intro to marine ecotox Flashcards
aquatic toxicology
the study of the effects of chemicals and other natural and anthropogenic materials (i.e. toxic agents) on aquatic organisms
ecotoxicology
a subset of aquatic toxicology that evaluates the changes in the communities of individual organisms in response to a toxic agent
toxicokinetics
the movement and transformation of pollutant compounds from the aquatic environment and into organisms.
endpoints (definition)
signals that indicate adverse impacts caused by exposure and include:
endpoints (examples)
- Lethality - the number of organisms killed or survived after an exposure event
- Reproductive success - in aquatic organisms this can be measured by egg production, hatchability, and recruitment—the number of juvenile organisms surviving to adulthood
- Whole body or organ condition factors - these include physical measurements of length, weight, and health indices (e.g. motility, lethargy, behavior changes)
- Mutagenesis or teratogenesis - molecular changes leading to tumors, birth defects, and cancer
bioaccumulation
the accumulation of environmental toxins within the body of an organism
PAH
polycyclic aromatic hydrocarbons -persistent type of contaminant associated with oil and gas exploration
biomedical toxicology
focuses on human health, using mammalian models as the basis for experimentation, testing, and data interpretation. The priority is to reduce the harmful effects of environmental pollutants on human populations.
ecotoxicology vs mammalian toxicology
ecotox :
- protect communities of diverse species from toxic substances
- can experiment directly on species of concern
- organisms live in variable environmental conditions, are mostly poikilothermic. Toxicity may not be predictable
- External exposure (dose) and duration from water, sediment can be known—actual absorbed does is often determined experimentally using metabolism and bioaccumulation and bioconcentration studies
- less research, emphasis of toxic effects and threshold concentrations, regulatory purposes
- test methods are new and usefulness uncertain
mammalian toxicology:
- protect humans
- uses animal models, cant feasibly experiment on humans
- homeothermic organisms, toxicity predictable
- doses of chemicals can be measured directly and accurately, administered through several routes
- extensive research, focus on mechanisms of toxic action
- test methods well developed, usefulness/limits understood
Phase of physical environment (4)
- Air
- Water
- Soil and sediment
- Biota (Tissue of living organisms)
Physical transport
the movement of chemical compounds without reaction or interaction with other environmental phases
reactivity
the chemical or biochemical reactions of chemical compounds with other environmental phases
Netric zone
nearshore regions
pelagic zone
deep ocean regions
abiotic components
nonliving elements that comprise the physical aquatic environment, including temperature, pH, salinity, dissolved gases, suspended particulates, and many more
Xenobiotics
any foreign substances or exogenous chemicals (e.g. from outside the organism) which the body does not recognize
duration
also referred to as an exposure event and can be acute or chronic in type. For example, intermittent chemical spills are classified as acute exposure events, where as continuous discharge of a waste stream into a water body is classified as a chronic exposure event.
resiliency properties
properties of an ecosystem enabling it to resist change that result from the presence of a pollutant. These properties include pH buffering capacity, dissolved organic matter (DOM) concentrations of the water column, tidal flushing events, and more
water
- facilitates chemical reactions
- conduit for transport of nutrients and waste
water (specific heat)
water has highest specific heat of common fluids. Takes a lot of energy to alter water temperature. Buffering effect, keeps organisms in narrow range of temperature. Specific heat is LOWERED by addition of solutes.
water (density)
highest water density at 4 degrees C. Density decreases above and below this point. This phenomenon causes water to freeze from the surface downward. Cold water is more dense than warm, so it sinks, leads to vertical mixing in shallow water and thermal stratification in deep water.
viscosity
characterizes a liquids resistance to flow (high viscosity = high resistance). measured in poise/centipoise
viscosity of water
increases with decreasing temperature. viscosity caused by hydrogen bonds resulted in internal friction . affects the energy output of organisms via locomotion
Reynolds number
(Re) dimensionless value. Predicts laminar or turbulent flow. Ratio of momentum to viscosity.
Re formula
ReD = pVD/u = VD/v
V is flow velocity (velocity of the fluid with respect to the object)
D is characteristic linear dimension (related to the shape of the object)
ρ is fluid density
μ is dynamic viscosity (fluid)
ν is kinematic viscosity (the velocity of the fluid)
Laminar flow
Re < 2000
Rare, particles move in straight lines, layers of water move over each other at different velocities with no mixing
Turbulent flow
Re > 2000
high velocity fluid, particles move irregularly. Average motion is in one direction, common
surface tension
water has high surface tension due to hydrogen bonds in all directions but the surface-air interface. The surface has higher potential energy and is under tension.
surface tension relationship with other properties of water
ST decreases with increasing temperature
ST decreases with increasing conc. of organic substances in column
ST increases slightly in presence of dissolved salts
Substances that lower surface tension, such as organic matter, become positively sorbed to particulates. As such, concentrations of chemical compounds in the aqueous phase are affected by the interfacial tension between the substance (organic matter) and water.
turbidity
presence of suspended solids
conservative components of sea water
most abundant
non-reactive and have long residence times in the ocean water. They include: chlorine, sodium, calcium, potassium, magnesium, and sulfate.
together they make up 99% of dissolved solute, sodium and chlorine comprise 86% alone.
in estuarine and land locked seas elements may not be acting conservatively, especially with riverine input.
The ratio of conservative components to chloride concentrations are the same in all seawater.
nonconservative components of water
chemically or biologically active, vary from place to place in the ocean
O2, CO2, H2S, and more
potassium, phosphate
organic compounds like amino acids and humic substances
sand, clay, microorganisms
trace metals nickel, lithium, and iron
non conservative components comprise a very small percentage of total solute
salt
ocean salinity: 33-37%, average 35%
Venice System: marine (ocean water) is greater than 30 percent, estuaries range between 0.5 and 30 percent and freshwaters are those less than 0.5 percent.
oxygen
most oxygen in the water column comes from the atmosphere. Dissolution from atmosphere is primary means of reoxygenation after consumption of oxygen by organisms.
concentration of dissolved oxygen regulates organismal and metabolic processes (cellular respiration and decomp).
factors affecting atmospheric o2 dissolution rate
wave action - increases o2 conc. through aeration
partial pressure - greater diff. in pp between air and water increases dissolution of o2 based on Henry’s Law
photosynthetic algae - produces oxygen dissolved in column, not an efficient means of reoxygenation
solubility of oxygen in water
increase temp decreases solubility
increase salinity decrease solubility
hypoxia
low oxygen water, less than 2mg/L dissolved oxygen
anoxia
complete depletion of dissolved oxygen
carbon dioxide
along with oxygen most abundant gas in fresh/sea water
highly soluble in natural waters, solubility varies due to equilibrium with bicarbonate (HCO3-) and carbonate (CO3-2) ions
co2 speciation
co2 speciation is pH dependent. Buffer action prevents shifts in acidity/alkalinity.
pH < 6, CO2 predominates
pH 6-10, HCO3- predominates (most natural waters)
pH>10, CO3-2 predominates
co2 and biological processes
CO2 regulates plant growth and cellular respiration. CO2 is derived from bacterial decomposition of organic matter, a form of cellular respiration. some reactions between acids and carbonate compounds release CO2, and the atmosphere supplies some CO2.
organic constituents
dissolved solids include hydrocarbons, carbohydrates, lipids, fatty acids, and amino and nucleic acids
organic matter in the aqueous environment
an important source of electrons that drive biologically mediated redox reactions.
Heterotrophic organisms require organic compounds for carbo and chemical energy source for cell metabolic functions inc. respiration.
what determines the distribution of organic compounds in the water column?
biological activity and the biogeochemical cycling of carbonaceous material
autochthonous sources
carbon derived from primary production (photosynthesis) and other autotrophic processes
largest fraction of POC in algae-dominated systems and includes biomolecules of lipids, pigments, proteins, and polysaccharides. settle slowly in the water column and undergo microbial degradation. degradation continues after this fraction of organic matter reaches the sediments.
allochthonous sources
plant and soil organic matter transported from the watershed into marine waters. These compounds are rich in plant structural material including lignins and cellulose. largely biologically recalcitrant and tier uptake and turnover in the water column happens slowly.
POC
Particulate organic carbon
primary productivity
plants assimilate energy by photosynthesis and produce biomass (glucose). transferred to heterotrophic consumers (primary and secondary)
photosynthesis
6CO2 + 6H20 + light energy = C6H12O6 + 6O2
or
inorganic carbon + nutrients + light energy = biomass + heat
GPP
gross primary production
total amount of energy fixed by plant matter.
NPP
Net primary production
total amount of energy available for plant growth and reproduction after accounting for respiration
NPP = GPP - respiration
particulate vs dissolved matter
particles retained by greater than .45 micrometer filter are solids or particulate matter and include sand, clay, microorganisms, and more
particles that pass through the .45 um filter are refereed to as dissolved matter and include colloidal compounds such as humic acid polymers and polysaccharides
dissolved vs particulate organic matter
DOM vs POM
dissolved organic matter can adsorb to particles in the water column to from aggregates of POM.
DOC
Dissolved organic carbon
chemically reactive fraction of the compound and provides the mass of organic carbon (OC) dissolved in water. measure of the organic molecules that make up the dissolved organic load in the water column.
POC
Particulate organic carbon, analogous to suspended organic carbon and is comprised of plant and animal organic matter and silt and clay.
TOC
total organic carbon in the aquatic system, sum of DOC, POC, and colloidal particles. Organic matter refers to the whole molecules and includes oxygen and hydrogen atoms. These concentrations are difficult to quantify so TOC is used instead.
seawater DOC concentration
seawater has low DOC concentration (ranges from 1.0 mg/L in surface water to 0.5 mg/L in deep water system)
surface water has higher concentration due to photosynthetic activity of phytoplankton (also source of POC due to aggregation)
seawater POC concentration
less than DOC concentration, range from 0.01 to 0.1 mg/L.
coastal water DOC
coastal waters have higher concentrations of DOC due to increased rates of primary productivity, range from 1-3 mg/L. Organic matter is also introduced from riverine and terrestrial sources. DOC of larger rivers ranges from 2-10 mg/L. Increased concentrations of suspended solids (Total suspended solids (TSS)) strongly related to sediment loading and river discharge
estuary DOC
concentration between river and marine level
relationship between salinity and DOC
linear, inverse. Higher salinity, lower DOC
humic substances
high molecular weight (500-5000 g/mol)
generated by microbial decomposition of organic matter
3 types: fulvic acid, humic acid, and humin (determined by solubility)
heterogonous mixtures of compounds, no single structural formula
natural chelating agents, affect the distribution and fate of aquatic pollutants
fulvic acid
soluble in acid AND alkali environment
provides binding sites for metals
precipitates metal ion out of the solution
without fulvic acids, metal ions would partition into the sediment, form of phase transport.
represents most of the humic material in water
humic acid
insoluble in acid, soluble in alkali environment
effectively exchange cation and organic substances with water, creating a nonpolar environment into which hydrophobic chemicals escape. also can reduce oxidized metal species, allowing the metal ion to be fixed to the humic matter
fixation makes metal unavailable for solubilization or uptake by living organisms (biounavailable)
humic matter in seawater
low concentration (0.06 to 0.6 mg C/L
properties of humic substances and their functions in soil
Properties and Function of Humic Material in Soils and Sediments
Properties
Comments
Function in Soil
Color
Dark color of soils is caused by organic matter
Facilitates soil warming
Water retention
Organic matter can hold up to 20 times its weight in water
Improves moisture retention of soils
Combination with clay minerals
Joins soil particles into structural aggregates
Permits gas exchange; stabilizes soil structure; increase permeability
Chelation
Forms stable complexes with metal ions
Buffers the available of metals to vegetation
Solubility in water
Insolubility of organic matter results from its association with clay; source of dissolved organic matter
Exports recalcitrant dissolved organic matter to adjacent aquatic systems
pH
Organic matter buffers soil pH in slightly acidic, neutral, and alkaline soils
Helps maintain a relatively constant pH
Cation exchange
Total acidities of humus fractions range from 3, 000 to 14,000 mmol/kg
Increase the cation exchange capacity (CEC) of the soil; 20 to 70 percent of the CEC capacity is due to organic matter
Mineralization
Decomposition of organic matter produces gases and nutrients
Energy source for microbes; source of nutrients for plan growth; source of greenhouse gases
Combination with organic molecules
Affects bioavailability, persistence and biodegradability of toxic organic compounds
Decreases bioavailability of toxic organic compounds to biota
nutrient remineralization
organic matter is consumed by heterotrophs and passed through food chain to drive biologically mediated reactions like cell respiration. Biochemical processes convert nitrogen, phosphorous, and carbon to soluble forms and increase nutrient recycling rates and concentrations.
solubility of xenobiotics
POM in the water column can bind to xenobiotics, can remain suspended in the water column, or be deposited on the sediment surface. (particle size, conc. , polarity, and spatial distribution influence the adsorption of foreign chemicals onto suspended particles). xenobiotics bound to particles in the aquatic environment reduce the bioavailability of potentially toxic chemical compounds to living organisms. soluble chem are more available for uptake/ more toxic to organisms
active layer of sediment-water interface
top 10cm of aquatic sediment
suspended aquatic sediments
0,1-200 micrometers in diameter, include fine sand, silt, and clays. Typically heterogenous mixtures and can include organic biota. inorganic constituents include silica, alumina, and iron- manganese oxides. can be pure mineral to pure organic
clay particles
substantial adsorptive capacity due to large surface area to volume ratio and surface charge (-)
Exchangeable cation status
(ECS) ability of clay particles to exchange cations with the aqueous phase
cation exchange capacity
is the amount of exchangeable cations held in the soil. It is a measure of the capacity of a sediment (solid phase) to sorb cations and it varies based on both pH and salinity.
freshwater sediment CEC
20-30 milliequivalents/100g
freshwater sediment ECS
range from less than 1 to 20 milliequivalents/100g
pore/interstitial water
fluid in open spaces between sediment particles.
adsorption
chemical compounds are taken up by surface interaction with solids
absorption
chemical compounds are incorporated into the body of the material (matrix) to which it is bound
partitioning of nonionic nonpolar molecules
partitioned onto the organic carbon fraction contained in marine sediments
partitioning of moderately polar organic molecules
sorbed through hydrogen bonding, cation exchange, and nonpolar partitioning interactions between the compound and the sediment surface.
advection
movement of fluid masses carrying pollutants
diffusion
the natural tendency of molecules to move from regions of higher concentration to regions of lower concentration. referred to as Fickian transport or molecular diffusion. approximated by turbulent mixing (eddies, stream flow)
convection
the vertical movement or advection of water
bioturbation
the restructuring of sediment deposits by benthic organisms. alters the physical processes that mediate chemical transport
(burrowing, swimming)
increases mobility, solubility, bioavailability of previously sequestered chemical compounds.
bioturbation marine vs freshwater
effects of bioturbation are greater in marine ecosystem due to larger organisms that disturb the sediment layer (crustaceans, polychaetes, mollusks)
oxic zone
upper 10cm of marine sediments
relatively homogeneous chemical distribution
oxidizing chemical reactions predominate
anoxic sediments
well defined concentration gradients for particular chemical compounds (reducing reactions predominate in anoxic sediment layers)
ingestion
plays largest role in bioaccumulation of environmental contaminants in aquatic organisms
what abiotic processes cause movement of contaminant out of sediment into porewater or water column
1 elevation of salinity, changes speciation of compounds
2 changes in oxidation/reduction state of sediment layer. changes speciation of chemical compounds
3 reductions in sediment pH, releases mobile, free organic compounds and metals into the aqueous phase
4 presence of complexing agents, releases organically bounds organic compounds and metals into the aqueous phase
reactions in natural aquatic systems:
Acid-base reactions Complexations Dissolution-precipitation reactions Oxidation-reduction reactions Sorption-desorption mechanisms Hydrolysis reactions Photolysis reactions
