Search results | Digital Commons of Moss Landing Marine Laboratories

Title: Ice ages and ecological transitions on temperate coasts
Description: Organisms face continual fluctuations in global climatic processes to which they must adapt or perish. Considering that many species are key habitat formers and energy producers, such responses to climate change can have significant population, community and even ecosystem consequences. Paleo-records of ecosystem responses to past environmental variability have proven invaluable for studying impacts of climate change on natural systems, yet such records are almost completely lacking for temperate benthic marine systems. Here, we bring together recent advances in paleoclimatology, coastal geomorphology, paleoceanography and archaeology for a well-studied region (the Southern California Bight, USA). We argue that there is now enough evidence to show that late-Quaternary sea-level rise over the past 18 500 years has caused a large-scale ecological shift in this region from highly productive rocky reefs to less productive sandy shores. Our integrated approach has implications for other temperate coastlines and helps provide insight into the interactions between human culture, biological communities and their environments., Cited By (since 1996):52, CODEN: TREEE
Author: Graham, Dayton, Erlandson
Date: 2003-01-01T00:00:00Z

Title: Grazing on giant kelp microscopic phases and the recruitment success of annual populations of Macrocystis pyrifera (Laminariales, Phaeophyta) in southern Chile,
Description: The giant kelp Macrocystis pyrifera (L.) C. Agardh is widely distributed in the Northern Hemisphere and Southern Hemisphere, yet it exhibits distinct population dynamics at local to regional spatial scales. Giant kelp populations are typically perennial with the potential for year-round reproduction and recruitment. In southern Chile, however, annual giant kelp populations exist and often persist entirely on secondary substrata (e.g., shells of the slipper limpet Crepipatella fecunda [Gastropoda, Calyptraeidae]) that can cover up to 90% of the rocky bottom. In these populations, the macroscopic sporophyte phase disappears annually during winter and early spring, leaving a 3-4month period in which a persistent microscopic phase remains to support the subsequent year's recruitment. We tested the effects of a suite of grazers on the recruitment success of this critical microscopic phase at two sites in southern Chile. Field experiments indicated that the snail Tegula atra negatively impacted M. pyrifera sporophyte recruitment, but that recruitment was highest in the presence of sessile female limpets, C. fecunda. Conversely, small male C. fecunda (biofilm grazers) did not regulate kelp recruitment. Laboratory observations showed that C. fecunda males only grazed on microscopic kelp gametophytes and small (<250μm) sporophytes, rejecting larger sporophytes, whereas T. atra grazed on all the kelp stages. Recruitment to the C. fecunda treatments far exceeded that to bare rock in the absence of grazers but was not due to the physical presence of C. fecunda shells. We concluded that the key to M. pyrifera recruitment success in southern Chile is its capacity to colonize secondary substrates provided by the slipper limpet C. fecunda., Cited By (since 1996):1, CODEN: JPYLA, ,
Author: Henríquez, Buschmann, Maldonado, Graham, Hernández-González, Pereda, Bobadilla
Date: 2011-01-01T00:00:00Z

Title: Variability in per capita oogonia and sporophyte production from giant kelp gametophytes (Macrocystis pyrifera, Phaeophyceae)
Description: Vegetative growth and fertility of kelp gametophytes are thought to be antagonistic, such that most successful kelp recruitment is assumed to result from fertilization of single oogonia released from unicellular female gametophytes. We used laboratory culture experiments to study the effect of temperature and nutrient addition on the per capita production of oogonia and sporophytes from Macrocystis pyrifera female gametophytes. Our results indicate that individual multicellular female gametophytes can give rise to more than one oogonium and that per capita oogonia production significantly increases with the enhancement of culture conditions (i.e., decreased temperature and increased nutrient concentration). Furthermore, the production of multiple oogonia per female often led to the production of multiple sporophytes per female. We discuss the importance of these results relative to variability in M. pyrifera life histories (e.g., annual vs. perennial) and their likely ecological and evolutionary consequences., Cited By (since 1996):11, Seaweeds
Author: Muñoz, Hernández-González, Buschmann, Graham, Vásquez
Date: 2004-01-01T00:00:00Z

Title: Arrested development of giant kelp (Macrocystis pyrifera, Phaeophyceae) embryonic sporophytes: A mechanism for delayed recruitment in perennial kelps?
Description: Delayed recruitment of microscopic stages in respouse to cyclical cues is critical to the population dynamics of many annual and seasonally reproducing perennial seaweeds. Microscopic stages may play a similar role in continuously reproducing perennials in which adult sporophytes are subject to episodic mortality, if they can respond directly to the unpredictable onset and relaxation of unfavorable conditions. We experimentally evaluated the potential for temporary reduction in limiting resources (light, nutrients) to directly delay recruitment of giant kelp (Macrocystis pyrifera (L.) C.A. Agardh) gametophytes and embryonic sporophytes. Laboratory cultures were subjected to limiting conditions of light and nutrients for 1 month and then exposed to non-limiting conditions for 10 days. Gametophytes in all treatments failed to recruit to sporophytes after 2 weeks, suggesting they are not a source of delayed recruitment in giant kelp. Sporophytes in light-limited treatments, however, survived and grew significantly slower than non-light-limited controls. When stimulated with light, light-limited sporophytes grew from 2 to >10 times faster than unstimulated controls depending on nutrient availability. These results suggest that limiting resources can delay recruitment of embryonic giant kelp sporophytes for at least 1 month. Flexible timing of recruitment from embryonic sporophytes may enhance persistence of continuously reproducing perennial species when macroscopic adults are subject to episodic large-scale removals., Cited By (since 1996):24, Seaweeds, CODEN: JPYLA
Author: Kinlan, Graham, Sala, Dayton
Date: 2003-01-01T00:00:00Z

Title: The acoustic identification and enumeration of scyphozoan jellyfish, prey for leatherback sea turtles (Dermochelys coriacea), off central California
Description: Acoustic-sampling techniques were developed to estimate the abundance and distribution of scyphozoan jellyfish, prey for leatherback turtles foraging off central California. Acoustic data were analysed from regions where jellyfish were present or absent from corresponding net tows. Empirical data on bell-diameter distribution (mean 26.2 cm; s.d. 10.6) were used to estimate target strength (TS; dB re 1 m 2) at 18, 38, 70, 120, and 200 kHz using a distorted-wave Born approximation scattering model. TS measurements of in situ animals at 38 and 200 kHz averaged -63.9 and -70.5 dB, compared with the model estimates of -54.9 and -64.0 dB, respectively. The model estimates of TS at 18, 70, and 120 kHz were -53.9, -59.9, and -61.8 dB, respectively. Using these TS estimates, an algorithm was developed to extract jellyfish echoes from total acoustic backscatter. Echo-integration methods applied to regions where net catches contained jellyfish resulted in an estimate of mean numerical abundance of 3217 jellyfish (s.d. 2276) with a mean density of 251 522 jellyfish nautical mile -2 (s.d. 57 504) and a mean concentration of 0.003 jellyfish m -3 (s.d. 0.002). The novel methods developed will help characterize prey resources for leatherback turtles off central California. © United States Government, National Oceanographic and Atmospheric Administration 2010., Cited By (since 1996):5, Invertebrates, Marine Mammals, Birds & Turtles, CODEN: ICESE
Author: Graham, Harvey, Benson, Renfree, Demer

Title: Fifty years of the Journal of Phycology: What's the impact?
Description: Export Date: 4 September 2015
Author: Graham
Date: 2015-01-01T00:00:00Z

Title: Global ecology of the giant kelp Macrocystis: From ecotypes to ecosystems
Description: The giant kelp Macrocystis is the world's largest benthic organism and most widely distributed kelp taxon, serving as the foundation for diverse and energy-rich habitats that are of great ecological and economical importance. Although the basic and applied literature on Macrocystis is extensive and multinational, studies of large Macrocystis forests in the northeastern Pacific have received the greatest attention. This review synthesises the existing Macrocystis literature into a more global perspective. During the last 20 yr, the primary literature has shifted from descriptive and experimental studies of local Macrocystis distribution, abundance and population and community structure (e.g., competition and herbivory) to comprehensive investigations of Macrocystis life history, dispersal, recruitment, physiology and broad-scale variability in population and community processes. Ample evidence now suggests that the genus is monospecific. Due to its highly variable physiology and life history, Macrocystis occupies a wide variety of environments (intertidal to 60+ m, boreal to warm temperate) and sporophytes take on a variety of morphological forms. Macrocystis sporophytes are highly responsive to environmental variability, resulting in differential population dynamics and effects of Macrocystis on its local environment. Within the large subtidal giant kelp forests of southern California, Macrocystis sporophytes live long, form extensive surface canopies that shade the substratum and dampen currents, and produce and retain copious amounts of reproductive propagules. The majority of subtidal Macrocystis populations worldwide, however, are small, narrow, fringing forests that are productive and modify environmental resources (e.g., light), yet are more dynamic than their large southern California counterparts with local recruitment probably resulting from remote propagule production. When intertidal, Macrocystis populations exhibit vegetative propagation. Growth of high-latitude Macrocystis sporophytes is seasonal, coincident with temporal variability in insolation, whereas growth at low latitudes tracks more episodic variability in nutrient delivery. Although Macrocystis habitat and energy provision varies with such ecotypic variability in morphology and productivity, the few available studies indicate that Macrocystis-associated communities are universally diverse and productive. Furthermore, temporal and spatial variability in the structure and dynamics of these systems appears to be driven by processes that regulate Macrocystis distribution, abundance and productivity, rather than the consumptive processes that make some other kelp systems vulnerable to overexploitation. This global synthesis suggests that the great plasticity in Macrocystis form and function is a key determinant of the great global ecological success of Macrocystis., Cited By (since 1996):75
Author: Graham, Vásquez, Buschmann
Date: 2007-01-01T00:00:00Z

Title: Population ecology of the invasive kelp Undaria pinnatifida in California: Environmental and biological controls on demography,
Description: We combined field monitoring and laboratory experiments to examine the population ecology of both the microscopic and macroscopic stages of a new invasion of Undaria pinnatifida in California. Over the course of 1 yr, we observed 2 distinct recruitment pulses of individuals in the Santa Barbara harbor; the appearance of these pulses was strongly correlated with a 4°C drop in ocean temperature approximately 2 mo prior to recruitment. Cultures of zoospores and successive microscopic stages revealed thermal tolerances consistent with field recruitment data; individuals grown at 13°C had significantly higher survivorship than individuals grown at higher temperatures (harbor temperatures annually ranged from 12 to 21°C). The 2 cohorts also differed greatly in individual size, growth rate, and survival to maturity. Grazing by herbivores, predominately the native kelp crab Pugettia producta, effectively prevented nearly all individuals in the second cohort from reaching reproductive maturity. Grazer control was effective despite far higher rates of recruitment during the second recruitment pulse. Our results highlight the potential for extreme variability in U. pinnatifida demography mediated by local oceanographic and biotic factors. Understanding controls on U. pinnatifida demography helps to explain variation in the spread and impact of this invader worldwide, and allows better prediction of when and where U. pinnatifida may continue its invasion along the west coast of North America., Cited By (since 1996):33, CODEN: MESED, , , Downloaded from: www.int-res.com/articles/meps2004/268/m268p069.pdf (13 June 2014).
Author: Thornber, Kinlan, Graham, Stachowicz
Date: 2004-01-01T00:00:00Z

Title: Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity,
Description: Classic marine ecological paradigms view kelp forests as inherently temperate-boreal phenomena replaced by coral reefs in tropical waters. These paradigms hinge on the notion that tropical surface waters are too warm and nutrient-depleted to support kelp productivity and survival. We present a synthetic oceanographic and ecophysiological model that accurately identifies all known kelp populations and, by using the same criteria, predicts the existence of >23,500 km2 unexplored submerged (30- to 200-m depth) tropical kelp habitats. Predicted tropical kelp habitats were most probable in regions where bathymetry and upwelling resulted in mixed-layer shoaling above the depth of minimum annual irradiance dose for kelp survival. Using model predictions, we discovered extensive new deep-water Eisenia galapagensis populations in the Galápagos that increased in abundance with increasing depth to >60 m, complete with cold-water flora and fauna of temperate affinities. The predictability of deep-water kelp habitat and the discovery of expansive deep-water Galápagos kelp forests validate the extent of deep-water tropical kelp refugia, with potential implications for regional productivity and biodiversity, tropical food web ecology, and understanding of the resilience of tropical marine systems to climate change. © 2007 by The National Academy of Sciences of the USA., Cited By (since 1996):36, CODEN: PNASA, ,
Author: Graham, Kinlan, Druehl, Garske, Banks
Date: 2007-01-01T00:00:00Z

Title: Effect of high irradiance on recruitment of the giant kelp Macrocystis (Phaeophyta) in shallow water
Description: Laboratory and field experiments were done in Stillwater Cove, Carmel Bay, California, and Monterey Harbor, California, to determine the effect of photosynthetically active radiation (PAR) on the shallow (upper) limit of giant kelp, Macrocystis pyrifera (L.) C. Agardh. At shallow, depths, M. pyrifera did not recruit or grow to macroscopic size from gametophytes or embryonic sporophytes transplanted to vertical buoy lines; sharp decreases in PAR with depth coincided with observed recruitment and sporophyte distributions. Shade manipulations indicated that settlement of M. pyrifera zoospores was decreased, but not prohibited, by high PAR. Postsettlement stages (gametophytes and embryonic sporophytes), however, survived only under shade. These results suggest that high PAR can inhibit the recruitment of M. pyrifera to shallow water by killing its postsettlement stages; whether or not ultraviolet (UV) radiation also inhibits recruitment was not tested. In either case, however, it appears that high irradiance (PAR and/or UV) regulates the shallow limit of M. pyrifera prior to temperature and desiccation stresses inherent to intertidal regions. In an additional experiment, recruitment or growth of transplanted gametophytes or embryonic sporophytes of Macrocystis integrifolia Bory also did not occur at shallow, depths, suggesting that this shallow water species accesses high irradiance regions via a method other than sexual reproduction., Cited By (since 1996):31, Seaweeds, CODEN: JPYLA
Author: Graham
Date: 1996-01-01T00:00:00Z

Title: The kelp highway hypothesis: Marine ecology, the coastal migration theory, and the peopling of the Americas
Description: In this article, a collaborative effort between archaeologists and marine ecologists, we discuss the role kelp forest ecosystems may have played in facilitating the movement of maritime peoples from Asia to the Americas near the end of the Pleistocene. Growing in cool nearshore waters along rocky coastlines, kelp forests offer some of the most productive habitats on earth, with high primary productivity, magnified secondary productivity, and three-dimensional habitat supporting a diverse array of marine organisms. Today, extensive kelp forests are found around the North Pacific from Japan to Baja California. After a break in the tropicswhere nearshore mangrove forests and coral reefs are highly productivekelp forests are also found along the Andean Coast of South America. These Pacific Rim kelp forests support or shelter a wealth of shellfish, fish, marine mammals, seabirds, and seaweeds, resources heavily used historically by coastal peoples. By about 16,000 years ago, the North Pacific Coast offered a linear migration route, essentially unobstructed and entirely at sea level, from northeast Asia into the Americas. Recent reconstructions suggest that rising sea levels early in the postglacial created a highly convoluted and island-rich coast along Beringia's southern shore, conditions highly favorable to maritime hunter-gatherers. Along with the terrestrial resources available in adjacent landscapes, kelp forests and other nearshore habitats sheltered similar suites of food resources that required minimal adaptive adjustments for migrating coastal peoples. With reduced wave energy, holdfasts for boats, and productive fishing, these linear kelp forest ecosystems may have provided a kind of kelp highway for early maritime peoples colonizing the New World., Cited By (since 1996):22, Seaweeds
Author: Erlandson, Graham, Bourque, Corbett, Estes, Steneck

Title: Net dextral slip, Neogene San Gregorio-Hosgri fault zone, coastal California: Geologic evidence and tectonic implications,
Description: Reinterpretation of onshore and offshore geologic mapping, examination of a key offshore well core, and revision of cross-fault ties indicate Neogene dextral strike slip of 156 ± 4 km along the San Gregorio-Hosgri fault zone, a major strand of the San Andreas transform system in coastal California. Delineating the full course of the fault, defining net slip across it, and showing its relationship to other major tectonic features of central California helps clarify the evolution of the San Andreas system. San Gregorio-Hosgri slip rates over time are not well constrained, but were greater than at present during early phases of strike slip following fault initiation in late Miocene time. Strike slip took place southward along the California coast from the western flank of the San Francisco Peninsula to the Hosgri fault in the offshore Santa Maria basin without significant reduction by transfer of strike slip into the central California Coast Ranges. Onshore coastal segments of the San Gregorio-Hosgri fault include the Seal Cove and San Gregorio faults on the San Francisco Peninsula, and the Sur and San Simeon fault zones along the flank of the Santa Lucia Range. Key cross-fault ties include porphyritic granodiorite and overlying Eocene strata exposed at Point Reyes and at Point Lobos, the Nacimiento fault contact between Salin- ian basement rocks and the Franciscan Complex offshore within the outer Santa Cruz basin and near Esalen on the flank of the Santa Lucia Range, Upper Cretaceous (Cam- panian) turbidites of the Pigeon Point Formation on the San Francisco Peninsula and the Atascadero Formation in the southern Santa Lucia Range, assemblages of Franciscan rocks exposed at Point Sur and at Point San Luis, and a lithic assemblage of Meso- zoic rocks and their Tertiary cover exposed near Point San Simeon and at Point Sal, as restored for intrabasinal deformation within the onshore Santa Maria basin. Slivering of the Salinian block by San Gregorio-Hosgri displacements elongated its northern end and offset its western margin delineated by the older Nacimiento fault, a sinistral strike-slip fault of latest Cretaceous to Paleocene age. North of its juncture with the San Andreas fault, dextral slip along the San Gregorio-Hosgri fault augments net San Andreas displacement. Alternate restorations of the Gualala block imply that nearly half the net San Gregorio-Hosgri slip was accommodated along the offshore Gualala fault strand lying west of the Gualala block, which is bounded on the east by the current master trace of the San Andreas fault. With San Andreas and San Gregorio-Hosgri slip restored, there remains an unresolved proto-San Andreas mismatch of ~100 km between the offset northern end of the Salinian block and the southern end of the Sierran-Tehachapi block. On the south, San Gregorio-Hosgri strike slip is transposed into crustal shortening associated with vertical-axis tectonic rotation of fault-bounded crustal panels that form the western Transverse Ranges, and with kinematically linked deformation within the adjacent Santa Maria basin. The San Gregorio-Hosgri fault serves as the principal link between transrotation in the western Transverse Ranges and strike slip within the San Andreas transform system of central California. © 2005 Geological Society of America., Cited By (since 1996):2, ,
Author: Dickinson, Ducea, Rosenberg, Greene, Graham, Clark, Weber, Kidder, Brabb, Ernst
Date: 2005-01-01T00:00:00Z

Title: Confronting multicollinearity in ecological multiple regression,
Description: The natural complexity of ecological communities regularly lures ecologists to collect elaborate data sets in which confounding factors are often present. Although multiple regression is commonly used in such cases to test the individual effects of many explanatory variables on a continuous response, the inherent collinearity (multicollinearity) of confounded explanatory variables encumbers analyses and threatens their statistical and inferential interpretation. Using numerical simulations, I quantified the impact of multicollinearity on ecological multiple regression and found that even low levels of collinearity bias analyses (r ≥ 0.28 or r2 ≥ 0.08), causing (1) inaccurate model parameterization, (2) decreased statistical power, and (3) exclusion of significant predictor variables during model creation. Then, using real ecological data, I demonstrated the utility of various statistical techniques for enhancing the reliability and interpretation of ecological multiple regression in the presence of multicollinearity., Cited By (since 1996):503, CODEN: ECOLA, ,
Author: Graham
Date: 2003-01-01T00:00:00Z

Title: Effects of local deforestation on the diversity and structure of southern California giant kelp forest food webs,
Description: It has been hypothesized that the high diversity of giant kelp forests is due primarily to the provision of energy and habitat by the giant kelp (Macrocystis pyrifera). In this article, I use a 19-year-long kelp forest-monitoring data set from the Channel Islands National Park (a) to identify associations between subtidal species and forested or deforested habitats, (b) to generate an idealized food web for Southern California giant kelp forests in order to identify the primary conduits of energy flow through the system, and (c) to determine changes in the diversity and complexity of this food web due to localized giant kelp deforestation. A total of 275 common species were observed in the park between 1982 and 2000, of which 36% occurred significantly more often in kelp-forested areas than in deforested areas (that is, sea urchin barrens); 25 species were found exclusively in forested areas. Most of these associations were clearly identified as trophic and/or structural associations with giant kelp itself. The producer level of the food web was diverse, although giant kelp apparently represents the greatest single source of fixed carbon through either direct grazing or the production of phytodetritus. Primary, secondary and tertiary consumer levels were also represented by numerous species, and generalist consumers were common. With deforestation, the source of primary production shifts from primarily kelps to ephemeral microalgae, macroalgae, and phytoplankton. These results support the reliance of giant kelp forest food-web structure and diversity on the presence of the forest itself., Cited By (since 1996):90, Seaweeds, Ecology, CODEN: ECOSF, ,
Author: Graham
Date: 2004-01-01T00:00:00Z

Title: How old is MVII?-seaweeds, shorelines, and the pre-clovis chronology at Monte Verde, Chile
Description: Cited By (since 1996):7
Author: Erlandson, Braje, Graham
Date: 2008-01-01T00:00:00Z

Title: Adrenal function in wild and rehabilitated pacific harbor seals (Phoca vitulina richardii) and in seals with phocine herpesvirus-associated adrenal necrosis,
Description: Adrenal function in harbor seals (Phoca vitulina richardii) was evaluated using adrenocorticotrophic hormone (ACTH) stimulation tests and fecal cortisol levels. The effect of ACTH administration on plasma cortisol and aldosterone levels in five free-living and 14 rehabilitated harbor seal pups was determined using enzyme immunoassay and radioimmunoassay, respectively. In free-living seals, injection of ACTH caused a significant increase in mean plasma cortisol but not of mean aldosterone levels 60 min postinjection. In these seals, mean initial plasma aldosterone was significantly higher than initial levels in rehabilitated seals, while initial cortisol levels were similar. Of the rehabilitated seals, eight died with adrenal cortical necrosis associated with herpesvirus inclusions, while six lived to be released. In the seals that were released, both mean initial cortisol levels and response to ACTH decreased through rehabilitation. In the seals that died, mean initial cortisol and response to ACTH increased through rehabilitation. The differences between initial cortisol levels in seals that lived and those that died were significant at weeks two and four of rehabilitation but not at the week of admission. There was considerable individual variation in initial plasma aldosterone levels and responses to ACTH, although initial aldosterone levels were significantly higher in rehabilitated seals that died than in seals that lived. Seals with adrenal necrosis associated with herpesvirus infection did not have decreased adrenal hormone responses to ACTH. Differences between initial hormone levels and responses to ACTH in different groups of seals may be associated with differing stress levels. Fecal cortisol assays were not a useful method of assessing adrenal function in these seals, as measured levels did not correlate with plasma cortisol levels., Cited By (since 1996):13, CODEN: MMSCE, , , Marine Mammals, Birds & Turtles
Author: Gulland, Haulena, Lowenstine, Munro, Graham, Bauman, Harvey
Date: 1999-01-01T00:00:00Z

Title: Warmer temperatures reduce the influence of an important keystone predator
Description: Predator-prey interactions may be strongly influenced by temperature variations in marine ecosystems. Consequently, climate change may alter the importance of predators with repercussions for ecosystem functioning and structure. In North-eastern Pacific kelp forests, the starfish Pycnopodia helianthoides is known to be an important predator of the purple sea urchin Strongylocentrotus purpuratus. Here we investigated the influence of water temperature on this predator-prey interaction by: (1) assessing the spatial distribution and temporal dynamics of both species across a temperature gradient in the northern Channel Islands, California, and (2) investigating how the feeding rate of P. helianthoides on S. purpuratus is affected by temperature in laboratory tests. On average, at sites where mean annual temperatures were <14°C, P. helianthoides were common, S. purpuratus was rare and kelp was persistent, whereas where mean annual temperatures exceeded 14°C, P. helianthoides and kelp were rare and S. purpuratus abundant. Temperature was found to be the primary environmental factor influencing P. helianthoides abundance, and in turn P. helianthoides was the primary determinant of S. purpuratus abundance. In the laboratory, temperatures >16°C (equivalent to summer temperatures at sites where P. helianthoides were rare) reduced predation rates regardless of predator and prey sizes, although larger sea urchins were consumed only by large starfishes. These results clearly demonstrate that the effect of P. helianthoides on S. purpuratus is strongly mediated by temperature, and that the local abundance and predation rate of P. helianthoides on sea urchins will likely decrease with future warming. A reduction in top-down control on sea urchins, combined with other expected impacts of climate change on kelp, poses significant risks for the persistence of kelp forests in the future.
Author: Bonaviri, Graham, Gianguzza, Shears

Title: Population dynamics of giant kelp Macrocystis pyrifera along a wave exposure gradient,
Description: Sporophyte recruitment, holdfast growth, and mortality of giant kelp Macrocystis pyrifera were measured seasonally on permanent transects at 3 sites (protected, intermediate, and exposed) along a wave exposure gradient on the Monterey Peninsula, central California (USA) between 1986 and 1991. The constant presence of cold, nutrient-rich water and the relative absence of other kelps and large grazers allowed the dynamics of M. pyrifera populations to be examined under conditions in which wave exposure was highly variable and influences of other abiotic and biotic factors were minimized. Recovery of M. pyrifera populations from decreased adult density (presumably due to storm-induced mortality; adult density was negatively correlated with storm activity) was a 2-stage process requiring the establishment of juvenile populations and conditions suitable for juvenile growth to adult size. Sporophyte recruitment was negatively correlated with M. pyrifera canopy cover, and thus appeared to be related to irradiance. Recruitment was low and continuous under a temporally stable M pyrifera canopy at the protected site. At the intermediate and exposed sites, canopy cover was more variable, canopy loss was greater, and durations of low canopy cover were longer than at the protected site, resulting in episodic sporophyte recruitment. These distinct patterns in sporophyte recruitment resulted in continuous juvenile populations at the protected site and intermittent juvenile populations at the intermediate and exposed sites. Growth of juveniles to adult size required additional irradiance probably due to greater light requirements for juvenile growth than for sporophyte recruitment. We observed that juveniles grew to adult size when canopy cover was low and adults were below a threshold density estimated at ~10 plants 100 m-2, but juveniles also occasionally grew to adult size following periods of low canopy cover only. Episodic sporophyte recruitment at the intermediate and exposed sites resulted in decreased coincidence of the 2 recovery stages; adult densities were often decreased below threshold prior to the establishment of juvenile populations. Recovery time, that required by populations to return to densities above threshold, was equal to the time lag between occurrence of the 2 recovery stages and was therefore greatest at the more exposed sites. Comparisons between central and southern California M. pyrifera populations suggest that by altering recovery time, variable frequency and magnitude of storm disturbance may result in different periodicities of adult population cycles., Cited By (since 1996):58, CODEN: MESED, ,
Author: Graham, Harrold, Lisin, Light, Watanabe, Foster
Date: 1997-01-01T00:00:00Z

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