The correlation of chitons to the entire invertebrate community along the low, middle and high tide zones
California State Polytechnic University, Pomona
Vertical zonation of organisms within intertidal communities is defined as a result of biological and physical stresses consisting of dessication, predation, competition, herbivory, predation, and wave action. The analysis studied the zonation of a community based on the correlation of chiton to invertebrate abundance along the low, middle and high intertidal zones of Laguna beach of California, where a 50m baseline transect with 25ft perpendicular transect were laid down to stratify the sample zones. Density was measured by based count method and percent coverage to estimate the abundance of species such as chitons, barnacles, mussels, and algae in each plot. It was found that there’s no correlation between chitons and species among the intertidal community despite popular beliefs. This suggests that the abiotic factors administers a stronger control on distribution than biotic factors such as intertidal interaction.
The intertidal zone is segregated into the high-tide zone, middle-tide zone, and low-tide zone. The high intertidal zone consists of mostly terrestrial terrain and minimal water coverage. The mid-intertidal is commonly exposed to air and submerged by incoming tides. Positions closer to the sea are called the low intertidal zone, which is only exposed to air during low tide and constantly submerged underwater. Due to contrasting exposures of intertidal zones, the abundance and diversity of life are affected by abiotic and biotic factors.
An organism’s capacity to withstand abiotic factors such as desiccation for instance, regulates their upper limits, whereas biotic interactions such as predator or competition draws lines of lower limits (Doty, 1946). Intertidal organisms like chitons, anemones, barnacles, and green algae inhabit the high-tide zones and usually must endure stresses such as temperature fluctuations, desiccation problems due to lack of water, and changes in salinity. Therefore as adaptations, high intertidal organisms have shells not only against desiccation problems, but also to ameliorate salinity stress. Middle tide zone experiences harsher waves thus steamline shaped organisms such as sponges, barnacles, algae, mussels, and sea stars must prevent dislodgement by waves. These organisms often utilize attachments (i.e tube feet) and their hyperdynamic body plan to decrease surface area, allowing cluster development which assists them to adhere to their habitat. An abundance of complex organisms are found in the low tide zone as well as nutrients, but the rapid changing conditions make survival a challenge, especially with potential predations and space competition. Organisms in this zone, typically sea urchins and jelly fishes, have evolved adaptations such as respiratory structures to improve oxygen carrying capacity or toxin secretion to warn off incoming predators.
There has been suspected research that chitons has the capacity to influence the benthic community of intertidal zonations (Hawkins and Hartnoll, 1983), and the purpose of this study was to determine the correlation between chiton and intertidal invertebrates, and how that shapes vertical zonation of intertidal communities. Specifically, it’s hypothesized that chiton will have a strong correlation to the entire intertidal community, causing negative correlation in algae and barnacles, and positive correlation in water coverage, baseline distance and mussels.
Materials and Methods:
On May 20, 2018, I did an observational study on several organisms including chitin, red algae, barnacles, mussels, etc. at Crescent bay, Laguna Beach California. For sessile organisms such as plants and intertidal invertebrates, the sampling method involved plots and line transects.
The study started off with the setup of a 50 meter baseline transect from high to low intertidal zone. Then incrementally, a 25 feet perpendicular transect was laid down until it reached the end of the baseline transect. The zones were stratified by randomly placing perpendicular transects between 0-48m for a total of 136 plots. A random number table was used to pick where to place the 1 ft by 1 ft square plot, and the following procedures utilized area based counts methods and percent coverage to estimate the number of intertidal organisms.
I used StatCat 3.7.1 to do a D’Agostino-Pearson K2test for normality. Water was normally distributed, but red algae, mussels, barnacles and chiton weren’t normally distributed. I transformed chiton data using square root transformation to ensure normality and equal variances followed by a spearman rank correlation for red algae, mussels and barnacles. Then finding correlation for water coverage, and regression for baseline distance.
Chiton are not significantly correlated with water cover (r=0.219, p;0.05) or algae (rs= -0.301, p;0.05) or muscles (rs=0.086, p;0.05) or banarcles(rs= -0.111, p;0.05), or baseline distance (F=1.838, p;0.05, Figure 1).
Originally, fundamental grazers like Chitons were hypothesized to have strong interactions and correlations to the algae assemblages, abundances, and the whole intertidal invertebrate community since they eat algae, diatoms, barnacles, and sometimes bacteria. However by the results and graph, the chiton assemblage had no real effects on intertidal colonization and abundance of algae as the correlations to water coverage, algae, mussels, barnacles and baseline distance is not statistically significant; therefore the hypothesis is disproven. Chitons were more abundantly found in the high intertidal zone due to higher salinity levels, but their ability to withstand abiotic factors allows them to segregate along the zones. Chitons typically prefer green algae, thus the weak negative correlation found with red algae may be due to the negative effects of herbivory and competition (Duggins and Dethier, 1985). Chiton is resourceful in managing algae growth and distribution, explaining for the inverse relationship between algae and chitons (Mendonca et al, 2015). Although they both consume algae, barnacles are filter feeders whilst chitons are grazers, so the competition for living space accounts for the weak negative correlation (Duggins and Dethier, 1985). These results concludes that all of these organisms and water are all within the same area and have possible interactions but no significant interactions with one another. Comparatively, few studies illustrate that intertidal interactions and competition realistically wouldn’t be as applicable in constructing vertical zonation, but more so the repercussions of biological factors in setting distribution limits (Doty, 1946).
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