Search results | Digital Commons of Moss Landing Marine Laboratories

Title: Complementarity in marine biodiversity manipulations: Reconciling divergent evidence from field and mesocosm experiments,
Description: Mounting concern over the loss of marine biodiversity has increased the urgency of understanding its consequences. This urgency spurred the publication of many short-term studies, which often report weak effects of diversity (species richness) driven by the presence of key species (the sampling effect). Longer-term field experiments are slowly accumulating, and they more often report strong diversity effects driven by species complementarity, calling into question the generality of earlier findings. However, differences among study systems in which short- and long-term studies are conducted currently limit our ability to assess whether these differences are simply due to biological or environmental differences among systems. In this paper, we compared the effect of intertidal seaweed species richness on biomass accumulation in mesocosms and field experiments using the same pool of species. We found that seaweed species richness increased biomass accumulation in field experiments in both short (2-month) and long (3-year) experiments, although effects were stronger in the longterm experiment. In contrast, richness had no effect in mesocosm experiments, where biomass accumulation was completely a function of species identity. We argue that the short-term experiments, like many published experiments on the topic, detect only a subset of possible mechanisms that operate in the field over the longer term because they lack sufficient environmental heterogeneity to allow expression of niche differences, and they are of insufficient length to capture population-level responses, such as recruitment. Many published experiments, therefore, likely underestimate the strength of diversity on ecosystem processes in natural ecosystems. © 2008 by The National Academy of Sciences of the USA., Cited By (since 1996):33 Seaweeds, CODEN: PNASA, ,
Author: Stachowicz, Best, Bracken, Graham
Date: 2008-01-01T00:00:00Z

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: Effects of climate change on global seaweed communities,
Description: Seaweeds are ecologically important primary producers, competitors, and ecosystem engineers that play a central role in coastal habitats ranging from kelp forests to coral reefs. Although seaweeds are known to be vulnerable to physical and chemical changes in the marine environment, the impacts of ongoing and future anthropogenic climate change in seaweed-dominated ecosystems remain poorly understood. In this review, we describe the ways in which changes in the environment directly affect seaweeds in terms of their physiology, growth, reproduction, and survival. We consider the extent to which seaweed species may be able to respond to these changes via adaptation or migration. We also examine the extensive reshuffling of communities that is occurring as the ecological balance between competing species changes, and as top-down control by herbivores becomes stronger or weaker. Finally, we delve into some of the ecosystem-level responses to these changes, including changes in primary productivity, diversity, and resilience. Although there are several key areas in which ecological insight is lacking, we suggest that reasonable climate-related hypotheses can be developed and tested based on current information. By strategically prioritizing research in the areas of complex environmental variation, multiple stressor effects, evolutionary adaptation, and population, community, and ecosystem-level responses, we can rapidly build upon our current understanding of seaweed biology and climate change ecology to more effectively conserve and manage coastal ecosystems. © 2012 Phycological Society of America., Cited By (since 1996):8, Seaweeds, CODEN: JPYLA, ,
Author: Harley, Anderson, Demes, Jorve, Kordas, Coyle, Graham
Date: 2012-01-01T00:00:00Z

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: Coupling propagule output to supply at the edge and interior of a giant kelp forest
Description: Propagule dispersal is fundamental in regulating the strength of demographic and genetic interactions between individuals both within and among populations. I studied spatiotemporal variability in propagule (zoospore) supply of a continuously reproducing seaweed, giant kelp Macrocystis pyrifera, to examine: (1) the extent to which local zoospore production is coupled to (correlated with) temporal variability in zoospore supply; and (2) spatial variability in the strength of such coupling. Macrocystis pyrifera planktonic zoospores were quantified from seawater samples pumped on numerous dates in 1999 from just above the substratum at various sites in the Point Loma kelp forest, southern California, USA. Zoospore collections were made at a site in the forest interior approximately three times per month from late February through mid-November. Sample collection overlapped with complete demographic surveys of the local population (100 m2) to determine local reproductive output. Temporal variability in zoospore supply was strongly correlated with relative changes in the density .and size structure of local reproductive adult sporophytes; 76% of variability in zoospore supply was explained by local reproductive output. This tight coupling between zoospore supply and local reproduction appeared to be driven by low-displacement, oscillating currents in the forest interior due to the cumulative drag of adult sporophytes, which kept zoospores close to their release site. High coupling between zoospore supply and local reproduction was validated at two additional interior sites separated by 1 km; 78% of variability in zoospore supply was explained by local reproductive output at these sites. Due to lower sporophyte densities, however, the forest edges experienced rapid, unidirectional currents that appeared to transport zoospores far from their release site, effectively decoupling zoospore supply from local reproduction; only 38% of variability in zoospore supply was explained by local reproductive output at these sites. The results suggest that the size of and location within kelp populations is an important determinant of the importance of local reproduction to zoospore supply due to the effects of flow modification by kelp canopies on zoospore dispersal., Cited By (since 1996):27 Seaweeds, CODEN: ECOLA
Author: Graham

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: Plant-animal diversity relationships in a rocky intertidal system depend on invertebrate body size and algal cover
Description: Considerable research has examined the influence of herbivores on the maintenance of plant diversity, but fewer studies have examined the reciprocal effect of plant diversity on the animals that use the plant community for food and shelter, particularly in marine systems. Several mechanisms could underlie such effects. Animal diversity and abundance could be increased by complementary use of different plants by different animals, or by an indirect effect of plant diversity on plant production that results in more total plant biomass in high plant-diversity communities. Alternatively, plant species identity could play a dominant role leading to sampling effects or no effect of diversity at all. We conducted a sixyear field manipulation of the richness of rocky shore seaweeds in northern California and measured the effects of algal richness and identity on the invertebrate community, from meiofauna to macrofauna. We found that diverse algal communities hosted more species of both large and small invertebrates than the average algal monoculture but that the mechanisms underlying this pattern differed substantially for organisms of different size. More species of macrofauna occurred in the polycultures than in any of the monocultures, likely due to the greater total cover of algae produced in polycultures. Rare and common macrofaunal taxa responded to host plant species richness in opposite ways, with more occurrences of rare taxa and lower abundance of very common taxa in the polycultures. In contrast, meiofaunal richness in polycultures was no different than that of monocultures of finely branched species, leading to strong effects of algal identity. Our findings are similar to those from terrestrial systems in that the effects of plant diversity we observed were most related to the greater amount of habitat in polycultures as a result of overyielding in algal biomass. However, our findings differ from those in terrestrial systems in that the primary mechanisms for both richness and identity effects appear related to the value of plants as shelter from harsh abiotic conditions or predation rather than food, and in that animal body size altered the mechanisms underlying diversity effects. © 2014 by the Ecological Society of America.
Author: Best, Chaudoin, Bracken, Graham, Stachowicz
Date: 2014-01-01T00:00:00Z

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: Diversity enhances cover and stability of seaweed assemblages: The role of heterogeneity and time,
Description: Generalizations regarding the mechanisms underlying the effects of plant diversity on ecosystem processes, and whether the patterns transcend study systems remain elusive. Many terrestrial plant diversity manipulations have found that plant biomass increases with diversity, but most marine studies find little or no effect of seaweed diversity on producer biomass or production. However, differences in experimental approach (field vs. mesocosm) and duration (years vs. weeks) between published terrestrial and marine experiments confound the interpretation of these differences in response to changing diversity. We conducted a three-year field manipulation of seaweed diversity on intertidal rocky reefs in central California, USA, to examine the effect of diversity on seaweed cover. We found that diversity increased standing algal cover and decreased the availability of free space relative to monocultures, but this effect took nine months to materialize. Furthermore, diverse assemblages did not consistently exceed the best performing monocultures until 18 months after the experiment was initiated, suggesting that the effect of diversity strengthens over time. Overall, diversity's effect was consistently stronger than that of individual species and not attributable to the influence of any particular species (sampling effect) because (1) polycultures eventually achieved higher cover than even the best performing monoculture and (2) monocultures rarely differed much, precluding a strong sampling effect. Instead, mechanisms such as facilitation and differential use of microhabitats in a heterogeneous environment likely caused the higher cover in polycultures. Our findings contrast with short-term experiments with other seaweeds but are similar to longer-term experiments with terrestrial plants, suggesting that experimental design and approach, rather than inherent differences between marine and terrestrial ecosystems, underlie contrasting responses among systems. We argue that experiments conducted in the field, and for a greater length of time, allow for the manifestation of a greater number of potential mechanisms of overyielding in diverse communities, increasing the likelihood of observing a strong diversity effect. © 2008 by the Ecological Society of America., Cited By (since 1996):38, Seaweeds, CODEN: ECOLA, ,
Author: Stachowicz, Graham, Bracken, Szoboszlai
Date: 2008-01-01T00:00:00Z

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: Phenotypic plasticity reconciles incongruous molecular and morphological taxonomies: The giant kelp, macrocystis (laminariales, phaeophyceae), is a monospecific genus
Description: The giant kelp genus Macrocystis C. Agardh (Laminariales, Phaeophyceae) is one of the world's most ecologically and economically important seaweed taxa, yet its taxonomy remains uncertain. Although the genus currently contains four accepted species based on variable holdfast and blade morphology [M. pyrifera (L.) C. Agardh, M. integrifolia Bory, M. angustifolia Bory, and M. laevis C. H. Hay], numerous recent studies on Macrocystis interfertility, genetic relatedness, and morphological plasticity all suggest that the genus is monospecific. We reviewed this evidence and present an explanation for the extreme phenotypic plasticity that results in morphological variability within Macrocystis, driven by the effects of environmental factors on early development of macroscopic sporophytes. We propose that the genus be collapsed back to a single species, with nomenclatural priority given to M. pyrifera. © 2009 Phycological Society of America., Cited By (since 1996):18, CODEN: JPYLA
Author: Demes, Graham, Suskiewicz
Date: 2009-01-01T00:00:00Z

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: Abiotic regulation of investment in sexual versus vegetative reproduction in the clonal kelp Laminaria sinclairii (Laminariales, Phaeophyceae),
Description: Clonal kelp taxa may reproduce both sexually and vegetatively resulting in a potential trade-off in the allocation of acquired carbon and nitrogen resources. Such trade-offs may dictate a different response of clonal kelps to varying environmental conditions relative to aclonal kelp taxa. Laboratory temperature and nutrient manipulation experiments demonstrated that investment in sexual and vegetative reproduction in Laminaria sinclairii (Harv. ex Hook. f. et Harv.) Farl., C. L. Anderson et D. C. Eaton was regulated by different abiotic factors. Sorus production (investment in sexual reproduction) and blade growth were significantly higher at 12°C compared to 17°C, regardless of nutrient concentration. Net carbon storage and depletion in rhizomes were observed in the low- and high-temperature treatments, respectively, suggesting that carbon stores were not responsible for increased growth. Rhizome elongation (investment in vegetative reproduction), on the other hand, was significantly higher in 12μM NO3- than in 2μM NO3-, irrespective of temperature. This increase in rhizome growth was concurrent with elevated rhizome percent tissue nitrogen levels also observed in treatments with higher nutrients, again indicating a growth response to treatment independent of previous nutrient stores. These results suggest that regulation of growth and investment in sexual reproduction in L. sinclairii is similar to that in aclonal kelps (i.e., warmer temperatures result in decreased reproductive output). Additionally, depletion of carbon and nitrogen from rhizomes in suboptimal conditions confirms the role of clonal kelp rhizomes in carbon and nutrient storage. © 2011 Phycological Society of America., Seaweeds, CODEN: JPYLA, ,
Author: Demes, Graham
Date: 2011-01-01T00:00:00Z

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: 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