Finishing Fieldwork in the Intertidal

Last weekend I concluded my fieldwork for both Otter Rock and Cascade Head 2018 intertidal monitoring for ODFW. On Saturday we finished community mussel bed surveys that examined the intertidal community for potential changes from reduced populations of sea stars caused by wasting in 2014. For this we meet at Otter Rock at 5:20am while it was still pitch black outside. We proceeded to walk to the site in the dark using the light from a few headlamps and phones.

Heading to site at Otter Rock before dawn

For this survey we measured the height and depth of the mussel bed, abundance of mussel predators (sea stars and whelks), and counted mussel recruits. We count the whelks because they may take over the role of controlling the lower limit of the mussel bed. This is normally the role of sea stars (especially Pisaster ochraceus) but their populations are significantly reduced due to wasting.

Counting mussel recruits at Otter Rock 

Whelk: predator of mussels

On Sunday I woke up before sunrise again. At 5am I was on my way to Cascade Head to complete the last sea star wasting survey of 2018. And good news was that we saw very little wasting sea stars! Unfortunately though three of our transects that we sample were under water even with the -1.9 tide. In previous months and years there had been more sand that made the pools shallower allowing for ODFW to count sea stars in those areas but this year the sand was all washed away and we were not able to sample them. We were still able to survey around 200 sea stars during the belt transect and over 200 sea stars for the timed searches.

Timed search surveys at Cascade Head


Timed search survey at Cascade Head

Once I finished the fieldwork I had to enter my data and analyze it before the final presentations we gave on Friday. It lead to a couple of very busy days but I was able to finish everything. For those of you who were unable to come to the final presentations I will give a brief summary of what I found. The biggest conclusion was that sea stars are very healthy! Since 2015 when monitoring began the percentage of sea stars showing signs of wasting has deceased to very minimal levels (below 2%) at both sites by 2018. The other big conclusion I determined was that population of sea stars remained similar to 2015 over the four years based on densities. There was some fluctuation but it was not statistically significant at Cascade Head and for Otter Rock it was only one year having slightly higher densities but then it dropped back down the next year. There are two main possibilities to explain why we aren’t seeing an increase in densities over the four years. One is that by 2015 populations had already recovered from sea star wasting. The other explanation is that four years is not enough time to see recovery and it will take more years of monitoring to observe an increase in sea star density indicating that they have recovered.

For those of you who came to the final presentations, thank you for your support. And for those who are reading and were unable to come, I hope you enjoyed learning about my project and you can check out a picture of my poster below:

Presenting my poster


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