1. Communities, Ecosystems, and Biodiversity Definitions of community Organism interactions Ecosystems Different types of communities, ecosystems Biodiversity

2. Community Definitions All organisms in an area Also includes: interactions, structure, organization Can also include recurrence The biological component of ecology (interactions between an organism in an area plus the environment) Superorganism (Clements, 1926) vs. Individualistic responses (Gleason, 1929)

3. Organism Interactions Competition Food, space, nutrients, light Niche concept and guilds Dominance Organisms partition resources so don’t compete Dominant organisms

4. Organism Interactions Predation Hunting: chemosensory, visual predator avoidance Morphology, chemistry, behavior Predators and trophic pyramids

5. Organism Interactions Epibiosis relationships: mutualists, parasites, commensal Keystone species and “species of great effect”

6. Why study marine communities? Understand trophic web Recognize keystone species, species of great effect Conservation practices Fisheries impacts, sustainable harvesting Importance of previously unknown processes Microbial loop, primary productivity and iron Understand impact of pollutants

7. Example: Sea Grass Bed, TX Annually dynamic, but over time, averages out to similarity Dead versus live assemblage comparisons In current near estuary, fully marine

8. Example: Sea Grass Bed, TX Sea grass: baffles sediment: environment mediator, species of great effect environment mediator, species of great effect Clams, gastropods, polychaete worms, arthropods, others Larval settlement at different times of year per species Clams in spring Summer: many dead juvenile clam shells in sediment Seagrass, algae: primary producers Gastropods: grazers, predators Clams: detritovores Mussels and polychaetes: filter feed Arthropod and fish: predators Seagrass substrate for microbes, algae Microbial loop recycles nutrients

9. ECOSYSTEM Ecosystem = community + environment Scaless Environment = physical aspects Topography, sediment type, currents, light Often anthropogenic effects: pollutants, sediments Dynamic: always changing on fine temporal scales Over geologic time: slow and quick changes

10. Example: Hydrothermal Vents Deep ocean, near “black smokers” Very high T water, sulfur, other chemicals No light, low O2 Tube worms, bivalves, shrimp, crabs, eels Symbiotic relationship with sulfur-fixing bacteria Similar to photosynthesis, but some predation Nutrient input from smokers, detritus Organisms tightly coupled with environment Open or closed system? Patches far apart, smokers ltd time Organisms have to get there somehow!

11. Biodiversity Species richness: how many species Can be studied on community/ecosystem scale or globally Ocean extremely diverse Reefs more diverse than rainforest! Most of study of biodiversity through time marine Diversity greatest on continental shelves, coasts Light, nutrients --> primary productivity high Diversity in deep ocean also high Nutrients, O2 But…patchy

12. Extinctions Local extirpations --> global extinctions Small, background extinctions --> mass extinctions Background extinctions: local to regional; one or few species Causes of background extinction: Speciation, outcompete, invader, environment, disease

13. Mass Extinctions Involve MANY species, global 5 major mass extinctions: Largest: P/Tr, 250MYA – 80 to 95% marine life Most well known: K/T, 65MYA – 40% marine life

14. Mass Extinctions Causes of mass extinction: Climate change ocean circulation change Volcanism Extraterrestrial impact Sea-level change Human factors

15. A human-caused mass extinction?

16. Trophic changes