Crystal Cove Long-Term trends | MARINe home

Crystal Cove 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).

From 1996-2006, average barnacle cover at Crystal Cove was generally high (50 to 80% cover) although abundance of barnacles fluctuated among sampling periods.  For most plots, the majority of the area not covered by barnacles was simply bare (recorded as bare rock) aside from the occasional and short-lived appearance of small patches of algae such as the ephemeral sea lettuce Ulva and the red turf Caulacanthus.  Mussels (Mytilus spp.) occasionally recruited into barnacle plots, but mussel abundance in these plots  was generally low (less than 20% cover on average) and occurred mostly in a single plot.   In 2006, barnacle cover dropped sharply across all plots, resulting in an increase in recorded coverage of bare rock.  Since this drop, barnacle cover has increased slightly but remains variable.  Barnacle plots have consistently contained extremely high numbers of limpets and periwinkles (Littorina spp.).  Generally, higher numbers of Littorina are recorded in fall than in spring sampling periods.

From 1996 to 2006, mussel cover in Crystal Cove mussel plots remained relatively high (above 60%) with the notable exception of a large drop in cover associated with the 1997-1998 El Niño. During the El Niño, several different species moved in to fill the space opened up by this decline in mussel cover, including the annelid Phragmatopoma, the ephemeral alga Ulva, and articulated coralline algae; yet cover of these species declined over the next two years as mussels recovered to original cover levels. Following this recovery, mussel cover remained relatively high until 2007 when a moderate decline was observed following a storm with extraordinarily large waves. The effect of the storm was variable in space: some plots lost only a small amount of mussel cover but one plot was completely denuded of all mussels.  Bare space created by the 2007 storm was filled quickly by a variety of algae including articulated corallines and non-calcified red algae.  From 2007-2011 overall mussel cover varied between approximately 40 and 60% cover, and cover in individual plots was dynamic. In the plot most heavily affected by the storm, mussel cover has remained low in subsequent years of monitoring; and in other plots, minor disturbances have caused smaller occasional reductions in mussel cover. Mussel cover began to increase in late 2011, reaching an average of ~80% cover in 2012. In Spring 2013, following stormy weather, mussel abundances were low in two plots, causing the average abundance to dip below 50%; and this overall decline continued into Fall 2013 when no mussels were recorded in any of the plots (although mussels do occur in low abundances elsewhere at the site).  As with past drops in mussel cover, a variety of algae, including articulated corallines and non-coralline red algae (e.g  Centrocerus and Laurencia) increased in abundance following mussel decline.  Mobile animals in mussel plots consisted primarily of limpets in the genus Lottia, whose numbers were highly variable over time but have been low since Fall 2011.

Rockweeds show variation in cover within years with a pattern of higher cover in fall than in spring. Across years, there appeared to be a slight and slow decline in rockweed cover from 2004 – 2009, followed by a slight increase and relative stabilization with average cover exceeding 70% since Fall 2010. Space created by the reduction in Silvetia cover was filled by a variety of species including mussels and the red turf alga Caulacanthus, though in general these other species did not persist long in Silvetia plots. Several types of mobile invertebrates, including hermit crabs, chitons, and turban snails, were regularly found in low abundance in the rockweed plots.  Limpets (Lottia spp) were the most abundant group of mobile animals in these plots; although numbers varied greatly over time, limpet counts were typically at least five times higher than counts of any other taxon. 

Surfgrass (Phyllospadix) cover varied within years (with higher cover in fall than in spring) and among years.  Despite these temporal fluctuations, surfgrass cover remained generally high at this site (typically above 50% cover).   While the feather boa kelp Egregia was the only other species with a notable contribution to cover in surfgrass habitat, several species of red algae (e.g. Pterocladiella and Plocamium) have been consistently present in this zone in low abundance.  This habitat is also heavily influenced by sand movement:  sand cover typically fluctuated between 3 and 22 %. 

Sea star (Pisaster) counts at this site varied greatly over the sampling period. From 1997 to 2008, site-wide Pisaster counts were generally low (fewer than 50 individuals) with except for peaks in abundance in Fall 1999 and 2007. From 2008 to 2011, Pisaster counts were generally higher than in the previous decade, with more than 75 individuals per survey.   Site-wide seastar counts were extremely high in 2013, exceeding 175 individuals in Fall of that year, before plummeting to a total of 11 observed individuals in Spring 2014. Sea Star Wasting Syndrome, which was first observed at this site on November 4, 2013 (after the Fall 2013 survey), is a likely contributor to the sharp decline.  Pisaster were still present at low abundance at the site in Fall 2014. Sea star size measurements were initiated in Spring 2012. Most individuals fall in the 100 to 150 mm size class. Larger individuals  (>150 mm) were present in low numbers in 2012 but were less abundant towards the end of 2013.  

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

Crystal Cove barnacle trend plot

Chthamalus/Balanus (Acorn Barnacles) - motile invertebrate counts

Crystal Cove barnacle trend plot

Mytilus (California Mussel) - percent cover

Crystal Cove Mytilus trend plot

Mytilus (California Mussel) - motile invertebrate counts

Crystal Cove Mytilus trend plot

Silvetia (Golden Rockweed) - percent cover

Crystal Cove Silvetia trend plot

Silvetia (Golden Rockweed) - motile invertebrate counts

Crystal Cove Silvetia trend plot


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)

Crystal Cove 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 ochraceus (Ochre Star)

Crystal Cove Pisaster trend plot

Pisaster ochraceus (Ochre Star) - sizes

Crystal Cove Pisaster size plot

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