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216 Cards in this Set

  • Front
  • Back
Why is the definition of the coastal zone a bit fuzzy?
Weather and seasonal changes affect how far coastal influence extends.
What are the common boundaries for the coastal zone?
the coastline and the continental shelf break
What percent of the total ocean area are the continental shelf and the coastal zone?
8% and 10%
Why is the coastal zone important to humans?
99% of the total world fishery catch is in it.
How are coastal zones different from the open ocean?
Salinity and temperature are more variable; currents are independent of gyres; the mixed layer has more nutrients, and benthic organisms are more diverse.
What does river discharge do to the salinity of coastal waters?
A halocline develops a few meters deep.
What determines the extent of a coastal shallow halocline?
the river's flow rate and the vertical mixing within the water column
What is the major consequence of shallow coastal haloclines?
Upwelling and vertical mixing are inhibited.
Why are residence times for coastal water generally high?
Coastal currents go parallel to the coastline, and a front (barrier) blocks the mixing of open-ocean water and coastal water.
How can the residence time of freshwater input from a river into the coastal zone be calculated?
from the volume input, the total coastal volume, and the average salinity
Why is it important to know the residence time of coastal water?
to calculate how much pollutants will build up
How does the salinity of coastal waters vary seasonally?
For the tropics, salinity is lowest in the rainy season, and at high latitudes, salinity is lowest in late spring or summer because of the snowmelt.
Where do salinity extremes occur?
in marginal seas, lagoons, or other bays
What happens in high-salinity coastal areas?
The mixed layer is deep because of the increased density and often extends to the seafloor, which mixes nutrients, increasing productivity.
What forms the top layer of high-salinity coastal areas?
Some parts have cold, low-salinity open ocean water on top while others have warm, high-salinity local water on top.
Where, in general, is coastal salinity low?
where river output is large and evaporation is low
Where specifically is coastal salinity low?
fjords, the Baltic Sea, and the Bay of Bengal
Where specifically is coastal salinity high?
the Mediterranean and Red Seas
Which coastal regions experience the most seasonal fluctuation?
those with limited exchange with the open ocean
How does temperature vary in high-latitude coastal waters?
It doesn't vary much, with sea ice melting and freezing, so the temperature is constantly -2°C.
How does temperature vary in tropical coastal waters?
It's always warm, and isothermal to the seafloor especially in shallow lagoons.
How does temperature vary in mid-latitude coastal waters?
In summer, a shallow thermocline forms at ~15 meters deep. In winter, this goes away due to lower solar heating and greater mixing.
How do tides enhance vertical mixing?
As they ebb and flood, they create turbulence.
What waves can enhance vertical mixing?
tidal waves, Langmuir circulation, and internal waves
What can photosynthesize in the benthic zone of shallow coastal waters?
kelp, macroalgae, and microalgae
What dominate the photosynthesis in the benthic zone of shallow coastal waters?
microalage that encrust rocks, dead coral, and other organisms
What makes the photic zone shallower and more variable in coastal waters?
Turbidity is often higher but depends on the proximity to a river, the direction of coastal currents, and the wave intensity.
Why does it matter that the photic zone of coastal waters varies widely in depth?
Benthic algae populations vary accordingly, and coral are limited by access to light.
What do coastal currents depend on?
weather and the shape of the coastline
Why are coastal waters so much more productive than the open ocean?
Nutrients are supplied by rivers or coastal upwelling and are not lost to the deep ocean.
How do nutrients supplied by a river distribute themselves?
along the coast, only slowly mixing with deep waters
Which way does Ekman transport push surface water during wind-driven coastal upwelling?
offshore, away from the coast
What must be true for coastal upwelling to increase primary productivity?
Photosynthesis at that location must be nutrient-limited, not light-limited, and the upwelling must draw from water that is high in nutrients from below the permanent thermocline.
Why is coastal upwelling more prominent in the western coasts of continents than the eastern?
because western boundary currents jam up against the coast, preventing upwelling from deep waters
What happens if river output and offshore Ekman transport are combined?
A wide, low-salinity surface layer can extend from the mouth of the river and hinder upwelling.
Why is coastal upwelling dependent on weather?
Ekman transport takes steady winds to establish, and therefore depends on local winds, which vary with weather.
Where around the world is coastal upwelling the most common?
in the trade wind regions
How can coastal upwelling change seasonally?
If climactic winds vary seasonally, such as in California, upwelling can vary seasonally.
Why is coastal upwelling stronger near capes?
It's not entirely clear, but it appears to involve the coastal currents and eddies and the topographic ridge that extends from capes.
Why doesn't phytoplankton growth begin right away in newly upwelled water?
Few phytoplankton cells exist in the water; micronutrients might be lacking; trace metals may be toxic or unavailable.
What effect does chelation have on the toxicity or biological availability of a metal ion? Why is this useful?
Toxicity decreases and availability increases. This lets us determine that metal ions play a role in the time lag after water is newly upwelled.
What species are the first to grow in newly upwelled water?
small flagellate phytoplankton
What do flagellate phytoplankton do that lets other species emerge?
They release some organic compounds that include chelating agents and micronutrients.
What happens to the phytoplankton biomass as coastally upwelled water travels offshore on the surface?
Diatoms and others bloom (biomass 100X offshore), depleting nutrients and then being eaten later.
How are zooplankton and nekton populations distributed in coastal upwelling ecosystems?
where there's food, so bigger fish are more offshore and not much lives in the newly upwelled water
Why do coastal upwelling fisheries use photosynthetically-produced organic matter more efficiently than open-ocean fisheries?
The food chains are shorter, because everything is in one small area.
How do coastal upwelling zones recycle nutrients?
Fecal pellets and detritus go from the surface to the soon-to-be-upwelled water.
How do plankton take advantage of coastal upwelling circulation?
They release spores, cysts or eggs as they are transported offshore, which sink into the soon-to-be-upwelled water and revive or hatch when this water is brought to the surface.
In coastal upwelling, what region has the highest primary productivity?
the mixing region
In coastal upwelling what regions have low primary productivity?
the upwelling region and the offshore region
How do nekton take advantage of coastal upwelling circulation?
They distribute eggs and larvae so they hatch when they are upwelled and can feed on the biomass in the mixing region, sometimes changing forms to take full advantage of the food options.
How are coastal upwelling zone species helped or harmed by changes in the upwelling?
Some time their life cycles so they depend on the upwelling for the next generation, and their population drops dramatically if it doesn't.
Besides coastal upwelling and river runoff, what can supply nutrients to the coastal photic zone?
storm waves, seasons, internal waves, tides, seafloor topography, convective downwelling, and eddies
How can waves supply nutrients to a coastal area?
During summer or fall, the seasonal thermocline can be disrupted by large waves from intense storms.
How can a change in seasons supply nutrients to a coastal area?
Shallow areas accumulate detritus on the seafloor, which decomposes into nutrients. When winter comes around, the thermocline goes away, and the nutrients are brought to the surface.
How can internal waves supply nutrients to a coastal area?
When they break on the continental shelf, they can mix some deep water into the coastal mixed zone.
How can tides supply nutrients to a coastal area?
They can in some areas generate swift currents that prevent a seasonal thermocline from forming.
How can seafloor topography supply nutrients to a coastal area?
Deep currents can be forced upwards by seamounts, ridges, plateaus or islands and mix with islands' coastal waters.
How can downwelling of water actually supply nutrients to the surface?
If it is persistent enough, it can break the thermocline. Then, when it is downwelled, deep water must be upwelled to take its place.
Where do convective (heat) motions increase the productivity of the surface waters?
in high-latitude waters, where cooling produces denser water that downwells and the thermocline is almost always absent
How can eddies supply nutrients to coastal waters?
At Georges Bank (a shoal, the seafloor is quite shallow) outside the Gulf of Maine, water flowing out of the gulf is deflected and circles the bank, supplying nutrients but not sweeping plankton away from the bank.
At which latitudes are the seasons significant?
middle and high
What temperature profile does the high-latitude water column exhibit?
It's isothermal and well-mixed.
Why don't high-latitude areas develop a thermocline?
Solar heating is limited, frequent storms mix the water, and surface cooling makes denser water that sinks.
Why do seasonal blooms in subpolar regions far from land last the entire season?
They remain light-limited, not nutrient-limited.
How do blooms fare in polar and subpolar regions with substantial freshwater input?
A halocline develops that limits vertical movement and makes blooms die when they run out of nutrients.
How do subpolar freshwater inputs limit primary productivity?
They often have high turbidity and create a pycnocline that cannot be crossed by upwelling.
What is required for the freshwater halocline of subpolar regions to be broken down?
strong, frequent storms
Why are Arctic waters nutrient-limited rather than light-limited during the summer?
The halocline produced from salt exclusion and the vast melting freshwater is persistent, mixing with other oceans is rare, there are few storms near the high-pressure pole, and any such storms have a limited fetch.
Why do Antarctic waters not develop the halocline of Arctic waters?
Antarctica melts only slightly, being a desert.
Why are Antarctic waters more productive than Arctic and North Pacific and Atlantic waters?
No permant halocline develops, so vertical mixing restores nutrients and keeps the populations alive.
Why are tropical waters low in primary productivity?
Nutrients are lost through the steep permanent thermocline and out of the photic zone.
What are the only tropical waters with lots of life?
coral reef communities
How is the mutualistic symbiosis between reef-building polyps important for the development of the coral reef community?
Somehow it allows the zooxanthellae to utilize small concentrations of nutrients, providing a base for the food chain. Also, they can exchange nutrients between each other, rapidly recycling the nutrients.
What are coral reefs made of?
the hard parts of coral animals or polyps
What happens to mid-latitude surface waters when winter comes?
The seasonal thermocline is eliminated, and the mixed zone mixes, moving phytoplankton in and out of the shallow photic zone. Phytoplankton are light-limited.
What happens to mid-latitude surface waters when spring comes?
The photic zone deepens and a seasonal thermocline starts to form, moving phytoplankton to the photic zone where they grow and reproduce rapidly.
What happens to the zooplankton population after a spring bloom in mid-latitude surface waters?
They also grow and eat the phytoplankton, so only a small fraction of the phytoplankton standing stock lasts at one time.
What happens to mid-latitude surface waters when summer comes?
Nutrients are depleted and the mixed layer becomes shallower, making the phytoplankton now nutrient-limited rather than light-limited. Primary productivity decreases as nutrients sink out of the mixed layer.
What happens to mid-latitude surface waters when fall comes?
Storms start to break up the thermocline, providing nutrients for a fall bloom.
How do fall blooms and spring blooms compare?
Fall blooms are smaller, shorter and more variable, sometimes not happening.
What must occur for a fall bloom to happen?
Nutrients must be mixed in before light intensity decreases too much, and the mixed layer cannot be too mixed, moving phytoplankton out of the photic zone.
What details can affect what types of blooms occur each year in mid-latitudes?
plankton population composition and silicate concentrations
What types of zooplankton are involved in most coastal food chains that produce desirable fish and shellfish?
large zooplankton, because they reduce the length of the food chain, making it more efficient
What is species succession?
how dominant species replace each other
What factors affect species composition and succession?
temperature, salinity, light intensity, and nutrient concentration
What organisms dominate when nutrient levels are high?
larger phytoplankton, specifically diatoms
What organisms dominate when nutrient levels are low?
smaller phytoplankton, specifically flagellates
How do zooplankton and fishes take advantage of phytoplankton succession?
They time their life cycles annually or biannually so their eggs can feed on diatoms and then on zooplankton after the bloom ends.
What is "year class strength"?
the number of juvenile fishes that survive their first year
What is year class strength dependent on?
the timing of blooms and spawning
Why can diatoms specifically be replaced by other phytoplankton?
They require silica, which does not recycle quickly, so when it runs out, they die.
What would happen if nitrogen and phosphorus nutrient levels were raised without silicate being raised as well?
The diatom bloom would die quickly, and the flagellate bloom would be tremendous, as in red tides.
What can raise nitrogen and phosphorus nutrient levels without raising silicate levels as well?
human sewage wastes discharged into the oceans
What is happening to dinoflagellate blooms recently?
Their frequency has been increasing.
How can a large freshwater runoff increase cause dinoflagellate blooms?
It can form a shallow surface layer with substances that react with toxic copper and mercury that normally limit flagellate levels.
How can sewage release cause dinoflagellate blooms?
It has high nitrogen and phosphorus nutrient concentrations as opposed to silicate concentrations.
How can cyanobacteria cause dinoflagellate blooms?
They fix nitrogen, making it available, but not in very high quantities, for flagellates to utilize.
How fast can dinoflagellates reproduce?
Their population can double in a few hours.
How can dinoflagellates concentrate themselves into blooms?
by using their flagella to move to the optimal depth
What colors do dinoflagellate blooms exhibit?
yellow, green or brown, but mainly red (red tides)
How can dinoflagellate blooms cause harm?
They can synthesize toxic substances or their dead bodies can deplete the oxygen.
List four toxins produced by dinoflagellates.
saxitoxin, brevetoxin, okadaic acid, and domoic acid
How do dinoflagellate toxins vary?
They are often mixtures of compounds. Some target vertebrates, while others also affect invertebrates.
What effects can dinoflagellate toxins have on fish and humans?
They kill fish, and filter-feeders like shellfish that are not intoxicated concentrate the toxins in their tissues, which poses problems for vertebrates like humans that eat them.
What are the four major human pathologies caused by shellfish-borne toxins?
paralytic, neurotoxic, diarrhetic and amnesic shellfish poisoning (PSP, NSP, DSP, and ASP)
What does PSP do?
causes permanent nerve injuries, paralysis or death
How many cases of PSP are reported annually?
1600 cases, 300 of them mortalities
What does NSP do?
produces symptoms similar to those of bacterial food poisoning, and thus is often misdiagnosed
What does DSP do?
causes severe diarrhea
What does ASP do?
destroys short-term memory, perhaps permanently
How can dinoflagellate toxins be dealt with?
by preventing infected shellfish from reaching the marketplace with expensive monitoring programs or simply closing areas where blooms occur predictably
What toxin have diatoms produced?
domoic acid
What does a recent hypothesis label as the cause of toxin production in phytoplankton?
viruses living in the phytoplankton cells
Besides fish, what vertebrates have been poisoned by phytoplankton toxins?
humans, pelicans, and bottlenose dolphins
What two processes decrease the oxygen concentration below the thermocline?
respiration and decomposition of detritus
Why is the reduction in oxygen concentration below a seasonal thermocline smaller than that below a permanent thermocline?
The seasonal thermocline doesn't last long enough for oxygen to be depleted over time, and summer, when the thermocline is strongest, is not the best season for primary productivity.
Does oxygen tend to get depleted below areas with high primary productivity?
rarely, because these areas usually have upwelling that prevents the steep thermocline from forming, and the oxygen-deficient water is continuously transported to the surface.
What is cumulative oxygen demand?
the total amount of oxygen consumed before the water mass recontacts the atmosphere or mixes with other water
What circumstances produce a high cumulative oxygen demand?
high overlying productivity and long residence time below the thermocline
What are hypoxia and anoxia?
low oxygen concentration and no oxygen, respectively
How long are residence times of water below seasonal and permanent thermoclines?
months and years to decades, respectively
Where are residence times for water below permanent thermoclines longest?
marginal seas, ocean inlets, and bays
Where is anoxia most apt to develop?
in marginal seas with long deep water residence times
Where has anoxia been present for the past 100 years or more?
Norwegian and other fjords and the Baltic Sea
What has happened to anoxic bottom waters recently?
More nutrients and anthropogenic oxygen-demanding compounds have spread the areas of anoxia.
In general, what happens when hypoxia and anoxia set in?
Many animal species cannot survive in hypoxia for long, and none can survive in anoxia.
How can phytoplankton blooms produce hypoxia or anoxia?
When they occur, they produce a lot of detritus that depletes oxygen.
What are three of the world's marginal seas where periodic massive algal blooms cause hypoxia or anoxia?
the Adriatic Sea and Saronikos Gulf in Greece, and the Sea of Japan
What are three US coastlines that have been harmed by hypoxia or anoxia?
the Gulf of Mexico, Chesapeake Bay, and the Oregon coast
What is eutrophication?
another name for hypoxia and/or anoxia
What determines fish abundance?
primary productivity
List open-ocean, coastal and upwelling regions from most abundant in fish to least abundant in fish.
upwelling, coastal, open-ocean
Between open-ocean, coastal and upwelling regions, where is the highest average trophic efficiency?
upwelling, coastal, open-ocean
Give the percentages of area and world fish catch for the open-ocean, coastal and upwelling regions.
Open ocean: 90% area, <1% fish
Coastal: 10% area, 50% fish
Upwelling: .1% area, 50% fish
What three fisheries are the most successful, and what do they share in common? Also, what percentage of the global catch do they constitute?
Herring, anchovy and sardine fisheries (in upwelling zones) draw from zooplankton at the second trophic level, very efficient and abundant, 25% of the global catch.
What percentage of the global fishery catch is used for animal food rather than people food?
40%
What would be the main harm done if the world fishery catch were increased substantially above present levels?
Higher carnivores like big fishes, mammals, and seabirds, would die off as the fish populations do.
At what capacity are many major fisheries in coastal and upwelling zones?
maximum sustainable yield, and many are even overfished
What difficulties do fish face that make their numbers vary substantially from year to year?
Larvae can only eat certain sizes of plankton and compete with others while juveniles have to worry about predation, disease, parasitism and pollution.
How has fish population prediction fared?
It takes a lot of studies to establish trends for just one species; plus, numbers might be inherently chaotic.
What are estuaries?
regions where freshwater and seawater mix
What are the boundaries of estuaries?
on the landward side, the limit of saltwater movement, and on the seaward side, where dilution becomes unnoticeable
Where are estuaries found?
at the mouths of major rivers and semi-enclosed inlets into which rivers flow
Why are estuaries important?
Most major cities are built on estuaries, and many fish and invertebrate life cycles involve both the ocean and a river or estuary
What are seven properties that define estuaries?
length, width, depth, tidal range, freshwater flow rate, shape, and coastal character
What are the two ways to classify estuaries?
by their geologic origins and by their water circulation and mixing characteristics
How much did sea level rise from the low point when?
130 meters since 18000 years ago
What happens to estuaries if sea level does not change?
They fill with sediment and a delta forms.
When in geologic history have estuaries existed?
only when sea level is rising or has recently risen
What are the types of estuaries classified by geologic origin?
coastal-plain estuaries, bar-built estuaries, tectonic estuaries and fjords
How did coastal-plain estuaries form?
as sea level rose into river valleys
What type of estuaries are drowned river valleys examples of?
coastal-plain estuaries
What are examples of coastal-plain estuaries in the US?
Chesapeake Bay, Delaware Bay, and New York Harbor
What type of estuary did the Mississippi River Delta used to be?
a coastal-plain estuary
How did bar-built estuaries form?
A sandbar is extended parallel to shore by longshore drift, separating the ocean and a shallow lagoon.
What are examples of bar-built estuaries in the US?
Albemarle Sound and Pamlico Sound in North Carolina
What type of estuary is the Hudson River estuary?
mainly a drowned river valley, but it also has a spit that makes it similar to bar-built estuaries
How did tectonic estuaries form?
A section of land moves along a fault and as a result is lowered below sea level.
What faults can create tectonic estuaries?
subduction zones or transform faults
What is an example of a tectonic estuary in the US?
San Fransisco Bay
How did fjords form?
They were cut by glaciers and simply filled with water when sea level rose.
What are three characteristics of fjords?
steep-sided, deep, and often have a sill at the mouth from the glacier's moraine
What are examples of fjords around the world?
Norway, SW New Zealand, and the Pacific coast of Canada
What are examples of fjords in the US?
southern Alaska and Puget Sound in Washington state
What are six or seven factors that affect the movement of water in an estuary?
tidal currents, wind-driven wave mixing, shape and depth of the estuary, flow rate, friction, and the Coriolis effect
Why is estuarine circulation important?
Major cities discharge lots of waste... where does it go?
What are four ways man can alter the circulation of estuaries?
by buiding piers or other port structures, dredging, filling in wetlands, and building levees or other coastal structures
What are the types of estuaries classified by circulation?
salt wedge estuaries, partially mixed estuaries, well-mixed estuaries, and fjords
How is a salt wedge estuary structured?
Freshwater flows over the top, so the salt water forms a wedge with a steep halocline in between.
How do salt wedge estuaries mix?
Friction at the halocline creates internal waves that mix when they break.
What are the ingredients for salt wedge estuaries?
large freshwater input, deep, narrow, small tidal range and limited winds, so that mixing is minimal
What is the main difference between partially mixed estuaries and salt wedge estuaries?
Vertical mixing is more prevalent in partially mixed estuaries than in salt wedge estuaries.
What are the ingredients for partially mixed estuaries?
tidal currents are fast, river flow is moderate, and the speeds are comparable
What is tidal excursion?
the distance water moves in an estuary with each tide
What are residual currents in estuarine circulation?
the net movement of water in an estuary, once the tides have been averaged out
How do residual currents and tidal excursion compare in partially mixed estuaries?
Residual currents are much smaller and therefore harder to measure.
What role does the Coriolis effect play in salt wedge and partially mixed estuaries?
In the Northern Hemisphere, from sea, it makes the halocline slope up and to the right.
How is a partially mixed estuary structured?
similar to a salt wedge estuary, but with a weaker halocline
How is a well-mixed estuary structured?
strong mixing, so the water column is homogenous and there is no halocline; salinity varies horizontally
How do tides affect well-mixed estuaries?
Tides mix them, and change the horizontal position of the vertical halocline.
What role does the Coriolis effect play in well-mixed estuaries?
It rotates the vertical halocline CCW in the Northern Hemisphere and clockwise in the Southern Hemisphere.
What are the ingredients for well-mixed estuaries?
wide, shallow, limited freshwater and strong tidal currents
What distinguishes fjords from the rest based on circulation?
They are so deep that bottom waters are not affected by tidal currents.
What role does a fjord's sill play in fjord circulation?
It prevents exchange of deep water, so the bottom water in a fjord just stays there. Also, turbulence around it enhances mixing at that depth.
What do fjords behave like above their sills?
salt wedge or partially mixed estuaries, only rarely well-mixed
What can displace fjord bottom water?
saline water flowing over the sill when random stuff happens (it's not predictable)
What happens if fjord bottom water is displaced?
H2S that has built up will kill lots of fish.
What are the ingredients for inverse estuaries?
shallow in arid regions with lots of evaporation
How are inverse estuaries structured?
Circulation is backwards: Seawater goes on top of estuarine water.
What are several examples of salt wedge estuaries?
the Red Sea, San Diego Bay, Laguna Madre, and even the Mediterranean Sea
How do estuarine currents compare to the river freshwater input?
They are many times greater, because they go in both directions.
What is the fate of large particles carried by rivers dumping into estuaries?
Usually, they are deposited before the river reaches the estuary.
What is the fate of medium-sized particles carried by rivers dumping into estuaries?
In well-mixed estuaries, they are deposited on one side, and in other estuaries, they cycle until they are eventually deposited in a shoal at the furthest point seawater gets landward. But if the tides mix them up, these particles eventually are deposited in wetlands.
How can particles from outside an estuary in the ocean be deposited within the estuary?
if the tidal currents are strong enough to resuspend them
What is the fate of small particles introduced to an estuary on the surface?
They are transported to the oceans.
What is the fate of small particles introduced to an estuary at depth?
They are moved landward and deposited rather than entering the cycle.
What is important about particles introduced to estuarine circulation?
They most often are not simply flushed out to sea; they cycle around and around in the estuary before finally settling. This matters for toxins in sewage.
What has gone wrong at San Francisco Bay?
Dredged sediments were put on the wrong side of the bay, where they were flushed back into the bay from which they were dredged.
What makes estuaries hard to live in (for organisms)?
rapid changes and the salinity variation, which means osmotic pressure variation
Why do estuaries tend to have a very high biomass?
There is plenty of nutrients and sunlight; it's just hard to live there, so not much variation appears.
What primary producers dominate most estuaries?
benthic microalgae like diatoms that mat the sediments
What primary producers are found in and around estuaries?
microalgae and macroalgae on the seafloor, and plants in nearby salt marshes and mangrove forests
Why are phytoplankton not very prevalent in estuaries?
They are swept seaward with the surface layer flow.
Why are estuaries high in nutrients?
They obtain many nutrients from the river, and sinking nutrients are retained by the circulation.
What is required for an estuary to develop a multi-level food chain analogous to that of coastal upwelling?
flow is slow or the estuary is long
Why do animal larvae and juveniles thrive in estuaries?
There are many hiding places from predators and in general, there are fewer predators.
What fraction of fish on the SE US coast use estuarine wetlands as nurseries or to breed?
half
What are anadromous fishes?
those that live their lives in the ocean but go to freshwater to spawn
What are two examples of anadromous fishes?
the salmon and striped bass
Describe the order of habitats for an anadromous fish.
born in freshwater, migrate to the estuary, live in the sea, come back to freshwater to spawn, and die
What are catadromous fishes?
those that live their lives in freshwater but go to the ocean to spawn
What is an example of a catadromous fish?
freshwater eels
Describe the order of habitats for a catadromous fish.
born in the ocean, migrate to the estuary (using currents), migrate up the river, live in freshwater, come back to the sea to spawn, and die
Where in the oceans do freshwater eels spawn?
in the Sargasso Sea and an equivalent area in the North Pacific
What role does the estuary play in anadromous and catadromous fishes?
It serves as the place where they adjust to saltwater or freshwater.