Marine Ecology Exam 2

Phytoplankton and small zooplankton distributions are often determined by localized wind patterns and a balance between ______ ______ and _____ ______

population growth; dispersive processes

List at least two factors that influence the vertical position of plankton in the ocean and choose one that sinks to the seafloor at a slowest rate among: fish eggs, Salps, Radiolaria, and living phytoplankton

Factors that influence the vertical position of plankton in the ocean: Density of plankton, Shape of plankton, Swimming ability, Water turbulence

Slowest sinking: Living phytoplankton

Many zooplankton rise to the surface from deep depths during ________ time of the day. Briefly explain two most probable causes of diel vertical migration of zooplankton

Night (they move toward the surface at night); Two probable causes of diel vertical migration of zooplankton are the effects of predation (easier to avoid being seen by predators in the dark) and the potential energy savings of poikilotherms by diving to cooler waters (dive to cooler waters during the day, cooler temp means slower metabolic rate)

Large geographic scale movement of nekton and seabirds in the ocean are selected to maximize efficient use of habitats for ______ and _______

feeding; breeding

In a temperate-boreal inshore water, phytoplankton bloom occurs in the springtime when available ________ is near maximum and nutrients (nitrate, phosphate) at surface are still very high. The spring time phytoplankton bloom would rapidly decline as ________ level decreases by phytoplankton uptake and increase of __________.

Sunlight; Nutrient; Zooplankton (grazing)

A depth where the amount of oxygen produced by a phytoplankton cell in photosynthesis and oxygen consumed in respiration become equal is called _______ depth

compensation

As light intensity increases, photosynthetic rate _______ in general until it reaches a plateau. Beyond that level of light intensity, photosynthesis is _______. Difference between gross photosynthesis and net photosynthesis is _________.

increases; inhibited; respiration

Inshore phytoplankton live at ________ nutrient concentrations and would be expected to be able to take up nutrients at _______ nutrient concentrations in the environment relative to open-ocean phytoplankton

higher; higher

________ are important in decomposition of particulate organic matter, and they are ubiquitous and usually filamentous groupings of cells. They are a major source of damage and occasionally disease to marsh grasses and sea grasses

fungi

List 3 main body structures of (brown) seaweeds

Holdfast, stipe, blade

How do seaweeds living in deeper depths adapt to a changing light environment? Briefly describe two ways of adjustment

Seaweeds living in deeper depths adapt to a changing light environment by altering their total pigment concentration and by altering their pigment proportions; For example, deeper-dwelling seaweeds increase their total pigment concentration to better capture light (because the deep has less total light irradiance); Deeper-dwelling seaweeds can also alter the proportions of different light harvesting pigments to adapt to the spectral composition of light as it changes with depth in order to maximize the capture of light

How seagrasses reproduce both sexually and asexually?

Seagrasses reproduce sexually via their flowers: pollen is elongate and specialized to stick to its target, so it floats in the water until it reaches a receptive stigma; Seagrasses also extend their populations by asexual growth via a subsurface rhizome system; A rhizome system is a series of interconnected stems that connects shoots beneath the sediment surface and allows for the sharing of nutrients

languir circulation converges on...

surface

circulation around an island creates...

a wake behind the island that traps plankton

tidal current exiting a constriction at the mouth of an estuary causes plankton to...

get trapped or be exported out into the coast (vortices are formed)

plankton occur in_____, sometimes concentrated at interfaces between water bodies

spatially discontinuous patches

what are causes of plankton patchiness?

horizontal spatial changes in physical and chemical conditions; specific depth gradients in salinity and temp; water turbulence and current transport; grazing; localized reproductive behavior; aggregating feeding behavior

phytoplankton density is determined by the interaction between _______ and ___________ (wind and turbulence)

population growth; dispersive processes

low turbulence allows phytoplankton populations too...

increase in an one place

high turbulence _______ phytoplankton and density does not increase

disperses

the W clockwise Gulf Stream eddy causes...

downwelling (pushes isotherms deeper)

the C counter-clockwise Gulf Stream eddy causes...

upwelling (doming up isotherms)

cold eddies can be _______ and move into warmer regions, bringing with them nutrients and plankton

pinched off

cold water regions tend to be...

nutrient abundant

subtropical latitudes tend to have...

low plankton levels

a warm core tends to be ________ while the cold region tends to be _______

nutrient depleted; nutrient rich

chlorophyll is higher in what area?

closer to land (along the coast)

advection

stretches plankton patches out into long filaments that resist dispersal

diurnal vertical movement of zooplankton

some organisms migrate up to the surface at night then down to the depths during the day

diurnal vertical movement behavior is controlled by _________ that is reinforced by ___________

a biological clock; environmental light cues

diurnal vertical movement is common in what seasons?

spring and early summer

the _______ oftentimes follow diurnal vertical movement organisms

predators

predation hypothesis of diurnal vertical movement

predators use vision to capture prey, so zooplankton leave surface waters during the day to avoid being seen. they then return to the surface at night to feed on the phytoplankton unseen

energy conservation hypothesis of diurnal vertical movement

Zooplankton are poikilotherms, so metabolism decreases and energy is conserved in cooler waters; Energetically advantageous to spend the day in cooler, deeper water where metabolic rate and energy needs are low. Come up at night to feed

what are the flaws in the logic of the energy conservation hypothesis of diurnal vertical movement?

the energy cost of vertical migration is modest; migrations have been seen in waters with no thermocline

what would happen to diurnal vertical migration organisms in a solar eclipse?

When it becomes dark during the day, the zooplankton migrate to the surface and then go back down to the depths when the sun returns

what is the buzzing sound associated with diurnal vertical migrations?

fish are releasing gas as they migrate to control buoyancy

how do krill experience different vertical migrations during their life cycle?

The adult females spawn in Arctic waters in the summer; The eggs then sink and hatch when they near the bottom; The eggs hatch and become larvae then rise to the surface to feed on phytoplankton; By the time the larvae reach the surface in their migration, the phytoplankton are in bloom; Then, in the fall, their eyes start to form; As sea ice forms, the krill begin to feed on the algae underneath the ice; Then, as spring comes around, the krill become adults and repeat the cycle with reproduction in the summer

how does climate change affect krill vertical migration?

Climate change affects this pattern though because the ice is retreating, causing a mismatch in timing in the krill's vertical migration cycle

the smaller the plankton, the lower the...

Re#

what does a low Re# mean?

there is a boundary layer around the plankton's body that causes the plankton body to be dragged by the surrounding water

stokes' law

If a particle is small and the velocity slow, its sinking velocity will increase with increasing weight of the particle; These organisms will reach a constant terminal velocity; Larger organisms will sink faster than smaller organisms of the same density; Irregularly shaped plankton tend to fall at lower velocities than predicted by Stokes' Law

where does most production occur?

in the surface waters via phytoplankton photosynthesis

how does phytoplankton death affect consumers in the deep?

not all phytoplankton is consumed by zooplankton, so some plankton die and sink to the deeper waters, which supplies organic matter to many consumers in the deeper water

during what season do plankton fall to the benthic with the highest frequency?

summer (they die after the spring bloom)

marine snow

aggregates of dead particles; the base of the deep-water food web

what factors affect the vertical position of plankton?

bulk density, features of the organisms that influence drag, swimming behavior, turbulence

a particle will remain suspended if...

1) it is less dense than seawater or of equal density so it is neutral

2) it has a shape that increases drag and reduces settling velocity

3) it can swim

4) water turbulence keeps the particle suspended in the water column

what are some floatation mechanisms?

gas-filled sac that acts as a float (Portuguese-man-of-war); Regulation of bulk density through variations in chemical composition (dinoflagellates and cyanobacteria); Oil droplets to increase buoyancy (diatoms); High lipid contents (copepods); Gas secretion (smaller nekton); Swim bladder (fish);

Shape of fish (plankton - jellyfish, diatoms, Flat bottom and tentacles create drag to slow sinking, Twisted chains of diatoms that spiral as they sink, Projections in zooplankton); Swimming (Flagellated phytoplankton, Dinoflagellates)

uses of bioluminescence

startle, counter illumination, smoke screen, lure prey, illuminate prey

what are some deep sea characteristics?

bioluminescence, big jaws, barrel eye, weak skeleton

why do deep sea fish have big jaws?

to ensure prey is captured in the rare occurrence prey is encountered

why do deep sea fish have barrel eyes?

to search for scare deep food

why do deep sea fish have weak skeletons?

due to the pressure of the deep

What might be a defense for the smaller preys against larger predators in deep sea?

Puke glowing fluid to predator --> predator now becomes potential prey because glowing in the dark --> predator swims away

what are some samples of defenses that phytoplankton and zooplankton have evolved to avoid predation in the deep?

spines and armature; transparency; toxic substances; bioluminescence

counterillumination

Generated by ventral bioluminescent organs to hide their position in low-sunlight conditions; Photophores concentrated on ventral surface; Eliminates a shadow when predators beneath the fish look upward into the down-welling light from the sun and moon

what are examples of organisms that use a startle flash to confuse predators?

dinoflagellates, squid

what are examples of organisms that use counter illumination as a defense?

fish, crustaceans, squids

what are examples that use smoke screen as a defense?

fish, crustaceans, squids, ctenophores, larvaceans

what are examples of organisms that lure prey or attract host?

angler fishes, siphonophores, cookie cutter shark

what are examples of organisms that use bioluminescence to illuminate prey?

dragonfish, flashlight fish

what particle sinks the slowest?

living phytoplankton

what particle sinks the fastest?

fish eggs

what is a thermocline?

Surface waters are the warmest, while the deeper water is colder; In the middle, there is a rapid transition between cold and warm water; This temperature gradient is a thermocline

what is a pycnocline?

a density gradient

what is the importance of thermoclines and pycnoclines?

The thermocline and pycnocline make the water column very stable, which in turn makes the water harder to mix and overturn; In order to achieve adequate mixing, the difference between the warm surface water and the colder depths need to be reduced --> this occurs in high latitudes and winter!

the chlorophyll max does not occur right at the surface because...

the surface layer s nutrient depleted and the sun can be harmful if too intense (conversely, in the deep, there is not enough sunlight)

migration

Species of large-bodied nekton, such as whales, tuna, and sharks, follow specified large-scale migration routes, stopping at foci of food abundance such as upwelling centers

how might global warming dwindle the supply of a key brain nutrient?

as waters warm, it impacts organisms in the layer and they have to adapt, which might affect their compositions (essential fatty acids that humans rely on)

why is it that as there are more whales, there are more plankton?

nutrient-rich feces boost plankton growth (excretion in the surface layer where nutrients are usually depleted so now more nutrients for phytoplankton)

why are blue whales the size that they are?

whales must gain more energy from krill than the energy expended to hunt the krill, so whales are picky about which plankton patches they eat; their size is the max size they can achieve while balancing the energy in and energy out

what mechanisms cause the spring phytoplankton bloom and its decline?

light, mixing, nutrient, predation

what is the seasonal pattern of plankton abundance in mid latitudes (temperate-boreal waters)?

phytoplankton increase in the winter through spring, decline in summer, and may increase to a lesser extent in the fall; zooplankton start to increase as the phytoplankton bloom reaches its peak, attaining a max following the phytoplankton peak in the late spring or early summer (no second peak though because fall phyto peak is small)

what is the seasonal pattern of plankton abundance in high latitudes (Arctic)?

Single summer peak of phytoplankton abundance following by zooplankton max

what is the seasonal pattern of plankton abundance in the tropics?

rhe spring phytoplankton peak and the later zooplankton peak are nearly indistinct in the tropics due to the relative lack of seasonality

how does light behave in water?

light declines by attenuation and scattering as water gets deeper; turbulence and particles scatter light even more

how does photosynthesis increase with increasing light intensity?

photosynthesis increases with increasing light intensity, up to a plateau, and then is inhibited by high light intensity

what are the physiological adjustments to changing light conditions?

total photosynthetic pigment content; pigment proportions; morphology of the chloroplast; chloroplast arrangement; availability of Calvin cycle enzymes

compensation depth

the depth at which the amount of oxygen produced by a phytoplankton cell in photosynthesis equals the oxygen consumed in respiration

how does compensation depth differ in temperate-boreal waters?

as spring progresses, the increasing photo-period tends to increase the compensation depth to a max

how does compensation depth differ in Arctic waters?

in the winter, the photo-period is zero, so there is no light for photosynthesis

how does compensation depth change during a phytoplankton bloom?

suspended matter becomes trapped in water column and decreases compensation depth due to light absorption and shading by particles

compensation light intensity

the light intensity corresponding to the compensation depth; occurs when the photosynthetic rate equals the amount of oxygen consumed in respiration

______ light penetrates the deepest

blue

_______ water has a deeper compensation depth

clear tropical

gross photosynthesis

total amount of carbon fixed or oxygen generated

net photosynthesis

net primary production (the energy transferred to the next trophic level)

why does photosynthesis hit a max at a certain light intensity?

too much light can cause harm via UV damage

how does photosynthesis work?

fixes inorganic carbon dioxide and converting it into organic carbon, where oxygen is the waste produced

______ and ______ decrease oxygen in the water

respiration; decomposition

in what season does deeper stirring/mixing of water occur?

winter (might get pushed too deep away from sufficient light)

what is the difference between compensation depth and critical depth?

critical depth is the collective photosynthesis and respiration whereas compensation is within a single cell of a phytoplankton

mixing depth

depth above which all water is thoroughly mixed, due to wind

critical depth

depth above which total oxygen produced in the water column equals total consumed (The depth above which total production of oxygen from photosynthesis in the water column equals total consumption from respiration)

what happens if the mixing depth is less than the critical depth?

phytoplankton bloom

what happens if the mixing depths greater than the critical depth?

no bloom

when does max sunlight occur?

summer

when are nutrients highest?

winter

how do zooplankton increase in relation to their prey phytoplankton?

zooplankton increase with a slight delay as their prey, phytoplankton, increase; they decline after the collapse of phytoplankton (which collapse due to using up the nutrients and grazing)