We were interested in investigating water characteristics and their effect on biodiversity and algal growth in the South Fork of Strawberry Creek (SFSC).
We were interested in investigating water characteristics and their effect on biodiversity and algal growth in the South Fork of Strawberry Creek (SFSC). We defined biodiversity as a function of species richness of macroinvertebrates living in and on top of SFSC. Based on our observations and peer-reviewed literature on urbanized landscapes and the effects of nitrate and phosphate on water systems, we hypothesized that there would be higher macroinvertebrate biodiversity and lower algal growth in areas of the South Fork located in the Berkeley Hills. We utilized the following metrics for water characteristics: dissolved oxygen, pH, water temperature, conductivity, nitrate levels, and phosphate levels. We measured water characteristics among four different sites: two on the University of California–Berkeley campus, and two in the Berkeley Hills. As a measure of algal growth we placed three tiles in each of our four sites to observe the percent cover of any algal or plant growth. At every site, we counted morphospecies as a way to test for biodiversity within a given site. We utilized ANOVA and Tukey HSD post-hoc statistical tests. We found that pH, water temperature, conductivity, nitrate and phosphate levels in on-campus sites and Berkeley Hill sites of the SFSC are significantly different. Algal growth in both on-campus sites had significant growth in comparison to Berkeley Hills sites. Our data supports our hypothesis: macroinvertebrate biodiversity in SFSC is higher in areas with little to no urban development.
From the microscopic organisms that inhabit the water, to larger Eukaryotes that depend on the water for everyday survival, water is an essential part of life. While water is a fundamental necessity for most, if not all forms of life, water is increasingly polluted due to agricultural runoff (Smith et al., 1999). According to a study on global eutrophication, human activity has profoundly affected biogeochemical cycle by nearly doubling the amount of nitrogen and substantially increasing the amount of phosphorous on the landscape (Smith et al., 1999). Another study noted that this over enrichment of phosphorus and nitrogen ultimately leads to widespread marine ecosystem eutrophication, which then impacts the water quality of the ecosystem (Carpenter et al., 1998)1. China’s Lake Taihu is an example of an excess amount eutrophication, in which widespread algal blooms disrupt food webs and leads to water quality that becomes toxic for certain organisms (Paerl et al., 2011).
According to the Center for Earth and Environmental Science at Purdue University, water quality can be affected by factors related to nitrogen and phosphorus. Other characteristics affecting water quality are dissolved oxygen, temperature, pH, and conductivity. Dissolved oxygen is the measurement of the amount of available oxygen present for chemical reactions and aquatic organisms. In relation to dissolved oxygen, the temperature of the stream can affect the amount of dissolved oxygen that is readily available. Acidity or basicity stream water can be determined through measurements of pH. According to the Center for Earth and Environmental Science, certain parameters for these measurements demonstrate optimal stream health. The ideal range for dissolved oxygen is 7-11 mg/l, pH will ideally be in the range of around of 6.5-8. Conductivity measurements of 150-400 S/cm are indicative of an excess amount of ions present in a freshwater stream, while measurements of less than 150 S/cm fall in the range of good water quality. Temperature does not have a set parameter due to multiple factors, including urban runoff, turbidity, and sunlight exposure affecting the temperature of streams in different regions. The Center for Earth and Environmental Science also informs us on the ideal ranges of nitrate and phosphate, which are between 0.9 to 3.15 mg/L for nitrate and around 0.02 mg/L for phosphate.
Due to the strong presence of urbanization, previous research leads us to believe that urban runoff, a source of nonpoint pollution, and sewage, a source of point pollution, can influence certain water characteristics of the South Fork part of the Strawberry Creek by introducing additional nitrate and phosphate to the creek (Carpenter et al., 1998). Urbanized regions of the South Fork will be more susceptible to urban runoff. According to Energy and Environmental Affairs, fertilizer usage can result in nonpoint pollution in water systems. The usage of fertilizers throughout campus is a possible source of nonpoint pollution in the South Fork region of Strawberry Creek. Point source pollution of nitrate and phosphate may be attributed to added sewage in the creek from the urbanized campus area (Brown et al., 2005). According to Charbonneau, sewage has been openly dumped into the stream in the past and may continue in lesser amounts today. Due to the increased likelihood of nonpoint and point source pollution to the lower regions of the Strawberry Creek, we expected water characteristics to differ between the sites located on the Berkeley campus in comparison to the sites of Strawberry Creek that are located in Strawberry Canyon. Measurements of conductivity may reveal if ion levels vary along the South Fork gradient of Strawberry Creek, and how this possible variance correlates to algae growth and macroinvertebrate species richness.
Based on our research, we hypothesized that there will be less species richness of macroinvertebrate occurring in the parts of Strawberry Creek that are located near campus, while the part of the stream located in the canyon will have an increased richness of macroinvertebrates.
Our field study took place in four sites along the South Fork gradient of Strawberry Creek. Site 4 was the furthest upstream near the botanical garden, and Site 1 was the furthest downstream on the UC campus. (refer to map). Site 3 was located .1 miles downstream from Site 4, right near the opening of the culvert that brings Strawberry Creek underground for a mile underneath the Berkeley stadium. The close proximity of Sites 3 and 4 is due to the inaccessibility of a site further upstream as a result of thick overgrowth. Sites 3 and 4 were chosen because they seemed to be less disturbed by urbanization or suburban developments than Sites 1 and 2. The stream in these sites generally contained a much greater amount of woody substrate from the shading tree cover and had faster water, a narrower bank, and less depth in comparison to Sites 1 and 2 located on campus. Site 2 is located 1 mile downstream of Site 4, directly after where the stream resurfaces from the culvert and after a confluence from another stream. Site one is located a total of 1.5 miles downstream of Site 4, next to the eucalyptus grove and approaching the West end of the Berkeley campus. Sites 1 and 2 were chosen because they are located in a much more heavily urbanized area than Sites 3 and 4. The stream at Site 2 is penetrated by some light, but remains mostly shaded throughout the day similarly to Sites 3 and 4. Site 4 was much more exposed to sunlight than the other sites, and also encompassed the largest pooling area of water in comparison to the other sites.
A PASCO device and Nutrafin nitrate and phosphate testing kits were used to determine if water characteristics varied across the four sites. In this field study, a PASCO equipped with a water quality multi-measure sensor was used to collect data on the conductivity, pH, dissolved oxygen, and temperature of the stream at all four locations along the South Fork gradient of Strawberry Creek. The data collected with the PASCO device was used to compare water characteristics across the gradients of our sites and to aid in understanding any correlation between species richness of macroinvertebrates and algal growth. A stainless steel probe was used to measure water temperature in degrees Celsius. The conductivity (S/cm) sensor was used to measure the electrolytic conductivity of the freshwater stream. The pH probe sensor measured voltage and computed the pH of the stream. Dissolved oxygen was measured using another probe that was immersed and gently swirled in the stream to encourage the presence of localized oxygen at the probe end. The multi-measure sensors were used to collect data once at each site per visit.
Freshwater streams located in urbanized areas are commonly exposed to excess nitrate and phosphate. While nitrate is necessary for the growth of macrophytic vegetation, an excess amount may lead to eutrophication and limited dissolved oxygen within the stream (Carpenter, 1998). With algae being a source of food for many macroinvertebrates, it is necessary to have a moderate level of nitrate to favor algal growth. A Nutrafin nitrate test kit was used to measure NO3 levels ten times in all four sites along the gradient of the stream. The sample was held up to a white background such as notebook paper with a light source to your back and have 2 or 3 observers come to a consensus on which color the sample most similarly matches in the chart provided on the testing kit box. Phosphate measurements determined the presence of possible detergents, which in sufficient quantity can be toxic to many macroinvertebrates while in moderate levels can favor algal growth (Pietilainen, 2001). Phosphate also pose the threat of freshwater algal blooms that deplete dissolved oxygen. Phosphate proves to be a key player in algal growth and the health of macroinvertebrate populations. A Nutrafin phosphate kit was used for measuring PO4 levels three times at all four sites. After allowing time to develop, the color was then compared to the chart provided on the Nutrafin box by visualizing the tube on a white background with the suns light to your back. 2-3 observers would come to a consensus of the matching color of the chart, which determined the measure of nitrate in mg/L
In order to measure algae growth, three 25 cm by 25 cm ceramic tiles were placed in the stream to provide a surface for algae to grow on at each of the four sites. The tiles were placed with the textured bottom side facing up and the smooth side facing down towards the substrate of the stream and their location was marked with a flag. Gordon et al. (1992) define riffles as shallower, higher velocity regions containing coarser bed materials, and pools as deeper, lower velocity regions containing finer bed materials. At each site one of the three tiles was placed in an area of the stream where water was pooling. The remaining two tiles were placed in riffles of the stream where water was flowing at a significantly faster rate than those tiles located in pooling areas. Riffles allow for an increase in coarse pebbly bottom materials and facilitate the growth of macrophytic vegetation (Krupek et al. 2012). Two tiles were placed in riffles of the stream, one in fast water speed and one in medium water speed. All tiles were completely immersed in the stream. In the case of a disturbed tile, flags were used to mark their original placement and where they should be repositioned to in such an event. The percent of the tile’s surface area covered by algae determined the algae growth measurement for that tile. The averaged percent cover of algae between the 2 tiles placed in the riffles of the stream determined algae growth for those tiles, while a single measurement of algal growth was obtained from the tile in the pooling areas of each site. The measurement of algal growth in the pooling areas were found to be much more significant than the little to no algae growth observed on the tiles placed in the riffles. Algal growth for the tiles in each site was much recorded on the sixth week of this research study. An additional measurement was recorded on the 11th week.
With each visit to a site, a 2m by 4m quadrat was placed in the general area of the tiles and was marked by two small flags to remain consistent between sites. Two members of the group looked for morphospecies of macroinvertebrates in the region of the stream bound by the quadrat for a period of 30 minutes. Because aquatic macroinvertebrates are highly responsive to water quality, we sought to find out if the overall species richness along the gradient of the stream was affected by different water characteristics. Morphospecies do not involve the identification of species, but rather the separation of taxa based on morphological characters that are easily observable (Derraik et al. 2002). The use of this method allowed for a species richness count at each site. If a new species was observed, its morphological characteristics were noted to prevent double counts, and it was then added to the total number of species observed for that site. Rocks and woody substrate in each quadrat were turned to allow a more thorough search in the area.
We will be analyzing our data using both ANOVA tests and post-hoc Tukey HSD tests. The reason why we want to use an ANOVA statistical test is because we want to test multiple sites on the same dependent variable and determine whether or not our data is statistically significant. By determining whether our data is significant or not will help us determine whether our results support our hypothesis or not. To determine significance, we will look for P values under .05, and we will look for high F statistics. This will ensure that the difference in data is not due to chance.
Following the use of an ANOVA test, we will use a Tukey HSD test. The Tukey HSD test is a post-hoc test, meaning that it needs to be performed after another statistical test. While ANOVA will be able to give us a P value, and an F statistic for each water characteristic, it would not allow us to see significance on a site vs. site basis. The Tukey HSD statistical test, although weak in statistical power, allows use to determine which sites are significant in respect to another, which will help us see what water characteristics may be contributing to the difference in macroinvertebrate biodiversity. We anticipate having equal sample sizes, and therefore avoid using the Scheffe statistical test, which is for uneven samples sizes and pairwise comparisons.
ANOVA was used because we have different sites because it is an analysis of variants. Dissolved oxygen was consistent throughout the stream and the F statistics measures variant to see if data is statistically significant. You want an F to be high to be significant.
|Site||Dissolved Oxygen (DO) (mg/L)||pH||Water Temp. (degrees Celsius)||Conductivity (S/cm)||Macro- invertebrate Biodiversity (# morpho- species counted/ site)||Algal Growth (% tile coverage)||Nitrate Levels (mg/L)||Phosphate Levels (mg/L)|
Table 1: The table above displays the average of all the data we collected.
|Water Characteristic:||Dissolved Oxygen (DO) (mg/L)||pH||Water Temperature (degrees Celsius)||Conductivity (mS/cm)||Nitrate||Phosphate|
Table 2: The table above displays the P-Values and F statistics of an ANOVA test run for DO, pH, water temperature, and conductivity. The asterisk (*) connotes that the value is highly significant (P<.01).
|Water Characteristic:||Dissolved Oxygen (DO) (mg/L)||pH||Water Temperature (degrees Celsius)||Conductivity ((S/cm)||Nitrate||Phosphate|
|Site 1 vs. Site 2||n/s||<.05||n/s||n/s||n/s||<.01|
|Site 1 vs. Site 3||n/s||n/s||<.01||n/s||<.01||<.01|
|Site 1 vs. Site 4||n/s||n/s||<.01||<.01||<.01||<.01|
|Site 2 vs. Site 3||n/s||<.05||<.01||<.01||<.05||<.01|
|Site 2 vs. Site 4||n/s||<.05||<.01||n/s||n/s||<.01|
|Site 3 vs. Site 4||n/s||n/s||n/s||n/s||n/s||<.01|
Table 3: The table above displays the values obtained from the Tukey HSD post-hoc statistical test. The left column shows a site being compared to another site for any significant difference. “n/s” indicates that a value is not significant; “<.01” indicates that the difference between two sites is highly significant at α=.01;” and “<.05” indicates the difference between two sites at α=.05 is significant.
Table 1 displays averaged values for the data we collected. For dissolved oxygen, Site 1 (n=5) had an average value of 9.6 mg/L, Site 2 (n=5) had an average value of 8.78 mg/L, Site 3 (n=5) had an average value of 8.26 mg/L, and Site 4 (n=5) had an average of 9.64 mg/L. While there is a decrease in dissolved oxygen as the site increases from 1-3, Figure 2 shows that there is no general trend of data. For pH, Site 1 (n=5) had an average pH of 7.92, Site 2 (n=5) had an average pH of 8.22, Site 3 had an average pH of 7.936, and Site 4 (n=5) had an average pH of 7.936. Figure 2 shows that pH was relatively stable across Sites 1,3, and 4, with an increase at Site 2, but overall has no trend. For water temperature, Site 1 (n=5) had an average water temperature of 16.426°C, Site 2 (n=5) had an average water temperature of 16.262°C, Site 3 (n=5) had an average water temperature of 13.23°C, and Site 4 (n=5) had an average water temperature 13.338°C. Figure 2 shows that there is a general trend of water temperature: average water temperature decreases when moving upstream. For conductivity, Site 1 (n=5) had an average conductivity 47.4 μs/cm, Site 2 had an average conductivity of 44.6 μs/cm, Site 3 (n=5) had an average conductivity of 32.2 μs/cm, and Site 4 (n=5) had an average conductivity of 23.6 μs/cm. Figure 2 shows a general linear trend where average conductivity decreases, when moving upstream.
When testing for nitrate, we found that the average value for Site 1 (n=10) was 7 mg/L, Site 2 (n=10) had average value of 4 mg/L, and Sites 3 and 4 (n=10) had 0.01 mg/L and 0 mg/L of nitrate present, respectively. The general trend for nitrate shows that nitrate concentrations increase as the water moves into the sites downstream (Sites 1 and 2).
When testing phosphate, we found that Site 1 (n=10) had an average value of .425 mg/L, Site 2 (n=10) had an average of .18 mg/L, Site 3 (n=10) had an average of .625 mg/L, and Site 4 (n=10) had an average of .965 mg/L. The general trend shows that nitrate increases as water moves into the downstream sites (Site 1 and Site 2) where phosphate decreases as water moves into the downstream sites. Our results indicate an inverse relationship.
Macroinvertebrate biodiversity richness was tested for at each site by searching for morphospecies for a specified amount of time at each site. We uncovered 4 morphospecies at Site 1, 5 morphospecies at Site 2 and Site 3, and 7 morphospecies at Site 4. The trend reveals that macroinvertebrate species richness decreases as water moves downstream.
ANOVA and Tukey HSD Statistical Tests
DO: The F statistic was .64, and the P Value (α=.05) was .60 (Table 2). Our low F statistic, and relatively high P value indicated that the levels of dissolved oxygen between Sites 1,2,3 and 4 were not significantly different. Further analysis through a Tukey HSD test yielded non-significant values (Table 3) between Sites 1,2,3 and 4.
Water temperature: The F statistic was 32.77 and the P Value (α=.05) was was <.0001. Our relatively high F statistic and relatively low P value indicate that differences found between sites 1,2,3 and 4 are highly statistically significant as confirmed by Tukey HSD test. The differences in water temperature between Sites 1 and 3, and Sites 1 and 4, Sites 2 and 3, and Sites 2 and 4 (α=.01) were highly statistically significant. The differences in water temperature between Sites 1 and 2, and Sites 3 and 4 (α=.05) were not significant.
Conductivity: The F statistic was 6.48 and the P Value (α=.05) was .004455 (Table 2). Our relatively high F statistic and relatively low P value indicate that differences found between sites 1,2,3 and 4 are highly significant (P<.01). Further analysis through the Tukey HSD test indicated the differences in water conductivity between Site 1 and 4, and Site 2 and 4 (α=.01) were highly significant (P<.01). However, differences in conductivity between Sites 1 and 2, Sites 1 and 3, Sites 2 and 3, and Sites 3 and 4 were not significant (Table 3).
pH: The F statistic was 6.48 and the P Value (α=.05) was .004455 (Table 2). Our relatively high F statistic and relatively low P value indicate that differences found between sites 1,2,3 and 4 are highly significant (P<.01). Further analysis through the Tukey HSD test indicated that differences in pH between Sites 1 and 2, and Sites 2 and 3, and Sites 2 and 4 (α=.05) were significant. However, pH values between Sites 1 and 3, Sites 1 and 4, and Sites 3 and 4 were not significantly different (Table 3)
Phosphate: The F statistic was 72.24 and the P Value (α=.05) was <.0001 (Table 2). Our relatively high F statistic and relatively low P value indicated that differences found between Sites 1,2,3 and 4 are highly significant (P<.01). Further analysis through the Tukey HSD test indicated that differences in phosphate levels between all sites (α=.0 1) were highly significant. t (able 3). However, pH values between Sites 1 and 3, Sites 1 and 4, and Sites 3 and 4 were not significantly different.
Nitrate: The F statistic was 12.03 and the P Value (α=.05) was <.0001 (Table 2). Our relatively high F statistic and relatively low P value indicated that differences found between Sites 1,2,3 and 4 are highly significant (P<.01). Further analysis through the Tukey HSD test indicated that differences in nitrate levels between Sites 1 and 2, and Sites 2 and 3 (α=.05) were significant.
Algal Growth and Macro-invertebrate Biodiversity
Nitrate levels positively correlated with algal growth such that water in downstream sites (Site 1 and 2) yielded a higher % tile coverage (95% and 48% respectively) than the upstream stream sites. Phosphate negatively correlate where when algal growth decreased, phosphate level increased (figure 4).
In regards to macro-invertebrate biodiversity, phosphate levels positively correlated with biodiversity such that there was higher amount of morphospecies in upstream sites (Site 3 and 4) where phosphate levels were at their highest. Nitrate negatively correlated with biodiversity where it was at its lowest when biodiversity was at its highest (figure 3).
Figure 2: Displayed above are the graphs of water temperature, dissolved oxygen, conductivity, and pH averages per site. Each water characteristic has a sample size of five (n=5).
Figure 4: The graph above shows the relationship between phosphate and nitrate levels and macroinvertebrate biodiversity. As indicated by the graph, biodiversity increases when phosphate level increases, and when nitrate levels decrease. Macroinvertebrate biodiversity also increases when moving upstream.
The main purpose of our study is to test the possible relationships between water characteristics, which are expected to include more introduced chemicals in urban areas, and biodiversity of stream life as well as average algae growth. Correlation between urban development and environmental pollutants in streams are discussed in detail in Larry Brown’s book (2005), Effects of Urbanization on Stream Ecosystems, and articles written by Shen Yu (2014) discuss the importance of runoff of pollution in urban environments. Charbonneau focus specifically on Strawberry Creek and the intense alteration it underwent as the University of California Berkeley campus urbanized and disrupted this stream, causing Strawberry Creek to act as a sewer for urban runoff. From these various sources it is expected that urban landscapes introduce pollutants to the environment and have the potential to alter natural ecosystems. Nitrates and phosphates are present in high concentrations in fertilizers and sewage (Rashid, 2013). They become prevalent chemicals in urban areas when rain causes runoff of lawns coated with organic fertilizers and waterways are used as open sewage systems (Yu, 2014). Our study sought to examine the relationships between the concentrations of these pollutants and the biodiversity of the surrounding water ecosystem, regarding richness of macroinvertebrates found in or on top of the water, and maximum amount of algae growth on tiles in each study site.
Our evaluation of water characteristics was based on readings from a PASCO probe reader, including recordings of temperature, conductivity, pH, and dissolved oxygen levels. Using these four parameters to assess water characteristics between each of our sites, it is possible to determine statistically significant differences within the stream and hypothesize pollutants likely to cause this variation.
Temperature may contribute to determining which plants and animals are most likely to survive well in stream ecosystems, as well as give an idea of the level of dissolved oxygen in the stream based on the fact that colder waters have a great capacity to hold dissolved oxygen (Center for Earth and Environmental Science). Water temperatures may vary greatly with the amount of shade and sun that each portion of the stream receives, but good water temperatures for stream animals can lie between 12 to 17 degrees Celsius (Center for Earth and Environmental Science). Sites 3 and 4, located in the Berkeley Hills and at a distance of .1 miles apart, gave average readings of 13.24 °C and 13.34 °C, respectively. Site 2, which is 1 mile away from Site 4, and Site 1, 1.5 miles away from Site 4, had average temperature readings of 16.43 °C and 16.26 °C respectively. All four sites fall within the 12-17 degrees’ Celsius range for good water temperatures for many stream animals. As indicated by our ANOVA test, this three degree difference has a very low P value and indicates that temperatures at Sites 1 and 2 are significantly different than Sites 3 and 4. This means that temperature difference in these four regions is not merely due to chance. The most likely explanation for this difference would be the high amount of tree shading in the upper Berkeley Hills area resulting in substantially cooler waters.
Conductivity of stream water relates to the amount of dissolved ions and salts present in the stream (Center for Earth and Environmental Science). Ions can include nitrate and phosphate concentrations that are introduced to the stream environment, so a statistically significant jump in conductivity may be indicative of a high presence of phosphate and nitrate ions. Levels of conductivity that fall below 150 are considered to be in good quality while streams with less than 50 μS/cm are ideal. The average findings of our sites along Strawberry Creek are relatively low with an average of 23.6 μS/cm in Site 4 and steadily increasing to 47.4 μS/cm in Site 1. These values are all within the range of very good water quality, which indicates that there is not an excessive amount of ions in Strawberry Creek. However, according to our ANOVA test, the results between Sites 1 and 4 as well as 2 and 4 have low P values and prove to be statistically significant. This indicates that ions such as nitrate and phosphate are introduced into Strawberry Creek on campus. Higher conductivity in UC campus may indicate a higher concentration of phosphate and nitrate within these areas than in the Berkeley Hills area.
An important aspect of stream health is pH and the acidity of the water. The pH scale is logarithmic, meaning that moving one number up or down the scale will lead to a tenfold increase or decrease in the acidity of the water. Invertebrates can best tolerate a range of 6.5-8.0, values above this indicate more basic waters while values below this represent acidic waters. Various types of pollution can cause both an increase and decrease in pH. The pH of Strawberry Creek lies on the high side, keeping relatively uniform at 7.93 throughout all sites with a slight increase at sight 2 and an average pH of 8.22. These results, although on the upper limits of good stream quality, still lie within the tolerable range of invertebrates. The conclusions of statistical significance shown by ANOVA and Tukey HSD tests show that there is a significant difference between Sites 2 and 4, and higher pH in Site 2 may be a result of introduced sewage coming from the confluence of another stream into the South Fork of Strawberry Creek (Rashid).
Greater amounts of dissolved oxygen provide a greater oxygen supply for invertebrates directly living in stream water. As mentioned before, dissolved oxygen levels may vary depending on the temperature of the water, with colder waters holding more oxygen. Very few invertebrates can live in water with less than 4 mg/L of dissolved oxygen. With multiple visits to each site our group recorded an average of 9.64 mg/L at Site 4, 8.26 mg/L at Site 3, 8.78 mg/L at Site 2, and 9 mg/L at Site 1. All of these readings fall within a range of 7-11 mg/L dissolved oxygen which is very high and can support most invertebrate life. According to ANOVA, there is no statistical significant for changes in dissolved oxygen level and any variances are due to chance. Overall we found that dissolved oxygen in Strawberry Creek may not play a large role in macroinvertebrate diversity and richness because these levels are high enough to support an abundance of stream life.
Nitrate and phosphate, two important ions used commonly in fertilizers and are present is sewage systems, are leading water pollutants that accumulate in runoff and result in eutrophication (Carpenter, 1998). Eutrophication is the excessive growth of algae that eventually dies and depletes oxygen from stream systems in the decomposition process, which in turn reduces the oxygen available to fish and stream invertebrates (Carpenter, 1998). According to the Aquarium Pharmaceuticals test kits we used to perform phosphate and nitrate test, levels of phosphate should ideally be at 0 mg/L but may occur at 0.05 mg/L while nitrate levels should not exceed 40 mg/L. Our data collection of nitrate indicates approximately 7 mg/L and 4 mg/L of nitrate present at Sites 1 and 2 respectively. Site 3 averaged to 0.01 mg/L of nitrate with all but one of the readings being 0, and Site 4 consistently came up as 0 mg/L of nitrate present. This concentration of nitrate is less than the maximum recommended level in streams, indicating that detrimental effects are unlikely to occur at these nitrate levels. However, the increase in nitrate from the upper regions of the Berkeley Hills to the Berkeley campus reveals that nitrate may cause an increase in algae growth in the urbanized Strawberry Creek area. Using ANOVA and Tukey Tests, it is shown that the P value is very low which indicates the nitrate tests between Sites 1 and 2 compared to 3 and 4 are significantly different from one another. This means that the increased nitrate values at Sites 1 and 2 are not due to chance but instead are impacted by some other factors, which my group hypothesizes to be sewage and fertilizer inputs by the urban campus.
Phosphate, on the other hand, decreased from concentrations of 0.965 mg/L to 0.625 mg/L at Sites 4 and 3 respectively, decreased sharply to 0.18 mg/L at Site 2, and then increased slightly to 0.425 at Site 1, the site furthest down Strawberry Creek. The P values of these results can be seen to be extremely low using ANOVA and Tukey Tests, meaning that phosphate concentrations at each site are significantly different from one another. Interestingly enough, this data shows an opposite trend compared to the nitrate data, suggesting that phosphate is higher in the less urbanized portions of the creek and lower on campus. In addition, these concentration levels are far above normal levels of .05 mg/L. According to the water quality parameters specified by the Center for Earth and Environmental Science, these high concentrations are expected to cause excess algae growth in areas in all four sites along Strawberry Creek, but this expectation was not observed. In addition, our group is curious as to why these high levels are not cumulative as water moves down to the Berkeley Campus where is predicted that additional phosphates would be added through fertilizer and sewage. Our group is uncertain why there are such high phosphate concentrations in the Berkeley hills, an exploration of this occurrence is recommended for future studies conducted in Strawberry Creek.
Determining biodiversity of animals living within and on top of the stream, as well as percent algae growth on clean tiles at each site, was crucial to our study in order to determine the effects nitrate and phosphate have on stream life. Our group based our identification of new species on morphology of a certain taxa: macro-invertebrates. After each search for species for a half hour at every site within a 4 meter by 2 meter quadrat, our group totaled the number of new morphospecies found and uncovered approximately equal numbers of morphospecies at each site. 4 morphospecies were uncovered at Site 1, 5 morphospecies were uncovered at Sites 2 and 3, and 7 morphospecies were uncovered at Site 4 mostly due to the aggregation of species on our algae tiles. Morphospecies counts reveal a slight downward trend as Strawberry Creek moved down onto Berkeley campus, which positively correlates with nitrate growth. It is possible that more nitrate concentrated in the water could have a negative effect on species richness, thereby reducing biodiversity in these areas. However, the number of species found every time we visited varied with weather and methods used, and it became difficult to determine if the maximum number of morphospecies were uncovered. More search attempts and a thorough method of searching may be necessary to determine the accuracy of our findings.
Algae generally increased in abundance in lower regions of UC Berkeley as compared to the Berkeley Hills. Sparse algae are scattered among the tiles located in the research locations above campus as well as in Site 2 located just after the culvert exit near the stadium, while a thick mat of algae grew in Site 1 on the tile in very still water. In every site, algae failed to grow in abundance in the fast and medium stream speeds our tiles were placed in but had the capability of growing well slower and deeper waters. For this reason, our calculations of algae growth depended on the slow stream tile and observations of abundant algae growth on surrounding rocks. Upon analysis of our graphs, algae growth correlates strongly with the concentration of nitrate within the stream environment. In the urban campus area, nitrate increases to 7 mg/L from 0 mg/L along the gradient between Sites 1 and 4 and algae shows a large percent increase in abundance in lower UC campus. We present our graphs with a line connected between data points because we tested algae growth and nitrate along the gradient of Strawberry Creek, and with this strong correlation we presume that intermediate sites will show intermediate results of nitrate concentration and algae growth. These results are supportive of our hypothesis that nitrate would be in greater concentration in urban areas and algae growth would increase with increased nitrate levels. Phosphate, on the other hand, shows a negative correlation with algal growth which is not is support of our hypothesis. As stated before, phosphate is far above normal levels and decreases as we move down the stream to the Berkeley campus.
After analysis of this data we find that stream characteristics in Strawberry Creek seem to fall within normal habitable ranges of a typical stream with statistically significant deviations in temperature, conductivity, and pH by site. Changes in temperature are likely associated with shade provided by trees, but higher pH levels and conductivity in areas on UC campus are indicative of introduced pollutants. Based on our knowledge of nitrate impacts on algae growth and the statistically significant results of change in conductivity and pH along the gradient of Strawberry Creek, it is likely that the correlations between pH, conductivity, and algae are related to the increase of nitrate concentrations in these areas (Center for Earth and Environmental Science). Phosphate, on the other hand seemed to follow an opposite trend while biodiversity was relatively stable and decreased slightly with higher nitrate concentrations. No definitive conclusions can be made regarding macroinvertebrate diversity due to the lack of available data and possible lack of thoroughness of our search. In our studies it was observed that algae grow the best in deep still waters. Wider stream beds in the UC campus results in more frequent pools of still, deep waters, while stream speeds tended to be faster at Sites 3 and 4 in the Berkeley Hills. Lack of appropriate algae growing conditions in the hills may, even with placing tiles in areas of slow, fast, and medium speeds, may have resulted in inaccurate measures of algae growth.
Our hypothesis that algae growth would increase in the presence of accumulated nitrate levels in Strawberry Creek was supported by our graphs of conductivity, pH, and nitrate. Levels of biodiversity decreasing as a result of the same pollution levels were slightly supported by our data, as biodiversity increased in the Berkeley Hills, yet we advise further testing to confirm our findings. Phosphate levels showed the opposite trends that we would expect as phosphate levels increased in the non-urbanized Berkeley Hills area. It is unclear why such results are observed and would suggest future experiments to explore this outcome.
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