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- Title
- Reproductive longevity of drifting kelp Macrocystis pyrifera (Phaeophyceae) in Monterey Bay, USA,
- Description
- Drifting Macrocystis pyrifera (L.) C. Agardh sporophytes have long been viewed as the primary long-distance dispersal vector; yet, few data exist that support the ability of reproductive viable sporophytes to actually travel the presumed hundreds to thousands of kilometers. This study addressed the reproductive longevity of experimental and naturally occurring M. pyrifera drifters. Temporal variability in sporophyte size and reproduction was estimated for experimental drifting sporophytes that were tethered to surface buoys and compared with attached plants (controls). Reproductive viability was also studied for beach-cast drifters (BCD), and naturally drifting sporophytes observed during field surveys in Monterey Bay. Detached drifting sporophytes were tracked with radio transmitters to follow drifter trajectories and to measure drifting speed. Experimental drifters (ED) experienced a 74% reduction in frond length after 35 days, a 76% reduction in average frond number after 70 days, and a reduction in average sorus area by 83% after 28 days. Although zoospore production was reduced following detachment, sporophytes remained fertile with high zoospore germination success as long as sori were present (125 days). Zoospore production and germination success for natural and BCD was similar to ED. The average displacement of radio-tagged drifters was 7.12 km·day-1, suggesting that a sporophyte adrift for 125 days disperses viable propagules (zoospores) over 890 km (±363). Dispersal of propagules is important for population restoration, distribution, and genetic diversity. Such dispersal distances are long enough to connect potentially all Northern Hemisphere Macrocystis populations across a generational timescale and may facilitate inter-hemispheric gene flow. © 2006 by the Phycological Society of America., Cited By (since 1996):34, CODEN: JPYLA, ,
- Author
- Hernández-Carmona, Hughes, Graham
- Date
- 2006-01-01T00:00:00Z
- Title
- Factors determining the upper limit of giant kelp, Macrocystis pyrifera Agardh, along the Monterey Peninsula, central California, USA,
- Description
- Abiotic and biotic factors determining the upper (shallow or nearshore) limit of giant kelp, Macrocystis pyrifera Agardh, were examined along a wave exposure gradient on the Monterey Peninsula, central California, USA. Wave modeling, analysis of aerial photographs from 1986 to 1989 and SCUBA surveys from 1993 to 1995 indicated a significant positive relationship between wave intensity and depth of the upper limit of giant kelp; increased wave intensity resulted in the upper limit moving offshore into deeper water presumably due to direct removal of adult giant kelp plants by waves. Further, during periods of high wave intensity, plants with canopies were restricted to deeper water than those without canopies, suggesting that wave- induced giant kelp mortality was related to plant biomass (i.e. drag). Removal of giant kelp from shallow water (≤ 2.5 m depth) during periods of high wave intensity may have facilitated the development of dense algal turf assemblages by reducing light limitation; clearing experiments indicated that algal turf inhibited giant kelp recruitment at depths ≤ 2.5 m. Under extended periods of low wave intensity, however, giant kelp can establish populations in shallow water as indicated by the shallower depth of continuous giant kelp canopies with decreasing wave exposure. Thus, algal community structure in these shallow subtidal regions along the Monterey Peninsula appears to be determined by disturbance-mediated competition; with a lack of disturbance favoring giant kelp, disturbance favoring algal turf. These data support the hypothesis that the upper limit of giant kelp is controlled by an interaction between abiotic and biotic factors., Cited By (since 1996):36, CODEN: JEMBA, ,
- Author
- Graham
- Date
- 1997-01-01T00:00:00Z
- Title
- Post-glacial redistribution and shifts in productivity of giant kelp forests
- Description
- Quaternary glacial-interglacial cycles create lasting biogeographic, demographic and genetic effects on ecosystems, yet the ecological effects of ice ages on benthic marine communities are unknown. We analysed long-term datasets to develop a niche-based model of southern Californian giant kelp (Macrocystis pyrifera) forest distribution as a function of oceanography and geomorphology, and synthesized palaeooceanographic records to show that late Quaternary climate change probably drove high millennial variability in the distribution and productivity of this foundation species. Our predictions suggest that kelp forest biomass increased up to threefold from the glacial maximum to the mid-Holocene, then rapidly declined by 40-70 per cent to present levels. The peak in kelp forest productivity would have coincided with the earliest coastal archaeological sites in the New World. Similar late Quaternary changes in kelp forest distribution and productivity probably occurred in coastal upwelling systems along active continental margins worldwide, which would have resulted in complex shifts in the relative productivity of terrestrial and marine components of coastal ecosystems. © 2009 The Royal Society., Cited By (since 1996):2, CODEN: PRLBA
- Author
- Graham, Kinlan, Grosberg
- Date
- 2010-01-01T00:00:00Z