marine bio 16 kelp and sea otters

Overview of Coastal Marine Ecosystems

• Focus on ecosystems dominated by seaweeds and macroalgae.

• Diversity levels and disturbance levels in systems.

Production and Growth Models

• Importance of the rate of production in ecosystems.

• Exponential growth model described by the equation:

  • $dN/dt = rN(1 - N/K)$

• When population size, n, is very small compared to carrying capacity, K:

  • Growth rate approaches:

  • $dN/dt = rN$

  • Indicates exponential growth as resources are initially abundant.

• As population size, n, nears K:

  • Growth rate approaches zero:

  • $dN/dt = 0$

  • Logistic growth curve shown, where resources are fully utilized.

• Purpose of the model:

  • Simplified representation to make comparisons and predictions without perfectly reflecting nature.

  • Allows testing of hypotheses through experiments and long-term observations.

Examples of Reproductive Strategies

• Concept of semelparity vs. iteroparity:

  • Example highlighted: semelparity in spawning species that die post-reproduction.

  • Iteroparity (from Latin ‘itero’ meaning to repeat) allows for multiple reproductive cycles.

Coastal Habitats and Zonation Patterns

• Description of rocky intertidal zones and deeper subtidal environments.

• Nutrient flow and influence of land on coastal ecosystems emphasizes the connection between terrestrial and marine environments.

• Zonation seen in reefs vs. subtidal kelp habitats:

  • Zonation pronounced in intertidal habitats due to exposure to air vs. submerged subtidal areas where influences differ.

Nutrient Dynamics and Photosynthesis

• Importance of nutrient content in colder waters, allowing for high productivity compared to tropical waters where nutrients are depleted throughout the year.

• Kelp forests imagery, relevance of cold water dynamics to their growth and nutrient absorption.

Chemical and Physical Adaptations

• Specialized structures in brown algae such as:

  • Air bladders to support flotation.

  • Distinct morphological parts like fronds, holdfasts, and stipes.

• Alteration of generations in kelps:

  • Large sporophyte generation produces male and female spores, leading to gametophyte development.

Echinoderm Habitats and Ecosystems

• Echinoderms’ absence in fresh or brackish systems due to their unique water vascular system.

• Examples of ecosystem resilience in salt marshes versus vulnerability in mangrove forests.

Ecosystem Disturbances and Resiliency

• Different ecosystems respond variably to disturbances; clonal plants, like seagrasses, can spread to fill loss, while mangroves are less resilient to damage.

• Recognition of different characteristics affecting recovery and health of ecosystems.

Models of Ecological Interaction

• Importance of models for describing interactions and making predictions regarding disturbances and responses in ecosystems.

• Discussion of trophic cascades—how changes at one trophic level affect others both up and down the food chain.

Trophic Cascades in Kelp Forests

• Role of top predators (e.g., sea otters) in maintaining healthy kelp forests by controlling herbivore populations (e.g., sea urchins).

• Impacts of overfishing and ecological mismanagement leading to imbalances in predator-prey interactions.

• Defined concept:

  • Trophic cascade: changes in population at one trophic level affect populations at others.

Predation and Ecological Complexity

• Interaction between orca whales and sea otters:

  • Series of dietary shifts observed in orcas leading to increased predation on sea otters due to declines in other prey.

• Highlighting the complexity and interdependence within marine food webs.

Human Influence on Marine Ecosystems

• Discussion of human interactions, such as fishing, which complicate natural predator-prey dynamics through resource depletion.

• Emphasis on the necessity of holistic approaches in ecological research and conservation.