Low Levels In Summer Research Articles

A model study on dynamical processes of phytoplankton in Laizhou Bay

A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the observed temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corresponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limitation, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River excluded.

SEASONAL CHANGES IN SOME PHYSIOLOGICAL AND CHEMICAL CONTENT IN LEAFLETS OF DATE PALM Phoenix dactilyfera L . IN THE WESTERN DESERT, IRAQ

Study was conducted in the western desert (south east of Al-Ramadi city) to shed light on drought tolerance, twelve of a number of already establishment field of Phoenix dactilyfera L. ( Zahde) trees which are used in this study. Through out the best 8 years half of the trees was being irrigated regularly while the other half irrigation was stopped two years period to the start of the experiment and contained to the end of it. Measurements on the leaf water potential and water loss were taken during the day hours (from dawn to sunset) for several days. Seasonal diurnal changes in total carbohydrates and other phenotypic characteristics, N and K percentage were recorded. Dunces Multiple Range was used to separate the means at 0.5% probabilities. Changes in water potential values, water loss, total carbohydrates, N and K percentage depended largely on irrigation vs. nonirrigation and seasons, beside the nutrient elements were in low level in summer specially in leaflets of nonirrigation date palms

Sperm production and quality in brill Scophthalmus rhombus L.: relation to circulating sex steroid levels

The aims of the present study were to characterize sperm quality and to quantify seasonal changes in sexual hormone (testosterone [T], 11-ketotestosterone [11-KT] and 17,20β-dihydroxypregn-4-en-3-one [17,20β-P]) levels in male brill (Scophthalmus rhombus) plasma, as well as to test a more intensive sampling strategy to establish relationships between sex steroid levels and sperm production parameters. Sperm concentration ranged from 0.5 to 3.1 × 10(9) spermatozoa mL(-1), and changes in sperm quality parameters depending on sampling date were observed. Plasma sexual steroid levels remained high and changed in parallel during the spawning season and afterwards decreased to very low levels in summer. The analysis of annual changes of 11-KT and T ratios suggests that 11-KT can be the main circulating androgen for stimulating spermatogenesis in S. rhombus and that T could be involved in the beginning of spermatogenesis through the positive feedback on brain-pituitary-gonad axis. Finally, daily 11-KT and T levels showed similar patterns of variation in males sampled, whereas 17,20β-P amounts showed somewhat opposite trends. These differences could be related with the different role of androgens and progestin during the spermatogenesis.

Climatic cues and glucocorticoids in a free-ranging riparian population of red deer (Cervus elaphus)

We measured faecal cortisol metabolites of a free-ranging riparian population of red deer to investigate potential effects of season, ambient temperature, precipitations and water level on the annual secretion pattern. Individuals may cope with environmental challenges through the secretion of stress hormones (glucocorticoids) which allows the integration of environmental change and life history traits by means of an adaptive feedback mechanism. Adaptations regard cyclic day-to-day activities, short-term environmental stressors or long-term ecological pressures. We detected a clear seasonal pattern of glucocorticoid metabolites secretion, with higher levels in winter and lower levels in summer. The model relating glucocorticoids secretion to minimum ambient temperature was the best fit to our dataset, although the observed pattern might as well be due to declining nutritional intake and reduction of metabolic rate in the cold season. We observed an improvement of the fit when stochastic events (flash flood) were included in the model, and discussed their role as potential contingent environmental stressors.

Stress and parasitism of white-footed mice (Peromyscus leucopus) in dry and floodplain environments

We hypothesized that flooding represents an environmental stressor that might affect the corticosterone levels, parasite prevalence, and life history of small mammals living in floodplain environments. We compared populations of white-footed mice ( Peromyscus leucopus (Rafinesque, 1818)) on floodplains and dry areas. We found more males on floodplains (p = 0.008) and more females on dry areas (p = 0.005). There were no differences in mass (p > 0.05) or intestinal parasite prevalence (p = 0.665) between dry and floodplain habitats, but bot fly larvae were significantly more prevalent in males living on floodplains (p = 0.043). Floodplain animals had significantly higher levels of corticosterone than dry-area animals in fall, and lower levels in summer (F[1,20] = 4.483, p = 0.047). In addition, we found that animals with intestinal parasites had higher levels of corticosterone than those that were without parasites (p = 0.014) or that harbored bot fly larvae (p = 0.001). Floodplains seem to be harsher environments than dry areas, but this may be a result of differences in habitat rather than a direct result of flooding.

Distribution of heavy metals and nutrients in rainwater in coastal regions between the southern Yellow Sea and East China Sea

Rainwater samples were collected in series in Qianliyan Island (southern Yellow Sea) and Shengsi Archipelago (East China Sea) between May 2000 and May 2002, chemical analysis for pH values, concentrations of heavy metals (Cu, Pb, Zn and Cd) and nutrients (NH4+, NO3−, PO43−, SiO32−) were performed. Results indicate that concentrations of most of the heavy metals and nutrients in rainwater show clear seasonal variation, i.e. high level in winter and low level in summer. Regionally, concentrations are higher in the southern Yellow Sea than in the East China Sea, but the annual input of heavy metals into oceans by wet deposition is similar in both stations. However, the input of nutrients by wet deposition in the East China Sea is 2–3 times higher than that in the southern Yellow Sea. In individual, Pb and PO43− are input to the sea mainly by dry deposition; whereas Cu, Zn, Cd and N compounds are input dominantly by wet deposition, the N/P ratios in the rainwater from two stations are much higher than those in seawater, showing a significant impact of atmospheric wet deposition on marine production and biogeochemical circulation of nutrients in these sea regions.

In situ enclosure experiments on the influence of cultured mussels ( Perna canaliculus) on phytoplankton at times of high and low ambient nitrogen

The influence of the cultured mussel Perna canaliculus (Gmelin 1791) on the abundance of phytoplankton was investigated in Pelorus Sound, New Zealand. Four in situ enclosure experiments were undertaken, two in summer when ambient nitrogen was low, and two in winter when it was high. Each experiment had four manipulation types: added mussels; added nitrogen; both mussels and nitrogen added; and control (no additions). In summer, there was a significant increase of chlorophyll a in response to added nitrogen, indicating that the phytoplankton were nitrogen-limited. At this time, mussels caused an increase (11–17%) in phytoplankton biomass, possibly by converting particulate nitrogen to ammonium, making the nitrogen available for phytoplankton utilisation. The highest ambient chlorophyll a concentrations coincided with high ambient nitrogen in the winter. At this time, mussel grazing caused a significant decrease (5–14%) in phytoplankton concentration, indicating that within-farm depletion of phytoplankton is most likely to occur in winter. On an annual time scale, the mussels had a stabilising influence on phytoplankton biomass, reducing high ambient levels in winter and slightly increasing low levels in summer.

Seasonal and spatial variation of reduced sulphur compounds in mistletoes (Viscum album) and the xylem sap of its hosts (Populus × euramericana and Abies alba)

In the present field study with adult trees inhabited by Viscum album, the question was addressed as to whether European mistletoes are able to remove reduced sulphur from the xylem sap of its hosts. For this purpose the reduced sulphur composition and content of the xylem sap of Viscum album and the corresponding hosts Populus × euramericana and Abies alba were analysed. The xylem sap of Viscum was enriched in reduced sulphur compared to the hosts but still reflected the higher reduced sulphur content of Populus compared to Abies. Despite similar xylem sap composition of the hosts with glutathione as the dominating thiol, Viscum on Populus contained predominantly cysteine, Viscum on Abies predominantly glutathione in its xylem sap. These findings suggest selective and different removal of reduced sulphur from these hosts. Still the amount of reduced sulphur removed was too small to result in changes of the concentration of thiols in the xylem sap of the hosts that are statistically significant, probably due to the high variability encountered under field conditions. Despite the differences in the reduced sulphur composition and contents of the xylem sap between Viscum on Populus and Viscum on Abies, total thiol content as well as thiol composition of Viscum leaves on the two hosts were similar throughout the seasons. The seasonal pattern in the thiol composition and contents of Viscum leaves showed high levels in spring and autumn and low levels in summer. The significance of these seasonal changes is discussed.

Trace metal (Cd, Cu, Ni and Pb) cycling in the upper water column near the shelf edge of the European continental margin (Celtic Sea)

Abstract This study investigates the relative importance of processes that affect trace metal (TM) cycling in the upper water column at the shelf edge of the Celtic Sea on the western European continental margin. The examined processes include external inputs (by atmosphere and river), physical factors (upwelling, winter mixing and water mass advection) and biological processes (in situ uptake, regeneration and export to deep waters). The concentrations of dissolved Cd, Cu, Ni and Pb were measured with this aim in January 1994 and June 1995 at vertical stations across slope, including stations with upwelling, and in the surface waters along the Celtic Sea shelf. Additionally, deep sea (from sediment trap data) and atmospheric fluxes were estimated. The metal profiles over the slope off the Celtic Sea are quite similar to open ocean profiles already described in the northeast Atlantic, and the concentrations in surface waters are only slightly enriched compared to the nearby open ocean (1.2–1.3× for Cd and Ni). The external sources to the system appear to be of weak influence: the fluvial input is locally strong at the coast and then “diluted” along the large continental shelf; the atmospheric deposition is not significant at the annual scale in comparison to the metal content in the upper waters of the shelf edge (at least for Cd, Ni and Cu). In the upwelling zone, a significant increase in concentrations was observed in the summer surface mixed layer (×2 for nitrate and Cd and ×1.5 for Ni) in comparison to the non-upwelling zone. In winter, concentrations of bioreactive metals increased significantly in the surface waters in comparison to the low summer levels (×5 for nitrate and Cd). Our results suggest that upwelling and winter mixing act as regenerated sources that lead to the resupply of the bioreactive elements above the permanent thermocline with a low export to deeper waters. The tracing of the Mediterranean intermediate waters (MIW) from Gibraltar to the studied area shows indeed that its elemental content at the Celtic shelf edge is mainly due to the conservative mixing of the three “end-member” component waters which are thought to make up the MIW. The remineralization of organic matter within this water mass during its transport to the north would contribute only 20% of the nutrients and Cd concentrations recorded at the Celtic Sea shelf edge. According to the correlation found with nutrients in the 10–200-m layer, dissolved Pb would also be subjected to biological uptake and regeneration within the seasonal thermocline. Particulate scavenging removal of Pb would take place below the permanent thermocline throughout the water column.

The hepatic stress protein (hsp70) response to interacting abiotic parameters in fish exposed to various levels of pollution

Two indigenous fish species, brown trout (Salmo trutta f. fario) and stone loach(Barbatula barbatula) were exposed tocomplex stressors (mixtures of environmentalpollutants) in laboratory and semi-fieldexperiments (aquaria connected to stream water)and in field studies. As a biomarker of effect,the level of the 70 kD heat shock protein(hsp70) was quantified in the liver of troutand loach. Laboratory experiments withdifferent pollutant mixtures did not mimic thehsp70-inducing or inhibiting potential of fieldconditions, whereas effects of long-termexposure in the bypass systems showed asignificant correlation with effects recordedin feral fish. Laboratory as well as semi-fieldstudies revealed the stress response to followan optimum curve, resulting in a maximum hsp70level under stress but rather low hsp70 levelswhen stressors (chemicals, high temperature)become too severe. Consequently, the hsp70level in the liver of both species was highlyseason-dependent with two peaks in late springand fall, and rather low hsp70 levels insummer, particularly in fish exposed to waterand sediment of the complexly polluted stream.In winter, the low hsp70 level of lab controlswas elevated by exposure to natural streamwater only, but elevation did not occur undercontrol conditions independent of apre-exposure to polluted streamwater two months earlier. Despite the highvariability of the hsp70 level within one yearand among five subsequent years, patternanalysis indicated the prevailing importance ofwater temperature on stress protein response.Temperature alone, however, could not explainthe regularly observed low summer levels inhsp70. Non-linear regression analysis on labcontrols revealed an optimum temperature(Topt) for the highest hsp70 level forboth fish species. In both investigated streams, thechemical influence led to a decrease in thehsp70 level only when Topt was surpassedby the ambient temperature at the same time.Otherwise, the chemical impact resulted in anelevated hsp70 level relative to the control.The study demonstrated the suitability of hsp70stress protein levels to integrate the responsedynamics of several different stressors and,therefore, to effectively function as abiomarker for the integrated effect of allenvironmental stressors acting on an organism(not only of chemical pollution). Rathercomplex kinetics of hsp70 elevation anddecrease should be taken into consideration.

Enzyme dynamics on decomposing leaf litter of Cistus incanus and Myrtus communis in a Mediterranean ecosystem

The decomposition of Cistus incanus leaf litter, a summer deciduous species, was compared to that of Myrtus communis, an evergreen species, during 15 months of incubation in a Mediterranean low shrubland. The litterbags were placed under randomly selected shrubs of Myrtus and Cistus, respectively. Owing to the different microclimatic conditions under deciduous and evergreen shrubs Cistus litter was also incubated under Myrtus shrubs. Microbial activity was evaluated by measuring litter respiration and enzyme activities (cellulase, xylanase, α-amylase, β-amylase, laccase and peroxidase). During the first 8 months of incubation the decomposition rate of both litters was independent of litter quality and incubation conditions. The average decay constant ( k) ranged between 0.29±0.03 and 0.33±0.03 yr −1. Subsequently, it increased only for litters incubated under Myrtus shrubs ( k=0.57±0.15 and 0.48±0.16 yr −1 for Cistus and Myrtus litters, respectively). The dry summer affected the decay rate of litters incubated under Myrtus but not under Cistus. Microbial respiration showed seasonal changes (from 25 to 150 μmol CO 2 g −1 dry wt. 24 h −1), with low levels in summer, mainly because of the low litter water content. After samples were placed in the field, α-amylase activity decreased rapidly, dropping to zero in Cistus litter, whereas it remained detectable in Myrtus litter (>0.02 μmol glucose g −1 dry wt. h −1). The β-amylase activity was low over the entire period. The activities of cellulase and xylanase ranged from 1 to 30 μmol glucose equivalents (reducing sugar) g −1 dry wt. h −1. Both litters showed the lowest enzyme activities in summer, when litter respiration was also at the lowest level. Peroxidase activity was detected in the litter of Myrtus(from 0 to 50 μmol o-tolidine oxidised g −1 dry wt. h −1) and had a seasonal pattern similar to cellulase and xylanase. It was undetectable in Cistus. In both litters laccase increased significantly going from 10 to 140 μmol o-tolidine oxidised g −1 dry wt. h −1 between eight and nine months when a large increase of fungal biomass occurred (from 0.5 to 2.5 mg g −1 dry wt.). The analyses of these enzymes have shown qualitative and quantitative differences depending on the litter type and the microclimatic conditions, suggesting changes in the microbial succession.

Factors influencing changes in rainwater composition from urban versus remote regions of the Yellow Sea

Rainwater samples were collected from three stations at the Yellow Sea in 1992–1993 and analyzed for some major species (Ca2+, K+, Na+, Mg2+, NO3−, NH4+, pH, PO43−, and SO42−). Absolute concentrations and element‐to‐sodium ratios show clear seasonal variations with higher levels in winter and lower levels in summer for most of the species. Levels of major species from urban areas can be twice as high as those of remote regions, in terms of both absolute concentration and element‐to‐sodium ratio. The contrasts between urban and remote and between low and high elevations can be explained by proximity to the ocean, local pollution sources, and scavenging processes. Comparison with other world areas shows rather high levels of chemical species in rainwater from the Yellow Sea relative to remote world oceans or even some other coastal urban areas. Using sodium as a sea‐salt tracer, it was estimated that more than 50% of major species in rainwater could come from non‐marine contributions, and for some species like NH4+, NO3−, and SO42−, anthropogenic emissions are definitely the major source. The high concentration of nitrogen species and elevated N/P ratio of rainwater, as compared to riverine input, suggest the significance of atmospheric wet deposition to the marine production and biogeochemical circulation of nutrients in this region.

Seasonal variations of the sea level in the central part of the Red Sea

Seasonal sea-level changes at two coastal stations, Jeddah and Port Sudan, display higher levels in winter and lower levels in summer, showing a coherence over a distance of 300 km. The amplitude of these changes is slightly higher at Jeddah compared with that of Port Sudan. Analysis of wind stress indicates that the cross-shore component plays a dominant role in the sea-level changes at Port Sudan in contrast to Jeddah where a major part of the changes can be accounted for by the long-shore component.

Platelet and whole blood serotonin content in depressed inpatients: Correlations with acute and life-time psychopathology

Platelet or whole blood serotonin content did not differ significantly in patients with major depression compared to healthy controls, but within the patient group, platelet serotonin levels correlated negatively with severity of depression ( r = −0.49, p = 0.007). Levels were 39% lower in patients who had made a suicide attempt compared to nonattempter patients (47.2 ± 27.3 versus 77.6 ± 41.7 ng/10 8 platelets, p = 0.04). 1755 1 Conversely, comorbid borderline personality disorder (85.3 ± 41.4 ng/10 8 platelets) was associated with 31% greater platelet serotonin content than nonborderliline patients (58.9 ± 31.1 ng/10 8 platelets) and 27% greater than healthy controls (62.4 ± 19.8 ng/10 8 platelets). A pronounced seasonal variation in whole blood and platelet serotonin content was found in both patients and controls, largely due to lower levels in summer. Excluding cases tested in the summer abolished the statistically significant differences in patients with and without comorbid borderline personality disorder (BPD). Nevertheless, BPD attempters had lower serotonin levels than BPD nonattempters but higher serotonin levels than non-BPD attempters. Current hostility and a life-time history of aggression were positively correlated with platelet serotonin content ( r = 0.44, p = 0.04 and r = 0.41, p = 0.06). This study provides evidence for an association between lower platelet serotonin content and depression and suicidal behavior, and association of higher platelet serotonin content and comorbid borderline personality disorder and behavior traits such as aggressivity.

Seasonal variations in mineral concentrations in the trunk xylem sap of beech (Fagus sylvatica L.) in a 42‐year‐old beech forest stand

SUMMARYIn a 42‐yr‐old beech forest stand, growing on acid brown earth, five trees were felled every 2 wk. From their lowest trunk segments, each 100 cm in length, tracheal sap was collected by water displacement. The investigation was performed from mid‐October 1988 to mid‐October 1989, comprising a total of 130 sample trees. Xylem sap concentrations of calcium, magnesium, potassium, and manganese of 26 sampling series were analysed by atomic absorption spectrophotometry, and the pH values of fresh sap samples were determined. The seasonal variation in xylem sap concentrations of Ca, Mg and Mn in the lowest trunk sections showed a strong increase in the second half of March and in April, a decrease in May, after the leaves had expanded, a low level in summer, and a new increase in late autumn and winter. Potassium showed a different pattern with maximal xylem sap concentrations in autumn. Additionally, at four sampling dates (mid‐March, beginning of May, mid‐August and mid‐November), four trees, one at each date were cut into sections for the determination of the mineral concentrations in the xylem sap along the stem.

Timing of nitrogen application to macadamias. 2. Storage carbohydrates

Samples of wood and bark were taken monthly from macadamia (Macadamia integrifolia Maiden and Betche) tree trunks and analysed for total 'fermentable' carbohydrates. Carbohydrates (%, w/w) were high during autumn-winter and declined to low levels in summer when oil was accumulating in kernels. Reproductive growth appeared to draw heavily on carbohydrate reserves. Vegetative growth, on the other hand, was not generally reflected in lower carbohydrate levels in tree trunks. Application of nitrogen (N) during summer resulted in higher carbohydrate levels than when applied in autumn or winter. Despite these differences, there was no apparent accumulation of carbohydrates in the months directly following application of N. The low N status of control trees was not reflected in low concentrations of storage carbohydrates. Wood tissues had a higher concentration of carbohydrates than bark, perhaps reflecting the sampling procedures used. Further work to quantify the contribution of storage carbohydrates and current photosynthesis to yield is justified.

Soil acidity and Rhizobium: their effects on nodulation of subterranean clover on the slopes of southern New South Wales

Rhizobium trifolii and root nodulation were compared in acid and limed soil to investigate mechanisms by which current soil acidity on the slopes of southern New South Wales may reduce the growth of Trifolium subterraneum. Increasing soil pH increased both the rate at which Rhizobium trifolii colonized soil and the frequency of nodules/g root (NF). Thus, numbers of R. trifolii were greater in carbonate-treated soil throughout autumn and winter compared to unlimed soil. In limed soil R. trifolii were measured at 104-105/g soil as early as seedling germination, 40-200 x more than in unlimed soil. Despite this, by spring, the numbers of rhizobia in soil without lime reached large and even similar levels as occurred in limed soil. Subsequently, with the drying of soil in summer, the numbers of R. trifolii declined markedly in both untreated and limed soil. Maximum NF could not be achieved with addition of Ca without increase in pH. From the field observations and other research, a hypothetical model is proposed to explain how differences in the rates of change in rhizobial numbers due to acidity may determine nodulation (NF). Thus, it is suggested that, when there is a repetitive decline in numbers of R. trifolii to low levels in summer, their subsequent rate of increase in the following autumn influences nodule abundance. The production of DM in an acidic soil appeared to be limited by symbiotic N2 fixation since added N fertilizer removed lime response. The limitation to N2 fixation did not appear to be due to lower occupancy of nodules by Rhizobium strains with less potential for N2 fixation than those in limed soil. It is possible that the effect of acidity on NF influences DM, though sampling limitations made it difficult to generalize in this regard.

Chronic infections of Haplosporidium nelsoni (MSX) in the oyster Crassostrea virginica

Oysters inhabiting areas enzootic for the parasite Haplosporidium nelsoni (MSX) are exposed to infective particles each summer, and it is often difficult to distinguish newly acquired lesions from older infections. To study long-term parasitism without the complication of new infections, MSX-infected oysters were moved from Delaware Bay to a disease-free area on the New Jersey coast. Because infections seen after the transfer were acquired in Delaware Bay during a known infective period, it was possible to determine how long oysters remained infected and how they were affected by chronic parasitism. Chronic infections displayed the same seasonal cycle (high levels in winter and late spring, low levels in summer and early spring) that occurs in enzootic areas with annual reinfection. Within individual oysters, chronic MSX became localized, relapsed into general infections, and then became localized again in a sequence that was probably controlled by temperature. Some experimental oysters survived with MSX for at least 4 years. Hemocytosis persisted in these oysters, and their poor condition suggested that chronically infected individuals would have lowered resistance to additional stress.

Seasonality in the fluoride concentrations of pasture grass subject to ambient airborne fluorides

High winter and low summer levels in grass fluoride concentrations have been commonly attributed to growth dilution. A large number of grass fluoride records obtained from routine monitoring around two different major sources of industrial airborne fluoride pollution were considered and there were no real indications of seasonality. Further investigations carried out on grass fluoride, airborne fluorides and meteorological data indicated that grass fluoride levels were positively related to the previous seven days' ambient airborne fluorides levels. It was concluded that meteorological, microclimatic and biological factors were directly or indirectly influencing grass fluoride levels.

Seasonal variation in the chemical constituents of the brown algae Macrocystis integrifolia and Nereocystis luetkeana

Ash, mannitol, alginate content, and inclusion levels of 27 inorganic elements in the brown algae Macrocystis integrifolia and Nereocystis luetkeana were monitored monthly over a period of 2 years. In addition, the composition and viscosity of the alginate were determined. Potassium, sodium, calcium, magnesium and phosphorus were the major elements present. Others, in decreasing amounts, included iodide, strontium, boron, iron, arsenic, aluminum, zinc, barium, manganese, copper, and cobalt. Some of these elements were accumulated to high concentrations in the thallus when compared with their concentrations in seawater. Marked seasonal variations were observed for potassium and phosphate, with high levels in winter and low levels in summer. Boron and iodide showed a reverse trend. Among the major elements, sodium, calcium, and magnesium showed no seasonal variations. Most of the inorganic elements, except potassium, were more abundant in the blade compared with the stipe. Leaching experiments with organic and inorganic solvents suggested that the alkali metals, sodium and potassium, were present mostly as inorganic salts, while divalent cations, calcium, magnesium, and strontium, were probably bound to alginic acid. Organic solvents did not leach appreciable quantities of the inorganic elements. The ash content in both algae was minimum (24%) in summer and maximum (49%) during winter, mainly because of the higher concentration of potassium in winter. Nereocystis showed higher values of ash than Macrocystis, and ash content was slightly higher in the stipe than in the blade tissues. The mannitol content ranged from 2 to 16% and alginate content from 19 to 31% of dry weight, both compounds showing higher values during the summer. Far more mannitol was present in the blade than in the stipe tissue, whereas the alginic acid content was slightly higher in the stipe than in the blade tissue. The mannuronate–guluronate ratio of alginate varied between 1.2 and 1.7 and the viscosity between 800 and 2000 cps.