Intertidal Ecology of Fucus, San Juan Island, Washington

  • Map: Map of our study sites
  • Sites: Table describing each site’s physical features
  • Graphs: Sample graphs illustrating some of the temperature data
  • Data: Links to downloadable temperature data from each site
  • Contact: Principal Investigators

Please read the following text, and our related publications, for more details on the studies.

Extreme temperatures and accompanying desiccation are probably the physiological stresses most likely to damage intertidal organisms and limit their potential production ­ this happens when abiotic factors exceed some threshold for optimal organismal function. We are examining the roles of temperature and other abiotic and biotic parameters on the ecophysiology of the common intertidal alga, Fucus. Our study tests the interactive effects of abiotic stress and herbivory, which can also affect algae (via altering production, distribution, abundance, chemistry and morphology). Little is known about the interactive effects of stress and herbivory on resource allocation to growth versus reproduction or other major resource sinks.

fucus

Fucus is a model organism for our research. It is very common on protected and semiprotected shorelines from Alaska to central California, it forms dense canopies in the intertidal zone, and its broad vertical distribution encompasses a presumed stress gradient (i.e., high to low on the shore).

Fucus San Juan Island location

We performed our observations at 14 field sites around San Juan Island, Washington. This unusually large number of sites was used in an attempt to encompass the range of variation in physical parameters and biotic environments experienced by this algal species. The San Juan Islands are at the northern end of the Puget Trough and the eastern (inner) end of the Strait of Juan de Fuca. All sites are protected from full oceanic conditions. The map to the right illustrates the location of the islands relative to other major landmasses. The map of the sites shows San Juan Island relative to the other islands in the archipelago. Sites on the west side of the island are exposed to more swell and wind waves, while those on the other sides are relatively protected by nearby islands.

Table 1. lists the sites and their basic physical features; they vary not only in wave exposure but in compass heading and local shading, and thus exposure to desiccating conditions. All sites were bedrock shores of 15 to 30 degrees slope. We sampled in the High zone (near the upper limit of the Fucus) and Mid zone (ca. +1.5 and +0.8m) at 12 of the sites, and in 3 zones (ca. +1.5, +1, and +0.5) at the other 2 sites.

At each site we gathered detailed temperature data to examine the effect of this environmental variable on the growth and survival of Fucus. Environmental temperature data were gathered using "Stowaway TidbiT" loggers at the two tidal heights at each site. These small, waterproof loggers were attached to pieces of PVC and bolted to the rock; a piece of thick flexible plastic protected the glass optical-readout points but the sensor was exposed to the environment (see Photo). Each logger was programmed to read the temperature (of air or water) every 20 minutes. Algal canopies were regularly cleared away from the loggers, and data were downloaded every 3-4 months.

Fucus TidbitIn the San Juan Islands, at any given point on the rock, the total number of hours per day of exposure to air remains fairly constant throughout the year (ca. 50% of the time at the High level, 22% at the Mid). However, the timing of the lower low tides swings from daytime in the spring and summer to after dark in the fall and winter, and this change is clearly reflected in the TidbiT data.

Sample graphs illustrate a variety of ways of analyzing the data collected; the entire dataset for each site can also be downloaded. Mean maxima through the year are illustrated for the hottest and coolest sites, showing very similar seasonal patterns but substantial differences in degree of heating. Davison Head (DH) was a south-facing site and Point Caution (PC) north-facing. As expected, TidbiTs in the High zone consistently recorded hotter temperatures than in the Mid zone. A few sites (e.g. Hannah Heights) had Mid zones that were as hot or slightly hotter than the adjacent High zone; these data reflected the Mid TidbiT’s placement on a more-horizontal or a more-south-facing surface than the High one (See Table 1.). Temperature minima are not illustrated; no significant freezes occurred during the measurement period, and minima were seldom below 2ºC.

Possible ecological and physiological effects of these temperature differences are being analyzed for publication in several papers (in review and in preparation). We will describe observations of natural populations of Fucus, quantifying patterns of growth, reproduction, and phlorotannin levels across intertidal gradients in herbivory and stress. We also describe field and laboratory manipulations of these processes, measurements of physiological parameters and allocation patterns, and demographic consquences. The research provides some of the first data on how algae respond (in ecological time) to simultaneous variation in these two key selective factors.

Publications using these data:

Haring, R.N., M.N. Dethier, and S.L. Williams. 2002. Desiccation facilitates wave-induced mortality of the intertidal alga, Fucus gardneri. Marine Ecology Progress Series 232:75-82.

Dethier, M.N. and S.L. Williams. In preparation. The effects of seasonal environmental stresses on intertidal algal growth rates.

Funding Source: National Science Foundation, Grants OCE 98-98196078, 0196078, and 9901138.

Locations of Sites for Temperature Data on San Juan Island

  • Clicking on the links in blue in the data table will start downloading temperature data for that site.
  • Decompress the zipped file.
  • You can also download the entire dataset (6.6 MB compressed) all at once.
  • All data files are in Excel format.
  • Explanations of abbreviated names can be found below the map.
  • See "Sites" for descriptions of the physical characteristics of each site.

Study sites on San Juan Island, Washington

fucus map

DH = Davison Head RTN = ReubenTarte North RTS = ReubenTarte South PC = Point Caution
CCN = Colin’s Cove North CCS = Colin’s Cove South WIL = Willow’s Point PHE = PumpHouse East
PHW = PumpHouse West CPN = Cattle Point North CPS = Cattle Point South HH = Hannah Heights
LK = Lime Kiln State Park SJC = San Juan County Park    

Descriptions of physical characteristics of study sites on San Juan Island, Washington

Table 1. Descriptions of physical characteristics of study sites on San Juan Island, Washington

Site

Map

Abbrev

Aspect

(magn.)

GPS Reading

Wave

Exposure

Slope

(degrees)

Tidal Height
(m above MLLW)

Morning

Sun

N

W

High

Mid

Low

Colin’s Cove North CCN NNW

48 32.906

123 00.393

low

22

1.6

0.9

N/A

Low
Colin’s Cove South CCS E

48 32.910

123 00.397

fairly low

15

1.6

1.1

0.7

High
Cattle Point North CPN NE

48 27.120

122 57.714

fairly high

15

1.6

0.8

N/A

Moderate
Cattle Point South CPS SW

48 27.120

122 57.714

fairly high

30

1.7

1.0

N/A

Moderate
Davison Head DH WSW

48 37.335

123 09.158

fairly low

30

1.4

0.7

N/A

Moderate
Hannah Heights HH ENE

48 29.477

123 06.773

fairly high

15

1.7

0.9

N/A

Moderate
Limekiln Park LK NE

48 31.001

123 09.149

fairly high

20

1.8

1.1

N/A

Low
Point Caution PC NNW

48 35.779

122 41.462

moderate

20

1.4

0.6

N/A

Low
Pumphouse East PHE SSW

48 32.757

123 00.478

low

25

1.3

0.6

N/A

Moderate
Pumphouse West PHW S

48 32.767

123 00.498

low

20

1.5

0.7

N/A

Moderate
Reuben Tarte North RTN E

48 36.782

123 05.917

moderate

30

1.6

1.1

0.6

High
Reuben Tarte South RTS SE

48 36.752

123 05.858

moderate

30

1.5

0.7

N/A

High
San Juan County Park SJC NW

48 32.589

123 09.683

moderate

25

1.8

1.1

N/A

Low
Willows Point WIL SE

48 32.800

123 00.448

fairly low

25

1.1

0.4

N/A

High

Sample Intertidal Temperature Graphs:

Fucus DHH 12Fucus DHM 12

Midnight vs. Noon Daily Temperatures

In the San Juan Islands, at any given point on the rock, the total number of hours per day of exposure to air remains fairly constant throughout the year (ca. 50% of the time at the High level, 22% at the Mid). However, the timing of the lower low tides swings from daytime in the spring and summer to after dark in the fall and winter, and this change is clearly reflected in the TidbiT data.

Maximum vs. Minimum Daily Temperatures

Fucus DHH 12Fucus DHM MaxMin

Graphs illustrating daily maximum and minimum temperatures differ slightly from those comparing Noon and Midnight.

Fucus DH AverageFucus PC Average

Mean Maxima for High and Mid Tidal Heights

Mean maxima through the year are illustrated for the hottest and coolest sites, showing very similar seasonal patterns but substantial differences in the degree of heating. Davison Head (DH) was a south-facing site and Point Caution (PC) was north-facing. As expected, TidbiTs in the High zone consistently recorded hotter temperatures than in the Mid zone.

Fucus HH Average

Mean Maxima for Hannah Heights

A few sites (e.g. Hannah Heights,) had Mid zones that were as hot or slightly hotter than the adjacent High zone; these data reflected the Mid TidbiT’s placement on a more-horizontal or a more-south-facing surface than the High one.

Sample Graphs: Photosynthesis, Air Temp and Humidity and H20 Loss

Figs. 1 & 2 BELOW. Rates of net photosynthesis of Fucus gardneri, a common intertidal seaweed, were measured to determine the variation in rates among individuals from two tidal heights at 14 sites around San Juan Island, Washington. Rates of 10 individuals (with few exceptions) were measured in air (to mimic exposure at low tide) and in water (submersed) and in both summer and winter at each tidal height at each site. The graphs represent the complete data set. Rates have been adjusted for seaweed mass (Analysis of Covariance), which differed significantly across tidal elevations. Some sites could not be sampled in winter due to difficulties of working at low tide at night. Site abbreviations: CCN (Colins Cove North), CCS (Colins Cove South), CPN (Cattle Point North), CCS (Cattle Point South), DH (Davison Head), FHL (Friday Harbor Laboratories), HH (Hannah Heights), LK (Lime Kiln), PC (Point Caution), PHE (Pump House East), PHW (Pump House West), RTN (Rueben Tarte North), RTS (Rueben Tarte South), SJC (San Juan County), WIL (Willows).

figure 1

fucus fig1

figure 2

fucus fig 2

Figs. 3 & 4 BELOW. Air temperature and relative humidity just above a canopy of Fucus gardneri when exposed during two low tides in winter. Data were taken using a Viasala ruggedized probe and logger.

figure 3

fucus fig 3

figure 4

fucus fig 4

Fig. 5 BELOW. The loss of water from Fucus gardneri during wintertime low tides at Friday Harbor Laboratories, WA, was minimal during winter.

fucus fig 5

Temperature Data

  • Clicking on the links in blue in the data table will start downloading temperature data for that site.
  • Decompress the zipped file. All data files are in Excel format.
  • See "Sites" for descriptions of the physical characteristics of each site.
  • See "Map" to see the locations of each study site.
Site Abbreviations Site Name Date File, Size
CCN Colin’s Cove North 464 KB
CCS Colin’s Cove South 696 KB
CPN Cattle Point North 492 KB
CPS Cattle Point South 572 KB
DH Davison Head 452 KB
HH  Hannah Heights 504 KB
LK Lime Kiln State Park 500 KB
PC Point Caution 368 KB
PHE PumpHouse East 692 KB
PHW PumpHouse West 232 KB
RTN ReubenTarte North 416 KB
RTS ReubenTarte South 488 KB
SJC San Juan County Park 568 KB
WIL Willow’s Point 388 KB
Download Entire Set (6.6 MB)

Contact information

Dr. Susan Williams
Professor, Environmental Science and Policy
Bodega Marine Laboratory
University of California, Davis
Phone: (707) 875-2211
Fax: (707) 875-2009
Email: slwilliams@ucdavis.edu

Dr. Megan Dethier
Research Associate Professor, Zoology
University of Washington
Friday Harbor Laboratories
Phone: (206) 543-1484
Phone: (360) 378-2165
Fax: (206) 543-1273
Email: mdethier@u.washington.edu