Pacific Rocky Intertidal Monitoring: Trends and Synthesis

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Slide Ranch 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).

Chthamalus/Balanus percent cover in barnacle plots at Slide Ranch remained consistently high (>73%) during the survey period with the exception of a dip to 55% in 2009 when Porphyra occupied 21% of the substrate.  Bare rock consistently accounted for around 20% of the cover in each year. The diversity of invertebrate taxa was low in barnacle plots with only limpets and Littorina spp. occurring in appreciable numbers.  Littorina abundances ranged from 1385 to 4867 per plot.  Counts were an order of magnitude greater than those observed at nearby sites Santa Maria Creek and Bolinas Point.  Limpet counts in barnacle plots showed no striking temporal trends with counts ranging between 24 and 80 individuals per plot.

Mytilus californianus cover in mussel plots was high with a gradually increasing monotonic trend from 92% (2006) to 95% (2010).  This pattern of continuously high mussel cover is similar to the trends observed at Santa Maria Creek and Bolinas Point which are nearby Long-Term Monitoring sites also located in the Gulf of the Farallones.  This stretch of coastline is afforded some protection from strong winter northwest swells by the Point Reyes Peninsula.  This protection may contribute to the lasting integrity of the mussel beds. The numerically dominant motile invertebrates observed in mussel plots were limpets, Littorina spp. and Nucella spp.  Limpet and Littorina abundances were both higher at Slide Ranch than they were at either Santa Maria Creek or Bolinas Point.  Limpet abundance was very high (686 limpets per plot) in 2006 then dropped to nearly half that number (375) in 2007 and subsequently remained fairly constant for the remaining three years.  Littorina abundance mirrored the pattern observed for limpets with high abundance in 2006 (187 per plot) then dropping to 83 in 2007 with an even steeper drop to 20 in 2008.  Counts rebounded somewhat in 2009 and 2010.

Endocladia cover in Endocladia plots at Slide Ranch dropped considerably from a high of 52% cover in 2006 to a low of 15% in 2008 with a slight recovery to 38% in 2009.  Barnacle cover was the reciprocal of Endocladia with high Chthamalus/Balanus percent cover when Endocladia was low and vice versa.  Bare rock was the most common cover type when Endocladia or barnacles were not present for all years except 2006 when Mastocarpus spp. occupied 10% of the substrate and rock was just 6%. The numerically dominant motile Invertebrates observed in Endocladia plots were limpets, Littorina spp. and Nucella spp.  Littorina abundance was considerably higher at this site than Santa Maria Creek and Bolinas Point.  Counts of Littorina increased fourfold between 2006 (822 per plot) and 2010 (3240 per plot).  Limpet abundance showed an opposite trend from Littorina with sawtooth abundance fluctuations trending from 368 per plot in 2006 to 158 in 2010.  Nucella spp. counts were highest in 2006 and 2007 exhibiting an abundance trend similar to that shown by Nucella in Pelvetiopsis plots.

Surfgrass (Phyllospadix) cover at Slide Ranch was reasonably stable with a slight decline from 75% in 2006 to 56% in 2010.

Pisaster (Ochre Star) numbers were reasonably steady from 2006 through 2009 with a large drop in 2010.  No significant shifts in Seastar sizes were obvious with a modal size of around 100mm in each year.  Since few small seastars were observed, the high numbers could not be explained as recruitment events as was observed at Santa Maria Creek. 

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.

Chthamalus/Balanus (Acorn Barnacles) - percent cover

Slide Ranch barnacle trend plot

Chthamalus/Balanus (Acorn Barnacles) - motile invertebrate counts

Slide Ranch barnacle trend plot

Mytilus (California Mussel) - percent cover

Slide Ranch Mytilus trend plot

Mytilus (California Mussel) - motile invertebrate counts

Slide Ranch Mytilus trend plot

Pelvetiopsis (Dwarf Rockweed) - percent cover

Slide Ranch Pelvetiopsis trend plot

Pelvetiopsis (Dwarf Rockweed) - motile invertebrate counts

Slide Ranch Pelvetiopsis trend plot

Endocladia (Turfweed) - percent cover

Slide Ranch Endocladia trend plot

Endocladia (Turfweed) - motile invertebrate counts

Slide Ranch 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 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)

Slide Ranch 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 ochraceus (Ochre Star) - counts

Slide Ranch Pisaster trend plot

Pisaster ochraceus (Ochre Star) - sizes

Slide Ranch Pisaster size plot

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Interactive Map

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