Final Exam: Productivity, Larvae, Marine Ecological Processes, Estuaries

microbial loop process

• phytoplankton die w/o being eaten → break down into dissolved org matter → eaten by bacteria

• → bacteria incorp into standard food chain if eaten by zooplankton who are eaten by something bigger

• → or bacteria cycled back into microbial loop if eaten by zooplankton who aren’t eaten + return to DOM pool

microbial loop

• marine version of detrital food chain

• can add productivity to marine food chain by inclusion of outside detritus

• as much as ½ primary production channeled thru it

seasonal productivity: salt marsh grasses

• grasses have seasonal growth + dieback pds depending on location

• dead grasses (wrack) stay rooted + rot where they are

• stored nutrients from summer in underground rhizomes + turnover of wrack nutrients → large growth each spring

seasonal productivity: phytoplankton in tropics

• oligotrophic (low nutrients)

• no seasonal bloom

• year-round sunlight

• always nutrient limited

seasonal productivity: phytoplankton in polar regions

• bloom in summer when no light limitations

• recedes in winter + fall due to onset of shorter days

seasonal productivity: phytoplankton in temperate regions (spring)

• larger spring bloom

• not light limited

• thermocline forms, concentrating phytoplankton to surface waters, don’t get circulated to below comp depth daily

• bloom dies due to nutrient limits from surface water depletion, no upwelling

seasonal productivity: phytoplankton in temperate regions (fall)

• smaller fall bloom

• fall storms kick up sedients + release nutrients by breaking thermocline + allowing mixing of deep water

• bloom dies bc of light limitations + circulation of phytoplankton below comp depth

seasonal productivity: phytoplankton in temperate regions (summer + winter)

• summer: no light limit but no nutrients left from spring, + added stratification

• winter: light limit, but despite no thermocline, there is no bloom

geotaxis

• to know whether to move up or down by sensing earth’s gravity

• positive = w/gravity (down)

• negative = vice versa

phototaxis

• sensitivity to light

• positive = towards light (up)

• negative = vice versa

barotaxis

• hydrostatic pressure

• increases w/incoming tides bc water depth increases → more pressure

role of adults

• time, season, location, tide, depth of spawning + release of eggs, + buoyancy of eggs

• → determine transport for first few days of development before larvae are big enough to act on their own

selective tidal stream transport (STST)

relies on combo of larval behavior + oceanographic processes to transport larvae much farther than they could swim on their own

factors of selective tidal stream transport (STST)

• oceanographic processes

• tides: ebb, flood, slack water, zero net movement up/down estuary

• vertical estuarine strat

• boundary layer effect

old settlement model

• random larval settlement

• site-specific mortality determines final distribution

new settlement model

active habitat selection based on larval behavior + settlement cues

new model: larval behavior

• free-swimming larvae alternate photonegative + photopositive to test bottom (crawling, turning, flexing abdomen) for suitable cues

• leave if surface is clean (uncolonized) or crowded

new model: settlement cues

• chem/microfloral cues indicating suitable habitat

• presence of conspecifics

• pits + grooves

• avoidance of competition

• bottom type: solid vs mud vs sand

passive deposition (microhydrodynamics)

larvae deposited on bottom as a function of their fall velocities, behavior, + bottom flow patterns

passive deposition: deposition

• can determine where + when active habitat selection can take place

• larvae transported by velocities above their swimming speeds deposited in bottom in areas of low flow, where their swimming + habitat selection behavior is effective

passive deposition: structure

• any structure on bottom can create passive deposition of larvae bc currents + flow patterns are changed as they move around the structure

• cyclical movement in vortexes around structure → increases sedimentation + passive deposition

interaction of flow + chem cues

• flow can determine when a larvae has an opp to respond to a chem cue + when they don’t

• still water: each chem cue can attract larvae

• moving water: only the cues in low-flow/deposition areas can attract larvae

bottom-up regulation

community structure shaped by nutrient availability + consequent primary production

bottom-up regulation: seasonal photosynthetic blooms

• blooms create seasonal oscillations in abundance of orgs at higher trophic levels

• species + pops up the food chain rise one at a time one after the other, but with 10% less energy each time

bottom-up regulation: nutrient availability

increased nutrients → increased secondary production → increasing reproduction

top-down regulation

• control of diversity + abundance in a community based on presence of consumers

• direct effects of consumers limit success of orgs at lower trophic levels (ecological + evolutional)

ecological effects of top-down regulation

• death: decreases prey pop size + less prey left to reproduce

• limiting prey to refuges

• indirect effects

ecological effects of top-down regulation: limiting prey to refuges

generally physiologically stressful places → more energy spent to survive → less energy left for reproduction → decreases pop size

top-down control: evolutionary time

• consumers act as selective force for evolution of anti-predator defenses that promote coexistence of predator + prey

• but metabolically expensive to make defenses

indirect effects of top-down control

• effects other than spatial restriction of prey

• trophic cascades

• habitat modification

indirect effects of top-down control: trophic cascades

• consumers limit their prey

• releases lower trophic levels from predation

• increases pop size of lower trophic levels

• killifish - grass shrimp - anemone

• gulls - urchins - algae

indirect effects of top-down control: habitat modification

• modification of habitat by 1 consumer that trickles down to affect every other species that requires that habitat

• urchins eat kelp, removing habitat species need for protection + primary production

zonation: physical stress

• induced by env factors

• terrestrial orgs: increased w/decreased elevation (towards water) bc increased salt, lower o2, lack of air, waterlogged sediment

• marine orgs: increased w/increased elevation (towards shore) bc dessication, lack of water for respiration, thermal stress

zonation: biotic stress

• competition, predation increase as physical strength decreases

• terrestrial orgs: increases w/elevation (out of water)

• marine: increases w/decreased elevation (into water)

positive interactions: facilitation

• factor increasing success of a diff species → often leads to replacement of facilitator by species they helped

• any action an org does that increases amt of env that meets niche requirements of another species

positive interactions: the facilitator

orgs that positively effect a neighboring org (measured by individual physio benefit or pop level effects

habitat amelioration

• an org changes an abiotic factor that unintentionally helps a member of the same species/another species by making env less harsh for them

• can allow for extension of range in stressful territory (can be facilitation)

• ex low soil o2 counteracted by marsh grasses/mangroves oxygenating soil

habitat amelioration: physical stress + variation in neighbor interaction w/stress

• amelioration more important the more stressful a habitat is

• high stress levels = positive interactions

• low stress levels = negative interaction (competition)

associational defenses

• response to biotic stress (predation)

• multiple species groupings (opportunistic or mutualistic, palatable orgs hiding among noxious prey)

• tradeoff for loss of space/ideal conditions, increased competition

importance of habitat amelioration vs associational defenses

• increasing physical stress + low consumer pressure = habitat amelioration more important

• increasing consumer pressure + low env stress = assoc defense more important

ecosystem engineers

• org that creates, significantly modifies, maintains, or destroys a habitat

• also alters availability of env resources (light, nutrients, water flow, etc) for other species

estuary

semi-enclosed body of water in which fresh + saltwater mix

bar-built estuary

• sandbars + barrier islands act as barrier btwn ocean + rivers behind the islands

• ex: Pamlico Sound

fjord estuary

• glacially carved U-shaped valley on coastline from mtns → sea

• valleys flood at sea level rise

• ex: coastal New Zealand

tectonic estuary

• piece of land sinks, allows sea to flood area rather than sea level rising

• ex: San Francisco Bay

coastal plain/drowned river valley estuary

• sea invades river valleys + lowlands as sea level rises

• ex: Chesapeake Bay