 | Ecology of Atlantic Shores Erin Miller, 2008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Home -------------------------- Nahant -------------------------- Narragansett Bay: Introduction Water Quality Methods Observations Results Discussion -------------------------- Bermuda: Introduction Water Quality Coral Disease Aspergillosis Hypothesis and Methods Results Discussion -------------------------- Conclusions -------------------------- References | Introduction
to Rocky Intertidal Data Sampling Techniques Northeastern
The goal of
this trip was to examine the diversity of organisms residing in the rocky
intertidal zone and to become acquainted with common sampling techniques.
Additionally, in order to direct data collection the hypothesis that Littorina obtusada is
more often associated with the brown alga Ascophyllum nodusum than either Fucus vesicilosus or Chondrus crispus was tested. Quadrat sampling was used to
determine percent algal cover in Ascophyllum, Fucus, and Chondrus dominated tidal zones and to determine the density
of L. obtusada,
Littorina littorea, and
Nucella lapillus living in each area.
Quadrat sampling was used to obtain information on the abundance of each snail
species living in each of the tidal zones:
The average abundance of each snail species in each tidal zone can be displayed graphically:
An ANOVA test was used to analyze the data, showing that there was an association between the species of snail and its abundance in the intertidal zone (F2, 24=3.55, P=0.044). Biologically this shows that each species of snail has a different abundance in the rocky intertidal, and the reason for this could be found by further research of the habitat of each species.
This analysis was expanded by conducting separate ANOVA tests for each of the three tidal zones. These three tests showed that there was a relationship between the species of snail and its abundance in the Ascophyllum zone (F2, 6=6.50, P=0.031) but not the Chondrus or Fucus zones (F2, 6=0.832, P=0.480; F2, 6=5.08, P=0.051). This shows that there is a factor of the Ascophyllum zone that caused each species to be distributed differently.
It could be hypothesized that the reason for this distribution is an interaction between the three species such as competition, tolerance of each species to desiccation, or the abundance of each species’ food sources. It can be determined that the high P-value for the Chondrus zone was due the different habitats sampled. Noted in the observations is that quadrat sample five had many rock crevices, accounting for the high number of L.littoria in this sample. Additionally, quadrat sample six had a high abundance of Fucus which the Nucella resided on, increasing the number of Nucella in the area to an abnormal amount. These occurrences caused the data to be skewed, resulting in an insignificant P-value. It is difficult to say that there is no relationship between abundance of each species in the Fucus zone due to a significant P-value of 0.001. Again, this was caused by quadrat sample nine which had zero percent cover of Fucus and therefore resulted in a high number of small L. littoria individuals living in a tidepool. These results could have been avoided by taking more quadrat samples in each tidal zone. Due to the quality of the data obtained, it cannot be determined whether the data collected for the Chondrus and Fucus zones exhibits a significant distribution. When testing the hypothesis, three graphs can be formed to compare the abundance of L. obtusada in each tidal zone:
In each graph it seems as if the trend is that as percent cover increases the abundance of L. obtusada increases. This data can be analyzed further using correlation tests, which support that there is a positive correlation between percent cover and abundance of L. obtusada. The tidal zones can be tested separately to determine if L. obtusada is more associated with a certain algal species.
The correlations between percent cover of each algal species and L. obtusada does not support our hypothesis that L. obtusada is more often associated with Ascophyllum than either Fucus or Chondrus. All tests had positive correlations, with Chondrus being the highest and Ascophyllum in a very close second. Again, it can be stated that our data was flawed due to low numbers of quadrat samples. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
