Sampling

Sampling site was Canoe Beach at Northeastern University's Marine Research Center in Nahant, Massachusetts. A 25 meter transect line was laid horizontally in three zones, upper intertidal, middle intertidal, and lower intertidal. Every .5 meters the algae under the transect line was picked up and the longest piece was followed back to the holdfast. The longest frond coming from that holdfast was then used for observation. The samples were labeled with flagging tape tied at the holdfast. This method was used until there were six samples from each location.

Height

Using a meter stick, the thallus was measured from the holdfast to the longest point and recorded.

Age

Since gas bladders accumulate annually, developing in January, age of the alga can be determined by counting the amount of gas bladders present and adding one since gas bladders are not produced during the first year of life (Stengel, 1997).

Annual Growth

Using a meter stick, the distance from the bottom of the fifth (or bottom) gas bladder was measured to the bottom of the top gas bladder. That distance was then divided by the number of gas bladders to yield the growth/year. To determine the growth this year, the alga was measured from the bottom of the most recent gas bladder to the tip of the frond.

Pigment Concentration

The sampled fronds were collected from Nahant and brought back to Clark University to be sampled in the laboratory. Using a razor blade, 2 cm portions were cut from the bottom of the frond and directly above each of the gas bladders. Samples were placed into 1.5 mL, weighed, and placed in a freezer until processing. Samples were thawed and 1mL of DMSO was added to each of the tubes. The samples were then covered with foil and allowed to sit in the dark for 15 minutes. The thalli were removed from the tubes with tweezers and rinse with .25mLs of distilled water over the tubes. The thalli were then each placed into 15mL tubes with 1.5mLs of 100% acetone. The tubes were covered with foil and allowed to sit in the dark for two hours. The thalli were then discarded and the absorbances of the DMSO and acetone samples were measured. The DMSO was measured at 665, 631, 582, and 480 nm and the acetone was measured at 664, 631, 581, and 470 nm. The concentrations of the pigments were then calculated using the following formulas (Seely et al. 1972):

DMSO:

Chl a = A₆₆₅/73.6
Chl c = (A₆₃₁+A₅₈₂-0.3*A₆₆₅)/62.2
Fucox. = (A₄₈₀-0.772(A₆₃₁+A₅₈₂-0.297*A₆₆₅)-0.049*A₆₆₅)/130 

Acetone:

Chl a = A₆₆₄/73.6
Chl c = (A₆₃₁+A₅₈₁-0.3*A₆₆₄)/62.2
Fucox. = (A₄₇₀-1.239(A₆₃₁+A₅₈₁-0.3*A₆₆₄)/141

Total:

Chl a = Chl a _DMSO + Chl a _Acetone
Chl C = Chl c _DMSO + Chl c _Acetone
Fucox. = Fucox. _DMSO + Fucox. _Acetone