Waterose Lab Introduction: Biodiversity in a Salt Marsh


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The Effects of the Proximity of the Marine Environment

on Biodiversity in Microhabitats within a Salt Marsh

by Waterose

Section 1. Introduction:

The hypothesis tested the edging effects of the proximity of the ocean on the biodiversity of the flora in three microhabitats in a salt marsh. The salt marsh is transversed by a fresh water stream. The number of species, as a measure of biodiversity, was compared between three different microhabitats. These were located at the marine edge, the fresh water edge, and the mixed water edge, which was located between the other two microhabitats. The salt marsh is a transition zone from the Esquimalt Lagoon to the Coastal Douglas-fir ecosystem which forms a component of the temperate rainforest on the coast of British Columbia. The one-hectare study plot is located on the property of Royal Roads University near Victoria, BC. The methods used to set up the plot were based on the design protocols of the joint Smithsonian Institute and Man and the Biosphere program of United Nations Educational, Scientific and Cultural Organisation (UNESCO). The study plot was further divided into twenty metre subquadrats, and random one metre quadrat samples were obtained from each of the microhabitats to identify the species within each of the microhabitats. The Anova analysis compared the differences between the three microhabitats and the T-test analysis compared the differences between each pair of the microhabitats.

The Anova analysis indicated that there was a significant difference between the mean number of different species between the microhabitats. The T-test analysis indicated that the lowest diversity occurred at the edge of the lagoon, and the highest diversity occurred furthest from the marine edge in the fresh water edge microhabitat. There was a significant difference in the biodiversity between the marine edge and the middle edge microhabitats, but there was no significant difference between the middle edge and the fresh water edge microhabitats. The trend was that biodiversity increased in a transverse from the lagoon edge inland to the freshwater edge.

The number of species within a defined study area is only one method of comparing biodiversity. The relative abundance of species should also be considered when analysing biodiversity issues. This could be accomplished by considering the percent cover of microflora and the relative abundance of soil fauna.

1.2 Introduction:

The nature of ecology is much more than a snapshot of the numbers of species in time. The spatial patterns of different organisms, their relative abundance, and their interactions with the ecosystem environment over extended periods of time provide deeper insight to gain an ecological understanding of biodiversity. The disturbance of habitat by natural succession or anthropogenic development can alter biodiversity and population distribution. The issue of sustainable development attained global importance with the Brundtland Commission report in 1987, Our Common Future (Rogers, 1993). Shortly thereafter, the 1992 Earth Summit meeting in Rio de Janeiro featured a global gathering of nations to wrestle with environmental concerns. The preservation of biodiversity is a global responsibility and Canada is a signatory to the 1992 Convention on Biological Diversity. The preservation of the temperate rainforests in Canada is just as important as the preservation of the tropical rainforests in Brazil, both of which are being decimated at an alarming rate. Large old growth rainforests have received a lot of public attention in BC; however, little is understood and documented about micro-organisms and microhabitats. They, too, are an integral component of our environment and they provide valuable services such as nutrient recycling, ecosystem stability, and water cleansing.

There are unique and rare ecosystems on Vancouver Island including the Coastal Douglas-fir ecosystem and highly productive saltmarshes; both are threatened by habitat disturbance and encroachment by anthropogenic development. The first step in protecting biodiversity is in knowing exactly what there is to protect. This is accomplished by completing inventories of existing biodiversity. Nature, however, is not static; nature is continually evolving and changing and, ongoing monitoring of existing species is critical to understanding changing ecological trends.

Royal Roads University (RRU) is participating in a long-term ongoing Ecological Monitoring and Assessment Network (EMAN) plan under the supervision of Environment Canada. The primary ecological inventory of the flora was completed in 1995 by Madrone Consultants and is referred to as the Madrone Report (Madrone, 1995).

RRU is broadly described as a Coastal Douglas-fir (Pseudotsuga menziesii) zone, with a moist maritime subzone biogeoclimatic ecosystem classification. The climate is moderated by the Pacific Ocean. The west coast of Vancouver Island receives high amounts of annual rainfall; RRU receives approximately one thousand millimetres of annual precipitation (Madrone, 1995). The broad classification contains a significant number of microhabitats within the RRU property boundaries.

The geologic history of the region is bedrock of early Eocene lavas (Madrone, 1995). This area was glaciated during the Fraser glaciation and subsequently, the bedrock was overlain with glacio-marine and fluvio-glacial till and sands forming a marine deltaic environment. The dominant soils are podzols in the forest areas and gleysols in the marine areas. The combination of different soil types, mountainous terrain, and proximity to the ocean create a wide venue of ecological landscapes.

Subsequent to the Madrone inventory, two study plots have been established on the property of RRU; one is located in a transition zone between an upland field and a mixed red cedar (Thuja plicata) /Douglas-fir (Pseudotsuga menziesii) forest, and the other is located in a transition zone between a rare saltwater marsh and a mixed Douglas-fir forest.

The saltwater marsh borders the Esquimalt Lagoon which is flushed by the ocean at a narrow inlet. The lagoon supports a wide diversity of species, including bivalves, avifauna, fish, and even a dead porpoise was observed on the beach at the mouth of the inlet. The biodiversity of the saltmarsh ecosystem is vulnerable to encroachment by non-indigenous flora species such as the Spartina saltmarsh grass which can invade shallow marine ecosystems and displace entire communities.

The saltmarsh features a wide range of birds and bird habitat, including large snag trees which are unique habitat to eagles and other large birds. This area has been designated as a bird sanctuary and is important to both migrating waterfowl and indigenous aviary species. The marsh is transversed by a small freshwater stream creating an estuary environment at the mouth of the stream and has been known to support spawning fish and river otters.

The study of saltmarsh ecosystems is extremely unique because there is a significant mixing of saline water and fresh water with the tidal flux. A non-mobile species must be very tolerant to withstand extreme changes in moisture and salinity to flourish in this environment. This study examined the biodiversity of the vegetation in the saltmarsh relative to the proximity of the Lagoon.

Three microhabitats were studied within the saltmarsh study plot: the marine water edge microhabitat at the lagoon shoreline; the fresh water edge microhabitat at the stream estuary; and, the mixed or middle water edge microhabitat equidistant between the former two microhabitats. The total distance from outside edge of the marine microhabitat to outside edge of the freshwater microhabitat spanned one-hundred metres, and the total area sampled was thirty square metres. The null hypothesis predicted that there was no difference in biodiversity relative to the marine edging factor; however the null hypothesis was rejected and the study revealed a trend that was opposite to the anticipated results. The hypothesis is described in more detail below in Section 1.3.

1.3 Hypothesis:

The hypothesis tests the differences in flora biodiversity between three types of microhabitats in the saltmarsh ecosystem. The null hypothesis is:
H_O: There is no difference in flora biodiversity between the marine water edge, fresh water edge, and mixed water edge microhabitats in the salt marsh.

If the null hypothesis is not accepted at the 95% level of certainty, the alternate hypothesis is:
H_A: There is a difference in flora biodiversity between the marine water edge, fresh water edge, and mixed water edge microhabitats in the salt marsh.