Texas Aquatic Science Unit 4: Disruption & Homeostasis

Unit 4: Disruption & Homeostasis of Aquatic Communities

• This unit covers the disruption and homeostasis of aquatic communities.
• The content is relevant to Texas Aquatic Science courses (1AB, 2E-J, 3ABDEF, 4B, & 11B).

4B: Positive & Negative Feedback Cycles

Positive Feedback Cycles

• Positive feedback cycles respond to changes by increasing the initial change.
• Example: Eutrophication - pollutants from runoff increase algal blooms.
• Algal blooms block sunlight, hindering photosynthesis in producers, impacting the aquatic food chain.
• Invasive species thrive in new ecosystems, outcompeting native organisms for resources.

Negative Feedback Cycles

• Negative feedback cycles counteract changes to stabilize conditions.
• Example: Carrying capacity - average population sizes are limited by environmental factors (food, water, shelter, mates).
• Community dynamics - how members of an aquatic community interact and adapt over time.

4B: Cause & Effect

• Too much rain: Leads to flooding (water level exceeding capacity).
• Not enough rain: Leads to drought (water loss from soil and water bodies).
• Increased ocean temperature & pollution: Coral reefs die off, and ocean producers decline (Acidification).
• Zebra mussels introduced: Exponential growth in their population.
• Polluted water: Ecosystem degradation (dead zones).
• Water temperature change: Organism death and habitat changes.
• Pollution introduction: Increased algal blooms (eutrophication), threatening other species.
• Severe winters: Bird migration.
• Ideal mating conditions: Spawning migrations in specific fish species.

11B: Factors Affecting Aquatic Population Cycles

Precipitation and Evaporation Rates

• Precipitation amount affects aquatic plant life.
• Evaporation rate, influenced by global warming, impacts lake size.

Acidification

• Increased pollution and ocean warming harm coral populations.
• Acidification causes coral bleaching, impacting habitat and ocean food chains.

Exponential Growth

• Invasive species (e.g., apple snail, zebra mussels) thrive in new environments, due to lack of predators.
• Water scarcity due to growing human population further affects aquatic ecosystems.

Dead Zones

• Eutrophication causes low oxygen (hypoxic) zones, harming life in aquatic ecosystems (e.g., Gulf Dead Zone, Baltic Sea, Lake Erie).

Water Temperature

• Global warming increases water temperature, melts ice caps, alters pH, and increases evaporation rates.
• Impacts aquatic organism metabolic rates.

Pollution

• Point and non-point source pollution (sewage, runoff) degrade water quality and damage aquatic food chains.
• Pollution leads to eutrophication creating dead zones.

Seasons

• Currents, weather patterns, upwelling, and migration patterns alter aquatic ecosystems in response to seasons.