Pacific Rocky Intertidal Monitoring: Trends and Synthesis

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Coal Oil Point 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).

The anemone plots at Coal Oil Point consist primarily of the solitary anemone, Anthopleura sola rather than the colonial anemone Anthopleura elegantissima (note that these were considered a single species prior to the past several years and they are not distinguished in our sampling methods).  Cover of Anthopleura has undergone a gradual decline from around 25% in 1992 to less than 10% in 2010 with cover estimates interrupted every few seasons by periods of near complete sand burial.  Aside from sand, the dominant taxa occupying these plots are species of filamentous red algae which have been lumped with a few other seldom-encountered species into the "other red algae" category.  These algae, though fluctuating wildly in relation to sand burial, are also showing signs of decline since about 2006.  Alternatively, the ephemeral alga Ulva has been increasing over this period, along with bare rock. 

Mussel plots were added to this site in the fall of 2003.  Since that time, the mean cover of Mytilus declined initially from around 80% to around 60% by the fall of 2004, but has remained generally steady in the 60-70% range thereafter.  Much of the decline is the result of a single plot in which a mussel breakout gave way to an open patch of rock and barnacles that has persisted since that time. Annual motile invertebrate sampling has occurred in these plots since their inception (always in the spring, though with an additional sampling in the fall of 2003).  Limpets along with Nucella spp. and Tegula funebralis snails have undergone slight fluctuations during this time, until the dramatic increase in Tegula in 2010.  

The mean cover of Surfgrass (Phyllospadix) has fluctuated widely throughout the years at Coal Oil Point with seasonal variation (lower in spring, higher in fall) along with intermittent periods of sand burial.  Throughout the years, the cover of Phyllospadix hovered around the 60% to 80% range.  Dips below that level were the result of sand burial, rather than plant and/or rhizome loss.  Even where leaves were lost the plants would quickly regenerate from the rhizomes upon emergence from burial.  Beginning in 2003 the seasonal pattern began to break down and surfgrass cover increased steadily until 2005.  Seasonal variation returned in 2006, but then in 2007 the surfgrass population crashed in the absence of sand burial, and this time there was extensive rhizome loss as well.  Mean surfgrass cover declined to almost zero by the spring of 2008 and has recovered only slightly since that time.   Filamentous red algae and bare rock have increased in the wake of the surfgrass declines.  As of 2010 Phyllospadix cover was close to 20% and in subsequent sampling events, some suggestion of rhizome recovery has been observed at this site. 

The numbers of seastars at Coal Oil Point have never been high enough to warrant plot establishment.  However, in the spring of 2010, the decision was made to initiate 30 minute timed searches for seastars at this site.  In that sampling season a total of 8 seastars were counted and measured.

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 show all 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. For motile invertebrate size trend graphs by site, please use the Interactive Map.

Anthopleura (Anemones)

Coal Oil Point Anthopleura trend plot

 Mytilus (California Mussel) - percent cover

Coal Oil Point Mytilus trend plot

Mytilus (California Mussel) - motile invertebrate counts

Coal Oil Point Mytilus 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 show all 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)

Coal Oil Point 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. The sum of all individuals across all plots is displayed.

 Pisaster (Ochre Star) - counts

Coal Oil Point Pisaster trend plot

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Interactive Map

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