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Amy Carlo, Eugene Disney, and Eric Ettner
A Test for how Species Richness Varies With Wave Force and Substrate Type
59/80 No graphs of mention of potential results
INTRODUCTION
Background 4/4
For experimental ecologists, the rocky marine Intertidal has always been an exciting place. It is so bracketed in its spatial extent as to make ecological zonation evident within the scales of tens of feet. Most of the animals are sessile, small, and plentiful: an excellent starting point of robust experimentation and manipulation. Some of the most prevalent paradigms in ecology have been derived from or best supported by experiments in the rocky Intertidal. These include excellent demonstrations of the Intermediate Disturbance Hypothesis of species diversity (Souza, 1979), and the introduction (Paine, 1969) and further elucidation (Menge et al., 1994) of the Keystone Species hypothesis of community maintenance.
It has been fairly well demonstrated that the worldwide distributions of species are mediated by abiotic factors (Sanders, 1968, Longhurst, 2007). However, just which factors these are and what values are acceptable or prohibitive remains relatively mysterious (Zacharias and Roff, 2001). Also lacking is a more intermediate scale of data. Most Intertidal diversity analysis has dealt with small scale distributions of sessile species, while few have attempted to extrapolate effects over more regional scales, on the order of hundreds to thousands of kilometers (Zacharias and Roff, 2001, Ebert and Russell, 1998). Recruitment to the substrate is a very important event for the life and therefore distribution of these sessile species. Physical factors can heavily influence this process, in that certain rates of flow are unacceptable for some larvae to settle, and they actively choose to go else where (Larsson and Jonsson, 2006), and rock formations of the Intertidal may strongly affect the flow speed and power of the impacting waves (Abelson and Denny, 1997).
Our observation and its prescribed experiments are directed at elucidating the link between community composition and physical factors, particularly wave stress and substrate type, in the rocky Intertidal. Through these measurements, we hope to show the controlling effects of the physical environment on recruitment, and therefore adult population structure, in our test area.
Pattern 2/2
Through many trips to the Intertidal, zonation patterns become apparent. The first pattern observed is the vertical stratification based around exposure time, where barnacles merge into mussels, and then into colonial organisms as you go further into the lower tidal zones. However, there are subtler patterns here. Upon close inspection, it becomes apparent that different cohorts of organisms are living on the rocks at different locations. It appears that more colonial organisms are attached at the bottoms or in the crevices of the rocks. It also appears that more arthropods and mollusks live on the most wave exposed parts of the rocks, while algaes often are attached to the tops. This zonation often occurs over very small scales of distance, and therefore implies minute changes in the environments these organisms are occupying. This observation was the basis for our study.
Figure 4/4
Figure 1: please note the beautiful curvature, voluptuous trends, and sensual specificity.
Goal 2/2
The goal of this experiment is to determine the effects, if any, of the substrate in the inter-zone on the settlement of sessile species with a planktonic larval stage. In particular, this experiment will test the effect of substrate type on species composition and angle of inclination of the substrate on species diversity.
Hypotheses
General Hypothesis I. The first hypothesis of this experiment is that substrates which exhibit different angles of inclination to the waves will possess different levels of diversity.
Specific Hypothesis 1. Substrates that possess a 45 degree angle of inclination will experience a greater diversity of settling, sessile species than substrates at the more extreme angles of 0 and 90 degrees. This result seems most likely to occur due to the fact that a substrate at a 45 degree inclination would likely experience intermediate amounts of wave action. According to the Intermediate Disturbance Hypothesis, the middling amount of perturbation will prevent both r-selected (poorly competitive, early colonizing) and K-selected (successfully competitive, late colonizing) species from dominating the system. Thus, the coexistence of K-selected and r-selected species will give the substrate at a 45 degree angle to the waves, the greatest amount of diversity.
Specific Hypothesis 2. Substrates with angles of inclination of 0 and 90 degrees will possess less species diversity than substrates with an angle of inclination of 45 degrees. Substrates at 0 degree inclination to the waves will rarely experience direct wave bombardment; instead, waves will merely roll over these areas, with little harsh impacts on the organisms. Therefore, K-selected species should dominate these substrates. Conversely, at substrates with a 90 degree angle of inclination, the wave action should cause constant disturbances that would allow r-selected species to dominant. In both causes, either r- or K-selected species would out-compete the other and come to dominant the substrate, leader to lesser diversity at these two extreme angles of inclination.
General Hypothesis II. The second hypothesis of this experiment is that different types of substrate will exhibit differences in the varieties of sessile species with settling planktonic larvae.
Specific Hypothesis 1. Substrates composed of granite, an igneous rock consisting of many pits and cracks, will exhibit different types of settling species than either sandstone or quartzite. This discrepancy should occur because the more jagged granite will be an ideal settling substrate for different types of larva than the sandstone or quartzite, which display different physical features. Larva may choose to settle on granite, or may just be incapable of settling on the other types of rock, but the result will still be a population consisting of different types of sessile species on the granite substrate.
Specific Hypothesis 2. Substrates composed of sandstone, a sedimentary rock consisting of a flat, smooth surface, will exhibit different types of settling species than either granite or quartizite. Again, settling planktonic larva of certain sessile species, different from the species that preferred the jagged, pitted granite, will either be attracted to or best able to settle on the smooth, even surface of the sandstone, causing a discrepancy between the types of species settling on the granite, sandstone, and quartzite.
Specific Hypothesis 3. Substrates composed of quartzite, a metamorphic rock consisting of flat, smooth portions and pitted, cracked portions, will exhibit sessile settling species that differ from both the sandstone and the granite substrates. With its variety of surfaces, species that may dominant the entirety of the sandstone or granite substrates will not be able to completely out-compete other species due to the lack of appropriate substrate texture on which to settle. Therefore, weaker, but more generalist competitors may be able to settle on this substrate, giving the quartzite a different composition of settling sessile organisms than the granite and sandstone substrates.
MATERIALS AND METHODS
Species Description 4/4
The rocky Intertidal is a diverse home to several different sessile species all competing for the substrate space we will be testing. In particular we will be testing the recruitment of several different phyla. Gastropoda, the phylum containing mussels, and in particularmytilus californianus, one of the most common species found in the monteray bay rocky Intertidal and will no doubt play a large role in our results. Barnacles (infraclass Cirripidia) are another competitive dominant species in the rocky Intertidal and represent the phylum Arthropoda. Other species include sea anemones(Cnidaria) and several species ofBryozoans. We suspect that there will be a large representation of flora in these results and will be looking at the colonizing behaviors of two types of algae Rhodophyta and Chlorophyta. Mobile predators such as Pisaster ochraceous and Acanthina punctulata are a threat to our study and as such we will be using fences around our testing areas. We will only be testing the recruitment after a short period of time, to avoid the effects of the ensuing competition for space.
Site Description 4/4
Our experimental site is coast of central California, particularly in MontereyBay. This area possesses a temperate climate, with little rainfall, with the peak of the hydrograph falling during the winter months (January to March). These experiments will be conducted during the middle of April, a period of strong upwelling along the coast, which helps drive the phytoplankton bloom and therefore recruitment (Longhurst, 2007). The test site is the rocky Intertidal, which, as the name implies, consists of hard, rocky substrates in an area that remains underwater during high tides, but is exposed at low tides. The experiments will all be conducted at mean tide level. The areas utilized for the experiments will be exposed rocky coast, with a consistent angle of wave impact to the test shoreline. A strip of the inter-tidal as long as necessary to obtain enough plots for each experiment plus that experiment’s replicates, will be utilized.
Methods
Our specific hypotheses are not mutually exclusive and because of thiswe will be using the same general setup for our experiment.
Specific Hypothesis 1. Substrates that possess a 45 degree angle of inclination will experience a greater diversity of settling, sessile species than substrates at the more extreme angles of 0 and 90 degrees due to an intermediate amount of wave action.
In order to test this hypothesis, we will be setting up poles in the mean tide level with 1sq meter plates of our different substrates, quartzite, granite, and sandstone. Each of these poles will be at one of our three testable angles (0, 45, 90) and each angle will have 5 replicates in each testing area resulting in 45 testable sites. This will allow us to experimentally change the amount of wave action on the substrates. In order to control for the effect of having the substrates on poles, we will also be testing the various angles in the rocky Intertidal itself, securing the substrates in spots all along the Intertidal with the same angles of inclination as the poles. This will result in another 45 testing sites, being 3 angles represented by each of 3 substrates, with 5 replicates of each combination. In order to control for the effects of the experimental substrate types, we will be clearing 1sq meter sections of the actual rocky Intertidal and testing these areas at the three inclinations. Finally, to test for the control substrate in the rocky Intertidal we will have a set up of the Intertidal substrate on a pole, resulting in 30 more testable sites. In total, we will have 120 testable sources of data to work with. Each testing site will also be equipped with a wave force transducer to record the amount of force the site is receiving from wave impact (Denny 1982). With the readings from the transducers, we will be able to calculate the exact amount of force each site is receiving and disprove or fail to disprove our first two specific hypotheses.If the impact force of the waves increases with the angle of the tests, and when wave force is graphed against species richness, a intermediate disturbance is shown to yield the highest species richness, we will reject the null hypothesis.
General Hypothesis II. The second hypothesis of this experiment is that different types of substrate will exhibit differences in the varieties of sessile species with settling planktonic larvae.
The different substrates will be tested at the same time and the data will show whether substrate makes a difference in species composition, if we see a statistical difference in species richness on each of the different types of substrates. We will set our critical p-value at .05, and if there are tests who, when compared against other tests within their specific hypothesis yield p-values higher than .05, we will fail to reject the null hypothesis for those tests.
BIBLIOGRAPHY
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Denny, M. 1982. Forces on Intertidal Organisms Due to BreakingOcean Waves: Design and Application of a Telemetry System.Limnology and Oceanography27 (1), 178-183.
Ebert, T.A., Russell, M.P.1998. Latitudinal Variation in Size Structure of the West Coast PurpleSea Urchin: A Correlation with Headlands. Limnology and Oceanography 33 (2), 286-294.
Larsson, A.I., Jonsson, P.R. 2006. Barnacle Larvae Actively Select Flow Environments Supporting Post-Settlement Growth and Survival. Ecology 87 (8), 1960-1966.
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Menge, B.A., Berlow, E.L., Blanchette, C.A., Navarrete, S.A., Yamada, S.B. 1994. The Keystone Species Concept: Variation in Interaction Strength in a Rocky Intertidal Habitat. Ecological Monographs 64 (3), 250-286.
Sanders, H.L. 1968. Marine Benthic Diversity: A Comparative Study. The American Naturalist, 102 (925), 243-282.
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Paine, R.T. 1969. A Note on Trophic Complexity and Community Stability. The American Naturalist103 (929), 91-93.
Zacharias, M.A., Roff, J.C. 2001. Explanations of Patterns of Intertidal Diversity at Regional Scales. Journal of Biogeography 28 (4), 471-483.