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Name:
Tutor:
Date:
Subject:
Environmental Biology
Title
Comparison of correlations between environmental characteristics and stream diatom
assemblages characterized at genus and species levels.
Division of Science & Environmental Policy, California State University Monterey Bay, Seaside,
CA, USA.
Abstract
The document presents an attempt to methods of measuring the degree of correlation between
variables in an ecosystem. The methods used here depend on the combination of knowledge of
the level of correlation between diatoms and the other variables within the system that has a
causal relation. The introductory part gives an overview of the background study of diatom
existence in the United States and hypotheses guiding this study. Data collection methods
included sampling, interviews, and questionnaires that guided the study to obtain results
analyzed and represented in numeric tables and graphs. The results are summed up in a
conclusion that gives remarks about the findings of the study.
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In biological and environmental sciences, one often has to encounter with various
characteristics or situations with a significant correlation because of a complex of interesting
uncontrollable and obscure causes. The degree of correlation between variables can be measured
by well-known methods. Diatoms are photosynthesizing materials, that contains a siliceous
skeleton (frustule) and exist in every aquatic habitat including the entire marine environment, in
fact almost anywhere moist. Biological surveys of stream communities have long been used to
assess the impacts of human activities on receiving waters (Whitton and Kelly 1995, Lowe and
Pan 1996, Stoermer and Smol 1999, Stevenson and Smol 2001). This survey of biological
assessment programs was carried in the United States and reported that thirty-nine States relied
on biological information in stream assessments, but only 27 states used this information in
setting water-quality criteria (Davis et al. 1996, Kroeger et al. 1999).
H1: there are more diatoms in the deep oceans of United States (x) than in the shallow oceanic
areas of United States(y)
X>Y
YH0: There will be no difference in the size of populations of diatoms between the deep (X) and
shallow (Y) areas.>
X = Y
Methods
Data used in analyses were compiled from the United States Environmental Protection
Agency’s Environmental Monitoring and Assessment Program (EMAP) surveys of
MidAppalachian streams conducted from 1993 to 1995 (Hill et al. 2000). Species were collected
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from forty-five rivers in 1993, 46 in 1994, and 108 in 1995. More than 10% of the rivers were
selected for the sampling process near the beginning and the end of the sampling period to
examine the diatom metric stability. However, data were gathered from nine hundred and ninety-
nine during 233 site study. The traits from each stream site included nineteen streams chemistry
variables, 13 stream habitat variables, and 15 land-use variables. Diatoms were collected from
erosional habitats at each of nine transects along the river reach, made into a single sample for all
the rivers, and brought back to the laboratory for processing (Hill et al. 2000). Environmental
preferences of the diatom species were taken from published research (Lowe 1974, van Dam et
al. 1994).
Research methodology
The project will be executed through the collection and collation of information and data
from the following sources and methods;
• Literature Reviews: This entails visiting libraries and consulting relevant literature on the
project design.
• Case Studies: This required a physical or virtual visit to existing xeriscapes to ascertain
what is required, what is provided for, and what is lacking.
• Interviews: This involved asking investigative questions of persons who are
knowledgeable and well versed with xeriscape landscapes.
• Internet sources: This means getting data from the world-wide web or network of
computers.
The research methods employed included data collection, data processing, data analysis
and methods to evaluate the accuracy of the results obtain to minimize the occurrence of
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errors. The research method involved observation checklists, utilization of secondary data,
sampling, administration of structured interviews and questionnaires and photographs.
Figure 1photo of people performing transects
Results
The sampling process involved forty-four genera and 522 species of diatoms from the study
streams (Table 1). Fifteen genera were represented by a single species; another ten genera had,
five species. Ten genera had .10 species, with Navicula (119 species), Nitzschia (66),
Table 1 Diatom genera, number of species (including varieties), and environmental preferences (based on average scores for
species within a genus) for Mid-Appalachian streams.
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Achnanthes (48), and Eunotia (44) being the most species-rich (Table 1). Canonical correlation
analyses of the genus- and species-level attributes and the environmental variables resulted in
significant canonical axes. A description of a nutrient-enrichment/stream-size gradient entails the
2nd canonical axis (W2), which was positively correlated with nutrients (total P and total N), Cl-,
total suspended solids, fine-grained stream sediments, and agricultural land utilization, and
negatively correlated with river width and depth (Table 2). Generic richness in any specific river
ranged from 3 to 17, with a mean of 11 genera per stream, whereas species richness ranged from
10 to 72 with an average of 34 species per stream. Genera richness was significantly correlated
with species richness. Acidobiontic diatoms presented zero percent to ninety-nine percent of both
the genus- and species-level counts, and both genus- and species-level traits were similarly
correlated with the selected environmental variables (Table 3). Both genus- and species-level
traits were significantly correlated with W1, the human disturbance/geomorphology gradient.
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The relative abundance of eutraphentic taxa revolved between zero percent to fifty-six percent of
the genus-level counts and from zero percent to ninety percent of the species-level counts, and
genus-level counts were significantly correlated with the species-level count.
.
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Figure 2: Comparisons of diatom taxa abundance (A), , and acidobiontic (C), motile (b), and pollution-
tolerance (c) attributes based on genus and species counts in streams in the MidAppalachian region of the
United States.
A
B
C
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Discussion
A simple measure of the reliability of genus level attributes as an alternative to species-
level attributes is the correlation between attributes based on diatom counts at the two taxonomic
levels. Perfect correlations (r 5 1.00) would suggest that there is no loss of information, for the
measures presented, by limiting identifications to the generic level. Genus- and species-based
attributes were significantly correlated, suggesting that for a reason diatom identification only to
genus may adequately characterize the diatom assemblage’s response to environmental
conditions. For those diatom assemblage attributes in which genus-level counts are highly
correlated with species-level counts (acidobiontic and motile attributes), it appears that genus-
level counts may suffice. Deviations from perfect correlations have simple explanations, and
their impacts on our assessments may be small. For example, the close agreement between
genus- and species-level counts of acidobiontic diatoms reflects the fact that most acidobiontic
species are in genera that are also classed as acidobiontic (Eunotia, Frustulia, Pinnularia,
Tabellaria). Exceptions to this fact include acidobiontic species in genera not classified as
acidobiontic: Achnanthes (1 sp.), Anomoeoneis (2), Aulocoseira (2), Cymbella (2), Fragilaria
(1), Navicula (5), Neidium (1), Stenopterobia (1), and Surirella (1). The impact of excluding the
above species from the genus-level assessment of acidobiontic diatoms can be determined only
by species-level counts, but the near-perfect correlation of the genus- and species-level attributes
suggests that this discrepancy is small.
Conclusion
Conclusions our results support four general conclusions. First, richness attributes are not
consistently or predictably related to gradients of human disturbances within a catchment and
should be used cautiously for environmental monitoring. Second, diatom assemblage attributes
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based on genus or species sensitivities and tolerances to environmental conditions, even based on
European Diatom autecology, are consistently and reliably related to gradients of human
disturbances within a catchment. Third, genus-level diatom assemblage attributes for some
environ 308 Volume 20 B. H. HILL ET AL mental gradients are predictable and appear to be
relatively precise compared to species-level attributes. Fourth, the environmental gradients with
which genus-level diatom assemblage attributes are most strongly correlated are those gradients
that involve morphological (motility) or physiological (pH tolerance) adaptations that are related
to evolved genus-level characteristics.
References
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Charles, D. F. 1985. Relationship between surface sediment diatom assemblages and lake water
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Ecology 66: 994–1011. Chessman, B., I. Growns, J. Curry, AND N. Plunkett-Cole. 1999.
Predicting diatom communitiesat the genus level for the rapid biological assessment of
rivers.
Freshwater Biology 41:317–331. Crossey, M. J.,and T. W. LA Point. 1988. A comparison of
periphyton structural and functional responses to heavy metals. Hydrobiologia 162:109–
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