Analysis of Campbell’s Bay Rocky Shore Ecosystem

My investigation was to analyse and collect data from the Campbell’s Bay Rocky Shore ecosystem. Rocky shores are coastal shores made from solid rock. This ecosystem relies on the movement of the tide, thus making different conditions that change species’ environments. I am focusing on finding the distribution pattern of Beaked Barnacles (Austrominius Modestus) and Oyster Borer (Haustrum Scobina). The main abiotic factors include desiccation and air exposure.

Zonation

The distribution pattern on the Rocky Shore is zonation. Zonation is the distribution of organisms into different zones.  Zonation is created and occurs due to the tidal movements of water.  Different species live in different tidal zones on the rocky shore due to different adaptations toward desiccation and exposure to the sun.

Between the high and low-tide is the intertidal zone.

Intertidal zonation is when you get horizontal bands of different species. These are created by abiotic factors, like tidal movement, desiccation and air exposure. Tide goes up and down, leaving some organisms exposed to the air without water.

When the water leaves, species living in the high intertidal zone need to be capable of dealing with abiotic factors such as desiccation. Species living in the low intertidal zone must be better at competing for space, as there’s a higher risk of competition.

In the intertidal zone there are two types of stresses, abiotic and biotic. The main abiotic factors are desiccation and air exposure. The biotic factors are predation and competition between different species.

Distribution Pattern

Barnacles

My data displayed that barnacles have a clumped distribution pattern as they were often grouped together. The grouping of barnacles together is due to their need to reproduce with each other because they are unable to move. My data showed that barnacles are found to be most common in the intertidal zone (10-20 metres from high tide) and have an average amount of 42% in a quadrat (from 6 quadrats). This is much more when compared to the high tide zone (0-8 metres from high tide) which has an average of 12.8%, and low tide zone (22-32 metres from high tide) which had an average of 4.2%. These statistics show that the barnacles seem to survive the best and are more common in the intertidal area compared to the high and low tide zone.

Oyster Borer

My data displayed that the oyster borer’s distribution is most common around the intertidal zone, with some being found in the low tide zone. The average amount of oyster borer in the intertidal zone (10-20 metres from high tide) was 6.25% (in 6 quadrats), while the average in high tide zone (0-8 metres from high tide) was 1.52%, and the average in the low tide zone (22-32 metres from high tide) was 0%.

Oyster borers also had a reasonable clumped distribution pattern as they were usually together. This is due to the fact that they eat barnacles so they try to stay near their food source.

Kite Diagram comparing Beaked Barnacle and Oyster Borer (and other species)
 

Abiotic Factors

Abiotic factors are factors in the environment caused by non living things.

Generally abiotic factors can be: terrain, temperature, weather, man made features, humidity, desiccation. Abiotic factors can affect the survival of a species, for example, if the temperature is too hot or cold some species may not have the structural adaptation to survive amongst this abiotic factor, and may die out or have to move to a different environment. This would affect the species distribution on the shore.

An abiotic factor that both beaked barnacles and oyster borers have to deal with is desiccation and air exposure. This influences the two species’ time spent submerged in water.

Barnacles

Barnacles are filter feeders, eating species that float in the water like bacteria, plankton, algae etc. Because their food all lives in water they can get their food whilst in the water, using their tentacles. They also should have access to water to avoid getting desiccated. This means they need to be submerged for some time during the day.

Because they are not blanketed by water all the time due to being in the intertidal zone, barnacles need to seal water inside their bodies while waiting for water to come.

Oyster Borer
Oyster Borer need water to help stop them from desiccating. They need to be submerged underwater frequently. They also need to be underwater to eat food, but they also eat barnacles, and need sufficient submersion time to eat the barnacles, otherwise they are at the risk of other species coming along to eat their food. Oyster Borers live in the intertidal zone to prevent loss of food and because they have adaptations that enable them to survive in this zone.

Biotic Factors

Biotic factors that affect Beaked Barnacles and Oyster Borer is predation and competition.

The beaked barnacles’ predation is oyster borer, and the barnacles’ competition is other species that also live on rocks, like mussels. To prevent too much competition, the barnacles live in the intertidal zone as some other species cannot survive in the intertidal zone as they don’t have the adaptations to live in it that barnacles have.

Oyster Borers’ predation is whelks. Whelks live from mid to low tide zones so some of them can feed on oyster borer. Oyster Borer competition is other species that eat barnacles. But by positioning themselves in the intertidal zone where they can survive well due to their adaptations, they have a good amount of barnacles as their food source.

Barnacles’ ecological niche is that they live in the intertidal zone on rocks, in attempt to stay away from predators that need a lot of submersion time. The main predator of Barnacles is Oyster Borer.

Oyster Borer’s ecological niche is that they live in the intertidal zone too, as barnacles are their food. By living in the intertidal zone it helps them to stay away from competition as they have adaptations that mean they can survive well in the intertidal zone. This leads to the distribution of both these species being in the intertidal zone as they can survive well to do their adaptations, have a sufficient amount of food, and not too much competition there.

Interrelationship

Barnacles and oyster borers’ have the interrelationship of predation. Oyster Borer is the main predator of barnacles, so oysters stay around where barnacles are. Barnacles usually survive best in the intertidal zone, making oysters stay around the intertidal zone too.

Adaptations

A structural adaptation that barnacles have is impermeable shells that don’t allow water to pass through. Their shape is hydrodynamic, which means they can withstand the harsh force of waves, and are able to protect themselves from predators. This allows them to resist the movement of tides well.

A behavioural adaptation that barnacles have is the ability to stick their bodies firmly to rocks. They secrete an adhesive substance that they can use to stick themselves to surfaces. This helps them resist the impact of waves so they can survive well in the harsh conditions of the intertidal zone.

A psychological adaptation barnacles have is a valve that opens up when the tide is out, to collect food and water, and then when the tide starts coming in it closes the valve to keep the food and water in their body. They then can process this food in their bodies. Their feathery legs sift the water for food. Due to this adaptation it means barnacles can avoid the risk of desiccation and too much air exposure, and have an advantage at surviving and feeding in the intertidal zone.

A structural adaptation that oyster borers have is a muscular foot that they can force open and insert into a barnacle their proboscis (an organ that sucks the food), eating the barnacle from the inside out.

Another structural adaptation that oyster borers have is the ability to create mucus which blocks the entrance of their shell, helping to create resistance to the risk of desiccation, allowing them to survive better in the intertidal zone.

Another structural adaptation oyster borer has is their tough outer shell which helps protect them from waves and predators, which also helps it camouflage to its surroundings.

Discussion

Desiccation and air exposure are abiotic factors that affect barnacles and their adaptation. They have adapted to the harsh conditions of the intertidal zone, with their impermeable shells and this helps them stop desiccation. This explains their distribution pattern, because they are able to survive in the intertidal zone and from this can have less competition between other species, as not as many species can survive the intertidal zone due to its conditions. This means only species that are adapted to the intertidal zone environment can survive well there. The level of the tide can affect the barnacles’ submergence time. If they live in a tide level that’s higher the barnacles will have more water but it means there will be more predators to impact their survival as many predators need more submergence time in water to feed. The barnacles’ valve closes its food and water into its body when the tide goes in, meaning the barnacle will still have sufficient amount of food and water when the tide is in. According to my data I collected, barnacles tend to survive best in large groups, so they need to stay around each other to reproduce.

Desiccation and air exposure are also abiotic factors that also affects Oyster Borer. Oyster Borer is able to resist these abiotic factors due to their adaptations of being able to create a mucus blocking the entrance to their shell to protect themselves from desiccation, and their tough outer shell provides protection from the harshness of waves. Oyster Borer also live in the intertidal zone as their main source of food is barnacles. With oyster borer being adapted to live in the intertidal zone, this is a good source of food as barnacles tend to survive best in large groups, meaning the oyster borer has a lot of food to eat. If barnacles did not have their adaptations to the intertidal zone they’d live in the low tide zone meaning they’d have more submergence time. This means other predators would feed on the barnacles and leave the oyster borer with not much food source, causing the oyster borer to be less likely to survive, meaning they would not have their ecological niche.

My data that I displayed earlier proves that there is a predation inter-relationship between Barnacles and Oyster Borer, with the Barnacles being most common in the intertidal zone (average of 42%) and Oyster Borer also being most common in the intertidal (average of 6.25%). As I displayed earlier the low tide and high tide zone both were much lower values for both species.

These results show that there is a predation type of interrelationship between the two species, as when the Barnacles are most common in the intertidal zone, so are the Oyster Borers.

Bibliography

• https://basicbiology.net/environment/marine/rocky-shore
• http://www.seafriends.org.nz/enviro/habitat/shore.htm
• https://year12biokbhs.weebly.com/uploads/2/6/3/7/26373118/barnacle_resource_with_extracted_highlights.pdf
• http://www.marinelife.ac.nz/species/849
• https://merc.org.nz/wp-content/uploads/2014/11/Oyster-borer.pdf
• https://www.otago.ac.nz/marine-studies/resources/download/otago062894.pdf