AICE MARINE CHAPTER 3

Organism Interactions

Types of Interactions

• Mutualism: Both species benefit from the interaction. Example: Coral and zooxanthellae, where coral provides a habitat for algae, and in return, the algae produce oxygen and nutrients for the coral.

• Commensalism: One species benefits while the other is unaffected. Example: Cleaner fish and larger fish, where cleaner fish eat parasites off larger fish without harming them.

• Parasitism: One species benefits at the expense of another. Example: Ectoparasites like salmon lice that live on the skin of fish, causing harm.

Specific Examples of Mutualism

• Coral and Zooxanthellae: Coral hosts single-celled algae (zooxanthellae) that perform photosynthesis, providing glucose and oxygen to the coral, while receiving protection and access to sunlight.

• Cleaner Fish: Species like gobies and wrasses clean parasites off larger fish, benefiting from nutrition while helping the host fish reduce infection risk.

• Boxer Crabs and Anemones: Crabs gain protection from anemones' stinging cells, while anemones receive food scraps from the crabs.

Feeding Relationships

Trophic Levels and Food Chains

• Trophic Levels: Organisms are categorized based on their feeding position in a food chain. Producers (autotrophs) are at the first level, followed by primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers (top predators).

• Food Chains vs. Food Webs: A food chain is a linear sequence of organisms where each is eaten by the next. A food web is a complex network of interconnected food chains, illustrating the multiple feeding relationships in an ecosystem.

• Energy Flow: Energy flows through trophic levels, with only about 10% of energy being transferred from one level to the next due to energy loss through metabolic processes.

Predator-Prey Dynamics

• Predator-Prey Relationships: Predators are typically secondary consumers or higher, and they have adaptations like speed and camouflage to hunt effectively. Prey species develop defenses such as spines or camouflage to evade predators.

• Population Effects: Predator populations are usually smaller than prey populations due to energy loss between levels and higher individual biomass in predators. This dynamic helps regulate prey populations.

• Example of Coevolution: The relationship between viceroy and monarch butterflies, where viceroys mimic the toxic monarchs to avoid predation.

Photosynthesis and Primary Productivity

Photosynthesis Process

• Photosynthesis: The process by which autotrophs convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. Key factors include light intensity, temperature, and nutrient availability.

• Types of Autotrophs: Photoautotrophs use light energy (e.g., plants, algae), while chemoautotrophs derive energy from chemical reactions (e.g., bacteria near hydrothermal vents).

• Primary Producers: Organisms like phytoplankton, seagrass, and kelp that form the base of the food web by converting sunlight into energy.

Measuring Productivity

• Gross Primary Productivity (GPP): The total amount of energy captured by photosynthesis in a given area and time.

• Net Primary Productivity (NPP): The energy available to consumers after accounting for the energy used by producers for respiration (NPP = GPP - Respiration).

• Productivity Experiments: Methods to measure productivity include comparing oxygen levels in light and dark conditions to assess rates of photosynthesis.

Ecosystem Dynamics and Energy Flow

Energy Transfer in Ecosystems

• Energy Flow: Energy is transferred through trophic levels, with primary producers converting solar energy into biomass, which is then consumed by herbivores and carnivores.

• Detritivores: Organisms that feed on dead organic matter, playing a crucial role in nutrient cycling within ecosystems.

• Compensation Point: The depth in water where the rate of photosynthesis equals the rate of respiration, indicating the limit of productive photosynthesis.

Impact of Invasive Species

• Lionfish: An example of an invasive predator in the Caribbean that disrupts local ecosystems by preying on native fish populations, leading to declines in biodiversity.

• Crown-of-Thorns Starfish: A predator of coral that can lead to coral reef degradation when populations are unchecked, illustrating the delicate balance in marine ecosystems.

• Population Dynamics: The interaction between predator and prey populations can lead to oscillations, where the predator population lags behind the prey population due to reproductive rates and resource availability.

Ecosystem Productivity and Energy Transfer

Key Concepts of Ecosystem Productivity

• Ecosystem productivity refers to the rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances.

• Primary productivity is the amount of biomass produced by primary producers (e.g., plants, phytoplankton) in a given area over a specific time period.

• Secondary productivity is the generation of biomass by heterotrophic organisms (consumers) that consume primary producers.

Energy Transfer Efficiency

• Energy transfer efficiency is typically around 10% between trophic levels, meaning only a fraction of energy is passed on to the next level.

• Factors affecting energy transfer include the amount of food consumed, digestibility, energy used for movement, and waste loss.

• Example: If the sun radiates 1,600,000 kJ/m²/year and phytoplankton captures 153,000 kJ/m²/year, the efficiency can be calculated as (153,000/1,600,000) x 100 = 9.56%.

Changes in Ecosystem Productivity

• Natural fluctuations in productivity can lead to ecosystem breakdowns, such as hypoxic conditions caused by algal blooms.

• Eutrophication is a process where excess nutrients lead to algal blooms, which can deplete oxygen in water and harm aquatic life.

• Example: Toxic algal blooms can produce harmful effects on marine life and human health.

Nutrient Cycling in Ecosystems

Major Nutrients and Their Roles

• Nitrogen is essential for amino acids, proteins, and DNA synthesis.

• Phosphorus is crucial for energy transfer (ATP) and is found in bones and teeth.

• Carbon is the backbone of organic molecules and is involved in energy storage and transfer.

Biotic and Abiotic Phases of Nutrient Cycling

• Biotic phase includes living organisms such as producers, consumers, and decomposers that contribute to nutrient cycling.

• Abiotic phase includes inorganic compounds and elements that play a role in nutrient availability, such as gases and sediments.

• Nutrient cycling is vital for maintaining ecosystem health and productivity.

Reservoirs and Residence Times

• A reservoir is a portion of the abiotic component of a nutrient cycle where nutrients can remain for extended periods.

• Residence time varies for different nutrients; for example, phosphorus can have a residence time of 20,000 to 100,000 years, while nitrogen is around 72,000 years.

• Understanding residence times helps in managing nutrient inputs and outputs in ecosystems.

Human Impact on Nutrient Cycling

Harvesting and Its Effects

• Human activities, such as fishing and agriculture, significantly impact nutrient cycling by removing species and nutrients from ecosystems.

• In 2010, the global catch of marine species was estimated at 109 million metric tons, affecting nutrient availability in marine environments.

• Sustainable practices are essential to mitigate the negative impacts of nutrient removal.

Pollution and Eutrophication

• Nutrient runoff from agriculture and urban areas can lead to eutrophication, causing algal blooms and dead zones in aquatic systems.

• Algal blooms can produce toxins that affect marine life and human health, highlighting the need for pollution control measures.

• Strategies to reduce nutrient pollution include better agricultural practices and wastewater treatment improvements.

Upwelling and Nutrient Distribution

• Upwelling brings nutrient-rich deep water to the surface, supporting high productivity in coastal regions.

• Coastal upwelling is driven by wind patterns and can significantly enhance fish populations, making it crucial for fisheries.

• Understanding upwelling dynamics is important for managing marine resources and ecosystems.