Seaweeds in general have three major parts: holdfast, stipe, and blade. When referring to an entire plant and all of its parts, we call it a thallus. Holdfast: This anchors the seaweed to the substrate. Stipe (st-eye-p): This stem-like structure connects the blade to the holdfast. The stipe is very flexible which allows the seaweed to flex and bend with wave action. This flexibility prevents it from being ripped loose from the rock. Blade: This is the largest part of the thallus. It is the blade that is responsible for photosynthesis and most of the nutrient absorbtion. Vesicles (vess-ah-culls): Commonly called air or gas bladders, these balloon-like structures provide buoyancy to the seaweed blade when it is submerged. By causing the blade to float, the algae is able to stay at the surface for maximum sunlight exposure. The air or gas inside the bladder is mostly nitrogen with varying amounts of oxygen, carbon dioxide and water vapour. These gases are not trapped inside the bladders but actually diffuse in and out. Not all seaweeds have vesicles. It has also been observed that Fucus species that grow in high wave action areas rarely develop air bladders. Receptacles: The swollen tips of Fucus species and Ascophyllum nodosum become receptacles in the spring. The swollen receptacles produce reproductive gametes, eggs and sperm, and release them into the water. |
FAQs
Low intertidal zone: virtually always underwater except during the lowest of spring tides. Life is more abundant there because of the protection provided by the water.
What determines the lower limit of the intertidal zones? ›
Intertidal Zonation
An organism's lower limit is often determined by competition or predators living in the lower zone. Because a tidepool may hold water even during a low tide, a pool may provide suitable habitat for organisms that would normally be found in a lower zone.
What are the 4 challenges in the intertidal zone? ›
These organisms face many grueling challenges to survive – they must endure hours of harsh sun exposure, low oxygen levels, increased water temperatures, and vulnerability to predators.
What are the 4 intertidal zones? ›
It has four distinct physical subdivisions based on the amount of exposure each gets -- the spray zone, and the high, middle, and lower intertidal zones.
What plants dominate the lower intertidal? ›
We are now moving into the Lower Intertidal zone. Algae dominates this zone. Marine algae, or seaweeds, can be found in patches among barnacles and mussels of the mid-intertidal zone and in some areas the brown algae can extend as far up as the black zone eliminating all other zones, as shown in image on the right.
What organisms inhabit the lower intertidal zone? ›
Intertidal zones of rocky shorelines host sea stars, snails, seaweed, algae, and crabs. Barnacles, mussels, and kelps can survive in this environment by anchoring themselves to the rocks.
What is low intertidal zone in marine science? ›
Marine biologists divide the intertidal region into three zones (low, middle, and high), based on the overall average exposure of the zone. The low intertidal zone, which borders on the shallow subtidal zone, is only exposed to air at the lowest of low tides and is primarily marine in character.
Why the low tide zone is the most populated level of the intertidal zone? ›
The low tide zone is only exposed during low tide and has the greatest biodiversity of the three zones because it provides more favorable conditions for those organisms that cannot tolerate air exposure for long.
What are threats to the lower intertidal zone animals? ›
Pollution & Coastal Runoff
Coastal pollution also poses a threat to tide pool animals and plants. Types of coastal pollution include discarded trash, oil spills, sewage spills, and toxic chemical runoff—all of which can negatively impact intertidal marine life.
Why is it that mussels do not dominate the lower intertidal? ›
In the lower the zone, sea stars are keystone predators that keep the number of mussels and barnacles down.
Pollution in the intertidal zone may result from a number of man's activities. The more obvious sources include spillage of crude oil from ships at sea, discharges of factory effluents and of sewage, polluted water running off from the land and the litter left behind by holidaymakers.
What are 2 things constantly changing in the intertidal zone? ›
These rocky intertidal communities are structured by local- and large-scale environmental drivers that can be dynamic (fluctuating over time, such as temperature and salinity) or static (not varying greatly across years, such as wave exposure and fetch/the distance wind travels over open water).
Is the low tide zone almost always covered with water? ›
Middle Intertidal Zone: Tides ebb and flow over this zone twice per day, meaning it frequently alternates between wet and dry conditions. Low Intertidal Zone: This zone is almost always covered by water. It only dries out during very low spring tides.
What are the lower intertidal zone ABiOTIC factors? ›
ABiOTIC FACTORS OF INTERTIDAL ZONES
Abiotic factors include the water temperature, amount of sunlight, soil composition, and dominate geographical features. Water Temperature: Since intertidal zones are all around the world, their climates change drastically, thus changing the temperature of the water.
How hot is the lower intertidal zone? ›
The weather in the intertidal areas can be extreme. The air and water temperature can range from extremely hot to below freezing to moderate. The average range of air temperature is from 75°f to 102°f. The intertidal zone does have seasons.
