Priority parameters for water quality and flow of energy on sustainability of an invertebrate aquatic ecosystem
Abstract
Sustainability is an essential component to consider when setting up an ecosystem for commercial or research purposes and is affected by various factors. Some of the critical factors that affect the sustainability of an ecosystem involve turbidity, conductivity, temperature and dissolved oxygen, that is, water quality parameters. Moreover, energy flow in an ecosystem is essential for ensuring that biological productivity of organisms. This paper sought to determine the various factors that relate to the sustainability of an ecosystem. In undertaking this study, an artificial ecosystem was set up in a bottle using pebbles, sand, duckweed, Vallisneria, aquatic snail and macroinvertebrates. Changes in the physicho-chemical and habitat factors were recorded weekly for a month.
The results observed indicated a continued decrease in pH, temperature, and dissolved oxygen. On the other hand, conductivity decreased with time. The rate of movement of the macroinvertebrates was seen to increase with time. There was also changes in the color of the duckweed and Vallisneria. The study observed that sustainability in an aquatic ecosystem is affected by changes in food and parameters of water quality. pH, temperature, conductivity and dissolved oxygen changes in an aquatic ecosystem with time and affect its sustainability.
Introduction
The existence of the aquatic systems is indispensable. Twomey, Piehler and Paerl (2009) explain that aquatic system have various roles. For instance, aquatic systems are responsible for drinking water, sustenance of recreational and commercial fisheries. Moreover, aquatic systems provide water used in industrial and agricultural activities. However, with the progressive pollution of the environment, the aquatic systems have been highly affected by the vice. Surface water faces a significant threat of pollution (Aazami et al., 2015). Pollution of water affects its quality.
Several factors are essential to the flourishing of an aquatic ecosystem. One such factor is the presence of substrates and food (Kotze, 2008). Water quality is a critical issue for aquatic life. However, water quality is highly jeopardized by human activities (Twomey, Piehler & Paerl, 2009). Often, human activities, both intentional and unintentional, interfere with nutrient enrichment, sedimentation, toxic contamination and alterations of the hydrologic conditions. As a result, maintenance of proper water quality has become a challenging issue in the world. The difficulty to ensure water quality is due to the vast pollution of the environment by the release of waste products and chemicals into the ecosystem, both intentionally and unintentionally.
According to Aazami et al. (2015), water quality ensures that aquatic ecosystems have functional attributes and natural biological structure. Water quality determines biogeochemistry in an aquatic ecosystem. Knowledge of the effects of water quality on aquatic ecosystems would be indispensable in ensuring maintenance of biodiversity (Abowei, 2010). Understanding of the effects of water quality on aquatic life would, hence, be an essential and prudent advancement way of creating awareness on the protection of water quality. Food availability is indispensable in an aquatic ecosystem as it determines the distribution of macroinvertebrates (Kotze, 2008).
This paper seeks to understand the energy flow in an artificial aquatic ecosystem. Moreover, it involves understanding pH, dissolved oxygen, conductivity and turbidity, essential components of water quality. It evaluates how they change as a way of informing the essence of monitoring these parameters in artificial aquatic ecosystems used in research. The paper majors on evaluating factors of quality water that should be monitored in an aquatic ecosystem. In undertaking this study, the paper uses an artificial aquatic ecosystem to determine the effect of water quality on aquatic macroinvertebrates ecosystem sustainability. The effect of water quality on the macroinvertebrates is assessed by observing their activities. According to Wright et al. (2007), macroinvertebrates are ubiquitous organisms and allow assessing of water quality. According to Twomey, Piehler and Paerl (2009), water quality can be assessed by considering factors such as dissolved oxygen, pH, conductivity, temperature, and salinity. This paper considers pH, conductivity, dissolved oxygen, and temperature. Their variation of these factors is observed, and the consequent changes of life in the ecosystem are determined.
Materials and Methods
The study involved the creation of artificial aquatic ecosystem using a bottle. The ecosystem was established in such a way that it ensured sustainability. Materials used included a bottle, pebbles, sand, duckweed, Vallisneria, mixed macroinvertebrates and an aquatic snail.
In setting up the experiment, water, pebbles and sand were put in the bottle. Vallisneria, duckweed, aquatic snail and the mixed macroinvertebrates were then added in the bottle. A net was used to cover the bottle and the physicho-chemical and habitat parameters were then monitored and recorded.
Results
The observed results were recorded weekly. Physicho-chemical factors and other relevant habitat parameters were observed and recorded. Physicho-chemical parameters that were considered involved pH, conductivity, temperature and dissolved oxygen. Habitat parameters considered involved activity and interrelation of the organisms use in the ecosystem.
Various habitat parameters were considered. In the first week, there was no significant change in the habitat parameters. However, the snail was seen to move slowly. The conductivity of the water was 133.8 ms/cm while dissolved oxygen was recorded at 9.05 mg/L. The temperature was recorded at 23 C° while the pH of the water in the ecosystem was registered at 7.5.
In the second week, the turbidity of the water was seen to have increased. Water level was also observed to have reduced further. The Vallisneria was observed to change color to yellow. The snail is observed to move around and is often attached to the duckweed, and it was seen to eat it. The macroinvertebrates were hard to see due to the high level of turbidity but with the help of a microscope, they are seen to be moving around. The duckweed is on the top of the surface of the water and has a green color. The pH of the ecosystem was recorded at 8.0. The conductivity of the water was 230ms/cm, temperature was 22.6 C° and dissolved oxygen was 8.5mg/L.
In the third week, the color of Vallisneria was seen to have changed from yellow to black. Secondly, the snail was observed on the upper side of the duckweed. Moreover, the level of the water is observed to have reduced by 0.5 cm. The rest of the macroinvertebrates are seen to move in a fast manner.The physicho-chemical parameters observed involved pH that was 7.5 and dissolved oxygen that was recorded at 9.32 mg/L. The conductivity of the water was measured to be 236 ms/cm while temperature was recorded at 23.62 C°.
In the fourth week, water level was observed to have reduced further. Three colors of the Vallisneria were observed. These colors involved black, yellow and green. The snail was found to move around but spending more time on the upper part, mostly attached to the duckweed. The color of the duckweed was light green. Other macroinvertebrates were seen to move in a fast manner. Turbidity of the water was observed to have increased. The temperature of the ecosystem was recorded at 22.8 C° while pH was 6.8. Dissolved oxygen was 8.82mg/L. The conductivity of the water was recorded at 240 ms/cm. By the end of the fourth week, pH, dissolved oxygen, temperature were seen to decrease progressively. On the other hand, conductivity is seen to increase progressively. An average decrease of water by 0.5 cm was observed every week of measurement.
Discussion
An ecosystem involves both biotic and abiotic factors. The interaction of these factors determines the sustainability of the aquatic ecosystem. Kotze (2008) states that availability and quality of water are of essence in determining water quality. Food and substrates are also another essential consideration of any ecosystem.
Food plays an essential role in shaping the distribution of organisms in an ecosystem. For the existence of any natural community, organisms must be arranged in such a way that allow the flow of energy among the various levels of primary, secondary and tertiary consumers. In the experiment, energy flow was maintained by incorporating both autotrophs and heterotrophs (Holz, Hoagland & Joern, 2000). Duckweed and Vallisneria incorporate light energy through the process of photosynthesis. The macroinvertebrates and the aquatic snail feed on duckweed and Vallisneria. Bacteria and other decomposers break down dead duckweed, Vallisneria, macroinvertebrates. Moreover, they would decompose the aquatic snail if its death occurred. The activity of the decomposers results in the release of minerals into the ecosystem. Moreover, they facilitate an exchange of gasses such as oxygen and carbon dioxide in the atmosphere.
A possible food web in the closed ecosystem of the experiment can be as illustrated below:
| Duckweed |
| Macroinvertebrates and aquatic snail |
| Mineralization |
| Sun |
| Vallisneria |
| Bacteria (Decomposers) |
Fig. 1: The food web of the bottle ecosystem
As earlier mentioned, water quality is an essential component of the aquatic ecosystem. The study above reveals that some essential parameters that determine water quality that ought to be monitored include pH and conductivity. Moreover, dissolved oxygen and temperature are critical for any aquatic ecosystem settings. These factors have been shown to interact in the ecosystem. Water level was seen to decrease in an average of 0.5 cm. The decrease in water level could be due to evaporation of water. Water from a river was used as it contained essential electrolytes required in the aquatic ecosystem.
Carr and Neary (2008) explain that conductivity in an aquatic ecosystem refers to electrical conductivity. Conductivity has a direct relationship with the amount of ions dissolved in the aquatic ecosystem. Conductivity varies depending on the changes experienced in an ecosystem. Of these changes, conductivity is affected by water level. In the experiment conducted, there was a progressive increase in conductivity. This increase of conductivity can be accounted by the changes in water level in the ecosystem. Water level progressively declined causing an effect on the concentration of ions. As water decreased, ions became more concentrated. This increase caused an increase in conductivity was observed. The graph below gives a summary of the trend of conductivity observed during the study.
Fig 2: Graph of conductivity
In the experiment, pH was observed to decrease slightly with time. pH is a factor of dissociation of water molecules in an aquatic ecosystem (Carr & Neary, 2008). The balance between the resulting hydrogen and hydroxyl ions determined the alkalinity or acidity of the water. pH is an essential component of an aquatic ecosystem as it determines its biological productivity. A pH range of 6.5-8.5 is conducive for an aquatic ecosystem. According to Bartram and Balance (1996), changes in the pH can be explained by reactions such as neutralization and redox of the dissolved water molecules. Such reactions can be due to changes in the concentration of ions as water decreased. The graph below summarizes pH trend in the ecosystem.
Fig 3: Graph showing the trend of pH
There was a progressive decrease of dissolved oxygen in the ecosystem. Dissolved oxygen is essential for metabolism reactions. The decrease of dissolved oxygen can be explained by the reduction in the water causing an increase in concentration. Concentration increase causes a decrease in the dissolved oxygen (Carr & Neary, 2008). Moreover, use of oxygen by the Vallisneria and the lack of water movement to allow for aeration of the water. Trend of dissolved oxygen form the experimental ecosystem is as illustrated in the chart below.
Fig 4: Graph indicating trend of amount of dissolved Oxygen in the ecosystem.
Temperature in an aquatic system affects biochemical reactions rate, interaction of pollutants with organisms, photosynthesis rate and vertical circulation patterns (Twomey, Piehler, Paerl, 2009). Decrease in temperature could be due to the interaction of the ecosystems with the external environment. Turbidity refers to the clarity of water. Clarity determines the amount of light scattering. An increase in turbidity in was due to increase in the concentration of ions in the water as its level reduced. The following graph gives an illustration of temperature trend for the four weeks.
Fig 5: Graph of Temperature trend
The rapidity of macroinvertebrate movement was observed to increase with time. By the end of the experiment monitoring, the macroinvertebrates were seen to move rapidly within the ecosystem. This movement could be explained by a possible increase in pollutants as waste products accumulated and possible competition due to resource depletion (West Virginia DEP, 2015). Availability of food and oxygen availability on the upper surface of the water can explain the reason the snail spent more time on the upper side of the duckweed. Change of color of the duckweed was due to loss of chlorophyll due to increasing toxicity (Khellaf & Zerdaoui, 2010). A further change of the duckweed color to black indicates the start of their death as toxicity surpasses tolerance levels. The table below gives a summary of biotic and abiotic factors that were revealed to be of essence for sustenance of an aquatic ecosystem.
| Biotic Factors | Abiotic Factors |
| Competition | Conductivity |
| Symbiosis | Temperature |
| Decomposition | Turbidity |
| Plants (For providing Oxygen and absorb Carbon Dioxide) | pH |
| Food availability | Dissolved Oxygen |
| Water Depth |
Fig 6: A table summarizing some of the essential biotic and abiotic factors of the aquatic ecosystem
Conclusion
Sustainability of an aquatic ecosystem requires maintenance of quality and diversity of a habitat (Kotze, 2008). Ensuring integrity of an aquatic ecosystem maintains a sustainable and viable aquatic community. This study reveals that sustainability of an aquatic ecosystem can be affected by both physicho-chemical and habitat parameters. Conductivity, temperature, pH and dissolved oxygen have been shown to influence the sustainability of an aquatic ecosystem. Moreover, energy flow affects the sustainability of an ecosystem by affecting the distribution of invertebrates. Artificial aquatic ecosystems, for both commercial and research purposes, should hence ensure a careful monitoring of these factors. Such maintenance of these factors at desirable levels will facilitate sustainability of the aquatic ecosystem.
References
Aazami, J., Esmaili-Sari, A., Abdoli, A., Sohrabi, H., & Van den Brink, P. J. (2015). Monitoring and assessment of water health quality in the Tajan River, Iran using physicochemical, fish and macroinvertebrates indices. Journal of Environmental Health Science and Engineering, 13(1), 29.
Abowei, J. F. N. (2010). Salinity, dissolved oxygen, pH and surface water temperature conditions in Nkoro River, Niger Delta, Nigeria. Advance journal of food science and technology, 2(1), 36-40.
Bartram, J., & Ballance, R. (Eds.). (1996). Water quality monitoring: a practical guide to the design and implementation of freshwater quality studies and monitoring programmes. CRC Press.
Carr, G. M., & Neary, J. P. (2008). Water quality for ecosystem and human health. UNEP/Earthprint.
Holz, J. C., Hoagland, K. D., & Joern, A. (2000). Aquatic Food Web Interactions: Microcosms as Lake Models.
Khellaf, N., & Zerdaoui, M. (2010). Growth response of the duckweed Lemna gibba L. to copper and nickel phytoaccumulation. Ecotoxicology, 19(8), 1363-1368.
Kotze, P. J. (2008). The ecological integrity of the Klip River and the development of a sensitivity weighted fish index of biotic integrity (SIBI)(Doctoral dissertation).
Twomey L. J., Piehler M. F., Paerl H. W. (2009). Priority parameters for monitoring of freshwater and marine systems and their measurement. In: Inyang II, Daniels JL (eds) Environmental Monitoring. EOLSS: Ontario, pp 318–338
West Virginia DEP (2015). Biological Monitoring. Department of environment protection. Retrieved from http://www.dep.wv.gov/wwe/watershed/bio_fish/pages/bio_fish.aspx
Wright, I. A., Davies, P., Wilks, D., Findlay, S., & Taylor, M. P. (2007, May). Aquatic macroinvertebrates in urban waterways: comparing ecosystem health in natural reference and urban streams. In Proceedings of the 5th Australian Stream Management Conference. Australian rivers: making a difference’.(Eds AL Wilson, RL Dehaan, RJ Watts, KJ Page, KH Bowmer and A. Curtis.) pp (pp. 467-472).
