Absence Of Algae Research Articles

Response of the methanogenic microbial community of a profundal lake sediment (Lake Kinneret, Israel) to algal deposition

An algal bloom of Peridinium gatunenese generally precedes the annual maximum of methane release from the profundal sediment of Lake Kinneret. Therefore, we investigated the response of the sediment methanogenic microbial community to simulated algal deposition. Addition of algal biomass on top of sediment cores resulted in increased CH4 production rates and concentrations of the fermentation products acetate and propionate in the upper 4‐cm layers with maximum values at 1‐cm depth. Addition of algae to sediment slurries also resulted in increased CH4 production rates and a transient increase of H2, propionate, and acetate concentrations within the first 10 d after addition. The composition of the active microbial community was determined by analysis of terminal restriction fragment polymorphism (T‐RFLP) targeting ribosomal RNA and cloning and sequencing of reverse‐transcribed 16S rRNA. Analysis of the sediment in the presence and absence of algae indicated that among the Bacteria, members of Deltaproteobacteria and Clostridiales responded by synthesis of ribosomes after 1 d of incubation and those of Bacteroidetes after 6 d. Among the Archaea, ribosomal RNA of the Methanosaetaceae (i.e., acetate‐utilizing methanogens) slightly increased after 6 d. Algal deposition apparently stimulated ribosomal synthesis in these sediment microorganisms, thus resulting in increased activity. We conclude that these microorganisms were involved in degradation of the algal biomass resulting in transient release of acetate and other fermentation products and increased production of CH4.

Importance of Algal Biomass to Growth and Development of <I>Anopheles gambiae</I> Larvae

We conducted experiments to investigate the importance of algal food resources for larval growth and adult emergence of Anopheles gambiae Giles s.s. in simulated larval habitats in Kenya, and in greenhouse and laboratory microcosms in the United States. In the first experiment, we used shading to reduce algal biomass, and because algal production and larval development might be a function of underlying soil nutrients, we crossed sun-shade treatments with soils of two distinct types collected near larval habitats. Shading reduced pupation rates and total adult biomass of An. gambiae by approximately 50%. Soil type had no significant effect on mosquito production, but it did significantly affect concentrations of phosphorus and chlorophyll a in the surface microlayer. In a subsequent experiment conducted in the greenhouse to reduce temperature differences found between the shaded and sunlit treatments, <1% of larvae in the shaded treatments reached the pupal stage. There was a marked reduction of chlorophyll a levels as a function of shading and larval density. In a third experiment, larvae receiving material harvested from sunlit surface microlayers performed as well as those receiving liver powder, whereas those receiving surface microlayer from shaded habitats suffered >90% mortality and failed to pupate. In a fourth experiment, glucose was added to shaded microcosms to stimulate bacterial activity in the absence of algae. Bacterial growth rates were 2 to 3 times higher, and larval development was enhanced in glucose-amended treatments. However, pupation rates and adult weights in glucose-amended shaded microcosms were still poor compared with those in nonamended sunlit microcosms. Overall, these results demonstrate the importance of algal biomass in the surface microlayers of larval habitats to development and adult production of An. gambiae.

Modulation of the bacterial response to spectral solar radiation by algae and limiting nutrients

SUMMARY 1. The response of bacterial production (measured as [3H]TdR incorporation rate) to spectral solar radiation was quantified experimentally in an oligotrophic high‐mountain lake over 2 years. Bacterial responses were consistent: ultraviolet‐B (UVB) was harmful, whereas ultraviolet‐A (UVA) + photosynthetically active radiation (PAR) and PAR enhanced bacterial activity. Full sunlight exerted a net stimulatory effect on bacterial activity in mid‐summer but a net inhibitory effect towards the end of the ice‐free period.2. Experiments were undertaken to examine whether the bacterial response pattern depended on the presence of algae and/or was modulated by the availability of a limiting inorganic nutrient (phosphorus, P). In the absence of algae, [3H]TdR incorporation rates were significantly lower than when algae were present under all light treatments, and the consistent bacterial response was lost. This suggests that the bacterial response to spectral solar radiation depends on fresh‐C released from algae, which determines the net stimulatory outcome of damage and repair in mid‐summer.3. In the absence of algae, UVB radiation inhibited bacteria when they were strongly P‐deficient (mean values of N : P ratio: 46.1), whereas it exerted no direct effect on bacterial activity when they were not P‐limited.4. P‐enrichment of lake water markedly altered the response of bacteria to spectral solar radiation at the end of ice‐free period, when bacteria were strongly P‐deficient. Phosphorus enrichment suppressed the inhibitory effect of full sunlight that was observed in October, both in whole lake water (i.e. including algae) and in the absence of algae. This indicates that the bacterial P‐deficiency, measured as the cellular N : P ratio, was partly responsible for the net inhibitory effect of full sunlight, implying a high bacterial vulnerability to UVB.

Replacement of live food with a microbound diet in feeding Litopenaeus setiferus (Burkenroad) larvae

Microbound feeds have been well accepted by shrimps and farmers in many penaeid shrimp hatcheries. The present study focused on an adequate level of replacement of Artemia nauplii and microalgae by a microbound diet for rearing Litopenaeus setiferus (Burkenroad) larvae. A microbound diet (MBD) consisting of fishmeal, squid meal, shrimp meal, yeast meal and soybean meal was used. The first experiment was designed to obtain the optimum level of MBD to complete the live feeding schedule, from Protozoea (PZIII) to Mysis (MIII). The experimental levels of the microbound diet tested were 2, 4, 6 and 8 mg MBD L−1 day−1. The next step was to determine the Artemia nauplii replacement level from PZI to MIII by MBD. These experiments were carried out either in the presence (Experiment 2) or in the absence of algae (Experiment 3). Four replacement levels were tested: 0% (4 mg MBD L−1 day−1: 1 Artemia nauplii mL−1), 40% (5.5 mg MBD L−1 day−1: 0.6 Artemia nauplii), 60% (6.5 mg MBD L−1 day−1: 0.4 Artemia nauplii) and 100% (8 mg MBD L−1 day−1: 0 Artemia nauplii). In all experiments growth, survival, development, quality index (QI) and performance index (PI), were used to determine the optimum concentration of microbound diet. Results showed that 6 mg MBD L−1 day−1 can be recommended as a complement to live food for L. setiferus larvae from PZIII to MIII. In the presence of algae, maximum growth and survival may be obtained in 40–60% (5.5–6.5 mg MBD L−1 day−1) of Artemia nauplii replacement levels. In the absence of algae, the Artemia nauplii replacement resulted in slower development, less salinity resistance, lower growth and lower survival than was obtained in larvae fed with algae.

Co-feeding microparticulate diets with algae: toward eliminating the need of zooplankton at first feeding in larval red drum ( Sciaenops ocellatus)

The effect of adding algae to the culture water used to rear red drum larvae was evaluated in terms of growth, survival and digestive enzyme activity. Red drum larvae were subjected to one of the following dietary regimes from first feeding (day 3 post-hatch) to day 14: (1) zooplankton supplemented with algae (L-A), (2) zooplankton without algae (L-NA), (3) a microparticulate diet with algae (M-A) and (4) the microparticulate diet alone (M-NA). The presence of algae in the rearing tanks improved growth of red drum larvae for both types of feeds. Growth was significantly higher ( P<0.05) in larvae reared in the presence of algae (L-A and M-A) than in larvae raised in the corresponding treatments without algae (L-NA and M-NA). Red drum larvae raised on the microparticulate diet and algae (M-A) grew as well as the zooplankton treatment with no algae (L-NA), and were not significantly different from the L-A treatment. The larvae fed the microparticulate diet in the absence of algae (M-NA) were significantly smaller than the other three treatments. These results were consistent for two separate feeding trials. Final survival was highly variable in all treatments; nevertheless, mean final survival values were 30% higher in treatment L-A compared to L-NA (14.1 and 10.1%, respectively) and 42% higher in M-A than for M-NA (6.2 and 4.0%, respectively). Significantly higher trypsin and aminopeptidase activity was observed in the presence of algae, which may have influenced the digestion of the diet. Our results demonstrate that red drum larvae may be raised on a microparticulate diet from first feeding without the use of zooplankton.

Phragmites australis: effects of shoot submergence on seedling growth and survival and radial oxygen loss from roots

Laboratory experiments indicated that any degree of permanent submergence +40–+120 mm) of young seedling shoots of Phragmites (height: 20–30 mm) greatly reduced (75–100%) the chances of their becoming emergent. With +40 mm submergence and with an absence of algae, about 25% of shoots emerged and grew normally; where algal growth developed during the experiment, 15% of shoots emerged, but where the submerging water was particularly rich in P and algae were present from the onset, no shoots emerged. Seedling leaves which became covered in epiphytic algae lost their chlorophyll. The roots of submerged plants tended to develop more extensive aerenchyma than those of controls whose shoots were emergent. When, after 25 days, water tables were lowered to the soil surface in sand treatments, seedlings recovered quickly except for those from a treatment with dense algal growth. In more mature seedlings (shoot height = 300–400 mm) gradual submergence of shoots in either light or darkness reduced radial oxygen loss (ROL) from adventitious root apices. At 23°C there was no ROL at complete submergence in darkness; at 18°C the values were from 7–23% of the dark, fully emergent condition. When the lights were switched on, ROL increased almost immediately due to photosynthetic oxygen generation and entrapment in the submerged shoots. At 18°C the values attained, relative to the dark emergent condition, were from 42–59%, but at 23°C they were much lower: 13–26%. These effects are discussed in relation to the regeneration of Phragmites by the establishment of seedlings, possibly after die-back.

Investigations into the causes of early larval mortality in cultured summer flounder ( Paralichthys dentatus L.)

Experiments were conducted to investigate larval mortality in cultured summer flounder during the first 2 weeks after hatch. The influence of feeding success, parentage, addition of algae, water quality, and the microbial community on mortality during this period were investigated. Larvae were raised in 2-l bowls at initial densities of 50 or 75/l with mild aeration, 12 L:12 D photoperiod, and regular 50% water changes. In all experiments, mortalities were recorded and removed daily. In the first two experiments, daily samples of larvae were taken to assess feeding success and to relate that to survival. The second experiment investigated the effects of both feeding success and the addition of algae to larval culture bowls on larval survival. The third experiment investigated the effects of water quality and bacterial load on survival during the experimental period. The first two experiments indicated that failure to establish feeding is probably not the cause of catastrophic mortality of the larvae, although a statistical relationship existed between feeding incidence and survival in two of six cases. High variability (34±38%, n=82) in survival was seen in the first two experiments (both within and between parental crosses) suggesting that catastrophic mortalities were due to rearing conditions in addition to gamete quality. The addition of algae to larval cultures increased survival from 13±24% ( n=33) in the absence of algae during the first experiment to 46±39% ( n=49) with the addition of algae during the second experiment. The final experiment indicated that larval mortality was not linked to the measured microbial or water quality conditions. The relationship between the percentage of floating eggs at time of fertilization and survival at 10 days after hatch was not significant.

Modelling of genetically engineered microorganisms introduction in closed artificial microcosms.

The possibility of introducing genetically engineered microorganisms (GEM) into simple biotic cycles of laboratory water microcosms was investigated. The survival of the recombinant strain Escherichia coli Z905 (Apr, Lux+) in microcosms depends on the type of model ecosystems. During the absence of algae blooming in the model ecosystem, the part of plasmid-containing cells E. coli decreased fast, and the structure of the plasmid was also modified. In conditions of algae blooming (Ankistrodesmus sp.) an almost total maintenance of plasmid-containing cells was observed in E. coli population. A mathematics model of GEM's behavior in water ecosystems with different level of complexity has been formulated. Mechanisms causing the difference in luminescent exhibition of different species are discussed, and attempts are made to forecast the GEM's behavior in water ecosystems.

Short‐term toxicity test based on algal uptake by Ceriodaphnia dubia

A Ceriodaphnia algal uptake suppression test (CAUST) was developed for short‐term toxicity screening. The test is based on the feeding behavior of C. dubia and requires as little as 1 hour contact time between C. dubia neonates and toxicant. Before the test, neonate digestive tracts were cleared by feeding yeast to the daphnids. Neonates were then exposed to toxicant, followed by addition of Scenedesmus subspicatus to the bioassay vessels. Daphnids were examined under bright‐field microscopy for presence of algae (indicated by a green‐colored digestive tract) or absence of algae. Uptake indicated no toxic effect, whereas absence of uptake indicated toxic inhibition. Median effective concentrations (EC50 values) were computed based on results over a range of dosed toxicant concentrations. Results for cadmium, zinc, copper, pentachlorophenol, phenol, cyanide, and selected pesticides showed that CAUST was similar in sensitivity to the standard 48‐hour C. dubia acute bioassay and was as sensitive as or more sensitive than the 1‐hour I.Q. test and 30‐minute Microtox.

Effects of copepod foraging behavior on predation risk: An experimental study of the predatory copepod Pareuchaeta norvegica feeding on Acartia clausi and A. tonsa (Copepoda)

The effect of foraging behavior on predation risk was studied by exposing the two small calanoid copepods Acartia clausi and Acartia tonsa to 0 or 1 ppm (~1,500 cells ml−1) of the diatom Thalassiosira weissflogii and to presence of the predator Pareuchaeta norvegica. In filtered water, predation rate was the same on the two species. In algal suspension, predation rate on A. clausi was half that in filtered water and half that on A. tonsa. Video observations revealed distinct differences in motility of Acartia depending on algal concentration. Both species performed frequent short feeding bouts in algal suspension; nonfeeding copepods in filtered water alternately sank or adjusted their vertical distribution by stronger jumps. Jump frequency nearly doubled for A. clausi in filtered water, but no significant difference was observed for A. tonsa. To explain the predation, assuming that P. norvegica is a rheotactic predator, we developed a model of potential hydrodynamic disturbance associated with each foraging behavior. Increased encounter rate with P. norvegica caused by frequent strong jumps by A. clausi in the absence of algae could explain &gt;40% of the observed increase in predation rate. For A. tonsa, jump frequencies and predation rates were similar in both food treatments, which is in accordance with the model.

Inhibition of urease activity in flooded soils: Effect of thiophosphorictriamides and phosphorictriamides

The effectiveness of two thiophosphorictriamides, [N-(n-butyl)thiophosphorictriamide (NBPT) and thiophosphoryltriamide (TPT)], and three phosphorictriamides, [N-(n-butyl)phosphorictriamide (NBPTO), phosphoryltriamide (PT) and cyclohexylphosphorictriamide (CHPT)], to inhibit urease activity in flooded soils in the presence or absence of photosynthetic algae was evaluated in laboratory experiments. Both TPT and its oxygen analogue PT were poor inhibitors of urease activity in these flooded soils in the presence or absence of algae. In the absence of photosynthetic algae, the rate of urea hydrolysis was retarded slightly by the addition of NBPT. However, in the presence of algae the capacity of NBPT to inhibit urease activity was enhanced considerably. It appears that the oxygen produced by the photosynthetic algae resulted in more rapid conversion of the pro inhibitor NBPT to NBPTO, which is the effective urease inhibitor. The phosphorictriamides CHPT and NBPTO were significantly better than the other compounds for retarding urease activity, and CHPT ranked above NBPTO as a urease inhibitor. In the presence of photosynthetic algae the effectiveness of these inhibitors appears to be reduced, and this seems to be related to algal uptake of nitrogen and more rapid volatilization of ammonia and nitrification. The results suggest that the phosphorictriamides CHPT and NBPTO in conjunction with an algicide, to control the growth of floodwater algae, have the potential to considerably reduce ammonia loss from flooded rice soils.

Light penetration in waste stabilization ponds

The penetration of light into waste stabilization ponds was studied because of its importance in pathogen removal and algal productivity. The attenuation of light in ponds was dominated by light absorption by gilvin (also called dissolved yellow matter or humic substances) and algae, light scattering processes (turbidity) being of no importance. Gilvin exerts a strong influence over the spectral variation and longer wavelengths penetrate much better than short wavelengths. Estimates of attenuation coefficients in the u.v. suggest that these wavelengths are less penetrating than previously reported. Differences in algal concentrations cause the differences in light attenuation seen between ponds, though they also cause some spectral variation because short wavelengths are more affected by changes in algal biomass than long ones. In the absence of algae there appears to be a lower limit to the clarity of ponds dictated by gilvin and other substances. Secchi disks were found to be reliable instruments for measuring light penetration.

Modern Deep-Water Coral Mounds North of Little Bahama Bank: Criteria for Recognition of Deep-Water Coral Bioherms in the Rock Record

ABSTRACT Deep-water, ahermatypic coral mounds are present at water depths of 1,000-1,300 m on the lower slope north of Little Bahama Bank. The mounds are patchily distributed over a minimum area of 2,500 km2 and typically display 5-40 m of relief above the surrounding sea bottom. A diverse benthic community exists on these apparently unlithified mounds, including l 1 genera and 16 species of ahermatypic coral (Bathypsammia, Caryophyllia, Deltocyathus, Desmophyllum, Enallopsammia, Javania, Madrepora, Polymyces, Solenosmilia, Stephanocyathus, and a previously undescribed genus), alcyonaceans, gorgonians, antipatharians, hydroids, ophiuroids, crinoids, barnacles, galatheid crabs, polychaetes, gastropods, bivalves, and sponges. Conspicuously absent from the coral fauna are Lop elia and Dendrophyllia, common deep-water corals in other parts of the Atlantic. Radiocarbon dates on fresh coral and gorgonian fragments of 940 ± 40 and 860 ± 50 years indicate the mounds are at least in part Recent and are probably actively forming today. Bored and stained corals date at around 22 10314C years B. P., which establishes a minimum age for these mounds. We speculate that the mounds develop on sea-floor perturbations in areas where strong bottom currents provide needed oxygen and nutrients to the fauna. The mounds may have undergone multi-stage evolution from colony to thicket to coppice to bank. This evolution may be accomplished through the in situ contribution of skeletal material along with the baffling and trapping of fine-grained carbonate sediment winnowed from adjacent areas by bottom currents. If found in the rock record, the coral mounds north of Little Bahama Bank would probably be considered bioherms. Geologists should thus be aware that scleractinian bioherms are not uniquely shallow-water in origin. The distinction between ancient deep- and shallow-water coral buildups involves using multiple recognition criteria, including: 1) presence or absence of algae; 2) diversity of corals; 3) coral morphology and microstructure; 4) abundance of planktonic/benthonic components; 5) microborings; 6) surrounding litho- and biofacies; 7) stable isotopes of carbon and oxygen; and 8) trace element geochemistry, particularly Sr and U concentrations. The distinction between deep- and shallow-water bioherms is crucial to regional paleoenvironmental and stratigraphic interpretations.

Seasonal shifts of sediment within an estuary mediated by algal growth

Measurements of the level of mud flats in the Deben estuary (Suffolk, England) show seasonal change with accretion of ~ 5 cm between April and September during algal growth, and erosion of that amount during autumn and winter when algae are dead or absent. Although some seasonal change might occur in the absence of algae, the rates of deposition involved require that erosion be inhibited and sedimentation be maximised from the available suspensions. In this the binding and baffling activity of algae is apparent. The total amount of deposition on the flats (10 5 tonnes) is far more than can be supplied from the river or the sea, and transfer between the channel banks and the tidal flats on a seasonal basis is postulated.

Effect of Exposure Period and Algal Concentration on the Frequency of Infection of Aposymbiotic Ciliates by Symbiotic Algae from Paramecium bursaria

SYNOPSISThe effect of exposure period and concentration of algae on the frequency of infection of aposymbiotic ciliates by algae obtained from the same clone of Paramecium bursaria syngen 2, was studied. The frequency of infection was roughly proportional to the algal concentration and to the exposure time of ciliates to algae. The relationship of algal concentration to infection frequency closely fitted the Poisson distribution curve for N = 1, suggesting that the minimum number of algae required to infect a single ciliate is 1. However, the data also strongly suggested that the average number of algae required to initiate infection of an average ciliate was ˜ 1,000. Three possible resolutions of this situation are: (a) the selection by the ciliate of a rare infective variant from a heterogeneous population: (b) the rare escape of an alga from digestion by the ciliate; and (c) the requirement for a large number of algae‐ciliate contacts to induce susceptibility in the ciliate. Splitting the exposure of ciliates to algae into 2 periods of 0.5 h, separated by 5 h in the absence of algae, produced a much higher frequency of infection than a single l‐h exposure, supporting the suggestion that the large number of algae is required to induce susceptibility in the ciliate which can then be infected by as few as a single algal cell.

A Deeper Water Mud Mound Facies in the Alps

ABSTRACT In the Hochlerch-Silleck syncline which forms the frontal part of the Lechtal nappe, Bavarian Alps, the lowest unit is composed of red of Lower and Middle Jurassic age. This unit termed massive red limestone is a mudstone-wackestone facies which exhibits slump structures, stromatactis and an absence of algae and corals. Because of these features, in conjunction with the three dimensional shape of the deposits and evidence for organic activity it is concluded that the red is a deeper water mud mound deposit (possibly greater than 100 meters in depth).

The Effects of Bird Droppings on Chemical and Biological Dynamics in Brackish Water Rockpools

In the Baltic, some brackish water rockpools, heavily polluted by bird droppings, were investigated in order to study some of the general patterns of biochemical cycling of the nutrients. The seasonal variations of the following parameters were studied: salinity, temperature, rainfall, pH, algal biomass, detrital content, NH4-N, N02-N, N03-N, P04-P, suspended and soluble organic nitrogen and phosphorus. The diurnal variations of pH, P04-P and oxygen were measured. The faunal composition is discussed. The bird feces provided nutrients well beyond the needs of the algal biomass throughout the vegetation period. High concentrations of phosphate were always found, and this resulted in extremely low N/P ratios reflecting the chemical composition of the bird feces. Ammonia was always the dominating inorganic nitrogen compound and only during the period of maximum algal growth in the spring were considerable amounts of nitrate found. A possible inhibition of the nitrification processes resulting in an accumulation of ammonia is discussed. The high concentrations of ammonia might have a toxic effect on the algae, especially at the prevailing high pH-values. Most of the algal biomass was decomposed in the beginning of July. The diurnal variation of inorganic phosphate was found to be very large even in the absence of algae. This is mainly attributed to the activity of both autotrophic and heterotrophic bacteria. The difficulties in relating these fluctuations to productivity measurements are discussed. The nutritive value of the detrital layer, which consists mostly of fecal pellets, is discussed. Pe3IoMe

Arctic Marine Vegetation

IN NATURE, vol. xii. p. 55, an interesting article on the Arctic marine vegetation, quotes Ruprecht (with doubt as to his accuracy) in regard to an asserted absence of Algae in Behring Sea and the waters north of it.