Sanctuary Integrated Monitoring Network
Monterey Bay National Marine Sanctuary
Rocky Shores_ map
Figure 1. Rocky shoreline within the Monterey Bay National Marine Sanctuary. [View Larger]
The Monterey Bay National Marine Sanctuary's rocky shores are characterized by a fascinating and diverse array of intertidal organisms. The dramatic influence of the mixed, semi-diurnal tidal cycle exposes intertidal invertebrates and algae to large fluctuations in temperature, desiccation (drying out) and wave action, with two high and two low tides per day. This range of environmental variables in turn interacts with biological factors to create the distinct zonation patterns evident on any trip to the rocky shore.

Individual species tend to occupy different parts of the intertidal gradient from the high intertidal zone, where environmental stress is highest, to the low intertidal zone, where biological interactions prevail. The striking vertical range occupied by these organisms has long motivated scientists and visitors to investigate the abundant and species-rich assemblage of intertidal organisms that thrive in the sanctuary. Many of the hundreds of marine species found on the rocky shore do not occur subtidally, contributing to the unique nature of this habitat at the interface of land and ocean.

Rocky shores make up about 39 percent of sanctuary shoreline habitat and primarily occur near the tips of and outside Monterey Bay, extending southward along the Big Sur coast and north toward San Francisco. Human use of sanctuary rocky shores ranges from research and education to harvesting, collection, tidepooling and recreation.

Shoreline Habitat Classification Interactive Map

Current research and monitoring efforts have two focus areas: Scientists have conducted baseline surveys of rocky-shore communities, and these systems are in turn monitored to understand trends in the abundance and distribution of numerous intertidal organisms. Establishing such baseline data will allow researchers and managers to assess future impacts on this ecosystem.

Various disturbances, which are well-documented occurrences in rocky shore habitats, can impact the typical patchy distributions of invertebrates and algae found in the intertidal zone. Natural forms of disturbance include waves, predation (e.g., sea otters remove mussels from rocky shores), wave-tossed rocks and logs, and substratum weathering and exfoliation. Anthropogenic (human-induced) disturbances include disease, collection and trampling, oils spills, ship groundings, coastal development and road maintenance.

Conservation Concerns

There are a number of conservation concerns relative to this habitat. These include the following:
The common brown seaweed, bladderwrack (Fucus gardneri) has flattened dichotomous branches with a prominent midrib.

This red alga is likely Cryptopleura ruprechtiana, which has elongate blades edged with small ruffles. The basal midrib subdivides into several veins distally.


Sanctuary rocky-shore monitoring programs collect information about key population characteristics such as abundance, size, density and diversity. This information helps resource managers and policy makers predict population changes due to both natural and human-induced disturbance and informs decisions about how to best protect these resources.

In the 1700s, whalers followed the gray whale migration to hunt and slaughter the giants for whale oil and other products. Lookouts were placed along points and promontories, and when whales were sighted, shore whaling vessels were launched. Some of Californiašs coastal towns, including San Simeon and Pacific Grove, were whaling stations.

PISCO biologists at UC Santa Cruz are monitoring the sanctuary's black abalone populations. They have documented the decimation of Southern California black abalone by withering syndrome and are monitoring the northward progression of the disease. Populations within the sanctuary appear to be stable, while more southern populations are in decline.

Rocky Shore
Visitor Use and Marine Reserves
The visitor-use survey project at Point Pinos in Pacific Grove has evaluated how visitors affect rocky-shore communities. This study established baseline data and evaluated visitor impact by comparing the abundance of organisms between high- and low-use areas.

Negative impacts from visitor use were found only in the high intertidal (> +2 ft. MLLW) in the form of reduced algal cover. However, given the likelihood of future increases in visitor use, continued monitoring of this site will provide data and information necessary to develop plans to manage visitor impact in the sanctuary's rocky shores.

Natural Variability and Long-term Comparisons
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