Occulto Long-Term trends | MARINe

Occulto 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). Due to funding constraints, semi-annual sampling of plots/transects was reduced to annual sampling beginning in 2016. In addition, counts of motile invertebrates within plots at most sites ended in 2014.

Barnacles (a mixture of Chthamalus fissus/dalli and Balanus glandula) within plots at Occulto declined substantially during the first few years of monitoring. An uptick in cover occurred between 2007-2014, but a decline in recent years (2014-2019) has resulted in low barnacle cover ranging between 7-25%. While bare space was still present in the plots, much of it has become occupied by mussels and several algal species, including Endocladia, Silvetia and Cladophora. Barnacles recruiting into this site tended to settle above the barnacle plots, in an area that is at a higher tidal elevation than barnacles were commonly found when monitoring began at Occulto nearly 30 years ago. Thus, although barnacles in the plots have declined substantially, they are still common at the site overall. Limpets and littorines were common in these high intertidal plots, and a few Nucella spp. were found amongst the mussels.

Mytilus cover within the mussel plots at Occulto has, on average, remained high over time. Storm-associated wave disturbance has removed mussels on occasion, and available space was temporarily colonized by other species, including Mazzaella, Phragmatopoma, and articulated corallines. However, mussels have always recovered. Limpets are the most abundant motile invertebrate counted in the mussel plots, but other species such as the whelk, Nucella spp. (mostly N. emarginata/ostrina), and the chiton, Nuttallina spp., were also commonly found.

Mytilus steadily recruited into the Endocladia plots, reaching an all-time high of 55% in 2008. Mussel cover has since gradually declined, replaced in part by barnacles and Mastocarpus.. Presence of Mytilus does not necessarily exclude Endocladia, as the alga can grow on top of mussels. However, in recent years, Endocladia has declined site-wide and is now considered to be “present”, but by no means “common to abundant” as previously described. The Endocladia plots are now primarily composed of bare rock and Mytilus.  Limpets and littorines were the most common motile invertebrate found in the Endocladia plots, with a few Nucella present within mussel patches.

Pisaster counts at Occulto were highly variable, largely because they are influenced by sampling conditions, as much of the plot consists of steep reef edges that can be difficult to sample when the swell is large. However, as with other sites in Santa Barbara County, ochre stars declined substantially with the arrival of sea star wasting syndrome. Sea star size typically spanned the entire range with both juvenile and large individuals  present, but the apparent lack of new recruitment to the site over the past 5 years suggests that recovery will be slow. The sea star plot could not be sampled in fall 2015 and fall 2016. In fall 2017, 2018 and 2019 the plot had to be sampled from above due to poor sampling conditions, so it is possible that sea stars normally counted from below by climbing into the channel surrounding the reef could have been missed. However, despite these constraints, sea stars at Occulto are nowhere near as abundant as they were prior to sea star wasting syndrome.

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

Occulto barnacle trend plot

Chthamalus/Balanus (Acorn Barnacles) - motile invertebrate counts

Occulto barnacle trend plot

Mytilus (California Mussel) - percent cover

Occulto Mytilus trend plot

Mytilus (California Mussel) - motile invertebrate counts

Occulto Mytilus trend plot

Endocladia (Turfweed) - percent cover

Occulto Endocladia trend plot

Endocladia (Turfweed) - motile invertebrate counts

Occulto Endocladia 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 (Ochre Star) - counts

Occulto Pisaster trend plot

Pisaster (Ochre Star) - sizes

Occulto Pisaster size plot