Episodes of decrease in mean sorus area (indicating that the release of mature spores was greater than the production of new spores, which hereafter is defined as net spore release) varied in duration from as little as 1 wk (April 1994) to as much as 2 mo (June to August 1993 and January to March 1994).
Mean sorus area steadily increased in these individuals until mid-January 1993, when an abrupt 50% decline in mean sorus area was observed during a single sample period [ILLUSTRATION FOR FIGURE 2A OMITTED].
In addition to the dramatic decrease in sorus area following the storm, individual Macrocystis lost on average 60% of their fronds.
For both Macrocystis and Pterygophora there was a significant positive relationship between the total spore release for a sample period (as estimated by total decrease in sorus area or in sporangium density summed over all individuals for Macrocystis and Pterygophora, respectively) and the percentage of individuals that showed net spore release during the same sample period, as indicated by a decrease in sorus area or sporanglum density ([F.sub.1.85] = 117.138, P = 0.0001 for Macrocystis, and [F.sub.1,15] = 94.379, P = 0.0001 for Pterygophora; [ILLUSTRATION FOR FIGURES 6A, B OMITTED]).
For a given sample period, total spore release in Macrocystis (total decrease in sorus area summed over all plants sampled) was positively correlated to the density of female gametophytes that settled in the study area; however, it only explained a relatively small amount of variation ([F.sub.1,59] = 15.93, P = 0.0002, [R.sup.2] = 0.21).
Synchronized reproduction in Pterygophora is most likely triggered by photoperiod, which is known to activate growth in Pterygophora (Luning 1993) and sorus formation in other perennial kelps (Luning 1988, tom Diek 1991).
- Estimates of sorus area per frond indicate that Macrocystis produces two large crops of spores during most years [ILLUSTRATION FOR FIGURE 2A OMITTED].
This seasonal pattern of spore allocation in Macrocystis was not observed in 1992 when sorus area per frond was relatively low and variable throughout the year.
Compared to reproductive allocation, seasonal variation in spore standing stock (estimated as sorus area per plant) in Macrocystis was less consistent among years.
In comparison to Naples Reef plants, however, Shallow Goleta Bay plants were generally larger (and presumably older) with substantially more sorus area, both per plant and per sporophyll.
Finally, spore C/N was unrelated to sorus area in both species.
Sorus area per frond and sorus area per plant in Macrocystis remained negatively correlated with temperature, even when analyses were confined to data collected during the cool months of November through April (Table 4).