Marine Bio Quiz 5

Where are sea grasses found

all over the world, shallow temperate subtropical waters

are sea grass mono or di cots

monocotyledons (grasses, lilies, palms)

what anatomical parts make up sea grass?

roots, leaves, veins & produce flowers & seeds

what is the max depth sea grasses grow determined by

light availability

what function do veins serve in sea grass

transport nutrients and water through the plant, lacunae (air pockets) that keep leaves buoyant and exchange O2 and CO2

How do sea grasses’ leaves preform gas exchange

lack stomata, instead, a thin cuticle layer allows gasses and nutrients to diffuse in and out of leaves

What are rhizomes in seagrasses?

Thick horizontal stems with roots that extend into sediment of seafloor, also used for storage and absorption of nutrients and anchoring of plants

How does sea grass preform asexual reproduction?

through rhizomes, they send up new shoots (fastest method of population growth of many sea grass species)

How does sea grass preform sexual reproduction?

similar process to terrestrial plants, water aids in pollination

• male flowers release pollen from stamen into water (longest pollen grains on planet) (stringy clumps)

• small invertebrates also help w pollination (feed on it) (amphipods, polychaetes)

• develops seeds after fertilization

• seeds float long distance before germination due to neutral bouyancy

• animals (turtle and fish) may aid in seed dispersal

What are the four major families of sea grasses?

• Zosteraceae

• Hydrocharitaceae

• Posidoniaceae

• Cymodoceaceae

what are tides

waves caused by the gravitational pull of the moon and sun

how does the frequency of tides work?

two low tides and two high tides every lunar day (24hrs and 50 mins)

• driven by gravity of moon

• tidal bulge on either side due to greater/less gravity than the center of the earth

• tidal bulge rotates around earth with respect to moon

• bulge-high tide

Spring tides

• during full or new moon when the sun earth and moon are in line

• gravitational force of sun amplifies that of moon - maximal vertical range

• 2 per month

Neap tides

• when the sun, earth, and moon form a right angle-quarter moon

• gravitational effects cancel each other out- minimum vertical range

• 2 per lunar month

What plant dominates salt marsh ecosystems

spartina alterniflora

What is the worldwide marsh distribution

equator is where mangroves exist, salt marshes occur ~30 degrees N & S

why are salt marshes considered carbon sinks?

• they are extremely efficient at carbon sequestration and carbon storage

• sequester 10x faster than mature tropical forests

• store 3-5x more in a given area than tropical forests

What are the reasons salt marshes can store large quantities of carbon?

• lots of new plant growth each year (highly bioproductive)

• Anaerobic soils cause carbon containing substances to decompose very slowly (100s-thousands of years)

What would be the reason salt marshes would add additional green house gases to the atmosphere?

when they are damaged/destroyed they lose the capacity to sequester carbon and may release it into the atmosphere

what is the difference between sequestration and storage?

• sequestration invloves pulling CO2 out of the atmosphere, plant sequestor through photosynthesis but this is not a form of storage since they must continuously use CO2 for their life processes

• Salt marshes store carbon by burying plant material that does not get decomposed for long periods of time, carbon is not re-released

Where is S. alterniflora native and where does it grow?

• eastern & gulf coast of American marshes

• lowest in the intertidal zone

  • immersed in salt water

  • high tolerance to salinity

Why is the sediment surrounding the roots of s. alterniflora anoxic?

regular water inundation

Anatomically, how is s. alterniflora structured?

• round, hollow stems

• strong, interconnected root system

• short and tall varieties

• smooth blade like leaves taper to a point

How is the stem of s. alterniflora specialized to oxygen transport?

• contains large amounts of open space devoted to air and o2 transport

• called aerenchyma tissue

• allows connection between aerobic leaves and stems/roots which lack access to o2

why is smooth cordgrass considered a halophyte?

• high tolerance to salinity

• has salt glands that secrete excess salt through leaf surface

describe the mutualistic relationship between s. alterniflora and ribbed mussels?

• mussels move nitrogen from water column into sediment, stumulating cordgrass growth

• spartina provides refuge from predators and heat stress

Describe the mutualistic relationship between s. alterniflora and fiddler crabs?

• burrows aerate roots which helps mychorrhizal fungi

• spartina binds soil, creating habitat for crabs to burrow and feed

How is s. alterniflora suited against herbivory?

• salt excretions deter grazing by birds and mammals

• cellulose and tough leaves prevents grazing

Describe the role leaf tissue decomposition of s. alterniflora can play in salt marsh ecosystems?

• decomposition of leaf tissue supports bacteria and fungi populations

• marsh periwinkle create and innoculate fungi in wounds of leaf tissue causing fungi growth which they feed on (fungal farming)

  • important food source, keep s. alterniflora in check

How does asexual reproduction of s. alterniflora work?

• involved vegetative fragmentation or rhizomes

• morphology of rhizome system and shoots create projections that form a baffle against water movement and encourages sedimentation

  • may result in meadow formation

How does sexual reproduction of s. alterniflora work?

• they develop flowers and set seed

How does s. alterniflora colonization and development work?

• a single plant may colonize by rafting or setting seed

• grass blades become dense enough to slow current speeds and accelerate deposition of fine-grained settlement

• sediment surface rises leading to spread of marsh and evolution into meadow of sediment

• eventually peat accumulates (high organic matter, nutrient rich)

• sediment surface rises, plants change from low inter tidal grasses to terrestrial plants

How do vegetational zones in salt marshes develop?

• through competition and physiological ability to survive salt and drowning

• each zone determined by different grass species

• most east coast/gulf marshes have tall alterniflora in low intertidal and short alterniflora in high intertidal

• sharp distinct zones

what does the term “wrack” describe in terms of s. alterniflora?

• the accumulation of old stems that become floating rafts

• stems concentrated by currents and then float up to rest on top of grass in the high marsh

How does the phenomenon of wrack promote biodiversity in salt marshes?

• they smother sections of grass and create bare zones

• evaporation occurs in bare zones resulting in saline environment preventing seed germination of seeds present in soil

• allows new seeds to grow in that area

How does sea level rise impact salt marshes?

marshes cant expand, they get lost to sea

How does pollution impact salt marshes?

ecosystem cant preform carbon storage as normal due to damage to plants or altered soils

How do invasive species harm salt marshes?

phragmites australis can alter natural functioning of salt marsh ecosystems by shading out/out growing alterniflora

what plants are characteristic of Mangroves?

emergent plant communities dominated by trees rooted in marine soft sediment/anoxic muddy sediment waterlogged with seawater

How are mangroves distributed?

tropical & subtropical

Where does detrital material come from in mangroves?

continuously large numbers of falling leaves

how did mangroves evolve?

independently from ancestors in a number of plant evolutionary groupsh

why are mangroves important

• buffer shoreline from wave action & storm surge, prevent erosion

• good at carbon sequestration (blue carbon)

• fish habitat (goliath grouper)

• sustain coastal fisheries

how are plants in mangroves adapted to anoxic sediment?

• broad-shallow roots

• root extensions project in air to provide oxygen for underwater/ground roots

• upward directing roots transport O2 to below ground tissues ensuring aerobic metabolism

what are the different root morphologies in mangroves?

• prop roots

• knee roots/pneumatophores

• finer roots

what are prop roots in mangroves

structures that extend midway from trunk and arch downward for support

What are knee roots/pneumatophores in mangroves?

roots that direct upwards into the air

What are finer roots in mangroves?

roots for gathering nutrients

why are mangrove roots susceptible to salt?

mangrove roots penetrate into a surface sediment layer that is of high salt content- known as the valdose layer (less than full strength seawater bc of rainfall)

how are mangroves adapted to high salt environments

• salt glands secrete salt from leaves

• roots reduce salt uptake through filtration system and store in vacuoles to maintain osmotic gradient

what is the red mangrove

• rhizophora mangle

• dominates seaward part of mangrove forests

• 1st to colonize

• prop roots

• tolerates full strength seawater and tidal inundation

what is the black mangrove

• avicennia mangle

• shoreward of red mangroves

• tolerates only occasional sea water inundation at high tides

what are white mangroves

• laguncularia racemosa

• rarely inundated by seawater

how does seeding dispersal and invertebrate predation on seedlings shape zonation?

• red mangrove seeds germinate while attached to parent plant

• seedlings dangle until they drop in mud or float away on water

• graspid crabs can cause massive mortality to new seedlings, determining species composition in individual mangrove forests

what is blue carbon in relation to seagrass?

• benefit of seagrass ecosystems where they sequester and store large amounts of carbon from atmosphere

• carbon stored underground as dead/decaying plant material

• seagrasses occupy .1% of total ocean floor byt responsible for ~11% of all organic carbon buried in ocean

how are epiphytes involves in seagrass ecosystems?

• bacteria fix N, make available for larger animals

• small inverts graze on epiphytes

• dead seagrass leaves support large communities of decomposing organisms

• epiphytes grow on leaves and may reduce light capture and photosynthesis