bluuebunny/crossref_metadata_2025_split huggingface dataset:
Current Loads of Coarse Woody Debris on Southeastern Australian Floodplains: Evaluation of Change and Implications for Restoration
Authors: MacNally Ralph , Parkinson Amber , Horrocks Gregory , Young Matthew 
Published: March 2003

AbstractWe evaluated the status of coarse woody debris (CWD, fallen wood) on floodplains of the southern Murray‐Darling basin of southeastern Australia. The floodplains are dominated floristically by the river red gum Eucalyptus camaldulensis. Aerial survey techniques were used to estimate the amounts of woody debris within 200 m of the channels along 2,442 km of 11 rivers of the system, including the Murray and Darling Rivers and the Darling Anabranch. Aerially based indices were converted into wood volumes by using ground‐truthing at a selection of sites; there was a strong correlation between index values and measured wood volume densities. For thickly forested sites such as Barmah, Gunbower Island, and the Ovens floodplains, the aerial method was not useful, so ground measurements at randomly positioned sites within the forests were used. Volumes were translated into mass by using conversion factors drawn from the literature. We estimated that total tonnage on approximately 221,000 ha of floodplain forests was 4.175 ± 0.579 × 106 tonne. In the larger forested blocks (>7,000 ha), mean wood densities ranged between approximately 12 tonne/ha on the lower Goulburn up to approximately 24 tonne/ha at Barmah State Forest. The area‐weighted mean for the entire area was approximately 19 tonne/ha. A main purpose of the research was to place these figures into an historical perspective to evaluate implications for restoration. A thorough search of historical documentation revealed that there are no extant data upon which to estimate pre‐European settlement levels. We used information from an apparently undisturbed “unmanaged” site in the Millewa forests of southern New South Wales as a basis. Wood density there corresponded to a mean figure of 125 tonne/ha wood‐mass density. By using this figure we estimate that CWD levels on the southern Murray‐Darling basin may be of the order of 15% of pre‐European settlement levels. Full restoration of the 221,000 ha surveyed would require 23.5 ± 0.579 × 106 tonne, which is equivalent to about 600,000 mature (1 m diameter at breast height) river red gum trees or the amount of timber derived from clear felling about 115,000 ha of river red gum forest at current stocking levels. We discuss the implications of this massive deficit and possible short‐ and long‐term solutions.
Early Responses of Fishes and Crustaceans to Restoration of a Tidally Restricted New England Salt Marsh
Authors: Raposa Kenneth 
Published: March 2003

AbstractNekton (fishes and decapod crustaceans) is an abundant and productive faunal component of salt marshes, yet nekton responses to tidal manipulations of New England salt marshes remain unclear. This study examined nekton use of a tidally restricted salt marsh in Narragansett, Rhode Island relative to an unrestricted marsh during summer. In addition, a before‐after‐control‐impact design was used to examine early responses of nekton to the reintroduction of natural tidal flushing. Species richness and densities of Cyprinodon variegatus, Lucania parva, Menidia beryllina, and Palaemonetes pugio were higher in the restricted marsh compared with the unrestricted marsh. The unrestricted marsh supported higher densities of Menidia menidia and Fundulus majalis. Mean lengths of Carcinus maenas and P. pugio were greater in the restricted marsh. Tidal restoration resulted in increased tidal flushing, salinity, and water depth in the restricted marsh. Densities of Fundulus heteroclitus, F. majalis, and Callinectes sapidus were higher after 2 years of restoration. Density of L. parva decreased after restoration, probably in response to a loss of macroalgal habitat. Species richness also decreased after 2 years, from 20.9 species when the marsh was restricted to 13.0 species. Total nekton density did not change with restoration, but shifts in community composition were evident. In this study restoration induced rapid changes in the composition, density, size, and distribution of nekton species, but additional monitoring is necessary to quantify longer‐term effects of salt marsh restoration on nekton.
Development of Valves in the Marine Diatom Genus Trigonium
Authors: Tiffany M. A. 
Published: March 2003

Abstract Trigonium arcticum and T. formosum, marine diatoms epiphytic on Ectocarpus sp., were collected from the sublittoral off Point Loma, California. Forming valves of these two sympatric species were studied using scanning electron microscopy. The earliest developing valve of T. arcticum encountered is a porous basal layer of silica, triangular, with pseudocelli just starting to form at each corner. The central annulus, the site of the earliest valve formation, appears to be about the size of a single areola. Early rimoportulae (labiate processes) are interspersed between central areolae and are simple oval openings. Internally these form their labiate lip‐like structures just before cribrum formation. Ridges form on the external side of the basal layer in a honeycomb pattern and produce the walls of the loculate structures. The ridges expand outward until cribrum formation is initiated. Small protuberances grow out from the edge of the ridge‐like structures and then become anvil‐shaped as they grow toward the center of the pores and form the ‘roofs’ of the loculi. In external view of the mature valve, the pores are smoothly covered over except for a ring of C‐shaped slits. These cribra are flush with the surface of the valve. At about the time the cribra are completing, rotae are formed within the porelli of the pseudocelli by extensions from two or three sides. The quadrangular T. formosum develops along much the same pattern. Differences are the less numerous, more centrally located rimoportulae, which possess external tubes and the formation of highly domed cribra.
Algal Polyunsaturated Fatty Acids: Food, Pheromones and Foul Odour
Authors: Watson S. , Janzen L. 
Published: March 2003

AbstractAlgal polyunsaturated fatty acids (PUFAs) are known to be high‐energy, often‐essential resources to freshwater aquatic food webs. On the other hand, high PUFA cell content in some algal taxa has been linked with the production of derivatives that may act as pheromones, allelogens or toxins. It has been known for some time that these compounds function in marine chemical ecology, but recent evidence indicates that they may play similar roles in freshwater ecosystems. This paper presents field and laboratory studies of planktonic and periphytic communities from freshwater systems, and shows that these communities are rich sources of certain PUFAs and derivatives which may function in both positive and negative foodweb interactions. This also has important implications for surface water quality, as these compounds are potent sources of rancid fishy odours.
The Use of Liquid Chromatography–Mass Spectrometry (LC–MS) in the Identification and Characterization of Mycosporine‐Like Amino Acids (MAAS)
Authors: Whitehead K. , Hedges J. I. 
Published: March 2003

AbstractMycosporine‐like amino acids (MAAs) are a class of UV‐absorbing compounds synthesized by a variety of marine and freshwater algae and cyanobacteria with absorption maxima between 310 and 360 nm. To date, ∼25 different MAAs have been characterized with several new compounds identified each year. A major difficulty in the analysis of MAAs is the lack of commercial standards. Thus far, MAAs have been identified by their retention time and UV absorption after separation via high performance liquid chromatography (HPLC). Complementing the HPLC method with the use of mass spectrometry (LC–MS) offers greater sensitivity and reduces the hindrance standard unavailability presents by providing detailed molecular information (molecular weight and fragmentation patterns). The molecular weight information adds one more level to our ability to characterize MAAs and any new UV‐absorbing compounds discovered. The fragmentation patterns obtained via LC–MS also contributes diagnostic information for structure elucidation and identification. LC–MS analysis has been used to examine UV‐absorbing compounds in methanolic extracts from Phaeocystis antarctica. When samples were analyzed using isocratic HPLC elution, several UV‐absorbing peaks were eluted. However, molecular weight and fragmentation patterns of some UV‐absorbing compounds were not commiserate with those expected for MAAs. Additionally, palythenic acid was detected rather than mycosporine‐glycine : valine as had been previously reported for this organism. Gradient elution provided further separation into MAA and ‘unknown’ groupings. The unknown UV‐absorbing component has longer retention times and different mass spectral characteristics with wavelength maxima between 315 and 325 nm. This study benefited immensely by the addition of MS techniques, as many of the compounds would have remained either misidentified or entirely unidentified. The increased analytical capability afforded by LC–MS allows us to further investigate the structural diversity and biochemistry of MAAs aiding our study of the role MAAs play as sunscreen agents.
Highlights of Recent Collections of Marine Algae from the Sultanate of Oman
Authors: Wynne M. J. 
Published: March 2003

AbstractCollections of benthic marine algae made over the past 3 years on the Dhofar coast of the Sultanate of Oman have continued to provide a more complete picture of the floristic affinities of this up‐to‐now poorly explored region. This Algal Biodiversity Project of Oman was funded by the British Government's Darwin Initiative grant for the ‘Survival of Species’ and managed by HTS Development Ltd., of the UK. A rich and floristically complicated flora is emerging, with connections to subtropical and warm temperate regions. Many new algal taxa have been discovered and described, and numerous new records for Oman or for the Indian Ocean have been reported. Some species newly reported for Oman (and the Indian Ocean) had previously been known from Japan (Distromium decumbens, Kallymenia crassiuscula, Dudresnaya japonica, and Chondria crassicaulis). Sporochnus pedunculatus and Pedobesia simplex had been known from the North Atlantic and the Mediterranean and are new records for the Indian Ocean. Some new species of red algae have been described, such as a Dipterocladia and a Plocamium. Some brown algal novelties have also been discovered, including new species of Turbinaria and Jolyna, and a new genus of Chordariaceae. The macroalgal flora of southern Oman is rich with representatives of Codium, Scinaia, Galaxaura, Melanothamnus, and the families Gelidiaceae and Dictyotaceae. Several representative marine algae from southern Oman will be depicted and discussed.
Diversity of Fusiform Microchlorophyte Algae from Itasca State Park, Minnesota
Authors: Dimmer S. K. , Dean M. , Fawley M. W. , Fawley K. P. 
Published: March 2003

AbstractThrough the use of molecular techniques, several different types of fusiform and twisted‐fusiform microchlorophyte algae (Monoraphidium, Ankistrodesmus, etc.) have been characterized from samples taken from lakes and ponds of Itasca State Park, MN. PCR–RFLP analysis of 18S ribosomal RNA genes was used to categorize 29 different isolates from the Itasca State Park lakes into nine different types. The 18S ribosomal DNA sequences were determined for one isolate from each type for phylogenetic analysis. Light microscopy was used so that morphological characteristics as well as molecular characteristics can be compared and contrasted. The morphological characteristics were consistent for each PCR–RFLP type. Further discussion will include comparisons of the distribution and diversity of these organisms from Itasca State Park to those from Arrowwood National Wildlife Refuge, ND.
A Total Evidence Approach to Inferring the Phylogenetic Relationships within Aulacoseira (Bacillariophyta)
Authors: Edgar S. , Theriot E. 
Published: March 2003

AbstractPhylogenies provide the context in which hypotheses about character evolution can be tested. But the phylogenetic understanding of many diatom taxa, including some of the more spatially and temporally ubiquitous genera, is insufficient to fruitfully pursue questions about character evolution within them. Consequently, we have estimated the phylogeny of Aulacoseira using a combination of nucleotide sequence data and data derived from morphological characteristics of the silica cell wall. In addition to the use of traditional ‘discrete’ or ‘qualitative’ morphological characters, we have assessed the use in our cladistic analyses of ‘continuous’ or ‘quantitative’ characters, including descriptors of the ontogenetic trajectories of these characters over a species' life cycle (size range). Also, molecular characters gathered from a chloroplast genome marker (rbcL) as well as a nuclear genome marker (18S rRNA) were used simultaneously in the cladistic estimation of the phylogeny of approximately 12 species of Aulacoseira. In order to have more thorough taxon sampling for a better estimate of phylogeny, we included several fossil species, as well as taxa where cultures were unavailable, by utilizing the morphologically based characters despite the absence of molecular characters for these taxa.
Phosphatase Expression by Chlorella Vulgaris (Chlorophyceae) is Mediated by Internal Phosphorus Levels and External pH
Authors: Evens T. J. , Koenig R. 
Published: March 2003

AbstractPhosphorus has been implicated as one of the causative agents of the eutrophication of lacustrine, estuarine and coastal waters. One of the major inputs of phosphorus into these waters comes from agricultural nonpoint sources in the form of dissolved organic phosphorus (DOP). In order to better understand how DOP may directly impact the microalgal community structure, it is necessary to understand the physiology of DOP uptake and utilization. To this end, cultures of Chlorella vulgaris were grown in custom photobioreactors in acid (pH 5.5) and alkaline (pH 7.5) media under phosphate replete and starved conditions in order to determine the types and triggers of phosphatase expression by this organism. Analysis of differential phosphatase expression during phosphate stress indicates that cultures of C. vulgaris grown under alkaline conditions derepressibly express two alkaline phosphatases, while cultures grown under acid conditions weakly express only one alkaline phosphatase. Analysis of internal and external phosphorus levels, whole‐cell phosphatase activity and in‐gel activity of protein extracts indicate that alkaline phosphatase expression is further mediated by internal, as opposed to external, phosphorus levels.
Dinoflagellate Genomics: Results From an EST Approach
Authors: Bachvaroff T. R. , Herman E. M. , Delwiche C. F. 
Published: March 2003

AbstractDinoflagellates are enigmatic protists with odd nuclear features, interesting plastid gene arrangements and a proclivity for endosymbiotic relationships. Relatively little molecular work has been done on dinoflagellates, and only a handful of genes have been characterized in these organisms. We have begun an Expressed Sequenced Tag (EST) project with the aim of collecting plastid targeted but nuclear encoded genes from peridinin‐containing dinoflagellates. This provides an opportunity to understand the integration of endosymbiont genes into the host cell. Our sequencing effort has produced about 1000 unique ESTs from a Gonyaulax polyedra cDNA library obtained from David Morse. Of the 1535 total ESTs (72%, >400 bp), 466 sequences were identifiable by BLAST with a bit score above 50. The most abundant transcript is the peridinin–chlorophyll‐binding protein, which constituted 3% of the clones. More recently, we began sequencing from an Amphidinium carterae cDNA library made in our laboratory. This provides insight into expression patterns and is a resource for other workers in the field. Several clearly identifiable plastid genes have been found and preliminary analysis confirms the chromophyte, and therefore, tertiary origin of the peridinin plastid.
Spatial and Temporal Distribution of Life History Variants in the Red Alga, Mastocarpus Papillatus
Authors: Fierst J. L. , Kubler J. , Dudgeon S. R. 
Published: March 2003

AbstractWe investigated small‐scale spatial structure in Mastocarpus papillatus, a red alga with sexual and apomictic life‐history variants. Spatial structure and habitat partitioning can facilitate the coexistence of ecologically similar organisms, and in M. papillatus a large scale geographic spatial division is well documented. Variants of M. papillatus display geographic parthenogenesis where sexual fronds are common south of San Francisco Bay and apomicts dominate north of San Francisco Bay. Although geographic parthenogenesis in M. papillatus is well‐documented small‐scale spatial structure was not previously known due to the similar appearance of sexual and apomictic upright fronds. We investigated whether sexual and apomictic fronds differed in their spatial distribution by sampling for vertical differences in intertidal height and horizontal patchiness. Fronds were sampled when reproductive and cultured for life history. We found sexual variants were significantly aggregated at lower intertidal heights while apomicts were found throughout the intertidal range. Sexual fronds were strongly seasonal and reproduced October–December whereas apomictic fronds reproduced throughout the year. These results parallel the large‐scale geographic distribution with apomicts inhabiting marginal areas, and suggest dispersal capability may also facilitate geographic parthenogenesis.
Estimating Divergence Times within the Charophyta: A Bayesian Approach Using Fossil and DNA Sequence Data
Authors: Karol K. G. , McCourt R. M. , Delwiche C. F. 
Published: March 2003

AbstractMorphological and molecular studies have advanced our understanding of charophycean green algal relationships. A recent multigene phylogenetic analysis has identified the Charales as the closest living relatives of land plants with the Coleochaetales sister to the Charales/land plant lineage. With a robust phylogeny now in hand, it is possible to explore phylogeny‐dependent questions that were previously difficult to assess. Estimating the divergence time of the land plant lineage is one such question. The most recent time estimate for the colonization of land by plants is 1061 ± 109 million years ago and 703 ± 45 million years ago for the divergence of vascular plants and bryophytes, a result much older than that found in the fossil record (roughly 470 million years ago). Several problems are inherent in estimating divergence times using DNA sequence data; these include the assumption of a molecular clock and choosing from a sparse fossil record for an external calibration date. Unlike most algae, a rich fossil record exists for the Charales in the form of calcified oospores termed gyrogonites. Representative gyrogonites that can be attributed to all six of the extant genera in the Characeae have been identified with reasonable accuracy. These six calibration points, identified from a closely related lineage of land plants, can be used in conjunction with a multigene DNA dataset to estimate the time that the land plant and Charales lineages diverged from their common ancestor.
UV‐Acclimation of Cultured Phytoplankton Exposed to Natural and Enhanced UVB Radiation and Methodological Aspects of MAA Quantification
Authors: Laurion I. , Roy S. 
Published: March 2003

AbstractBloom‐forming dinoflagellates often synthesize high concentrations of mycosporine‐like amino acids (MAAs) as a protection from high PAR and UV radiation, which may afford them a competitive advantage over other species. Photoprotection and long‐term acclimation to natural and enhanced UVB radiation were examined during 4 weeks in three dinoflagellates and one diatom. Semi‐continuous, nutrient‐replete cultures were maintained outdoors under natural light, with or without additional UVB (from lamps). The photosynthetic performance (XE‐PAM fluorometry) and the concentration and composition of MAAs and photoprotective carotenoids (PPCs; comprising xanthophylls) were followed weekly. A great variety of MAAs was found in the dinoflagellates (up to 10, identified by cochromatography and LC–MS). Large differences between sp. (and between two strains of the same sp.) were observed. In most cases, the composition and concentration of MAAs and PPCs increased under enhanced UVB. Growth rate and photosynthetic performance were sometime lower under enhanced UVB, while in other cases photoacclimation seemed to occur. The least affected sp. was Alexandrium tamarense who responded most rapidly to enhanced UVB. The algae also responded to changes in natural incident radiation. Some methodological aspects of MAA quantification were also investigated (with four species of dinoflagellates). Our results indicate how freezing (liquid‐N) likely breaks the cells, mobilizing the water‐soluble MAAs in the filter moist (otherwise highly packaged in fresh cells), while the organelles containing the pigments remain relatively intact. The implications of standard sample handling on the evaluation of MAA concentration in algae and on the estimation of the absorption of suspended material in water from in vivo spectroscopy (filter pad technique) will also be discussed.
The Transition From Algae to Embryophytes: Chloroplast Phylogenomic Evidence (II)
Authors: Lee J. , Manhart J. R. 
Published: March 2003

AbstractThe transition of plant life from aquatic algae to land plants was one of the major events in the history of life. However, in hypothesizing the evolutionary path of the transition, limited shared phenotypic characters in aquatic algae and land plants (embryophytes) have been a major hinderance. Chloroplast genomes contain characters useful in tracing evolutionary histories. Embryophyte chloroplast genomes are distinguished from algal cpDNAs by the presence of over 20 group II introns and three ribosomal protein operons (rpl23, clpP and 3Œrps12 operons). These phylogenomic features indicate a phylogenetic relationship of charophytes and embryophytes. In addition to these operons and introns, the evolution of rRNA and psbB operon evolution of streptophyte lineages will be incorporated with major biological phenotypic features to produce a phylogenetic tree. Basal embryophytes, the antithetic hypothesis, monophyly of embryophytes, and paraphyly of charophytes will be discussed. Strepotophytes are classified into three major groups (basal streptophytes, mid‐divergent streptophytes and late divergent charophytes‐embryophytes).