BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 45 1 



These records of the bottom temperature between Gay Head and the ledges of Sow 

 and Pigs indicate that the average range is from below 35 in the winter to about 6o c 

 in the summer. The bottom temperature probably does not fall to the lowest winter 

 temperature of the sheltered waters of the Bay and Sound and does not rise to within 

 1 5 of the highest summer temperatures in such situations; the total range is close to 

 26 . The surface temperature between Gay Head and the ledges of Sow and Pigs is at 

 times in the summer 4 to 5 higher than the bottom temperature, and in the winter 

 probably somewhat lower; the total range is close to 32 . The seasonal range in Great 

 Harbor, Woods Hole, is about 46 , and it must be more than 50 in the upper portions 

 of Buzzards Bay. 



The causes of these very different conditions are not difficult to understand. The 

 great range of temperature in the sheltered waters of the Bay and Sound is simply the 

 result of summer and winter atmospheric temperatures acting on bodies of water suffi- 

 ciently shallow to respond very quickly to their influences. Tables 9 and 10 (pp. 46- 

 47), giving the average monthly range of the temperatures of both air and water at 

 Woods Hole over a five-year period, make clear the relationship, also shown on chart 

 219. The small range of the temperature of the bottom water between Gay Head and 

 the Sow and Pigs, together with the greater range of the surface water, shows the effect 

 of proximity to the deeper cold water of the open sea, water which, as stated before, 

 appears to be an extension of the cold belt north of Cape Cod. 



It is clear from the above statements of the seasonal ranges of temperature in the 

 two extremes of the conditions presented within the limits of the Survey (first, the 

 bottom temperatures off Gay Head and Sow and Pigs; second, the temperatures of shel- 

 tered waters of the Bay and Sound) that several very different types of floras would be 

 expected, and this is the case. The uniformly cool bottom water of Gay Head and the Sow 

 and Pigs (generally below 6o°) admits of the development of a flora with a number of 

 species characteristic of northern waters. This flora is restricted to the lower portion of 

 Buzzards Bay and the westerly portion of Vineyard Sound and is distinguished by the 

 presence of the following species which are never found (at least during the summer) 

 in the more sheltered regions of the Bay and Sound : Chcetomorpha melagonium, Lami- 

 naria digitata, Plumaria elegans, Rhodomela subfusca, Actinococcus peltajormis, Gym- 

 nogongrus norvegicus, Euthora crisiata, Lomentaria rosea, Rhodymenia palmata, Deles- 

 seria sinuosa. It would be very interesting to know whether other northerly species 

 may not be present during the winter and spring and whether this cold-water flora 

 extends its range during the winter into more sheltered portions of the Bay and Sound, 

 but we have made no dredgings for algae off Gay Head in the winter and know nothing 

 of the deep-water flora of that season. 



The seasonal extremes in the sheltered portions of Buzzards Bay and Vineyard 

 Sound, as would be expected, give at least two distinct seasonal floras, (1) that of the 

 winter and early spring, and (2) that of midsummer and the early autumn. Some species 

 are found all the year round, but they are generally much more luxuriant at one season 

 than at the other. Many of the species are limited to a season of perhaps two or three 

 months and are never found at other times. It is not at present possible to discuss sat- 

 isfactorily the seasonal habits of the algae at Woods Hole, for they have been very little 

 studied during the winter, but such data as are known are included in the Catalogue. 



