Seasonal changes in the content of lipids and photosynthetic pigments in a brown alga Saccharina cichorioides

Seasonal changes in the contents of lipids and photosynthetic pigments (PSP) were investigated in a brown alga Saccharina cichorioides Miyabe (Phaeophyceae, the family Laminariaceae). The content of lipids varied from 0.27 to 0.60% of the algal fresh weight. The content of glyceroglycolipids (GL) was much greater in the time of spore formation (June–July and September–October), phospholipids — in the spring and in September–October, and the content of neutral lipids — in the spring and in November. In the period of spore release (August and October), the level of GL and polyunsaturated fatty acids (PUFA) sharply decreased. A high level of PUFA was observed from March to July and in November. In August and October, the same as in the spring, the proportion of saturated fatty acids (FA) was great. The content of chlorophylls from March to November varied from 20.3 to 26.9%, and the level of carotenoids — from 10.7 to 16.1%. Total content of PSP was relatively high in March and in August–September. Free sterols accounted for 3.4–7.3% of total lipids; their proportion was greater in spring than in summer and autumn.     

Seasonal variation in the biochemical composition of particulate material collected by sediment traps at Signy Island, Antarctica

Particulate material recovered over an 18-month period from sediment traps deployed at a shallow-water nearshore Antarctic site was analysed for photosynthetic pigments, aliphatic hydrocarbons and fatty acids. All components showed a distinct seasonal variation, with high recovery rates during the summer open-water phytoplankton bloom and low rates under winter fast ice. The amount of trapped material differed between the two summers, indicating inter-annual variability of vertical flux associated with differences in the intensity of the summer phytoplankton bloom. Particulate material trapped in summer was dominated by that which originated in diatoms. High recoveries of chlorophyll a, fucoxanthin, n-C_21:6 hydrocarbon, 20:5(n-3) fatty acid and shorter chain (C₁₅–C₂₄) aliphatic hydrocarbons all pointed to a significant summer flux of ungrazed diatoms. There were, however, also signals of zooplankton grazing activity (notably pyrophaeophorbide a), and the presence of C18:4(n-3) and C22:6(n-3) fatty acids suggested a small flux of material from flagellates and other sources. Longer chain n-alkanes (C₂₅–C₃₄) indicative of nanoplankton were detected all year, but there was no significant deposition of zooplankton material in any sample. The major recovery rate of photosynthetic pigments was in late summer (February to April), and the major grazing signal occurred after the peak of the summer diatom bloom. Most of the diatom bloom appeared to settle out from the water column without being grazed. The major seasonal contrast in the biochemistry of the trapped material was the dominance of the diatom signature in summer, and in winter the predominance (but at much lower recovery rates) of material from nanoplankton. Received: 2 March 1998 / Accepted: 12 June 1998     

Reproductive biology of Philodryas patagoniensis (Snakes: Dipsadidae) in south Brazil: male reproductive cycle

The male reproductive cycle of Philodryas patagoniensis in south Brazil was described through morpho‐anatomical and histological analysis of individuals deposited in zoological collections. Spermatogenesis occurred during late autumn–winter (June–September) and spermiogenesis occurred in spring–summer (October–March). The volume of the testes was smaller (quiescent) in winter, while the tubular diameter and the epithelial height of the seminiferous tubule were larger in summer (January–March). The ductus deferens presented spermatozoa all over the year and had no seasonal variation in diameter. The length of the kidney was larger in winter–spring (July–December), although the tubular diameter and epithelium height of the sexual segment of the kidney (SSK) were larger only in winter (July–September). Total testicular regression was observed in late autumn (May), simultaneously with the peak in SSK. Therefore, at the individual level, males exhibit a discontinuous cyclical reproduction. Considering the population level, the reproductive cycle is seasonal semisynchronous, with most of the individuals showing a reproductive peak in spring–summer (October–March). Here, we present evidence to support the importance of the microscopic approach to reproductive cycle studies. Finally, we discuss the intrinsic and extrinsic factors influencing P. patagoniensis reproductive patterns.     

Effects of decadal climate change on zooplankton over the last 50 years in the western subarctic North Pacific

Decadal‐ to multi‐decadal variations have been reported in many regional ecosystems in the North Pacific, resulting in an increasing demand to elucidate the link between long‐term climatic forcing and marine ecosystems. We detected phenological and quantitative changes in the copepod community in response to the decadal climatic variation in the western subarctic North Pacific by analyzing the extensive zooplankton collection taken since the 1950s, the Odate Collection. Copepod species were classified into five seasonal groups depending on the timing of the annual peak in abundance. The abundance of the spring community gradually increased for the period 1960–2002. The spring–summer community also showed an increasing trend in May, but a decadal oscillation pattern of quasi‐30‐year cycles in July. Phenological changes coincided with the climate regime shift in the mid‐1970s, indicated by the Pacific decadal oscillation index (PDO). After the regime shift, the timing of the peak abundance was delayed one month, from March–April to April–May, in the spring community, whereas it peaked earlier, from June–July to May–June, in the spring–summer community, resulting in an overlap of the high productivity period for the two communities in May. Wintertime cooling, followed by rapid summertime warming, was considered to be responsible for delayed initiation and early termination of the productive season after the mid‐1970s. Another phenological shift, quite different from the previous decade, was observed in the mid‐1990s, when warm winters followed by cool summers lengthened the productive season. The results suggest that climatic forcing with different decadal cycles may operate independently during winter–spring and spring–summer to create seasonal and interannual variations in hydrographic conditions; thus, combinations of these seasonal processes may determine the annual biological productivity.     

Seasonal changes in the content of lipids,fatty acids,and pigments in brown alga <Emphasis Type="Italic">Costaria costata</Emphasis>

We compared the content of total lipids, particular lipid classes, fatty acids (FAs), and pigments in the brown alga Costaria costata [Turn.] Saund (Laminariaceae) in different seasons: during algal active life (April–June) and in the beginning of their degradation (the end of July). Lipids comprised only a small part of algal extractable compounds (10.9–13.4%). Their higher content was observed in May, in the period of alga preparation to sporogenesis. Polar lipids, glyceroglycolipids (GL) and phospholipids (PL), comprised a great part of total lipids in spring months and June, whereas neutral lipids, in July. GL predominated in polar lipids in spring and summer. The highest content of GL was observed in May and PL in April. Storage lipids comprised a great part of lipids in July. The content of sterols was the highest in April and May. In summer months, the content of sterols decreased and remained on unchanged level until thallus degradation. Polyunsaturated FAs (PUFAs) comprised the most part of FAs. Their highest content was observed in April. The main part of PUFAs were those of ω-3 series. In July, the level of these PUFA decreased substantially. The levels of ω-6 PUFAs were approximately similar in spring and summer months. The lowest content of monounsaturated FAs was detected in April; in May and July; the relative content of these FAs increased sharply. We also detected seasonal changes in the content of pigments and the ratios between them.     

Seasonal changes in oleosomic lipids and fatty acids of perennial root nodules of beach pea

Seasonal changes in the fatty acid composition of phospholipids (PL), monoglycerides (MG), diglycerides (DG), free fatty acids (FA) and triglycerides (TG) separated from oleosomes (lipid bodies) of perennial root nodules of beach pea (Lathyrus maritimus) were analysed. Thin layer chromatography (TLC) revealed that PL and MG are the major lipids in nodule oleosomes. The fatty acid profile and overall double bond index (DBI) varied among lipid classes depending upon the season. High DBI in PL and MG found during late winter and early spring indicated that they may play a major role in winter survival and regeneration of perennial nodules. The DBI of DG was high at the end of the fall season and the DBI of FA and TG was high in summer months. The dominant fatty acids are C16:0 followed by C18:0 and C18:1. The levels of many unsaturated fatty acids such as C18:1, C18:2 and C18:3 increased while saturated fatty acid C18:0 decreased during winter. These unsaturated fatty acids possibly play an important role in the protection of nodule cells from cold stress. Nodules seem to retain some fatty acids and selectively utilize specific fatty acids to survive the winter and regenerate in spring.     

Resource Ratios and Phytoplankton Species Composition in a Strongly Stratified Lake

The epilimnetic phytoplankton and its relations to nutrient content in Lake Verevi through the whole vegetation period in 2000 were studied. Lake Verevi (surface 12.6 ha, mean depth 3.6 m, maximum depth 11 m) is a hypertrophic hard-water lake, where the so-called spring meromixis occurs due to an extremely warm spring. Most dissolved nutrients in the epilimnion were low already in spring, and their concentrations were quite stable during the study period. The concentration of total silicon was very low in spring but increased rapidly in summer. Total phosphorus followed the pattern for stratified eutrophic lakes, and total nitrogen was quite high. The stoichiometric N:P ratio fluctuated between 25 and 81. The dynamics of phytoplankton biomass with a spring peak from April to May and a late summer peak from July to August is typical of Estonian eutrophic lakes. Green algae and chrysophytes occurred in the phytoplankton throughout the vegetation period. The spring peak was dominated by diatoms (Synedra ulna and Synedra acus var. angustissima) and the summer peak was caused by Aphanizomenon klebahnii and Ceratium hirundinella. The study showed that in physically stratified systems, the total concentration of limiting resources and plain physical factors (light and temperature) may be more important in the determination of phytoplankton dominants than different resource ratios. A combination of light and temperature optimum, along with nutrient utilization and transport capacity, effectively segregates phytoplankton species and can be used for the explanation of seasonal succession pattern.     

Seasonal levels of LH, FSH, testosterone and prolactin in adult male pudu (Pudu puda)

Seasonal levels of LH, FSH, testosterone (T) and prolactin (PRL) were determined in plasma of six captive adult male pudu (Pudu puda) kept in Concepcion, Chile. Average PRL levels exhibited one peak (28 ng/ml) in December (summer); minimal levels (3 to 6 ng/ml) were detected between April and July. FSH concentrations remained at peak levels (54–63 ng/ml) from December until March; minimal values (25–33 ng/ml) were detected from April until October. T levels exhibited two, almost equal peaks; the first peak (2.8 ng/ml) was detected in March (rut) and the second one (2.7 ng/ml) in October (spring). Both T peaks were preceded by an earlier elevation of LH in February and July (both around 1.3 ng/ml). During the fall, only the alpha male exhibited a sharp peak of T (8.4 ng/ml), whereas in the spring five out of six bucks demonstrated an increase of T levels. Two peaks of LH and T and the 4 months of elevated FSH may be related to a long period of spermatogenesis observed in this species.     

Effects of the season and growth stage on the contents of lipids and photosynthetic pigments in brown alga <Emphasis Type="Italic">Undaria pinnatifida</Emphasis>

Seasonal changes in the contents of lipids and photosynthetic pigments (PSP) in the brown alga Undaria pinnatifida (Harvey) Suringar (Phaeophyceae, Alariaceae) on different stages of its growth were studied. Lipids of all plant growth group comprised glyceroglycolipids (GL), phospholipids, and neutral lipids (NL). The ratio between these lipid groups and the content of particular lipids depended on the season and algal growth stage: NL predominated in seedlings; juvenile algae comprised approximately similar amounts of NL and GL; and in adult algae, GL predominated. In winter and spring, algal tissues contained relatively more free sterols than in summer. Total lipid content in seedlings and juvenile algae was higher then in adult plants. Lipid fatty acid (FA) composition was similar on all growth stages, but the content of major components differed; this is mainly related to 18:4 n-3, 20:4 n-6, and 20:5 n-3 acids. The predominant FAs in seedling lipids were saturated FAs, whereas in the lipids of juvenile and adult algae, polyunsaturated FAs predominated.     

Seasonal dynamics of fatty acids in the lipids of water moss <Emphasis Type="Italic">Fontinalis antipyretica</Emphasis> from the Yenisei River

Identification of lipid fatty acids (FA) and studying of their seasonal dynamics in water moss Fontinalis antipyretica from the Yenisei River were carried out by means of gas chromatography-mass spectrometry. FA composition of water moss was notable for a relatively low level of saturated acids and predominance of polyunsaturated acids (PUFA) with double bonds (accounting for more than 30% of total FA) and polyunsaturated acids with double and triple bonds (acetylenic acids, accounting for more than 40% of total FA). Among PUFA, α- and γ-linolenic (18:3ω3 and 18:3ω6), arachidonic (20:4ω6), and eicosapentaenoic (20:5ω3) acids prevailed. Relative content of PUFA from ω3-family was the greatest in spring, and the level of PUFA from ω6-group was essentially the same throughout all the seasons. In the biomass of water moss, we identified seven acetylenic acids; among them octadeca-9,12-dien-6-ynoic (6a,9,12-18:3), octadeca-9,12,15-trien-6-ynoic (6a,9,12,15-18:4), and eicosa-11,14-dien-8-ynoic (8a,11,14-20:3) acids were predominant. For the first time, in the lipids of water moss we identified an acetylenic eicosa-11,14,17-trien-8-ynoic acid (8a,11,14,15-20:4). Relative content of acetylenic acids in the total FA was great throughout the entire period of investigation with the peak accumulation in summer. Owing to a steadily high level in the biomass of water moss and the lack of other producers of these acids in the ecosystem, acetylenic FA are highly specific biochemical markers useful for the investigation of trophic interactions between higher aquatic plants and zoobenthos.     

Fatty acid composition and lipid content in the copepod <Emphasis Type="Italic">Limnocalanus macrurus</Emphasis> during summer in the southern Bothnian Sea

The lipid reserves and occurrence of the cold-stenothermic, omnivorous copepod Limnocalanus macrurus were studied in the Bothnian Sea (northern Baltic Sea) during spring and summer 2013–2014 with a special emphasis on the fatty acid composition of adults and their potential food. The individual total wax ester (WE) content, determined from the size of oil sacs in the prosoma, ranged on average from 1.3 to 2.6 µg, and showed a decreasing trend towards September. Lipids were dominated by fatty acids 16:0, 18:1(n-9), 18:2(n-6), 20:5(n-3) and 22:6(n-6), forming 56–61% of total fatty acids in June–September. Decreasing abundance of adults and reduction of the lipid storage implied that during summer adults suffered from starvation and, as a result, became eliminated from the population. The lipid content and dietary fatty acid markers suggested that in May, adult L. macrurus utilized the phytoplankton bloom, consisting mainly of diatoms and dinoflagellates, but later, during July–September, consumed either algae or heterotrophic organisms sinking from upper water layers or crustaceans inhabiting the same deeper water layers as L. macrurus. In the face of the climate change, the rising temperatures may force L. macrurus permanently to deeper water levels. If also the food resources are limited, we conclude that the summer season may act as a bottleneck limiting the propagation of L. macrurus and having implications further along the food web.     

Seasonal maturity development of Baltic cod in different spawning areas: importance of the Arkona Sea for the summer spawning stock

We investigated the seasonal maturity development of cod in four areas of the Baltic Sea. Two different spawning peaks were identified and found to be consistent over the period 1992–2005. In the Kiel Bight and Mecklenburg Bight (ICES SD 22) a spawning peak was observed from March to April (spring spawning). In the areas of the Arkona Sea (ICES SD 24) and Bornholm Sea (ICES SD 25) the spawning peak occurred during summer. In the Bornholm Sea, the main spawning activities began in June and ended in September, with a spawning peak in June–August (summer spawning). In the Arkona Sea, which is a transition area between the Mecklenburg Bight and the central Baltic Sea, spawning began in March and lasted until July, with a spawning peak in June–July (summer spawning). Seasonal maturity development and proportions of spawning cod in June in the Arkona Sea were similar to that of the Bornholm Sea. In addition, the proportion of spawning cod in the Arkona Sea was positively correlated with the size of the spawning stock in the Bornholm Sea. Our results provide evidence of a spatial expansion of spawning activities of the summer spawning stock from the eastern Baltic Sea into the Arkona Sea. Therefore, the Arkona Sea should be considered as one of the spawning habitats of the summer spawning stock of Baltic cod.     

Seasonal composition of lipids, fatty acids, and sterols in the edible red alga Grateloupia turuturu

Composition of lipids, sterols, fatty acids (FA), and phospholipids in the edible Rhodophyta Grateloupia turuturu from Britanny, France, was investigated over four seasons in order to identify compounds with potential benefits in health and nutrition. The lipid content was found to vary from 3.3 to 4.1 % dry weight. No marked variations were observed for glycolipids accounting for 42.3–46.8 %, whereas neutral lipids and phospholipids fluctuated from 20.1 % (summer) to 41.8 % (winter), and 11.2 % (winter) to 33.4 % (summer), respectively. Polyunsaturated FA of the total lipids were found from 20.4 % (winter) to 31.1 % (summer), including 20:5 ω3 acid as the major one (up to 16.3 % in summer). Phosphatidylcholine (20.0–43.7 %) and phosphatidylserine (24.6–37.5 %) were the dominant phospholipids in all seasons. Compounds of interest were identified in minor amounts such as squalene, α-tocopherol, phytonadione (vitamin K₁), cholesteryl formate, cholest-4-en-3-one, and cholesta-4,6-dien-3-one. Cholesterol was the major sterol with a lower content in spring and summer.     

Fatty acid compositions of arthropod and cephalopod photoreceptors: interspecific,seasonal and developmental studies

Fatty acid compositions of the compound eyes of insects (soldier-bug, Hemiptera, and silk moth, Lepidoptera), crustaceans (crayfish and grapsid crab, Decapoda) and inner and outer segments of visual cells of a squid (Cephalopoda, Mollusca) were analyzed by gaschromatography for interspecific comparison. Fatty acid compositions showed great variation among species. In insect compound eyes, 16:0 and 18:0 were the main saturated fatty acids, and 18:1 was the dominant unsaturated fatty acid. Silk moth eyes contained, in addition, considerable amounts of 18:2 and 20:5. In crustacean compound eyes, the main saturated fatty acids were 16:0 and 18:0, and 14:0 (5.0%) was only detected in grapsid crabs; the main unsaturated fatty acids were 20:4, 20:5 and 22:6. Both whole eyes and rhabdom fraction of crayfish showed similar profiles of fatty acid compositions. Both inner and outer segments of squid retinae were characterized by high amounts of unsaturated fatty acids, especially 22:6. Compound eyes of grapsid crabs were used for the experiments on seasonal changes of fatty acid compositions. UFA/SFA ratios (weight in % of unsaturated fatty acids saturated fatty acids) were lowest (1.0) in July and highest (2.5) in March, and unsaturation indexes (average number of double bonds per molecule) were lowest (1.5) in July and highest (2.3) in March. Fatty acids 18:0 and 20:1 showed a significant correlation with the changes of seasonal temperature. Fatty acid analysis of the developing compound eyes of silk moths during the pupal stage revealed that eicosapentanoic acid (20:5) increased remarkably in parallel with the development of photoreceptive membranes, the rhabdoms. This suggests that eicosapentaenoic acid may play an important role in formation and function of rhabdoms.     

Seasonally different response of photosynthetic activity to daytime and night‐time warming in the Northern Hemisphere

Over the last century the Northern Hemisphere has experienced rapid climate warming, but this warming has not been evenly distributed seasonally, as well as diurnally. The implications of such seasonal and diurnal heterogeneous warming on regional and global vegetation photosynthetic activity, however, are still poorly understood. Here, we investigated for different seasons how photosynthetic activity of vegetation correlates with changes in seasonal daytime and night‐time temperature across the Northern Hemisphere (>30°N), using Normalized Difference Vegetation Index (NDVI) data from 1982 to 2011 obtained from the Advanced Very High Resolution Radiometer (AVHRR). Our analysis revealed some striking seasonal differences in the response of NDVI to changes in day‐ vs. night‐time temperatures. For instance, while higher daytime temperature (T_max) is generally associated with higher NDVI values across the boreal zone, the area exhibiting a statistically significant positive correlation between T_max and NDVI is much larger in spring (41% of area in boreal zone – total area 12.6 × 10⁶ km²) than in summer and autumn (14% and 9%, respectively). In contrast to the predominantly positive response of boreal ecosystems to changes in T_max, increases in T_max tended to negatively influence vegetation growth in temperate dry regions, particularly during summer. Changes in night‐time temperature (T_min) correlated negatively with autumnal NDVI in most of the Northern Hemisphere, but had a positive effect on spring and summer NDVI in most temperate regions (e.g., Central North America and Central Asia). Such divergent covariance between the photosynthetic activity of Northern Hemispheric vegetation and day‐ and night‐time temperature changes among different seasons and climate zones suggests a changing dominance of ecophysiological processes across time and space. Understanding the seasonally different responses of vegetation photosynthetic activity to diurnal temperature changes, which have not been captured by current land surface models, is important for improving the performance of next generation regional and global coupled vegetation‐climate models.     

Variation in growth,yield and protein concentration in <Emphasis Type="Italic">Saccharina latissima</Emphasis> (Laminariales,Phaeophyceae) cultivated with different wave and current exposures in the Faroe Islands

Ropes seeded directly with Saccharina latissima were deployed at different exposures (sheltered, current exposed and wave exposed) in a Faroese sound and characteristics of growth and quality of the biomass and surroundings were evaluated during the growth season from March to August 2015. Saccharina latissima individuals cultivated at the current exposed location were heavier compared to the individuals cultivated at the other locations; however, the total biomass yield was significantly lower at the current exposed location. The protein and nutritional value of the biomass varied with season but showed no correlation with exposure. The highest protein levels and EAA (essential amino acid) score were measured in the spring (April and May) samples. The amino acid composition was dominated by glutamate followed by aspartic acid; however, this was replaced by methionine in the July samples. Total Kjeldahl nitrogen was significantly higher in May and August compared to July, and the nitrate concentration in the biomass was significantly lower in May and August compared to July. Nitrate was most available in the seawater at the time of deployment (3rd of March) and decreased during spring and summer. Saccharina latissima was cultivated successfully at the sheltered, current exposed and wave exposed locations using a direct seeding method. However, our results indicate that the lower biomass yield at the current exposed cultivation location compared to the sheltered and wave exposed are due to the direct seeding method, and possible limitations using this method need further testing and optimization.     

Photosynthetic activity of epilithic algal communities in sections of the Torna stream (Hungary) with natural and modified riparian shading

The photosynthetic activity of epilithon grown in the Torna-stream (Hungary) was studied. Samples were collected from natural sections with closed canopy and natural stream bed and from modified sections with trapezoid river bed and shores lacking riparian vegetation. We assumed that human modifications would have a significant impact on epilithic photosynthesis, and therefore expected to observe corresponding changes in photosynthesis–irradiance (P–I) parametric. The laboratory P–I measurements were carried out monthly between April 2008 and September 2009 with epilithon after 3 weeks of in situ colonization. The maximum rate of the photosynthesis (P _max) correlated positively with the chlorophyll a content of the samples. Natural sites had lower biomass and P _max values than modified sites, and the biomass differed substantially in spring and summer, the P _max differed significantly only in spring. Natural sections had higher biomass-specific photosynthesis values than modified sections in all seasons, but the difference was significant only in summer–autumn: in summer the samples from the natural sections had significantly higher photosynthetic efficiency. In spring and summer, the photoadaptation parameters (I _k ) of communities grown in modified sections were substantially higher than in natural sections. Light availability appeared to be the major factor regulating the seasonal photosynthetic activity of epilithic communities.     

Seasonal variation in phenolic composition, antibacterial and antioxidant activities of Ulva rigida (Chlorophyta) and assessment of antiacetylcholinesterase potential

The phenolic composition and antibacterial and antioxidant activities of the green alga Ulva rigida collected monthly for 12 months were investigated. Significant differences in antibacterial activity were observed during the year with the highest inhibitory effect in samples collected during spring and summer. The highest free radical scavenging activity and phenolic content were detected in U. rigida extracts collected in late winter (February) and early spring (March). The investigation of the biological properties of U. rigida fractions collected in spring (April) revealed strong antimicrobial and antioxidant activities. Ethyl acetate and n-hexane fractions exhibited substantial acetylcholinesterase inhibitory capacity with EC₅₀ of 6.08 and 7.6 μg mL^?1, respectively. The total lipid, protein, ash, and individual fatty acid contents of U. rigida were investigated. The four most abundant fatty acids were palmitic, oleic, linolenic, and eicosenoic acids.     

Early life history timings in marbled rockcod (Notothenia rossii) fingerlings from the South Shetland Islands as revealed by otolith microincrement

Although it has been reported that Notothenia rossii elsewhere hatches in spring, our daily increment back-counting from the capture date in otoliths of fingerlings caught in Potter Cove, South Shetland Islands, in the 2000s, showed two main periods of larval hatching, one in summer (February–March) and another in winter (July). In concordance, the simultaneous presence of two cohorts born the same year was identified in the age/length frequency distribution of fish sampled in spring 2010, which belonged to biological ages 0+ and 1+ and hatched, respectively, in summer and winter–spring. Maximum and minimum ages of pelagic blue-phase and demersal brown-phase fingerlings were, respectively, 227 and 240 days, indicating a demersal settlement after about 8 months from hatching. The estimated growth rate was 0.23–0.33 mm/day, equivalent to that of South Georgia fingerlings and higher than those of other nototheniids of similar size range. Based on early life events associated with the hatching periods, two types of life cycles are hypothesised for South Shetland fingerlings. The pelagic blue-phase fingerlings (6.5–7.6 cm TL, age group 0+) hatched in July (winter cohort), entering in Potter Cove in February–March. The brown-phase fingerlings (6.3–10.6 cm, mostly of age group 0+) hatched in February–March (summer cohort) and were collected in the cove in spring (the smaller specimens) or in summer (the larger ones). Finally, early juveniles (10.7–15.5 cm, age group 1+) hatched in winter, mainly in July (winter cohort), entering in the cove the following year to spend the second winter inshore.     

pH and CO<Subscript>2</Subscript> effects on <Emphasis Type="Italic">Coelastrella</Emphasis> (<Emphasis Type="Italic">Scotiellopsis</Emphasis>) <Emphasis Type="Italic">rubescens</Emphasis> growth and metabolism

We studied effects of рН and СО₂ enrichment on the physiological condition and biochemical composition of a carotenogenic microalga Coelastrella (Scotiellopsis Vinatzer) rubescens Kaufnerová et Eliás (Scenedesmaceae, Sphaeropleales, Chlorophyceae), a promising source of natural astaxanthin. The microalga was grown at a constant pH (5, 6, 7 or 8) maintained by direct СО₂ injection. The air-sparged culture served as the control. Cell division rate and size, dry biomass productivity, the rates of nitrogen and phosphorus uptake as well as photosynthetic pigment and total lipid content and fatty acid composition were followed. С. rubescens possessed a narrow-range рН tolerance (the optimum рН 6–7). Under these conditions, the highest values of the maximum (1.0–1.1 1/day) and average (0.3–0.35 1/day) specific growth rate, chlorophyll а (4.8–4.9%) and total carotenoid dry weight percentages (1.7–1.8%) were recorded. Cell lipid fatty acid unsaturation index (1.851) and polyunsaturated fatty acid percentage (36–39%) and С18:3 ω3/С18:1 ω9 ratio (3.8–4.5) were also the highest under these conditions. A decline of рН to 5 brought about severe stress manifesting itself as a cell division cessation, photosynthetic apparatus reduction, two-fold increase in cell volume, accumulation of dry weight and lipids and a considerable decline in fatty acid unsaturation. Cultivation of С. rubescens without СО₂ enrichment resulted in a rapid alkalization of the medium to рН 9.5–10.5 impairing the physiological condition of the cells. Reasons of the deteriorative effects of suboptimal pH values on the physiological condition of C. rubescens are discussed.