Ecological Physical Environment and Environmental Chemistry Vocabulary

Physical Environment and Climate Patterns

• Global Climate Drivers:

  • The tilt of the Earth creates optimal planetary conditions for maximum biological diversity.

  • Topography: The physical shape of the land, including elevations, slopes, and structural contours, heavily dictates local microclimates.

  • Distribution of Land Masses vs. Water: Air temperatures over land masses display significantly greater seasonal variation compared to air temperatures over oceans.

• Thermal Properties of Water and Ocean Circulation:

  • Water possesses a high specific heat capacity, absorbing vast amounts of solar radiation and energy with minimal change in temperature.

  • Chemical Basis: Intermolecular hydrogen bonding between adjacent water molecules absorbs incoming heat energy before phase or temperature changes occur.

  • Atmospheric vs. Oceanic Circulation:

  • Atmosphere: Circulates rapidly but holds relatively little heat. Air heats up quickly to its maximum relative thermal capacity upon exposure to solar radiation, dissipating heat rapidly.

  • Oceans: Surface water heats slowly. Oceans feature deep-water circulation processes—including upwelling, underwelling, and vertical mixing into the deep ocean—which effectively spread and dissipate thermal energy across massive fluid volumes.

• Global Temperature Extremes and Ocean Moderation:

  • Arctic Land Masses: Experience annual seasonal temperature ranges of up to $60^\text{o}$ from winter to summer.

  • Arctic Oceans: At identical latitudes, oceanic temperature fluctuations range only between $25^\text{o}$ and $30^\text{o}$ annually (half the variation seen on land).

  • Equatorial Regions: Show minimal seasonal temperature fluctuation, with oceanic areas demonstrating less than half the variation of terrestrial equatorial zones.

  • Climate Change and Ocean Currents: Climate warming threatens to slow critical circulating currents, such as the Atlantic Coast jet stream / conveyer system, fundamentally altering global weather and marine activity.

Altitude, Air Pressure, and Lapse Rate Mechanics

• Lapse Rate Definition:

  • Lapse Rate: The rate at which atmospheric temperature decreases as altitude/elevation increases.

  • Atmospheric Profile: Temperature decreases continuously with altitude throughout the troposphere. Above the troposphere, the trend reverses and temperature increases due to solar radiation absorption by dense gas layers (e.g., the ozone layer). Biology is restricted entirely to the troposphere.

• Mechanisms Driving Environmental Lapse Rate:

  1. Ground Reflectance and Thermal Emanation:

  • At sea level ($0\text{ altitude}$), heat emanates directly from land and water, which have higher specific heat capacities than air.

  • As altitude increases, proximity to ground-level thermal radiation decreases.

  1. Air Pressure and Molecular Density:

  • At sea level, atmospheric pressure is approximately $1\text{ atmosphere}$, compressing air molecules together.

  • High-density air near the surface contains concentrated greenhouse gases ($CO_2$, $H_2O\text{ vapor}$, $N_2O$) that absorb re-radiated heat.

  • Higher elevations experience lower atmospheric pressure and reduced air molecule density, leaving fewer gas molecules to absorb radiation.

  1. Adiabatic Cooling:

  • Definition: The thermodynamic process by which air expands as it rises into regions of lower atmospheric pressure.

  • Mechanism: As air parcels transition from high pressure to low pressure, physical molecular expansion causes the air parcel to release heat, causing a drop in temperature.

  1. Wind Speed and Convective Dissipation:

  • Wind speeds increase at higher elevations due to reduced friction from ground topography.

  • Increased wind speeds generate convection currents that rapidly sweep away heat emanating from mountain surfaces.

Long-Term Climatic Oscillations and Ecological Impacts

• Pacific Decadal Oscillation (PDO):

  • Definition: A large-scale, long-term ocean-atmosphere climate cycle featuring alternating warming and cooling phases across the Pacific Ocean lasting $20\text{ to }30\text{ years}$.

  • Comparison to El Niño/La Niña: Operates on a similar mechanism to El Niño/Southern Oscillation (ENSO), but spans multiple decades rather than single-year intervals.

  • Recent Cycles: A cooling phase began around 2008 (lasting approximately 20 years into the current period), characterized by cooler ocean temperatures off the Western Pacific coast.

  • Ecological Impacts: The PDO directly dictates the abundance, distribution, and movement of marine organisms (e.g., historical salmon catches show enhanced migration and survival during cooler ocean phases) and influences global terrestrial weather patterns.

• Methodological Challenges of Decadal Climate Cycles:

  • Research Time Scales:

  • Most field ecology grants cover $2\text{ to }5\text{ years}$, operating entirely within a single phase of a decadal oscillation.

  • Long Term Ecological Research (LTER) programs (such as National Science Foundation studies in Puerto Rican forests) provide rare multi-decade datasets.

  • Analytical Pitfall: Comparing short-term population data taken 30 years apart may lead researchers to incorrectly attribute natural population shifts to local human disruption or climate change rather than natural multi-decadal cycles.

  • Evolutionary and Physiological Consequences for Organisms:

  • Multi-decadal cycles exceed the lifespan of almost all organisms, except long-lived animals such as humans, elephants, horses, and whales.

  • Species tolerance limits follow a standard bell-shaped curve for temperature and moisture.

  • Short-Lived Organisms (e.g., Insects): Undergo numerous generations within a single 20-30 year phase, rapidly evolving adaptive traits to match the current phase (e.g., cooling phase). When the phase shifts, the population drops sharply before evolving to fit the new phase.

  • Long-Lived Organisms: Cannot adapt evolutionary traits rapidly between phase shifts, resulting in prolonged physiological stress when oscillation phases change.

Chemical Factors in Marine and Terrestrial Environments: Salinity

• Major Environmental Chemicals: Salinity, Acidity ($pH$), and Dissolved Oxygen ($O_2$).

• Salinity Fundamentals:

  • Chemical Diversity: Includes table salt ($NaCl$) along with critical nutrient salts such as sodium nitrate ($NaNO_3$) and calcium nitrate ($Ca(NO_3)_2$).

  • Dissolved salts dissociate into positively charged cations and negatively charged anions. Anions neutralize acidity by binding free hydrogen ions ($H^+$).

  • Evaporation: Concentrates dissolved ions, causing salinity to increase.

  • Precipitation: Adds fresh water, causing salinity to decrease.

  • Sea Ice Melting: Dilutes ocean water with fresh water, decreasing salinity.

• Global Ocean Salinity Distribution:

  • Equatorial Dynamics: Salinity is slightly lower directly at the Equator despite intense evaporation, because extreme heat triggers intense localized precipitation.

  • Hadley Cells: Intense equatorial solar heating causes warm, moist air to evaporate and rise, dropping heavy rain directly over the Equator. The dry air moves north and south, descending at approximately $30^\text{o}$ latitude (subtropics), where high evaporation and minimal rain create the highest global ocean salinities.

  • High Latitudes and Poles: Salinity decreases toward the poles. Annual seasonal temperature swings up to $60^\text{o}$ melt polar ice, adding fresh water. Because solar evaporation at the poles is near zero, precipitation and ice melt lower overall salinity.

• Salinity Extremes and Soil Salinization:

  • Ocean average salinity ranges from $33\text{ to }37\text{ parts per trillion}$ (typically around $35\text{ parts per trillion}$).

  • Hypersaline Inland Lakes:

  • Dead Sea: $250\text{ parts per trillion}$.

  • Great Salt Lake: $150\text{ parts per trillion}$.

  • Formed in arid basins where mineral-rich runoff enters from surrounding rock weathering and continuous evaporation leaves salts trapped with no outflow mechanism.

  • Soil Salinization:

  • Natural salinization occurs in coastal salt marshes, tidal estuaries, and arid regions with extreme evaporation.

  • Agricultural salinization occurs when persistent irrigation in dry climates evaporates, leaving residual fresh-water mineral salts behind in topsoil until crop land degrades.

Environmental Acidity, pH Mechanics, and Geological Drivers

• pH Scale Mechanics:

  • Acidity: Concentration of hydrogen ions ($H^+$).

  • Alkalinity: Capacity to act as a base by absorbing $H^+$ ions, measured via hydroxide ion ($OH^-$) availability.

  • Logarithmic Formula:     $pH = -\text{log}_{10}[H^+]$

  • Concentration Calculations:

  • Neutral pure water ($pH = 7$) has a hydrogen ion concentration of:       $[H^+] = 10^{-7}\text{ mol/L}$

  • A difference of 1 $pH$ unit ($pH = 7$ vs. $pH = 6$) represents a 10-fold ($10\times$) change in $H^+$ concentration.

  • A difference of 2 $pH$ units ($pH = 7$ vs. $pH = 5$) represents a 100-fold ($100\times$) change in $H^+$ concentration.

  • Strongly acidic solutions ($pH = 1$) contain $10^{-1}\text{ mol/L}$ of $H^+$ ions.

• Geological and Environmental Drivers of pH:

  • Organisms exhibit specific bell-shaped tolerance curves for $pH$.

  • Limestone Parent Rock (Basic): Composed of calcium carbonate ($CaCO_3$), which breaks down into carbonate ($CO_3^{2-}$) and bicarbonate ($HCO_3^-$) anions. These negatively charged ions bind free $H^+$ ions, neutralizing acidity and raising $pH$.

  • Granite Bedrock (Acidic): Common in regions like Maine; releases aluminum ions ($Al^{3+}$) that react with water via hydrolysis, splitting $H_2O$ and releasing excess $H^+$ ions to acidify soils.

  • Ocean Acidification:

  • Open oceans historically maintain stable $pH$, but rising atmospheric carbon dioxide ($CO_2$) over recent years has driven rapid acidification.

  • Chemical Reaction:       $CO_2 + H_2O \rightarrow H_2CO_3$

  • Carbonic acid ($H_2CO_3$) dissociates into $H^+$ ions, disrupting sensitive marine species, particularly reef-building corals.

  • Other Acidification Processes: Decomposition of organic matter, leaching of basic mineral cations, acid rain, and acid mine drainage (exposure of sulfide-bearing bedrock during mining).

Environmental Oxygen Availability and Ecological Adaptations

• Role of Oxygen in Respiration:

  • Oxygen ($O_2$) acts as the terminal electron acceptor in aerobic cellular respiration, maximizing ATP production compared to anaerobic pathways.

  • Hypoxia: Environments characterized by low dissolved oxygen concentrations.

• Altitudinal Oxygen Variation:

  • Atmospheric pressure drops at higher elevations, reducing total air density and total oxygen molecules per unit volume.

  • Plant Adaptations: Plants are generally unaffected by high-altitude oxygen drops because their metabolic respiration requirements are low. Plants require $CO_2$ for photosynthesis. Reduced oxygen at high elevations decreases photorespiration—a wasteful process where the enzyme Rubisco accidentally binds $O_2$ instead of $CO_2$.

  • Animal Adaptations: Animals at high elevations face severe metabolic limits. Evolutionary adaptations include higher hemoglobin oxygen-affinity and elevated red blood cell counts.

• Edaphic and Aquatic Oxygen Dynamics:

  • Soil Oxygen: Waterlogged soils block gas diffusion, depriving roots of oxygen for cellular respiration and causing root rot in non-adapted plants.

  • Aquatic Systems:

  • Turbulence (waves, fast-flowing streams) increases dissolved oxygen concentrations.

  • Fish Kills: Triggered when excess organic waste enters streams, fueling massive bacterial and algal blooms. When these organisms die, microbial decomposers consume all available dissolved oxygen, suffocating fish.

  • Shark Respiratory Mechanisms:

  • Buccal Pumping: Species such as Nurse sharks actively pump water across their gills while remaining stationary on the ocean floor.

  • Obligate Ram Ventilators: Species such as Great White sharks and Mako sharks cannot execute buccal pumping and must continuously swim forward to force oxygenated water over their gills.