Search results

Title: Top-down impact through a bottom-up mechanism. In situ effects of limpet grazing on growth, light requirements and survival of the eelgrass Zostera marina,
Description: Temporal changes in abundance, size, productivity, resource allocation and light requirements of a subtidal eelgrass (Zostera marina L.) population were followed for 2 yr after the September 1993 appearance of a previously rare oval form of the commensal limpet Tectura depicta (Berry) in Monterey Bay, California, USA. By exclusively targeting the epidermis, limpet grazing impaired photosynthetic performance but left respiratory demand, meristematic growth and more than 90% of the leaf biomass intact. The resulting low P:R ratios of grazed plants raised the light requirements for the maintenance of positive carbon balance almost 2-fold relative to healthy ungrazed plants and prevented the summertime accumulation of internal carbon reserves. Shoot density in this once-continuously vegetated 30 ha meadow declined from more than 50 shoots m-2 (2230 g fresh wt [FW] m-2) to sparse patches supporting an average of 16 shoots m-2 (380 g FW m-2). More than 50% of the continuously vegetated meadow was converted to bare sand despite ambient light availability and water temperatures that were favorable for growth of healthy, ungrazed plants. Plant size declined by 50 % and internal sugar reserves declined more than 4-fold within 6 mo after the appearance of T. depicta. Plant losses were most extensive during winter, when internal carbon reserves were minimal. The dramatic decline in eelgrass vigor and abundance reported here, despite a physical environment that was favorable for healthy eelgrass survival, illustrates the amplification of top-down control by this relatively inconspicuous limpet through a feeding mechanism that specifically impairs photosynthesis, a bottom-up process., Cited By (since 1996):11, Seaweeds, CODEN: MESED, ,
Author: Zimmerman, Steller, Kohrs, Alberte
Date: 2001-01-01T00:00:00Z

Title: Effect of storms on photosynthesis, carbohydrate content and survival of eelgrass populations from a coastal lagoon and the adjacent open ocean,
Description: Annual variations in density, morphology, pigment levels, carbohydrate levels and photosynthetic characteristics of Zostera marina L. (eelgrass) from a coastal lagoon and from an unprotected area in the open coast were compared to understand the environmental regulation of this species growing near the southern limit of its distribution in the eastern Pacific. From January to April of 1997, light attenuation coefficients at the lagoon and the open coast increased six-fold as a result of sediment resuspension caused by storms in the area. During the storms, in situ irradiance was reduced two-fold at the lagoon. Irradiance values at the open coast, however, were reduced to nearly zero for >3 weeks, promoting the disappearance of the open coast population. At the open coast, eelgrass shoots died after sugar and starch content in the leaves decreased by approximately 85% after 3 weeks of light limitation. The re-appearance of eelgrass seedlings at the open coast coincided with the end of the winter storms in the area and decreasing water column turbidity. Maximum photosynthesis values of eelgrass from the open coast were two-fold greater than those from lagoon plants, except during March-June when seeds germinated at the open coast. Similarly, survival and leaf carbohydrate content of eelgrass from both sites decreased by >90% when incubated for 3 weeks in darkness. Collectively, these results indicate that the disappearance of eelgrass at the open coast is regulated by irradiance and not by an endogenous cycle. Although eelgrass can succeed in the open coast given sufficient light during the year, the accumulation and mobilization of carbon reserves appear to play a key role in the dynamics of eelgrass survival in temporally variable environments. © 2002 Elsevier Science B.V. All rights reserved., Cited By (since 1996):27, Seaweeds, CODEN: AQBOD, ,
Author: Cabello-Pasini, Lara-Turrent, Zimmerman
Date: 2002-01-01T00:00:00Z

Title: Coralline algal rhodoliths enhance larval settlement and early growth of the pacific calico scallop Argopecten ventricosus
Description: The features of heterogeneous rhodolith beds (maerl) that contribute to their role as nursery habitats in coastal ecosystems are poorly understood. Rhodoliths are branched, unattached coralline algae that form complex benthic substrates and support diverse communities worldwide. Pacific calico scallops Argopecten ventricosus = circularis (Sowerby II, 1842) occur in high densities in rhodolith beds in the Gulf of California, México. In this study, we found that Lithophyllum margaritae rhodoliths enhanced larval scallop settlement and early post-settlement growth, and examined the settlement cues responsible. In both field and laboratory experiments, larval settlement was significantly higher on (1) rhodolith derived vs. non-coralline sedimentary substrates, (2) living vs. nonliving coralline surfaces, and (3) substrates with higher (whole, branching rhodoliths) vs. lower (rhodolith fragments or sediment) structural complexity. In the field, larval settlement (mean ± SE) onto rhodoliths was 30 to 35 times higher on live rhodoliths (55.0 ± 13.4 and 84.4 ± 8.8 larvae cm-2) than on non-carbonate sediment (1.8 ± 0.8 and 2.4 0.9 larvae cm-2) relative to the surrounding rhodolith or sand habitat, respectively. In a laboratory preference experiment, when comparing live vs. dead coralline surfaces respectively, settlement density was 3.3 times greater (55.8 ± 14.6 vs. 17.0 ± 4.9 larvae cm -2) on whole rhodoliths and 7 times greater (24.2 ± 4.7 vs. 3.4 ± 1.3 larvae cm-2) on fragmented rhodoliths. The strong cueing to live coralline surfaces may have resulted from live coralline algal surfaces or surface biofilms. Growth, presented as post-settlement size, was significantly greater in scallops that settled onto whole vs. fragmented rhodolith substrates for both live (246.6 ± 1.9 vs. 238.9 ± 4.4 μm) and dead (244.2 ± 2.8 vs. 234.7 ± 5.6 μm) coralline surfaces. The structural and coralline cues provided by live, intact rhodoliths and their large-grained sediments contribute to the importance of rhodolith beds as nursery habitats by increasing both scallop settlement and postsettlement growth. Protection of living rhodolith habitats can enhance scallop and other invertebrate populations as well as the sustainability of scallop fisheries by enhancing early life stages. © Inter-Research 2009., Cited By (since 1996):10 Seaweeds, CODEN: MESED
Author: Steller, Cáceres-Martínez
Date: 2009-01-01T00:00:00Z

Title: Effects of epiphyte load on optical properties and photosynthetic potential of the seagrasses Thalassia testudinum Banks ex König and Zostera marina L.,
Description: The biomass and optical properties of seagrass leaf epiphytes were measured to evaluate their potential impact on the photosynthetic performance of the seagrasses Thalassia testudinum Banks ex König (turtlegrass) and Zostera marina L. (eelgrass). Turtlegrass was obtained from oligotrophic waters near Lee Stocking Island, Bahamas; eelgrass was collected from a eutrophic environment in Monterey Bay, California. Leaf-epiphyte loads were characterized visually and quantified using measurements of their phospholipid biomass. Light absorption and reflectance of the intact epiphyte layer were determined spectrophotometrically. Turtlegrass epiphytes from the oligotrophic site absorbed a maximum of 36% of incident light in peak chlorophyll absorption bands, whereas higher epiphyte loads on eelgrass from the more eutrophic Monterey Bay absorbed 60% of incident light in peak chlorophyll absorption bands. The combination of intact epiphyte-leaf complexes and spectral measurements enabled us to construct a quantitative relationship between epiphyte biomass and light attenuation, and, by extension, between epiphyte biomass and seagrass photosynthesis. The model yielded a robust, positive relationship between epiphyte biomass and the absorption of photons in photosynthetically important wavelengths, and it generated a strong negative relationship between epiphyte biomass and spectral photosynthesis of their seagrass hosts. Furthermore, the calculations of photosynthesis highlighted the significant differences between PAR and spectral models of photosynthesis, illustrating that the spectral quality of the incident flux must be considered when evaluating the effects of epiphyte load on seagrass leaf photosynthesis. Verification of the model - using direct measurements of photosynthesis and a variety of epiphyte and macrophyte combinations from different locations - is warranted., Cited By (since 1996):34, Seaweeds, CODEN: LIOCA, ,
Author: Drake, Dobbs, Zimmerman
Date: 2003-01-01T00:00:00Z

Title: Effects of zoospore aggregation and substrate rugosity on kelp recruitment success,
Description: Successful kelp recruitment is important for kelp population persistence and associated kelp forest communities. The proximity of settled kelp zoospores is a known requirement for successful kelp recruitment and proximity can be increased as zoospores aggregate. Substrate rugosity can also be an important factor affecting macroalgal settlement and recruitment in wave-swept areas, and may affect kelp recruitment by aggregating zoospores. In this study, kelp zoospores were cultured at different levels of small-scale aggregation and kelp recruitment was quantified. Sporophyte production significantly increased as zoospores became more aggregated indicating that processes that aggregate kelp zoospores have the potential to enhance kelp recruitment. A 13-month field experiment demonstrated differential kelp recruitment onto settlement plates that mimicked surface rugosities of two common rock types within Stillwater Cove, Carmel Bay in central California (Carmelo Formation sandstone and Santa Lucia granodiorite). Significantly more kelp recruited to molds mimicking granodiorite over the yearlong study (granodiorite = 2.7 recruits ± SE 0.50, sandstone = 1.2 recruits ± SE 0.51). There was a significant difference in recruitment between seasons and this variability was due to the fact that spring had the highest average number of kelp recruits per mold. However, the interaction between substrate and season was not significant. This study emphasizes the importance of kelp zoospore aggregation on kelp recruitment and demonstrates that small-scale rugosity affects kelp recruitment. © 2012 Phycological Society of America., Cited By (since 1996):1, Seaweeds, CODEN: JPYLA, ,
Author: Muth
Date: 2012-01-01T00:00:00Z

Title: Comparison of techniques used to count single-celled viable phytoplankton
Description: Four methods commonly used to count phytoplankton were evaluated based upon the precision of concentration estimates: Sedgewick Rafter and membrane filter direct counts, flow cytometry, and flow-based imaging cytometry (FlowCAM). Counting methods were all able to estimate the cell concentrations, categorize cells into size classes, and determine cell viability using fluorescent probes. These criteria are essential to determine whether discharged ballast water complies with international standards that limit the concentration of viable planktonic organisms based on size class. Samples containing unknown concentrations of live and UV-inactivated phytoflagellates (Tetraselmis impellucida) were formulated to have low concentrations (<100 mL -1) of viable phytoplankton. All count methods used chlorophyll a fluorescence to detect cells and SYTOX fluorescence to detect nonviable cells. With the exception of one sample, the methods generated live and nonviable cell counts that were significantly different from each other, although estimates were generally within 100% of the ensemble mean of all subsamples from all methods. Overall, percent coefficient of variation (CV) among sample replicates was lowest in membrane filtration sample replicates, and CVs for all four counting methods were usually lower than 30% (although instances of ~60% were observed). Since all four methods were generally appropriate for monitoring discharged ballast water, ancillary considerations (e.g., ease of analysis, sample processing rate, sample size, etc.) become critical factors for choosing the optimal phytoplankton counting method. © 2011 Springer Science+Business Media B.V. (outside the USA)., Cited By (since 1996):1 Seaweeds, CODEN: JAPPE
Author: Steinberg, First, Lemieux, Drake, Nelson, Kulis, Anderson, Welschmeyer, Herring
Date: 2012-01-01T00:00:00Z

Title: Distribution patterns of benthic microalgal standing stock at McMurdo Sound, Antarctica,
Description: During the austral summer of 1975-76 and winter of 1977 benthic and water column chlorophyll a and phaeopigments were measured at several sites along the east and west sides of McMurdo Sound, Antarctica. Estimates of in situ primary productivity were made at some McMurdo Sound locations. Additionally, water column samples were collected at 5 stations in the Ross Sea during January, 1976. Standing stock data are analyzed to identify seasonal and spatial patterns. Variability in algal standing stock was related to ambient light levels and appeared to be mediated by ice and snow cover whereby the highest algal standing stock was present under high light conditions (low ice and snow cover, shallow water, summer). Differences in published benthic invertebrate densities appear to be closely allied to differences in benthic primary production, and less so to in situ planktonic ice microalgal production. © 1986 Springer-Verlag., Cited By (since 1996):49, Seaweeds, Antarctica, CODEN: POBID, ,
Author: Dayton, Watson, Palmisano, Barry, Oliver, Rivera
Date: 1986-01-01T00:00:00Z

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: Temperature dependence of nitrate reductase activity in marine phytoplankton: Biochemical analysis and ecological implications,
Description: The temperature dependence of NADH:NR activity was examined in several marine phytoplankton species and vascular plants. These species inhabit divergent thermal environments, including the chromophytes Skeletonema costatum (12-15°C), Skeletonema tropicum (18-25°C), Thalassiosira antarctica (-2 to 4°C), and Phaeocystis antarctica (-2 to 4°C), the green alga Dunaliella tertiolecta (14-28°C), and the vascular plants Cucurbita maxima (20-35°C) and Zea mays (20-25°C). Despite the difference in growth habitats, similar temperature response curves were observed among the chromophytic phytoplankton, with temperatures optimal for NR activity being between 10-20°C. In contrast, the chlorophyll b-containing alga and vascular plants exhibited optimal temperatures for NR activity above 30°C. Such dramatic differences in NR thermal characteristics from the two taxonomic groups reflect a divergence in NR structure that may be associated with the evolutionary diversification of chromophytes and chlorophytes. Further, it suggests a potential contribution of the thermal performance of NR to the geographic distributions, seasonal abundance patterns, and species composition of phytoplankton communities. NR partial activities, which assess the individual functions of Mo-pterin and FAD domains, were evaluated on NR purified from S. costatum to determine the possible causes for high temperature (>20°C) inactivation of NR from chromophytes. It was found that the FAD domain and electron transport among redox centers were sensitive to elevated temperatures. S. costatum cells grown at 5, 15, and 25°C exhibited an identical optimal temperature (15°C) for NADH:NR activity, whereas the maximal NR activity and NR protein levels differed and were positively correlated with growth temperature and growth rate. These findings demonstrate that thermal acclimation of NO 3 - reduction capacity is largely at the level of NR protein expression. The consequences of these features on NO 3 - utilization are discussed., Cited By (since 1996):26, Seaweeds, Oceanography, CODEN: JPYLA, ,
Author: Gao, Smith, Alberte
Date: 2000-01-01T00:00:00Z

Title: Community structure of temperate reef fishes in kelp-dominated subtidal habitats of northern Chile,
Description: An important aim of fish ecology is to understand and predict patterns of distribution and abundance in marine communities. Such patterns were examined at four kelp-dominated sites along the northern coast of Chile (19° through 30°S) over 1 year. Fish species richness, diversity and abundance estimates obtained via observational and destructive sampling methods were compared among sites as were habitat and environmental variables that characterised the sites; including sea water temperature below the surface, nutrients, productivity, visibility, density of macroalgae stands, and percentage cover of observed microhabitats (including understorey algae and faunal assemblages). In total, 19 fish species belonging to 14 families were observed from all sites. Species richness and diversity were highest in sites where kelp canopy was composed of two species and where kelp was densest, although only species diversity was significantly different among sites. The sites with high kelp density, in turn, sustained abundant habitat-forming species in the kelp understorey. Principal coordinate analysis indicated that the composition and structure of the fish assemblages varied significantly with depth at all study sites. The depth distribution of fishes was correlated with the arrangement of site-specific biological microhabitats, defined by the algae or invertebrate species that form the microhabitat. Temperature, productivity, and nutrients did not vary consistently across study sites, but did vary within individual sites. We suggest that kelp cover and composition strongly affects the diversity and distribution of fishes at shallow coastal habitats in northern Chile through the availability of microhabitats. © CSIRO 2007., Cited By (since 1996):8 Fish and Fisheries Seaweeds, CODEN: AJMFA, ,
Author: Pérez-Matus, Ferry-Graham, Cea, Vásquez
Date: 2007-01-01T00:00:00Z

Title: Effect of the bat star Asterina miniata (Brandt) on recruitment of the giant kelp Macrocystis pyrifera C. Agardh,
Description: Cited By (since 1996):10, Ecology, Seaweeds, CODEN: JEMBA, The effect of the common bat star, Asterina miniata (Brandt) on recruitment of the giant kelp, Macrocystis pyrifera C. Agardh, was addressed through laboratory grazing experiments, a field experiment, and modeling of feeding behavior. In the laboratory, Asterina miniata significantly decreased the density of sporophytes that developed from 1-wk-old gametophytes as well as the percent cover of 2-, 6-, and 7-wk-old sporophytes. All grazed blades remaining at the end of these experiments subsequently died. Small scale variability in spore settlement and sporophyte development were also evident in the laboratory. Bat star density significantly affected short-term kelp recruitment during a large-scale field experiment. Simple modeling suggested that high densities of Asterina miniata could graze nearly 100% of the bottom over the 90-day experiment. However, visible recruitment was seen in less than 30 days, and over this time, 36% of the substratum was predicted to have remained ungrazed. Macrocystis pyrifera of 1 to 3 cm in length may thus obtain a refuge in size from bat star grazing through rapid growth. These results indicate this generalist grazer can affect giant kelp recruitment but that even under high grazing pressure numerous plants survive. Bat star grazing probably does not contribute to large-scale differences in adult plant density but may contribute to small-scale patterns of dispersion., ,
Author: Leonard
Date: 1994-01-01T00:00:00Z

Title: Effect of temperature on photosynthesis, growth and calcification rates of the free-living coralline alga Lithophyllum margaritae
Description: Rhodolith beds are the dominant submerged calcifying aquatic vegetation in some coastal marine environments worldwide but flew quantitative data are available regarding their physiology. In the Gulf of California (Mexico), Lithophyllum margaritae (Rhodophyta, Corallinaceae) is the most abundant nongeniculate, rhodolith-forming coralline species. Over their gulf-wide distribution, rhodolidis are exposed to a wide range of seasonal temperatures (∼8-32°C). The effect of changes in temperature on the photosynthetic and calcification rates of this species is unknown. We therefore evaluated the effect of temperature (10-30°C) on the photosynthetic and calcification rates of L. margaritae rhodoliths in the lab and examined the effect of seasonal changes in temperature on growth rates in the field. Photosynthetic rates were evaluated polarographically and calcification rates were evaluated in the lab using both the buoyant weight technique and total alkalinity method, and in the field through alizarin staining. To the best of our knowledge, this is the first time that these three methods are used simultaneously to evaluate growth rates in coralline algae. Photosynthetic, calcification and growth rates showed wide fluctuations as a result of laboratory or field temperature. Photosynthetic (Pmax) and respiratory rates both increased five-fold as incubation temperature increased to 25-30°C. Similarly, calcification rates in the lab and growth rates in the field increased with higher temperatures. The lab data suggest that rhodolith growth is seasonally regulated by seawater temperature. The buoyant weight and total alkalinity techniques for determining calcification rate were comparable at low temperatures, but variability increased with temperature and this will be examined in further studies. Field growth rates, presented as apical tip extension, were significantly higher in summer (5.02 ± 1.16 mm yr-1) than in winter (0.83 ± 0.16 mm yr-1), supporting the lab results. The strong effects of temperature on photosynthetic, calcification and growth rates of Lithophyllum margaritae in the Gulf of California suggest that changes in sea surface temperature directly regulate bed production., Cited By (since 1996):13, Seaweeds, From abbreviated title field: Efecto de la temperature sobre las tasas de fotosíntesis, crecimiento y calcificación del alga coralina de vida libre Lithophyllum margaritae
Author: Steller, Hernández-Ayón, Riosmena-Rodriguez, Cabello-Pasini
Date: 2007-01-01T00:00:00Z

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