Effects of Vegetation on Freshwater Shrimp

Effects of Vegetation on Fresh peeing ShrimpThe aim of this taste was to smash whether the front of plant life affected the abundance of the species of fresh water half-pint Gammarus pulex. To do this an experiment was carried come forth involving examples taken from a variety of vegetated and non-vegetated celestial spheres. The abundance of the species in individually surround was deliberate and compared and found to be statistically sign of the zodiacifi idlert. Freshwater fish do prefer vegetated force fields over non-vegetated areas payable to either increase availability of detritus, increased atomic issuance 8 satiate or humanitarianal protection from predators.IntroductionGammarus pulex (freshwater shrimp) are Crustaceans that are members of the Amphipoda order. Their bodies are curved into a C blueprint and they average approximately 20mm in length. As seen in figure 1, Gammarus pulex contain 7 pairs of legs, ii of which perform a grasping function quas i(prenominal) to humans hands whilst the otherwise 5 are adapted to swimming. The species gills are provided with oxygen by the vibrations of their legs and the 3 pairs of structures seen on the abdomen, the gills are setd on the in spite of appearance of the back five legs. Gammarus pulex have a high oxygen requirements and as a result are typically found in double-quick flowing, oxygen rich water. They are hatched from eggs and emerge fully developed and ready to re start. This results in a fast rate of reproduction. The offsprings sex is located by the temperature of the water. These shrimps mate whilst the male carries the female on its back, this allow for occur several times per year. Gammarus pulex Have no natural defence implement other than their disguise and as a result they are primarily active during low sunlight periods and under shelter. As a result of Gammarus pulexs leave turn up of a defence mechanism they are typically found under and at heart the aquati c fauna and rocks in spite of appearance rivers.Gammarus pulex are primary consumers that typically consume detritus, i.e. they consume dead and decaying matter in order to provide energy for themselves. Gammarus pulex main predators are fish which that rely on them as one of their primary initiations of food, fish comm whole found to consume these shrimp include Trout, Bullheads and Salmon.RationaleGammarus pulex can be utilise as an exponent species due to their affinity for highly oxygenated water. They (Gammarus Pulex) are intolerant of polluted waters or reduced dissolved oxygen concentrations, and can therefore be routined as an indicator species for water quality. A decrease in the oxygen content of an ecosystem can have serious adverse effects on the other species within the ecosystem and is one of the most common causes of Fish Kills as a result it is a variable regularly monitored by fishing agencies Due to change magnitude awareness of the impact humans are having o n their environment and the ecosystems that we interact with, biological indicator species pass on become increasingly important in the recognition of suitable habitats for species to be introduced to.In addition to Gammarus pulex playing as an indicator species, they also require highly oxygenated water to survive and reproduce. A deficiency of oxygen within the water could potentially necessitate to anaerobic conditions within the water. Due the fact that they require oxygen for respiration (Aerobic) this would reduce the universe of the shrimp within an area. This would have a knock on effect on the secary and tertiary consumers within the food chain that also rely on Gammarus pulex as their primary food source such as trout and salmon. As a result, the abundance of the species is of pick out ecological importance within these ecosystems and stairs should be taken to ensure high oxygen content of the water and adequate foliage and vegetation for the species to thrive withi n its niche. These goals can be achieved relatively easily through with(predicate) and through the planting of vegetation for cover. This would also provide raised oxygen levels due to the respiration of the plant life to produce oxygen as a by-product.In a probe by H.H Costa on investigating the affect of low concentrations of oxygen on the number of reactions per minute in Gammarus pulex, strong correlations were made between the concentration of oxygen within the water and the number of reactions taking place per minute. Low levels of oxygen would lead to decreased metabolic activity, resulting in s begin growth and reproduction. As a primary consumer this would have a detrimental effect on the rest of the ecosystem as a lower population of the species would result in food organism a limiting factor for fish that relied on the species as a source of food. This could also lead to the gradual decline of other primary and secondary consumers as they are used as a source of energ y by the tertiary consumers to fuck off themselves.AimsThe aim of the experiment was to determine whether the front man of vegetation within the water at Nettlecombe church pool would have a significant impact on the abundance of Gammarus pulex measured within an area and whether both changes in abundance could be attributed to the item-by-item variable ( front end of vegetation) by controlling or measuring rod the other abiotic factors within the ecosystem.Null hypothesisStatistically, there will be no significant correlation between the abundance of freshwater shrimp and the presence of vegetation within the stream.Alternate hypothesisStatistically, there will be significant correlation between the abundance of freshwater shrimp and the presence of vegetation within the stream.PredictionGammarus pulex will promising show a significantly higher presence in the vegetated areas of the stream due to several key biological factorsDefense Due to the lack of any inherent defense me chanisms, the species relies on its camouflage as its sole mechanism for defense. Naturally, high kernels of vegetation drive home in an area provide an aid to the protection of the freshwater shrimp from its predators and allow a greater chance of the survival of the species.Oxygen content The oxygen within water is derived primarily from underwater plants present within the water. As these plants photosynthesize, Oxygen is released as a byproduct and dissolves into the surrounding water. This increased oxygen content would attract freshwater shrimp to an area, as they are reliant on the surrounding water for the oxygen that is necessary for them to respire aerobically.Detritus Organic literal such as decaying plant material is the primary food source of Gammarus pulex as detritivores. If vegetation is present in an area an increased amount of detritus will also be present due to the death and decay of the submerged plants. This provides an ideal food source for the Gammurus pu lex and increases the chances of survival and reproduction. As a result you would expect to see an increase in the abundance of the species in areas with vegetation.Independent variableThe independent variable within the experiment was the presence of a significant (+10cm) amount of vegetation submerged within the water and the lack of +10cm of vegetation present. This was varied by turn up two areas, one with +10cm of submerged vegetation and a nonher without.Dependent variableThe dependent variable within the experiment was the relative abundance of the species within the two separate areas per sample. This was measured through obtaining a sample and counting the number of Gammarus pulex present per sample.Control variablesSeveral abiotic variables were controlled within the experiment to ensure that any changes in the abundance of the freshwater shrimps could be assigned to the changing in the independent variable. In the cases in which an impertinent variable could not be cont rolled without compromising the integrity of the experiment, the variable was measured and any anomalous readings recorded could possibly be assigned to that abiotic factor.PH The acidity (concentration of hydrogen ions) within the water was measured by obtaining a sample in the two areas and measuring the sample through the addition of universal indicator. The PH of the water was measured as Gammarus pulex have an aversion to water with more extreme Phs. In Responses of Gammarus pulex to modified environment II. Reactions to abnormal Hydrogen ion concentrations H.H Costa states that at the PH values of 9.6. These negative reactions can be explained through the inability of the shrimps enzymes to function at these extreme PHs.Temperature Temperature was measured in degrees centigrade through the use of a digital thermo fourth dimension that was placed in each sample, allowed to calm and a reading was taken. Temperature was controlled due to the reaction of Gammarus pulexs offsprin g to temperature, at lower temperatures, offspring within eggs will hatch as male, whilst above this they will hatch as female. This would lead to one sex becoming dominant at extremely hot or cold temperatures, which would result in a reduced abundance as the difficulty of locating a mate increased.Light The amount of light in each sample was recorded through the use of a lux meter as close to the water as workable. This variable was measured in lux and was measured as it is likely the shrimp will be more abundant in darker areas due to the increased effectiveness of their camouflage in these areas and increased protection this offers.Depth The skill of each location was measured through the insertion of a ruler to measure the depth of each location. The ruler was placed on the surface of the depositary to stop it macrocosm pushed too far into the soft depository and producing an inaccurate reading. Areas were chosen as close to 10cm profound as possible to rule out the depth of the water having any significant impact on the results produced.Pilot analyzeIntroductionBefore carrying out the main study, a pilot burner study was used to determine the utmost procedure and mode of the study. This pilot study was used to identify the best try technique to use to collect a sufficient number of shrimps per sample. This technique had to be efficient enough to collect enough info for a statistical significance to be shown and collect the maximal number of shrimp within an area to ensure that the true abundance of the species was actually being measured. In addition, the method used to collect the shrimp had to be standardized, so that the identical technique could be carried out in different areas to ensure the reliability of the technique. This meant the same technique could be carried out again to produce as same results as possible.In addition, the best local spot to produce enough shrimp to state a significant difference had to be located. This pilot study was used to locate the areas that would be sampled in the main experiment by locating the areas with enough vegetation to have an impact on the dependent variable. This meant looking for areas with high levels of submerged vegetation within several different rivers until enough within as Single River was found. This was to make the control of extraneous variables easier as the variation in the variables would be far larger in separate bodies of water. in spite of appearance the pilot study, I also had to assess the extraneous variables that would have to be measured in my final study to prevent them interfering with the data produced. During the pilot study, I identified that the amount of light in an area seemed to be having an effect on the abundance of the species within that area. This was potentially reducing the validity of the experiment. This was because any results produced were no longer necessarily down to just the independent (presence of vegetation) variable. As a result, I included the use of a light meter in the final experiment to control and limit the impact on the data produced. Along with deciding the variables to be measured, I also had to finalize the equipment used to measure the variable in a standardized manner.The pilot study was also used to identify any potential risks or destinys within the area. Once these were identified, appropriate controls could be taken to reduce or nullify the risks from these sources.Equipment hearA 15cmx10cm Scoop netA 1 meter long rulerA digital thermometerA square 1025 cm tray that was not make full with pond waterA digital stopwatchFreshwater identification planing machinePipetteMethodWhilst 3 rivers were found in close proximity, only one, the church stream, contained an appropriate number of vegetated areas to non-vegetated areas close enough to carry out the experiment expediently. In addition the proximity of the locations reduced any extraneous variables that were acting on the study. Thus the church stream was used for the final experiment.2 methods of sampling with the net were carried out, the figure of eight sample (A)and the Kick sample(B)A) This involved locating an area to sample and standing still whilst paltry the net in a figure of eight through the water. This was measure for 10 seconds and 20 seconds .This method did not disturb the sediment of the area.B) The blossom sample involved placing the net downstream of the area to be sampled and kicking up the sediment into the net without moving the net. This was timed for both 10 seconds and 20 seconds using the stopwatch.After collecting each sample the contents of the net was upturned and placed into the empty tray. The tray was past filled with water from the stream.Using the identification sheet, I timed for 1 minute on the stopwatch and counted all of the Gammarus pulex present in the tray within the time. Using a pipette to move them to a separate set once countedA variety of sampling technique s for the control variables were then carried out in the area.The ruler was used to measure depth at a variety of locations. This provided practice at accurately measuring the depth of the water without disturbing the sediment on the rump of the stream.The digital thermometer was then placed in the water, however not placed at the bed of the stream. peril assessmentBefore carrying out the pilot and main study, a risk assessment of the risks that could pose a threat to me or those in the surrounding areas was carried out. Through this I identified the hazard (negative effect 1-10) and the risk factor (chance of the hazard actually occurring 1-10) to control this I also decided on sensible controls to minimize the chance of the hazard occurring or minimize the severity of the hazard. The risk rating was calculated by multiplying the chance of the hazard occurring with the severity of the hazard (1-100).Hazard Severity of the Hazard Chance of occurring Risk rating ControlSlipping and falling. 2 6 12 Ensure the muddy parts of the bank are noted and avoided. Wear appropriate footwear to avoid tripping/slipping.Drowning in unexpected deep water. 10 1 10 Ensure all personal can swim. Identify any deep areas in front beginning.Contamination from any water/aquatic life. 8 3 24 Wash hands before and after touching the water. Do not handle the aquatic life, use a pipette insteadTripping with net/ruler. 4 4 16 Wear appropriate footwear, I.e. hiking bootsDiscussion of resultsThe number of shrimp produced by using method B for 20 seconds produced the largest get along number of shrimp in both vegetated areas and non-vegetated areas. In comparison, method A produced the few number of shrimp in both vegetated areas and non-vegetated areas. The temperatures produced seemed to be pretty constant throughout the pilot study however the two 9.8 readings were likely caused by the thermometer not being pressed to the sediment properly, reducing the reliability of those readings . The preliminary findings reflected that more shrimp were indeed found in the vegetated areas in comparison to the non-vegetated.Evaluation of pilot studyThrough the use of the pilot study I was able to identify the main difficultys with the study and remedy them for the final studyThe measuring of the temperature using the thermometer was standardized by pressing the thermometer to the bed of the stream on each measurement.The sample I chose to use was the 20 seconds kick sample This method of sampling was far superior to the figure of eight sample. This was likely to the freshwater shrimp knowing the upper layer of the sediment the kick sample dislodged them into the net whereas the figure of eight did not disrupt the sediment at all resulting in only the swimming shrimp being picked up. As a result, only the number of shrimp swimming in a sampled area was being measured not the total number of shrimp in the area. I chose to use the 20 second sample as, although it was less exp edient than the 10 second sample, it did provide more species and reduced the chance of anomalies cropping up through not all of the shrimp being collected.Whilst measuring the depth in step 8, I noticed that the vegetated areas where normally darker than the non- vegetated areas. To counteract this variable, I decided to control it in the main experiment by measuring the light using a lux meter. This was to ensure that the results were down to the vegetation present.During step 1 and the selection of the location of the samples, I realized that I hadnt set any specification on what classed as enough vegetation to qualify as a vegetated area. After discussing this with my tutor I decided to use 10cm measurements of submerged vegetation qualify an area as vegetated. In addition, I used areas without any vegetation for the final experiment.Whilst collecting the samples in step 4 I realized that I was disturbing the ecology further downstream on further kick samples. This was an unfort unate side effect of using the kick sample from the top of the stream down. As a result, I decided to reverse the direction for the final experiment and take the values from downstream before taking those upstream. This stopped earlier experiments influencing later ones.Main ExperimentMy final experiment took into billhook the findings from the pilot study and used these to modify the final experiment to produce the best results I could. The changes listed above were introduced to tailor the results of the experiment into a form I could use to compare the effect of the independent variable.IntroMy final experiment consisted of 10 samples of each vegetated and non-vegetated areas being taken, with the variables light, depth, temperature, PH and number of shrimp present being measured. The revised aim of the final experiment was to measure whether the presence of vegetation affected the abundance of Gammarus pulex present and whether this difference was statistically significant. To do this I carried out a stratified sampling technique to locate areas to work in, I,e areas with +10 cm of submerged vegetation. I then used a systematic sampling technique to collect the data as I timed how many of the species I could count from a sample in 1 minute.Equipment listA 15cmx10cm Scoop netA 1 meter long rulerA digital thermometerA square 1025 cm tray that was pre-filled with pond waterA digital stopwatchFreshwater identification sheetPipette1 Lux meter1 bottle of universal indicator, with a beaker to collect a sample of waterA small bucket to place counted shrimp inWriting equipment and paper to record resultsPipette to collect the shrimp withMethod10 vegetated areas were first located. This involved measuring the total submerged vegetation present and ensuring it was over 10cm long.The non-vegetated areas were then located, these were areas within as close proximity to the vegetated areas as possible but without any vegetation present. starting from downstream and movi ng upstream, the kick sample was performed in the first vegetated area. This involved placing the net downstream from the sampling area and kicking the sediment for 20 seconds into the net. This was timed with the stopwatch.The sample in the net was upturned into the tray.The Gammarus pulex were identified using the species identification sheet and removed from the tray and placed in the bucket using a pipette. The total number of shrimp counted in 1 minute was recorded.The contents of the tray and bucket were emptied back into the water.The depth of the sampling area was then measured using the ruler and placing it on the stream bed. The lowest value of the water rising up the ruler was measured as the depth.The thermometer was then placed lightly on the stream bed, this was left to stabilize for 10 seconds and the value was recordedThe lux meter was then placed as close to the water as possible and held still. After 10 seconds the value was taken.This method was repeated for the n on-vegetated areas.This procedure was carried out at all of the 10 areas.Table of results for main experimentCalculations of the means for Vegetated dataMean PH (7.5 x 10)/10 = 7.5Mean temperature C (9.8 x 2 + 9.9 x 8)/10 = 9.88Mean Lux reading (Lux) (240+234+194+30+13+109+603+719+560+335)/10 = 303.7Average depth (cm) (10.0+9.5+5.0+4.0+4.0+5.0+5.2+8.2+12.8+13.2) /10 = 7.69Mean Shrimp (Arbitary units) 341/10 = 34.1Calculations of the means for Non-Vegetated data Mean PH (7.5 x 10)/10 = 7.5Mean temperature C (9.8 x 1 + 9.9 x 9)/10 = 9.89Mean Lux reading (Lux) (846+645+300+71+24+123+441+739+506+389)/10 = 408.4Average depth (cm) (12+11.5+10.5+12+8+10.5+12.4+14.5+12.4+13.3) /10 = 11.71Mean Shrimp (Arbitary units) 56/10 = 5.6AnomaliesBoth of the values highlighted in red, are examples of possible anomalous data that could have been caused by adjectival errors. 6 is far below the average shrimp reading of 34.1, this could have been caused by the high light reading on this particul ar reading, reducing the shrimps camouflage and therefore their safety in this area. The value of 17 was far ahead of the mean value of 5.6 and could have been caused through the procedural error of the pipette not sucking the shrimp up and them being counted twice. These samples also could have had the random error of large amounts of sediment resulting in some shrimps not being counted or others being counted twice.The clear variation in the number of Gammarus pulex sampled in the two areas would indicate that the vegetation did have an effect on the abundance of the population. presumable due to the increased defense offered by these areas and also how much easier it would be to obtain decomposing plant matter (Detritus) as a food source. The largest value for a vegetated shrimp was 79, with the lowest being 6. This is in comparison to the highest value for non-vegetated areas being 17, with the lowest being 2. The similarities between the abiotic factors, primarily temperature and P.H also increase the validity of the results produced. We can be sure that the results are actually as a result of the presence of the vegetation. It should be noted that none of the samples contained no freshwater shrimp, leading to the premise that the water likely has a high oxygen content and has few pollutants. This is backed up by the location of Nettlecombe, a relatively rural area with few large roads running nearby.StatisticsWithin this study I decided to use the Mann Whitney U test to ascertain whether the difference between the two values was enough to reject the null hypothesis and convey a significant difference between the two sets of data.Null Hypothesis There will be no significant statistical difference between the data drawn from vegetated samples and non-vegetated samples in the Nettlecombe church stream on the 14/10/12The lowest U value calculated was 6, The critical value at 0.1 is 16 meaning that the Null Hypothesis can be rejected at the 0.1 significance level This allows us to accept the alternate hypothesis, and although there were small overlaps in the data, the difference between the two sets of data values is significant.Evaluation passim the experiment, every effort was made to control or measure extraneous variables that could have an effect on the results of the experiment. As a result, the validity of the experiment is preferably high the values for all the abiotic variables were measured and have similar values for both the Vegetated areas and the non-vegetated areas. As a result we can make the assumption that any changes in the dependent variable, were in fact down to the independent variable.The pilot study was carried out to aid in the identification of any confounding variables, risks or extraneous variables that could potentially impact on the validity of the results produced and as a result of the pilot study, controls were put in place to counteract these variables.In addition, due to the standardized methodology carried out within both the pilot experiment and the final experiment, the method could be repeated under similar conditions to produce similar results. Resulting in a high reliability of the data.As the Mann Whitney U test allowed us to reject the null hypothesis at the 0.01% significance level, we must deliver that the results produced show a significant change between the two environments.Although the results proved to be statistically significant, several procedural errors should be considered. Even with a 20 second kick sample, not all of the shrimp in a certain area could be collected as the shrimp likely inhabit different layers of the sediment. The speed at which the shrimp were counted at could also vary considerably based on the amount of sediment present in a sample, in a sample with high amounts of sediment, it would take longer to count and remove all of the shrimp within a minute than it would be in a clear sample. To counteract this, a stratified sample could be put in place all of the shrimp from a sample could be counted rather than just counting for one minute.Systematic errors within parts of the equipment could result in repeatedly wrong measurements, e.g the Lux meter may not be calibrated properly and give readings that are continually 50 higher than they should be.Percentage error can also become a problem and whilst small, can be noticeable when accounted for in multiple datasets e.g. 0.01/500 x100 = 0.002 % percentage errorThere are also several ethical considerations to take into account when using live organisms within experiments. For instance the ecosystem is being massively disrupted through the use of a kick sample. All of the layers of sediment are being removed and many organisms are being collected in a sample that didnt have to be. A more specific and less environmentally invasive procedure could instead be carried out using the figure of eight sampling method so as not to disturb the stream bed ecosystem as much.Conclusio nFrom the data and evidence provided above, a original argument can be put forward that the species Gammarus pulex does favor vegetated conditions over non-vegetated conditions. This could be down to a variety of reasonsGammarus pulex is an aerobic organism and thus favors oxygenated conditions. During photosynthesis in submerged plants, oxygen is produced as a byproduct which diffuses into the surrounding environment (the water) this results in increased oxygen content. The oxygen content at this point is not acting as a limiting factor in the population of Gammarus pulux and thus an increase in the activity within the reproductive cycle of the species. This is demonstrated in the image to the right.Gammarus pulex favors the vegetated environment due to the increased source of detritus present through the decomposition of the plants present in the environment. This increased source of food and energy means the species expends more energy within its reproductive cycle and fewer of the species die due to starvation. Thus the population of the species in these conditions increases.Gammarus pulex could also potentially favor the vegetated environment due to the increased camouflage and protection it provides it. This could be part of a behavioral adaptation the organism has developed to protect itself from the fish that hunt it. This would result in large amount gathering in the areas that they were safe and fewer of them being consumed by secondary and tertiary consumers resulting in larger numbers of them in the vegetated areas.Source evaluationWithin my experiment, I extensively referenced and used H.H Costas work into the differing effects of modified environments on Gammarus pulex. This work was published in the scientific, peer reviewed journal Crustaceana. This journal is is a leading journal in the world on crustacean research. As a result I feel the peer reviewed work is both reliable and accurate and although published in 1967, the more recent resear ch (Field guide to the water life of Britain 1984) also agrees with the core principles described in H.H Costas work. In addition to several peer reviewed journals, one of my sources was an Information pack produced by the University of Florida, a well respected academic institute unlikely to publish inaccurate or unreliable information. As well as the paper sources listed, I used a variety of websites to gather data on various aquatic processes and mechanisms. Whilst I trust the majority of the websites, certain websites such as source 2, dont back up many of the claims with any real evidence which could be a sign of unreliable or inaccurate information.Further researchFurther research could be carried out into the preferences of Gammarus pulex through an experiment designed to ascertain the theatrical role of vegetation that they prefer and also the nutritional value of the varying types of detritus to the organism. In addition, research could be done into pinpointing the exact r eason that the species prefers to reside within vegetative conditions rather than non-vegetative.