Primary Bloom Research Articles

Huge amounts of iron raw material from the Early Iron Age settlement of Dédestapolcsány-Verebce (N-Hungary) – a preliminary archaeometallurgical study

The team of the Institute of Archaeological Sciences of the Eötvös Loránd University has been investigating the Early Iron Age hillfort at Dédestapolcsány-Verebce-bérc (Northeast Hungary) since 2020. The settlement was destroyed by siege in the late 7th century BC, as evidenced by hundreds of early Scythian bronze arrowheads and burnt buildings. Based on the recovered metal and pottery findings the settlement dated to the Early Iron Age in the Carpathian Basin (end of the 7th century – beginning of the 6th century BC). The quantity of the Early and Middle Iron Age iron and bronze artefacts and pieces of iron raw material on the site is exceptionally high. More than 30 depots were unearthed which include pieces of iron raw material. In the whole territory, the number of these finds is more than 600. The average weight of the pieces was 1.54 kg. A few selected objects were sampled and subjected to archaeometric analysis (OM and SEM-EDS). The main aim of the examinations carried out by the experts of the Archaeometallurgical Research Group of the University of Miskolc (ARGUM) was the material characterisation of the samples to figure out what kind of processing has been applied and reveal how the iron raw materials can be connected in any way to the other iron objects found at the site. Based on the results, it can be concluded that the iron pieces are compacted with a slightly heterogeneous structure. Each one is a part of a single bloom, not several pieces of different blooms assembled together. Numerous pores and cavities were observed in the microstructure of the samples. Their basic character is similar, although, they differ from each other, mainly in terms of carbon content and degree of forming. These pieces are not typical semi-finished products; they can be identified somewhere halfway between primary bloom and compacted bar.

Karenia brevis bloom patterns on the west Florida shelf between 2003 and 2019: Integration of field and satellite observations

Harmful algal blooms of the toxic dinoflagellate Karenia brevis occur almost annually on the West Florida Shelf (WFS) of the eastern Gulf of Mexico. To date, however, comprehensive assessments of K. brevis bloom spatial extent and temporal occurrence are lacking due to limitations in the two primary bloom monitoring techniques: microscopy evaluation of field-collected water samples and satellite remote sensing of ocean color. This is despite community efforts in expanding sampling coverage statewide and developing remote sensing algorithms to interpret color changes of surface waters. In this work, an approach is developed to combine the strengths of both techniques to estimate mean bloom occurrence frequency and bloom intensity as well as bloom extent at weekly, bi-weekly, monthly, and annual intervals between 2003 and 2019. Here, due to technical constraints on ocean color remote sensing, a bloom is defined as waters with K. brevis concentrations greater than 1.5 × 105 cells L−1. While microscopy examination of surface water samples provides K. brevis cell concentrations to help delineate bloom locations from Moderate Resolution Imaging Spectrometer on Aqua (MODIS/A) images, the imagery provides far more synoptic and frequent observations to make the bloom characterization statistically meaningful. Such derived bloom statistics often show bloom patterns that are not always known previously or at the time of the event, and in some years, they also differ from those determined from microscopic taxonomy data alone. For example, in terms of bloom size, two major bloom periods are observed in 2005 – 2007 and 2014 – 2018, respectively, when annual cumulative bloom size exceeded ∼50,000 km2. While preliminary in nature, the approach and results from this work may represent a first step to integrate water sample analysis and satellite remote sensing towards an improved characterization of K. brevis blooms on the WFS.

Addition of a Secondary Functional Bloom Filter

Key–value data structures have been extensively used in various applications. When a large amount of data needs to be compactly stored in a fixed memory size, a functional Bloom filter is a space-efficient key–value structure. In this letter, we propose a 2-stage functional Bloom filter structure composed of a primary functional Bloom filter and a secondary functional Bloom filter to resolve the indeterminables produced from the primary functional Bloom filter. We analytically present the memory ratio allocated for each of the two Bloom filters to achieve the lowest search failure rate. The analytical result is validated through experiments, thereby demonstrating that the optimal performance is realized when the secondary functional Bloom filter uses 3% of the total memory.

Patterns and drivers of phytoplankton phenology off SW Iberia: A phenoregion based perspective

Phytoplankton patterns, tightly linked to the dynamics of the ocean surface layer and its atmospheric forcing, have major impacts on ecosystem functioning and are valuable indicators of its response to environmental variability and change. Phytoplankton phenology and its underlying drivers are spatially variable, and the study of its patterns, particularly over heterogeneous regions, benefits from a delineation of regions with specific phenological properties, or phenoregions. The area Southwest off the Iberian Peninsula (SWIP, NE Atlantic) integrates a highly complex set of coastal and ocean domains that collectively challenge the understanding of regional phytoplankton phenology and related forcing mechanisms. This study aims to evaluate phytoplankton phenology patterns over the SWIP area, during an 18-year period (September 1997 – August 2015), using an objective, unsupervised partition strategy (Hierarchical Agglomerative Clustering – HAC) based on phenological indices derived from satellite ocean colour data. The partition is then used to describe region-specific phytoplankton phenological patterns related to bloom magnitude, frequency, duration and timing. Region-specific variability patterns in phenological indices and their linkages with environmental determinants, including local ocean physical-chemical variables, hydrodynamic variables and large scale climate indices, were explored using Generalized Additive Models (GAM). HAC analyses identified five coherent phenoregions over SWIP, with distinctive phytoplankton phenological properties: two open ocean and three coastal regions. Over the open ocean, a single, low magnitude and long bloom event per year, was regularly observed. Coastal phenoregions exhibited up to six short bloom events per year, and higher intra-annual and variability. GAM models explained 50–90% of the variance of all phenological indices except bloom initiation timing, and revealed that interannual patterns in phytoplankton phenology and their environmental drivers varied markedly among the five phenoregions. Over the oceanic phenoregions, large-scale climate indices (Eastern Atlantic Pattern, Atlantic Meridional Oscillation), mixed layer depth (MLD) and nitrate concentration preceding primary bloom events were influential predictors, reflecting the relevance of nutrient limitation. For the Coastal-Slope, a relatively more light-limited phenoregion, North Atlantic Oscillation and wind speed were more relevant, and bloom magnitude was also positively influenced by riverine discharge. This variable was a significant predictor of bloom frequency, magnitude and duration over the Riverine-influenced region. Over the Upwelling-influenced region, upwelling intensity and mean annual MLD showed stronger partial effects on phytoplankton phenology. Overall, our phenology-based unsupervised approach produced a biologically-relevant SWIP partition, providing an evaluation of the complexity of interactions between phytoplankton and multiple environmental forcing, particularly over coastal areas.

Abundance of the iron containing biomolecule, heme b, during the progression of a spring phytoplankton bloom in a mesocosm experiment.

Concentrations of heme b were determined in a mesocosm experiment situated in Gullmar Fjord off Sweden. The mesocosm experiment lasted for ca. one hundred days and was characterised by the growth of a primary nutrient replete and a secondary nutrient deplete phytoplankton bloom. Heme b varied between 40 ± 10 pmol L-1 in the prebloom period up to a maximum of 700 ± 400 pmol L-1 just prior to the time of the primary chlorophyll a maximum. Thereafter, heme b concentrations decreased again to an average of 120 ± 60 pmol L-1. When normalised to total particulate carbon, heme b was most abundant during the initiation of the nutrient replete spring bloom, when ratios reached 52 ± 24 μmol mol-1; ten times higher than values observed both pre and post the primary bloom. Concentrations of heme b correlated with those of chlorophyll a. Nevertheless, differences were observed in the relative concentrations of the two parameters, with heme b concentrations increasing relative to chlorophyll a during the growth of the primary bloom, decreasing over the period of the secondary bloom and increasing again through the latter period of the experiment. Heme b abundance was therefore influenced by nutrient concentrations and also likely by changing community composition. In half of the mesocosms, pCO2 was elevated and maintained at ca.1000 μatm, however we observed no significant differences between heme b in plus or ambient pCO2 mesocosms, either in absolute terms, or relative to total particulate carbon and chlorophyll a. The results obtained in this study contribute to our understanding of the distribution of this significant component of the biogenic iron pool, and provide an iron replete coastal water end member that aids the interpretation of the distributions of heme b in more iron deplete open ocean waters.

Dissolved N:P ratio changes in the eastern tropical North Atlantic: effect on phytoplankton growth and community structure

Previous bioassays conducted in the oligotrophic Atlantic Ocean identified availability of inorganic nitrogen (N) as the proximate limiting nutrient control of primary production, but additionally displayed a synergistic growth effect of combined N and phosphorus (P) addition. To classify conditions of nutrient limitation of coastal phytoplankton in the tropical ocean, we performed an 11 d nutrient-enrichment experiment with a natural phytoplankton community from shelf waters off northwest Africa in shipboard mesocosms. We used pigment and gene fingerprinting in combination with flow cytometry for classification and quantification of the taxon-specific photoautotrophic response to differences in nutrient supply. The developing primary bloom was dominated by diatoms and was significantly higher in the treatments receiving initial N addition. The combined supply of N and P did not induce a further increase in phytoplankton abundance compared to high N addition alone. A secondary bloom during the course of the experiment again displayed higher primary producer standing stock in the N-fertilized treatments. Bacterial abundance correlated positively with phytoplankton biomass. Dominance of the photoautotrophic assemblage by N-limited diatoms in conjunction with a probable absence of any P-limited phytoplankton species prevented an additive effect of combined N and P addition on total phytoplankton biomass. Furthermore, after nutrient exhaustion, dinitrogen (N-2)-fixing cyanobacteria succeeded the bloom-forming diatoms. Shelf waters in the tropical eastern Atlantic may thus support growth of diazotrophic cyanobacteria such as Trichodesmium sp. subsequent to upwelling pulses.

Late spring and summer patterns of euphausiid reproduction in Southeast Alaska fjord waters

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 516:153-161 (2014) - DOI: https://doi.org/10.3354/meps11003 Late spring and summer patterns of euphausiid reproduction in Southeast Alaska fjord waters Andrew R. Szabo1,*, Harold P. Batchelder2 1Alaska Whale Foundation, 4739 University Way NE 1239, Seattle, WA 98105, USA 2College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA *Corresponding author: szabo@alaskawhalefoundation.org ABSTRACT: Abundance, size and developmental stage data for furcilia and juvenile euphausiids together with data on the timing and prevalence of attached spermatophores on adult females are used to infer times of spawning by 4 euphausiid species in Frederick Sound and lower Stephens Passage, Southeast Alaska. Results from net tows conducted between late May and September 2008 and a single, opportunistic dip-net sample on 21 April indicate that Thysanoessa raschii and T. longipes spawned in association with the spring phytoplankton bloom in April and continued spawning until June, with juveniles first appearing in mid- to late June. Presence of female T. spinifera carrying spermatophores in mid-April indicates that T. spinifera spawns in association with the spring bloom as well; however, absence of larval T. spinifera suggest that spawning in the inshore waters is comparatively rare. In contrast, observations of female Euphausia pacifica carrying spermatophores from late May to August and the first appearance of early furcilia in August indicate that spawning occurs, at least to some extent, after the primary bloom. However, the appearance of juvenile E. pacifica in late June suggests that spawning occurred earlier as well and in discrete bouts. We argue that the absence of E. pacifica furcilia that were likely to have originated from an early spawning event may indicate that E. pacifica juveniles observed in late June were advected into the study region from the Gulf of Alaska. Overall, phenology of seasonal reproduction in this Alaskan fjord is similar to that observed in coastal waters in arctic and temperate ecosystems. KEY WORDS: Euphausiids · Southeast Alaska · Spawning timing · Juvenile · Larva · Fjord Full text in pdf format PreviousNextCite this article as: Szabo AR, Batchelder HP (2014) Late spring and summer patterns of euphausiid reproduction in Southeast Alaska fjord waters. Mar Ecol Prog Ser 516:153-161. https://doi.org/10.3354/meps11003 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 516. Online publication date: December 03, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

ESTIMATION OF RHODODENDRON FLOWERING INTENSITY IN BOTANICAL GARDEN OF SIAULIAI UNIVERSITY DURING 2003-2007

Historically, rhododendrons (Rhododendron L.) have rarely been planted in Lithuania landscapes due to lack of knowledge about their cultivation and due to complicated adaptation. However, nowadays rising interest in rhododendron might be caused by increasing investigates in adaptation and cultivation of these plants. One of the main requirements for ornamental woody plants is the quality of flowering. Specifically flowering intensity should be seen as the most important criterion of ornamental quality was evaluated. Flowering intensity was evaluated in view of abundance of flowering. Methods that have been verified by long-term investigations were used to estimate the intensity and duration of flowering for rhododendron cultivars in the Botanical Garden of Siauliai University. Usually the collection evaluate using the five main criteria: (1) general condition; (2) resistance to low temperatures; (3) flowering intensity; (4) phytopathological condition; (5) suitability for cultivation in green plantations. Data collected during 2003–2007 demonstrate that the majority of rhododendron primary bloom occurs from May (the third decade) to June (the third decade). The majority (64%) of the cultivars in the collection flower abundantly (3 points). Reasons for poor and uneven flowering of rhododendrons might be the freezing of flower buds during late spring frosts. For some rhododendron cultivars growing in the Botanical Garden, repeat flowering is typical. Second bloom as is customary started in August and lasted until the middle of September. After comparing primary and repeat flowering, we found the second bloom to be less intensive, although the duration of the repeat bloom was approximately the same as the primary bloom in the spring. The research initiated by the Botanical Garden will help the landscape industry and consumers to select rhododendrons that are suitable for cultivation and can abundantly flowering in Northern Lithuania.

Phytoplankton community structure and stocks in the Southern Ocean (30–80°E) determined by CHEMTAX analysis of HPLC pigment signatures

Abstract The geographic distribution, stocks and vertical profiles of phytoplankton of the seasonal ice zone off east Antarctica were determined during the 2005–2006 austral summer during the Baseline Research on Oceanography, Krill and the Environment-West (BROKE-West) survey. CHEMTAX analysis of HPLC pigment samples, coupled with microscopy, permitted a detailed survey along seven transects covering an extensive area between 30°E and 80°E, from 62°S to the coast. Significant differences were found in the composition and stocks of populations separated by the Southern Boundary of the Antarctic Circumpolar Current (SB), as well as a small influence of the Weddell Gyre in the western sector of the ‘zone south of the Antarctic Circumpolar Current’ (SACCZ). Within the SACCZ, we identified a primary bloom under the ice, a secondary bloom near the ice edge, and an open-ocean deep population. The similarity of distribution patterns across all transects allowed us to generalise a hypothesized sequence for the season. The primary phytoplankton bloom, with stocks of Chl a up to 239 mg m−2, occurred about 35 days before complete disappearance of the sea ice, and contained both cells from the water column and those released from melting ice. These blooms were composed of haptophytes (in particular, colonies and gametes of Phaeocystis antarctica), diatoms and cryptophytes (or the cryptophyte symbiont-containing ciliate Myrionecta rubrum). Aggregates released by melting ice quickly sank from the upper water column and Chl a stocks declined to 56–92 mg m−2, but the bloom of diatoms and, to a lesser extent, cryptophytes continued until about 20 days after ice melt. The disappearance of sea ice coincided with a sharp increase in P. antarctica and grazing, as indicated by increasing phaeophytin a and phaeophorbide a. Chlorophyllide content suggests that the diatom bloom then senesced, probably due to iron exhaustion. Stocks rapidly declined, apparently due to grazing krill that moved southward following the retreating sea ice. We suggest that grazing of the bloom and export of faecal pellets stripped the upper water column of iron (as suggested by low Fv/Fm ratios and CHEMTAX pigment ratios in Haptophytes – iron was not measured). Thus, export of iron by grazing, and possibly sedimentation, created a southward migrating iron gradient, limiting growth in the upper water column. North of the postulated iron gradient, a nanoflagellate community developed at depth, with Chl a stocks from 36–49 mg m−2. This community was probably based on regenerated production, sustained by residual and/or upwelling iron, as indicated by a close correspondence between distributions of Chl a and profiles of Fv/Fm. The community consisted of haptophytes (chiefly Phaeocystis gametes), dinoflagellates, prasinophytes, cryptophytes, and some small diatoms. Selective grazing by krill may have fashioned and maintained the community. North of the SB, Chl a ranged from 40–67 mg m−2 and was found predominantly in the mixed layer, but Fv/Fm ratios remained low, suggesting the community of P. antarctica and diatoms was iron-limited. These interpretations provide a cogent explanation for the composition and structure of late summer microbial populations in the marginal ice zone.

Variability of upwelling and chlorophyll in the equatorial Atlantic

The primary seasonal phytoplankton bloom in the equatorial Atlantic occurs in boreal summer in response to seasonal strengthening of zonal winds. However, the equatorial Atlantic also has a secondary bloom in late fall – early winter. This secondary bloom is weaker than the primary bloom by a factor of two, but is subject to year‐to‐year variability that is similar in magnitude. Here, observational evidence, including sea level and SeaWiFS‐derived chlorophyll‐a concentration, is used to examine several potential causes of this secondary bloom. The secondary bloom varies independently of blooms along the eastern coastal zones. Also, the secondary bloom has a relationship with the cessation of the Northwest African monsoon, which propotes the secondary seasonal strengthening of the trade winds. The variability of the secondary bloom results from perturbations in the depth of the thermocline induced by zonal wind anomalies in the western tropical Atlantic. These wind anomalies are correlated with mean sea level atmospheric pressure anomalies in the region of the northern subtropical high as well as over the Amazon.

Spatial variability of chlorophyll- a in the Marginal Ice Zone of the Barents Sea, with relations to sea ice and oceanographic conditions

The distribution of chlorophyll- a in the Barents Sea was observed from the optical satellite instrument Sea-viewing Wide Field-of-view Sensor (SeaWiFS) during May 1999. In the same period water samples were collected in situ and analysed. Contrary to previous studies of phytoplankton distribution in the Barents Sea, we rigourously analysed the chlorophyll- a distribution characteristics with respect to sea ice and oceanographic conditions, spatially and temporally. The spatial distribution of surface chlorophyll- a was analysed and related, statistically, to the ice edge and sea ice concentrations from the Special Sensor Microwave Imager (SSM/I) satellite instrument. The highest chlorophyll- a concentrations were observed near the ice edge, and then decreased further into the ice. The spatial variability of the chlorophyll- a concentrations in this region was high, even in open water along the ice edge. The chlorophyll- a observations indicated a strong primary bloom about 2 weeks after the ice edge had retreated from a given measurement point. There were also indications of several minor blooms about 2 weeks after the initial bloom. The vertical distributions of chlorophyll- a are presented for nine different stations in the Marginal Ice Zone (MIZ) of the northern Barents Sea and discussed in terms of simultaneously measured temperature–salinity CTD profiles. Water mass properties and sea ice history have a significant impact on the vertical distribution of phytoplankton. The surface chlorophyll- a concentration was about 60% higher (±70% S.D.) than the total column average. The correlation coefficient was 0.87, indicating that surface values are good predictors for relative levels of total phytoplankton biomass during spring conditions. We propose a method to identify the stage of the phytoplankton bloom based on satellite observations of chlorophyll- a, temperature, salinity and sea ice history. Based on an extensive set of field measurements at different times from many locations in the Barents Sea, we have produced empirical formulae to estimate the integrated chlorophyll- a content for the water column from surface (satellite) measurements during early spring (homogeneous water masses) and bloom conditions.

The effect of in situ iron addition on the sinking rates and export flux of Southern Ocean diatoms

Abstract During the Southern Ocean Iron RElease Experiment (SOIREE), conducted in February 1999 at 61°S, 141°E in high nutrient, low chlorophyll waters south of the Polar Front, we measured the intrinsic sinking rates of diatoms at two depths inside and outside of an iron-fertilised patch. Overall, the sinking rates of the diatoms estimated by the SETCOL method (Bienfang, Canadian Journal of Fisheries and Aquatic Sciences 38 (1981) 1289–1294 were significantly lower inside than outside the patch, and a time series of sinking rates (chlorophyll-based) indicated that the rates of cells >22 μm reduced to a minimum (0.47 m d−1) 8 days after the first in situ iron addition. A subsequent increase in sinking rates (chlorophyll-based) of >22 μm cells coincided with an increase in algal iron stress (based on diatom flavodoxin levels). The primary bloom species, Fragilariopsis kerguelensis and Nitzschia and Navicula sp. reduced their sinking rates most markedly within the patch, showing a decrease of up to 87% of initial rates, over the 13 days of the time series. In contrast, the very largest cells (>1 mm, Trichotoxon and Thalassiothrix) showed little change in sinking rate inside or outside the patch. Sinking rates of resident cells associated with a deep chlorophyll maximum (40–75 m) in and out of the patch also showed no significant sinking rate change upon iron addition. Given these results and the known longevity of the SOIREE bloom (at least 60 d), we infer that sinking rate reduction is an integral part of a species-specific bloom response to elevated Fe supply. We calculate that sinking losses of iron-saturated, unaggregated cells would have been ∼1% d−1. A 1% daily loss would have halved cell accumulation at the surface over 60 d, primarily via a reduction in growth potential.

Epiphytic Colonization of Pear Stigmas and Hypanthia by Bacteria During Primary Bloom

ABSTRACT Pear blossoms were sampled during various stages of bloom in 1991 and 1992 from orchards at Cashmere, WA, and Corvallis and Medford, OR, for epiphytic populations of culturable bacteria. On stigmatic surfaces, bacteria were isolated from 2 to 32% of blossoms prior to petal expansion and from 47 to 94% of blossoms by petal fall. In general, a lower percentage of hypanthia than stigmas supported bacterial populations. Randomly selected bacteria isolated at population levels of >/=10(4) CFU/tissue were identified by fatty acid methyl ester analysis. Diverse genera of gram-negative and -positive bacteria were identified from the Medford and Cashmere field sites. Pseudomonas syringae and Pseudomonas viri-diflava were isolated from all sites and were the predominant species detected at Corvallis, where they were isolated from 28% of the blossoms sampled on a given date. Because most pear blossoms do not support detectable populations (>/=10(2) CFU/tissue) of culturable bacteria prior to petal expansion, we speculate that introduced biocontrol agents may become established with minimal competition from indigenous epiphytes at early bloom stages.

Spring bloom sedimentation in a subarctic ecosystem

A 5-yr study (1985 to 1989) of spring bloom sedimentation in Auke Bay, Alaska, indicates that the sinking response of diatoms to ambient nutrients influences both species succession during the spring bloom and the subsequent sedimentation of new production. Diatoms from the genera Thalassiosira, Chaetoceros and Skeletonema formed the bulk of the spring bloom each year. Growth of Thalassiosira spp. consistently initiated the primary bloom, while Skeletonema costatum tended to grow later in, or after, the primary bloom. We postulate that this successional pattern is driven by interspecific nutrient competition. Overall, sedimentation flux of the dominant species of bloom diatoms was correlated with surface concentrations of cells integrated over the bloom period. In fact, different linear relationships existed when Thalassiosira and Chaetoceros spp. were considered separately, but not for Skeletonema sp., indicating that marked differences exist between the sedimentation tendencies of these genera. The observed inter-generic differences are explicable by the different overall sinking rates, as well as different nutrient-sensitivities of the sinking rates of each genus. Thalassiosira spp., the fastestsinking and most nutrient-sensitive species, contributed up to 10 x more carbon to the benthos in all years of the study, reaching a maximum of 11.1 gCm-2 over a single spring bloom event in 1988. This study indicates that the tendency to sink to the benthos during and/or after a bloom is highly dependent on species-specific cell physiology, and supports the idea that it is the fast-sinking, nutrient-sensitive diatoms, such as Thalassiosira species, that constitute the major source of vertical carbon flux in this embayment and other such coastal ecosystems during the spring bloom.

Interannual variability in the spring phytoplankton bloom in Auke Bay, Alaska

Data on phytoplankton primary production, biomass, and species composition were collected during a 5 yr (1985–1989) study of Auke Bay, Alaska. The data were used to examine the interannual differences in the timing, duration, and magnitude of the spring phytoplankton blooms during each year and to relate these differences to interannual variations in weather patterns. Within any given year, a pre-bloom phase was characterized by low available light, low rates of primary production, low biomass, and predominantly small (<10µm) diatoms. During the primary bloom, integrated production rates rose to 4 to 4.5 g C m−2 d−1, and integrated biomass levels reached 415 to 972 mg chlorophyll m−2. Primary blooms were usually dominated by large diatoms (Thalassiosira spp.), and in a single year (1989) byChaetoceros spp. The primary blooms terminated upon nutrient depletion in the euphotic zone. Secondary blooms, triggered by nutrient resupply from below, occurred sporadically after the primary bloom and accounted for 4 to 31% of total spring production. The date of initiation and the duration of the primary bloom varied little from year to year (standard deviation 3 and 5 d, respectively). Seasonal production rates and biomass levels varied interannually by a factor of 2 to 3. In contrast, intra-annual variations of more than an order of magnitude, especially in biomass, occurred over periods as short as 10 d. These large variations over short time periods indicate the importance of synchronous timing between spring blooms and the production of larval fish and shellfish, which depend on an appropriate and adequate food supply for growth and survival. Parameters describing primary production (e.g. peak daily production, mean daily production, and total production during the primary bloom and the entire season) exhibited little interannual variation (coefficient of variation, CV = 10 to 19%), but a large degree of intra-annual variation (CV = 77 to 116%). Similarly, interannual variations in biomass (peak chlorophyll, mean chlorophyll) were also lower (CV = 20 to 33%) than intra-annual variations (CV = 85 to 120%).

Importance of a winter dinoflagellate-microflagellate bloom in the Patuxent River estuary

A dense bloom of Katodinium rotundatum was observed in the Patuxent River estuary from December to February 1989. The dinoflagellate dominated phytoplankton densities reaching 10 8 cells l −1 and contributed up to 1900 μgC l −1 in near-surface depths. The bloom maintained a distinct patch extending over 10–25 km of the estuary or approximately one-third to one-half of the total estuary (salinities from 5–13 ppt) and was restricted to regions immediately upriver of the transition between the shallow upriver (3–4 m) and deeper lower estuary (10 m). Daily measurements collected in the primary bloom area at the same time each day in the study area indicated 80- and 120-fold variations in chlorophyll and cell densities from day to day. Densities of potential grazers in the region were high with rotifers, primarily Synchaeta baltica, reaching densities of 1000 l −1 in early winter, and the copepod Eurytemora affinis reaching levels exceeding 1·15 × 10 5 m −3 in February. Estimates of grazing pressure by these planktonic herbivores indicated substantial grazing losses for the bloom, with up to 67% of bloom biomass consumed day −1 in February. Nutrient concentrations and ratios of N P during the bloom suggested potentially N-limited conditions; bloom demise was coincident with a shift to high N P ratios and high river flows. These data as well as other historical data suggest that dinoflagellate blooms in the lower Patuxent River estuary could be the primary source of carbon to the system during the winter and supply a large reservoir of labile organic matter to planktonic secondary producers prior to annual spring diatom blooms in the region.

TIMING OF SPAWNING OF THYSANOESSA RASCHII (EUPHAUSIACEA) AND OCCURRENCE OF THEIR FEEDING-STAGE LARVAE IN AN ALASKAN BAY

ABSTRACT The timing of spawning and onset of feeding for euphausiid larvae in Auke Bay, Alaska, was monitored for 3 years. Thysanoessa raschii was the most abundant euphausiid species in the study area. In all years the eggs were most abundant in the plankton soon after the major spring phytoplankton bloom was completed. During all 3 years of observation, the major cohort of stage I calyptopis, which is the first feeding stage, appeared in the plankton after the primary diatom bloom was finished. When the calyptopes initiated feeding, the water column was physically stratified and low nutrient availability limited primary production in the photic zone. The results suggest that euphausiid larvae in Auke Bay are dependent on secondary phytoplankton blooms for food, rather than the major spring diatom bloom. The concentrations of nauplii were about 70,000·m―2 in 1986, 40,000·m―2 in 1987, and 140,000·m―2 in 1988. Concentrations of calyptopes peaked at about 40,000·m―2 in 1986, 10,000·m―2 in 1987, and 70,000·m―2 in 1988. Maximum concentrations of furciliae were 730 to 1,660·m―2 in 1988, 1,037·m―2 in 1986, and 10 to 19·m―2 in 1987.

Lygus Bug Control and Effects on Predators, 1988

Abstract Sweet grain lupin was seeded at 270 lb/acre in 11-inch rows near Waitsburg, Walla Walla County, Wash. Ten treatments, including the control, were replicated 5 times in a randomized complete block design of 0.01-acre plots. Insecticides were applied with a CO2-powered backpack sprayer with a 4-ft spray boom calibrated to deliver 27 gal/acre at 30 psi. Four 8003 flat-fan nozzles at 19-inch spacings were used on the spray boom. The first treatment was made 1 Jul at 50% primary bloom followed by a second treatment 21 Jul. Populations were estimated from 5 180° sweeps on 1, 7, 15, 21, and 28 Jul with a 15-inch-diam sweep net. A count of MPB was not made on the 1 Jul sampling date.

Evaluation of Insecticides for Lygus Bug Control, 1987

Abstract White lupin was seeded in experimental plots at 200 lb/acre in 11-inch rows near Waitsburg, Walla Walla County, Wash., for the control of lygus bugs. Seven treatments were replicated 4 times in a randomized complete block design of 0.01-acre plots. The treatments were applied with a CO2-powered backpack sprayer with a 4-ft spray boom calibrated to deliver 27 gal/acre at 30 psi. Four 8003 flat-fan nozzles at 19-inch spacings were used on the spray boom. First treatment was on 8 Jun at 50% primary bloom; the second treatment was made on 20 Jun. A third, late-season treatment was applied on 20 Jul. Population densities of lygus bugs were determined from 5 (180-degree) sweeps with a 15-inch-diam sweep net on 8, 14, 20, and 28 Jun and 8, 16, and 28 Jul. Samples were bagged in the field and counted in the laboratory. Adult lygus bugs (ALB) were counted separately from nymphs (NLB).

Lygus Bugs and Western Flower Thrips Control on White Lupin, 1986

Abstract White lupin was seeded at 180 lb/acre in 11-inch rows near Waitsburg, Walla Walla County, Wash. Seven treatments were replicated 4 times in a randomized complete-block design of 0.01-acre plots. Insecticides were applied with a CO2-powered backpack sprayer with a 4-ft spray boom calibrated to deliver 80 gal/acre at 30 psi. Four 8003 flat-fan nozzles at 19-inch spacings were used on the spray boom. First treatment was on 13 Jun at 50% primary bloom followed by the second treatment on 27 Jun. Populations were estimated from 5 (180-degree) sweeps on 13, 20, and 27 Jun and 6 and 14 Jul with a 15-inch-diam sweep net. No samples were taken for western flower thrips (WFT) on 14 Jul due to their almost complete absence from all plots.