Marine Ecosystems 2

oldest and most structurally simple of all living vertebrates

marine fishes

3 types of marine fishes

jawless, cartilaginous, bony

agnatha (jawless) examples

hagfish, lampreys

chondrichthyes (cartilaginous) examples

sharks, skates, rays, ratfish

osteichthyes (bony) examples

lobe-finned fish, ray-finned fish

coelacanth is known as

a living fossil

characteristics of jawless fish

muscular, circular mouth with circular rows of teeth

long, cylindrical body

lack paired fins, scales, bones

have cartilage

hagfish

only marine

feed on dead/dying marine mammals, live in burrows in soft sediments

produce lots of mucus from skin glands for protection while feeding

lamprey

live in both freshwater and seawater (freshwater to breed)

feed on living fish: attach and consume blood, tissue, body fluids

no natural predators

characteristics of cartilaginous fish

cartilage skeleton: non-vascular, fibrous, firm

moveable jaws with well-developed teeth

placoid scales and paired fins

spiracles, male claspers

spiracles

present in cartilaginous fish

openings on the head to bring in water used for respiration without having to open the mouth

claspers

present in male cartilaginous fish

projections of the anal fin used in copulation

sharks

primarily marine

most with 2 dorsal fins, enlarged pectoral fins

powerful jaws with triangular teeth

many are carnivorous, some filter feeders

ampullae of lorenzini

various modes of reproduction

no swim bladder: large lipid-rich liver helps for bouyancy

filter feeders use

gill rakes for filtering water

ex. whale shark

ampullae of lorenzini

sensory organs present in sharks

detects electrical currents for prey detection

viviparous

internal fertilization

embryo has placental connection

fetus develops in the womb

live births

oviparous

internal fertilization

embryo development is external

egg yolk nourishes, hard shells for protection

ovoviviparous

internal fertilization

no placental connection

animal lays eggs and keeps them internal until they hatch

parthenogenesis

asexual reproduction

rays

pectoral fins expanded into wings

ventral gill slits and mouth, spiracles on top of body

spend much of their time on the bottom partially covered in sediment (demersal)

give birth to live young (ovoviviparous, viviparous)

electric rays

have organs that produce electricity on either side of the head

manta rays

plankton feeder in mid water, gill rakers used to filter water

skates

fleshy tail with no spine

always lay egg cases

demersal, feed mostly on molusks

ratfish

mostly deep water

gill slits covered by flap of skin

feed on bottom crustaceans and mollusks

bony fish

homocercal tail, flat bony tails

swim bladder used for buoyancy control

lateral line for sensory information

homocercal tail

two lobes of equal size

countershading

dorsal surface is darker than ventral (belly)

top view blends with ocean floor, bottom view blends with ocean water

disruptive coloration

bars or stripes break up silhouette for predator avoidance

cryptic coloration

helps blend with background

warning coloration (aposematic)

advise bad taste, poisonous nature

caudal fin swimmers

‘s’ shaped swim pattern

bands of muscles along body drive swimming motion

swim bladder

bony fishes

filled with gas

provides buoyancy

gill construction

gill arch: support

gill rakers: outer surface of gill arch

gill filaments: behind gill arch

diffusion of oxygen, co2 in fish

along capillaries in the lamellae that cover the gill filaments

water flows opposite direction of blood,

water always more oxygenated than blood

fish digestion

intestine, pyloric caeca, pancreas, liver secrete digestive enzymes

fish circulatory

2 chambered heart

water as the universal solvent

substance dissolved in water = solute

salinity = level of solutes

lots of sodium, chloride

osmoregulation in marine fish

outside environment more salty than inside

tend to lose water and gain solutes

need to regulate to prevent dehydration

concentrated urine

osmoregulation in bony fish

pass very little but very concentrated urine

swallow seawater, excrete excess salt through kidneys/intestine

osmoregulation in cartilaginous fish

keep blood at about the same concentration as the sea water

urea in blood: toxic compound resulting from breakdown of proteins

fish nervous system

brain, spinal chord, nerves

lateral line system

olfactory sacs with external nostrils for detecting compounds in water

tastebuds in mouth, lips, barbels, skin

lateral line system

series of pores and canals lined with cells (neuromasts) specialized to detect vibrations

schooling

small fish can appear larger, make it hard for predator to capture any one fish

territoriality

some all the time, some only during reproduction

show aggressive behaviors (posturing)

fights between individuals is rare

migration in estuaries

alternation between fresh/sea water for reproduction

salmon/lampreys/sturgeon: sea → fresh to reproduce

american eel: fresh → sea to reproduce

broadcast spawning

release of eggs and sperm directly into water

protandry sex reversal

first male then female

protogyny sex reversal

first female then male

carbon cycle

carbon used used by primary producers for photosynthesis

CO2 released by all organisms through respiration and decomposition

nitrogen cycle

most abundant gas in the atmosphere (78%)

only bioavaliable through biofixation

phosphorus cycle

crucial for marine life (phytoplankton)

too much can lead to harmful algal blooms

salt marshes

cordgrass dominates along waters edge

high primary production

nursery for young of many species

contribute detritus to estuary

flowering plants in estuaries

expel excess salt through salt glands (cordgrass, mangroves)

concentrate solutes in tissues (pickelweed)

pneumatophores

in mangroves

vertical and aerial root extensions, help in gas exchange

(sediment is usually anoxic)

mangrove trees

tropical and subtropical coasts

replace salt marshes in these areas

high primary production

protect coasts against wave action from storms

estuary

semi-enclosed area where fresh/seawater meet

wide changes in salinity, temp, exposure to air, presence of soft sediments

low species diversity, but high biomass

dominant organisms are phyto/zooplankton, fish

estuary development

areas where coastal plains are flat and continental shelf is wide

drowned river valleys

most common type

formed by drowning of low land around mouths of rivers when sea level rose after the last ice age

bar-built estuaries

built by accumulation of sediment into sand bars or barrier islands parallel to coast

a lagoon forms

limited tidal influence

tectonic estuaries

formed as a result of land sinking due to movement of Earth’s crust

fjords

deep valleys cut on the coast as a result of retreating glaciers

estuary salinity

varies between 5-30% based on distance from seawater tides and freshwater input

salt wedge: saltwater more dense than fresh

eurohaline organisms

typical of estuary organisms

tolerate a wide range of salinities

stenohaline organisms

tolerate a narrow range of salinity

osmoregulators

mechanisms for keeping internal concentrations stable

osmoconformers

internal concentrations vary with surroundings

oyster reefs

found in many estuaries, may provide the only hard substrate

rocky shore vertical zonation

universal feature of rocky shores

1. black lichen zone

2. periwinkle zone with sparse barnacles

3. barnacle dominated zone either overlapping with a muscle dominated zone or with muscles below

4. dominated variously, usually by seaweeds

environmental stressors of vertical zonation

heat stress, desiccation (drying out), gas exchange, reduced feeding time, wave shock, biological interactions (competition, predation)

vertical spatial gradient

tide levels, time of exposure to air/water

horizontal spatial gradient

changing wave exposure

heat stress/dessication reduction

body size and shape are important (reduction of surface area/volume ratio reduces heat gain/water loss)

evaporative cooling and circulation of body fluids reduces heat loss

well-sealed exoskeletons reduce water loss

heat shock proteins

heat shock proteins

used to reduce temp stress

low intertidal species produce more when stressed w high temps

higher intertidal organisms and heat stress

more resistant to heat

less time to feed, sessile forms, grow more slowly than lower intertidal organisms

negative geotaxis

organism moves away from gravitational pull to avoid predation and high tide

negative photoaxis

organism moves away from light to avoid predation

positive photoaxis

organism moves toward light for feeding, reproduction, finding new habitat

wave shock effects

abrasion: particles in suspension scrape surfaces

pressure: hydrostatic pressure of breaking waves

drag: can pull organisms from their attachments

vertical zonation causes

physiological tolerance

larval/adult preference

competition

predation

behavior

conclusion from connoll’s experiments

1. predation is important in lower intertidal

2. biological factors control the lower limit of species occurrence

3. physical factors control the upper limit

4. community structure is a function of local processes

disturbances

physical events that influence the distribution and abundance of organisms

may reduce abundance of competing species

may allow coexistence of competitively inferior species or colonization of species adapted to disturbance

spatial scale of disturbance might affect spatial pattern of dominant species

pelagic

water column away from the bottom

epipelagic

includes the sea surface to a depth of about 200 meters

includes neritic and oceanic

neritic

waters over the continental shelf

oceanic

waters beyond the continental shelf

epipelagic characteristics

warmest and most well-lit portion of the water column

lots of primary production

limitations of epipelagic

no substrate for attachment, no bottom for burrowing or deposit feeding, limited places to hide from predators

infralittoral zone

shallow water closest to the shore and below the low-water mark

circalittoral zone

deeper than infralittoral, dominated by immobile organisms like sponges/bryozoans

sublittoral zone

extends from ocean floor near the shore to the edge of the continental shelf

plankton

thrive in epipelagic

classified by size

all organisms that can’t swim against prevailing wind currents (drifters)

plankton size classification

picoplankton < 2 to 3 microns

nanoplankton 2 to 20 microns

microplankton 20 to 200 microns

macroplankton > 200 microns

types of plankton

holoplankton, meroplankton, phytoplankton, zooplankton

holoplankton

entire life of the organism is spent in the planktonic realm

ex. pteropods, jellyfish/comb jellies, arroworms

meroplankton

only a portion of the life of the plankton is spent in planktonic realm

(fish larvae, mollusks, crustaceans)

phytoplankton

performs photosynthesis (primary producers)

zooplankton

heterotrophs (consumers)

marine diatoms

photosynthetic, shell of silica called a frustule, mostly solitary and unicellular

marine dinoflagellates

mostly photosynthetic, plates of cellulose reinforce, some are bioluminescent

ex. zooxanthellae

radiolarians

shell of silica, pseudopods to capture particles,