Chapter 12 Estuaries

What type of bacteria thrives under anoxic conditions in the sediments of estuaries?

Anaerobic bacteria

T/F: Salt marshes in the Northern hemisphere tend to be more extensive on the left side than on the right side of estuaries since the turbulence cause by the flow of freshwater from rivers is stronger on the right side as a result of the ___?

Coriolis Effect

How is salinity shifted in both diurnal and semidiurnal tides in estuaries?

Diurnal: 2 shifts in salinity daily Semi-diurnal: 4 shifts in salinity daily

What is the most common type of estuary?

Drowned river valley

T/F: Water temperature in estuaries varies in fjords

FALSE

T/F: Marine organisms that live in estuaries have to adapt to increased salinities

FALSE Marine organisms have to adapt to REDUCED salinities

T/F: Most estuarine organisms are stenohaline species

FALSE most are EURYHALINE

T/F: Both mudflat organism and soft-bottom intertidal organisms must withstand regular variations in salinity

FALSE only mudflat organisms must withstand regular variations in salinity

T/F: Suspension feeders are more common than deposit feeders on mudflats

False, deposit feeders are more common

T/F: Salinity increases as one moves upstream

False: Salinity decreases as one moves upstream the more freshwater mixed in, lower salinity

How does the Coriolis effect affect circulation in estuaries?

N of Equator- freshwater flowing toward sea deflected right S of Equator- flow deflected left Estuaries in N hemisphere- marine organism penetrate upstream on left side S Hemisphere- extend up right side

How do estuarine ecosystems face the problem of the water in estuaries being diluted with freshwater?

Osmoconformers-have internal salt concentration higher than that of surrounding water take on water thru OSMOSIS others hide in mud burrows, close shells, swim away

How is a salt wedge affected by the tides?

Salt wedge moves up the estauary on rising tide, recedes when tide falls Organisms submerged under salt wedge at high tide and under low-salinity water at low

What type of bacteria uses hydrogen sulfide in mudflats and why?

Sulfur bacteria (chemosynthetic) derives energy by breaking down sulfure compounds like H2S

T/F: Diatoms and bacteria account for most of the primary production on mudflats

TRUE

T/F: Primary producers are not usually evident on mudflats

TRUE

T/F: Salinity fluctuations are LESS drastic in the mud than in the water column.

TRUE

What region has the world's most extensive mangrove forest w/ the largest # of mangrove species?

The Indo-West Pacific Region

T/F: In regions of little freshwater runoff and high evaporation , the salinity of the water increases

True

T/F: Mangroves grow on protected coasts where muddy sediments accumulate

True

T/F: Most infauna in mudflats are deposit feeders

True

T/F: Salt marshes are subject to the same extremes in salinity, temperature and tides that affect mudflats

True

T/F: the most important predators in the mudflat community are fishes and birds

True

What is a salt wedge?

a layer of denser, saltier seawater that flows along the bottom in estuaries

What is the landward limit of salt marshes?

a transitional zone with adjacent terrrestrial, or land communities it is characterized by a lare variety of plants resistant to salt spray: salt grasses and pickle weed

How are bar-built estuaries formed?

accumulation of sediment along coast builds up sand bars and barrier islands that act as a wall between the ocean and reshwater from rivers Ex: Texas coast of the Gulf of Mexico

How do osmoconformers cope with salinity fluctuations in estuaries?

allow bodily fluids to change with the salinity of the water Ex: soft-bodied estuarine animals- molluscs, polychaete worms

Where do salt marshes develop?

along sheltered open coasts develop as long as wave action disturbance is minimal to allow the accumulation of muddy sediments tidal creeks, freshwater sreams, shallow pools cut thru marsh

How were drowned river valleys formed?

also called coastal plain estuaries sea level rose because of the melting of the ice at the end of the last ice age the sea invaded the low lands and river mouths Ex: Chesapeake Bay, mouths of Delaware, St.Lawrence Rivers, mouth of River Thames in England

anadromous fish v.s. catadromous fish examples in estuaries

anadromous: marine fish that migrate to fresh water to breed -salmon, smelts, shad catadromous:freshwater fishes that migrate to the sea to breed -freshwater eels

Why do mangroves show a idstinctive zonation in the intertidal?

as a result of different tolerances to immersion by high tide marine->terrestrial environment

Why would the deep water in a fjord become depleted in oxygen

bacterial respiration associarted with the decompostion of organic matter that sinks and accumulates on the bottom

What types of primary producers are common during the warmer months on mudflats?

benthic diatoms cgrow on the mud and undergo extensive blooms->golden-brown patches in tide pools, patches become coated w/ oxygen bubbles b/c of photosynthesis

How are estuaries advantageous for birds?

birds congregate at low tide to feed at estuaries important stopover and wintering area for many migratory birds open spaces offer safety from natural enemies, food is plentiful

black mangroves v.s. white mangroves

black:seedlings can survive the high salinity of the water after high tide flooding, grows higher in intertidal than red. excrete salt white: does not tolerate flooding by seawater, found only along landward edge of mangrove forest. leaves have 2 visible salt glands

What types of organisms live in salt marshes?

burrowing animals, nematodes, small crustaceans, larvae of land insects, small invertebrates live in algal mats and decaying marsh plants fiddler crabs build burrows in mudflat edges-increase the oxygenation of soil

What types of animals make up the majority on mudflats?

burrowing deposit and suspension feeders that feed on detritus

How can the particulate material in the water of an estuary harm organisms?

can clog the feeding surfaces o some filter feeders kill organisms- sponges-sensitive to sediment

How do plants in salt marshes rovide shelter and food to many marine and land animals?

coffee bean snails and marsh periwinkles feed on detritus, minute algae, fungi that grows on marsh plants, move up with high tide lay their eggs in the water and the larvae hatched develop in plankton ribbed/horse mussel is a suspension feeder that lives half buried in mud among gcordgrass kilifishes inhabit tidal creeks and pools in the marsh at low tide. move into salt-marsh grass at high to escape predators(crabs)

Name different adaptations that have evoled in some estuarine plants to handle salinity variations

cordgrasses, salt-marsh plants, some mangroves excrete excess salts by the salt glands in their leaves pickle weed accumulate large amounts of water to dilute the salts they take up

What is the most common type of plant along the seaward limit of the salt marsh?

cordgrasses. occupy the fringe above the mean low-tide level b.c the soil is well drained and richer in oxygen, less salty leaves exposed to air even if bottom is covered at high tide plants have extensive horizontal stems that stretch out underground leaves and roots develop from the stems. roots below soil take in O from air

what types of marine and land animals live in mangrove forests?

crabs-feed on abundant leaf litter fiddler excavate burrows in mud. burrowing crabs help oxygenate sediment mudskippers have burrows in mud but skip over mud and crawl up mangrove roots for food

What does bacteria do on mudflats?

decompose the huge amounts of organic matter brought in by rivers and tides when O is used up by decay, some produce H2S

How do cordgrass help stabilize soils?

decrease the effects of wave action

What do low tides on mudflats expose organisms to that are similar to those on muddy shores?

desiccation, wide variations in temperature, predation

What are the four types of estuaries?

drowned river valleys, bar-bult, tectonic, and fjords

salt/tidal marshes

extensive grassy areas that extend inland from mudflats that are partially flooded at high tide

T/F: Mudflats are especially extensive in estuaries where there is a SMALL tidal range and a gently sloping bottom

false mudflats are especially extensive in estuaries where there is a LARGE tidal range

What are some examples of bivalves on mudflats

filter feeders quahog-hard clam, soft-shelled clam, razor clams bent-nosed,small clams are deposit eeders that use their long incurrent siphons to vacuum the surface

How do polychaetes feed on detritus in mudflats as suspension feeders?

filter water or extrude tentacles to collect the detritus that falls from the water column switch back and forth between suspension and deposit eeding, depending on the amount of suspended material in water

Succulents

fleshy plants that accumulate large amounts of water to dilute the salts they take up

Mangroves

flowering land plants adapted to live in the intertidal

How do estuarine plants handle salinity variations?

grasses/salt marsh plants acively absorb salts and concentrate harmless solutes to match the outside concentrations and prevent water from leaving their tissues

negative estuaries

high-salinity estuaries in regions of little freshwater runoff and high evaporation Ex: Laguna Madre

What toxic chemical accumulates in anoxic sediments?

hydrogen sulfide

On what type of margin are broad, well-developed estuaries more likely to be found?

in passive margins- regons with flat coastal plains and wide continental shelves

Where does respiration by decay bacteria use up oxygen?

in the intersitial water- the water between sediment particles

infuana v.s. epifuana

infauna: animals that burrow in the substrate epifuana: animals that either live on the sediment surface or are attatched to a surface as sessile forms

meiofauna

intersitial fauna microscopic animals that lie on the bottom Ex: protozoans, nematodes

How does bacteria play a crucial role in muddy salt-marsh substrate?

it deomposes the large amounts of dead plant material produced in the salt marsh. bacteria and broken down organic matter are a major source of the detritus that feeds on many estuary inhabitants some bacteria are nitrogen fixers

How do osmoregulators cope with salinity fluctuations in estuaries?

keep salt concentration of their body fludis ore or less constant regardless of water salinity Ex: fishes, crabs, molluscs, polychaetes

How are tectonic estuaries formed?

land subsided as the result of movements of the crust Ex: san Fran Bay

Why is water clarity reduced in estuaries?

large amounts of suspended sediments are typical of estuaries very little light penetrates the water column

What types of organisms take shelter among submerged mangrove roots?

large sponges provide nitrogen for mangrove plants and help protect the roots from burrowing isopods birds live in branches nad feed on fishes, crabs. snakes frongs lizards bats live in trees

How do fiddler crabs live on mudflats?

live in burrows but are active on mudflats at lwo tide they process the mud and extract the detritus for food

What do ghost and mud shrimps do in mud flats that is significant?

make elaborate burrows that help oygenate the sediment feed on detritus that they filter from the water and sift from the mud

mangals

mangrove forests formed by mangroves, tropical and subtropical trees and shrubs adapted to the intertidal environment

Why are estuaries comercially important?

many species like fish and shrimp use estuaries oas nurseries for their young, taking advantage of abundant food and safety from predators

What are disadvantages of living in the mud?

most animals burrow/live in permanent tubes beneath sediment surface Many organisms are slow moving

Why is the red mangrove of the atlantic and eastern Pacific mangrove forests of great ecological significance?

most commmon species of mangrove on the shores of southern Florida, the Caribbean, the gulfs of California and Mexico lives right on shore, easily identified by peculiar prop roots branch downward and support the stilts flexible aerial roots drop from higher branches

What type of animals live on the surface of the mud or move in an out with the tide?

mud snails, amphipods, shrimps. Carnivores: polychaete worms, moon snails, swimming crabs

Why is the muddy bottom of salt marshes more stable than that of mudflats?

muddy bottom is held together by the roots of marsh plants

What do shorebirds feed on?

polychaetes, ghost shrimps, small crustaceans, clams, mudsnails

What restrictions does murky water in open water estuaries present?

restricts the penetration of light limits primary production

How are fjords formed?

retreating glaciers cut deep valleys along the coast which were partially submerged when sea level rose and now rivers flow ex: SE Alaska, British COlumbia, Norway, SW Chile

How do mangroves get rid of salts?

salt glands on the leavs excrete salts instead of being taken in by the roots

wetlands

salt marshes flooded at high tide and freshwater marshes collectively

What types of plants are salt-marsh communities dominated by?

salt-toelerant land plants such as hardy rasses thrive in the marsh but marsh is too harsh for other land plants pronounced zonation of plants in salt marshes

What is the substrate of most estuaries?

sand or soft mud coarse materials settle out in the upper estuary where river current slows

What does the fat inkeeper worm do on mudflats?

secretes a funnel shaped net of mucus, pumps water thru it to filter out food shares its U-shaped burrow w/ a polychate, crab, one more fish, etc.

Estuaries

semi-enclosed areas where freshwater and seawater meet and mix

What tool do fjords have that restricts water circulation?

shallow sill prevents sewater from flowing in along the bottom after low-salinity water flows out on the surface

How does the zonation of a salt marsh affect the soil salinity?

soil salinity may become high at intermediate heights as a result of higher evaporation in marshes closer to hot, dry regions. result in areas bare of vegetation

What special adaptations do burrowers have to low low-oxygen environments?

some have blood that contains hemoglobin- can hold and carry O2 w/ limited available quantity

What do herons and egrets specialize in?

specialize in catching fishes, shrimps, small swimming prey Ducks, terns, gulls rest on mudflats

What are euryhaline species?

species that can tolerate a wide range of salinities

What are stenohaline species?

species that tolerate only a narrow range of salinities-can be either marine or ffreshwater limited to the upper or lower ends of estuary and rarely penetrate properly

How is most salt marsh zonation determined?

the effects of flooding by tides competition for space among salt-marsh plants increased soil salinity in warm areas due to evaporation effect of burrowing animals

What influences the distribution of salinity in estuaries?

the shape of the estuary and its bottom, the wind, evaporation of water from the surface, changes in the tide seasonal variations oin freshwater runoff from rivers as result of rainfall patterns

Why do suspension feeders dominate on sandy sediment?

the wider intersitial spaces between the larger sand particles hold less detritus for deposit feeders to eat, and the abrasive sand is hard on their digestive systems

Why are suspension feeders at a disadvantage on mudflats?

their filtering mechanisms tend to get clogged by the high amounts of sediment that rains on soft bottoms deposit feeders exclude many suspension feeders by disturbing the sediments, which clogs the suspension feeders' feeding structures and buries their newly settled larvae

Why are tidal currents important in estuaries

tide rushes in creating strong tidal currents b.c long and narrow affects pattern of salinity

pneumatophores

unbranched extension sof the shallow roots of mangroves that grow upward from the oxygen poor mud to help aerate the plant tissues and obtain oxygen in mangroves

How do shorebirds use resource partioning for feeding habits?

varying lengths of bill represent specialization in prey b/c of depth in mud use diff strategies to locate food sandpipers-bills probe thru mud plovers use eyesight to detect movement in mud

tidal bores

vertical wall of water that effects the pattern of salinity

Who are the most significant predators on mudflats?

waddling shorebirds ex: willet, godwits, dowitchers,plovers,sandpipers

Why are the sediments in estuaries anoxic?

water cannot easily flow through the fine sediment to replenish the oxygen supply

what is brackish water?

water of intermediate salinity

How are mudflats formed?

when the bottoms of estuaries become exposed at low tide form mudflats

How and for what purpose do osmoregulators use active transport?

when the salinity of the water is lower than that of the blood use active transport to get rid of excess water they absorb some solutes from the surrounding water to compensate for those lost in the elimination of water using the gills, kidneys, etc. Ex: salmon and freshwater eels