Pacific Rocky Intertidal Monitoring: Trends and Synthesis

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Navy North 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 Navy North has been monitored largely through volunteer efforts; field data have been collected, but not scored nor entered into database.

Tetraclita plots at Navy North consist primarily of pink barnacles (Tetraclita), but also contain acorn barnacles (Chthamalus dalli/fissus), as well as other red algae, other brown algae, and rock. Tetraclita varied over time from a range of ~20-60% cover, with highest abundances during/after the 1999-2000 La Niña (Chthamalus abundances peaked a year earlier). There was a tendency for Tetraclita to be more common in spring compared to fall.

Pollicipes cover in Pollicipes plots gradually declined from ~20% cover in the 1990’s to near zero by 2003 and thereafter. Rock dominated the plots, varying inversely with crustose corallines in abundance.

Mytilus covered ~20-40% in mussel plots from 1995-2001, after which it declined gradually to near zero after 2004. Bare rock, the only other dominant in the plots, increased coverage as mussels declined. Mussels were once common along Point Loma shores, but became increasing rare or absent after the 1970’s, apparently due to lack of successful recruitment. Now even the remnant mussel patches at Navy North that were initially chosen for monitoring have largely disappeared.

Silvetia cover in Silvetia plots, initially ~80% cover in 1995, lost about half of its cover during the 1997-1998 El Niño, then recovered by 2002 and remained at high levels thereafter. Other red algae abundance varied inversely with Silvetia, with articulated corallines making up most of the rest of the plot cover. There was a tendency for Silvetia to be more common in fall compared to spring seasons. Often in spring surveys, some rockweed appeared thinned out, tattered, and bleached. These conditions apparently were associated with storm damage coupled with aerial exposure to midday low tides during winter months.

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, other green algae, and articulated corallines. These components fluctuated considerably during 2002-2005; however, their combined values continued the >90% turf cover that existed throughout the monitoring period.

Surfgrass (Phyllospadix) remained at ~90% or higher cover throughout the monitoring period. There was a tendency for Phyllospadix to be more common in fall compared to spring seasons. Typical in spring surveys, portions of the surfgrass habitat appeared thinned out, tattered, and bleached. These conditions apparently were associated with storm damage coupled with aerial exposure to midday low tides during winter months.

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.

Tetraclita (Pink Barnacle)

Navy North Tetraclita trend plot

Pollicipes (Goose Barnacle)

Navy North Pollicipes trend plot

Mytilus (California Mussel)

Navy North Mytilus trend plot

Silvetia (Golden Rockweed)

Navy North Silvetia 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

Navy North red algal turf trend plot

Phyllospadix (Surfgrass)

Navy North 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)

Plots were sampled regularly at this site, but no Pisaster were observed.

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Interactive Map

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