Introduction

After searching the net and discovering a dearth of information regarding Pacific intertidal organisms, it was evident that more information on this subject was desperately needed. To certain members of the Spring 1998 Marine Biology class at the University of San Francisco, it also became apparent that creating such a web site was an ideal way to fulfill the class project requirement for the course. In this web site, our group set out to describe all the intertidal algae and invertebrates we observed at Pillar Point Harbor in Half Moon Bay. Through this study guide, we hope to provide a foundation for future students and for individuals surfing the net wanting to gain elementary knowledge of intertidal marine life.

Here's the text we used. (Click on image to enlarge)

 

 

Marine Biology

The Marine Biology course at the University of San Francisco, as taught by Dr. Paul K. Chien, emphasizes a survey approach to intertidal biology where the lab field work complements the lecture material. The course began with a global view of the oceans beginning with the formation of land masses, and progressed further into the physiology and morphology of various intertidal algae and organisms. Concluding the lecture portion of the course was a discussion of the dynamics of marine waters and the human influence on the ecology of the oceans. The lab portion of the course consisted of an intensive review of various intertidal algae and invertebrates, including identification to genus and species levels in such exercises as on site field practicals and lab keying exams. Field trips to such places as Pillar Point Harbor (Half-Moon Bay), Ocean Beach (San Francisco), Rockaway Beach (Pacifica), and Bean Hollow Beach (Half-Moon Bay) allowed for direct observation of intertidal life.

Right in our own back yard, California's coast lines offer some of the richest intertidal habitats of North America. Several factors contribute to this lush domain: 1) upwellings from the bottom of the ocean, bringing in nutrient rich waters; 2) a relatively stable temperate zone, preventing ice formation; and 3) coastal fogs, which aid in protection from heat.

 

 

What is an Intertidal Zone?

An intertidal zone is a narrow band consisting of three distinct zones (upper, middle, and lower) between the lowest and highest tide markers. Marking the area where the sea confronts the land, it is an area extremely rich in biological organisms.

 

 

Upper (High) Intertidal Zone

The highest area on the rocky shore community, the upper intertidal zone is also known as the Littorina zone for the main group of organisms that live in this area. Organisms that live in this area are equipped with the ability to protect themselves from desiccation, a necessity considering the water level seldom rises to this area.

 

 

Middle Intertidal Zone

This middle community is characterized by the prevalence of barnacles, rockweed, and mussels. An area where water occasionally covers its surface, the organisms that live in this zone must be able to survive in high salinity water during high tides; they must also be able to survive in the absence of water when the tide is low.

 

 

Lower Intertidal Zone

Most often this part of the rocky shore is underwater and exposed only partly at extremely low tide. When this region is exposed, it is a violent and hazardous area where strong waves and violent currents combat the land. All organisms living in this violent region have features that allow them to hold tightly to a solid substrate and to keep from being carried away into the deep abyss.

 

 

Mono Lake

Perhaps the most exciting and fascinating field trip took place just south of Yosemite at Mono Lake. Mono Lake is a truly unique body of water. Its salinity is three times that of the ocean owing to the sodium and other salts brought in via erosion that are concentrated as water evaporates from the lake. Additionally, the lake provides an abundant food source in the form of brine flies and brine shrimp for hundreds of thousands of migratory birds. In fact, this food source is so abundant that the entire sea gull population of California makes a yearly migration to this nutritious haven to mate and to take advantage of this ecological niche. Near Mono Lake are other great attractions such as a trout fishery, natural sulfur hot springs, and sand tufa-lined fissures. Some pictures taken from this trip are included in this site. CLICK HERE