3
Homework-Answer this question and email it to biovcc@Gmail.com
HW 3 There are marked differences in the type of organisms
found at four different locations at the same tidal height along ta rocky shore.
What might account for this? Mention 3 possible explanations.
Beaches and Rocky Shores
The beach is a region between the high
and low waterlines that is covered by sand or some other unconsolidated
material.
Turbulent waves along the shore usually
remove mud from the beaches and hold it in suspension.
As the fine particles of mud are
transported to deeper or less turbulent water, they settle on the bottom.
A beach is described in terms of the
average size of its sand particles, the range and distribution of these
particles, the elevation and width of the berm,
the
slope of the foreshore and the slope of the inshore.
Waves are primarily responsible for
moving sand away from river mouths and along the coast.
Beaches
As a wave breaks, the sudden release of
energy within a small area causes turbulence that dislodges sand particles.
Beaches
Waves
approach the coast from almost any angle and if it comes in from the north say,
then the water runs back to the sea in a southernly
direction.
This forms
what is known as the longshore current or littoral
drift. This current provides longshore transport that carries sand along the shore.
Beach sand is always in transit from one place to another
Beaches
Size and
power of waves affect the rates of longshore
transport.
On the east
and west coast, LST runs in one direction usually, and that is south because
most waves come from northern storms.
Sand is
transported south at a rate of 150,000 to 1,600,000 m3/yr.
Beaches
Human
activities have had both beneficial and harmful effects on the coastline.
Some
activities include damming of rivers, land recovery programmers, dredging of
inlets, development of dune areas and construction of erosion control
structures.
Beaches
Erosion
Control Structures
Jetties built
to prevent longshore currents from filling inlets or
to bring about the deposition of sediments benefit the property immediately upcurrent but may cause the downcurrent
shoreline to recede.
Beaches
Groins, small
piles of rocks at right angles to the beach transform the longshore
current into a zig zag
current that destroys the linear form of the coast..
Beaches
When the
first groin or jetty was constructed, it was observed to collect the sand on
the upcurrent side of the jetty.
This became a
way to enlarge an otherwise eroding beach!
The removal
of beach sediment is erosion and addition of material is deposition.
Beaches
Unfortunately,
the jetty was interrupting the longshore current
carrying the sand and while erosion was still occurring downcurrent,
no more sand was being deposited so downcurrent to
the jetty started to erode.
Solution?build
another jetty..and thats
what they did
Beaches
Tides produce
short-term fluctuations along coastlines but sea level changes are long-term..and there lies the problem.
Beaches
To counter
the erosion of the beaches and coastline due to sea-level rise, jetties were
built along the coasts to stabilize the beaches.
Beaches
From dumping
loads of sand along the beach to pumping sand back in from the ocean, billion$
of dollar$ have and will be spent trying to rebuild our beaches.
In Ocean
City, NJ, attempts were made to pump sand in from the ocean.
Beaches
This time, beaches were rebuild taking size of sand grains, and replacing enough
sand so it just wouldnt drop offshore.
Beaches
1st Picture
Looking south from the last picture..
1st Picture
1st Picture
To try and stablize the beaches, fences were placed in the upper part of
the beach to collect the sand from the beach when the wind blows. Dune grass was planted to stabilize the
sand
and in turn collects sand as it moves across the dune and keeps growing..
Dunes are a
mobile physical medium and ecological environment,
frontal dunes are part of sediment exchange.
They can
migrate inland or seaward and should be allowed to move
and do
The next
pictures are the DUNES built along the newly built beaches.
Next
.Sand Dunes
.
Rocky Shores
The rocky intertidal habitat has a very rich diversity of organisms
especially in temperate climates.
Attachment is
critical and competition for space is a prime factor.
The organisms
are well adapted for withstanding tremendous SURF-EXPOSURE and
.
Rocky Shores
also
tolerance to DESICCATION (low tides during the summer days),
temperature
changes, and
salinity
changes( rainfall during low tide).
Rocky Shores
When the tide
goes out, the phenomenon of ZONATION is manifested - horizontal bands or zones
of organisms.
This is true
for both plants and animals.
Each zone has
a particular color or texture from the organisms inhabiting that particular
zone.
Rocky Shores
UNIVERSAL
PATTERNS of zonation, occurring throughout the world,
have been recognized, such that no matter where you might be observing the
exposed intertidal, the middle littoral zone will
often have a community of barnacles, mussels, and rockweeds
Rocky Shores
The nature of
the rock between the tide marks may exert a certain selective influence on the
organisms that attempt to colonize it, in the sense that some rocks are more
susceptible to the activities of boring organisms and others are not and
certain minor variations in zonation may also be
attributed to it.
Rocky Shores
Rocks between
the tidemarks include GRANITE, HARD QUARTZITIC SANDSTONES, SOFT SANDSTONES
(calcareous or not), DOLERITE, CONGLOMERATES, LIMESTONES, SLATELIKE ROCKS, and
various other materials.
Rocky Shores
You see,
porous sandstone will hold water longer during low tide than granite and other
non-porous rocks and therefore may exhibit a different type of zonation than other rocks nearby.
Rocky Shores
Rock texture/rough
and smooth does not really seem to have much of an effect unless friability is
considered where pieces of rock (bearing attached organisms) may break off.
Rocky Shores
The proximity of sand also affects
populations of adjacent rocky areas.
In
some cases, sands shift a good deal, so that a low rocky reef may be buried
under sand at one, and emerged at another time.
This does not always kill everything on
the reef unless it lasts for a long time.
Rocky Shores
Desiccation /
drying out plays a role in organisms to the degree
which they can withstand exposure to the air between the tidemarks.
It may affect
organisms in two ways:
it
may be intense, but for short duration, or
less
severe, but of repeated occurrence.
Rocky Shores
It can be
intensified by increased temperature and air movement (and light).
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Factors
controlling the distribution of organisms on the PACIFIC coast:
Predation is
#1; also competition, exposure to the waves, desiccation, and rain water.
On the
Washington coast the yearly water temperature change is only 5.5'C (10F).
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East coast intertidal populations are affected dramatically by the
relatively LARGE SEASONAL TEMPERATURE CHANGES:
Predation is
also important but less so than in the Pacific
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The Upper intertidal zone: usually termed the LITTORINA ZONE, named
after the small herbivorous gastropods (periwinkles) that occupy this zone that
must survive long periods of exposure.
Rocky Shores
This zone extends
higher than the highest tide where there is great exposure with spray from the
various waves causing the organisms to extend higher into the littoral zone.
There may be
several species of these snails but each species occupy their specific niche..species 1 are the most
tolerant and occupy the highest level
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Species 2,
less tolerant and occupy the next and so on. (one
lower species mimics the air bladders of rockweed).
There is even
a higher zone than the periwinkles and it is occupied by LICHENS (Verrucaria) which occupy a dark zone above the
periwinkles and/or blue-green algae (covered with mucilage to prevent total
desiccation.
Rocky Shores
Middle intertidal zone: barnacles (upper part), rockweed (middle),
& mussels (lower) occupy this zone and each will have one distinct
advantage in regard to their area over the others.
Rocky Shores
Barnacle life cycle
eggs hatch into napulus larva
molts
6 times and turns into cypris larva
cypris
larva finds place to attach
secretes cement from cement glands on the 1st antennae to
attach
develop
into adult
Rocky Shores
Mussels and
seaweeds can crowd out the barnacles but the barnacles can tolerate surf and
desiccation better, giving them the upper position in the Mid-littoral.
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The rockweeds
in the middle of the mid-littoral zone provide a nice moist protective canopy
when the tide is out, so many inverts. can survive
underneath.
The green
crab hides under it during the day and comes out at night.
Rocky Shores
Below the
rockweed are beds of mussels (Mytilis)
using their byssal threads to attach.
Their shape
allows them to adapt well to the wave force and adductor muscles tightly hold
them closed at low tide...protecting them from predators and desiccation.
Rocky Shores
Mussels will
be preyed on by certain snails, seastars, crabs,
shorebirds, lobsters etc. but while the mussels are uncovered for a while, the
marine organisms can only get them while they are covered (and birds vice
versa) Tough life!
Rocky Shores
FORAGING
RUNS...the Predation above, which opens up the habitat for
other species and thus increases species diversity.
The greater
the diversity, the more links in the food chain of that community.
Rocky Shores
LOWER
INTERTIDAL ZONE
There is less
time of exposure to air as you get lower into the zone.
These
organisms while less tolerant of air are better adapted to wave exposure.
Rocky Shores
Dense strands
of kelp can occur here and all this provides living and hiding spaces for a
variety of inverts. (hydroids, bryozoans, nudibranches, worms, crabs, tunicates.
Some are more
conspicuous like the sea anemones, sea urchins, and sea stars.
Rocky Shores
Some inverts.
can BURROW or BORE into hard substrates: rock, coral, wood
by either mechanical abrasion or chemical dissolution.
Some mussels,
date mussels, secrete acid and dissolve limestone, gribbles are small
wood-boring isopods that simply chew into wood. Teredo (shipworm) are also
filter feeders as well as eat wood.
Rocky Shores
Tide pools
are depressions of varying size in the intertidal
such as when the tide is out, standing water is left behind like an oasis for
algae and animals.
They are
subjected to great fluctuations in regard to temp. salinity,
acidity, dissolved oxygen content...
Rocky Shores
The higher
the pool is in the littoral zone, the longer the pool will be exposed, or
isolated from the flush of the oceans waves.
Depth in the
pool is important, as is the overall size.
Rocky Shores
If
then tide is out at night, the release of CO2 from the respiring animals and
plants will increase (NO Ps) and increase the acidity of the pool.
During the
day, PS will cause the pH to increase
Rocky Shores
The larger
pools in the mid zones allow the inverts, seastars
etc. to live higher up on the rocks and therefore be able to feed in the upper
areas longer.
In
California.
some kelps get started in these pools but once a
series of spring tides in June arrive (esp. sunny days), the species living
beyond their limits will be killed off.
Rocky Shores
Biological
succession: going from bare rock to a mature, or climax community, although
nothing is permanent.
Predation
brings about open areas or physical abrasion by logs often
destroy communities in the intertidal.
Rocky Shores
The term
conditioning is used to refer to the process by which a bare rock surface must
go through a sequence of first being settled by bacteria and algae and such
slime-producing organisms before the larva of barnacles and zygotes of rockweeds
will be able to attach themselves.
Rocky Shores
Then mussel
larva will settle down and crowd out the barnacles and rockweeds restricting
them to higher areas.
Predators and
mussels will next move into the picture.
Rocky Shores
Trophic
structure on the rocky beach community: Primary production is the
photosynthetic activity of the BENTHIC seaweeds and also a good part from the
phytoplankton being washed over the area whenever the tide is in.
Rocky Shores
Also
dissolved organic matter and detritus will be a source of nourishment for
filter feeding/ suspension feeders/sponges, barnacles, mussels, while the
grazers, chitons, periwinkles, limpets, sea urchins
are scraping off the benthic flora.
Rocky Shores
Tidal
fluctuations make for a good contribution coming from outside the narrow
confines of the littoral zone and this results in a
large biomass or carrying capacity and the numerous predators at various levels
that enter this ecosystem and the rich diversity of species and high density of
individuals inhabiting the intertidal zone of the
rocky coastlines.
Rocky Shores
Zonation
Few features
of the shores are more obvious than zonation.
All shores,
no matter how large or small the tidal range (max. 17m Bay of Fundy) have at least some degree of zonation
or vertical banding of the organisms living on them.
Rocky Shores
Just as plant
communities occupy definite bands or zones on mountains corresponding to
tolerances to decreasing temperature with increasing elevation, so intertidal communities occupy definite zones on the shore.
Compared to
the mountains though, the shorelines are much compressed vertically.
Rocky Shores
Generally
where the range of tides is small or where the slope of the beach is steep, the
zones are generally narrow.
Where the
slope of the beach is flat and the range of tides is great, then the zones are
wide.
Rocky Shores
Heavy wave
action widens the zones, both above and below the calm water limits and the upper
and lower borders of the zones are less distinct.
An example of
the coast of Vancouver Island where the algae, Porphyra
is the highest level (above the highest barnacles)
.
Rocky Shores
and
grows best in the winter because of the high storm surge and nighttime low
tides and its burned off in the summer.
The barnacle
zone is the first clearly demarcated zone at the top of the shore and this zone
occurs on almost every shore in the world.
Rocky Shores
This is
followed by a zone of mixed barnacles and seaweeds, the mid tide region is
marked by mussels and goose barnacles and beneath this zone is another of
barnacles and algae and several whelks and limpets.
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Below this
zone and marking the beginning of the lower intertidal
zone is the clearly marked zone of brown algae (kelp) interspersed with chitons,starfish, and surf grass.
The zones are
by no means constant in composition, number, width and these factors vary from
season to season, year to year, shore to shore, and even rock to rock.
Rocky Shores
The
"Universal" scheme of zonation
After 30
years of studying intertidal zonation
throughout the world, (tough job), husband and wife team T.A. and Anne
Stephenson published their findings (1949) in which they presented their
"universal" scheme of zonation. They
attempted to formulate general zonation patterns for
the whole world.
Rocky Shores
1. Supralittoral zone ..near sea but above the high
tide mark with some marine influence (spray)
2. Supralittoral fringe...upper limit of
barnacles (in quantity) to nearest higher convenient landmark (upper limit of Littorina or lower limit of land lichens. Spring tides
invade part of this zone.
Rocky Shores
3. Midlittoral zone: the entire intertidal areas, from the upper limit of barnacles to
upper limits of large brown algae at the lower part of the shore. The barnacle
demarcation is an important reference point in the universal scheme.
Rocky Shores
4. Infralittoral fringe: the lower fringe of the
intertidal
..an area extending from the upper limit of whatever organism sets the
lower limit of the midlittoral zone, to the ELWS
(extreme low water spring) tide mark, or in areas of waves, to the lowest level
visible between waves. Organisms living here cannot tolerate complete emersion
but can live in an area of broken emergence through wave action.
Rocky Shores
Organisms
living here cannot tolerate complete emersion but can live in an area of broken
emergence through wave action.
5. Infralittoral zone: the area between ELWS tidal
level and corresponding more or less to the more commonly used "sublittoral" term.
Rocky Shores
This pattern
pointed out by the Stephensons is sensitive to such
factors as wave effects, slope of rocks, differing amounts of sun and shade.
However, while shores may differ in relatively minor details as a result of
such factors, most still adhere to the basic pattern.
Beach and Rocky Shores
Review Answers
1. it is regularly exposed to air
2. the
substrate
3. a great deal of
geologic activity
4. attach themselves to the substrate
5. higher
6. living in moist areas at all times
7. a white, ridged shell
8. filter feeders
9. become more parallel to
the shore
10. space
11. vertical zonation
12. physical factors
13. upper intertidal
14. periwinkles
15. submerging
and uncovering by the tides on a regular basis
16. intertidal
zone
17strandline
18. climax community
19. red, green, and brown
seaweeds
20. light
21. seaweeds
22. bays and lagoons (calm areas)
23. is deficient in oxygen
24. detritus
25 barnacles
26. beach
27. longshore
current
28) the angle that waves hit the
shoreline
29 foreshore
30 erosion /deposition
31. drying out
32. zonation
33help increase species diversity
34. calcium carbonate
34. short
term
36 steeper
37. energy//dislodges
38. longshore current or littoral drift
39. moist////capillary
40 interstidual
sand //cacteria
41. represent similar
organisms present
42. snails of species littorina live there