Bob Creek Long-Term trends

See below for trend graphs

In order to standardize species resolution across all MARINe groups, and over time, some species (typically rare) were lumped for graphical presentation of Long-Term monitoring data. See lumped categories for definitions (some variation occurs between methods and over time). Due to funding constraints, counts of motile invertebrates within plots at Oregon sites ended in 2012.

Barnacle cover was generally high in the barnacle plots at Bob Creek, and consisted almost exclusively of Balanus glandula. Barnacle plots at this site are subjected to a high level of scour from sand movement, and plot 5 is often buried when we survey in the summer. Because of this, we added a 6^th barnacle plot in 2001 and excluded plot 5 from the trend graph summary data. Pelvetiopsis cover fluctuated substantially in 2 of the 5 barnacle plots. Cover of Semibalanus within its target plots was somewhat variable over time, beginning around 50%, then dropping to around 10% in 2004. A recruitment event in 2007 resulted in a spike in cover at around 70%, followed by a gradual decline. As of 2019, mean cover of Semibalanus was down to 14%, and mean mussel cover was at an all-time high of 32%. This fluctuation in cover of thatched barnacles was surprising given their ability to be quite long-lived (10-15 years; Morris, Abbott, and Haderlie, 1980). Mussel cover was generally high in Mytilus plots with the exception of a dip in 2003-2005 , and a more recent drop to around 65% cover between 2016-2019. Fucus cover in rockweed plots started out at nearly 100% but declined dramatically in 2002 and further in 2003. This decline was followed by a modest recovery in 2004/2005, but cover has since declined again and remained quite low. Barnacles were abundant in Fucus plots, but a fair amount of bare space was also present. Pelvetiopsis cover in its target plots fluctuated substantially over time, varying inversely with barnacle cover. Endocladia cover in turfweed plots began at just above 50%, but then declined and was generally quite low. Barnacles were commonly the most abundant taxa in these plots. Limpets and littorines were abundant in all photoplots. Nucella spp. were often quite numerous in Semibalanus plots, but were also present in Mytilus, Endocladia, and Pelvetiopsis plots.

Two of the surfgrass transects at Bob Creek had consistently high cover of Phyllospadix (nearly always close to 100%), but the third transect is located along the side of a surge channel and commonly contains significant cover of red algae such as Prionitis spp. Sampling of this third transect was discontinued in 2017, due to access difficulties.

Ochre star numbers were relatively stable at Bob Creek until 2014. The “jump” in numbers between 2003 and 2004 was due to the enlargement of one plot that had low numbers of stars. Numbers declined in 2014 due to Sea Star Wasting Syndrome but have since steadily increased to counts that far exceed the long-term mean. Although the population size is now at an all-time high at Bob Creek, the size structure has not yet recovered to a normal distribution. Small ochre stars (< 50mm radius) are much more abundant than larger individuals. However, if these smaller animals continue to grow and thrive, the population size structure should recover within a few years.