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Daniel C. Reed - One of the best experts on this subject based on the ideXlab platform.
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effects of depth cycling on nutrient uptake and biomass production in the giant kelp Macrocystis pyrifera
Renewable & Sustainable Energy Reviews, 2021Co-Authors: Ignacio A Navarrete, Daniel C. Reed, Diane Y Kim, Cindy Wilcox, David W Ginsburg, Jessica M Dutton, John F Heidelberg, Yubin Raut, Brian Howard WilcoxAbstract:Abstract Seasonal or chronic nutrient limitations in the photic zone limit large-scale cultivation of seaweed (macroalgae) in much of the world's oceans, hindering the development of macroalgae as a biofuel feedstock. One possible solution is to supply nutrients using a diel depth-cycling approach, physically moving the macroalgae between deep nutrient-rich water at night and shallow depths within the photic zone during the day. This study tested the effects of depth-cycling on the growth, morphology, and chemical composition of the giant kelp Macrocystis pyrifera, a target species for renewable biomass production. Giant kelp grown under depth-cycling conditions had an average growth rate of 5% per day and produced four times more biomass (wet weight) than individuals grown in a kelp bed without depth-cycling. Analysis of tissue from the depth-cycled kelp showed elevated levels of protein, lower C:N ratios, and distinct δ15N and δ13C values suggesting that the depth-cycled kelp were not nitrogen-deficient and assimilated nutrients from deep water. Depth-cycled kelp also exhibited smaller and thicker-walled pneumatocysts and larger blades. Overall, this study supports further investigation of depth-cycling as a macroalgal farming strategy.
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patterns and controls of reef scale production of dissolved organic carbon by giant kelp Macrocystis pyrifera
Limnology and Oceanography, 2015Co-Authors: Daniel C. Reed, Andrew Rassweiler, Craig A Carlson, Elisa R Halewood, Clinton J Nelson, Shannon L Harrer, Robert J. MillerAbstract:We investigated the patterns and controls of dissolved organic carbon (DOC) production by the giant kelp (Macrocystis pyrifera) using data from short-term in situ incubations of entire blades and portions of stipes. These data were incorporated into an empirical model of reef-scale net primary production (NPP) at Mohawk Reef in southern California, U.S.A. for an 8-yr period. Rates of DOC release of incubated blades varied unpredictably with time of year, but were significantly related to the irradiance at the sea surface during the incubations. The growth stage, C/N ratio, and epiphyte load of the blades and the temperature of the ocean during the incubations had no discernable effect on rates of DOC release. Blades produced on average 2–3 times more DOC than stipes, and stipes and blades produced on average 30% and 80% more DOC respectively during the day compared to the night. Modeled DOC NPP at the reef scale was on average highest in summer and spring (∼0.5 g C m−2 d−1) and lowest in winter and autumn (∼0.31 g C m−2 d−1), but it varied greatly among years for any given season as large oscillations in standing biomass led to corresponding fluctuations in reef-scale DOC NPP. The fraction of NPP released as DOC was highly variable when examined at the monthly time scale, but became much more stable at seasonal and annual time scales averaging 14% of total NPP.
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Seascape drivers of Macrocystis pyrifera population genetic structure in the northeast Pacific
Molecular ecology, 2015Co-Authors: Mattias L. Johansson, Daniel C. Reed, Peter T. Raimondi, Filipe Alberto, Nelson C. Coelho, Mary A. Young, Patrick T. Drake, Christopher A. Edwards, Kyle C. Cavanaugh, Jorge AssisAbstract:At small spatial and temporal scales, genetic differentiation is largely controlled by constraints on gene flow, while genetic diversity across a species' distribution is shaped on longer temporal and spatial scales. We assess the hypothesis that oceanographic transport and other seascape features explain different scales of genetic structure of giant kelp, Macrocystis pyrifera. We followed a hierarchical approach to perform a microsatellite-based analysis of genetic differentiation in Macrocystis across its distribution in the northeast Pacific. We used seascape genetic approaches to identify large-scale biogeographic population clusters and investigate whether they could be explained by oceanographic transport and other environmental drivers. We then modelled population genetic differentiation within clusters as a function of oceanographic transport and other environmental factors. Five geographic clusters were identified: Alaska/Canada, central California, continental Santa Barbara, California Channel Islands and mainland southern California/Baja California peninsula. The strongest break occurred between central and southern California, with mainland Santa Barbara sites forming a transition zone between the two. Breaks between clusters corresponded approximately to previously identified biogeographic breaks, but were not solely explained by oceanographic transport. An isolation-by-environment (IBE) pattern was observed where the northern and southern Channel Islands clustered together, but not with closer mainland sites, despite the greater distance between them. The strongest environmental association with this IBE pattern was observed with light extinction coefficient, which extends suitable habitat to deeper areas. Within clusters, we found support for previous results showing that oceanographic connectivity plays an important role in the population genetic structure of Macrocystis in the Northern hemisphere.
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trophic versus structural effects of a marine foundation species giant kelp Macrocystis pyrifera
Oecologia, 2015Co-Authors: Robert J. Miller, Henry M Page, Daniel C. ReedAbstract:Foundation species create milieus in which ecosystems evolve, altering species abundances and distribution often to a dramatic degree. Although much descriptive work supports their importance, there remains little definitive information on the mechanisms by which foundation species alter their environment. These mechanisms fall into two basic categories: provision of food or other materials, and modification of the physical environment. Here, we manipulated the abundance of a marine foundation species, the giant kelp Macrocystis pyrifera, in 40 × 40-m plots at Mohawk Reef off Santa Barbara, California and found that its biomass had a strong positive effect on the abundance of bottom-dwelling sessile invertebrates. We examined the carbon (C) stable isotope values of seven species of sessile invertebrates in the treatment plots to test the hypothesis that this positive effect resulted from a nutritional supplement of small suspended particles of kelp detritus, as many studies have posited. We found no evidence from stable isotope analyses to support the hypothesis that kelp detritus is an important food source for sessile suspension-feeding invertebrates. The isotope composition of invertebrates varied with species and season, but was not affected by kelp biomass, with the exception of two species: the tunicate Styela montereyensis, which exhibited a slight enrichment in C stable isotope composition with increasing kelp biomass, and the hydroid Aglaophenia sp., which showed the opposite effect. These results suggest that modification of the physical habitat, rather than nutritional subsidy by kelp detritus, likely accounts for increased abundance of sessile invertebrates within giant kelp forests.
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The importance of progressive senescence in the biomass dynamics of giant kelp (Macrocystis pyrifera)
Ecology, 2013Co-Authors: Gabriel E. Rodriguez, Daniel C. Reed, Andrew Rassweiler, Sally J. HolbrookAbstract:Temporal variation in primary producer biomass has profound effects on the structure and function of the surrounding ecological community. The giant kelp (Macrocystis pyrifera) exhibits strong intra-annual variation in biomass density, which is better explained by the demographic rates of fronds than by those of whole plants. To better understand the processes controlling the dynamics of giant kelp fronds we collected monthly time-series data of frond initiation and survival. These data were used to determine how frond loss and frond initiation rates were predicted by factors thought to affect the growth and survival of Macrocystis, including external environmental factors (i.e., wave height, day length, temperature, nutrient concentration, and neighborhood density) and intrinsic biological characteristics (i.e., frond age, plant size, and nutritional status). Our results revealed that frond dynamics were better explained by intrinsic biological processes rather than external environmental factors. A metric of frond age structure that incorporated progressive senescence was the best predictor of frond loss rate, accounting for 58% of the explained variation in frond loss. A similar analysis revealed that frond age structure was also the single best predictor of frond initiation rate, accounting for 46% of the explained variation. To further examine the importance of senescence in biomass dynamics, we used frond age-dependent mortality and frond initiation rates to predict biomass in subsequent months and found that the model explained 73% of the observed variation in biomass at our sites. Vegetation dynamics of many species including giant kelp are often considered largely in the context of external controls on resource availability and physical disturbance. Our results indicate that investigations of the processes controlling vegetation dynamics may benefit greatly from the inclusion of intrinsic biological factors such as age-dependent mortality and growth, which can outweigh the effects of external forcing in accounting for fluctuations in vegetation biomass.
Alejandro H Buschmann - One of the best experts on this subject based on the ideXlab platform.
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varying reproductive success under ocean warming and acidification across giant kelp Macrocystis pyrifera populations
Journal of Experimental Marine Biology and Ecology, 2020Co-Authors: Carolina Camus, Alejandro H Buschmann, Jordan A Hollarsmith, Edwin D GrosholzAbstract:Abstract Understanding how climate change may influence ecosystems depends substantially on its effects on foundation species, such as the ecologically important giant kelp (Macrocystis pyrifera). Despite its broad distribution along strong temperature and pH gradients and strong barriers to dispersal, the potential for local adaptation to climate change variables among kelp populations remains poorly understood. We assessed this potential by exposing giant kelp early life stages from genetically disparate populations in Chile and California to current and projected temperature and pH levels in common garden experiments. We observed high resistance at the haploid life stage to elevated temperatures with developmental failure appearing at the egg and sporophyte production stages among Chilean and high-latitude California populations, suggesting a greater vulnerability to climate- or ENSO-driven warming events. Additionally, populations that experience low pH events via strong upwelling, internal waves, or estuarine processes, produced more eggs per female under experimental low-pH conditions, which could increase fertilization success. These results enhance our ability to predict population extinctions and ecosystem range shifts under projected declines in ocean pH and increases in ocean temperature.
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revisiting the economic profitability of giant kelp Macrocystis pyrifera ochrophyta cultivation in chile
Aquaculture, 2019Co-Authors: Carolina Camus, Javier Infante, Alejandro H BuschmannAbstract:Abstract The demand for seaweed biomass for hydrocolloid industries and novel products for the food, pharmaceutical, cosmetics and agro-industry has been steadily increasing during the last decade. This trend is expected to continue into the future as new uses are discover and the ever-increasing human population needs for healthy products and clean energy expand beyond land-based resources. Seaweed farming still faces constraints for its development and one of them is its economic profitability as in general the seaweed biomass has a rather low value with few exceptions of some species used for human consumption. Therefore, there is a need to increase production of seaweed biomass, but there is still a lack of realistic economic assessments that determine the economic potentiality of a seaweed farming project to attract investors. This article reports an economic model, fed with data of a pre-commercial Macrocystis pyrifera 21-ha pilot farm installed in southern Chile. The economic sensitivity analysis revealed that cultivation of M. pyrifera in southern Chile is profitable in a 10-ha cultivation system when the market price is at least US$ 87 wet t−1 and yields are kept at a minimum of 12.4 kg m−1. We discuss the potential that seaweed cultivation has in Chile and we agree with previous studies that value, productivity and the farming model used are key factors for the economic success of seaweed farming.
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Macrocystis pyrifera aquafarming production optimization of rope seeded juvenile sporophytes
Aquaculture, 2017Co-Authors: Carolina Camus, Alejandro H BuschmannAbstract:Abstract The use of kelp in different human activities has increased over recent decades and this demand is increasing the demand for cost-effective farming technologies. In the case of the giant kelp (Macrocystis pyrifera) there is a large accumulation of knowledge concerning the relevant information required for aquafarming that allowed the installation of a 20 ha pilot culture farm 5 years ago in southern Chile. However, this experience indicated that to achieve a production level above 200 tons per hectare per year it is necessary to optimize all the protocols starting from the hatchery level through to the growing phase in order to be cost effective. In this study we present information on optimizing the hatchery phase of M. pyrifera culture. The results show that it is possible to obtain 4 to 5 mm long M. pyrifera juvenile sporophytes attached to seeded rope in less than 45 days. To obtain this result, temperature should be 12 °C with a photon irradiance of 12 μmol m− 2 s− 1 and a photoperiod of 16:8, L:D. In addition, macro and micronutrient concentrations should be maintained as the traditional Provasoli culture medium indicates, and with aeration of 414 L h− 1 to maintain water movement in the culture system. Statement of relevance Commercially hatchery kelp farming protocol development is presented.
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scaling up bioethanol production from the farmed brown macroalga Macrocystis pyrifera in chile
Biofuels Bioproducts and Biorefining, 2016Co-Authors: Carolina Camus, Paola Ballerino, Rocio Delgado, Alvaro Oliveranappa, Carmen Leyton, Alejandro H BuschmannAbstract:Interest in third-generation biomass such as macroalgae has increased due to their high biomass yield, absence of lignin in their tissues, lower competition for land and fresh water, no fertilization requirements, and efficient CO2 capture in coastal ecosystems. However, several challenges still exist in the development of cost-effective technologies for processing large amounts of macroalgae. Recently, genetically modified micro-organisms able to convert brown macroalgae carbohydrates into bioethanol were developed, but still no attempt to scale up production has been proposed. Based on a giant kelp (Macrocystis pyrifera) farming and bioethanol production program carried out in Chile, we were able to test and adapt this technology as a first attempt to scale up this process using a 75 L fermentation of genetically modified Escherichia coli. Laboratory fermentation tests results showed that although biomass growth and yield are not greatly affected by the alginate:mannitol ratio, ethanol yield showed a clear maximum around a 5:8 alginate:mannitol ratio. In M. pyrifera, a much greater proportion of alginate and lower mannitol abundance is found. In order to make the most of the carbohydrates available for fermentation, we developed a four-stage process model for scaling up, including acid leaching, depolymerization, saccharification, and fermentation steps. Using this process, we obtained 0.213 Kg ethanol Kg−1 dry macroalgae, equivalent to 9.6 m3 of ethanol hectare−1 year−1, reaching 64% of the maximum theoretical ethanol yield. We propose strategies to increase this yield, including synthetic biology pathway engineering approaches and process optimization targets. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd
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the status of kelp exploitation and marine agronomy with emphasis on Macrocystis pyrifera in chile
Advances in Botanical Research, 2014Co-Authors: Alejandro H Buschmann, Carolina Camus, Maria C Hernandezgonzalez, Julio A Vasquez, Steven Prescott, Philippe Potin, Sylvain Faugeron, Javier Infante, Alfonso Gutierrez, Daniel VarelaAbstract:Kelp cultivation started in Japan, China and Korea, mainly for human consumption; new applications are still expanding. In Chile, three ‘wild’ Lessonia species and Macrocystis pyrifera are under a strong and increasing pressure of exploitation mainly for alginate production and as a source of feed for abalone. Regulatory restrictions for kelp exploitation and the increased demand for biomass provided a positive environment for the installation of a kelp farming industry. Pilot-production studies demonstrated that 200 tonnes (fresh)/ha/year can be achieved and genetic diversity and breeding studies suggested that this volume could be increased. Kelp disease research is a necessary condition for securing the future development of this industry, as are environmental studies on the impacts of large-scale aquaculture. Beyond the positive bioremediation, ecosystem service effects that kelp farming can provide, especially in a region such as in southern Chile, where intensive salmon and mussel cultivation occurs. Life Cycle Assessment suggests that the energy returns on investment in kelp farming are positive, but more detailed data are still required.
Matthew S. Edwards - One of the best experts on this subject based on the ideXlab platform.
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elevated pco2 is less detrimental than increased temperature to early development of the giant kelp Macrocystis pyrifera phaeophyceae laminariales
Phycologia, 2017Co-Authors: Priya Shukla, Matthew S. EdwardsAbstract:Abstract: Global climate change is increasing ocean temperature and partial pressure of CO2 (pCO2) in coastal and marine ecosystems. Research in this field has largely focused on how limited CO32− availability and low pH adversely affect early development of calcifying organisms, but noncalcareous organisms are comparatively understudied despite their prevalence in many coastal communities. We investigated how present-day and future levels of ocean temperature (12°C vs 15°C, respectively) and pCO2 (400 μatm vs 1500 μatm, respectively) influence successful germling production, gametophyte survival, growth, and sex ratio, and embryonic sporophyte production and growth in the habitat-forming kelp Macrocystis pyrifera over a 15-wk period in San Diego, California, USA. Our results indicate that relative to present-day conditions, successful germling production was reduced fourfold under elevated temperature alone, and fivefold under combined elevated temperature and pCO2 (i.e. “future conditions”). Similarly, ...
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Abiotic influences on bicarbonate use in the giant kelp, Macrocystis pyrifera, in the Monterey Bay.
Journal of phycology, 2016Co-Authors: Sarah Tepler Drobnitch, Kerry J. Nickols, Matthew S. EdwardsAbstract:In the Monterey Bay region of central California, the giant kelp Macrocystis pyrifera experiences broad fluctuations in wave forces, temperature, light availability, nutrient availability, and seawater carbonate chemistry, all of which may impact their productivity. In particular, current velocities and light intensity may strongly regulate the supply and demand of inorganic carbon (Ci) as substrates for photosynthesis. Macrocystis pyrifera can acquire and utilize both CO2 and bicarbonate (HCO3- ) as Ci substrates for photosynthesis and growth. Given the variability in carbon delivery (due to current velocities and varying [DIC]) and demand (in the form of saturating irradiance), we hypothesized that the proportion of CO2 and bicarbonate utilized is not constant for M. pyrifera, but a variable function of their fluctuating environment. We further hypothesized that populations acclimated to different wave exposure and irradiance habitats would display different patterns of bicarbonate uptake. To test these hypotheses, we carried out oxygen evolution trials in the laboratory to measure the proportion of bicarbonate utilized by M. pyrifera via external CA under an orthogonal cross of velocity, irradiance, and acclimation treatments. Our Monterey Bay populations of M. pyrifera exhibited proportionally higher external bicarbonate utilization in high irradiance and high flow velocity conditions than in sub-saturating irradiance or low flow velocity conditions. However, there was no significant difference in proportional bicarbonate use between deep blades and canopy blades, nor between individuals from wave-exposed versus wave-protected sites. This study contributes a new field-oriented perspective on the abiotic controls of carbon utilization physiology in macroalgae.
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effects of climate change on the physiology of giant kelp Macrocystis pyrifera and grazing by purple urchin strongylocentrotus purpuratus
Algae, 2014Co-Authors: Matthew B Brown, Matthew S. Edwards, Kwang Young KimAbstract:Copyright © 2014 The Korean Society of Phycology 203 http://e-algae.kr pISSN: 1226-2617 eISSN: 2093-0860 Effects of climate change on the physiology of giant kelp, Macrocystis pyrifera, and grazing by purple urchin, Strongylocentrotus purpuratus Matthew B. Brown*, Matthew S. Edwards and Kwang Young Kim Department of Biology, San Diego State University, San Diego, CA 92182, USA Department of Oceanography, Chonnam National University, Gwangju 500-757, Korea
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role of nutrient fluctuations and delayed development in gametophyte reproduction by Macrocystis pyrifera phaeophyceae in southern california1
Journal of Phycology, 2010Co-Authors: Laura T Carney, Matthew S. EdwardsAbstract:Organisms occurring in environments subject to severe disturbance and/or periods of poor environmental quality that result in severe adult mortality can survive these periods by relying on alternate life stages that delay their development in a resistant state until conditions improve. In the northeast Pacific, the forest-forming giant kelp Macrocystis pyrifera (L.) C. Agardh periodically experiences widespread adult mortality during extended periods of extremely low nutrients and high temperatures, such as those associated with El Nino. Recovery following these periods is hypothesized to occur from microscopic life stages that delay their development until the return of favorable conditions. In the laboratory, we experimentally examined the environmental conditions responsible for regulating delayed development of the microscopic stages of M. pyrifera from Southern California, USA. Nutrients controlled the delay and resumption of gametophyte growth and reproduction, perhaps linked to the large fluctuations in nutrients occurring seasonally and interannually in this region. Although growth of gametophytes proceeded in the virtual absence of nitrate, both nitrate and other trace nutrients were necessary for gametogenesis. Upon exposure to elevated nutrients, delayed gametophytes produced sporophytes more quickly (5–20 d) and at smaller sizes (10–200 μm) than gametophytes that had never been delayed (18–80 d, 80–400 μm, respectively), reducing negative density-dependent effects. This finding demonstrates that delayed gametophytes of M. pyrifera rapidly utilize increased resources to consistently produce sporophytes. Further work is needed to assess their potential role in population recovery following periods of poor environmental quality.
Catriona L Hurd - One of the best experts on this subject based on the ideXlab platform.
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stress due to low nitrate availability reduces the biochemical acclimation potential of the giant kelp Macrocystis pyrifera to high temperature
Algal Research-Biomass Biofuels and Bioproducts, 2020Co-Authors: Matthias Schmid, Pablo P Leal, Pamela A Fernandez, Juan Diego Gaitanespitia, Patti Virtue, Andrew T Revill, Peter D Nichols, Catriona L HurdAbstract:The performance and survival of macroalgae is largely determined by their ability to adjust to varying environmental conditions. In this study, we investigated the short-term response of the giant kelp Macrocystis pyrifera to varying temperatures (6, 17 and 24 °C) and low and high nitrate conditions (5 μM and 80 μM nitrate) on lipid and fatty acid levels. Results revealed that M. pyrifera was able to rapidly adjust to varying temperatures by changing the saturation level of the fatty acid composition at low and high nitrate conditions. On a lipid level, we observed interactive effects of temperature and nutrient conditions. Under high nitrate conditions, M. pyrifera maintained the same lipid profile. However, under low nitrate and high temperature conditions, an increase in free fatty acids (FFA) was observed, indicative of lipid degeneration at high temperatures. Results show that low nitrogen concentrations can magnify the negative effects of short term temperature stress in the giant kelp M. pyrifera. Our findings indicate that under rapid warming events, local nitrate availability might be a decisive factor for the acclimation potential of M. pyrifera.
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seawater ph and not inorganic nitrogen source affects ph at the blade surface of Macrocystis pyrifera implications for responses of the giant kelp to future oceanic conditions
Physiologia Plantarum, 2017Co-Authors: Pamela A Fernandez, Pablo P Leal, Michael Y Roleda, Catriona L HurdAbstract:Ocean acidification (OA), the ongoing decline in seawater pH, is predicted to have wide-ranging effects on marine organisms and ecosystems. For seaweeds, the pH at the thallus surface, within the diffusion boundary layer (DBL), is one of the factors controlling their response to OA. Surface pH is controlled by both the pH of the bulk seawater and by the seaweeds' metabolism: photosynthesis and respiration increase and decrease pH within the DBL (pHDBL ), respectively. However, other metabolic processes, especially the uptake of inorganic nitrogen (Ni ; NO3- and NH4+ ) may also affect the pHDBL . Using Macrocystis pyrifera, we hypothesized that (1) NO3- uptake will increase the pHDBL , whereas NH4+ uptake will decrease it, (2) if NO3- is cotransported with H+ , increases in pHDBL would be greater under an OA treatment (pH = 7.65) than under an ambient treatment (pH = 8.00), and (3) decreases in pHDBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H+ ] might affect the strength of the diffusion gradient. Overall, Ni source did not affect the pHDBL . However, increases in pHDBL were greater at pH 7.65 than at pH 8.00. CO2 uptake was higher at pH 7.65 than at pH 8.00, whereas HCO3- uptake was unaffected by pH. Photosynthesis and respiration control pHDBL rather than Ni uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and Ni uptake will not be affected by a reduced pH.
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exposure to chronic and high dissolved copper concentrations impedes meiospore development of the kelps Macrocystis pyrifera and undaria pinnatifida ochrophyta
Phycologia, 2016Co-Authors: Pablo P Leal, Catriona L Hurd, Sylvia G Sander, Birthe Kortner, Michael Y RoledaAbstract:Abstract: Copper in low natural concentrations is essential for cell metabolism but in excess it becomes extremely toxic to aquatic life, including to the early life stages of marine macroalgae. This work determined the effects of copper exposure on meiospore development of two kelp species, the native Macrocystis pyrifera and invasive Undaria pinnatifida. After settlement, meiospores were exposed to nominal copper concentrations of control (no added copper), 100, 200, 300 and 400 μg L−1 Cu for 9 days. Inductively coupled plasma mass spectrometry of total dissolved copper (CuT) concentrations in the blanks showed that nominal copper concentrations were reduced to 54, 91, 131 and 171 μg L−1 CuT, respectively, indicating that > 50% of the dissolved copper was adsorbed onto the culture vessel walls. In the media with meiospores, the dissolved copper concentrations decreased to 39, 86, 97 and 148 μg L−1 CuT in M. pyrifera and to 39, 65, 97 and 146 μg L−1 CuT in U. pinnatifida, indicating that 6–15% of the dis...
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meiospores produced in sori of nonsporophyllous laminae of Macrocystis pyrifera laminariales phaeophyceae may enhance reproductive output
Journal of Phycology, 2014Co-Authors: Pablo P Leal, Catriona L Hurd, Michael Y RoledaAbstract:Different lamina of Macrocystis pyrifera sporophytes (i.e., sporophylls, pneumatocyst-bearing blades, and apical scimitars) in a wave-sheltered site were found to be fertile. We quantified their sorus surface area, reproductive output (number of spores released) and the viability of released spores (germination rate). Sorus area was greatest on the sporophylls, with sporangia developing on >57% of the total area and smallest on the pneumatocyst-bearing blades with 21% of the total area bearing sporangia. The apical scimitar released the greatest number of meiospores (cells · mL−1 · cm−2) and the sporophylls the least. Meiospores produced from all types of fertile laminae were equally viable. This reproductive plasticity may enhance reproductive output, and contribute to short and long-distance spore dispersal and the cryptic gametophyte propagule bank for the next generation of sporophytes.
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flow induced morphological variations affect diffusion boundary layer thickness of Macrocystis pyrifera heterokontophyta laminariales 1
Journal of Phycology, 2011Co-Authors: Catriona L Hurd, Conrad A PilditchAbstract:In slow mainstream flows (<4-6 cm · s(-1) ), the transport of dissolved nutrients to seaweed blade surfaces is reduced due to the formation of thicker diffusion boundary layers (DBLs). The blade morphology of Macrocystis pyrifera (L.) C. Agardh varies with the hydrodynamic environment in which it grows; wave-exposed blades are narrow and thick with small surface corrugations (1 mm tall), whereas wave-sheltered blades are wider and thinner with large (2-5 cm) edge undulations. Within the surface corrugations of wave-exposed blades, the DBL thickness, measured using an O2 micro-optode, ranged from 0.67 to 0.80 mm and did not vary with mainstream velocities between 0.8 and 4.5 cm · s(-1) . At the corrugation apex, DBL thickness decreased with increasing seawater velocity, from 0.4 mm at 0.8 cm · s(-1) to being undetectable at 4.5 cm · s(-1) . Results show how the wave-exposed blades trap fluid within the corrugations at their surface. For wave-sheltered blades at 0.8 cm · s(-1) , a DBL thickness of 0.73 ± 0.31 mm within the edge undulation was 10-fold greater than at the undulation apex, while at 2.1 cm · s(-1) , DBL thicknesses were similar at <0.07 mm. Relative turbulence intensity was measured using an acoustic Doppler velocimeter (ADV), and overall, there was little evidence to support our hypothesis that the edge undulations of wave-sheltered blades increased turbulence intensity compared to wave-exposed blades. We discuss the positive and negative effects of thick DBLs at seaweed surfaces.
Mark A. Brzezinski - One of the best experts on this subject based on the ideXlab platform.
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Partitioning of primary production among giant kelp (Macrocystis pyrifera), understory macroalgae, and phytoplankton on a temperate reef
Limnology and Oceanography, 2010Co-Authors: Robert J. Miller, Daniel C. Reed, Mark A. BrzezinskiAbstract:We experimentally investigated the response of phytoplankton and understory macroalgae to canopies of giant kelp, Macrocystis pyrifera, by following changes in their biomass and net primary production over 17 months in 600-m2 plots where giant kelp was continually removed or left intact and allowed to vary naturally. Production by phytoplankton was two times greater and understory algae five times greater where Macrocystis was removed relative to the intact forest. Understory biomass, but not phytoplankton biomass, was suppressed inside the forest, leading to a higher magnitude of effect on net primary production (NPP) by understory relative to phytoplankton. Following a natural decline of the Macrocystis canopy by winter storms, understory macroalgae and phytoplankton increased production in the Macrocystis control plot. This response was delayed for both groups, with phytoplankton production increasing in spring and understory increasing later during summer. The longer delay for understory macroalgae was likely due to restrictions in the timing of macroalgal recruitment and their slower growth rates compared with phytoplankton and with increased competition for light resulting from greater light absorption by the spring phytoplankton bloom. Surprisingly, total ecosystem production that included NPP by Macrocystis, phytoplankton, and understory algae did not differ between the Macrocystis control and removal plots for much of the study. NPP by understory algae, which comprised the bulk of the ecosystem NPP in the Macrocystis removal plot, can compensate to varying degrees for the loss of Macrocystis production following its removal by winter storms.
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net primary production growth and standing crop of Macrocystis pyrifera in southern california
Ecology, 2008Co-Authors: Andrew Rassweiler, Daniel C. Reed, Richard C Zimmerman, Katie K Arkema, Mark A. BrzezinskiAbstract:Marine macroalgae are believed to be among the most productive autotrophs in the world. However, relatively little information exists about spatial and temporal variation in net primary production (NPP) by these organisms. The data presented here are being collected to investigate patterns and causes of variation in NPP by the giant kelp, Macrocystis pyrifera, which is believed to be one of the fastest growing autotrophs on earth. The standing crop and loss rates of M. pyrifera have been measured monthly in permanent plots at three sites in the Santa Barbara Channel, USA. Collection of these data began in June 2002 and is ongoing. Seasonal estimates of NPP and growth rate are made by combining the field data with a model of kelp dynamics. The purpose of this Data Paper is to make available a time series of M. pyrifera NPP, growth, and standing crop that is appropriate for examining seasonal and interannual patterns across multiple sites. Data on plant density in each plot and censuses of fronds on tagged plants at each site are also made available here. NPP, mass-specific growth rate, and standing crop are presented in four different metrics (wet mass, dry mass, carbon mass, and nitrogen mass) to facilitate comparisons with previous studies of M. pyrifera and with NPP measured in other ecosystems. Analyses of these data reveal seasonal cycles in growth and standing crop as well as substantial differences in M. pyrifera NPP among sites and years.
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physical pathways and utilization of nitrate supply to the giant kelp Macrocystis pyrifera
Limnology and Oceanography, 2008Co-Authors: Jonathan P Fram, Daniel C. Reed, Mark A. Brzezinski, Brian Gaylord, Hannah L Stewart, Susan L Williams, Sally MacintyreAbstract:To determine the relative importance of different sources of nitrate to the annual nitrogen needs of the giant kelp Macrocystis pyrifera, we measured ambient nitrate concentrations at a kelp forest for 13 months and characterized nitrate delivery using water column thermal structure and flow data collected in the forest and at its offshore edge. The forest’s monthly nitrate supply varied by a factor of 50, while measured net nitrogen acquisition varied only fivefold. Maximum net nitrogen acquisition rates for fronds in the forest interior were 0.18 mmol N g21 month21 during spring upwelling in 2005 and declined fourfold during autumn until upwelling resumed the following year. Modeled gross nitrogen uptake with consideration of Michaelis–Menten kinetics for nitrate and mass transfer limitation was higher than observed net acquisition except during the warm stratified summer and autumn months, when net acquisition exceeded modeled gross uptake. This shortfall indicates that the kelp forest received over half its nitrogen from sources other than nitrate such as ammonium from epibionts. Most of the nitrate in the forest was delivered as a result of upwelling-favorable winds and convection. Internal waves and local streams contributed ,9% of the nitrate delivered to the forest on an annual basis and 20% during stratified periods. Kelp used less than 5% of the nitrate supplied to the forest. Nitrate delivery to this modest sized kelp forest was roughly equivalent between alongshore (45%) and cross-shore flows (55%), which distinguishes it from large kelp forests in which cross-shore flows dominate exchange.
