Marine Biology Study Guide

Intertidal Ecosystems

  • Rocky Intertidal Areas

    • Highly productive due to the nutrient exchange with the water column.
    • Organisms rely on the water column for feeding and nutrient acquisition.

  • Environmental Challenges

    • Waves crashing create a need for organisms to grip onto rocks.

Types of Organisms

  • Seaweeds (Macroalgae)

    • Three Main Types:
    • Green Seaweeds
    • Red Seaweeds
    • Brown Seaweeds
    • Seaweeds strongly attach to rocks using their holdfasts.

  • Rock-Dwelling Animals

    • Example species include barnacles and rhizoans.
    • These organisms spend their entire adult life on the rock, colonizing as larvae from the water column.

Important Experiments in Marine Biology

  • Hydrocondylate Experiment

    • Conducted to understand ecological distribution patterns.
    • Focused on the distribution of large vs. small particles on rocks.
    • Key Finding: Movement of barnacles up and down the rock resulted in significant mortality due to desiccation stress.

  • Competition Among Barnacles

    • Smaller barnacles thrive initially when moved lower but are ultimately outcompeted by larger barnacles.
    • Ecological trade-off highlighted: competition versus environmental resilience.

Herbivorous Organisms

  • Mollusks

    • Key Species: Snails, Limpets, Chitons.
    • Struggle for space due to competition with mussels.

  • Bob Payne's Starfish Experiment

    • Removal of starfish allowed mussels to dominate, leading to decreased biodiversity.

Evolutionary Insights

  • Seaweeds evolved on land before returning to marine environments—saltwater environments present physiological stresses for these organisms.

Food Chain Dynamics

  • Majority of biomass is converted into detritus after death, forming the basis of the food chain.

Coastal Habitats: Salt Marshes and Mangroves

  • Distribution and Stressors

    • Salt marsh plants submerge more during tidal cycles, creating a stressful habitat lower on the intertidal.
    • Superior competitors exist higher on the rocks.

  • Coastal Development Impact

    • Coastal development threatens salt marshes, leading to loss of biodiversity.
    • Salt marsh plants drown when sediments rise and they cannot emerge.

Seagrass Meadows

  • Provide limited hiding spaces for juvenile fish due to constant predation.

Kelp Forest Ecosystems

  • Kelp forests create structural habitats in hard bottom areas, distinct from coral reefs.
  • Important Species: Sea otters—maintain kelp forest balance by preying on herbivores such as sea urchins.

Trophic Cascades

  • Removal of top predators dramatically affects ecosystem dynamics, leading to algal overgrowth and reduced biodiversity.

Coral Reefs

  • Coral requires clear, warm water and forms beneficial associations with zooxanthellae (dinoflagellates).

  • Corals provide suitable habitats through various structural adaptations that compete for sunlight.

  • Damage and Recovery

    • Coral reefs can become damaged due to factors like increased water temperature and sediment covering.
    • Erosion affects reef growth and recovery, with visible impacts from parrotfish eating algae and creating scrape marks on coral skeletons.

Interactions and Community Structure

  • Relationships among species in coral reefs include mutualism (cleaning fish vs. bigger fish).

Environmental Threats

  • Climate change affects coral health, leading to widespread bleaching events and degradation of reef ecosystems.

Sediment Dynamics

  • Importance of sediment habitats, often overlooked, as they support various life forms through detrital feeding.

Examples of Biological Interactions

  • Distinction between planktonic life stages and adult forms described.
  • Insights into predatory relationships using gut contents, though limited by practical issues with data collection.

Trophic Levels and Food Web Structure

  • Overview of trophic levels in aquatic ecosystems, highlighting predation dynamics.

Deep Sea Ecosystems

  • Contrast between sediment environments (high diversity but low biomass) and hydrothermal vent systems (low diversity but high productivity due to chemosynthesis).

  • Evolutionary Adaptations

    • Organisms in sediment must manage stable conditions while those in vent systems rely on ephemeral habitats.

Conclusion

  • Summary of marine ecosystems highlights the critical roles of competition, predation, and environmental stress on community dynamics.
  • Next session will shift focus toward different marine ecological topics.