I was wondering today about any possible environmental impacts that rain has on bacteria. It washes it off the land into rivers and streams and then the ocean. Any impact involved in washing away from the land? On rivers? On the ocean? On anything?
I was told in Brazil that it is safe to drink the water straight from the Amazon River, as long as you are not too close to an effluent from a town. Trying to google it, I get no reliable cites yea or nay, an dWiki’s Amazon article does not address the subject… If that is the case, there would be a natural cleansing taking place in a large movement and exchange of water.
I was thinking more in terms of being a necessary process of some kind where it helped the bacteria and whether or not it had an impact of any kind on oceans.
It dissolves all sorts of nutrients and washes both them and the bacteria themselves into the ocean. The ocean is full of dissolved minerals that were put there in part because of rain.
Also, the impact of rain helps oxygenate the surface layer of the ocean, both by mixing it with air and because it carried dissolved oxygen with it.
California beaches are regularly closed after the first rain of the season, because of all the stuff – lots and lots of dog excrement being high on the list – that washes down the storm drains to the sea.
I’m not really sure if this is what you were looking for: bacteria don’t exist without a sustaining medium. Dog poop is a very rich and ripe example.
People are instructed not to go swimming in their local swimming hole right after rain events because of bacteria. Cell densities increase temporarily because of run-off carrying human and animal waste. In places that have combined sewage systems (rainwater is collected and conveyed along with human/industrial sewage all in the same pipe), you can have overflows during heavy storm events–which means raw sewage gets discharged into waterways. Bacteria concentrations jump up dramatically during these events.
Bacteria are carried downstream, yes. But the bacteria that are of human health concern are associated with feces–especially mammalian feces. So in this way, being washed into a stream is not “helpful” for bacteria, since their food source is diluted. It isn’t real common that you’ll find high bacteria counts all the time in most waterbodies. The streams that have the highest bacteria counts on a continual basis tend to be those adjacent to livestock grazing land. Cows will often wade into these streams for cooling and drinking purposes and poop at the same time. And then there are are streams that contain residential straight pipes–which discharge untreated sewage directly from people’s toilets. The bacteria in these streams are “happy” because they have plenty of food. But in the absence of a poop source, fecal bacteria don’t do very well.
Fecal bacteria that make their way to the ocean tend to be of the salt-tolerant variety. Like Enterococcus. E.coli is the indicator fecal bacteria for freshwater systems.
There I was, out in the countryside, and found a lovely little brook. I bent and drank from it.
Then, upstream just a bit, I encountered a small herd of cattle, standing in the water, doing what cattle do.
Was lucky, didn’t get sick, never drank from a natural stream again.
A lot of rain is possibly caused by bacteria. There are in the range of500 billion tons of dry biomass of bacteria on (and over, and under) Earth. (There are around 105 million tons of human dry biomass, so that is more than 4,000 times the mass of all humans.)
I’m not sure if you are asking about bacteria washed off the land or nutrients washed off the land. The mass of bacteria washed off the land would be trivial compared to the amount already in the ocean. If you are talking about nutrients, then yes, they are very important to the ocean’s food web. And when there is a large amount of runoff, it can cause blooms by providing nutrients that were bottlenecks to growth.