Pacific Rocky Intertidal Monitoring: Trends and Synthesis

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Cardiff Reef 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).

Since 2005/2006 Cardiff  has been monitored largely through volunteer efforts; field data have been collected, but not scored nor entered into database.

Chthamalus/Balanus plots (nearly all Chthamalus dalli/fissus) at Cardiff were subject to sand and gravel scour during storm events that led to highly variable abundance over time, ranging from ~10-80% cover. Barnacle cover dropped from initial values due to severe 1997-1998 El Niño storms, with plot cover changed to bare rock or ephemeral seaweeds Ulva and other brown algae. Barnacle cover gradually returned to initial monitoring levels by Fall 2001, went through a lesser decline after Spring 2002, then increased to highest abundances by 2005-2006. Throughout the monitoring period, bare rock cover was inversely correlated with barnacle cover, except for Spring 1999 when the ephemeral algae blooms coated the plots.

Pollicipes cover in Pollicipes plots varied from ~10-30% cover during the monitoring period, with generally less storm effects on abundances than acorn barnacles (above); however, one plot was completely destroyed by rock breakout that occurred after Fall 2001 sampling (a replacement plot was added in Spring 2002, so trend graph does not reflect the plot loss). Other plot cover included Mytilus, Chthamalus, and bare rock. Mytilus cover variations associated with the 1997-1998 El Niño and 1999-2000 La Niña were greater than those for Pollicipes.

Mytilus were monitored in two sets of mussel plots at Cardiff, representing inshore reef (smaller mussels) and offshore reef (larger mussels). The trend plot combines abundance data from both reefs. Mytilus cover fluctuated from ~55-85% cover during the monitoring period. Declines are evident associated with 1997-1998 El Niño storms, followed by recovery and stability until another decline/recovery cycle occurred in 2004-2006. Bare rock accounted for nearly all other cover in the plots. Unlike monitoring sites on Point Loma, mussels at Cardiff were common in their zone, with successful recruitment episodes evident over time.

Red algal turf was scored in red algal turf transects until 2001, after which it was scored as more detailed components, including other red algae, articulated corallines, and other brown algae. These components combined values continued the relatively high turf cover that existed throughout the monitoring period, except in Fall 2003 when sand covered ~60% of the transects. Surfgrass (Phyllospadix) comprised a relatively small portion of the red algal turf transects.

Surfgrass (Phyllospadix) cover varied considerably from ~15-95% during the monitoring period. Following a small decline during the 1997-1998 El Niño, abundance increased to highest levels by 1999-2000 La Niña, followed by variable declines to the lowest cover in 2005. Other red algae varied inversely with surfgrass, except in Spring 2004 and Spring 2005, when other brown algae was more common. There was a tendency for Phyllospadix to be more common in fall compared to spring seasons. Sometimes in spring surveys, portions of the surfgrass habitat appeared thinned out, tattered, and bleached. These conditions apparently were associated with storm damage and/or with aerial exposure to midday low tides during winter months.

Ochre seastars (Pisaster ochraceus) were rare or absent from Fall 1997 to Fall 1999, after which numbers increased to roughly 10-30 stars site-wide, except in Fall 2000 and Spring 2003 when poor sea conditions made searching low intertidal crevices difficult.  The wide range of star sizes found was not consistent with recruitment alone; it was likely that shallow subtidal seastars migrated into the low intertidal to forage on mussels and other mollusk prey. Southern California seastars experienced catastrophic declines associated with warm-water periods starting in the late 1970’s due to a bacterial “wasting” disease. Some recovery has been evident in recent years, as demonstrated by the increased numbers at Cardiff.

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.

Chthamalus/Balanus (Acorn Barnacles)

Cardiff Reef barnacle trend plot

Pollicipes (Goose Barnacle)

Cardiff Reef Pollicipes trend plot

Mytilus (California Mussel)

Cardiff Reef 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.

Red Algal Turf

Cardiff Reef red algal turf trend plot

Phyllospadix (Surfgrass)

Cardiff Reef 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

Cardiff Reef Pisaster trend plot

Pisaster (Ochre Star) - sizes

Cardiff Reef Pisaster size plot

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Interactive Map

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