EEB240 Quiz 4 Notes

Lecture 9 What is Salinity and How Is It Measured? - Salinity: refers to the total concentration of dissolved inorganic ions in water or soil - Although salinity can mean any inorganic ions, in practice the most important ions are Na+, Ca2+, Mg2+, K+, Cl-, SO4(2-), CO3(2-), and HCO3- - Freshwater < 500 mg/L (1 kg of freshwater has roughly 0.5g of salt) - Brackish Water, about 500 - 30 000 mg/L - Seawater, about 35 000 mg/L (1 kg of sweater has roughly 35g of salt) ● Sodium, calcium, magnesium, potassium, chloride, sulfate, making up 99% of salts in seawater, with Cl- generally the dominant ion (55% Cl-) - Salinity is a major factor limiting the distribution of biota, aquatic biota are grouped according to their salinity preferences; i.e. freshwater fauna, brackish-water fauna and marine fauna - Conductivity is a measure of water’s capability to pass electrical flow - This ability is directly related to the concentration of ions in the water - These conductive ions come from dissolved salts, therefore, EC is routinely used to measure salinity - If salinity is affected by many different ions and if conductivity is related to salinity and not Cl- per se, then how is it possible to predict Cl- from EC, like in this figure? Where Do Salts Come From? - The process of increasing salt concentration in soil or water is called salinization - There are two main sources of increasing salinity: natural (primary) and anthropogenic (secondary) Primary Salinization 1) Weathering: the decomposition of soils and their minerals and rocks through direct contact with the Earth’s atmosphere - During the process of mineral weathering, salts (sodium, calcium, magnesium, potassium, chloride, sulphate, carbonate, bicarbonate) are gradually released and made soluble 2) Sea spray: a seawater (35 000 mg/L salts) in the form of mist and spray that makes its way into the terrestrial environment - This process is only important in coastal areas, where its influence on local salinity may be substantial 3) Evaporation of seawater: there are small amounts of salts dissolved in rainwater as a consequence of the evaporation of seawater - This third source can be a significant source of salt in terrestrial landscapes distant from the sea - Seawater can be deposited inland as a source of rain - Can introduce salinization into areas are not close to the sea Secondary Salinization 1) Irrigation, even in freshwater there is up to 500 mg/L dissolved salts - If freshwater is applied over time while irrigating crops, salt will concentrate

- This is because water is uptaken more readily than salts by plants, and water also evaporates more readily - Further, plants absorb only a fraction of the irrigation water, which may in turn cause the groundwater table to rise, bringing salty water to the surface, or brining to the surface water that is used by plants causing salinization 2) Mining activity: large quantities of potash salts (K-based salts) are extracted each year for the manufacture of agricultural fertilizers - During the manufacturing process of crude salt (containing not only potash but also NaCl and other salts) huge amounts of solid residues are stockpiled - The salts are dissolved during precipitation events and may enter the surface waters - Exposure of coal seems to weathering and percolation during coal mining provides many opportunities for the leaching of sulphate from coal wastes into surface waters - Massive amounts of salt being mined - Mining is a significant source of salinization 3) Salts as De-Icing Agents: Salts lower the freezing point of water, so since 1938 they have been used in (some) areas experience that snow and ice, as salt (NaCl) melt snow at temperatures below zero (but generally above -12 C) - Road de-icing salts have an immense benefit to human safety for those travelling during dangerous winter conditions - Road salts reduce accident rates on average 78%-87% Long-Term Trends in Salinization - “Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from371 NA lake. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest NA lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization” Roads Salts…How Much? - The US and Canada, respectively, apply roughly 24.5 and 7 million tonnes of road salt annually - 7 million tonnes is 15,432,358,000 lbs (CAD) - 24.5 million tonnes is 50,013,254,235 lbs (US) - For every person is Canada (38 000 000) we put 406 lbs of salt on the road - The primary source of secondary salinization in north-temperate regions is road salt runoff from road de-icing and anti-icing agents, whereas in other regions, it may be caused by mining, wastewater effluents, irrigation for agriculture Cl- Influences Salinity! - If primary salinization is mainly a function of parent material and geography, then it follows that there is a “base” level of salinity in the environment that is generally constant - Variation in salinity will therefore depend a lot on Cl- ions, as Cl- will enter a waterbody at a rate that depends on our behaviour and weather - Baseline of primary salinization (not very much because of weather and natural functions) - Humans come along and begin increasing salt usage

- If salt concentrations become sufficiently high, osmoregulatory mechanisms become overwhelmed, and a surplus of salt enters the cell, ad interferes with cellular process, possibly causing death - When the salinity becomes higher on the outside than on the inside → takes a lot of energy to maintain the concentration gradient - If salt concentrations become too high → impairs cellular processes (osmoregulatory machinery becomes overwhelmed and cannot handle it) - Increasing amounts of salt also impairs cellular processes and cell death can occur (too many ions) Salt Causes Stress Followed by Metabolic Collapse - Benthic invertebrates were collected and placed in a respirometer at various salt concentrations - The response was typically immediate, with increasing O2 consumption up to a critical concentration, followed by low O2 consumption - Their response to increasing salt concentrations - Authors were looking at to see what happens to organisms metabolic responses to increasing concentrations - Organisms metabolic processes in response to the high concentrations in salt and eventual metabolic collapse How Do We Assess Cl- Toxicity/Tolerance - LC50 = bioassays are used to develop dose-response curves, which are used to assess the hazard or risk posed by a given contaminant ● From these curves, we can determine the concentration that is lethal to 50% of the test population within a defined time period, or LC50 - Measured the survival = put larvae in a jar and after a specific amount of time to see the amount of tadpoles that survive in the jar - Each dot = increasing concentration of Cl- toxicity - Sees that the population is dying at a higher rate in a response to an increase in chloride concentration - Only get this data after a specific amount of time (96 hours) - Increasing duration of exposure = lower and lower LC50 = stressed out for longer and longer Lecture 10 Cl- Can Be Sublethal Effects (IC50) - IC: inhibitory concentrations or IC values, estimate the concentration at which the performance of individuals in the experimental population is inhibited in some biologically meaningful way, such as growth or reproduction, by a specified percentage relative to controls - NaCl in the environment reduced growth and size of juvenile Rainbow trout, at least at high concentrations - Here there is no outward sign of stress at low concentrations before a strong effect is observed - The experiment lasted 25 days, from 2-d post hatch to 12 days after the onset of exogenous feeding, less than 2% of the rainbow trout died (10/520)

Causes of Environmental Variability: Hard vs Soft Water - When water percolates or filters through porous material in the ground, such as deposits of limestone, chalk, or gypsum then it becomes hard - “Hard” water is water with relatively high levels of dissolved minerals, especially calcium, and magnesium carbonates ● Hard water is common in Southern Ontario - “Soft” water is water with relatively low levels of dissolved minerals, including calcium, and magnesium carbonates, bicarbonates, and sulphates ● Soft water is common on the Canadian Shield The Canadian Shield - The Canadian Shield constitutes the largest mass of exposed Precambrian rock on the face of Earth - It is composed mainly of granite, these rocks are generally quite resistant to weathering and erosion, but have been subjected to intense and repeated glaciation - During the Pleistocene Epoch (2.6 million to 11, 700 years ago), the vast continental glaciers that covered northern North America had this region as a centre - The ice, in moving to the South, scraped the land bare of its overlying mantle of weathered rock - The bulk of it was carried southward to be deposited south and southwest of the Canadian Shield - The resulting surface consists of rocky, ice-smoothed hills, together with irregular basins, which are mostly filled by lakes or swamps Hard vs Soft Water in Ontario and Canada - Hardness of drinking water can be classified in terms of its calcium carbonate (CaCO3) concentration: ● Soft: 0 to <60 mg/L ● Medium hard: 60 to <120 mg/L ● Hard: 120 to <180 mg/L ● Very hard: 180 mg/L and above Why is Cl- Toxicity Lower in Hard Water? - The short answer is that we don’t know! - One role of cell junctions is to (selectively) prevent the passage of material - A plausible hypothesis is that organisms in hard water have a lower permeability in their cellular junctions, an adaptation that helps exclude ions from intercellular spaces (where the ions might otherwise more easily enter the cell) - If this is true, then it is possible that organisms acclimated to soft vs hard water will respond differently to Cl- stress in soft water (hard-water acclimated populations will have a greater LC50) What Causes Variability Within Species? - Genetic variation - Evolution and Adaptation

- In a lake with Cl- exposure since in 1950, the Cladoceran community has changed over time Variation in Cl- Tolerance - Variation in Cl- tolerance is pervasive - As such, we expect Cl- effects on communities to be the norm rather than the exception Populations to Ecosystems - Given that salt affects different species and groups differently, what are the ecosystem-level consequences? - A trophic cascade is an ecological phenomenon that can be triggered by the addition or removal of (top) predators, and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling - Large impacts of chloride ions to lakes can interfere with normal seasonal mixing of lake waters, causing a chemical form of stratification - As chloride accumulates in the deepest part of the lake, the hypolimnion (lowest layer) becomes denser than normal - The salty hypolimnion can be resistant to mixing - A lake may become monomictic, mixing layers once instead of twice or meromictic, having no mixing - Meromictic lakes can usually be divided into three sections or layers - Monimolmnion: bottom layer - The waters in this portion of the lake circulate little, and are generally hypoxic and saltier than the rest of the lake - Mixolimnion: top layer, and essentially behaves like a holomictic lake - Chemocline: the area in between, high conductivity - Low levels of dissolved oxygen in the monoliminion can stress or kill aquatic life, giving rise to a “dead zone” within the lake Thermal Stratification - The result of the density difference between warmer and cooler water and the turnover of that stratification is an important component of the ecology and productivity of a lake - A top layer of warm water forms in many temperate lakes during summer months

- As the weather cools in the fall and winds pick up, the upper layer, the epilimnion typically gets cooler and denser then breaks up entirely as wind propels mixing of the entire lake water - This lake turnover occurs because there is less temperature difference between the upper and lower lake layers in the fall and the force of wind is sufficient for mixing during that time of year - The same turnover (complete vertical mixing), usually occurs again in the spring - Lakes that follow this pattern are termed dimictic Salt Management and Regulation by Government - Assessment of Road Salt Under the Canadian Environmental Protection Act: the Priority Substances List Assessment Report for Road Salts was published on December 1, 2001 (Environment Canada 2001) - The report concluded that road salts that contain inorganic chloride salts…have adverse impacts on the environment and are therefore toxic under subsections 64(a) and (b) of the Canadian Environmental Protection Act, 1999 - This decision has led to the publication in April 2004 of a Code of Practice for the Environmental Management of Road Salts - This Code of Practice is aimed at helping municipalities and other road authorities (>500 tonnes per year) better manage their use of road salts in a way that reduces the harm they cause to the environment while still maintaining road safety - These municipalities are legally bound to report their use to Environment Canada Canadian Council of Minsters of the Environment Guidelines - Numerical concentrations or narrative statements that are recommended as levels that should result in negligible risk of adverse effects to aquatic biota - As recommendations the Canadian Water Quality Guidelines for the Protection of Aquatic Life are not legally enforceable limits, though they may form the scientific basis for legislation, regulation, and/or management at the provincial, territorial, or municipal level - CWQGs may also be used as benchmarks or targets in the assessment and remediation of contaminated sites, as tools to evaluate the effectiveness of point-source the provincial, territorial, or municipal level - CWQGs may also be used as benchmarks or targets in the assessment and remediation of contaminated sites, as tools to evaluate the effectiveness of point-source controls, or as “alert levels” to identify potential risks Species Sensitivity Distributions - They model the variation in the sensitivity of different species to a stressor - SSDs assist in the interpretation of site data for stressor identification and risk assessment by relating them to the proportion of species expected to be affected at prescribed concentrations - SSDs are usually created using data from laboratory toxicity tests Short-term Freshwater Quality Guidelines: - Short-term exposure guidelines are derived with severe effects data (such as lethality) of defined short-term exposure periods (24 to 96-hour)

Dispersal - An ecological process that involves the movement of an individual or multiple individuals away from the population in which they were born to another location, or population, where they will settle and reproduce - One challenge with studying it is that the geographic distribution of most species is rarely very well characterized, so many dispersal events undoubtedly go unnoticed Striking Example of Dispersal - In the mid-1980s, a small mussel native to the Caspian Sea of Asia was discovered in Lake St. Claire - Biology: Each female lays up to one million eggs each breeding season, after the eggs are fertilized, larvae are free-swimming for up to a month - Result: The zebra mussel quickly became a pest, reaching densities of 750,000 per m2 - One reason that zebra mussels were transported very quickly was ballast water: ● Boat sucks up ballast water to balance the ship ● Ship travels distances and releases all the ballast water (no filtration, so all the organisms collected from one area is released into another one) Zebra Mussels - They alter food webs by removing native species’ food sources, such as plankton - They affect fish spawning areas by changing important substrates, which impacts the survival of fish eggs - They create clearer water which: ● Allows sunlight to penetrate depper ● Increases the growth of submerged aquatic vegetation ● Leads to toxic algal blooms as Zebra Mussels do not feed on toxic algae ● Increases pathogenic bacteria, avian botulism, and localized anoxia - In the Hudson River in NY, phytoplankton biomass was reduced 80-90% after zebra mussels invaded and zooplankton that feed on phytoplankton declined by more than 70% after the invasion Modes of Dispersal 1. Jump dispersal - Is the movement of individual organisms across large distances followed by the successful establishment of a population in the new area - This form of dispersal occurs in a short time during the life of an individual, and the movement usually occurs across unsuitable terrain - Island colonization is achieved by jump dispersal, and human introductions, such as the zebra mussel introduction, can often be viewed as an assisted form of jump dispersal 2. Diffusion - The gradual movement of a population across hospitable terrain for a period of several generations - This common form of dispersal is illustrated by the sea otter in California and the cane toad in Australia

- Cane Toad: introduced by jump dispersal from South America to Hawaii but sometime in the 1930, was introduced from Hawaii to Australia to predate on beetles, cane toads diffused across Australia and happened very gradually and over several years - Sea Otters: hunted near extinction in the 1900s and a population was found in the pacific ocean and began slightly diffusing across the coastline, as the years went on diffused more southernly 3. Secular dispersal - If diffusion occurs in evolutionary time, the species that is spreading undergoes extensive evolutionary change in the process - The geographic range of secularly dispersing species expands over geologic time, but at the same time natural selection is causing the migrants to diverge from the ancestral population - Secular dispersal is an important process in biogeography, but, since it occurs in evolutionary time, it is rarely of immediate interest for ecologists working in ecological time How Does Dispersal Influence Range Expansion? - Case Study: ● Reid (1899): How did the British Isles become recolonized with vegetation after the glaciation? ● Reid calculated that dispersal should have take one million years but actually took 10,000 years ● Oak trees take about 10-50 years to reach sexual maturity and even when they do, their seed droppings are only about 30 m away and it takes a long time for those seeds to mature and move - Solving Reid’s Paradox ● To repopulate Britain or northern parts of NA, trees had to migrate 100-1000 m per year. How? ● Tree seed dispersal can be mapped by putting out seed traps at different distances from the parent tree or by mapping the locations of seedlings that have been produced by isolated trees ● Mean dispersal distance of 12 species of temperate zone trees is 4-34 m ● Even though the mean dispersal distance is small, colonization rates are not driven by the mean dispersal distance but by extreme dispersal events ● A few seeds are blown by wind or moved by animals a long distance from the parent tree ● Extreme long-distance events are difficult to record and measure, since less than one seed in 10,000 might be blown a long distance by wind or moved a great distance by animals Does Dispersal Limitation Generally Limit Range Size? - Many animals also have a life stage that is highly mobile, or they are highly mobile themselves - E.g., marine pelagic fishes spawning in the water column with highly mobile larvae, many spiders are light enough to be blown on the wind, and many insects are obviously highly mobile

2. The distributions of prey and (suspected) predator are inversely correlated 3. The (suspected) predator is able to kill the prey 4. The (suspected) predator is shown to be responsible for killing the prey in transplant experiments - Mussels were transplanted around and out of the Lough, and mussels in the Lough quickly disappeared, suggesting predation - Subsequent experiments confirmed predation on mussels by crabs and starfish - Can this work the other way: Can the prey’s distribution limit the distribution of a predator? ● If the prey is to restrict the predator’s range, the predator must be very specialized and feed on only one or two species of prey ● Such a predator is called a specialist or a monophagous predator ● Many insect predators are specialists, but most vertebrate predators are not - E.g., Butterfly larvae are specializes and if the host plant that it feeds on has a range size of 10 km then the butterfly’s range limit is also 10 km and we expect a 1:1 line - But from the experiment, when looking at range size we see evidence that the range of host plants is limiting the butterfly but also some other factor is limiting it too (butterfly’s range is always smaller) Other Species: Disease and Parasitism - Like predation, disease and parasitism can restrict host distribution and abundance - Unlike predation, host distribution probably influences diseases and parasites often as diseases and parasites are often specialized on hosts - In Hawaii, >55 different species of honeycreepers evolved from a single ancestor species to exploit different niche - Hawaiin honeycreepers evolved a range of bill forms in response to available food sources on the Hawaiin archipelago - The ancestor of this radiation is likely a single species of Eurasian rosefinch that colonized the island 7 mya - Rosefinches are known for the “irruptive” behavior, irruption is typical in finches and occurs when a large mixed-sex group moves to a new wintering grounds outside their typical range - It is theoretically possible that a very small group of birds colonized Hawaii, but it is also quite possible that the original colonization consisted - Temperature and elevation affect the distribution and intensity of avian malaria in Hawaii - At low elevations, mosquitoes breed year-round and disease transmission is too intense for most native bird species to persist - At mid-elevations, up to 1500 m, disease is more seasonal and some native species persist - Only at the highest elevation forests, above 1500 m, are temperatures too cool for mosquitoes and the malaria parasite to develop, resulting in forest habitat with little to no disease transmission - However, climate change is allowing mosquito populations to invade new areas, increasing disease distribution across the Hawaiian islands

- The female releases mature glochidia (larvae) and then attach to the gills, fins, or skin of a host salamander - - Salamander mussel has evolved specialization for salamander tissue during the glochidi phase, so the range of S. ambigua aligns well with that of its only host, the mudpuppy - A cyst is quickly formed around the glochidia, and they stay on the salamander for several weeks or months, consuming nutrients from the salamander’s body, before they fall off as juvenile mussels, which they bury themselves in the sediment - The range of the salamander mussel is constrained by the host, but another factor is controlling it because the Mudpuppy’s fundamental niche is broader than the salamander mussel’s niche Other Species: Competition - Competition: a negative interaction between 2 or more organisms over resources - Interference competition: organisms seeking a resource harms one another in the process, even if the resource is not in short supply - Interspecific competition: competition between species - Intraspecific competition: competition within species Other Species: Interspecific Competition - One approach to observe the competition between species is to do a removal experiment - If competition is restricting the geographic range of a species, and we remove the dominant competitor, then the other species should expand its local geographic range ● Why? Because a fundamental niche represents the range of environmental conditions that an organism can theoretically tolerate but a realized niche is the actual niche an organism tolerates with biotic factors accounted for (food availability, competition, etc) - E.g., Tribolium confusum and Tribolium castaneum are two species that compete for food and space and egg cannibalism seems to be a major factor limiting the other species’ growth ● 2 treatments: - One with no competition: only T.castaneum present, dispersal allowed every “generation” for 24 hours by lifting flaps - Competition: T.confusm are present in patches 9-16, population for T.castaneum should be different and decrease, dispersal allowed every “generation” for 24 hours by lifting flaps ● In the no-competition treatment: found that the T. castaneum population after 7-8 generations colonized all patches and were established ● In the competition treatment: after generation 8 = no T.castaneum successful establisment because those tanks already had existing competitors, even in tanks 5,6 the population rapidly decreased because of competition Range Limits - Asymmetric competition: one species limits the realized niche of the other but not vice versa - E.g., these two species grow naturally at the edges of ponds, with T. latifolia in shallow water and T. angustifolia in deeper water