Intertidal Habitats - Exam 3

Emersion

Out of the water and exposed to air

Immersion

Submerged in the water

Substrate

Material on or in which the organism lives

Epifauna

Organisms that live on the surface of the substrate

Infauna

Organisms that live in the substrate

Meiofauna

Organisms that live between the grains of substrate (very SMALL)

Intertidal Habitat

Habitat along the shore that lies between the highest high tide and the lowest low tide.

Physical stressors in the intertidal zones

-Water loss/desiccation
-Temperature
-Salinity
-Wave action
-Space
-Oxygen

Water loss

When exposed, organisms risk desiccation. Coping mechanisms include hiding, closing up, and tolerance.

Hiding to prevent desiccation (two different ways)

1-Mobile organisms can move into tide pools or moist, shady crevices; some organisms cluster together to prevent water loss.

2-Organisms that have a protective covering can close shut to seal in moisture or burrow in soft-bottom habitats. Limpets clamp themselves tightly to a hard substrate.

Tolerance to desiccation

Some intertidal chitons can survive the loss of 75% of the water in their tissues. Rockweeds such as Fucus (brown algae) can survive a water loss of up to 90%.

Temperature adaptations

Heat in the summer and cold in the water. Mobile organisms move into crevices where the air is cooler in the summer. Light shell color in snails.

Salinity adaptation

Varies depending on temperature and precipitation. Most organisms in tide pools can withstand a variety of salinities. Burrow or reduce activity until high tide returns.

Wave action adaptations

-Some organisms have a compact shape and low profile to reduce wave impact; others anchor to the substrate.
-Organisms with shells inhabiting exposed sites tend to have thicker shells, while others are flexible

Space adaptation

-Limited space is available, particularly for sessile organisms that need a permanent place to attach.

-Competition for space is very high: first to settle in an open space, good at keeping a space, quick to reproduce to fill other spaces with offspring, and take over an already-occupied space.

Oxygen adaptation

Tide pools with a high density of organisms deplete oxygen quickly. Some organisms have evolved the ability to exchange gas in both air and water.

Advantages of living in the intertidal

-High tide brings in plankton, macroalgae, and detritus.
-Wave action brings in nutrients and oxygen.
-High light levels and nutrient-rich coastal waters allow rapid growth of algae, supporting food web.

Which is not a physical stressor organisms in the intertidal face?
a.)     Wave action

b.)    Oxygen availability

c.)     Competition for space

d.)    Extreme temperatures

e.) High pH

e.) High pH

What is an example of a species that has evolved in the intertidal to exchange oxygen through its skin?

Mudskippers, some gastropods (slugs

An oyster is an example of an (blank) and a clam is an example of an (blank) organism.
a.)     Infaunal, epifaunal

b.)    Epifaunal, meiofaunal

c.)     Epifaunal, infaunal

d.)    Meiofaunal, infaunal

e.)     Infaunal, meiofaunal

c.) Epifaunal, infaunal

Closing” up is a mechanism to cope with (blank) commonly seen in intertidal (blank).
a.)     Desiccation, echinoderms

b.)    Wave action, bivalves

c.)     Space, macroalgae

d.)    Desiccation, bivalves

e.)     Oxygen, gastropods

d.) Desiccation, bivalves

Zonation

-The presence of organisms only within a particular range.

-Upper, middle, and lower intertidal

What limits the distribution of species in the intertidal?

-Temperature
-Salinity
-Oxygen
-How long underwater
-Water loss
-Wave movement.

Upper distribution in intertidal habitats is determined by….

tolerance to emersion

Lower distribution in the intertidal habitat is determined by….

Biological factors such as competition and predation.

Upper zone in intertidal habitats

Occurrence depends on tolerance to emersion; organisms keep wet via wave spray, immersed only during high spring tides.

Middle zone in intertidal habitats

Regularly immersed and then exposed by tides; moderate competition and predation, but organisms still must be able to cope with regular emersion.

Lower zone in intertidal habitats

Immersed most of the time; organisms tolerate limited emersion; species distribution mostly determined by biological factors. More species rich than other intertidal zones.

What organisms are usually found in the upper intertidal?

Periwinkles dominant; limpets, licens, encrusting algae also common

What organisms are usually found in the upper middle intertidal?

Barnacles

What organisms are usually found in the lower middle intertidal?

Mussels, barnacles, and seaweeds.

What organisms are usually found in the lower intertidal habitat?

seaweeds, surf grass, marcoalgae, and sea stars

Intertidal habitats differ based on…?

Substrate

The upper limit of species distribution in the intertidal is usually determined by what?
a.) presence of predator
b.) competition for space
c.) tolerance to emersion
d.) A and B
e.) A, B, and C

c.) tolerance to emersion

The lower limit of species distribution in the intertidal is usually determined by what?
a.) Presence of predator
b.) Competition for space
c.) Tolerance to emersion
d.) A and B
e.) A, B, and C

d.) A and B

Where in the intertidal would you expect periwinkle snails to be common?
a.) Upper intertidal
b.) Upper middle intertidal
c.) Lower middle intertidal
d.) Lower intertidal

a.) Upper intertidal

Where in the intertidal would you expect mussels to be common?
a.) Upper intertidal
b.) Upper middle intertidal
c.) Lower middle intertidal
d.) Lower intertidal

c.) Lower middle intertidal

Where in the intertidal would you expect sea stars to be common?
a.) Upper intertidal
b.) Upper middle intertidal
c.) Lower middle intertidal
d.) Lower intertidal

d.) Lower intertidal

What happened when sea stars were removed from a rocky intertidal community?

Mussels soon dominated the intertidal community and species diversity decreased because mussels are better competitors for space.

Intertidal substrate differences

Hard substrate: Rocky shores, like headlands, rocky beaches.
Soft substrate: Sandy beaches, mudflats, salt marshes.

Soft substrate organisms are usually…

Infaunal!

Soft-bottom intertidal habitats advantages

Sediment stays moist after tide goes out, keeping organisms moist and cool.

Soft-bottom intertidal habitat disadvantage

Oxygen availability depends on grain size; deep, fine sediments tend to be anoxic.

What organisms are usually found in upper sandy intertidal habitats?

Amphipods, isopods, fiddler, and ghost crabs

What organisms are usually found in middle and lower intertidal habitats?

Polychaetes, clams, and snails.

Burrowing invertebrates in soft intertidal habitats compete for…?

Space, resulting in vertical stratification of species within the sediment.

Describe the physical stressors organisms living in intertidal habitats face and how they cope with each stressor

Both: Desiccation, wave action, extreme temperatures, and salinity.

-Desiccation: operculum to seal moisture inside, or seal shells tight, and some can lose a large percentage of their water content and be fine.
-Waves: Root-like “holdfasts” to cling to rocks, some have stalks to hold onto rocks (like mussels). Barnacles cemet themselves directly to the rock. Limpets use a suction-foot.
-Temperature: Some produce heat-shock proteins to manage high temperatures. Hides in shaded, damp crevices during low tide.
-Salt: Majority are euryhaline (able to handle a wide range of salinities) or hide in moist crevices.
-Oxygen Availability: Can tolerate anoxia, but some can also survive through specialized biochemical adaptations (anaerobic respiration)

Describe zonation in intertidal habitats, including the factors that limit the upper and lower distribution of organisms found in these habitats

-Upper limits (physical/abiotic factors): Restricted by their ability to withstand desiccation, heat stress, high salinity, and lack of oxygen, as they’re exposed to air for long periods.
-Lower limits (biological/biotic factors): Restricted by competition for space and predation.

-Spray/splash zone (upper intertidal): Occasionally wetted by spray; dominated by organsims like lichens and periwinkle snails.
-Upper middle intertidal: Submerged only during high tide, creating high heat and drying stress. Dominated by barnacles and limpets.
-Lower middle intertidal: Submerged/exposed twice daily. Dominated by mussels and seaweeds.
-Low intertidal: Almost always submerged, allowing high biodiversity, like sea stars, seaweeds, etc.

Compare and contrast rocky shore and soft-bottom intertidal communities.

-Rocky shore: High-energy coastal areas, solid, stable substrate that support attached organisms (epifauna). Biological factors like competition for space and predation, rather than just physical. Snails, barnacles, mussels, crustaceans.

-Soft-bottom: Sandy beaches and mudflats, unstable sediments where organisms must burrow (infauna) to survive wave action and anoxic conditions. Zonation less distinct, but still exists based on tidal level and moisture content. Food source is mostly detritus-based. Seagrass, clams, worms, crustaceans, etc.

-Similarities: Both are harsh, highly stressful environments that are alternately exposed and submerged by tides.