This project stemmed from one seemingly simple question: why do things adapt the way they do in the inter-tidal region and what does that mean for their survival and the survival of the organisms around them? Little did I know this would end up to be one of the most complex concepts I have studied so far in my undergraduate experience. Through these articles I was able to expand my knowledge of scientific writing and research in general, but also specifically how organisms in rocky coastlines worldwide were so different yet also very similar. Each species of organism I read about was very different. Different types of specializations in different parts of the world interacting in very different ways. At the same time, each organism shared themes with many others. Some organisms were similar by the way they reproduced, even if they were specialized this way for very different reasons. Another large similarity I found was that organisms, no matter how seemingly small and insignificant, can effect and entire population if not ecosystem. No matter how simple and interaction is it may have possible backlash in many other populations as well. I guess, to answer my own question, Organisms adapt to become successful or maintain success through efficient use of energy and increased biological fitness. The ways species interact with each other are extremely complex, each different from all others. Even researchers sometimes have a hard time understanding why organisms react the way they do and how this impacts others, but that doesn’t mean that it is a lost cause. Actually, inter tidal research was and is remaining extremely relevant, as you can see from the vast array of time periods when these articles were published.

 

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Researchers in California showed that the native Black Abalone species have a very low recruitment in populations following mass moralities. This is not surprising, many abalone species have closed populations, but scientists have a few explanations on why black abalone populations can’t bounce back. The first reason is that abalones in the area are not producing larvae and no other sites are dispersing into the area. A second idea is that abalone are producing larva but the larva cannot settle successfully in the habitat. The third reason is that the larvae are being killed by the disease before they can be counted in surveys. Results show that the first reason is more likely than the second and third reasons and is probably a larger contributor to the lack of abalone. In order to cope with this lack of individuals, the authors suggest an entire ecosystem based management plan to jump start population size. This is because abalone larvae are hard to settle in many habitats, and once population sizes are low it is less likely they will even produce offspring since they broadcast spawn. This is similar to posts I have done before about broadcast spawners. It also reminds me in ways of the piece I did on anemones because both articles were focused on how animals respond and are affected by parasites and diseases.

 

Abalone

The paper I read this week highlighted how hermit crabs in the intertidal zone are actually limited in population size by how many shells there are. The author supports this logic by showing that: there are no extra shells available for additional crabs, many crabs are living in shells that are too small or broken, when larger shells are present, larger crabs are present, and lastly when shell amounts increase, population increases. He then goes on to describe how in crab populations there are no shells present which are extra. Crabs will even fight to pull each other out of shells to have new ones which are bigger. Crabs usually use bigger shells when available because shells that are small and broken leave crabs more prone to be killed by predators. The scientist tried to increase crab populations by adding shells to an isolated reef. He was able to do this but the rate of increase was lower than expected. This is because shell supply changed seasonally.

 

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            This paper, more than any other, truly highlights the community impacts each organism can have on another in accidental ways. In this study, scientists were looking for the impacts filter feeders in the intertidal zone would have on the transition of a parasite from one host to another. A species of crab is infected by meritrema, a marine parasite, after first being transmitted by a sea snail. The study tested three different filter feeders, anemones, cockles, and barnacles as well as dense mats of sea weed which would cover the crabs from infected snails and water. While the study showed no effect on transmission rate when cockles, barnacles, or sea weed was concerned, the sea anemones greatly reduced the amount of transition of the parasite from snail to crustacean. One hypothesis for these phenomena is that the other filter feeders are size specific and the parasite is small enough to sift through the water column past them. While this is certainly a great intuition, the scientists are still unsure why exactly this occurs. The important part of this article in light of my blog, is to look at the specialization of the sea anemone. Although it is certainly indirect, this very specific type of filtering has a drastic effect on the life history of a parasite and the effects it will have on entire marine populations. For instance, if this crab were a keystone predator, the sea anemone would be preventing the downfall of, perhaps, an entire ecosystem.

anemone

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In the experiment described in this article, an intrusive tunicate species was found in Antofagasta Bay in Chile, far from its normal coastal range in Australia. In order to prove the tunicates were not drawn to this Bay in particular, they did tests with tunicates both inside and outside of their newly populated habitat in Chile. The results showed that tunicates were successful at growing and reproducing inside and outside the bay. Scientists then tested the effects of this tunicate on a local species of mussel, and eventually published results finding that the tunicate was able to overcrowd the native population. Overcrowding lead to a decreased fitness in the mussel population due to increased competition and limited refuges left for the mussels to occupy. Another study conducted by the author showed that at the rocky intertidal level, predation by sea stars and large snails on small juvenile tunicates was a key limiting factor to their continued growth and those predators act as regulating factors in their life history. This particular article is interesting because it takes an organism which is so sophisticated and successful it can survive at inter-tidal zones across the globe. Somehow this small organism is able to have a major effect on native populations but it also fits flawlessly into the predatory interactions already in place on mussels found in Chile naturally. It is important to show how this animal has a negative impact as an invasive species, because as you can see in this example, it can easily out compete its “peers” so to speak. This will put the native mussel population in direct threat of being drastically limited.

 

tunicate

Here are some really good images showing how important the rocky inter-tidal zone is on a world scale. The first shows how much of the earth is coastline dedicated to inter-tidal areas, the second shows the many different regions which are encompassed in such a zone, and why it is necessary to specify “Rocky Inter-Tidal” as my area of study.

world map coast intertidal zone

The article I chose to go with these images given is more of an overview. It describes how vertical zonation was found in the intertidal zone, and how experimentation has needed to evolve through the years, yet many approaches remain in place. The first scientists to study zonation were Doctors Cowels, Clements, and Shelford in the United States. They all started in the 1930’s and although looking for answers about the limits of a marine community but based much of their evidence on that of plant science and botany. The scientists focused on a natural history approach at first, but after settling in the West, they started using less deterministic methods. This approach carries over into some studies I have talked about in the blog thus far and is still an important method of study.

perspective post article

 

This piece is a little different from the first two, but I feel in many ways is even more important to the blog. The author describes the taxes of living in a harsh place like the rocky shore and how its ever changing tides and temperature effect how organisms can intake oxygen. This basic need is affected by many different factors, such as how active the water is. The slower the tide the less oxygen uptake there will be, so even though some protection from waves is helpful to organisms it can also reduce oxygen intake. The author, G. M. Branch, makes a note that previous experiments show that an upper tidal niche is most strained by the environment because it has higher temperatures and more exposure to the sun. In these harsher ecosystems, metabolic rates are adapted to stay low in order to maintain oxygen conservation. In one particular species of limpet, P. Granularis, has a lower rate of metabolism because it lives higher on the shore and has more competition with barnacles than its mid-shore cousins. Therefore, the high shore species of limpet has a lower metabolic rate because it has less food resosurces available.

Here is the paper referenced above:

limpet