Freshwater and Marine Communities Flashcards

Global Water Cycle

Major Water Reservoirs: The Earth's water is distributed across several major reservoirs: * The atmosphere. * Ice (glaciers and polar caps). * Oceans. * Lakes. * Rivers. * Groundwater. * Soil.
The Hydrologic Cycle Processes: Water moves between these reservoirs through a series of specific processes: * Transpiration: Also known as evapotranspiration from plants. * Evaporation: Water turning to vapor from land, lakes, and oceans. * Infiltration: The process where water soaks shallowly into the soil, moving through the ground where it can be absorbed by plant roots. * Sheet Flow: The movement of water across the surface of the soil. * Percolation: Water moving deep into the ground to recharge the water table or aquifers. * Collection in Aquifers: Storage of water in the subterranean water table. * Precipitation: Water returning to the surface in the form of rain, snow, or clouds.
Movement Determinants: The specific movement patterns and amounts of water within the hydrologic cycle are primarily determined by patterns of evaporation and precipitation.
Quantitative Data (Reservoirs and Fluxes): * Oceans: $1,350,000,000$ * Ice: $24,000,000$ * Groundwater: $8,200,000$ * Atmospheric Compartment: $13,000$ * Precipitation on Land: $111,000$ * Precipitation on Oceans: $385,000$ * Evaporation from Oceans: $425,000$ * Transpiration/Evaporation from Land: $71,000$ * River Flow: $40,000$ * Net Transport to Land: $40,000$

Rivers and Streams: Lotic Ecosystems

General Characteristics: Lotic (flowing water) systems are defined by their rate of flow and the surrounding geology. These factors determine nutrient flow and overall biodiversity.
Energy Sources: * Autochthonous Sources: Energy derived from photosynthesis occurring within the aquatic system itself, primarily from aquatic plants.
Threats to Lotic Systems: * Dewatering (draining systems of water). * Pollution.
Species Diversity by Stream Type: * Fast-Flowing Rocky Streams: Characterized by cascades and pools. Notable species include the Stream Frog (Amolops gerutu) and the River Toad (Phrynoides asper) found in Malaysia. * Slow-Flowing Meandering Streams: Notable species include the Malaysia Soft-shelled Turtle (Dogania subplana) and the Siberut Island Frog (Pulchrana siberu). * Endangered Habitats: Systems such as those in Idyllwild, CA, harbor endangered species like the Yellow-legged Frog (Rana muscosa).

Rivers as an Ecosystem Continuum

Ecosystem Continuum Concept: Rivers change predictably from headwaters to downstream reaches.
Headwaters (Upstream): Most energy is provided by allochthonous sources (energy originating from outside the system, such as terrestrial leaf litter).
Downstream Reaches: Energy primarily comes from upstream sources and autochthonous production by algae within the river.
Stream Order and Elevation: * Low-Order Streams: Located at higher elevations with no other streams feeding into them. Characteristics include higher oxygen concentration, lower temperatures, and lower nutrient content. * High-Order Streams: Located downstream with other streams feeding into them. Characteristics include lower oxygen concentration, higher temperatures, and higher nutrient content.

Lakes and Ponds: Lentic Ecosystems

General Characteristics: Lentic (still water) systems receive a major portion of their energy from allochthonous sources in the surrounding terrestrial landscape.
System Importance: Lentic systems are critical for human water consumption, food, biodiversity, and transportation. They are often fed by watersheds drained by lotic systems.
Threats: Primarily landscape-related, including pollution and invasive species introduced via sheet flow.
Zonation and Light: Structured by zones related to water depth and light penetration.
Thermal Stratification in Deep Lakes: * Epilimnion: The warm surface layer. * Hypolimnion: The deep, cold water layer. * Thermocline: The boundary layer between the epilimnion and hypolimnion where temperature and water density change rapidly (step-clinal). * Seasonal Dynamics: Stratification develops in summer and disappears during fall and spring water turnover as air temperatures cool.
Lake Zones: * Littoral Zone: Near-shore area. * Pelagic Zone: Open water. * Limnetic Zone: Well-lit open water. * Profundal Zone: Deep, dark water below the limit of effective light penetration. * Benthic Zone: The very bottom of the lake.
Primary Producers: * Lentic: Phytoplankton (microscopic, single-celled photosynthetic organisms suspended in water). * Lotic: Periphyton (freshwater organisms attached to plants or objects projecting above bottom sediments).

Wetlands: Marshes, Swamps, and Bogs

Marshes: * Shallow basins located along the edges of lotic and lentic ecosystems. * Vegetation: Specifically adapted to changing water levels. * Functions: Improve water quality through filtration; used in human aquaculture. * Threats: Pollution, invasive species, and draining.
Swamps: * Dominated by woody plants (trees) and typically found in the floodplains of large rivers. * Functions: Critical habitat for many species and aid in flood control. * Threats: Significant threat from logging. * Biological Radiation: Some lineages, such as the "swamp clade" of geckos in Malaysia and Indonesia, have evolved to inhabit swamp vegetation exclusively near water. Examples include Cyrtodactylus payacola and Cyrtodactylus rosichonarieforum, which are nocturnal and have large red eyes; some even walk on the bottom beneath the water.
Bogs: * Wetland habitats typically found in northern regions, often in depressions created by glacier retreat. * Conditions: Low nutrient content, specific vegetative structure, anoxic (oxygen-poor), and acidic. * Threats: Significant threat of draining for agricultural land use.

Marine Ecosystems: Open Ocean and Coral Reefs

Open Ocean: * One of the least studied ecosystems on the planet, ranging from Arctic and Antarctic to tropical waters. * Primary Production: Major source is algae, but only in surface waters due to light penetration limits. * Economic Value: Commercial fish populations rely on a healthy open ocean. * Threats: Overharvesting of fish, whales, and invertebrates.
Coral Reefs: * Highly diverse ecosystems in subtropical and tropical regions where water temperatures exceed $18^\circ C$ . * Structure: Built around colonial corals, which serve as a living substrate for symbiotic relationships. * Functions: Protect shorelines from flooding/storm surges and increase commercial fishing success. * Threats: Bleaching caused by warming seas and ocean acidification.

Specialized Marine and Coastal Communities

Mangrove Swamps: * Occur at varying salinity levels (saline near open water to brackish inland). * Salinity is altered by tides, rainfall, and lotic system inputs. * Function: Protect inland communities from storm surges. * Threats: Coastal development.
Rocky Intertidal: * Supports diverse plants and sessile invertebrates, which in turn support fish and mobile invertebrates. * Characterized by a strong horizontal gradient of environmental conditions and temporal fluctuations due to tidal cycles. * One of the most harvested environments on Earth.
Estuaries and Salt Marshes: * Estuary Definition: A semi-enclosed coastal body of water with a free connection to the open sea, where seawater is measurably diluted by freshwater from land drainage. * Key Feature: The salinity gradient. * Salt Marshes: Estuarine communities occurring where barrier islands protect a bay from wave action.
Coastal Communities: The most productive and diverse marine communities, occurring in shallow water near shore.
Coral Reef Types: * Fringing reefs. * Barrier reefs. * Atolls.

Physical and Chemical Factors in Marine Systems

Key Physical Factors: * Oxygen Concentration: $O_2$ has lower solubility and diffusion rates in water than in air. * Salinity. * Nutrient Limitation: Limited Nitrogen ( $N$ ) and Phosphorus ( $P$ ). * Light Availability: * Light Attenuation: The change in wavelength with depth. * Light Compensation Point (LCP): The specific depth at which photosynthesis exactly balances respiration ( $CO_2$ in, $O_2$ out). No growth of photosynthetic organisms occurs below the LCP.
Ocean Temperature and Currents: * Ocean temperature is dictated by the sun and a latitudinal gradient similar to land. * Warm water from the equator is distributed via currents driven by Earth's rotation, salinity levels, and wind patterns.

Ocean Chemistry and Acidification

Ocean Acidification Process: Elevated atmospheric $CO_2$ leads to higher $CO_2$ concentrations in ocean waters. This results in the following chemical reactions: $CO_2 + H_2O \rightarrow H_2CO_3$ $H_2CO_3 \rightarrow HCO_3^- + H^+$ $HCO_3^- \rightarrow H^+ + CO_3^{2-}$
Consequences: * Formation of carbonic acid ( $H_2CO_3$ ) lowers the pH of marine systems. * Lower pH dissolves calcium carbonate and decreases calcium carbonate saturation. * This represents a significant threat to marine calcifiers (like coral reefs) whose bodies are composed of calcium carbonate.
Coral Bleaching: Bleaching events occur when ocean temperatures rise, killing the corals and leaving a "bleached" appearance. This leads to a decline in hyperbiodiverse systems, resulting in recruitment failure and decreased coral cover.

Connectivity Between Terrestrial and Aquatic Ecosystems

Example Case Study: El Muerto Island, Mexico: * The island has very scant vegetation. * Allochthonous Energy: The main energy source is derived from the ocean, specifically dead sea lions and intertidal isopods. * Energy Flow: Rotting sea lions attract flies and maggots, which are eaten by the Island Side-blotched Lizard (Uta tumidarostra). The lizards also consume marine isopods. The lizards are then eaten by the El Muerto Island Rattlesnake (Crotalus pyrrhus). * Isotope Evidence: Radioactive isotopes confirm that more energy in this ecosystem comes from the ocean than from the island's photosynthetic land plants.