Differential patterns of mesozooplankters’ distribution in relation to physical and biological variables of the northeastern Aegean Sea (eastern Mediterranean)

Mesozooplankton group composition was examined in the Northeastern Aegean Sea (NEA) over a grid of 30 stations sampled during July 2004. The surface water layer influenced by the low salinity Black Sea waters (BSW) is considered in this paper. We attempted to study horizontal distribution patterns of major mesozooplankters within a more comprehensive framework, taking into account not only hydrology but also available, concurrently collected data on lower trophic levels (autotrophic and microbial heterotrophic communities). BSW was mainly restricted in the eastern part of the surveyed area where it was entrapped in a ca. 50-km wide anticyclone (the “Samothraki” gyre). High Chlα concentrations, autotrophic biomass as well as abundance and biomass of mesozooplankton were associated with the BSW, with the highest values recorded inside the gyre as well as at its coastal northern periphery and the lowest values towards the western and offshore part of the surveyed area characterized by high salinity waters of Levantine origin. Among mesozooplankters, cladocerans (mainly Penilia avirostris) showed a high abundance within the gyre in contrast to the very low abundance of copepods and appendicularians. Low salinity-high temperature gyre waters were characterized by the dominance of cyanobacteria of the genus Synechococcus in autotrophic biomass and the significant contribution of heterotrophic nanoflagellates in microbial heterotrophic biomass. Based on existing knowledge on ecophysiological traits and prey size-spectra selectivity, we discuss the observed distribution patterns of major mesozooplankton groups in terms of ambient abiotic parameters and the possible biological interactions among these groups as well as with lower or upper trophic levels.     

Temperature,salinity and water-age variations in a tidal creek network,Bushehr Port,Iran

The spatio-temporal variability of temperature and salinity was studied for a creek network and its adjacent coastal waters along the northwestern coast of the Persian Gulf during warm and cold months. Salinity variations and tidal fluctuations were found to be out of phase throughout the creek. Temperature variations at the creek were exhibit a direct correlation with tidal fluctuations during cold months and were inversely related during warm months. The creek water was colder (warmer) than offshore water during the cold (warm) season. The salinity values observed inside this inverse estuary were higher during the warm season than the corresponding values during the cold season due to a change in evaporation rates; while the open water salinity had an opposite pattern. Using salinity as a tracer, the water-age (WA) was calculated, which shows almost linear increase from the mouth to the head. The maximum WA increases from ~10 days in winter to ~30 days in summer due to the corresponding increase in longitudinal salinity gradient. Based on the calculated non-dimensional Peclet number, the diffusion process is more rapid than the advection process in this water body, especially during the cold season.     

Heterotrophic activity associated with particulate size fractions in a Spartina alterniflora salt-marsh estuary,Sapelo Island,Georgia, USA,and the continental shelf waters

An investigation was undertaken to determine the distribution and activity of the heterotrophic microplankton associated with particles from a Georgia salt marshestuarine ecosystem to the western edge of the Sargasso Sea. Heterotrophic activity was determined by the uptake of ¹⁴C-glucose. More than 80% of the activity was associated with detritus greater than 3 m in creek, river and coastal (within 4 km of shore) waters. In the Gulf Stream, approximately 80% of the heterotrophic activity was in the fraction less than 3 m. In the estuary, total heterotrophic activity fluctuated with the tides; the greatest activity occurred near low ebb tide at all locations. The lowest activity was measured at slack low and high tides. In creek water most of the heterotrophic activity was associated with particles between 14 and 180 m, whereas in coastal waters (less than 4 km from shore) most of the activity was in the fraction greater than 180 m.Contribution No. 331 from the University of Georgia Marine Institute, Sapelo Island, Georgia 31327, USA.     

Zooplankton abundance and grazing at Davies Reef,Great Barrier Reef,Australia

Zooplankton abundance and grazing on autotrophic and heterotrophic particulate matter were measured along a transect across Davis Reef (18°5S; 147°39E) and in the back-reef lagoon over tidal and diel cycles during austral winter (August 1984). Zooplankton entering the reef from the surrounding shelf waters decreased in abundance over the reef flat, presumably because of predation. Within the reef lagoon, maximum daytime densities of pelagic copepods occurred during high water, suggesting an external input. At night, water-column zooplankton biomass increased by a factor of 2 to 3 due to the emergence of demersal reef zooplankton. Zooplankton grazing rates on heterotrophic particulate matter (bacteria + detritus and Protozoa) compared to phytoplankton were higher on the reef flat than on the fore-reef or lagoon. Within the lagoon, zooplankton grazing rates on heterotrophic material were maximum during high water, coincident with maximum tidal concentrations of particulate organic carbon. The combined demersal and pelagic zooplankton community were often able to crop 30% of the daily primary production by >2µm phytoplankton. However, >50% of phytoplankton biomass was in cells <2µm, presumably unavailable to these zooplankton. Our particulate production and ingestion measurements, together with zooplankton carbon demand extrapolated from respiration estimates, suggest that the zooplankton community of Davies Reef derives much of its nutrition from detritus.Joint contribution from the University of Maryland, Center for Environmental and Estuarine Studies (No. 2015), and the Microbial Ecology on a Coral Reef Workshop (MECOR No. 19)     

Species-specific grazing rates of heterotrophic dinoflagellates in oceanic waters,measured with a dual-label radioisotope technique

A dual-isotope method was developed to measure grazing rates and food preferences of individual species of heterotrophic dinoflagellates from natural populations, collected from the Slope, Gulf Stream, and Sargasso Sea and from a transect from Iceland to New England, in 1983. The isotope method measures the grazing rates of microzooplankton which cannot be separated in natural populations on the basis of size. Tritiated-thymidine and ¹⁴C-bicarbonate were used to label natural heterotrophic and autotrophic food, respectively. Nine oceanic dinoflagellate species in the genera Protoperidinium, Podolampas, and Diplopsalis fed on both heterotrophic and autotrophic food particles with clearance rates of 0.4 to 8.0 l cell^-1 h^-1, based on ³H incorporation, and 0.0 to 28.3 l cell^-1 h^-1, based on ¹⁴C incorporation. Two dinoflagellate species, Protoperidinium ovatum and Podolampas palmipes, fed only on ³H-labelled food particles. Several species of dinoflagellates fed on bacteria (<1 m) which had been prelabelled with ³H-thymidine. The clearance rates of heterotrophic dinoflagellates and ciliates were similar and within the range of tintinnid ciliate clearance rates reported in the literature. As heterotrophic dinoflagellates and ciliates can have comparable abundances in oceanic waters, we conclude that heterotrophic dinoflagellates may have an equally important impact as microheterotrophic grazers of phytoplankton and bacteria in oceanic waters.Partially supported by a grant from the National Science Foundation, OCE-81-17744     

Distribution of diatom Pseudo-nitzschia and dinoflagellates of Dinophysis spp along coast off Goa

As a part of an annual analysis on the phytoplankton distribution and composition, regular monthly sampling carried out during October 2007- September 2008 from salinity gradient zones in the intertidal waters along the coast of Goa. Among the 179 species of phytoplankton observed during this study, as many as 11 of them are recognized, potentially toxic ones. The toxic diatom species, Pseudo-nitzschia pungens was quite preponderant, in particular during the pre-monsoon month of May 2008 off Chapora, a perennially low salinity location. Among the 10 toxic dinoflagellate species detected, the known toxic species, Alexandrium minutum followed by Dinophysis acuminata were found to attain maximum cell numbers in the study area. It is apparent from our results that the toxic species do occur in all salinity zones sampled and during many months of the year in coastal waters off Goa. Though directly governed by the variations in nutrient concentrations, some of these toxic phytoplankton species attain high cell numbers. It is reasonable for us to therefore caution that the toxic species do prevail in these waters.     

The trophic role of glycolic acid in coastal seawater. II. Seasonal changes in concentration and heterotrophic use in Ipswich Bay,Massachusetts, USA

Glycolic acid is a known algal excretory product which is found in marine waters and is readily metabolized by marine bacteria. The following parameters were measured over the course of a year in Ipswich Bay: chlorophyll a, temperature, viable bacteria, heterotrophic uptake of glycolate, and glycolate concentrations. The latter two were combined to give estimates of the flux of glycolate for a station 3 km out in the bay and for an inshore station. Pronounced seasonal changes were found for all parameters. Statistically significant correlations between heterotrophic V _max and glycolic acid concentrations and temperature were found, but not between planktonic chlorophyll a and any of the other parameters. Measurements of glycolic acid flux yielded an annual flux of 2.84 g m^-2 for the bay station, which is about 0.5% of the bay phytoplankton production. Glycolic acid turns over roughly 12 times per year in the bay. It contributes perhaps as much to bacterial metabolism as any other single substrate, but is apparently not of dominating importance.     

Observations of heterotrophic activity on photoassimilated organic matter

The natural heterotrophic utilization of released and particulate photoassimilated compounds by natural phytoplankton populations was followed during the summer of 1975 in the Kiel Bight (Western Baltic Sea). Phytoplankton exudates (2 to 21% of primary production) seem to represent an important substrate for heterotrophic bacteria: uptake rates between 8 and 17,5%/h were observed. Samples incubated with antibiotics indicated that the heterotrophic uptake of phytoplankton exudates during photosynthesis could lead to underestimation of the release rate. Production of 14_{CO 2}was used as an estimate of the mineralization of particulate photoassimilated matter. The mineralization rates measured were in the range of 6 to 20% after 20 h. In order to confirm the quantitative measurements, micro-autoradiographic examinations of the samples were performed.     

Pesticide Residues in Water From River Kaveri,South India

The residue levels of presistent chlorinated pesticides such as HCH (hexachlorocyclo-hexane) isomers and DDT (dichlorodiphenyl trichloroethane) compounds were quantified in water samples collected from the River Kaveri and its distributor River Coleroon in Tamil Nadu, South India. HCH showed higher levels in River Kaveri during premonsoon (July to September) and monsoon (October to December) months, reflecting the HCH usage during that season for paddy crops. But in the case of DDT no clear trend in residue level was observed. the α-HCH was detected as the dominant isomer in all the three sampling sites. Among DDT compounds, p,p'-DDT and p,p'-DDE showed higher percentage of the total. International comparison of residue levels revealed that the present values are comparable to the waters from Asian and South East Asian nations, but lower than some samples from other parts of India. the value of DDT is well below the EEC's maximum acceptable concentration for surface waters and lower than the recommended limit of 2000ng 1^-1 in USA water for protection of aquatic life (Water Quality Criteria, 1972).     

Utilisation des mesures de charge énergétique,d'ETS et de 14C-assimilation pour le suivi de l'activité microplanctonique dans des eaux côtières sous l'influence de rejets urbains

The influence of the sewage from the city of Marseilles, France, upon the marine microplanktonic assemblages was followed over a period of one year (May 1980–April 1981) at five stations and three sampling depths. Measurements of the ¹⁴C assimilation rate, adenylate energy charge, and the electron-transport system (ETS) were compared with parallel phytoplankton and bacteria counts. In the coastal waters near the sewage outlet the phytoplanktonic organisms were stressed, as attested by the low values of both assimilation rate and energy-charge ratios; the living microbiomass in these waters was essentially of bacterial origin. In waters situated 4 to 5 km away from the outlet, and therefore not directly under its influence, higher mean P:B and EC ratios indicated the presence of a predominantly living phytoplanktonic assemblage. Nevertheless, the metabolic stress induced by the inflow of polluted water to the waters near the sewage outlet did not prevent the occurrence of a spring bloom. The electron-transport system measurements and their relationship to the effective bacterial counts are in good accordance with the literature data describing laboratory cultures, and indicate intense heterotrophic activity in the waters nearest to the sewage outlet. This activity is most probably of bacterial origin: perhaps some of the terrestrial germs introduced into the marine environment remained viable, perhaps the considerable volume of organic matter introduced into this area induced heterotrophic development, or perhaps both factors combined. Simultaneous consideration of biochemical and physiological data with the structure and composition of the microplanktonic populations could explain the apparent contradiction between the high level of nutrient supply and the lack of photoautotrophic growth noted in previous studies in this area. However, the considerable amounts of fresh organic matter present in the waters near the sewage outlet at Cortiou indicate the necessity for great care in the use of biochemical parameters such as chlorophyll or AMP for the estimation of microplankton biomass; such estimates can be biased by the presence of non-degraded detrital particles of biological origin.     

Production dynamics of the eelgrass, <Emphasis Type="Italic">Zostera marina</Emphasis> in two bay systems on the south coast of the Korean peninsula

Production dynamics of eelgrass, Zostera marina was examined in two bay systems (Koje Bay and Kosung Bay) on the south coast of the Korean peninsula, where few seagrass studies have been conducted. Dramatically reduced eelgrass biomass and growth have been observed during summer period on the coast of Korea, and we hypothesized that the summer growth reduction is due to increased water temperature and/or reduced light and nutrient availabilities. Shoot density, biomass, morphological characteristics, leaf productivities, and tissue nutrient content of eelgrass were measured monthly from June 2001 to April 2003. Water column and sediment nutrient concentrations were also measured monthly, and water temperature and underwater irradiance were monitored continuously at seagrass canopy level. Eelgrass shoot density, biomass, and leaf productivities exhibited clear seasonal variations, which were strongly correlated with water temperature. Optimal water temperature for eelgrass growth in the present study sites was about 15–20°C during spring period, and eelgrass growths were inhibited at the water temperature above 20°C during summer. Daily maximum underwater photon flux density in the study sites was usually much higher than the light saturation point of Z. marina previously reported. Densities of each terminal, lateral, and reproductive shoot showed their unique seasonal peak. Seasonal trends of shoot densities suggest that new eelgrass shoots were created through formation of lateral shoots during spring and a part of the vegetative shoots was transformed into flowering shoots from March. Senescent reproductive shoots were detached around June, and contributed to reductions of shoot density and biomass during summer period. Ambient nutrient level appeared to provide an adequate reserve of nutrient for eelgrass growth throughout the experimental period. The relationships between eelgrass growth and water temperature suggested that rapid reductions of eelgrass biomass and growth during summer period on the south coast of the Korean peninsula were caused by high temperature inhibition effects on eelgrass growth during this season.     

A novel symbiosis between a cyanobacterium, Synechococcus sp., an aplastidic protist, Solenicola setigera, and a diatom, Leptocylindrus mediterraneus, in the open ocean

The abundance, biomass and distribution of Solenicola setigera, a colonial heterotrophic protist found only with the centric chain-forming diatom Leptocylindusmediterraneus, are reported for four major ocean basins. The distribution is cosmopolitan, and abundances and biomass are usually low (<500 colonies l⁻¹); however, in the summer of 1993, we observed a major biomass component (range = 5 to 31 μg C l⁻¹) in the surface waters of the North Atlantic attributable to S. setigera. These colonies of S. setigera were exceptionally large, and unusual in possessing high abundances of Synechococcus sp., a normally solitary cyanobacterium, embedded in the matrix covering the cells. We hypothesize that this relationship was mutually beneficial for both Solenicola setigera and Synechococcus sp. Received: 5 January 1998 / Accepted: 22 May 1998     

青藏高原东缘不同林龄云杉林冬季土壤呼吸特征

采用动态密闭气室红外CO_2 分析法(IRGA),连续定位测定青藏高原东部4种不同恢复阶段的人工云杉林和原始云杉林在冬季(2007.11.01～2008.03.31)的土壤呼吸.用挖壕沟法同步区分土壤自养呼吸和异养呼吸,并同步测定土壤5 cm温度和水分结果表明,土壤5 cm温度与冬季土壤呼吸速率具有显著的正指数相关关系,土壤含水量与冬季土壤呼吸的相关性不明显.亚高山针叶林冬季土壤呼吸温度系数Q_(10) 值为3.180 3～6.546 9,不同年龄阶段针叶林的Q_(10)值大小依次为:35 a人工云杉林>47 a人工云杉林>65 a人工云杉林>22 a人工云杉林>原始云杉林.22 a、35 a、47 a、65 aA工云杉林和原始云杉林冬季土壤总呼吸碳释放通量别为200.16、196.23、166.71、228.47、261.75 g(C)m~2,随着森林恢复更新,冬季土壤呼吸通量呈现出先下降后升高的趋势,这种变化趋势的拐点出现在47 a人工林附近.温度是影响土壤自养呼吸贡献率和异养呼吸贡献率的主要因子,温度与异养呼吸贡献率成负相关.22 a、35 a、47 a、65a人工云杉林和原始云杉林冬季土壤的自养呼吸和异养呼吸碳释放通量平均值分别为133.44、134.04、115.97、166.05、199.07 g(C)m~(-2)和66.71、62.20、50.73、62.43、62.68 g(C)m~(-2).图7表3参34     

Seasonal and tidal impact on the organic compounds and nutrients distribution in tropical mangroves,Kerala, India

Seasonal changes in the concentration of nutrients and various organic compounds were studied in the waters surrounding mangroves and in the marshy areas of mangroves. Higher amounts of nutrients and organic compounds were observed during low tide. This is due to the remineralisation of plant detritus in this area. High concentration of carbohydrates, proteins, chlorophyll and phosphate were observed during monsoon, which can be attributed to the leaching of plant detritus as well as the land run-off. During pre-monsoon and post-monsoon high tannin and lignin concentration was noted. A 24-hour sampling was also done to study the tidal impact on the concentrations of various organic compounds and nutrients in this ecosystem. Even though a tidal impact was observed, a clear picture was not reported in this study.     

Effects of cultivation strategies on the cultivation of Chlorella sp. HQ in photoreactors

Heterotrophic cultivation caused high level of ROS and high lipids accumulation. HMTC is the best culture strategy for improving the microalgal biomass. Chlorella sp. HQ had great nutrient removal capacity under five culture strategies. The effects of cultivation strategies (including autotrophic cultivation (AC), heterotrophic cultivation (HC), fed-batch cultivation (FC), heterotrophic+ autotrophic two-stage cultivation (HATC), and heterotrophic+ mixotrophic two-stage cultivation (HMTC)) on the growth and lipid accumulation of Chlorella sp. HQ and its total nitrogen (TN) and total phosphorus (TP) removal in secondary effluent were investigated in column photoreactors. The results showed that the TN and TP removal rates ranged between 93.72%–95.82% and 92.73%–100%, respectively, under the five different strategies. The microalgal growth potential evaluated by the maximal growth rate (R_max) was in the order of HMTC>HC>FC>AC>HATC. The values of biomass, total lipid yield, triacylglycerols (TAGs) yield, and total lipid content of the microalga cultivated in the last 5 d increased significantly, but the TAGs productivities of the five strategies were lower than those in the first 7 d. Compared with all the other cultivation strategies, the TAGs productivity and yield after 12 d of cultivation under the heterotrophic condition reached the highest values accompanying the highest level of intracellular reactive oxygen species (ROS), in which the TAGs yield reached 40.81 mg/L at the end of the cultivation period. The peaks in TAGs yield and ROS level suggested that HC was beneficial for lipids accumulation via regulating the cellular redox status and exerting ROS stress on microalgal cells. In summary, HMTC was the best cultivation strategy for improving the microalgal biomass and HC was the best strategy for microalgal TAGs accumulation to produce biodiesel.     

Seasonal and tidal impact on the organic compounds and nutrients distribution in tropical mangroves, Kerala, India

Seasonal changes in the concentration of nutrients and various organic compounds were studied in the waters surrounding mangroves and in the marshy areas of mangroves. Higher amounts of nutrients and organic compounds were observed during low tide. This is due to the remineralisation of plant detritus in this area. High concentration of carbohydrates, proteins, chlorophyll and phosphate were observed during monsoon, which can be attributed to the leaching of plant detritus as well as the land run-off. During pre-monsoon and post-monsoon high tannin and lignin concentration was noted. A 24-hour sampling was also done to study the tidal impact on the concentrations of various organic compounds and nutrients in this ecosystem. Even though a tidal impact was observed, a clear picture was not reported in this study.     

Acid mine-drainage toxicity testing

The BOD inhibition test, the activated sludge respiration inhibition test, and the Microtox® Bioassay procedure were examined for their potential as rapid toxicity screening methods for acid mine drainage (AMD) and for setting toxicity threshold levels in receiving waters. The BOD inhibition test proved to be unsuitable due to the high chemical oxygen demand of the toxicant. The long incubation time (minimum 5 d at 20°C) allowed growth of chemo-autotrophic bacteria and resulted in excessive flocculation and precipitation of metals, making accurate and meaningful measurements of inhibition impossible. The activated sludge respiration inhibition test was successful in measuring AMD toxicity, and for deriving toxicity threshold levels for the basic heterotrophic community in surface waters. However, it is a very time-consuming technique and is not sensitive enough to be used as a routine screening technique. The variability in toxicity was found to be due to the availability of metals as well as the effect of pH on metabolism. Simple linear models were derived to estimate inhibition within surface waters. Prediction of the inhibition caused by AMD can be made as long as the pH of the river water after mixing and the dilution of the AMD are known. Most accurate predictions are made using equations for specific pH ranges, but a useful estimation of inhibition can be obtained using the general equation: inhibition (%) = -2.34 pH + 6.41 AMD (%) + 22.1. The Microtox® Bioassay method, although expensive, was rapid and simple to use. It was the most sensitive test of the three, with the toxic response of marine bacteria increasing notably from 5 to 15 min due to the presence of bivalent metals in the toxicant. The problem of repeatability and reproducibility encountered with the activated sludge inhibition test was overcome with the highly standardised Microtox® method, making it an ideal screening method for AMD. However, the advantage of the activated sludge inhibition test is that the types of heterotrophic micro-organisms found in activated sludge are similar to those found in receiving waters such as the Avoca River and so more meaningful toxicity threshold values can be obtained.     

Distribution of Juvenile,subadult and adult Scylla serrata (Crustacea: Portunidae) on tidal flats in Australia

In Deception Bay, northern Australia, during 1979–1981, a study was made of the distribution of Scylla serrata (Forskal) in an area having a broad intertidal zone. Juveniles (20 to 99 mm carapace width) were resident in the mangrove zone, remaining there during low tide. The majority of subadult crabs (100 to 149 mm) migrated into the intertidal zone to feed at high tide and retreated to subtidal waters at low tide. Adults (150 mm and larger) were caught mainly subtidally and only small numbers were captured in the intertidal at high tide. Few crabs were captured in the coolest months (May to August). Adults were captured on the flats mainly in the warmest months (January to April), but subadults could be captured over the entire summer (September to March). Juveniles were found in the upper intertidal throughout the year.     

Distribution of chlorophyll,carotenoids and phytoplankton in relation to certain environmental factors along the central west coast of India

Distribution of chlorophyll pigments, carotenoids and abundance of phytoplankton in relation to certain environmental factors of the nearshore waters off the central west coast of India (latitudes 15°30 to 18°30N) were studied monthly at 7 stations during 1970/1971. Changes in the hydrographical factors and the biological processes occurring in the region during different months appear to be influenced by the pattern of upwelling along the northern and southern parts of the west coast of India. The pigment concentration shows a marked decrease in October, but is followed by a slow but steady rise, which reaches its maximum in April/May. A slightly smaller maximum is noticed in December/January. The composition of various chlorophyll pigments and carotenoids indicated the physiological state of phytoplankton populations during different months in the region investigated. Abundance of specific phytoplanktonic elements, consisting mainly of diatoms, in space and time, characterises the waters of the central west coast of India, indicating a clear succession of species.     

Green and blue fluorescing dinoflagellates in Bahamian waters

At three stations in Bahamas waters, in 1989, 15 to 30% of all the dinoflagellates >20µm diameter observed in near-surface waters fluoresced green under blue excitation light, 55 to 66% fluoresced red, and the remainder did not fluoresce at all. The abundance of these green-fluorescing dinoflagellates ranged from ca 5 to 10 cells l^–1 at the study sites. Under UV excitation, however, the dinoflagellates had a blue to blue-green appearance. Almost all the blue-green fluorescing dinoflagellates appeared to be heterotrophic, except for one species,Phalacroma rapa Stein, which also contained red-fluorescing (under blue light) chlorophylla. The emission spectra from all species examined were of three basic types. Type 1 typically had two fluorescence emission peaks (ca 440 and ca 510 nm). Type 2 spectra possessed one sharp peak at 495 nm. Spectra belonging to Type 3 had a broad peak around 470 to 480 nm. The green fluorescence thus is likely caused by different substances in individual species. The attempt to reconstitute observed spectra with nicotinamide adenine dinucleotide (NADH) and riboflavin 5-phosphate (FMN) solutions was unsuccessful.