The effects of human activities on the populations of attached organisms in intertidal rocky shore
Date Issued
2011
Date
2011
Author(s)
Lee, Tsung-Han
Abstract
The aim of this study is to investigate effects of artificial structures and human trampling on attached organisms in intertidal rocky shore. The intertidal attached organisms on breakwaters, seawalls and natural rocky shores were studied in Linshanbi and Houcuo Harbour, North coast of Taiwan. To assess the generality of patterns through four seasons, natural and artificial habitats were sampled at September 2010, December 2010, March 2011 and June 2011. We also measured several seawater parameters at each sampling site at December 2010, March 2011 and June 2011. Furthermore, we selected two types of rocky intertidal platforms, andesite rock and algal reef, in the Qianshui Bay near Houcuo Harbour. There are ten rocks for each rock type and three quadrats with different trampling treatments on each rock. The trampling treatments were used 0, 125 and 500 footsteps per 100cm2 per month on different quadrats for each rock from June 2010 to November 2010. Observations were made on attached organisms at the end of each month during trampling treatment as well as 1, 3 and 6 months after the last of trampling treatment. The data were analysed by Bray-Curtis similarity, non-metric multi-dimensional scaling (n-MDS), ANOVA, principal component analysis, correlation coefficient and BIO-EVN, in order to test the temporal and spatial variations of the attached organisms and seawater parameters. Biodiversity Index, such as species dominance (Simpson Index), species diversity (Shannon-Wiener’s index of species diversity) and species evenness (Pielou’s evenness) were calculated to study changes in assemblages after tampling.
There are two main findings. First, attached organism assemblages on seawalls were largely distinct from those on breakwaters or natural rocky shores. There were lower abundance of species at seawalls than breakwaters and natural rocky shores. The attached organism assemblages at breakwaters were similar to natural rocky shores, but the abundance of species at natural rocky shores were higher than breakwaters during the growing season of attached organisms. Besides, changes in the seawater environment produced by the establishment of artificial structures will affect the abundance of attached organisms. In addition, no matter what kind of structures, green algae and invertebrates had greater abundance on unshaded surface, while red algae had greater cover on shaded seawalls.
Second, trampling experiment shows that there were higher species dominance and lower species diversity and evenness at experimental quadrats after trampling treatment. All kinds of organisms reduced to 50% of control values at 500 footsteps per month after three months of trampling treatment. Attached animals declined immediately after trampling started, but they recovered at the end of trampling treatments. By contrast, red algae were resistant to trampling effects in first three months of trampling, but they couldn’t recover after the experiment. Thus it can be seen, human trampling will cause both direct and indirect effects on intertidal ecosystem. For example, percentage cover of sea lettuce (Ulva lactuca) increased after trampling because red algae are difficult to recover from trampling treatments, which compete for settlement space with sea lettuce. As a result, the percentage cover of sea lettuce at experimental quadrats were higher than control values after trampling.
Subjects
intertidal rocky shore
artificial structures
attached organisms
human trampling
biodiversity
Type
thesis
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