Estimating spatial variation in the abundance of potential microcystin-producing Microcystis spp. using real-time PCR during summer bloom in Lake Taihu

Lake Taihu, which is the third largest freshwater lakes in China, is a hypertrophic shallow lake in eastern China that has experienced lake-wide cyanobacterial blooms annually during the last few decades. In this study, quantitative real-time PCR assays targeting on phycocyanin intergenic spacer (PC-IGS) and a microcystin synthetase gene mcyD were established, respectively. Water samples collected from eight sampling sites (including Zhushan Bay (N5), Meiliang Bay (N2), Gonghu Bay (N4), West lake areas (W2 and W4), south-middle lake areas (S2, S4 and S5)) in August of 2009 and 2010 were analyzed using real time PCR for the distribution and abundance of toxic and total Microcystis populations. The results showed that Microcystis exists as a mixed population of potential toxic and non-toxic genotypes, and there was significant spatial changes in the abundance of potential toxic Microcystis on the basis of quantification by quantitative real-time PCR analysis: the abundance of toxic Microcystis population in 2009 and 2010 varied from 4.08 × 10⁴ to 8.28 × 10⁶ copies mL^?1, from 4.45 × 10⁵ to 5.22 × 10⁷ copies mL^?1, respectively. Meanwhile the ratio of the mcyD subpopulation to the total Microcystis varied considerably, from 5.7% to 41.1% in 2009 and from 10.3% to 65.8% in 2010 in all sampling sites, and the value is high in Zhushan Bay and Meiliang Bay with the high level of eutrophication. Correlation analysis showed the abundance of toxic and total Microcystis being strongly related (P < 0.01). However, there is different effects of environmental factors on the abundance of toxic and non-toxic Microcystis populations. The abundance of toxic and total Microcystis populations were positively correlated with chlorophyll-a (Chl-a) concentration (P < 0.01) suggesting that Microcystis is dominated genera of cyanobacterial bloom in Lake Taihu. It was also found that the abundance of toxic Microcystis and the proportion of toxic subpopulation to the total Microcystis were positively correlated with total phosphorus and orthophosphate concentrations (P < 0.01), whereas there was no significant correlation with total nitrogen and nitrate concentration (P > 0.05). All data suggest that phosphorus concentration is a critical factor for determining the abundance of toxic Microcystis population.     

Response in root morphology and nutrient contents of Myriophyllum spicatum to sediment type

Sediment may play an important role during the submerged macrophyte decline in the eutrophication progress. In order to investigate the response in root morphology and nutrient contents of submerged macrophytes Myriophyllum spicatum to sediment, five sediment types were treated and used (five types of sediment were used in the experiment: treatment 1 was nature sediment + sand, a 50:50 (v/v) mixture, treatment 2 was the studied sediment only, treatment 3 was sediment + nitrogen (N, NH₄Cl 400 mg kg^?1), treatment 4 was sediment + phosphorus (P, NaH₂PO₄ 300 mg kg^?1); treatment 5 was sediment + phosphorus (P, NaH₂PO₄ 600 mg kg^?1)). The results show that the root N content was only significantly affected by adding N in sediments and P was elevated by adding N and P. The root mass and its percentage increased at first, the peak values were reached at 35 d, and then decreased. The root growth was restrained by adding sand and N in sediments, root senescence process was delayed at the later experimental time by adding P in sediments. The increase of root volume showed a similar trend to that of root growth, except for plant with P addition where root volume remained high after 35 d. The root volume decreased while the main root number increased significantly by adding sand in sediments. The mean root length and main root diameter were reduced by adding P in sediments. The compatible sediment nutrient condition is necessary to restore submerged macrophytes in a degraded shallow lake ecosystem, and the effect of sediment on the root morphology and nutrient content is one of the important aspects restricting the restoration of submerged macrophytes.     

Factors influencing the return of submerged plants to a clear-water,shallow temperate lake

Lack of submerged vegetation was studied in a small, shallow, alkaline, clear-water lake with high nitrate concentration (mean 9 mg NO₃–N L⁻¹) and profuse filamentous green algae (FGA) (mainly Spirogyra sp.). A laboratory microcosm and two lake enclosure experiments were carried out using Elodea nuttallii (Planchon) St John. E. nuttallii grew about 1.7 times as well in sediment from its place of origin compared with sediment from the lake. Differential water quality had no effect, and neither sediment nor water prevented growth in the lake. Nutrient addition reduced plant growth by more than 55% because of shading from epiphytic filamentous green algae (shoot dry weight versus epiphytic algal dry weight, r = −0.491, P < 0.05). Transplanted Elodea plants grew better in enclosures in the lake than in laboratory conditions with lake water and sediment (P < 0.001, t-test). Rare Elodea individuals in the lake indicate the presence of plant propagules in the lake sediment, but excessive growth of filamentous green algae (summer mean 3.2 g dry weight m⁻²) significantly hamperd plant growth (shoot length reduced from 29 ± S.E.M. 1 to 25 ± 1 cm) and bird herbivory significantly reduced survival (from 82 ± 7 to 40 ± 6%) and shoot growth (from 78 ± 6 to 18 ± 5 cm) and thus eliminates establishment of even modest plant beds. Fish disturbance and sediment stability were not important. Restoration of submerged plants may require reduction of nitrate input, control of filamentous green algae and protection from birds.     

Changes in abundances of Alexandrium tamarense resting cysts after the tsunami caused by the Great East Japan Earthquake in Funka Bay,Hokkaido, Japan

The 2011 Great East Japan Earthquake and the subsequent huge tsunami greatly affected both human activity and the coastal marine ecosystem along the Pacific coast of Japan. The tsunami also reached Funka Bay in northern Japan and caused serious damage to the scallop cultures there, and this tsunami was believed to have affected the coastal environments in the bay. Therefore, we investigated the changes in the spatial abundance and distribution of the toxic dinoflagellates Alexandrium tamarense cysts before the tsunami (August 2010) and after the tsunami (May 2011, August 2011, May 2012 and August 2012) in the bay. Further, monthly sampling was conducted after the tsunami to identify seasonal changes of Alexandrium catenella/tamarense cysts and vegetative cells. Significant increases were observed in the populations of A. catenella/tamarense cysts, comparing the abundances before the tsunami (in August 2010; 70 ± 61 cysts g⁻¹ wet sediment) to those just after it (in May 2011; 108 ± 84 cysts g⁻¹ wet sediment), and both A. tamarense bloom (a maximum density was 1.3 × 10³ cells L⁻¹) and PSP (Paralytic Shellfish Poisoning) toxin contamination of scallops (9.4 mouse unit g⁻¹ was recorded) occurred in the bay. Seasonal sampling also revealed that the encystment of A. tamarense and the supply of the cysts to bottom sediments did not occur in the bay from September to April. These results strongly suggested that the mixing of the bottom sediments by the tsunami caused the accumulation of the toxic A. tamarense cysts in the surface of bottom sediment through the process of redeposition in Funka Bay. Moreover, this cyst deposition may have contributed to the toxic bloom formation as a seed population in the spring of 2011.     

Growth,biomass allocation,and autofragmentation responses to root and shoot competition in Myriophyllum spicatum as a function of sediment nutrient supply

Plant growth, biomass allocation and autofragmentation were investigated in response to root and shoot competition in the submersed macrophyte Myriophyllum spicatum L. growing in two sediment environments. Biomass accumulation and allocation were significantly affected by sediment fertility, with a higher total biomass observed in fertile sediment (average: 4.69 g per plant vs. 1.12 g per plant in infertile sediment). Root-to-shoot ratios were 0.34 and 0.06 in the infertile and fertile sediments, respectively, reflecting the high investment placed on roots under infertile conditions. In the presence of root, shoot, and full competition, whole plant biomass decreased by 18%, 12% and 24% in the infertile sediments, and 23%, 25% and 33% in the fertile sediments, respectively. Root weight ratios (RWRs) increased with root competition by 38% (P < 0.001) and 12% (P = 0.002), while leaf weight ratios (LWRs) decreased with shoot competition by 6% (P = 0.042) and 5% (P = 0.001) in the infertile and fertile sediments, respectively. A total of 406 autofragments were harvested in the fertile sediments, but none were obtained from the infertile sediments. In the control, autofragment number and biomass was 166% and 175% higher compared to the competition treatment. Root and shoot competition resulted in a 21% (P = 0.043) and 18% (P = 0.098) decrease in the autofragment biomass, respectively. These results indicated that M. spicatum responds to different sediment fertility by changing its allocation patterns. Moreover, both root and shoot competition influenced plant growth and autofragmentation, while sediment nutrient availability played an important role in M. spicatum autofragmentation.     

A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams

Anthropogenic modifications of sediment load can cause ecological degradation in stream and river ecosystems. However, in practice, identifying when and where sediment is the primary cause of ecological degradation is a challenging task. Biological communities undergo natural cycles and variation over time, and respond to a range of physical, chemical and biological pressures. Furthermore, fine sediments are commonly associated with numerous other pressures that are likely to influence aquatic biota. The use of conventional, non-biological monitoring to attribute cause and effect would necessitate measurement of multiple parameters, at sufficient temporal resolution, and for a significant period of time. Biomonitoring tools, which use low-frequency measurements of biota to gauge and track changes in the environment, can provide a valuable alternative means to detecting the effects of a given pressure. In this study, we develop and test an improved macroinvertebrate, family-level and mixed-level biomonitoring tool for fine sediment. Biologically-based classifications of sediment sensitivity were supplemented by using empirical data of macroinvertebrate abundance and percentage fine sediment, collected across a wide range of temperate river and stream ecosystems (model training dataset n = 2252) to assign detailed individual sensitivity weights to taxa. An optimum set of weights were identified by non-linear optimisation, as those that resulted in the highest Spearman’s rank correlation coefficient between the index (called the Empirically-weighted Proportion of Sediment-sensitive Invertebrates index; E-PSI) scores and deposited fine sediment in the model training dataset. The family and mixed-level tools performed similarly, with correlations with percentage fine sediment in the test dataset (n = 84) of r_s = −0.72 and r_s = −0.70 p < 0.01. Testing of the best performing family level version, over agriculturally impacted sites (n = 754) showed similar correlations to fine sediment (r_s = −0.68 p < 0.01). The tools developed in this study have retained their biological basis, are easily integrated into contemporary monitoring agency protocols and can be applied retrospectively to historic datasets. Given the challenges of non-biological conventional monitoring of fine sediments and determining the biological relevance of the resulting data, a sediment-specific biomonitoring approach is highly desirable and will be a useful addition to the suite of pressure-specific biomonitoring tools currently used to infer the causes of ecological degradation.     

Response of Potamogeton crispus root characteristics to sediment heterogeneity

Plant growth, biomass allocation, root distribution and plant nutrient content were investigated in the submerged macrophyte Potamogeton crispus growing in heterogeneous sediments. Three experimental sediments heterogeneous in nutrient content and phosphorus release capacity were used: sandy loam with low nutrient content (A), clay with intermediate nutrient content (B), and clay with high nutrient content (C). Biomass accumulation was significantly affected by the sediment type, and was highest in clay C (1.23 mg per plant dry weight) but lowest in sandy loam (0.69 mg per plant dry weight). The root:shoot ratios in treatments A, B and C were 0.30, 0.14 and 0.09, respectively. P. crispus allocated more biomass to roots in sandy loam compared with the other sediments. The average root numbers in sediments A, B and C were 16, 19 and 20, respectively, and the total root lengths in sediments A, B and C were 238.84, 200.36 and 187.21 cm, respectively. Almost 90% of the root biomass was distributed in the 0–15 cm depth in sediments B and C, compared with 64.53% in sediment A. The rank order of plant nitrogen and phosphorus concentrations in the sediment types was C > B > A. These results indicate that both sediment structure and nutrient availability influence the growth and distribution of the root system of P. crispus.     

Effects of phosphorus and nitrogen amendments on the growth of Egeria najas

The effect of nutrient addition on the growth of E. najas was evaluated in a dose response experiment using sand amended with phosphorus (P) and nitrogen (N), and in enrichment trials with N and P amendments to natural sediments. Plants, water and sediment came from lagoons of the Upper Paraná River Floodplain and from Itaipu Reservoir (Brazil). Relative growth rates (RGRs) of E. najas shoots, based on dry mass (DM), varied from 0.03 to 0.060 d⁻¹ for both nutrients. Root:shoot biomass ratios were related to sediment exchangeable P (r = −0.419; P = 0.03) and N (r = −0.54; P = 0.006), however root RGR was not related to sediment nutrient concentrations. When natural sediments were amended with N and P, neither shoot nor root RGRs differed among treatments for substrata from either the reservoir or the floodplain lagoons (P > 0.05). Comparison of nutrient concentrations measured in natural sediments collected from several sites in both the Upper Paraná River Floodplain (range 49–213 μg P g⁻¹ DM; 36–373 μg N g⁻¹ DM) and Itaipu Reservoir (range 43–402 μg P g⁻¹ DM; 7.9–238 μg N g⁻¹ DM) showed that sediment N and P from these systems usually exceeded minimum requirements necessary for E. najas growth, as measured in the dose response experiment. Together, these results indicate that E. najas, at least in early stages of development, responds to sediment nutrient amendments and relies upon bottom sediments to meet its N and P requirements and that for at least two Brazilian ecosystems, growth of this species is not limited by insufficient sediment N or P. Thus, reducing N and P in water is not enough to control E. najas growth in short time periods in these ecosystems.     

Growth responses of Zostera capricorni to estuarine sediment conditions

This study comprised (1) a field survey of intertidal seagrass (Zostera capricorni) biomass, cover and photosynthetic potential and sediment characteristics at a range of contrasting sites in three New Zealand harbours, and (2) a microcosm experiment comparing plant responses to sediments from extant versus historical seagrass sites. The field survey showed that the sediment physico-chemical characteristics were generally consistent with the limited previous reports for Zostera environments, although the total P concentration range was higher (0.08–0.72 mg P g⁻¹). Overall, 52% of variation in seagrass cover was explained by sediment water content (R = 0.54) and organic content (R = −0.56). Twenty-two percent of variation in seagrass biomass was explained by sediment total P and redox potential (both R = −0.35). Intra-harbour seagrass–sediment relationships were more significant (explaining up to 82% of plant variation) but harbour-specific. In the microcosm experiment, threefold higher Z. capricorni biomass was maintained on extant than historical sediments but not conclusively linked to measure sediment characteristics. Overall, the results of this study demonstrate that significant relations can exist between estuarine sediment conditions and Z. capricorni growth responses, and suggest that detrimental change in sediment conditions may be a contributing factor in seagrass decline.     

Density and distribution of seeds in bottom sediments in Zostera marina beds in Ago Bay,central Japan

The density of Zostera marina L. seeds in bottom sediments was examined to study the reproductive patterns of the Z. marina population in Ago Bay, Mie Prefecture, central Japan.Seeds and seed coats were numerous in Tategami, where the annual type of Z. marina grows. In contrast, seeds were scarce in Hamajima, where the perennial type of Z. marina grows. Bottom sediment was sampled with sediment cores at Tategami in November 2004 and March 2005 to examine density and depth distribution of the seeds. Seeds were found as deep as 8 cm, but no deeper. On the other hand, empty seed coats were found as deep as 16 cm in both months. In the upper layers of the sediment to a depth of 8 cm, the average number of seed coats was 7960 ± 2997 m⁻² in November and 16,318 ± 2922 m⁻² in March. Deeper than 8 cm, the number of seed coats gradually decreased owing to decomposition, and none was found below 16 cm. We used the density of reproductive shoots and number of seeds per spadix in Tategami to estimate the fate of seeds and seed coats of the annual type of Z. marina in bottom sediments: out of the 6000 seeds m⁻² produced annually, 72% disappears from the stand and 28% is buried locally. The density and distribution of Z. marina seeds are among the most important factors in maintenance and propagation of the annual population at Tategami.     

Growth responses of Zostera capricorni to estuarine sediment conditions

This study comprised (1) a field survey of intertidal seagrass (Zostera capricorni) biomass, cover and photosynthetic potential and sediment characteristics at a range of contrasting sites in three New Zealand harbours, and (2) a microcosm experiment comparing plant responses to sediments from extant versus historical seagrass sites. The field survey showed that the sediment physico-chemical characteristics were generally consistent with the limited previous reports for Zostera environments, although the total P concentration range was higher (0.08–0.72 mg P g⁻¹). Overall, 52% of variation in seagrass cover was explained by sediment water content (R = 0.54) and organic content (R = −0.56). Twenty-two percent of variation in seagrass biomass was explained by sediment total P and redox potential (both R = −0.35). Intra-harbour seagrass–sediment relationships were more significant (explaining up to 82% of plant variation) but harbour-specific. In the microcosm experiment, threefold higher Z. capricorni biomass was maintained on extant than historical sediments but not conclusively linked to measure sediment characteristics. Overall, the results of this study demonstrate that significant relations can exist between estuarine sediment conditions and Z. capricorni growth responses, and suggest that detrimental change in sediment conditions may be a contributing factor in seagrass decline.     

Short-time response in root morphology of Vallisneria natans to sediment type and water-column nutrient

Rooted submerged macrophytes can absorb significant amounts of nutrients from both sediment and water. We investigated root morphology of Vallisneria natans in mesocosm plastic bins, in response to three types of sediment (sandy loam, clay, and a 50:50 (v/v) mixture of the two sediments) and two levels of water-column nutrient (well water and nutrient medium). Compared to the plants grown in the clay or mixed sediments, root diameter decreased (0.39–0.41 versus 0.36–0.37 mm) but total root length per plant increased (0.87–1.27 versus 1.14–1.62 m) when grown in sandy loam. Increase of nutrient availability in water column led to decreased specific root length (306–339 versus 258–281 m g⁻¹). However, both sediment type and water-column nutrient had no impacts on root number (ranged from 19 to 24 number of roots per plant). Root weight ratio, root:leaf mass ratio and root:leaf length ratio generally decreased with enhanced nutrient availability in sediment or water. Plant growth was affected by sediment type alone (P < 0.05), rather than water-column nutrient (P > 0.05). However, plant N and P contents were significantly impacted by both sediment type (P ≤ 0.001) and water-column nutrient (P < 0.05). Increase of nutrient availability in sediment or water led to increased plant N (ranged from 2.47 to 4.77 mg g⁻¹) and P concentrations (ranged from 42.8 to 62.0 mg g⁻¹). These results indicate that considerable variation in root morphology of V. natans exists in response to the fertility of the sediment it is rooted in.     

Predominance of terrestrial organic matter in sediments from a cyanobacteria- blooming hypereutrophic lake

Although an understanding of the quantity and quality of sedimentary organic matter (SOM) pools is necessary to design sound environmental management strategies for lacustrine systems, the characterization of organic matter sources and the assessment of their relative contributions to eutrophic and inland lake sediments remain insufficient. In this study, the contribution of potential organic matter sources to sediments in shallow and hypereutrophic lake Taihu, China was assessed on the molecular level using source-specific fatty acid biomarkers. The results indicated that SOM was composed mainly of terrestrial plants with a maximal contribution of 45.3 ± 2.4% to the total organic carbon, which accounted for approximately 66% among the determined organic matter sources. Evidence suggests the terrestrial plants remained in a fresh state in surface sediments: the correlation (R² = 0.62, p < 0.05) between bacterial and terrestrial plant carbon was strong. On the other hand, aquatic plant and bacterial carbon contributed 5–15% to the total organic carbon, which was followed by the faint contribution (<5% of total organic carbon) of algae-derived organic carbon including cyanobacteria, diatoms, and dinoflagellates. The results provided details of the contributions of SOM sources, illustrating the usefulness of fatty acid biomarkers in discriminating organic matter sources within lake environments. Although organic matter sources of sediments varied in spatial and temporal patterns, the strong correlation between terrestrial plant and total organic carbon (R² = 0.60, p < 0.05) indicates that terrestrial plants were the dominant source in lake sediments.     

Enzymatic hydrolysis of organic phosphorus in river bed sediments

Enzymatic hydrolysis of phosphorus (P) in bed sediments is an important process that maintains bioavailable P in the river systems. The P bioavailability is the criterion for assessing the eutrophication potential in rivers and streams. The objective of this research was to determine potential bioavailability of organic P (OP) in the Bronx River bed sediments using native phosphatases (NPase) and phosphodiesterase (PDEase) hydrolysis. The bed sediments collected in summer 2006 and 2007 were incubated at 37 °C for 6 h at pH 7.5 with NPase. The results showed that NPase hydrolyzed a substantial amount of OP (up to 76%) under favorable temperature and pH, indicating OP could be hydrolyzed under increased temperature, and in turn increase in P availability in the river. Similarly, the resulting form sediments incubated with PDEase at 37 °C and pH 8.8 showed that up to 82% of OP could be hydrolyzed. Strong correlations between percentage of OP hydrolyzed by PDEase and organic matter (OM) were observed for sediments collected in 2006 (r = 0.745; p ≤ 0.01) and 2007 (r = 0.724; p ≤ 0.01), indicating PDEase hydrolysable P is mainly associated with OM. It is indicative that local hydro-climatic changes such as temperature increase and pH variations could hydrolyze a substantial amount of OP and increase bioavailable P in the water column, resulting in a potential threat to the river ecosystems.     

Distribution and survival of faecal indicator bacteria in the sediments of the Bay of Vidy,Lake Geneva,Switzerland

The purpose of this study was to determine the concentrations and the horizontal distribution of faecal indicator bacteria (FIB) including Escherichia coli and Enterococcus sp. in the bottom sediments of the Bay of Vidy, City of Lausanne, Switzerland. A vertical distribution of FIB in sediments near the municipal wastewater treatment plant (WWTP) outlet was evaluated and their persistence in those sediments was monitored for a period of 90 days. High FIB levels were measured in the sediments sampled near the WWTP outlet pipe and the mouth of the Chamberonne River, at concentrations ranging between 10⁵ and 10⁷ CFU 100 g^?1. FIB levels at 10 cm depth in the sediments near the WWTP outlet pipe ranged between 10⁴ and 10⁵ CFU 100 g^?1, and were still detected in the top 6 cm after 90 days. Results of this study indicate that freshwater sediments of the Bay of Vidy constitute a reservoir of faecal indicator bacteria, which can persist in certain areas of the bay. Possible resuspension of FIB and pathogens may affect water quality and may increase health risks to sensitive populations during recreational activities. FIB survival in sediments for long periods is of considerable significance for the understanding of microbial pollution in water and for the management of risk at specific recreational coastal sites.     

Evaluation of quantitative recovery of bacterial cells and DNA from different lake sediments by Nycodenz density gradient centrifugation

While purified bacterial cells and DNA – the signature of life – from soil and sediment matrices have been extensively studied in a wide range of environments and in different microbial ecosystems, the paucity of data on DNA extraction from contaminated sediments emphasizes the need for further research on the isolation and quantification of bacterial cells and DNA in sediments. Consequently, the Nycondez gradient centrifugation method was applied to extract bacterial cells from contaminated and uncontaminated sediments. Quantitative estimates of recovered bacterial cells were obtained from direct counts performed using DAPI (4′,6′-diamino-2-phenylindole hypochloride) staining couples with fluorescence microscopy and indirect counts (colony-forming units). The estimation was improved by using an efficient method of comparing sediment types composed of quantifying bacterial densities in three steps: S₁ the initial freshwater sediments; S₂ the first supernatant recovered after mixing the sediments with sodium hexametaphosphate solution followed by centrifugation; and S₃ the extracted cells. Total and extracellular DNA were extracted and quantified in each of the three steps. Additional analysis of faecal indicator bacteria (FIB) including E. coli and Enterococcus (ENT) was also performed in each step. The results display considerable variability in the quantity of bacteria cells depending on sediment type, ranging from 1.2 × 10⁵ to 6.2 × 10⁹ cell g^?1 dry sediments. The treatment with sodium hexametaphosphate solution (2%) leads to the desorption of bacterial populations which were firmly adsorbed on contaminated sediment surfaces resulting in more than 90% of the FIB being recovered. The Nycondez density gradient centrifugation method makes it possible to extract bacterial cells from freshwater sediments without extracellular DNA so it is ideal for metagenomic analysis of bacteria.     

Bromophenol accumulation and sediment contamination by the marine annelids Notomastus lobatus and Thelepus crispus

The occurrence of bromophenols in Notomastus lobatus and Thelepus crispus and associated sediment and porewater was determined. 4-Bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol were identified in N. lobatus with the highest concentrations occurring in the anterior and posterior abdomen and substantially less in the thorax (345, 209, and 6.6 μg/ml of worm, respectively). The concentration of dibromobenzyl alcohol was highest in the tail (last 15 setigers) of T. crispus (1.02 mg/ml of worm), but did not differ among body parts as the bromophenols did in N. lobatus. Concentrations in sediments were significantly reduced from those in the worms and decreased from the inner burrow lining out to 5 cm from N. lobatus burrows. Similarly for T. crispus, concentrations of dibromobenzyl alcohol in the surrounding sediments and porewater were low and increased with proximity to the burrow. For both species, concentrations in surface sediment (upper 1 cm) did not differ from those at 6 cm depth. Several lines of evidence indicate that these compounds are produced by the worms and hence their presence in sediments is derived from the worms. The contamination of sediment by these bromophenols has important implications for the structure and activities of benthic-associated communities.     

Algicidal and growth-inhibiting bacteria associated with seagrass and macroalgae beds in Puget Sound,WA, USA

The algicidal and growth-inhibiting bacteria associated with seagrasses and macroalgae were characterized during the summer of 2012 and 2013 throughout Puget Sound, WA, USA. In 2012, Heterosigma akashiwo-killing bacteria were observed in concentrations of 2.8 × 10⁶ CFU g⁻¹ wet in the outer organic layer (biofilm) on the common eelgrass (Zostera marina) in north Padilla Bay. Bacteria that inhibited the growth of Alexandrium tamarense were detected within the biofilm formed on the eelgrass canopy at Dumas Bay and North Bay at densities of ∼10⁸ CFU g⁻¹ wet weight. Additionally, up to 4100 CFU mL⁻¹ of algicidal and growth-inhibiting bacteria affecting both A. tamarense and H. akashiwo were detected in seawater adjacent to seven different eelgrass beds. In 2013, H. akashiwo-killing bacteria were found on Z. marina and Ulva lactuca with the highest densities of ∼10⁸ CFU g⁻¹ wet weight at Shallow Bay, Sucia Island. Bacteria that inhibited the growth of H. akashiwo and A. tamarense were also detected on Z. marina and Z. japonica at central Padilla Bay. Heterosigma akashiwo cysts were detected at a concentration of 3400 cysts g⁻¹ wet weight in the sediment from Westcott Bay (northern San Juan Island), a location where eelgrass disappeared in 2002. These findings provide new insights on the ecology of algicidal and growth-inhibiting bacteria, and suggest that seagrass and macroalgae provide an environment that may influence the abundance of harmful algae in this region. This work highlights the importance of protection and restoration of native seagrasses and macroalgae in nearshore environments, in particular those regions where shellfish restoration initiatives are in place to satisfy a growing demand for seafood.     

Immune mobilization of autologous blood progenitor cells: direct influence on the cellular subsets collected

Background aimsA phase I trial examined the ability of immunotherapy to mobilize progenitor and activated T cells.MethodsInterleukin (IL)-2 was administered subcutaneously for 11 days, with granulocyte (G)-colony-stimulating factor (CSF) (5 mcg/kg/day) and granulocyte–macrophage (GM)-CSF (7.5 mcg/kg/day) added for the last 5 days. Leukapheresis was initiated on day 11. Thirteen patients were treated (myeloma n = 11, non-Hodgkin's lymphoma n = 2).ResultsToxicities were minimal. IL-2 was stopped in two patients because of capillary leak (n = 1) and diarrhea (n = 1). Each patient required 2.5 leukaphereses (median; range 1–3) to collect 3.2 × 10⁶ CD34⁺ cells/kg (median; range 1.9–6.6 × 10⁶/kg). Immune mobilization increased the number of CD3⁺ CD8⁺ T cells (P = 0.002), CD56⁺ natural killer (NK) cells (P = 0.0001), CD8⁺ CD56⁺ T cells (P = 0.002) and CD4⁺ CD25⁺ cells (P = 0.0001) compared with cancer patients mobilized with G-CSF alone. There was increased lysis of myeloma cells after 7 days (P = 0.03) or 11 days (P = 0.02). The maximum tolerated dose of IL-2 was 1 × 10⁶ IU/m²/day.ConclusionsImmune mobilization is well tolerated with normal subsequent marrow engraftment. As cells within the graft influence lymphocyte recovery, an increased number of functional lymphocytes may result in more rapid immune reconstitution.     

Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia,Southern Mediterranean Sea)

A high spatial resolution sampling of Alexandrium pacificum cysts, along with sediment characteristics (% H₂O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotyping of cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum. The toxin profile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N-sulfocarbamoyl toxins C1 (9.82 pg toxin cell⁻¹), the GTX6 (3.26 pg toxin cell⁻¹) and the carbamoyl toxin Neo-STX (0.38 pg toxin cell⁻¹). The latter represented only 2.8% of the total toxins in this strain.High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63 μm were examined as a favorable potential seedbed for initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.