MAR305 Exam 2

70-90

Copepods are ---% of herbivore mass

Diurnal

Events that occur during the day

Nocturnal

Events that occur during the night

Diel

events that occur within a 24 hr periodicity

Diel Vertical Migration (DVM)

Generally an upward migration at dusk and downward migration at dawn

vertically

Plankton can not swim against currents but can move ---

DVM

Almost all holoplanktonic groups participate in ---

life stage, sex

DVM may vary with --- and/or ---

10-170 m/hr

Small taxa DVM speed

100-200 m/hr

Large taxa DVM speed

Deep scattering layer

-layers in oceans detected by sonar
-Appear as false bottoms
-up to 5 during day
-merge upward into shallow band at night

strong

Animals with a strong density and/or sound speed contrast will produce --- echos

euphausiids, shrimp, small fishes

DSLs are dominated by ---, ---, and ---

ambient light

Suspected cue for DVM

Isolumes

lines of constant light followed by DVM organisms

visual predators

DVM may reduce vulnerability to ---

abundant

DVM is most pronounced when predatory fish are ---

surface

Under conditions of abundant food DVM organisms spend more time at the ---

surface, cold deep water

DVM organisms may conserve energy by feeding at the ---, and spending non-feeding time in ---

Horizontal advection

DVM Benefits of ---
--Zooplankton graze down food while at surface
--Avoid rising into same low food region on next night
--Will also enhance genetic change

Consequences to DVM

-transfer of energy from surface to depth
-Herbivores graze on surface at night the release fecal pellets and organic debris at depth
-Deep carnivores graze on herbivores at depth transporting energy deeper

faster

DVM energy transport to deep waters is --- than sinking

patchy

Zooplankton have a --- distribution

patchy distribution

Unreliable net tows are a result of zooplankton's ---

Hard Bottom

Nonliving rock or biologically derived hard substrates (coral, oyster reef)

Soft Bottom

organisms associated with sand or mud

Infauna

organisms that live within the sediments beneath the sediment-water interface (worms, clams)

Epifauna

organisms that live on top of the sediment surface

Microfauna

Meiofauna

0.1-1 mm (small copepods, nematodes, and juveniles of the larger organisms)

Macrofauna

>1 mm (bivalves, shrimp, and brittlestars)

above them

Benthic communities are dependent on the rates of primary production occurring -- them

below

Benthic communities typically occur --- the euphoric zone

increased

In areas of high plankton production you find areas with --- density of benthic organisms

nearshore

There is a higher density of benthic biomass in --- waters

larger

Cold water species are --- than warm water taxa

planktotrophic

Larval development is --- in tropical regions

direct developers/live births

Larval development is --- in polar regions

increases

tropics -> temperate -> polar epifaunal diversity ---

silt/clay substrate

small organisms, many deposit feeder and few filter feeders

Sand substrate

large organisms, many filter feeders and few deposit feeders

Sediment reworking

The effect of organisms that create burrows or that feed in sediments have on the characteristics of those sediments

sediment, large

Burrows change the --- chemistry and produce --- amounts of fecal material

Sandy

--- bottoms are characterized by continental shelves, shallow water, high flow, little to no accumulation, redistribution, low organic content, permeable

Muddy

--- bottoms are characterized by deep waters, estuaries and harbors, low flow, sediment accumulation, high organic content, low permeability

less

Fast air = --- pressure

more

Slow air = --- pressure

Pressure gradients

--- drive flow

velocity

--- determines how much water is advected

active, passive

Advection is an --- process and diffusion is a --- process

mixed

--- sediments result in the highest diversity of deposit and suspension feeders

size

Fecal mounds change the --- of sediment present in a given area

aerate, O2, anoxic

Burrowing activities --- sediments and allow --- rich water to penetrate --- sediments

increase

Burrowing activities --- the amount of habitable area

stabilize

Dense assemblages of tube building organisms --- the sediments so that suspension feeders can colonize an area

Bioturbation

-dominated by deposit feeders that ingest sediment
-increase sediment cycling to the surface
-Increase pore water irrigation of sediments
-increase oxygen transport into the sediments
-organism uptake contributes to transmission up food chain

Biologically mixed zone

Plowers

Sediment destabilizers

Tube builders

sediment stabilizers

Worm tubes

-animals "engineer sediment with tube mounds or pits
-Increases flux of food, oxygen, and wastes into/out of sediments
-Some species create dense fields of these
-leads to extremely diverse communities within these tube fields
-presence makes benthos more permeable, oxygenates depth, Bernoulli's principle of velocity and pressure aerates these features and sediments

Suspension feeders

Organisms feed upon particles suspended in the water column

Active suspension feeders

organisms that pump water across their food collecting apparatus (clams)

Passive suspension feeders

Organisms that rely on water currents to cary food past them (sea fans)

perpendicular

Passive feeders orient --- to the movement of water

concave, towards

Feeding apparatus of passive feeders is frequently --- and oriented --- the current

high

Passive feeders preform better in areas of --- flow

Food of suspension feeder

microzooplankton, small macrozooplanton, larvae and eggs, bacteria, viruses

Deposit feeders

Consume particles from the sediment usually by pressing some feeding organ against the substrate

Swallowers

Swallowing sediments; little selectivity (many worms and snails)

Tentacular feeders

Use tentacles to trap particles by pressing against the substrate and transfer to mouth

Siphon feeders

Vacuum sediments into themselves, above or within sediments

size, organic matter

Feeding rate of deposit feeders is determined by the --- of the organism and independent of the ---

Coprophagy

Consumption of fecal material, may appear to be a poor strategy but these fecal pellets become colonized by bacteria in 1-2 days

allochthonous

Benthic secondary production is controlled by --- inputs of organic matter, although energetic requirements can be supplemented with in situ benthic micro and macroalgal primary production in shallow waters

Water column productivity, water column depth, sinking rates and the intensity of vertical mixing

The level of benthic primary production or supply of allochthonous organic material to the seafloor is usually a function of...

Parallel bottom communities

Benthic communities from around the world occurring at the same depth and possessing similar species and sediment types

predation, exploitative

In soft sediment communities --- dominates and competition is ---

Allelopathy

The harmful effect of one organism on another caused by the release of chemical compounds produced by the first

Rocky Subtidal Communities

-densely covered by low growing plants and sessile or sedentary animals (sea urchins, crabs, and gastropods)
-2D systems
-Suspension feeders dominate (sponges, tunicates, bryozoans, and various cnidarians)

Subtidal Environmental parameters

-Never exposed to extreme atmospheric conditions
-Water temps are mild with little variation
-exist in areas of upwelling so nearly always adequate supply of nutrients
-Water always moves; tides and wind driven currents

Disturbance, competition, predation/grazing

What structures rocky subtidal communities

Sea urchin

Consumes algae and opens space for mussels to colonize

Mussel

Provides a surface that improves sea urchin stability and a predation refuge

Starfish

Removes mussels and reduces sea urchin densities

Alternative stable sates

-The existence in the same area of different groups of organisms or patches of organisms
-Result when some factor or set of factors disturbs the dominant species causing the community to switch into a new composition which in turn remains stable until disturbance

Kelp forests

-subtidal communities in areas of strong currents and heavy surf
-Rocky intertidal communities merge into ---
-annuals or perennials
-regrowth from holdfast yearly or every few years
-reproduce by spores
-require hard substratum

20 C

Kelps are generally restricted to regions where summer temps do not exceed ---

Mann 1973

-punched holes in blades of laminar that dominates St. Margaret's Bay in Nova Scotia
-Observed that kelps grow like a conveyor belt
-annual production 1000-2000 g/C/m2/yr
-despite dark and cold environment

pneumatocysts

gas filled floats keeping kelp blades near water surface

blades

Kelp photosynthesis is concentrated in the ---

Detrital food web

-Up to 90% of kelp production ends up here
-Plant fragments, even whole blades or plants
-Exudation of dissolved organic matter

Inverse

There is an --- relationship between kelp and sea urchins

Paine and Vadas 1969

-Grazing by sea urchins limits kelp distributions
-The first ecologists to recognize the importance of urchin grazing on kelps
-Kelps dominated areas from which urchins excluded
-Hedopyllum in intertidal pools and Laminaria in subtidal pools following early succession

Vadas 1977

-Sea urchins have food preference correlated with kelp competitive ability
-They like nereocystis the best and Agarum the least
-Sea urchins get more energy eating nereocystis than kelps like agarum
-assimilate 84-91% of what they ingest compared to 36-52% for chemically defended species
-Important fitness consequences; grow faster, produce more gonads with access to preferred food

Foundation species

Kelps are considered ---; large size and 3D structure creates a complex variety of habitat and foraging areas for many other species

Estes and Palmisano 1974

-effects of otters on subtidal benthic communities
-otters are size-selective predators
-At amchitka otters eat big urchins leaving only small urchins

keystone predator

Sea otters act as --- of urchins

Atlantic

In the --- ocean all predators of urchins have been overfished and cannot control their abundance (no otters in this ocean)

Elner and Vada 1990

-What controls urchin abundance and aggregative behavior?
-Lobsters as keystone predators on urchins? NO
-Lobsters, fish, and crabs preying on urchins? NO
-Episodes of extremely high recruitment? YES
---causes aggregations and switch to coralline barrens
-Disease (parasitic amoeba) at high densities? YES
---causes mass mortality of urchins and switch to kelps

competition between kelp species

In the absence of disturbance kelp forest composition is determined by ---