Dana Point Long-Term trends | MARINe

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Dana Point 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).

Barnacle cover at Dana Point showed frequent small increases and decreases since initiation of sampling in 1996, with a trend of declining cover over time.  On a few occasions, small amounts of algae (including the rockweed Silvetia, the ephemeral sea lettuce Ulva, the brown blade Endarachne and the red turf Caulacanthus) recruited into barnacle plots, but these algae did not persist.  Instead, rock in barnacle plots that was not occupied by barnacles generally remained bare.  Snails in the genus Littorina were consistently found in very high abundance in barnacle plots.  Limpets (genus Lottia) were also consistently present but at much lower densities than Littorina

Mussel cover at Dana Point also fluctuated over time.  Mussel cover decreased during the 1997-1998 El Niño.  After recovering following the El Niño, mussel cover dropped again in spring 2007 following a storm with extraordinarily large waves.  As at other sites in the region (e.g. Crystal Cove) the effects of the storm were variable in space, with some plots losing more of their mussel cover than other plots.  In general, following a drop in mussel cover, space on the rock not covered by mussels remained bare except for occasional recruitment of barnacles (acorn barnacles and Tetraclita). Low and fluctuating cover of the red turf alga Caulacanthus has been observed on top of mussels in several plots since the early 2000s. After the 2007 storm, plots that lost large numbers of mussels were slow to recover, and on average mussel cover remained lower than 75% of plot area until abundances began to increase at the end of 2010. Following several seasons of high cover, mussel abundance started to decline again in Fall 2013, and in 2014 average cover across all plots again remained lower than 75% of plot area.   Several groups of molluscs are consistently found in low abundance in mussel plots (e.g. the chiton Nuttallina, the turban snail Tegula funebralis, and the periwinkle genus Littorina) but only limpets (genus Lottia) were found in very high abundance.

Rockweed cover at this site fluctuated within years (often with higher cover during fall sampling periods than spring sampling periods).  Small amounts of sand were occasionally observed in a few of the rockweed plots during fall sampling, but overall sand influence appeared to be low.  Across all years, mean rockweed cover remained relatively high (above 60% of plot area, on average).  When the cover of Silvetia dipped, the cover of bare rock typically increased: aside from the red turf alga Caulacanthus (which appeared at low levels in a few plots) and crustose algae, few other space-holding species were observed in rockweed plots.  Limpets (Lottia sp) were very abundant in Silvetia plots, although limpet abundances fluctuated greatly over time (from a high average of 100 individuals per plot to a low average of approximately 20 individuals per plot).  Littorina snails were somewhat common, while other taxa, such as chitons and  turban snails were also regularly found in rockweed plots in low numbers. 

Sea star (Pisaster) counts varied greatly over the sampling period, but were generally lower than numbers observed at other Orange County Sites (see Crystal Cove, Shaws Cove, and Treasure Island for comparisons).  From 1996 through 2002, the maximum number of Pisaster encountered in site-wide surveys at Dana Point was 10 individuals (in Fall 1999).  From 2003 – 2012, counts fluctuated from a low of 1 individual to a high of 30 individuals encountered per survey.  Measurements during this period (2004-2005 and 2012) indicated that most individuals fell into the 100 to 150 mm size class.  As with other Orange County sites, Pisaster numbers increased sharply in 2013, with a count of 70 individuals in fall of that year. Measurements in Spring and Fall 2013 show that most individuals fell in the 100 to 150 mm size class, but individuals as small as 50mm and as large as 190 mm were present at the site.  Consistent with other sites in the region, Pisaster counts dropped sharply following Fall 2013 surveys (no Pisaster were observed during surveys in Spring or Fall 2014).  Sea Star Wasting Syndrome, which was observed at multiple sites in this region after our Fall 2013 survey, is a likely contributor to the sharp decline. 

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

Dana Point barnacle trend plot

Chthamalus/Balanus (Acorn Barnacles) - motile invertebrate counts

Dana Point barnacle trend plot

Mytilus (California Mussel) - percent cover

Dana Point Mytilus trend plot

Mytilus (California Mussel) - motile invertebrate counts

Dana Point Mytilus trend plot

Silvetia (Golden Rockweed) - percent cover

Dana Point Silvetia trend plot

Silvetia (Golden Rockweed) - motile invertebrate counts

Dana Point Silvetia 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) - counts

Dana Point Pisaster trend plot

Pisaster ochraceus (Ochre Star) - sizes

Dana Point Pisaster size plot

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