Lecture Notes: Importance of Community Interactions and Coral Reef Ecosystems

Key Topics Covered

• Community interactions and trophic interactions
• Keystone species vs. foundation species
• Coral reef ecosystems
• Threats to coral reefs and coral bleaching
• Importance of symbiotic relationships

Community and Trophic Interactions

• Community interactions refer to how species interact within an ecosystem.
• Trophic interactions describe the feeding relationships between species and their impacts on the ecosystem.

Keystone Species

• Keystone species have a disproportionate impact on their ecosystem relative to their abundance.
• Traditionally thought of as top predators, but in coral reefs, corals themselves can be keystone species.
• Coral reefs support up to 50% of ocean biodiversity but occupy less than 0.015% of ocean space.

Coral Reef Ecosystems

• Important for ocean biodiversity and heavily threatened.
• In 1970s, over 50% of coral reefs had live coral growth; by 2012, only 8% did.
• Support many marine species either directly or indirectly.

Threats to Coral Reefs

• Destructive fishing practices such as bottom trawling that damage coral structures.
• Direct collection and sale of coral by humans.
• Pollution, including ocean acidification, poses a significant threat.

Symbiotic Relationships: Coral and Zooxanthellae

• Coral reefs have a mutualistic relationship with zooxanthellae (microscopic algae).
• Zooxanthellae live inside corals, providing nutrients, and benefiting from coral protection.
• This relationship is crucial for coral health and survival.

Coral Bleaching

• Coral bleaching is the loss of color in corals due to the expulsion of zooxanthellae.
• Triggered by environmental stressors such as chemical changes in ocean water.
• Coral misinterprets chemical signals, leading to zooxanthellae expulsion and coral death.

Foundation Species

• Foundation species provide the structural basis for an ecosystem (e.g., coral, kelp, hemlock).
• Coral serves as both a keystone and foundation species in coral reef ecosystems.
• These species increase biodiversity by creating diverse habitats and niches.

Effects of Multiple Stressors

• Most environmental problems are due to multiple stressors, not just a single cause.
• Coral reefs face threats from pollution, overfishing, and direct human interference.

Comparing Ecosystems

• Sea otters as keystone species and kelp as foundation species in kelp forests.
• Corals serve as both keystone and foundation species, unlike other ecosystems.

Conclusion

Understanding the roles of keystone and foundation species is crucial for ecosystem conservation. Coral reefs, being key to ocean biodiversity, require urgent attention to mitigate multiple environmental stressors.