolution (starts to break into component ions) equals the rate of supply from above; calcareous ooze can build up above CCD; calcium carbonate insoluble at surface

what affects the carbonate compensation depth (CCD)

temperature (more soluble at low temp), pressure (more soluble at high), CO₂ concentration (more soluble at high conc.); more CO₂ in atmosphere less CaCO₃ storage in sediments

what is microbial carbon pump

as bacteria eat DOC, it becomes increasingly less appealing, leading to a pool of unappealing organic compounds, because no one wants to eat its sequestered

recalcitrant DOC

DOC that’s been processed to the point where most/all of the valuable parts have been cleaved off and consumed

e-ratio

the fraction of NPP that is exported from euphotic zone; way to quantify the efficiency of the biological pump (0-0.4)

regenerated nitrogen

recycled nitrogen within the euphotic zone

examples of regenerated nitrogen

zooplankton excreting urea and byproducts like amino acids, phytoplankton taking up ammonium to build biomass (returned back into inorganic form)

new nitrogen

nitrogen that originates outside the euphotic zone

examples of new nitrogen

upwelling of deep-water NO₃, N₂ fixation, a little bit from rivers and coastal runoff

new production

primary production (in terms of carbon) that results from new nitrogen

regenerated production

primary production that results from regenerated nitrogen

why is new production important from an ecosystem perspective

important because it is the base of the food web, drives carbon cycle that provides energy and organic matter for the entire ecosystem

f-ratio

new production (NO₃ uptake) / new + regenerated production (NO₃ + NH₄ uptake); high in upwelling zones, low in the oligotrophic ocean

remineralization length scale

just depends on how fast particle is sinking to avoid getting eaten

where does new production occur

areas of upwelling, where there is lots of nutrients

where does regenerated production occur

oligotrophic gyres, area where there is low nutrients

how do consumers maintain regenerated nutrient supplies

microbes recycle nutrients (microbial loop), zooplankton too, whale pump (surface feeders —> regenerated nitrogen; deep feeders —> new nitrogen)

remineralization length scale

depth to which a particle sinks before it’s remineralized

short remineralization scale where

in gyres with low new production, small cells, sink slowly, consumed at shallow depths

long remineralization scale where

where new production is high, large particles, so sink faster and make it to greater depths before being eaten

why is nitrogen fixation important in increasing ocean carbon export

nitrogen fixation breaks redfield ratio, with more nitrogen, in order to return back to steady state ocean under redfield, more carbon is brought down to the deep ocean (upwelled waters bring DIC to surface with NO₃)

why target iron and HNLCs

iron is limiting nutrient in HNLC, increasing iron, microbes can flourish (bloom), increasing primary production, especially large cells, increasing export potential

downfalls to iron in HNLCs

the export from bloom is not predictable, bloom can not go on forever, even if carbon is exported the depth at which its remineralized is unknown, and if sequestered only a 1000 year solution because DIC comes back up with upwelling

other approaches to increase rate of biological carbon pump

restoring coastal ecosystems, farming seaweed, creating artificial upwelling to increase primary production (wave-powered pumps), add rocks to ocean to adjust pH and let it take up more CO₂

three main groups of nekton

chordates, molluscs, arthropods

universal challenges faced by nekton

food is dispersed, mates are dispersed, predation because no where to hide

shared traits by nekton in response to universal challenges

colors (red and black) that aren’t visible in blue light, silver sides the reflect light and obscure silhouettes, countershading

approaches to identify who eats whom in deep open ocean

gut content analysis, stable isotope analysis

goal of fisheries oceanography

estimating a catch level that maintains a sufficient spawning population; hard because multiple breeding grounds and fish can converge on feeding grounds for part of the year (removing one species alters the predators and prey of other species)

potential uses of eDNA sampling

routine community composition monitoring, targeted monitoring, ecological questions like studying food webs

specific targeted monitoring from eDNA

endangered species, invasive species, cryptic species, harmful algal blooms

biological material that gets sampled for eDNA

feces, mucous, gametes, skin, hair, carcasses

challenges of implementing eDNA monitoring

dna has a limited lifespan, in dna processing there are different target genes and primers for those genes, reference database, hard to interpret with spawning seasons, organisms vary in size, dna of different species degrades faster or slower

direct development

young come out of the egg looking a lot like adults and develop quickly; no distinct larval stage

lecithotrophic larvae

larvae are provided with a form of nutrition like a yolk sac

planktorophic larvae

larvae who feed on other members of the plankton

feeding differences of lecithotrophic and planktotrophic larvae

lecithotrophic are provided with food and planktotrophic feed on other members of plankton (aren’t provided)

morphological differences between lecithotrophic and planktotrophic larvae

lecithotrophic are relatively large and produce smaller numbers, while planktotrophic have more complex body forms because need to feed themselves

time in larval stage (lecithotrophic and planktotrophic larvae)

lecithotrophic only stay in larval stage until nutrition lasts (hours to 2 weeks) and planktotrophic have longest potential persistence in larval stage (weeks up to a year) 

parental investment (lecithotrophic and planktotrophic larvae)

lecithotrophic produce in small numbers with great parental investment, while planktotrophic produce in large numbers with low parental investment

benefits of a larval life stage

for P reduced competition between parent and offsping, for sessile and benthic organisms dispersal to new habitats (L close to birth habitat (consistent year-to-year), P can be moved away by currents (high risk, high reward potential; interannual variability), escape from parasite or benthic predators

how to study larval dispersal

modeling combining spawning locations, larval duration, and modeled ocean currents; population genetics