APES Unit 8-

how do people affect aquatic ecosystems?

divert rivers, dam rivers, & introduce substances & diseases → accumulation in oceans & pollution in groundwater

nonpoint source

pollutants enter the environment from many places at once spread out over a large geographic region → difficult to point to one individual source

point source

pollutants that enter environments from an easily identified & confined place → can “point” to it

effects of nutrient pollution

nitrogen & phosphorus increases → eutrophication of surface waters → increased Biological Oxygen Demand (BOD) → dissolved oxygen (DO) levels decrease

causes of nutrient pollution

• runoff of fertilizers (not pesticides) from farms, golf courses, & residential lawns

• sewage lakes/discharge into surface waters

• flooded to leaking CAFO manure lakes

oligotrophic lakes

lakes & ponds with low nutrient (N/P) levels, stable algae populations, & high dissolved oxygen due to lack of nutrient pollution or age of body of water

eutrophic lakes

sediment builds up on the benthic zone (bottom) due to continuous erosion in watershed & deposition into lakes/ponds → shallower benthic environments → increased sunlight reaching these environments → increased growth of rooted aquatic vegetation → more trapped sediment & dissolved nutrients

sediment

eroded material that is carried into rivers & deposited into depositional basins (lakes, bays, river deltas, oceans)— increase turbidity of aquatic ecosystems

common causes of sediment

logging, mining, construction, farming

turbidity

measures depth that light can penetrate from the surface of the water

**increased turbidity reduces NPP of ecosystems & alters entire food webs/chains b.c it affects visual predators’ visibility

thermal pollution

results from any process that changes the ambient water temperature → heat increases respiration rate of aquatic organisms (thermal shock)

dissolved O2 levels based on temperature

hot water has less dissolved O2 since gases diffuse out of solutions more rapidly at higher temperatures → solubility of gases decrease as temperature increases

impact of resevoirs

• can change seasonal temperatures of water downstream

• impact the timing of migration, spawning, & egg hatching

causes of thermal pollution

• nuclear power plants: power plants use cool water from surface/ground water to cool steam produced for turning a turbine back into water (cool) to reuse

• cooling towers & holding ponds: require large amounts of cool water to cool stream back to water & discharge it back to the environment

• steel mills, paper mills, other manufacturing plants: use cool down machinery → return warm water

• urban stormwater drain runoff: causes thermal pollution due to heat from blacktop/asphalt

how does plastic trash get into the ocean?

1. litter reaches aquatic ecosystems

2. plastic debris is durable & breaks into microplastics

3. washes out of watersheds into oceans

4. areas where circulating currents converge (gyres) bring & trap plastic trash

effects of litter to aquatic ecosystems

• marine plastics mistaken as food (plankton or fish eggs)→ ingestion, choking hazard, intestinal blockages → deaths of marine mammals & seabirds

• plastics contain harmful substances (Bisphenol A & phthalates) → leech into digestive tracks of organisms + POPs adhere to plastics & increase toxicity

• risk of entanglement in plastic → suffocation & exhaustion

impacts of oil spills

• organisms may be killed by smothering, injstion, inhaling, or absorbing oil

• fish kills become coated → reduces gas exchange

• birds loose buoyancy → process to hypothermia

• decreased light penetration → reduced photosynthesis & base of marine food chains

chemical dispersants

break down oils into smaller droplets, diluting the concentration & reducing toxicity

others ways to clean up oil spills

• microbes that degrade oil

• burning oil off the surface of the water

• use of skimmers to collect oil on the surface + floating booms to keep it contained

• using absorbent material to soak up the oil as it washes ashore

• physically cleaning rocks & organisms along short-line

wetlands

area with soil submerged/saturated in water for at least part of the year but shallow enough for emergent plants (adapted to living with roots submerged in standing water—cattails, lilpads, reeds)

ecosystem services of wetlands

• supporting: H20 filtration, biodiversity, nutrient cycling

• regulating: groundwater recharge, absorb of floodwater, CO2 sequestration

• provisioning: habitat for animal & plant foods

• cultural: tourism, revenue, fishing licence, camping fees, ed/med research

threats to wetlands

• pollutants (nutrients N/P)

• sediment

• motor soil

• pesticides

• sea-level rise

• development (can be filled in or drained)

• water diversion for flood control, agriculture, or drinking water → reduces water flow & dries them up

• dam construction

• overfishing

mangroves

small trees with unique roots that grow in saline or brackish water throughout the tropics

mangrove ecosystem services

• supporting: biodiversity (habitat nursery), H2) filtration, nutrient cycling

• regulating: coastal protection, storm buffering, erosion control

• provisioning: habitat for juvenile commercial fish species, timber, fuelwood

• cultural: tourism, recreation, aesthetics

threats to coasts

• same threats as wetlands

• sea-level rise

• development

• pollution

• over harvesting aquaculture

mercury

considered most toxic heavy metal in the environment & main contributor is coal combustion, trash incineration, burning medical wastes, & heating limestone for cement production

inorganic mercury (Hg 2+)

has low toxicity, attaches to PM released by combustion → deposited wherever PM settles

methylmercury (CH3Hg+ or MeHg)

Hg2+ depositioned in aquatic ecosystems that converts to a more organic toxic form by phytoplankton & bacteria → is incorporated into lipids found in neurons → inhibits nervous systems function (neurotoxins) as result + lead to miscarriages + birth defects (teratogen) or bioaccumulates in organisms & biomagnifies in ecosystem

arsenic (AS)

naturally occurring element in rocks underground that can dissolve into drinking water & is naturally releases worsens with mining into ground water → coal ash & particulate matter can spread arsenic over large areas

**formally used in pesticides & wood treatments

toxicity of arsenic

• carcinogenic (lungs, bladder, kidney)

• endocrine disrupting (blocks receptor proteins on cell surfaces from receiving steroidal signal)

lead (Pb)

most abundant heavy metal pollutant (ex. old paint, old water pipes, car batteries, used as glaze in some pottery, PM from vehicle exhaust)

toxicity of lead

• neurotoxicant (damages central nervous system)

• endocrine disruptor

pathway inhibitors

toxicants that block steps in a biochemical pathway → may inhibit key enzymes (ex. Atrazine inhibits enzymes in Calvin Cycle of photosynthesis, cyanide inhibits electron carrier proteins in ETC of mitochondria, blocking cellular respiration)

endocrine disruptors

pathway inhibitors that interfere with the endocrine (hormonal) systems of animals

• hormones stimulate growth, development, sexual maturity, work w/ extremely small concentration

• endocrine disrupting chemicals interfere with normal signals → block hormones, preventing signals from working → mimics hormones (sometimes estrogen )

atrazine

endocrine disrupting chemical that binds to receptors, converting estrogen to testosterone in male frogs → higher estrogen/lower testosterene levels → lowers sperm count & causes gender reversal & development of eggs in test or ovary formation

human medications

pass through urine & into sewage or flushed down toilet → common source of endocrine disrupting chemicals

heavy metals

endocrine disruptors such as mercury, lead, arsenic

phthalates

endocrine disrupting compound used to make plastic more flexible & in cosmetic manufacturing (plastic, fragrances)

bisphenol A (BPA)

used to make hard plastics & epoxy → common in food-storage containers

polyfluoroalkyl substances (PFAs)

non-stick coating of cookware → enter surface & groundwater through improper disposal of chemical water & landfill leaching

persistent organic pollutants (POP’s)

long-lasting, carbon-based synthetic compounds that do not easily breakdown in the environment, fat-soluble (accumulates & persists in fat instead of passing through body) + endocrine disruptor

• travel long distances through wind & water

• Ex. DDT, PCB’s, PBDEs, Dioxins, Phthalates (plastics)

sources of POPs

• wastewater from industrial processes

• pesticide productions

• emissions

• enter soils/water

• assimilated by plants

• stores in fatty tissues

• eaten by humans

• enter humans through drinking water

fat-soluble toxicants

POPs & heavy metals that don’t dissolve easily in water → don’t easily enter blood (not filtered) → stories in fatty acids & buildup

bioaccumulation

process of toxicants building up in biological tissues during a lifetime to greater concentrations than in the environment

biomagnification

process that occurs when concentrations of toxicants become magnified in higher levels of the food chain

• eating species from a higher trophic level can pose a risk especially to pregnant women, children, & people with fish diets

ex. bioaccumulation of DDT → near extinction of peregrine falcons & bald eagles due to egg shell thinning

case histories

response of people who have been exposed to a substance in the past (mainly comes from autopsies of those with acute symptoms so little exists for low chronic exposure) → tells us little about risk of being exposed

epidemiological studies

large-scale, long term study of a group who have been exposed to a hazard vs. another group with no exposure → use of statistical methods to look for significant difference

• subjects may be exposed to more than one risk factor → confounding effects

• required long wait times for results & do not provide information about the toxicology of new substances but do provide accurate predictions of risk associated with exposure

animal studies

performed in the controlled conditions of a laboratory → provide specific data on toxicity of substances

**human responses are often determines from animal studies w/ mice & rats since they share evolutionary history

dose-response analysis

exposes groups of organisms to different concentrations (doses) of a a chemical in order to measure the response (effect) → results are plotted on graph to create dose-response curve to show probability of certain effect

independent variable

concentration of the chemical (added to food, water, air) → LOGARITHMIC SCALE on x-axis

dependent variable

% of population showing a specified response (death or specific impairment)

what is the unit for mass of toxin/unit of body mass?

mg/kg

• mg is 1/1000 of kg

what unit is used to measure the mass of toxin/volume of water, air, etc?

mg/L

what are the common units?

ppm (parts of a million)

• 1 ppm= 1000 ppB

what shape do dose-response curves have?

s-shaped: low morality at low doses → rapid increase in mortality as dose increases (level off near 100% morality at high doses)

LD50

dose or concentration of the chemical that kills 50% of the population being studied

TD50

the dose required to show a specific toxic effect in 50% of the population

ED50

dose required to show a specific, often beneficial, effect on 50% of the population (similar to TD50 & often reported when substance results in desired effect)

threshold dose

minimum dosage where a specified response starts to occur → cells/tissues/organs can metabolize or excrete low doses of a toxicants → impacts start to show at higher doses

precautionary principle

do not proceed with new actions or at least proceed with extreme caution until the ramifications of those actions are well understand— “assume the worst until proven otherwise”

Ex. EPA, FDA, CDC, Europe

• for each 3 levels of uncertainty, the experiment determines “safe dosage” concentration diving the results by 10 → results are 1000x lower than animal studies

• CONS: may impede pace of technology & hinder economic advance due to higher burden of proof

synergistic effects

interactive impacts that are greater than the sum of their constituent effects

ex. 2+2 = 20

additive effect

mixed toxins that sum up

ex. 2+2 = 4

antagonist effect

mixed toxins that cancel out

ex. 2+2=1

“innocent-until-proven-guilty” approach

assumed a substance is harmless until shown to be harmful → helps technological innovation & economic advancement by limiting initial resting but allows dangerous substances to be widely used before later determination of greater risk

Ex. U.S approach

Toxic Substances Control Act (1976)

directs the EPA to monitor (but not test) thousands of chemicals made in or imported into the US → can ban substances that pose excessive risks but many advocates think its too weak

The Stockholm Convention on POPs

enacted in 2004 & ratified by over 150 nations → set guidelines for phasing out the “dirty dozen”— 12 most dangerous POPs— & encourage the transition to safer alternatives

Delaney Clause (1958) of the food, drug, & cosmetics Act (1938)

bans the use of food additives found to induce cancer in humans or lab animals at any dosage

solid wastes

any discarded material that is not a liquid or gas & is generated in domestic, industrial, business, & agricultural sectors → disposed of in landfills → can contaminate groundwater & release harmful gases if built incorrectly

origins of industrial solid waste (ISW)

mining, farming, construction (demolition)

municipal solid waste (MSW)

waste from home & workplaces other than factories

what are some solid waste migration strategies?

burning waste, restoring habitats as parks, reusing, recycling

sanitary municipal landfill

consists of:

• bottom liner (plastic or clay)

• storm water collection system

• a cap

• methane collection system

advantages of sanitary municipal landfills

cheap, efficient, filled land can be used for other purposes, no shortage of space

disadvantages of sanitary municipal landfills

noise, traffic, dust, releases methane & C02 unless being collected, output approach that encourages waste production, eventually leaks & can contaminate groundwater

incineration of solid wastes

waste is burned at high temperatures → releases air pollution (CO, PM, heavy metals) → need for costly scrubbers and electrostatic

The 3R’s: Reduce, Reuse, Recycle

• Recycling= process by which certain solid waste materials are processed & converted into new products → reduces demand on materials & minerals but process in energy-intensive & can be costly & inconvenient

• Reusing= using objects over & over again

• Reducing= making less waste

electronic waste/e-waste

composed of discarded electronic devices (TV, phones, computers) → metals can leech into groundwater & sent to other countries

food waste & composting

process of organic materials decomposing & can be used as fertilizer but there is odor & rodents

pathogens

a living organism (virus, bacteria, fungi, parasite, worm) that causes an infectious disease → they adapt & evolve to take advantage of humans for their reproduction

infectious disease

capable of being spread or transmitted (ex. HIV, ebola, COVID)

vector

living organism (rat, mosquito, tick) that carry & transmit infectious pathogens to other organisms

tuberculosis (TB)

bacterial (pathogen) infection that targets the lungs & is transmitted by breathing bacteria from body fluids of an infected person (can linger in air for hours) → causes night sweats, fever, coughing blood, treable with access to powerful antibiotics, & leading cause of disease death in developing world

plague

bacterial (pathogen) infection transmitted by fleas that attach to mice & rats through contact or containated human fluids

malaria

parasite protist (pathogen) infection caused by bite from infected mosquitos (most common in Africa)- symptoms like flue & kills children under 5

west nile

virus (pathogen) caused by bite from infected mosquitos → birds are main host but can be transmitted to humans by mosquitos → brain inflammation

zika virus

virus (pathogen) infection caused by bite from infected mosquitos & sexual contact with infected individuals → causes babies to be born with abnormally small heads & damaged brains

coronavirus

through to have first appeared in bats & spread to other animal hosts → transmitted through touching/inhaling fluids of others → fever, cough, pneumonia, diarrhea, asymptomatic

reservoir species

species humans more commonly come in contact with that the coronavirus can mutate to infect the species & humans

severe acute respiratory syndrome (SARs-CoV)

likely transmitted from palm civets to humans in southern China

middle east respiratory syndrome (MERS)

likely transmitted from humans by dromedary camals in Saudi Arabia

severe acute respiratory syndrome (SARs-Cov-21)

suspected of having been transmitted to humans by unknown vector

dysentery

bacterial infection caused by food/water being contaminated with feces → intestinal swelling, blood in feces, & severe hydration

chlorea

bacterial infection caused by drinking infected water → extremely contagious → vomiting, muscle cramps, diarrhea, severe dehydration

Sewage treatment process

1. Primary Treatment: physical removal of large debris (TP, leaves, plastic, sediment) with screens or grates

2. Secondary Treatment: biological breakdown of organic matter by bacteria (aerobic process requiring O2)

3. Tertiary treatment (optional): chemical treatment to reduce nutrient pollution (nitrate, phosphate, ammonia)

4. Disinfection: UV light, ozone, or chlorine is used to kill bacteria & pathogens

5. sludge is disposed in landfills or sent to anaerobic digester → generated methane gas & can be used to generate electricity

6. Screens & grates filter out large soils → allow sediment to settle out & be removed

7. oils & grease are skimmed from top & primary is collected & disposed or sent to aerobic digester

8. O2 bubbles into aeration tank (filled with bacteria that break down organic matter)

9. Effluent is charge dinto surface water with elevated nitrate & phosphate → eutrophication