Abstract:
In determining the ecological diversity within different stream zones certain abiotic factors are known to have a large influence. Certain macroinvertebrates are affected by abiotic factors which impact the population of fish species, White Sucker and Longnose Dace. The prevalence of these fish species were investigated in pool and riffle stream zones of Butternut Creek in Lafayette, NY. Macroinvertebrates were collected in both zones with the use of kick-nets and classified with taxonomic keys. Fish species were collected using electroshock equipment, and once stunned they were then caught with a net. For both riffle and pool zones water velocity, temperature, and dissolved oxygen readings were taken. After testing for diversity, similarity, and frequency, results expressed that the diversity of certain fish species were higher in a pool stream zone type, and the differing frequencies of fish among zones were statistically significant.
Introduction:
The abiotic factors within this environment were measured due to the significant impact they have on the organisms that inhabit it. The abiotic factors involved in this study include the concentration of dissolved oxygen, water temperature, substrate type, food type, and water velocity. The two separate zones, riffle and pool, were studied at Butternut creek in Lafayette, NY. The pool zones are deep and round with a much lower water velocity that can cause an accumulation of organic matter. A pool, mostly stationary, will attract specific macroinvertebrates such as shredders. Riffle zones have a higher water velocity resulting in a shallow, linear area that does not accumulate as much organic matter as a pool zone. Riffles will attract macroinvertebrates, classified as scrapers, that generally feed on algae retrieved from rocks and bottom surfaces. Interactions among macroinvertebrates and their food resources vary among functional groups. Macroinvertebrates are a good source of food for numerous fish, and have an important influence on the system of a stream (Wallace and Webster, 1996). The two species of fish focused in this study, White Sucker and Longnose Dace, are both affected by these abiotic factors contributing to their presence in a specific stream zone. The Longnose Dace has a pointed nose suitable for the consumption of macroinvertebrates along the banks of a stream and within rocks. This particular species can commonly be found in riffle zone. The White Sucker species, most abundant within a pool zone, consumes organic matter floating on the surface. Multiple statistical tests were performed during this experiment in order to provide evidence that the diversity and frequency of certain fish species will be higher in a pool stream zone. A more thorough comprehension of this experiment requires detailed studies in multiple different stream zones with varying abiotic factors. Major ecological principles to take into account are the effects that nutrients have on an ecosystem. Runoff from fertilizers, sewage discharge, and livestock can all be considered variables with respect to the presence or absence of certain nutrients in water. The purpose of this study was to investigate the differences between both riffle and pool zones of a stream, and gather data relative to the diversity of fish among them.
Materials and Methods:
Studies were performed at Butternut Creek stream site in Lafayette, NY in order to gather data for various ecological characteristics within two stream zones; pool and riffle. Separating into groups, the acquired data consisted of physical characteristics and fauna relative to the stream community. The velocity of stream flow, air temperature, water temperature, and dissolved oxygen readings were measured, as well as a collection of various fish and invertebrates within the two zones.
The velocity of the stream flow for both the riffle and pool was measured using a float method. This method involved recording the time a floatation device takes to travel to a known distance. The time trial was repeated five times in order to gather an average value.
Air temperature was acquired using a thermometer. With the use of probes, the water temperature and dissolved oxygen readings were taken for both riffle and pool. In order to collect fish for both zones groups utilized electroshocking equipment to stun the fish for a short period of time. The fish were stunned briefly and captured in nets to gather information on the diversity of each zone.
Macroinvertebrates were collected in both zones using a kick-net. After pulling the kick-net out of the water, the invertebrates collected were placed into a tray using forceps. Once secured into the tray the group was able to identify each invertebrate with a taxonomic key, and organized into various groups including scrapers, shredders. collector-gatherers, collector-filterers, and predators.
During the following lab-week the data gathered from every section was pooled together and statistically analyzed. The individual data and the pooled data from the week were utilized to conduct multiple statistical tests. These tests included four Chi-square tests of both species (Longnose Dace and White Sucker) for pooled and individual data, as well as calculations of Simpson’s Index of Diversity and Sørensen’s Coefficient of Community Similarity for the pooled data of each zone for the week.
Results:
The Simpson’s Index of Diversity, a unified concept of diversity, was measured in determining if either the pool or riffle zone of Butternut Creek has a higher diversity of fish species. In order to incorporate evenness into the diversity estimate the Simpson’s Index was utilized instead of species richness. The index values of riffle and pool zones were taken, from a pooled set of data among all lab sections, to compare the abundance and evenness of fish species within the two stream zone types. The observations taken suggest that there is only a slight difference in the diversity of fish species within each stream zone (Figure 1). The pool zone resulted in a higher index value.
Figure 1. Contains the Simpson’s Index values for Riffle and Pool Zones at Butternut Creek
The Sørensen’s Coefficient of Community Similarity (CCs) was utilized in the experiment to compare the diversity between the two stream zones in order to quantify their similarity. The pooled value calculated for the entire lab week ranges from 0 to 1, where 0 indicates no species in common and 1 indicates all species in common. Given the varying amounts of organic matter present in each zone, the similarity of fish between the pool and riffle zones will not have many species in common. In calculating a relatively low coefficient value (CCs=0.24), this statistical test suggests that there is a low amount of similarity among the riffle and pool zones of Butternut Creek.
A series of multiple Chi-square (X2) tests were taken in order to evaluate question regarding where more fish were caught, whether or not both species were caught in riffle and pool zones, and whether the difference is statistically significant. All Chi-square tests were taken with 1 degree of freedom at =0.05, displaying 95% confidence that the result is correct. The observed and expected values for the individual lab section, as well as pooled data for the week were recorded for each species in calculating the frequency in a particular stream zone type (Tables 1-2).
Table 1. Individual Data Friday Lab
Species
Observed Riffle Zone
Observed Pool Zone
Expected
White Sucker
0
0
0
Longnose Dace
0
0
0
Table 2. Pooled Data
Species
Observed Riffle Zone
Observed Pool Zone
Expected
White Sucker
1
10
5.5
Longnose Dace
6
0
3
The first Chi-square test was performed, with individual data from lab section 10, in order to indicate that the amount of White Sucker caught will not differ significantly between pool and riffle zones. Observations of the species White Sucker within both stream zone types revealed that the frequency of this particular species (X2=0) was not statistically significant when compared to a table value of (X2=3.841, =0.05). Among both stream zone types there was no significant difference in the frequency of White Sucker fish species (Fig. 2)
The second Chi-square test was performed, with individual data from lab section 10, in order to reveal that the amount of Longnose Dace caught will not differ significantly between pool and riffle zones. Observations of the species Longnose Dace among both stream zone types revealed that the frequency of this particular (X2=0) was not statistically significant when compared to a table value of (X2=3.841, =0.05). Among both stream zone types there was no significant difference in the frequency of Longnose Dace fish species (Fig. 2).
The third Chi-square test was performed, with pooled data from each lab section, in order to indicate that the amount of White Sucker caught will not differ significantly between pool and riffle stream zones. Observations of the species White Sucker with both stream zone types revealed that the frequency of this particular species (X2=5.82) was statistically significant when compared to a table value of (X2=3.841, =0.05). Among both stream zone types there was a significant difference in the frequency of White Sucker fish species for the pooled data (Fig. 2).
The fourth Chi-square test was conducted, with pooled data from each lab section, in order to reveal that the amount of Longnose Dace caught will not differ significantly between pool and riffle zones. Observations of the species Longnose Dace among both stream zone types revealed that the frequency of this particular species (X2=4.16) was statistically significant when compared to a table value of (X2=3.841, =0.05). Among both stream zone types there was a significant difference in the frequency of Longnose Dace fish species for the pooled data (Fig. 2).
Figure 2. Chi-Squared tests for both fish species, pooled/individual data
Important abiotic factors measured that impact organisms within their environment were water velocity, air and water temperature, and the amount of dissolved oxygen in a stream of Butternut Creek. These factors influence the presence of certain macroinvertebrates and fish within a given stream, and zone in particular (Table 3-4). The abiotic factors measured during this experiment determine the activity of dynamic systems such as riffles and pools.
Table 3. Average Water Velocity
Riffle Zone
Pool Zone
Distance Traveled (m)
10
10
Mean Time Traveled (sec)
12.29
49.21
Water Velocity (m/sec)
0.82
0.31
Table 4. Air and Water Temperature, Dissolved Oxygen Percentage
Riffle Zone
Pool Zone
Average Air Temperature (C)
19.83
19.83
Average Water Temperature (C)
14.23
14.22
Dissolved Oxygen (mg/L)
8.7
8.63
Dissolved Oxygen (%)
87.2
86.1
Discussion:
The major findings within this experiment relative to the diversity of fish species within a fast moving riffle and a slow moving pool zone suggest that there was a higher diversity within a pool stream zone. With a Simpson’s Diversity Index value of 7.364, the pool zone expressed a slightly higher diversity among different zones. Slow-water habitats include pools formed by channel scour (eddy pools, trench pools, mid-channel pools, convergence pools) and those formed behind dams. Fish species and macroinvertebrates distinguish among habitats at one or more levels of hierarchy. This hierarchal system of classification assists in the understanding of biotic-habitat relationships in streams and leads to more effective methods of evaluating the effects of environmental change on stream ecosystems (Hawkins et al, 2011). The accumulation of organic matter on the surface of a pool zone leads to more macroinvertebrates, increasing the fish abundance within a pool zone causing this level of hierarchy.
In calculating a Sørensen’s Coefficient of Community Similarity, the determined value of 0.24 was closer to 0 resulting in a relatively low species similarity within riffle and pool stream zones. The differences in species of fish and macroinvertebrates can be caused by a number of abiotic factors, one being water velocity. Pools contain gravel which indicates less disturbance during high flow, resulting in a richer assemblage of certain species. Many invertebrates in pools end up in a pool zone as a result of drift from a preferred riffle habitat, but the presence of gravel provides protection for various species of macroinvertebrates (Brown and Brussock, 1990). The presence of certain macroinvertabrates, shredders and scrapers, in a pool zone feed on algae from rocks and bottom surfaces and leaves that fall into areas of low disturbance. These factors contribute to a relatively low species similarity within the two stream zones.
Another major finding within this experiment was the difference in frequency for both White Sucker and Longnose Dace fish species among the pooled data for all lab sections. Both values for the Chi-square tests revealed a statistically significant difference in the frequency for both zones of a stream. Abiotic factors that would be accountable for this difference in frequency are concentration of dissolved oxygen and water temperature. Waters that are high in dissolved oxygen are very cold and turbulent, and attract certain species of macroinvertebrates, stoneflies and mayflies, that rely on cold fast flowing water to maintain a high concentration of oxygen near their gills or body. Waters with low dissolved oxygen are still and warm, contain midges and dragonflies which carry a small bubble of air next to their bodies for oxygen. These intermediate trophic level consumers are influenced by bottom-up and top-down forces in streams and serve as the conduits by which these effects are propagated. Macroinvertebrates, a very important source of food for fish, have an important influence on nutrient cycles, primary productivity, decomposition, and translocation of materials (Wallace and Webster, 1996).
Conclusion:
Various abiotic factors such as the concentration of dissolved oxygen, water temperature, substrate type, food type, and water velocity are all significant with respect to the presence of specific macroinvertebrates and the fish that feed on them. In determining the density and relative abundance of White Sucker and Longnose Dace, the variation of macroinvertebrates and the accumulation of organic matter are also considerable. A pool stream zone is less turbulent, has a much lower water velocity, and is mostly stationary which attracts shredders. A riffle stream zone has a higher water velocity resulting in a shallow, linear area that does not accumulate as much organic matter as a pool zone. Multiple statistical tests conducted throughout the experiment suggest that the two stream zones differ significantly, and the diversity among a pool stream zone is relatively higher than that of a riffle zone. Important ecological factors that relate to this experiment involve the presence of important nutrients such as nitrogen and phosphorus, and the affect these nutrients have on the production of macroinvertebrates. Since macroinvertebrates are such a vital source of food for fish, effective fisheries management must account for fish-invertebrate linkages and macroinvertebrate linkages with resources and habitats (Wallace and Webster, 1996).
Literature Cited:
- Brown, A. V., Brussock, P. P. (1990, December 25). Comparisons of benthic invertebrates hhhhhhhbetween riffles and pools. Retrieved November 05, 2017.
- Hawkins, C. P., Kershner, J. L., Bisson, P. A., & Bryant, M. D. (2011, January 09). A hhhhhhhHierarchical Approach to Classifying Stream Habitat Features. Retrieved November 05, hhhhhhh2017
- Wallace, J. B., & Webster, J. R. (1996). The Role of Macroinvertebrates in Stream Ecosystem hhhhhhhFunction. Annual Review of Entomology, 41(1), 115-139. hhhhhhhdoi:10.1146/annurev.ento.41.1.115