Ecology & Quadrat Sampling
In Unit Four of Biology 1122, we study Ecology and ecosystems and look at the interactions between the abiotic and biotic factors involved. Abiotic factors include nonliving features of the environment, such as temperature, sunlight/shade, wet/dryness, salinity, etc. Biotic factors include all living things in the environment and involve such relationships as predator/prey and parasitism/symbiosis, etc.
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In this experiment we explored the small but diverse ecosystems at Spittal Pond, a nature reserve in Bermuda (see map above), and looked at how the biotic and abiotic factors contribute to the biodiversity in each ecosystem. There are several identifiable ecosystems (i.e. communities of living organisms and the abiotic components interacting to create a whole system) within Spittal Pond Nature Reserve, including grasslands, rocky shore, brackish pond, lowlands and woodlands.
The different levels of biodiversity present in each ecosystem at Spittal Pond are due in part to the different abiotic factors affecting them.
Along the rocky shore, there is high salinity both in the water and on the rocks due to spray and tides, full sunlight, no soil, high winds, and limestone formations. In the lowlands, just farther in from the shore, there is some soil and sand, lower salinity, part sun/shade, and wind barrier due to the raised limestone formations.
These conditions either limit or enhance the flow of energy, water and essential minerals to the living organisms there and thus help control the biodiversity possible in these environments. Biotic factors such as photosynthetic organisms, decomposers and competing life forms then further affect the success or failure of other biotic components.
The different levels of biodiversity present in each ecosystem at Spittal Pond are due in part to the different abiotic factors affecting them.
Along the rocky shore, there is high salinity both in the water and on the rocks due to spray and tides, full sunlight, no soil, high winds, and limestone formations. In the lowlands, just farther in from the shore, there is some soil and sand, lower salinity, part sun/shade, and wind barrier due to the raised limestone formations.
These conditions either limit or enhance the flow of energy, water and essential minerals to the living organisms there and thus help control the biodiversity possible in these environments. Biotic factors such as photosynthetic organisms, decomposers and competing life forms then further affect the success or failure of other biotic components.
Hypothesis
The purpose of this experiment is to investigate how the abiotic factors in the various environments of the nature reserve affect the types of organisms present and their population densities. We believe that due to certain abiotic factors on the rocky shore, such as high salinity, lack of soil and high winds, this environment will support significantly less biodiversity than the lowlands only a few meters inshore. The lowlands in contrast have life-supporting features such as soil, low/moderate salinity and protection from wind and salt spray.
The purpose of this experiment is to investigate how the abiotic factors in the various environments of the nature reserve affect the types of organisms present and their population densities. We believe that due to certain abiotic factors on the rocky shore, such as high salinity, lack of soil and high winds, this environment will support significantly less biodiversity than the lowlands only a few meters inshore. The lowlands in contrast have life-supporting features such as soil, low/moderate salinity and protection from wind and salt spray.
Materials
Transect (Quadrat)
Tape Measure
Data table
Camera
Transect (Quadrat)
Tape Measure
Data table
Camera
Methods
In order to estimate the population sizes of various species in these two environments, we used the Quadrat/Transect Sampling method, where the area/environment to be studied is narrowed down a measured 100 square meter area. The transect was then placed randomly inside this area three times, and each time, the number and coverage of each species within the transect was noted. This gives a random sampling which is a good estimation of the population densities for the whole area.
In order to estimate the population sizes of various species in these two environments, we used the Quadrat/Transect Sampling method, where the area/environment to be studied is narrowed down a measured 100 square meter area. The transect was then placed randomly inside this area three times, and each time, the number and coverage of each species within the transect was noted. This gives a random sampling which is a good estimation of the population densities for the whole area.
It is essential to choose random sites within the chosen environment in order to get an unbiased sampling of the populations there. In order to do this, we stood with our backs to the area and tossed the transect behind us, then observed and counted the species where it landed.
Results
In each environment, we found several species of living organisms. However, there was very little overlap, if any, of the kinds of organisms present. On the rocky shore, we found mostly animals, such as small hermit crabs, chiton and fish, and only one type of photosynthetic organism - moss. In the lowlands, we found only plants, such as grasses, flowering plants (nasturtium, Bermudiana, etc.) and other common coastal plants.
The total number of species in the Lowlands exceeded that in the Rocky shore by 4 (four) species.
In each environment, we found several species of living organisms. However, there was very little overlap, if any, of the kinds of organisms present. On the rocky shore, we found mostly animals, such as small hermit crabs, chiton and fish, and only one type of photosynthetic organism - moss. In the lowlands, we found only plants, such as grasses, flowering plants (nasturtium, Bermudiana, etc.) and other common coastal plants.
The total number of species in the Lowlands exceeded that in the Rocky shore by 4 (four) species.
Conclusion
In conclusion, our findings show that there is indeed an increase in biodiversity in the lowlands versus the rocky shore. There is no obvious dominant plant species within the lowlands, as multiple plants compete for sunlight and soil space (both abiotic factors necessary for survival). Each transect area showed different population densities than the next. While one area was almost completely covered with nasturtium, the other two were absent of that species.
In the rocky shore area, the only plant-like organism found was moss growing on the limestone formations. The dominant animal species appears to be tiny hermit crabs living in the tide pools there.
Sampling animal populations proves somewhat difficult with the quadrat sampling method, as animals such as ants or bees may be present, but will be moving and often out of sight, and therefore hard to quantify. We would guess that both of these organisms were actually present in the lowlands area, but were not observed within the quadrats. Should they have been included in our observations, they would add to the biodiversity in the lowlands environment and further support our hypothesis.
The abiotic factors on the Rocky Shore, such as high salinity, high winds, no soil, and tidepools are the right components for the growth of moss/algae, small fish, mollusks and crabs. These factors, however, inhibit the growth of plants which need soil, low salinity, some shade and protection from high winds and salt spray. Thus, the biotic (living) components of this environment are dictated by the abiotic factors above.
In the lowlands, abiotic factors included some sun and some shade, low/moderate salinity, some soil, and protection from high winds, tides and salt spray. These factors allow for the survival of various coastal plants such as those we found - nasturtium, sea oxide, Bermudiana, New Zealand spinach, etc. In turn, in this environment without the tidepools of salt water, none of the animals from the rocky shore could survive. Again, the abiotic factors are an essential component of the ecosystem, controlling what organisms can thrive there.
In conclusion, our findings show that there is indeed an increase in biodiversity in the lowlands versus the rocky shore. There is no obvious dominant plant species within the lowlands, as multiple plants compete for sunlight and soil space (both abiotic factors necessary for survival). Each transect area showed different population densities than the next. While one area was almost completely covered with nasturtium, the other two were absent of that species.
In the rocky shore area, the only plant-like organism found was moss growing on the limestone formations. The dominant animal species appears to be tiny hermit crabs living in the tide pools there.
Sampling animal populations proves somewhat difficult with the quadrat sampling method, as animals such as ants or bees may be present, but will be moving and often out of sight, and therefore hard to quantify. We would guess that both of these organisms were actually present in the lowlands area, but were not observed within the quadrats. Should they have been included in our observations, they would add to the biodiversity in the lowlands environment and further support our hypothesis.
The abiotic factors on the Rocky Shore, such as high salinity, high winds, no soil, and tidepools are the right components for the growth of moss/algae, small fish, mollusks and crabs. These factors, however, inhibit the growth of plants which need soil, low salinity, some shade and protection from high winds and salt spray. Thus, the biotic (living) components of this environment are dictated by the abiotic factors above.
In the lowlands, abiotic factors included some sun and some shade, low/moderate salinity, some soil, and protection from high winds, tides and salt spray. These factors allow for the survival of various coastal plants such as those we found - nasturtium, sea oxide, Bermudiana, New Zealand spinach, etc. In turn, in this environment without the tidepools of salt water, none of the animals from the rocky shore could survive. Again, the abiotic factors are an essential component of the ecosystem, controlling what organisms can thrive there.