Point Sierra Nevada Long-Term trends

Long-Term Monitoring Trend Graphs

Barnacle plots at Point Sierra Nevada consist almost exclusively of Chthamalus dalli/fissus, although Balanus glandula are recorded on rare occasion (note that species were not distinguished until 2001). Cover of Chthamalus spp. varied inversely with rock cover nearly perfectly, with little else occurring in these plots. Mytilus cover in mussel plots remained high and extremely stable at Point Sierra Nevada, hovering just above 80% for nearly the entire 30-year monitoring period. Rock and the goose neck barnacle, Pollicipes generally made up the remainder of cover within the plots.  

Hesperophycus cover within its target plots started out high and then declined precipitously. Gradual recovery occurred between 2004-2013, but in 2014 Hesperophycus appeared to be sunburned or heat-stressed and in many cases only the stipes remained. Cover of the rockweed has since remained low. Another species of rockweed, Silvetia, has also declined over time in plots where it is targeted at Point Sierra Nevada. In some plots, Mytilus, Hesperophycus, Endocladia, or Mastocarpus has moved in, but a fair amount of bare rock remains.  

In Mastocarpus plots, cover of the red alga is highly seasonal, with higher cover in fall than in spring. The way in which hydrodynamic forces affect intertidal plants may help to explain seasonal variation in size of Mastocarpus populations.  When water velocities are low, such as during the summer months in central California, hydrodynamic forces do not limit thallus size (Carrington 1990).  However, as water velocity increases, larger plants are torn out.  Small plants may be able to better withstand large hydrodynamic forces associated with winter swell.  Indeed, our plots generally contain smaller plants (and hence lower cover) in the spring. In 2016, monitoring frequency was reduced to a single annual survey each fall; hence the seasonal cycle is no longer captured by our data. 

Mean cover of Mazzaella was relatively constant over time within plots where it is targeted, although some seasonal variation was apparent (commonly higher in fall than spring). Reductions in Mazzaella cover were often associated with increases in cover of articulated corallines, suggesting that coralline algae persisted as a stable understory below Mazzaella, and reduced canopy cover of Mazzaella simply exposed more corallines. As with Mastocarpus, larger blades of Mazzaella tend to be ripped out during winter storms, leaving a perennial basal crust behind. In early spring, our plots tended to have mostly small plants that had just begun to grow back. Beginning in 2016, mussels began to settle in the plots and steadily increased in cover. This pattern is consistent with a trend observed at other sites, where ochre star decline due to sea star wasting has enabled mussel expansion into areas where they previously would have been consumed. Field sampling of Mazzaella plots ended in 2015 due to funding constraints, but plots are still photographed and scored in the lab for a reduced set of species. 

Surfgrass (Phyllospadix) cover hovered at around 80% along the transects where this species is targeted. Mean cover exhibited slight seasonal variation, with lower cover in the spring following winter storms that ripped out plants and abraded leaves. 

Counts for the ochre star, Pisaster ochraceus, in the sea star plots at Point Sierra Nevada varied substantially over time. In 2014, sea star numbers plummeted due to wasting syndrome. Very few juvenile stars have been observed, suggesting low recruitment levels and long recovery time. Point Sierra Nevada is the southernmost site at which we find the katy chiton, Katharina tunicata, in our sea star plots, albeit at very low numbers. 

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).

If you experience any barriers accessing the trend graphs below, please contact (pacificr@ucsc.edu) for help.

Photo Plots

Chthamalus/Balanus (Acorn Barnacles) – percent cover

Chthamalus/Balanus (Acorn Barnacles) – motile invertebrate counts

Mytilus (California Mussel) – percent cover

Mytilus (California Mussel) – motile invertebrate counts

Silvetia (Golden Rockweed) – percent cover

Hesperophycus (Olive Rockweed) – percent cover

Hesperophycus (Olive Rockweed) – motile invertebrate counts

Silvetia (Golden Rockweed) – percent cover

Silvetia (Golden Rockweed) – motile invertebrate counts

Mastocarpus (Turkish Washcloth) – percent cover

Mazzaella (Iridescent Weed) – percent cover

Transects

Phyllospadix (Surfgrass)

Species Counts and Sizes

Pisaster ochraceus (Ochre Star) – counts

Pisaster ochraceus (Ochre Star) – sizes