Bob Creek Long-Term trends | MARINe

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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).

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 6th 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, with high cover in 2011, 2012, and 2013. 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%, before stabilizing at about 40% over the past several years. 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 high in Mytilus plots in all years except 2003-2005 when a dip occurred, followed by recovery. 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.

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, and it is likely that we will see further decline due to Sea Star Wasting Syndrome when the site is resampled in 2015. Occasional pulses in the number of juvenile ochre stars have occurred at Bob Creek, the most recent of which was in 2014. It is our hope that these juveniles survive and help to replenish the depressed sea star population.

Photo Plots

Long-Term methods Photo Plot thumbnail

Below are the trends observed for each Photo Plot target species at this site. Long-Term percent cover trend graphs also include any species that reached a minimum of 25% cover during any single point in time within a given target species assemblage. Breaks in trend lines represent missed sampling events. For additional species observed that did not meet this 25% threshold, please use the Interactive Map.

For motile invertebrate Species Counts, a mean across all plots was calculated, and only those species with a value of at least 5 individuals for at least one sample are shown. Due to time constraints, motile invertebrate counts have not been done at most sites since 2012. For motile invertebrate size trend graphs by site, please use the Interactive Map.

Chthamalus/Balanus (Acorn Barnacles) - percent cover

Bob Creek barnacle trend plot

Chthamalus/Balanus (Acorn Barnacles) - motile invertebrate counts

Bob Creek barnacle trend plot

Semibalanus (Thatched Barnacle) - percent cover

Bob Creek semibalanus trend plot

Semibalanus (Thatched Barnacle) - motile invertebrate counts

Bob Creek semibalanus trend plot

Mytilus (California Mussel) - percent cover

Bob Creek Mytilus trend plot

Mytilus (California Mussel) - motile invertebrate counts

Bob Creek Mytilus trend plot

Fucus (Northern Rockweed) - percent cover

Bob Creek Fucus trend plot

Fucus (Northern Rockweed) - motile invertebrate counts

Bob Creek Fucus trend plot

Pelvetiopsis (Dwarf Rockweed) - percent cover

Bob Creek Pelvetiopsis trend plot

Pelvetiopsis (Dwarf Rockweed) - motile invertebrate counts

Bob Creek Pelvetiopsis trend plot

Endocladia (Turfweed) - percent cover

Bob Creek Endocladia trend plot

Endocladia (Turfweed) - motile invertebrate counts

Bob Creek Endocladia trend plot

Transects

Long-Term methods Transects thumbnail

Below are the trends observed for each Transect target species at this site. Long-Term trend graphs also include any species that reached a minimum of 25% cover during any single point in time within a given target species assemblage. Breaks in trend lines represent missed sampling events.

Phyllospadix (Surfgrass)

Bob Creek surfgrass trend plot

Species Counts and Sizes

Long-Term methods Counts thumbnail

Species Counts and Sizes (where recorded) for Pisaster are shown below for this site. At some sites, other sea star species and Katharina are counted in addition to Pisaster. The sum of all individuals across all plots is displayed. Note that data gaps are represented by breaks in long-term count trend lines, but are not shown in size plots.

Pisaster (Ochre Star) - counts

Bob Creek Pisaster trend plot

Pisaster (Ochre Star) - sizes

Bob Creek Pisaster size plot

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