Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • BCO-DMO Processing Description
• Parameters
• Project Information
• Funding

ACE = Annual Colonization Experiment

Species interaction experiments called ACE, Annual Colonization Experiment includes six treatments to test the main and interactive effects of predation, competition and disturbance on annual colonization of rocky substrates in the mid-zone of the rocky intertidal along the Oregon Coast (see site list attached). The experiment began in 2011 and is repeated annually. All plots are 15 x 15cm and fixed,  and the experiment is repeated in the same location each year.  Each spring (usually April or May), all plots are cleared of all biomass using scrapers and oven cleaner to reset the community. The exception is the control plots  (CO) which were started in 2021 and are nearby plots that have never been intentionally disturbed.   There are 6 treatments that include 1) undisturbed controls of the climax community which is typically mussel-dominated, 2) marked plots that are cleared annually to capture annual prey colonization and serve as controls for the interaction experiments, 3) 2) partial cages that serve as cage controls for the interaction experiments 3) predator exclusion cages where an open-topped metal cage is placed around the plot to deter entry by predatory whelks and sea stars and where mussel and barnacle colonization occurs undeterred (to test predation), 4)  predator exclusion + barnacle removal cages in which predator are excluded plus barnacle settlers removed (to test facilitation by barnacles of mussels), and 5)  predator exclusion + mussel removal cages  in which predator are excluded plus mussel settlers removed  (to test competition effects of mussels on barnacles). All plots are photographed approximately monthly, and treatments are maintained by removing predators that in the cages and by clearing the relevant competitors (mussels or barnacles). Photos are analyzed by overlaying a 5 x5 grid onto the photo in Image J (so that each square is 4% cover) and estimating the % cover of each major space holder to the nearest 1%.  Space holders include: free space, algal crusts, acorn barnacles, gooseneck barnacles, mussels, articulated coralline algae, foliose algae and other sessile invertebrates. We also count the number of sea stars, whelks, and other herbivores.  Each spring, all plots are cleared and biomass collected (except controls). Biomass of functional groups is measured as wet and dry mass of mussels, barnacles, gooseneck barnacles, mobile predators, herbivores, and other. 

* Table within sheet 1 of the submitted file "BCODMOSubmission_ACEMasterWide_ByFunc_2025-07-16.xlsx" was imported into the BCO-DMO data system for this dataset. Values "NA" imported as missing data values. Table will appear as Data File: 990939_v1_ace-experiment.csv (along with other download format options).

Missing Data Identifiers:
* In the BCO-DMO data system missing data identifiers are displayed according to the format of data you access. For example, in csv files it will be blank (null) values. In Matlab .mat files it will be NaN values. When viewing data online at BCO-DMO, the missing value will be shown as blank (null) values.

* Table within BCODMO_SiteList_STARS_2023-04-11_SAG.xlsx added as supplemental file sitelist_stars.csv

NSF abstract:

In recent decades, ocean ecosystems, long thought to be immune to change, have undergone disruptions to their structure, diversity, and geographic range, yet the actual underlying reasons for such changes in oceanic biota are often unclear. Coastal intertidal zones (i.e., the shore between high and low tides) have long served as important ecological model systems because of advantages in accessibility and ease of observation, occupancy by easily studied and manipulated organisms of relatively short lifespans, and exposure to often severe environmental conditions. This research will address the stability of a well-known rocky shore system along the Oregon and California coasts. Prior long-term research indicates that, although casual observation suggests these systems are stable, in fact, they may be on the cusp of shifting into another state, losing iconic organisms like mussels and sea stars, and becoming dominated by seaweeds. These changes might be comparable to losing trees and large predators from terrestrial systems. This study would result in the training of undergraduates and graduate students, including individuals from under-represented groups. Additionally, this study would include outreach to the general public.

The researchers will focus particularly on impacts of increasing and more variable warming on community recovery. For example, climate oscillations (e.g., El Niño), coastal upwelling, and particularly temperature have all changed in recent decades in ways leading to increased stress on intertidal biota. In apparent response, coastal ecosystems evidently have become less productive, organismal performance (growth, reproduction) has declined, and key dynamical processes (species interactions) have weakened. The new research will pursue these strong hints of an impending “tipping point” by (1) continuing the projects that led to the insights of increasing instability, (2) adding new projects that will pinpoint ecological changes, and (3) expanding the region of work to include locations in California. Research will assess whether or not sea stars recover from wasting disease, experimentally test if species interactions are indeed weakening, quantify the annual inputs of new prey and changes in abundance, diversity, stability, and resilience of intertidal communities, and document changes in the physical environment. Using field observations and experiments, the research will provide insight into impacts of environmental change, particularly warming, on the future of coastal ecosystems, and more generally, into possible future states of Earth’s ecosystems. Using these data, we will test the hypothesis that direct and indirect effects of climate change are driving, or may drive these systems into new, alternative states.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.