Ecology of a Rocky Shore Ecology of a Rocky Shore CommunityCommunity

Understanding the Influence Understanding the Influence of Tidesof Tides

• Tides have a powerful influence on Tides have a powerful influence on how and when we play at New how and when we play at New England beaches. England beaches. – During low tide on Cape Cod Bay, it's During low tide on Cape Cod Bay, it's

often possible to walk 1/2 mile out onto often possible to walk 1/2 mile out onto the flats in ankle-deep water. the flats in ankle-deep water.

– Six hours later, the water is suddenly Six hours later, the water is suddenly too deep to stand in.too deep to stand in.

– Tides cause currents that greatly affect Tides cause currents that greatly affect fishing, kayaking, swimming and surfingfishing, kayaking, swimming and surfing

Cause and Affects of TidesCause and Affects of Tides• The ebb and flow of tides are caused by the The ebb and flow of tides are caused by the

gravitational effect of the Sun and Moon on the gravitational effect of the Sun and Moon on the Earth. Earth.

• Because the Moon is much closer to Earth than Because the Moon is much closer to Earth than the Sun, its influence is much greater.the Sun, its influence is much greater.

• When the Moon is up, it pulls water beneath it When the Moon is up, it pulls water beneath it outwards into a bulge. On the opposite side of outwards into a bulge. On the opposite side of the Earth, a similar bulge is also formed by water the Earth, a similar bulge is also formed by water being moved outward from the planet's rotation. being moved outward from the planet's rotation.

• These two bulges travel around the globe, These two bulges travel around the globe, producing (in most places) two high tides every producing (in most places) two high tides every day. day.

The water Bulge makes The water Bulge makes TidesTides

Wave ActionWave Action• Tides directly affect Tides directly affect wave height wave height

•Waves are a powerful Waves are a powerful forceforce

•Tidal currents change Tidal currents change direction twice a day direction twice a day and can run at speeds and can run at speeds of up to 5 knots of up to 5 knots around points and at around points and at harbor entrancesharbor entrances

The Angry SeaThe Angry Sea

Zones of Life along a Rocky Zones of Life along a Rocky ShoreShore

Rock Intertidal ZonesRock Intertidal Zones• CC is the is the splash zonesplash zone: not submerged : not submerged

except in storm tidesexcept in storm tides

• DD is the is the high tide zonehigh tide zone: covered : covered during high tideduring high tide

• AA is the is the mid tide zonemid tide zone: covered much : covered much of every dayof every day

• BB is the is the low tide zonelow tide zone: covered most : covered most of the time, only exposed during high of the time, only exposed during high tide.tide.

Why are some animals and plants Why are some animals and plants located in special zones and not all located in special zones and not all over?over?

Adaptations for life on a high energy Adaptations for life on a high energy rocky shorelinerocky shoreline

• High energy wavesHigh energy waves

• Low tide exposureLow tide exposure

Animals on a typical New England Animals on a typical New England rocky shorerocky shore

• Asian Shore CrabAsian Shore Crab

((Hemigrapsus sanguineusHemigrapsus sanguineus))

• Periwinkle snails(Periwinkle snails(Littorina Littorina littorealittorea))

• Blue MusselsBlue Mussels(Mytilus edulis)(Mytilus edulis)

• Purple Sea Purple Sea Urchin(Urchin(Strongylocentrotus Strongylocentrotus purpuratuspurpuratus ) )

• Rock BarnaclesRock Barnacles

(Chthamalus fragilis)(Chthamalus fragilis)

• Common Sea Star(Common Sea Star(Asterias Asterias forbesi)forbesi)

Algae on a typical New England rocky shoreAlgae on a typical New England rocky shore

• Fucus (Fucus (Fucus Fucus gardnerigardneri ) )

• Knotted Wrack Knotted Wrack ((Ascophyllum Ascophyllum nodosumnodosum))

• Kelp (Kelp (Laminaria)Laminaria)

More Algae More Algae TypesTypes

•Ulva lobata (Sea Lettuce)Ulva lobata (Sea Lettuce)

•Chondrus (Chondrus (Chondrus Chondrus chrispus)chrispus)

Adaptations to life on a rocky shore Adaptations to life on a rocky shore lineline

Adapting to Wave ShockAdapting to Wave Shock

• BarnaclesBarnacles

• Cements shell Cements shell to rockto rock

• SnailsSnails

• Use a suction Use a suction cup like footcup like foot

Adaptations to Wave ShockAdaptations to Wave Shock

• Sea Stars Sea Stars and Urchinsand Urchins

• Tube feet Tube feet with suction with suction cup endscup ends

Adaptations to Wave ShockAdaptations to Wave Shock

• Blue MusselsBlue Mussels• Byssel Threads ( strong cables)Byssel Threads ( strong cables)

Adaptations to Wave ShockAdaptations to Wave Shock

• Crabs and LobstersCrabs and Lobsters• Wedge into rock spacesWedge into rock spaces• Hide under rocks Hide under rocks

Adaptations to Wave ShockAdaptations to Wave Shock

• Sea Weeds (macroalgae) Sea Weeds (macroalgae) • Hold fasts attach to rocksHold fasts attach to rocks

Rocky shore animal feeding Rocky shore animal feeding adaptationsadaptations

• BarnaclesBarnacles• Filter food with Filter food with

feathery legs feathery legs (filter feeder)(filter feeder)

• SnailsSnails• Scrape food with Scrape food with

a radula - tongue a radula - tongue with teeth with teeth (grazers and (grazers and carnivores)carnivores)

• Sea stars Sea stars • Use tube feet and Use tube feet and

stomach stomach

Reproduction adaptationsReproduction adaptations

• Barnacles are Barnacles are hermaphrodithermaphroditeses

• Each Each barnacle has barnacle has both male both male and female and female reproductive reproductive organsorgans

Sea star and Urchin Sea star and Urchin ReproductionReproduction

• Sea stars and Sea stars and Urchins broad cast Urchins broad cast eggs and sperm eggs and sperm into the waterinto the water

Marine SnailsMarine Snails

• Marine snails Marine snails mate and mate and deposit egg deposit egg casescases

Marine Arthropods like Marine Arthropods like crabs and lobsters mate.crabs and lobsters mate.• Female attracts Female attracts

male using male using pheromones.pheromones.

• After the female After the female molts and molts and mates with the mates with the male, eggs will male, eggs will later be later be deposited on deposited on underside of her underside of her abdomen and abdomen and carried until carried until they hatch.they hatch.

• Lobster with eggsLobster with eggs

• Green crab with Green crab with eggseggs

Off Shore In the Bay!Off Shore In the Bay!

The Harbor Seal (Phoca vitulina)

Eastern Atlantic Harbor Eastern Atlantic Harbor SealsSeals• Live along the western coast of Europe Live along the western coast of Europe

and along the New England shorelineand along the New England shoreline

• They like to They like to haul out haul out on flats that are on flats that are uncovered at low tide. uncovered at low tide.

• These seals are also seen in estuaries.These seals are also seen in estuaries.(Narragansett Bay!) (Narragansett Bay!)

• They spend about 80 percent of their lives They spend about 80 percent of their lives in the water. in the water.

Harbor Seals AppearanceHarbor Seals Appearance• Have a fat body and a narrow-pinched head. Have a fat body and a narrow-pinched head.

The nostrils are narrow and show a typical V-The nostrils are narrow and show a typical V-shape. The eyes are quite big and close set to shape. The eyes are quite big and close set to each other. each other.

• The seals' belly is always lighter than its The seals' belly is always lighter than its back. back.

• It is difficult to It is difficult to

distinguish males from distinguish males from

females. females.

• The seals' back usually The seals' back usually

shows varied spots. shows varied spots.

The Eastern Atlantic Harbor seals' fur color The Eastern Atlantic Harbor seals' fur color varies from grey to brown. The animals have varies from grey to brown. The animals have black spots on their body.black spots on their body.

Seal Life-cycleSeal Life-cycle

•The females reach sexual maturity in 3 of 4 The females reach sexual maturity in 3 of 4 years of age. years of age.

•Males reach sexual maturity at six years of Males reach sexual maturity at six years of age.age.

• These seals eat a variety of fish: squid, sole, These seals eat a variety of fish: squid, sole, whiting, herring, shrimp, and mussels. whiting, herring, shrimp, and mussels.

Life-CycleLife-Cycle• Unlike most other Unlike most other pinnipeds harbor seals are harbor seals are

generally solitary. generally solitary.

• They are not highly communicative, but when feel They are not highly communicative, but when feel threatened they may respond by lunging, scratching, threatened they may respond by lunging, scratching, snorting, growling or other aggressive snorting, growling or other aggressive communications. communications.

• Although they are solitary they haul out in small Although they are solitary they haul out in small groups for protection from predators. groups for protection from predators. – They haul out on rocky shores, sand beaches, reefs, piers or They haul out on rocky shores, sand beaches, reefs, piers or

ice, to breed, moult and rest. ice, to breed, moult and rest.

• Moult takes place in July and August. During this time Moult takes place in July and August. During this time the seals' metabolism is reduced. They eat very little the seals' metabolism is reduced. They eat very little so conserve the energy usually expelled finding food. so conserve the energy usually expelled finding food.

A Male DisplayA Male Display

Haul OutHaul Out

• Pups are weaned after 4 up to 6 weeks.Pups are weaned after 4 up to 6 weeks.

• Due to the high percentage of fat in the mother's Due to the high percentage of fat in the mother's milk (45%) the pups double their weight by the milk (45%) the pups double their weight by the time they are weaned. time they are weaned.

• From birth on the pups immediately can swim and From birth on the pups immediately can swim and dive. After 2 days the pups can remain submerged dive. After 2 days the pups can remain submerged for about 2 minutes. for about 2 minutes.

Mating Mating • During the summer time the seals come together During the summer time the seals come together

to give birth and nurse their young. to give birth and nurse their young.

• Mating takes place right after weaning.Mating takes place right after weaning.

• Unlike other mammalians the ovum becomes Unlike other mammalians the ovum becomes implanted in the wall of the uterus approximately implanted in the wall of the uterus approximately three months after breeding. three months after breeding. – This makes it possible to both nurse pups and This makes it possible to both nurse pups and

breed in the short period the seals are together. breed in the short period the seals are together.

• During the mating season male seals can become During the mating season male seals can become very aggressive.very aggressive.– They may fight when competing for a female.They may fight when competing for a female.

• The males also display aquatic performances and The males also display aquatic performances and vocalizations to attract a female. vocalizations to attract a female.

Threats to the Harbor SealThreats to the Harbor Seal• Natural predators: killer whales, sharks and polar bears. Natural predators: killer whales, sharks and polar bears.

• They usually remain in the vicinity of their traditional breeding area year They usually remain in the vicinity of their traditional breeding area year round. round. – Due to this restricted range the viability of harbor seal populations Due to this restricted range the viability of harbor seal populations

can be at risk.can be at risk.

• the population in Lake Ontario disappeared in the early 1980's.the population in Lake Ontario disappeared in the early 1980's.

• In some areas (Norway, Iceland) people still hunt themIn some areas (Norway, Iceland) people still hunt them

• In other countries (e.g. the United Kingdom) fishermen may shoot those In other countries (e.g. the United Kingdom) fishermen may shoot those that became entangled in fishing nets. that became entangled in fishing nets.

• Fishing nets, plastic wrapping bands and marine debris are also threatsFishing nets, plastic wrapping bands and marine debris are also threats

• Hunting and water pollution has drastically decreased the population of Hunting and water pollution has drastically decreased the population of Eastern Atlantic harbor seals in the waters of The Netherlands. Eastern Atlantic harbor seals in the waters of The Netherlands. – Down to less 500 in 1975, out of aprox 3000 seals. Down to less 500 in 1975, out of aprox 3000 seals.

• the population recovered slowly, In 1987 about 1,000 sealsthe population recovered slowly, In 1987 about 1,000 seals

• Pollutants decrease the productivity and may cause premature births. Pollutants decrease the productivity and may cause premature births.

• Some seals have been killed by being trapped in the intake pipes of Some seals have been killed by being trapped in the intake pipes of power plants. power plants.