Burnt Hill 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, counts of motile invertebrates within plots at Oregon sites ended in 2012. At Burnt Hill, reduced funding also meant that sampling could not be done in 2017 and 2018.

Barnacles in the focal plots for this species group consisted of higher cover of Balanus glandula than Chthamalus fissus/dalli, but a mixture was present in all years. Mean barnacle cover fluctuated between about 35%-85%. In the years when barnacle cover was lower, cover of the rockweed, Pelvetiopsis, increased. Barnacles, both live and dead, provide an excellent substrate upon which Pelvetiopsis can settle, so it is possible that during the years of “low” barnacle cover, barnacles were simply hidden below the rockweed. In 2014 we began keeping track of multiple layers under each point (previously only the top layer was typically scored), which will enable us to know whether species “declines” are real, or simply a result of one species overlaying another. Counts of littorines and limpets were consistently high in barnacle plots at Burnt Hill, and the whelk, Nucella was present in low numbers.

Cover of mussels in Mytilus plots was consistently high until 2016, when it dropped to 51%. Sampling did not occur in 2017 or 2018, but mean mussel cover was back up to 73% by 2019.  Limpets, littorines and Nucella were all common in mussel plots.

Rockweed cover in Pelvetiopsis plots was high most years, but dipped below 50% in 2008-2010, and again in 2013-2014. These dips corresponded with increases in barnacle cover, and as described above, it is not clear whether these increases were real, or just a result of barnacles being exposed when epiphytic Pelvetiopsis cover declined. Limpets and littorines were consistently abundant in Pelvetioptis plots.

In general, Endocladia cover remained moderately high over time in the plots it is targeted in. Dips in cover were sometimes associated with an increase in Mastocarpus, but more often with increases in bare rock, suggesting that space is not a limited resource in these plots. Three groups of motile invertebrates, limpets, littorines and Nucella, were common in most years within Endocladia plots.

Phyllospadix transects are located within pools at Burnt Hill, which typically means that cover does not fluctuate as much as in areas where the surfgrass is exposed to air at low tide, and can become dry and bleached out during warm, mid-day low tide periods. Surfgrass cover was relatively stable, and while a few other species, such as Odonthalia, were commonly present along the transects, none exceeded 25% cover.

As with many sites, abundance of the sea star, Pisaster ochraceus, fluctuated substantially over time for this highly mobile animal. Surprisingly, ochre star numbers remained high in summer 2014, well after declines had occurred along much of the west coast due to Sea Star Wasting Syndrome, but a significant decline was documented in 2015. As of 2019, no significant recruitment pulse (as evidenced by low numbers of stars < 50 mm radius) had been observed, suggesting that recovery of ochre stars at Burnt Hill could be slow.