Oil? Spills? and Crabs? Oh my!

Sarah, Anika, and Marco
Bishop O’Dowd High School

How did the 2007 oil spill in the San Francisco bay affect the population of sand crabs in the area? This question is important because sand crabs are significant to beach ecosystems; they are food for many animals, and they are also an indicator species. This means that scientists and researchers can look at sand crabs to determine the health and sustainability of beaches and other marine ecosystems.

Source: https://nrm.dfg.ca.gov

Source: https://nrm.dfg.ca.gov

Sandy beach organisms such as sand crabs are highly affected by oil spills. Oil is detrimental to sand crabs because it can be toxic, clog the delicate organisms’ bodily systems, reduce oxygen in the sand, and reduce water flow to the beach. An ecosystem’s recovery from an oil spill is a timely process. Within the first year, the bacterial population will increase back to what it was prior to the spill, but, depending on the amount of oil and environmental conditions at the time, it can take the ecosystem about 6 years to make a complete recovery.

The data that we collected showed that the population of crabs was already at a low number before the oil spill occurred. In fall of 2005 the average number of crabs per core was 0.38. At the time overlapping the oil spill, fall 2007, the average number of crabs per core was 0.24. Another interesting component of our data was that in spring of 2008, fall of 2008, and spring of 2009 the average number of crabs per core was lower that the average during the oil spill. There could have been a lag between the oil spill and its effect on sand crab populations.

In conclusion, it is unclear whether the oil spill affected the sand crabs. However we hypothesize that the cleanup efforts allowed for the sand crab population to increase in 2010. The oil spill had negligible effects in 2007 and 2008, 3 years after the spill in the spring and summer of 2010, there was an incredible increase in sand crabs on Ocean Beach.

3 thoughts on “Oil? Spills? and Crabs? Oh my!

  1. Great topic choice! The effect of oil spills is definitely a very important aspect of environmental research, as they are unfortunately all to common and can utterly destroy ecosystems. The oil being toxic and clogging the bodies of sand crabs is understandable, but I didn’t realize that oil can actually lower oxygen content in sand; how awful! Overall, this blog is very thorough with some valuable research-the recovery of San Franciscan beaches from the oil spill and the effects on sand crabs, an indicator species, could serve as models for how other similar areas may be effected if oil spills were to occur.

  2. Great choice for your topic. Your information was very clear and it was very easy to follow and it taught me a lot about the consequences that come with oil spills to beach organisms. Also, I like how your information linked directly to your graph at the end.

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