Assessing the Health of Gull Lake Emily Grubb Trent University 2013

Transcription

1 Assessing the Health of Gull Lake Emily Grubb Trent University 2013 Prepared for: Gull Lake Cottagers Association In partnership with: U-Links Centre for Community-Based Research

2 TABLE OF CONTENTS ABSTRACT... 1 ACKNOWLEDGEMENTS...2 LIST OF FIGURES...3 LIST OF TABLES...4 GENERAL INTRODUCTION Defining Ecosystem Health Ecosystem Approach Research Focus... 7 CHAPTER 1: Gull Lake Benthic Community Report 1.0 Introduction Importance of Biomonitoring Study Subject: Benthic Macroinvertebrates METHODS Site Selection Study Design Sampling Macroinvertebrates Environmental Sampling Analysis of Invertebrate Data RESULTS Macroinvertebrate Site Composition Functional Feeding Groups Biodiversity: Abundance and Richness Hilsenhoff Biotic Index Environmental Measurement DISCUSSION Amphipod Abundance Feeding Habits Environmental Heterogeneity... 21

3 4.4 Biodiversity: Abundance and Richness CONCLUSIONS Current Inferences of Water Quality Effects of Scale and Other Factors Next Steps CHAPTER 2: 1.0 Introduction Lake Trophic Status and Eutrophication Forms of Pollution Water Quality Monitoring Measures of Ecosystem Health Importance of Lake Trout METHODS Data Collection RESULTS Total Phosphorous ph Temperature Dissolved Oxygen E. Coli Secchi Depth Turbidity Colour DISCUSSION TotalPhosphorous ph Temperature Dissolved Oxygen E. Coli... 47

4 3.6 Secchi Depth Turbidity Colour CONCLUSIONS Implications of Water Quality Effects of Water Quality on Lake Trout GENERAL CONCLUSION AND RECOMMENDATIONS...56 Water Quality and Macroinvertebrates. 56 Managing Gull Lake as a Lake Trout Lake Lakeshore Capacity Assessment Shoreline Naturalization Final remarks.61 REFERENCES 63

5 ABSTRACT Gull Lake is an inland lake located in Northern Ontario in Haliburton County. The Gull Lake Cottage Association (GLCA) is concerned with the overall water quality of the lake as there has been increased shoreline development. According to Karr and Chu (1999), biological monitoring, measuring and evaluating the condition of a living system, or biota, is the first step in protecting life in waters or anywhere else. Biological evaluations and criteria can redirect management programs towards restoring the maintaining the chemical, physical, and biological integrity of aquatic systems. Three sites were chosen along the lake from distance end to end and sampled using the kick and sweep method. Assessments of species richness, species composition, relative abundances of species, and feeding relationships among resident organisms are the most direct measures of determining biological conditions within Gull Lake. Amphipods were found to be the most dominate species at each site, representing over 50% of the benthic community. Results from functional feeding group analyses revealed that all sampling sites are collector-dominated, representing almost 80% of the benthic community, and were composed primarily of Amphipods. Site 1 was found to have the highest species richness and abundance across the three sites. Sites 2 and 3 species richness and abundance are relatively similar and not far from that of site 1. Based on the results of the Hilsenhoff Biotic Index, water quality is "fair" as determined by macroinvertebrate species assemblages. Studies have found that recolonisation of other macroinvertebrates was reduced when Amphipod numbers were high indicating predation or some form of competitive exclusion (Waters, 1964) which could potentially explain why there are such large numbers of Amphipods found across sites sampled on Gull Lake. It is important that factors (such as landscape-level factors such as land use/cover, surficial geology, and surface area or geographic factors such as latitude (Richards et al,. 1997)) are further looked into in order to develop the real reasons as to why Amphipods are in such high abundance within Gull Lake. Key Words: Biomonitoring, indicator species, benthic macroinvertebrates, water quality, ecosystem health, anthropogenic sources (human sources). 1

6 ACKNOWLEDEMENTS I would like to thank the Gull Lake Cottage Association, specifically my host Don Drouillard, for setting up this project and assisting with the macroinvertebrate study carried out in the fall as well as helping to collect data used for interoperation. I would also like to thank the U-Links programs for setting up this opportunity and Emma Horrington of U-links for all of her help in assisting with OBBN techniques as well as advice along the way. Last, I would like to thank my supervisor, Tom Whillans, for his guidance, knowledge, and support along the way. Without all of these people and organizations, this project would not have been possible. It has been a amazing experience and I have learnt so much not only out Gull Lake, but the importance of water quality monitoring as well as myself. Thank you for making this experience what is was. 2

7 LIST OF FIGURES CHAPTER 1 Figure 1 Study sites one, two, and three located along the distance from end to end of Gull Lake for sampling macroinvertebrates on October 12, Pg 5 Figure 2 Example site lay-out for sampling using the OBBN kick and sweep method... Pg 6 Figure 3 Percent composition of macroinvertebrates species found in Gull Lake October 12 th, 2012 at sites one, two, and three... Pg 10 Figure 4 Functional feeding group affiliation of macroinvertebrates collected from the study sites one, two, and three along Gull Lake on October 12, Pg 11 CHAPTER 2 Figure One Average of total phosphorous levels within Gull Lake from Figure 2 ph levels within Gull Lake from Figure 3 Average of surface temperatures within Gull Lake from Figure 4 Average of dissolved oxygen within Gull Lake from Figure 5 Average E. coli levels within Gull Lake from Figure 6 Average secchi depth within Gull Lake from Figure 7 Average turbidity levels (NTU) within Gull Lake from Figure 8 Average a apparent colour levels within Gull Lake from

8 LIST OF TABLES CHAPTER 1 Table 1 A summary of species richness and Simpson's Diversity D values calculated as a measure of site diversity at all three sampling sites on Gull Lake on October 12, Pg 12 Table 2 A summary of values calculated from the Hilsenhoff Family-level Biotic Index used to categorize data by weighing the relative abundance of taxa in terms of their pollution tolerance across sampling sites 1, 2, and 3 at Gull Lake.... Pg 13 Table 3 - Summary of results showing other significant parameters for discussion... Pg 13 CHAPTER 2 Table 1 Lake Trophic Status Table 2 Canadian Water Quality Guidelines for dissolved oxygen

9 1.0 GENERAL INTRODUCTION 1.1 Defining Ecosystem Health Emphasis in environmental protection is shifting from focus on human health to a more balanced consideration of both human and ecological health. This shift provides opportunities as well as challenges to the scientific community. Defining ecosystem health and integrity according to Costanza (1992) is a process which involves the identification of important indicators of health, endpoints of health, and identification of a healthy state which incorporates our values policy making. According to Parks Canada (2012) ecosystems exhibit integrity when their components, including plants, animals, and other organisms as well as processes such as growth and reproduction are intact. Costanza (1992) has added that a healthy ecosystem must also be stable and sustainable and maintain its organization and autonomy over time and its resilience to stress. However, Rapport et al. (1989) state that human dominated ecosystems have become highly stressed and dysfunctional and capacity of the environment to sustain economic activity and human health is being reduced. If natural fluctuations are artificially altered, ecosystems can become severely damaged. Stress on ecosystems generally weakens the resistance of local species and makes them more susceptible to disease (Karr, 1992). Ecosystem breakdown may be categorized by the following symptoms; reduced primary productivity, loss of nutrients, loss of sensitive species, increased instability of populations, increased disease prevalence, changes in the biotic size spectrum, and increased circulation of contaminants (Rapport, 1989). Even primary productivity is reduced under stress, although when the stress itself is nutrient loading, ecosystem productivity can be elevated above normal levels posing other threats to health (Rapport, 1989). Critical components of successful monitoring programs should include evaluations relative to regional expectations, 5

10 use indexes that reflect the multivariate nature of biological systems, and include index components (metrics) that evaluate conditions from individual, population, assemblage, and landscape perspectives (Karr, 1992). For purposes of health assessments, it is preferable that all symptoms of ecosystem health are analyzed rather than relying on a single indicator as a measure of health. This is because ecosystem stress may appear late in development or might in some cases fail to appear at all (Rapport, 1989). There is often a long period of time (sometimes years) between exposure to stress and subsequent development of symptoms to that stress. It is for this reason that various approaches to ecosystem health based on adverse abnormalities need to be supplemented by an analysis of the threats posed to particular environment from exposure to specific stress (Rapport, 1989). 1.2 Ecosystem Approach In the past, assessments of aquatic and terrestrial ecosystems have focused on the consumer and the economic gain in which one can accumulate through the extraction of the earth s resources. The change to the ecosystem approach represents a major paradigm shift from approaches dominated by assessments of chemical and physical monitoring to one that realizes the complexity of ecological interactions, the intrinsic importance of humans within ecosystems, and the need for a more balanced approach to resource use (Rapport 1992, Steedman 1994, and Karr 1995). Definitions of an ecosystem approach are highly variable, but according to Cash (1995), most involve one or more of the following characteristics: 1) the collection and synthesis of existing information, including a historical perspective to identify previous states or processes; 2) a holistic approach bridging different ecological, management, and political levels; and 3) a management approach that is ecologically anticipatory and ethically correct. Rapport et al. (1989) has found that linking ecosystem health to the provision of ecosystem services (those 6

11 functions that are recognized as satisfying human needs) and determining how ecosystem dysfunction relates to these services are major challenges at the interface of the health, social and natural sciences. They have also noted that ecosystems will continue to degrade under pressure of increased demands unless we apply preventative and restorative strategies to achieve the health and integrity of regional ecosystems. 1.3 Research Focus Gull Lake is an inland lake located in Northern Ontario in Haliburton County. The lake is roughly 8 km long and up to 150 ft deep and has 600 or more cottages along the shores. Gull Lake receives its water directly north from the Gull River which connects with Minden Lake. Rackety Creek also runs into Gull Lake which connects with Little Bob Lake just North-west of the lake. Gull Lake is located in the Canadian Shield where lakes are primarily rocky and have shallow soils and rapid runoff (Parks Canada, 2012). Gull Lake is a part of the Trent-Severn Waterway system and the Gull River Watershed. The Gull Lake Cottage Association (GLCA) is concerned with the overall water quality of the lake as there has been increased shoreline development. Being less than two hours away from Toronto, it is anticipated that development pressure may potentially erode the natural beauty of Gull Lake. The GCLA is concerned that this development will also negatively impact the overall health of the lake. Current lake conditions need to be determined in order to implement monitoring and management practices. This will ensure that the water quality and lake health are at level which will not cause any further environmental damage to the species of the lake as development increases. 7

12 This background document is intended to: Record the history of the lake Compile and organize past research Provide a snapshot of the lake as it exists now Identify areas where further research is required Recommend a series of actions that could help to ensure the GCLA's vision. 8

13 CHAPTER 1: 1.0 INTRODUCTION 1.1 Importance of Biomonitoring Interest in North American aquatic ecosystems has grown rapidly and this interest has intensified in the last few decades due to concerns for environmental quality (Merritt and Cummins, 1984). Retaining the biological elements of freshwater systems, as well as the processes which sustain them, is crucial to retaining the goods and services fresh water provides (Merritt and Cummins, 1984). Degradation of water resources begins in upland areas of a watershed as human activity alters plant cover. The shores of many lakes have been substantially altered by human developments such as erosion control structures or recreational beaches. Such alterations are likely to increase in the future, yet little is known about their impacts on macroinvertebrate community. These changes can modify the quality of water flowing in lake system as well as its adjacent riparian environments (Karr and Chu, 1999). According to Karr and Chu (1999), in many waters, physical habitat loss and fragmentation, invasive species, excessive water withdrawals (especially prevalent in the Trent-Sever Waterway which Gull Lake is a part of), and over harvest by sport and commercial fishers harm the system if not more than chemical contamination. According to Karr and Chu (1999), biological monitoring, measuring and evaluating the condition of a living system, or biota, is the first step in protecting life in waters or anywhere else. The goal of biological monitoring is to evaluate the effect of human activities on biological resources. Through biological monitoring we are able to track, evaluate, and communicate the condition of living systems, and the consequences of human activity on those systems 9

14 (Matthews, 1982). Because biological monitoring focuses on living organisms, whose very existence presents the integration of conditions around them, biological evaluations can diagnose chemical, physical, and biological impacts as well as their cumulative effects (Wepener et al., 2005). The concept of indicator species is of central importance in biological monitoring. Indicator species is defined as a species that has particular requirements with regard to a known set of physical or chemical variables such that changes in presence/absence, numbers, morphology, physiology, or behaviour of that species indicate that the given physical or chemical variable are outside of its preferred limits (Rosenberg and Resh, 1993). Ideally indicator organisms are those species which have narrow and specific environmental tolerances (Rosenberg and Resh, 1993). The most compelling reason for using indicator species is that they can give information on biological effects to ecosystem pollutants rather than a mere quantification of their environmental levels (Wepener et al., 2005). 1.2 Study Subject: Benthic Macroinvertebrates In order to survive, a living organism must spend its life in an environment which meets its needs: a suitable physical habitat which provides shelter and sufficient food supply, oxygen and other metabolic requirements, and is not subject to extreme conditions which are outside of the range the organism can tolerate (Abel, 1989). Different habitats have very different physical characteristics which organisms have evolved to adapt to. Benthic macroinvertebrates are well recognized as valuable indicators species and have become common in biomonitoring tools in the assessment of water quality and ecosystem health (Rosenberg and Resh, 1993). Rosenberg and Resh (1993) state that long term biomonitoring of macroinvertebrates can provide the evidence essential to the evaluation of apparent or emerging environmental problems. As the 10

15 basis of many aquatic food webs, macroinvertebrates can be considered good indicators of overall ecosystem biodiversity (Rosenberg and Resh, 1993). Macroinvertebrates are invaluable keys to the successful establishment of other freshwater biota including waterfowl and fish what rely on them for food sources (Murkin et al., 1982). Benthic macroinvertebrates are used to achieve biomonitoring objectives in a variety of ways including monitoring changes in the genetic composition, bioaccumulation of toxins, toxicological testing, and measurements of changes in population numbers, community composition, or ecosystem functioning (Rosenberg and Resh, 1993). The flowing are some of the many attributes that make macroinvertebrates good bioindicators: they are abundant and widespread; easily and inexpensively sampled; reflective of site specific conditions; they vary in their responses to pollutants; and they are fast colonizers of newly constructed aquatic habitats meaning that relevant can be obtained in short-terms (Johnson et al., 1993). 2.0 METHODS 2.1 Site Selection Macroinvertebrates will be assessed within Gull Lake as an indicator of lake health. Fall sampling of macroinvertebrates was completed on October 12 th Three sites were chosen along the lake from distance end to end order to get an understanding of the benthic community present. Site one was located in the upper part of the lake, specifically along the shore of Sandy Beach (Fig. one). Site one is not far from the Gull River mouth (lake inflow) where water flows south from Minden Lake. Site two is located in roughly the middle of the lake along the shore of Rackety Trail Road (Fig. one). This site is not far from the mouth of Rackety Creek where water comes in from the north-west from Little Bob Lake. The third site was located at the boom part of the lake in Miners Bay (Fig. one). 11

16 Figure 1 Study sites one, two, and three located along the distance from end to end of Gull Lake for sampling macroinvertebrates on October 12, These sites were chosen because they are all similar in substrate, organic matter, riparian vegetative community and abundant aquatic macrophytes. Selecting sites with these similarities ensures that factors within the lake are more likely affecting the species present rather than the geological and physical differences between sites. 2.2 Study Design The Ontario Benthos Biomonitoring Network (OBBN) Protocol Manual by Jones et al. (2004) was used in order to determine the best sampling methods for collecting an appropriate sample from the lake. Jones et al. (2004) state that the main purpose of OBBN is to enable assessment of aquatic ecosystem condition using benthos as indicators of water and habitat quality, making the use of these protocols beneficial in determining project goals. The study was designed with three sampling sites with three individual replicates taken at each site. 2.3 Sampling Macroinvertebrates Kick and Sweep Protocol Macroinvertebrates were collected using a 0.5 mm mesh D-frame dip nets in October A traveling kick and sweep method outlined in the OBBN was used along 10 m transects to 12

17 collect the samples. The substrate was kicked up as the net was moved back and forth and up and down along the transect. Sampling was done for about 3 minutes per replicate to ensure that at least 100 insects were collected. Three replicates were taken at each site in attempt to standardize sampling efforts and in order to ensure a more appropriate representation of the species present. Figure 2 Example site lay-out for sampling using the OBBN kick and sweep method Identification Species were quantified and identified to class once back in the lab using a binocular microscope. 100 individuals were counted for each site following OBBN protocol in order to develop an accurate site representation. In an attempt to minimize bias in the subsample of 100, the jars were mixed well before counting and identification took place. 2.4 Environmental Sampling All abiotic samples were taken prior to kick and sweep sampling. Temperature, dissolved oxygen (DO), conductivity (us/cm), and ph were measured using calibrated probes inserted into the water column at a standardized depth. Other parameters that were measured include dominant substrate, organic matter, and aquatic macrophytes. Qualitative measurements of 13

18 substrate, organic matter, and aquatic macrophytes were recorded to get a better understanding of the habitats in which macroinvertebrates live. 2.5 Analysis of Invertebrate Data According to Karr and Chu (1999), assessments of species richness, species composition, relative abundances of species, and feeding relationships among resident organisms are the most direct measures of determining biological conditions. These assessments are used in this study. A functional approach to studies of freshwater macroinvertebrate community structure has been increasingly emphasized, whereby taxa are assigned to a trophic or functional feeding group (FFG) based on their perceived dominant feeding mode (Merritt and Cummins, 1984). "Scrapers" graze organic biofilms covering stones and plants; "shredders" harvest detritus and coarse particulate organic matter, sediment deposit-feeding; "collectors" utilize fine and very fine particulate organic matter; "shredders" feed on living macrophytes and "predators" kill and eat members of other feeding groups (Merritt and Cummins, 1984). Macroinvertebrates collected from Gull Lake were categorized into these four functional feeding groups (scrapers, predators, shredders, and collectors) based on categorization from the following reference: Merritt and Cummins Relative percent composition of feeding groups was calculated for each sampling site within Gull Lake. Interpretation of the resulting patterns in functional feeding groups and the habitat affiliations of the most abundant taxa are reported. By comparing the functional feeding group affiliations of macroinvertebrates, associations can be drawn between the categories of nutritional resources present in the environment and the presence of invertebrate populations adapted to harvest these resources (Merritt and Cummins 1984). 14

19 Site diversity was calculated using species richness (the number of species per sample) was also calculated as a measure of biodiversity. The more species present in a sample, the 'richer' the sample. Because species richness does not take into account the abundances of the species or their relative abundance distributions, Simpson's Diversity Index is used. Simpson`s Diversity Index which, according to Magurran (2004) is appropriate for small sample sizes and relevant to aquatic ecosystems. Simpson`s Diversity Index (D): D = 1- ((Σn(n-1)/(N(N-1)) n = the total number of organisms of a particular species N = the total number of organisms of all species The use of indices summarizes information and to assess pollution effects on aquatic communities. Biotic indices are used to classify the degree of pollution in an aquatic system y determining the tolerance or sensitivity of a species to a given pollutant. Water quality specialists have developed biotic indexes sensitive to organic effluent and sedimentation (Hilsenhoff, 1982). The approach used involves ranking taxa to family on a scale from 1 (pollution tolerant) to 10 (pollution intolerant). An average pollution tolerance level (the biotic index value) is expressed as an abundance weighted mean for each site sampled to facilitate comparisons among sites. The Hilsenhoff family-level biotic index was calculated for Gull Lake to further categorize data by weighing the relative abundance of taxa in terms of their pollution tolerance and comparing these between sites. Tolerance is a listing of tolerance values for each taxon used in the calculation of numerous well tested indices foremost among which are the Hilsenhoff specieslevel Biotic Index and the Family Biotic Index. Tolerance values range from 0 for organisms very intolerant of organic wastes to 10 for organisms very tolerant of organic wastes. 15

20 Hilsenhoff Family-level Biotic Index: FBI = Σ(x i *t i )/(n) xi = number of individuals within a taxon ti = tolerance value of a taxon n = total number of organisms in the sample (100) 1.0 RESULTS 3.1 Macroinvertebrate Percent Composition Macroinvertebrate species found in Gull Lake were quantified and identified to class for each sampling site. Amphipods were found to be the most dominate species at each site, representing over 50% of the benthic community. Gastropods (snails) were found in the second largest quantity in Sites 2 and 3 and the Blood worm was found in the second largest quantity in Site 1. Gastropods, Annelida, Hempitera, and Ephemeridae were found species found across all sites in low densities. Figure 3 Percent composition of macroinvertebrates species found in Gull Lake October 12 th, 2012 at sites one, two, and three. Amph=amphipods (scuds); Anis=Anispotera; Hemi=Hempitera ; Chir=Chironomids (midges); Tric=Trichopterans (caddisflies); Ephe= Ephemeridae: Zygo=Zygoptera: Mega=Megaloptera (larvae); 16

21 Gast=Gastropods (snails); Peli=pelicypods (clams); Cole=Coleoptera: Anni=Annileda(bloodworm); Nema=Nematoda(Roundworm); Turb=Turbellaria (flatworms). 3.2 Functional Feeding Groups Results from functional feeding group analyses revealed that all sampling sites are collector-dominated, representing almost 80% of the benthic community, and were composed primarily of Amphipods (Fig. four). Scrapers represented the second high densities (between 17 and 18%) within the Lake and were primarily dominated by Gastropods. The predators were present in low densities within the lake (less than 8%) and were primarily dominated by Meglaoptera, Anisoptera, and Zygotpera. Figure 4 Functional feeding group affiliation of macroinvertebrates collected from the study sites one, two, and three along Gull Lake on October 12, Biodiversity: Abundance and Richness For macroinvertebrates collected at each site, species biodiversity was measured using the Simpson's Diversity Index and by calculating species richness. Table 1 below shows that site 1 exhibits the highest species richness indicating that there are a greater number of species present at this site. Site 3 exhibits a species richness which is very close to that of site 1 and site 17

22 2 does not show a richness significantly less to that of both sites. Overall, the three sites display relatively equal species richness. Site 1 shows highest D value from the Simpson's Diversity Index, which is consistent with measures of species richness. Sites 2 and 3 show D values that are relatively similar and not too much different from values calculated for site 1. In comparison, all three sites tend to exhibit a high D value and are not significantly different from each other. Table 1 A summary of species richness and Simpson's Diversity D values calculated as a measure of site diversity at all three sampling sites on Gull Lake. Site Density Species Richness Simpson`s Diversity Index (D) Hilsenhoff Biotic Index From the Hilsenhoff Biotic Index "tolerance values" show that majority of the species present show values over 5 (Appendix) indicating that these species exhibit a higher organic waster tolerance level. Of the 14 species present, only 4 of them are assigned values less than 5 meaning that less than 30% of the species present within the lake are very sensitive to organic waste. Amphipods, representing over 50% of the species present in the population collected, exhibit a value of 6 which would contribute significantly to the final value of the Biotic Index. Calculations of the Hilsenhoff Biotic Index indicate that all three sites exhibit a relatively similar biotic index having "fair" water quality and "fairly significant organic pollution." 18

23 Table 2 A summary of values calculated from the Hilsenhoff Family-level Biotic Index used to categorize data by weighing the relative abundance of taxa in terms of their pollution tolerance across sampling sites 1, 2, and 3 at Gull Lake on October 12, Site Biotic Index Water Quality Degree of Pollution Fair Fairly significant organic pollution Fair Fairly significant organic pollution Fair Fairly significant organic pollution 3.5 Environmental Measurements: The following table (Table 3) distils the findings of environmental factors which have significance in determining the benthic community as well as to the overall health of the lake. These abiotic parameters represent the non-living chemical and physical factors in the environment which affect ecosystem of the lake. Table 3 - Summary of results showing other significant parameters for discussion. Parameter Site 1 Site 2 Site 3 Water Temperature( C) ph DO (mg/l) Conductivity (us/cm) Dominant Substrate Slit/Sand Slit/Sand Slit/Sand Organic Matter Abundant Present Abundant Aquatic Macrophytes Submergent, rooted floating, and emergent present Submergent, rooted floating, and emergent present Submergent and emergent present 19

24 4.0 DISCUSSION 4.1 Amphipod Abundance From the data is it clear that Amphipods show the highest percent composition, representing over 60 % of the benthic macroinvertebrate population across all thee sampling sites. According to MacNeil et al. (1997), Amphipods, or Gammarus spp., are widespread throughout a diverse range of freshwater habitats and can be the dominant part of many benthic macroinvertebrate assemblages, in terms of both numbers and/or biomass. Amphipods are often found in great abundance in or under any substrate that provides both shelter from predators and a supply of organic detritus and other foodstuffs, that is, under rocks, in gravel or coarse substrates and amongst living and dead vegetation (MacNeil et al., 1997). Gull Lake has more of a sandy/silt substrate (Table 3) which initially does not seem like an ideal place for Amphipods to take shelter. However, there was an abundance of leaf litter present in the lake at the time of fall sampling (Table 3) which would have provided Amphipods with lots opportunity to seek shelter. It would be interesting to note if Amphipod populations changed seasonally based on the amount of organic matter present within the lake in order to gain a better understanding of the population. 4.2 Feeding Habits Based on the assemblages of Functional Feeding Groups, it is clear that the collectors dominate the benthic macroinvertebrate population (Figure 4). This is most likely due to the fact that the Amphipod, present in the largest density, is defined as a collector species (Merritt and Cummins, 1984). It is possible that these high densities of Amphipods are directly affecting the abundances of other macroinvertebrate species within the lake. 20

25 Although Amphipods have been traditionally been viewed as principally herbivorous shredders and detritivores (Merritt and Cummins, 1984), more recently, however, this has been found to be a myth generated by over-reliance on the rigid Functional Feeding Group classification system (MacNeil et al. 1997). Recent studies indicate that freshwater Amphipods are generalists both in habitat use and trophic ecology (MacNeil et al, 1997). They can be herbivores, detritivores, carnivores, or omnivores and according to Kelly et al. (2003) Amphipods can even become predators of other macroinvertebrates and each other. This is confirmed by Kestrup and Ricciardi (2009) whose study found that Amphipod species acted as cannibals, interspecific predators and scavengers. Because Amphipods exhibit the ability to be a generalist and can act as collectors, predators, etc rather than being a specialist, they are most likely able to find food resources at any given site allowing them to be a more resilient species within Gull Lake when compared to other less dominate and pollution tolerant species. It is important to note that as well as with amphipods, difficulties have been experienced in assigning realistic FFGs to other benthic macroinvertebrate species with considerations of changing life-history strategies, the physical mechanisms of feeding and differing proportions of resources available causing a very general and not always correct final FFG assignment (MacNeil et al, 1997). This is something to consider as data is further interpreted. 4.3 Environmental Heterogeneity It has been suggested that amphipod invasions are often associated with variation in environmental factors (Kelly et al., 2003). The study of Kelly et al. (2002) gave some indication of differential effects of two Amphipods and it was found that the invader would have a greater impact on macroinvertebrate communities because of its more aggressive attack behaviour, 21

26 greater reproductive potential, and higher densities. In addition, Waters (1964) showed that recolonisation of other macroinvertebrates was reduced when Amphipod numbers were high, indicating predation or some form of competitive exclusion. This could potentially explain why there are such large numbers of Amphipods found across sites sampled on Gull Lake (Figure 3). It has been found that the establishment success and population growth of an introduced species can be driven largely by the physiological tolerance of the invader to local conditions, which can affect the outcome of its interactions with other species in the invaded range (Kestrup and Ricciardi, 2009). Based on the high tolerance levels of the Amphipod (Appendix), it can be said the Amphipods, in general, can easily tolerate changing systems which could allow for them to be successful invaders. Experiments by Dick et al. (2002) indicates that invasive Amphipods are capable of preying effectively on many such macroinvertebrate groups and that communities may experience differential impacts on prey species. This could indicate why there other macroinvertebrate species are found in such low densities within the lake (Figure 3). Knowing that Gastropods are the species in second highest abundance (Figure 3) across all three sites and that Amphipods are not likely able to feed on Gastropods as prey because of their large size and protective shell; it could very easily be assumed that Amphipods could be acting as a predator to other macroinvertebrates found within the lake. Although most species introductions cause little detectable change in freshwater communities, some produce substantial impacts including the loss of native species through competitive exclusion (Palmer and Ricciardi, 2004) which could explain environmental heterogeneity within Gull Lake. These implications are interesting however, at this time, they are only assumptions as conditions studied could change seasonally and from year to year. This 22

27 stresses the importance of continued studies within the lake in order to get a better understanding of factors which are influencing the population. 4.4 Biodiversity: Abundance and Richness Based on calculations of species richness and the Simpson's diversity index, it is clear that all three sites experience relatively equal diversity (Table 1). In relation to the other data collected across the sites (Table 3) it is not a surprise that this is true. Had one site experienced a much greater D.O. level than another, for example, we might expect to see higher species richness and abundance when compared to other sites. Table 1 shows that site 1 has the highest species richness and abundance across the three sites. Sites 2 and 3 species richness and abundance are relatively similar and not far from that of site 1. However, it is possible that there could be potential biotic and or abiotic factors which are causing a higher species abundance at site 1 with these factors possibly having negative effects of sites 2 and 3 species abundance and richness. Although species richness and abundance are both considered here, it should be pointed out that the over abundance of Amphipods is likely to have a great effect of the macroinvertebrate community diversity. Based on the assumption of Amphipods as an invading species, Dick et al. (2002) states that invasions into native communities by exotic amphipods with exceptional predatory capabilities may have profound impacts on biodiversity. Predation by invasive Amphipods may have direct impacts on macroinvertebrate communities, reducing abundance and distributions of species, although indirect effects may include increases in populations of some species (Dick et al., 2002). It is possible that such scenarios may reflect 23

28 species extinctions, both locally and globally, of native prey exposed to invading vertebrate predators in extreme conditions (Dick et al., 2002). Therefore, it is important that we establish Amphipods as invasive or not as the lake health will likely decrease as a result of species diversity decline from invasive species. 5.0 CONCLUSIONS 5.1 Current Inferences of Water Quality Based on the results of the Hilsenhoff Biotic Index, water quality is "fair" as determined by macroinvertebrate species assemblages across all three sites sampled along Gull Lake (Table 2). Therefore, one could make the assumption that Gull Lake is not experiencing organic pollutants in higher concentrations within any of the sites sampled. More sites would have to be sampled or areas of concerned defined in order to determine where organic pollution within Gull Lake stems from. 5.2 Effects of Scale and Other Factors on Macroinvertebrate Assemblages Invasion of non-native species of Amphipods could be a result of the high densities of Amphipods found within Gull Lake. However, these are only assumptions and other factors must be considered. According to Richards et al. (1997) benthic macroinvertebrate assemblages been shown to be structured by factors such as stream hydraulics, substratum, water chemistry, and riparian vegetation. Other studies have shown landscape-level factors such as land use/cover, surficial geology, and surface area or geographic factors such as latitude and distance to water source to be as important (Richards et al., 1997). According to hierarchy theory, physical and biological variables on a small spatial scale are influenced by variables on larger spatial scales (Richards et al., 1997). Consequently, although habitat availability is considered to be the template that shapes organisms life-history 24

29 strategies, the environmental characteristics of a specific stream are not random, but are considered to be controlled by macro scale geomorphic patterns (Johnson et al., 2004). The presence of indicators species is a reflection of its environment, the presence of a species assures us that certain minimal conditions have been met, absence of a species doe not tell us that critical environmental factors are not being met (Rosenberg and Resh, 1993). The absence of a taxon might result from geographical barriers, occupation of its niche, or normal life-cycle events (Rosenberg and Resh, 1993). It is important that these factors are further looked into in order to develop the real reasons as to why Amphipods are in such high abundance within Gull Lake. Within the Gull Lake watershed, it is important to remember that the lake is apart of the Trent-Severn waterway where water levels are changed seasonally. Richards et al. (1997) points out that man-made hydromorphological impact may strongly affect river ecosystems and their biota. This is also an important factor that must be considered when assessing the health of the lake. 5.3 Next Steps Information collected from the benthic community report will be tied in with historical data that has been collected by the GCLA over the years (from 2003 to 2012) which will need to be organized and summarized. There parameters are ph, total phosphorous (TP), secchi depths, turbidity, E. coli, and dissolved oxygen (DO). The data will be used to interpret the current quality of the lake and will be analyzed in combination to the new data collected on Gull lakes benthic community. Analyzing the data in combination will allow us to make connections between the different parameters and the benthos present and tell us how different conditions in the lake might be affecting the benthic community. 25

30 CHAPTER 2: 1.0 INTRODUCTION 1.1 Lake Trophic Status and Eutrophication The trophic status, measured as phosphorus and chlorophyll a concentrations, is considered a good indicator or measure of a lake s ecosystem health and is a lake capacity factor which can limit development (Harper, 1992). Increased phosphorus inputs resulting from development is a concern on all lakes. Lakes generally progress from oligotrophic to eutrophic as a process of natural succession eutrophication. Eutrophication is defined by Abel (1989) as a natural process in which the nutrient levels of lakes increase from oligotrophic (nutrient poor) to eutrophic (nutrient rich). Eutrophication is caused by the accumulation of plant nutrients and organic matter within the lake and can be accelerated by anthropogenic influences (Abel, 1989). Since phosphorus is the nutrient in short supply in most fresh waters, even the slightest increase can, under the right conditions, set off a whole chain of undesirable events in a stream including accelerated plant growth, algae blooms, low dissolved oxygen, and the death of certain fish, macroinvertebrates, and other aquatic organisms (EPA, 2013). It is also important to understand that lakes go through seasonal and annual cycles which can change the physical and chemical characteristics. Abel (1989) points out that as time goes on, dissolved minerals including plant nutrients enter the lake from surface runoff and groundwater infiltration at a rate dependent on local climate and geology. This is why it is important to monitor local changes and to better understand the natural fluctuations and human induced changes within an ecosystem. 26

31 1.2 Forms of Pollution Point- source discharges (pollutants entering surface waters at a definable location) and non-point source discharges (pollutants entering surface waters in a dispersed manner) generated from human activities add large quantities of nutrients, pathogens, and toxins to freshwaters (Mueller et al., 1995). The resulting eutrophication and toxicity in surface waters has produced both undesirable ecological consequences and increased costs for treating the water for certain uses (Carpenter et al., 1998). These problems are often exacerbated by consumptive water uses such as irrigation and domestic water supplies, as the consumption reduces in-stream flows and thus concentrates pollutants introduced by urban, domestic, agricultural, and industrial sources (Jacoby, 1990). The discharge of excessive quantities of organic matter in undoubtly the oldest, most widespread, form of water pollution. The major sources of organic pollution are sewage and domestic wastes (Abel, 1989). Abel (1989) adds that most organic wastewaters contain a high proportion of suspended matter which effects on receiving water are similar to those of other forms of suspended solids. Understanding the forms of pollution within Gull Lake is important as it helps us to distinguish the differences between human sources of change and natural sources of change. 1.3 Water Quality Monitoring Water quality monitoring involves taking measurements that provide information on conditions and allow managers to estimate trends occurring within a given system (Chapman, 1992). Chapman (1992) describes that monitoring provides the information needed for an assessment of the conditions of the water in relation to natural variability, human effects and intended uses. Although an assessment is a cumulative evaluation of overall system conditions, it is difficult to measure all the physical, chemical and biological properties of a water body. 27

32 Instead, Karr and Chu (1999) suggest that a few variables that provide general indications of environmental conditions are selected. Many water quality variables are subject to large fluctuations in space and time. Chapman (1992) outlines that understanding these fluctuations in the physical environment and determining whether such changes are natural or a result of anthropogenic influences can be a difficult problem. Karr and Chu (1999) suggest that an ideal variable(s) provides unambiguous information about the condition of the environment in relation to reference conditions and is relatively easy and inexpensive to measure. 1.4 Measures of Ecosystem Health Biological monitoring is defined as the use of a biological entity as a detector and its response as a measure to determine environmental conditions (Karr, 1992). Baseline data can be used in order to assess ecosystem health and is a collection of background information on the conditions of the environment (water quality), tracked over time, that enables comparative assessments of potential or current impacts and ensures that appropriate information is available to guide management policies and decisions (Chapman, 1992). Measuring ecosystem health is a process that must be long term and ongoing because it is difficult, if not impossible, to draw conclusions regarding the health of the environment, or in this case the health of the lake s water, based upon a single year s observations (LPP, 2004). Unfortunately, for most lakes in Ontario, there is a lack of consistent data available to make accurate assessments of how water quality is changing over time. This report is intended to provide a comprehensive examination of the water quality and overall ecosystem health of Gull Lake. Physical parameters such as salinity, light, dissolved oxygen concentration, temperature, and ph play an important role in the biogeochemistry of water bodies (Twomey et al., 2005). Subtle changes in physical conditions can have profound effects on water quality which may in turn affect the spatial and temporal 28

33 distribution of nutrients and biological communities. Inferences of different water quality parameters for Gull Lake are defined below Phosphorous Phosphorus is often in short supply or a 'limiting nutrient' in aquatic ecosystems and limits plant and algae growth as phosphorus is an essential nutrient for all living organisms (Schindler, 1977). The primary natural sources of phosphorus to aquatic ecosystems are the slow dissolution of minerals in soil and decomposition of allocthonous organic matter, such as leaf litter (Schindler, 1977). Schindler (1977) adds that human activities have dramatically increased release of phosphorus to freshwaters. Primary anthropogenic sources of the nutrient include sewage septic tank leachate, fertilizer runoff, soil erosion, animal waste, and industrial discharges (Schindler, 1977). Increased input of nutrients in water can trigger increased plant and algae growth which can lead to changes in biological characteristics (Abel, 1989). Excessive amounts of nutrients can be very harmful to aquatic ecosystems, especially on a short-term scale (Abel, 1989). However, Abel (1989) suggests that plant growth in oligotrophic waters such as Gull Lake, where primary productivity can be limited, can be considered beneficial as moderately increased plant growth can lead to increased overall lake productivity ph ph is a term used to indicate the alkalinity or acidity of a substance as ranked on a scale from 1 to 14. Aquatic ph is affected by the production of and demand for oxygen and carbon dioxide as well as the catchment s geology (Osgood, 1957). All aquatic organisms are adapted to a certain ph range, usually between 6.5 and 8.0; a change in ph outside the normal range of a water body has the potential to cause a loss of species depending on their sensitivity (EPA, 2013). According to the LPP (2004) human caused changes in ph may result from disturbance to 29

34 acidic soils, industrial wastes, or burning of fossil fuels. The EPA (2013) states that low ph can also allow toxic elements and compounds to become mobile and available for uptake by aquatic plants and animals causing conditions that are toxic to aquatic life, particularly to sensitive species like lake trout Temperature The rates of biological and chemical processes depend on temperature. Aquatic organisms from microbes to fish are dependent on certain temperature ranges for their optimal health (EPA, 2013). The EPA (2013) states that if temperatures are outside of an organism's optimal range for a prolonged period of time, organisms are stressed and can die. According to Hauer et al. (1997) causes of temperature change include weather, removal of shading streambank vegetation, impoundments (i.e. dams), discharge of cooling water, urban storm water, and groundwater inflows to the stream. According to the EPA (2013) temperature affects the oxygen content of the water (oxygen levels lower as temperature increases), the rate of photosynthesis by aquatic plants, the metabolic rates of aquatic organisms, and the sensitivity of organisms to toxic wastes, parasites, and diseases. It is important that temperature changes within aquatic ecosystems be monitored with the foreseen impacts of climate change Dissolved Oxygen Oxygen within aquatic ecosystems is measured in its dissolved form as dissolved oxygen (DO); oxygen gas that is dissolved in the water and made available to aquatic life. Oxygen gets into the water by diffusion from the surrounding air, by aeration from moving water or as a product of photosynthesis (SITE). SITE adds that the oxygen content of natural waters varies with temperature, salinity, turbulence, photosynthetic activity of algae and plants, and 30