Bacteria are one group of organisms that are truly everywhere. There is even a type of photosynthetic bacteria ("cyanobacteria") that grows in snow at the south pole in Antarctica! Your question is a good one, though, because in addition to the bacteria that naturally live in fresh water systems, Santa Barbara creeks tend to pick up a lot of contaminant bacteria from human and animal waste ("poop"). This waste is either put there by people living near the creeks (the homeless are blamed a lot for this), by campers or by people who use the creeks for fun (hiking, swimming). I've seen baby diapers floating in the water at Red Rock, and there are tons of dogs on the hiking trails. Human and animal waste has a lot of bacteria in it, and these bacteria grow well in fresh water streams with nutrient contamination (nitrogen and phosphorus from fertilizer, for example).Two kinds of bacteria from human waste include fecal coliform and Escheresha coli (often just called E. coli). This bacteria gets washed into the ocean during storms, and is the main reason why the beaches are closed in winter in Santa Barbara, and why surfers get sick if they go surfing during or immediately after storms.

It is important to keep in mind, though, that many bacteria live in the creeks naturally. In the ocean, there are over a million bacteria cells in one drop of water (and ten times as many viruses!). These bacteria and viruses are important to the health of the ecosystem (they break down dead organic matter and recycle nutrients, for example) and are in no way a health threat to humans. In addition to bacteria and viruses, there are many protozoa (tiny single-celled animals) that live in fresh and marine waters. Most are harmless but a few (giardia, cryptosporidium) can cause serious illness.