2. Streams (Rivers) Stream = water flowing downhill in a defined channel. Amount of flow significant. Usually varies seasonally. (wet season & dry season) Substrate important. (bedrock, gravel, silt) Amount of floating particles (turbidity) is important. What physical conditions do flow, substrate, & turbidity affect?

5. Energy in Streams Photosynthesis can occur in stream via periphyon (attached “algae”) or macrophytes (larger multicellular photosynthesizers). What conditions need to occur for photosynthesis to happen in stream? Most streams heavily dependent on external organic matter inputs (leaf litter) to support their food webs.

6. N. Amer. vs. S. Amer. Streams How do temperature and sunlight vary between temperate N. America and tropical S. America? How does precipitation vary between temperate N. America and tropical S. America? How do leaf litter inputs vary between temperate N. America and tropical S. America?

7. N. Amer. Stream Food Web periphyton grazing insects & crustaceans grazing fishes bacteria & fungi fine organic matter collecting insects, crust., nematodes, & annelids leaf litter predatory insects & crustaceans dissolved organic compounds runoff or groundwater entry coarse organic matter bacteria & fungi conditioning (microbial colonization) shredding insects & crustaceans “predatory” fishes

8. S. Amer. Stream Food Web periphyton grazing FISHES & crustaceans bacteria & fungi fine organic matter detritivore FISHES, crust., nematodes, & annelids leaf litter dissolved organic compounds runoff or groundwater entry coarse organic matter bacteria & fungi conditioning (microbial colonization) herbivore FISHES & crustaceans “predatory” FISHES Relatively few aquatic insects.

9. ? Aquatic Insect O-rama @ lower trophic levels Fish O-rama @ lower trophic levels

13. Estuaries Estuary = semi-enclosed body of water where freshwater from land drainage dilutes sea water. Amount of stream flow again significant. Usually varies seasonally. (wet season & dry season) Tidal and wave activity also significant. Salinity varies. Much organic matter deposited (mud).

15. Sea Grass Beds Seagrasses live completely submerged and can tolerate fully marine water. Require a soft particulate substrate and low turbidity.

16. Coral Reefs Reef = a solid outcrop in shallow water reached by sunlight. Coral Reef = a solid outcrop created by the action of coral animals in shallow water reached by sunlight. Coral reefs require shallow, 23-25 º C, clear water (low in nitrogen). Very sensitive to perturbation and stress.

17. Coral Animals

19. flat back reef reef face Fringing Coral Reefs

21. Acropora palifera Forms

22. Coral Bleaching

23. Coral Reef Food Webs Primary producers = algae in corals, periphyton (algae), and macrophytic algae. External inputs = plankton from open water (usually very important) Trophic patterns very complicated. Cleaner fishes. Coral eaters (parrot fishes).