Stable patterns in size structure of a phytoplankton species of Lake Kinneret

The aim of the study was a search for typical structure patterns of phytoplankton assemblages, based on the long-term dynamics analysis. As a test case we used the interannual phytoplankton variability of Lake Kinneret (Israel). The dominant phytoplankton species (Peridinium gatunense) structure was presented as the frequency-weighted taxonomic size spectrum (TSS) which describes the size distribution of the operational taxonomic unit (OTUj) occurrence frequencies. Using 24 years monitoring data, the TSS annual patterns of P. gatunense were compared. Typical persistent TSS patterns were evident even during years of pronounced deviations from the typical patterns of phytoplankton biomass dynamics and species composition. By correlation analysis, hierarchical cluster analysis and ANOVA the TSS variability was quantified and compared. While the TSS general shape was almost constant, its amplitude variations allowed us to distinguish between three levels of annual bloom intensity. Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users     

Selectivity and grazing impact of microzooplankton on phytoplankton in two subtropical semi-enclosed bays with different chlorophyll concentrations

Microzooplankton grazing rates were compared between two sites (S1 and S2) in the coastal seas of eastern Hong Kong with similar physio-chemical parameters, but different chlorophyll concentrations. During the period from March 2007 to January 2008, six sets of dilution experiments, combined with high performance liquid chromatography and phytoplankton size fractionation (< 200 μm, < 20 μm and < 5 μm), were carried out to study the microzooplankton grazing rate on phytoplankton of different taxonomic groups and sizes. Although total chlorophyll a concentrations were much higher in S1 (4.98-18.42 μg l^− 1) than in S2 (0.29-1.68 μg l^− 1), size composition of phytoplankton was relatively similar between the two sites. Measured as chlorophyll a, phytoplankton growth rates (− 0.84-1.91 d^− 1 in S1; 0.03-2.85 d^− 1 in S2) and microzooplankton grazing rates (0.00-2.26 d^− 1 in S1; 0.00-1.49 d^− 1 in S2) for all three size fractions were similar between the two bays. Phytoplankton growth rates and microzooplankton grazing rates measured as other pigments for phytoplankton of different size fractions did not show strong variations. Microzooplankton grazing impact, expressed as the ratio of microzooplankton grazing rate to phytoplankton growth rate, was generally higher in S1 than in S2, although the difference was not statistically significant. High microzooplankton grazing impact on alloxanthin (1.00-45.85) suggested strong selection toward cryptophytes. Our results provided no evidence for size selective grazing on phytoplankton by microzooplankton.     

A Short-Term Study of Vertical and Horizontal Distribution of Zooplankton During Thermal Stratification in Lake Kinneret,Israel

This study documents for the first time both vertical and horizontal distribution patterns of the zooplankton community in Lake Kinneret during the period of thermal stratification. The zooplankton distribution patterns were explored in relation to abiotic (temperature, oxygen) and biotic (picocyanobacteria, ciliates, flagellates, phytoplankton, fish) environmental gradients. Sampling was carried out on 6–7 July 1992 at five stations and six depths from nearshore to offshore. Zooplankton abundance and biomass varied from 5 to 267 ind. l^–1(mean: 95 ind. l^–1), and from 0.1 to 65 d.w. mg m^–3(mean: 24 d.w. mg m^–3). Zooplankton taxonomic groups (Rotifera, Cladocera, Cyclopoida, Calanoida) and size classes (micro-, meso- and macrozooplankton) showed peaks of maximal density and biomass in the epilimnetic and metalimnetic strata (5 and 14 m). Depth, accounting for 31–39% of total spatial variation, reflected the vertical distribution of zooplankton in relation to temperature and oxygen declines, and the higher concentration of food resources (protists and phytoplankton) in the epilimnion and metalimnion. Onshore–offshore distance, accounting for 17–22% of the total spatial variance, reflected different distribution patterns shown among zooplankton groups and size classes. The macrozooplankton (Copepoda, Cladocera) was more abundant offshore, whereas microzooplankton (Rotifera and nauplii) predominated nearshore. These horizontal distribution patterns were related to small increases in temperature and phytoplankton biomass, and higher concentrations of fish in the littoral zone. Although limited to a short temporal scale, our study indicated that zooplankton spatial distribution in Lake Kinneret during the period of thermal stratification was related to physicochemical, food and predation factors, manifested differently along the vertical and nearshore–offshore gradients.     

Differences in cell viabilities of phytoplankton between spring and late summer in the northwest Pacific Ocean

Cell viabilities of phytoplankton in the Oyashio and Kuroshio-Oyashio transition regions of the northwest Pacific Ocean were examined in September 2003 (late summer) and May 2005 (spring) using a membrane permeability test. Specific lysis rates of the phytoplankton during late summer were also assessed by an esterase activity assay. In late summer, cyanobacteria Synechococcus spp. were > 2 × 10⁴ cells ml^− 1 and numerically dominated the phytoplankton communities. The cell viabilities of Synechococcus spp. and eukaryotic ultraphytoplankton (< 10 μm in size) were 60-79% and 26-41% in surface waters, respectively. The specific lysis rates of the phytoplankton were 0.12-0.67 d^− 1 in late summer. By contrast, in spring, eukaryotic cells were predominant in the phytoplankton communities. The cell viabilities of surface eukaryotic ultraphytoplankton in spring were > 70% and significantly higher than those in late summer. During spring, Synechococcus spp. only occurred with < 1 × 10⁴ cells ml^− 1 in the Kuroshio-Oyashio transition region, and their viabilities were 80%. In the Oyashio region where a spring diatom bloom developed, the viability of fucoxanthin-containing algae (mainly diatoms and prymnesiophytes) was ca. 90%. These results suggested that the cell viability of phytoplankton could vary seasonally with their community structure in the study area. The phytoplankton cell death in late summer was particularly significant for their loss process and could support the microbial food webs by supplying dissolved organic carbon (DOC) derived from the dead cells.     

Factors affecting the performance of membrane bioreactor for piggery wastewater treatment

This study was conducted to identify the factors affecting the performance of membrane bioreactor (MBR) for piggery wastewater treatment. The change of organic and nitrogen concentrations in piggery wastewater was studied to investigate the treatment efficiency. The increase of COD, BOD and NH₃–N from 1150 to 2050 mg/L, 683 to 1198 mg/L and 154 to 248 mg/L has led to the decrease of treatment efficiency. Removal efficiencies of COD, BOD and NH₃–N have decreased from 96.0% to 92.0%, 97.0% to 92.7% and 93.2% to 69.5%, respectively. The effects of biomass characteristics on membrane fouling were determined based on Pearson’s correlation coefficient (r_p). It was found that MLSS had a negative correlation with permeate flux (r_p = −0.745, at significant level of 0.05) while sludge floc size a positive correlation (r_p = 0.731, at significant level of 0.05). MLSS and sludge floc size were found to be the dominant factors that controlled the membrane filterability while sludge viscosity, EPS, SMP and SV₃₀ have taken as the sub-factors affecting membrane fouling.     

Influence of cell equivalent spherical diameter on the growth rate and cell density of marine phytoplankton

The maximal growth rates (μ_max) of 8 species of marine phytoplankton were studied in detail. A Logistic growth model was used to describe the growth process of phytoplankton and the averaged plotting correlation coefficient was 1.00 ± 0.01 (mean ± standard deviation). The size distribution of phytoplankton could be well represented by single or combined Gaussian distribution functions. The size distribution of phytoplankton was investigated by daily analysis, and the variation of the median equivalent spherical diameter (MESD) was recorded. The size of algal cells varied throughout the process of population growth, and the size distribution characteristic of the two species of pyrrophytes investigated also changed during the growth process. The relation between maximum growth rate and MESD could be expressed by the equation μ_max = a * MESD^b (where μ_max is the maximum specific growth rate, MESD is the median equivalent spherical diameter, and a and b are constants equal to 2.10 × 10⁵ and − 1.15, respectively), estimated by nonlinear regression analysis with the allometric function. The dependence of maximum cell density on algal MESD was also investigated and the relationship B_f = 1.56 × 10⁷ MESD^− 1.20 was obtained (where B_f is the maximum cell density).     

Human plasma phospholipid transfer protein specific activity is correlated with HDL size: Implications for lipoprotein physiology

To gain further insights into the relationship between plasma phospholipid transfer protein (PLTP) and lipoprotein particles, PLTP mass and phospholipid transfer activity were measured, and their associations with the level and size of lipoprotein particles examined in 39 healthy adult subjects. No bivariate correlation was observed between PLTP activity and mass. PLTP activity was positively associated with cholesterol, triglyceride, apo B and VLDL particle level (r_s = 0.40–0.56, p ≤ 0.01) while PLTP mass was positively associated with HDL-C, large HDL particles, and mean LDL and HDL particle sizes (r_s = 0.44–0.52, p < 0.01). Importantly, plasma PLTP specific activity (SA) was significantly associated with specific lipoprotein classes, positively with VLDL, IDL, and small LDL particles (r_s = 0.42–0.62, p ≤ 0.01) and inversely with large LDL, large HDL, and mean LDL and HDL particle size (r_s = − 0.42 to − 0.70, p ≤ 0.01). After controlling for triglyceride levels, the correlation between PLTP mass or SA and HDL size remained significant. In linear models, HDL size explained 45% of the variability of plasma PLTP SA while triglyceride explained 34% of the PLTP activity. Thus, in healthy adults a significant relationship exists between HDL size and plasma PLTP SA (r_s = − 0.70), implying that HDL particle size may modulate PLTP SA in the vascular compartment.     

Application of a new multi-metric phytoplankton index to the assessment of ecological status in marine and transitional waters

Patterns of phytoplankton size spectra variation with gradients of environmental stress have been observed in freshwater, transitional waters and marine ecosystems, driving the development of size spectra based assessment tools.In this study, we have tested on transitional and coastal waters a new Index of Size spectra Sensitivity of Phytoplankton (ISS-Phyto), which integrates simple size spectra metrics, size class sensitivity to anthropogenic disturbance, phytoplankton biomass (chlorophyll a) and taxonomic richness thresholds. ISS-Phyto has been tested both among and within ecosystems along pressure gradients based on expert view assessment; the adequacy of symmetric and both left and right asymmetric models of phytoplankton size class sensitivity have been compared.The results showed that ISS-Phyto consistently discriminated between anthropogenic and natural disturbance conditions. Left asymmetric models of size spectra sensitivity, assuming greater disturbance tolerance with respect to eutrophication and organic enrichment of increasingly large size classes, showed the best fit comparing all ecosystems; in three of the four considered ecosystems (Varna, Helsinki, Mompás-Pasaia), they seemed to discriminate best between different levels of disturbance also within ecosystems. Moreover, they demonstrated significant and inverse patterns of variation along the overall pressure gradient as well as along the inorganic phosphorus (DIP), chlorophyll a and trophic index (TRIX) gradients.Therefore, ISS-Phyto, originally developed for transitional waters, seems to be an adequate assessment tool of ecological status also in coastal marine waters; moreover, it seems adequate to describe within ecosystem disturbance gradients. Hence, ISS-Phyto helps to understand the relationships between anthropogenic impact and ecosystem response from the individual point of view, with reference to the simple parameter of body size.     

The effects of temperature increases on a temperate phytoplankton community — A mesocosm climate change scenario

Prior to the spring bloom in 2003 and 2004, batch temperature experiments of approximately 3 weeks' duration were carried out in land-based mesocosms in at the Espeland field station (Norway), with temperatures on average increased ~ 2.7-3 °C (T1) and ~ 5.2-5.6 °C (T2) above in situ fjord temperature (RM). The development in the chlorophyll concentrations showed an earlier bloom as a response to increased temperatures but the carbon biomass showed that the warmest treatment yielded the lowest biomass. This study indicates that a part of the relationship between temperature and spring bloom timing stems from a temperature-induced change in phytoplankton algal physiology (the efficiency of photosystem II, F_v/F_m, and growth rates, µ_max), i.e. a direct temperature effect. Data analysis performed on microscope identified and quantified species did not show a significant temperature influence on phytoplankton community composition. However, the HPLC data indicated that temperature changes of as little as 3 °C influence the community composition. In particular, these data showed that peridinin-containing dinoflagellates only increased in abundance in the heated mesocosms and that a prasinophycean bloom, which was undetected in the microscope analyses, occurred prior to the blooms of all other phytoplankton classes in all treatments. The microscope analyses did reveal a temperature effect on individual species distribution patterns. Thalassionema nitzschioides was more abundant in the warm treatments and, in the warmest treatment, the spring bloom forming Skeletonema marinoi comprised a smaller proportion of the diatom community than in the other treatments.     

The relationship between water availability and anatomical characters in Carex hirta

The effects of edaphic moisture in anatomical characters were evaluated in two different populations of Carex hirta L. with three watering treatment for 6 months to evaluate stability, and determined taxonomic value. Water availability increased (p < 0.001) leaf thickness from 239 to 289 μm, metaxylem vessel diameter from 17 to 23 μm, air cavity size from 10 to 24% and adaxial epidermal cell height from 18 to 34 μm, and abaxial from 11 to 16 μm, adaxial epidermal cell length from 54 to 105 μm, and abaxial from 35 to 86 μm, and adaxial epidermal cell width from 20 to 33 μm, and abaxial from 15 to 23 μm. Stomatal index and the number of cells in the girder of sclerenchyma did not vary with water availability, hence these traits have taxonomic value. Other characters (the length and amplitude of wall undulations in the epidermal cells, the number of bulliform cells) have a doubtful relation with water availability, because they are variable even in constant homogeneous conditions.     

Effect of essential dietary fatty acids on egg production and hatching success of the marine copepod Temora longicornis

The calanoid copepod Temora longicornis and its food (seston of size < 200 μm) was sampled during three successive seasons (2002-04) in the Trondheimsfjord, Central Norway. Egg production (24 h) and hatching success (72 h) was determined by incubation experiments, and the essential fatty acid (EFA) content of their in situ food was analysed. The dominant EFA in the seston were DHA (22:6n-3) and EPA (20:5n-3), whereas ARA (20:4n-6) were present in low quantities. Egg production and hatching success was relatively low during early spring and late autumn (~ 10 eggs female^- 1 day^- 1 and ~ 30%), and relatively high during summer. Spring phytoplankton, dominated by diatoms, contained low amounts of DHA. Dinoflagellates, small flagellates, and ciliates dominated during summer, when a high content of DHA was recorded.The rate of egg production of T. longicornis did not show any relationship with food concentration (r² = 0.003), but was positively correlated to temperature, although not statistically significantly (r² = 0.48, p = 0.05). The quantitative and percent DHA contents of the food was significantly related to the rate of egg production (r² = 0.96 and 0.95, respectively, p < 0.001), but no such relationship were observed for the quantitative or percent content of EPA and ARA in the seston. The egg production of T. longicornis during May-August was 43-47 eggs female^- 1 day^- 1, with dietary DHA contents higher than 7-8 mg DHA g^- 1 DW. Also the hatching success of T. longicornis was positively correlated to the quantitative content of DHA in the diet (r² = 0.88), but hatching was also inversely related to the percentage ARA (r² = 0.84). The maximum hatching success was found when the ARA content was < 0.15% of total fatty acids and the DHA:ARA ratio was > 50. The conclusion that DHA most strongly affected egg production whereas ARA affected hatching, fit well with earlier findings for fish. Our results do not exclude that toxic aldehydes interact with reproduction of calanoid copepods when diatoms are present, but we observed a consistent pattern where dietary DHA and ARA alone explained a majority of the variability in egg production and hatching of T. longicornis.     

Factors controlling vegetation structure in peatland lakes—Two conceptual models of plant zonation

Two conceptual models of plant zonation in peatland lakes are given. The first represents vegetation on slightly sloping substrate (N < 0.2) in shallow and relatively large lakes. The vegetation is not diverse (H′ = 0.0 ± 0.01). The frequency and biomass of the dominant (Sphagnum denticulatum) correlate positively with lake size, and negatively with depth and substrate slope. They are also correlated with water transparency and water color (r = −0.53), concentrations of total organic carbon (r = −0.43), Ca²⁺ (r = 0.40) and humic acids (r = −0.46), and redox potential (r = 0.44). The second model represents vegetation on steep peat walls (N > 0.3) in deep, usually small lakes. Plants occur only on the upper part of the peat wall or form a multispecies curtain hanging from the lip of peat at the top. Species diversity in this scenario is higher (H′ = 0.18 ± 0.17). The curtains usually are composed of mosses such as Warnstorfia exannulata, S. cuspidatum and S. riparium, and vascular plants are rare. The frequency and biomass of bryophytes in this type of structure are related to substrate slope (r = 0.56), lake depth (r = 0.56), Ca²⁺ concentration (r = −0.69) and water color (r = −0.51). In both models, plant biomass is correlated with temperature (r = −0.78), irradiance (r = −0.64) and water oxygenation (r = −0.54).     

Decomposition and nutrient release in halophytes of a Mediterranean salt marsh

This study dealt with the decomposition and nutrient release from the halophytes Atriplex portulacoides, Arthrocnemum macrostachyum, Limoniastrum monopetalum, and Spartina densiflora, the dominant species in the Castro Marim salt marsh, Portugal. Environmental effects on decomposition were also assessed. The study was carried out for one year using the in situ litterbag technique. S. densiflora showed a lower decomposition rate (k = 0.003 day⁻¹) than the other study species (k = 0.005-0.009). Study species showed similar decomposition patterns, that is, the weight loss mostly occurred during the autumn-winter period (study beginning in November). This indicates that temperature in this period did not hamper the decomposition process. The decomposition rate was positively affected by the initial N concentration (r² = 0.87, P < 0.05) and negatively by the C:N ratio (r² = 0.86, P < 0.05) in decomposing materials. At the end of the study, S. densiflora and L. monopetalum, the species with lower initial N concentrations, retained much higher proportion of initial N (89-109%) than the others (5-14%). Also, S. densiflora with the lowest P concentration retained higher proportion of initial P (48%) than the others (5-20%). Release of K and Mg were also slower from S. densiflora and was associated with their initial low concentration in this species. The lowest Mn release was observed from A. macrostachyum and also in relation to the lowest initial concentration. Our study supports the hypothesis that decomposition patterns of marsh species are mostly associated with differences regarding their morphology and chemical composition. Given the higher resistance of S. densiflora to decomposition, its progressive spreading may result in accumulation of organic detritus overtime in invaded salt marshes.     

Quantifying the ecological stability of a phytoplankton community: The Lake Kinneret case study

The widely used term “stability” has multiple meanings and is rarely quantified in limnological studies. The main objective of this study was to develop an approach for quantifying the stability of a phytoplankton community using Lake Kinneret as a case study. It is a first attempt of calculating an index of stability for each of the five main taxonomic groups of the Kinneret phytoplankton (Bacillariophyta, Chlorophyta, Cryptophyta, Cyanophyta and Dinophyta), and for the entire community. A simple statistical approach to calculate the stability index was devised, using phytoplankton wet-weight biomass as the parameter being manipulated. The period 1970–1979 was selected as a reference period. The following stability indices were established and applied (each at three time scales): (1) a stability index for each of five main taxonomic groups; (2) a combined index of the stability, aggregating the stabilities of the individual taxonomic groups and (3) a stability index of entire community based on total phytoplankton biomass. The dynamics of these indices during 1969–2011 were examined. Destabilization of the community structure was triggered by an increase in the variability of Bacillariophyta biomass shortly after the reference period, in 1981–1983. Only 10 years later, the community destabilization become associated with progressively increasing biomass of Cyanobacteria. Dinophyta were the last to destabilize in the mid 1990s. Despite notable changes in the community structure, the total phytoplankton biomass remained relatively stable. Therefore, in 1969–2011 the stability index based on total phytoplankton biomass was higher than the combined index based on the stabilities of the individual taxonomic groups. Only weak relationships were found between the stability index values and potential driving forces (lake water level fluctuations and nutrient loads). While this approach was applied to Lake Kinneret, the concept presented is not lake specific and could be applied to other lakes.     

Linking phytoplankton community metabolism to the individual size distribution

Quantifying variation in ecosystem metabolism is critical to predicting the impacts of environmental change on the carbon cycle. We used a metabolic scaling framework to investigate how body size and temperature influence phytoplankton community metabolism. We tested this framework using phytoplankton sampled from an outdoor mesocosm experiment, where communities had been either experimentally warmed (+ 4 °C) for 10 years or left at ambient temperature. Warmed and ambient phytoplankton communities differed substantially in their taxonomic composition and size structure. Despite this, the response of primary production and community respiration to long‐ and short‐term warming could be estimated using a model that accounted for the size‐ and temperature dependence of individual metabolism, and the community abundance‐body size distribution. This work demonstrates that the key metabolic fluxes that determine the carbon balance of planktonic ecosystems can be approximated using metabolic scaling theory, with knowledge of the individual size distribution and environmental temperature.     

Study on the granular characteristics of starches separated from Chinese rice cultivars

Granule size distribution, the relative crystallinity, morphology and thermal degradation of starches from 10 different non-waxy rice cultivars were measured in present study. The relationships between granular structure and thermogravimetric parameters of tested starches were evaluated using Pearson correlation analysis. The range of median size for rice starches was 6.23-7.81 μm. The relative crystallinity of 10 non-waxy rice starches ranged from 20.4% to 33.4%. The range of activation energy from different rice starches was between 155.6 and 201.5 kJ/mol. The Pearson correlation results showed that the relative crystallinity was positively correlated (r = 0.6750, p < 0.05) with the percentage of branch chains with DP12-23. Furthermore, the activation energy of the rice starches showed a positive correlation (r = 0.7903, p < 0.01) with relative crystallinity.     

Ovine IgA-reactive proteins from Teladorsagia circumcincta infective larvae

Infection of small ruminants with Teladorsagia circumcincta has, until now, been controlled using a combination of pasture management and frequent anthelmintic treatments. Resistance to the commonly used anthelmintics has driven research into the development of a subunit vaccine, encouraged by the demonstration of development of protective immunity in sheep following exposure to this parasite. Local immune effectors in the abomasum, in particular IgA, are thought to play important roles in naturally- and experimentally-acquired immunity. L3s represent the first contact of this pathogen with the host immune system and, herein, the presence of L3 antigen-specific IgA was demonstrated in abomasal mucus from immune sheep. This antibody source was used to immunoaffinity purify and identify IgA-reactive molecules present in L3s. We identified 155 different proteins in this way, including a number of activation-associated secretory proteins, venom allergen-like-type proteins, detoxifying enzymes, galectins and a suite of other potential vaccine candidate molecules. Levels of immunoaffinity-enriched L3 antigen-specific IgA in gastric lymph from previously-infected sheep were statistically significantly higher (P = 0.004) than those measured in helminth-free sheep and a statistically significant negative correlation (P = 0.005, r_s = −0.565) was identified between immunoaffinity-enriched L3 antigen-specific IgA levels in efferent gastric lymph and total T. circumcincta burden measured at necropsy. In addition, a statistically significant positive correlation (P = 0.007, r_s = 0.534) was measured between immunoaffinity-enriched L3 antigen-specific IgA levels in efferent gastric lymph and the percentage of inhibited L4s enumerated at necropsy. These results indicate that the purified antigens contain components that could be strongly considered as vaccine candidates.     

Food acquisition responses of the suspension-feeding bivalve Placopecten magellanicus to the flocculation and settlement of a phytoplankton bloom

In situ technologies were employed to monitor suspended particle flocculation and floc settlement and utilization by a cohort of sea scallops (Placopecten magellanicus) during the 2000 spring phytoplankton bloom in Bedford Basin, Nova Scotia, Canada. The objectives were to determine the effect of bloom flocculation and settling on food acquisition and utilization by scallops, and to assess the potential role of flocculation in enhancing the bioavailability of trophic resources and particle-reactive contaminants to bivalve filter feeders. The development and flocculation of the phytoplankton bloom were monitored within the surface layer (10 m depth) by in vivo chlorophyll fluorescence and silhouette camera observations. Sedimentation rate, seston abundance and composition, and sea scallop functional responses were monitored at 20 m depth (below the bloom) to provide insight into the potential forcing of feeding and digestion processes by changes in the abundance, composition and properties of the ambient food supply. The bloom began in mid-March and median floc diameter at 10 m depth increased rapidly from 200 μm to greater than 400 μm between 21 and 28 March. Flocs were observed to be abundant in the surface layer up to 4 April. Daily vertical particle flux was high during the last week of March and declined to near zero by 1 April. Clearance rates of scallops held at 20 m depth were relatively high (average ± S.D.; 11.7 ± 4.0 L h^− 1) during the period of bloom settlement and declined rapidly to low levels (0.4 ± 0.9 L h^− 1) after 31 March. Average absorption efficiency also declined (0.88 ± 0.01 to 0.78 ± 0.05) after bloom settlement. Daily biodeposition rates by scallops were poorly correlated with temporal variations in the quantity (total particulate matter and chlorophyll a concentration) or quality (organic content) of seston available to the scallops, but were significantly correlated with sedimentation rate. Comparison of disaggregated inorganic particle size distributions for suspended particulate matter, settled particles, and scallop feces indicated that fine-grained particles (1 to 4 μm) were effectively ingested by sea scallops—an indication of whole floc ingestion. The settlement of flocs produced during the spring bloom appears to be important in regulating this species physiological energetics and for enhancing the bioavailablility of fine particles (including picoplankton) and particle-reactive contaminants.     

Effect of meal size on the specific dynamic action of the juvenile snakehead (Channa argus)

The effect of meal size on the specific dynamic action (SDA) of the juvenile snakehead (Channa argus) was assessed at 25 °C. The fish were fed with test diets at meal sizes of 0.5, 1, 2, 3, 4, and 5% body mass and the postprandial oxygen consumption rate was determined at 1-h intervals until it returned to the pre-prandial level. The peak metabolic rate increased from 237.4 to 283.2 mg O₂ kg^− 1 h^− 1 as the relative meal size increased from 0.5% to 3% and leveled off at 4% and 5%. Factorial metabolic scope increased from 1.53 to 1.99 and SDA duration increased from 11.7 to 32.3 h as the relative meal size increased from 0.5% to 5%. The relationship between SDA duration (D) and relative meal size (M) was described as: D = 4.28 M + 10.62 (r² = 0.752, P < 0.05, n = 50). The energy expended on SDA increased while the SDA coefficient decreased with increasing meal size. The results of the present study suggest that the snakehead may adopt different feeding strategies when taking in different amounts of food.