Egg capsules, eggs and embryos of the southwestern Atlantic gastropod Coronium coronatum (Gastropoda: Muricidae)

The egg capsules, eggs and embryos of the muricid gastropodCoronium coronatum are described for the first time. Capsulesare sessile, bulliform, semi-circular, with a plug in the dorsalcenter. Sutures split the capsule into two asymmetrical halves.Recently laid capsules showed the presence of 3639 (n = 2) uncleavednurse eggs with a diameter of 180–210 µm (mean= 197.4 ± 8.9). The number of early embryos was 9–11.The size of the embryos was 320 x 320 to 820–880 µm.Nine pre-hatching embryos of 3.94 mm (n = 8, SD = 0.32)were found inside the older capsule. SEM illustrations of embryosand radulae are provided. Comparison of shell and radula ofembryos with the protoconch and radulae of adults of C. coronatumrevealed that the capsule belongs to this species. (Received 18 March 2006; accepted 10 October 2006)     

Population dynamics of Corbicula fluminea (Bivalvia) in the Paraná River Delta (Argentina)

Benthic individuals and drifting planktonic juveniles of Corbicula fluminea were sampled in the Lower Delta of the Paraná River (Argentina) at monthly intervals between October 1995 and October 1996. Densities of settled clams above 1 mm, around 300–1000 ind. m-2, varied little throughout the year. Below 1 mm benthic juveniles, on the other hand, showed a single conspicuous abundance peak in October-November (up to 1722 ind. m-2), and were practically absent during the rest of the year (overall annual mean: 1070 ± 797 ind. m-2). Drifting juveniles showed one major peak in December 1995 (160 ind. m^-3), and a minor one at the end of March (24 ind. m^-3). Length-frequency analyses of the monthly field data clearly indicate a highly structured population with a single well defined reproduction period centered on October–November. Population parameters derived from the seasonally oscillating version of von Bertalanffy's growth formula were as follows: maximum shell length: 32 mm (maximum observed shell length: 33 mm); growth constant: 0.65; growth seasonality (i.e., span of summer-to-winter growth-rate difference): 0.7; winter point (i.e., time of the year when growth is minimum): 0.5 (June–July); estimated size range for one year-old individuals: 15.3–22.4 mm; for two years: 23.5–27 mm, and three years: 27.5–29.3 mm. Comparison with previous data confirm the influence of water temperature on the clam's reproduction and growth and furnish additional evidence suggesting that food availability may be as important for recruitment as thermic regimes. Contrasts between traits of the population analyzed herein with those described previously from a nearby (ca. 10 km) site more influenced by industrial pollution point at the influence of water quality on Corbicula's recruitment and growth. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tree-ring variation,wood formation and phenology of beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) from a representative site in Slovenia,SE Central Europe

Long-term variation in tree-ring widths (1873–2006) and intra-annual dynamics of cambial activity and tree-ring formation in 2006 were studied in mature beech (Fagus sylvatica L.) trees at a typical forest site near Ljubljana (46°N, 14°40′E, 400 m a.s.l.) and related to leaf phenology and climate data. Tree-ring widths were negatively affected by minimum March and maximum August temperatures and favoured by May and July precipitation. Precipitation of the previous August and temperature of the previous November also had a positive effect. Leaf unfolding was affected by March and April temperatures, occurring later if they were low. Leaf yellowing was positively affected by minimum July temperatures and negatively by September precipitation. In 2006, leaf unfolding occurred on 16 April and was immediately followed by reactivation of cambium at breast height of the trees. One week later, the cambium obtained its maximum width (around 11 cell layers) and the rate of division increased until the end of May/beginning of June. By the end of June, 75% of the tree-ring was formed. Cambial cell divisions stopped from the end of July to mid-August. The average time of cambial activity was 100 days. Leaf yellowing occurred at the end of October, i.e. nearly 2 months after the cessation of cambial cell division. We discuss the usefulness of a combination of long-term (tree-ring width and phenology) and short-term (wood formation at a cellular level) data to understand better the environmental signals registered by a tree during growth.     

POPULATION DYNAMICS OF ZEBRA MUSSELS DREISSENA POLYMORPHA (PALLAS, 1771) DURING THE INITIAL INVASION OF THE UPPER MISSISSIPPI RIVER, USA

The aim of this study was to document and model the populationdynamics of zebra mussels Dreissena polymorpha (Pallas, 1771)in Pool 8 of the Upper Mississippi River (UMR), USA, for fiveconsecutive years (1992–1996) following their initialdiscovery in September 1991. Artificial substrates (concreteblocks, 0.49 m² surface area) were deployed on or aroundthe first of May at two sites within each of two habitat types(main channel border and contiguous backwater). Blocks wereremoved monthly (30 ± 10 d) from the end ofMay to the end of October to obtain density and growth information.Some blocks deployed in May 1995 were retrieved in April 1996to obtain information about over-winter growth and survival.The annual density of zebra mussels in Pool 8 of the UMR increasedfrom 3.5/m² in 1992 to 14,956/m² in 1996. The average May–Octobergrowth rate of newly recruited individuals, based on a von Bertalanffygrowth model fitted to monthly shell-length composition data,was 0.11 mm/d. Model estimates of the average survivalrate varied from 21 to 100% per month. Estimated recruitmentvaried substantially among months, with highest levels occurringin September–October of 1994 and 1996, and in July of1995. Recruitment and density in both habitat types increasedby two orders of magnitude in 1996. Follow-up studies will benecessary to assess the long-term stability of zebra musselpopulations in the UMR; this study provides the critical baselineinformation needed for those future comparisons. (Received 5 November 2004; accepted 30 September 2005)     

The reproductive cycle,size at maturity and fecundity of garfish (<Emphasis Type="Italic">Belone belone</Emphasis>, L. 1761) in the eastern Adriatic Sea

A recent study concerning the reproductive biology of the garfish (Belone belone, L. 1761) has been carried out in the eastern part of the Adriatic Sea along the Croatian coastline. Specimens of the fish (N = 3,393) were collected over a 6-year period (2003–2008). Their length varied between 20.8 and 75.4 cm (mean ± SD = 38.3 ± 7.94). Female garfish were dominant in larger length groups being most apparent during the resting phase of sexual cycle and in the peak of the spawning period, occurring in April and May. The sexual ratio of all specimens was m/f = 0.98. Males were prevalent in March—at the beginning of the highest spawning activities. Fifty percentage of the garfish population sexually matured at 28.5 cm of total length. Males and females reached their sexual maturity at 28.0 and 31.5 cm of total length, respectively. Spawning began in January peaking during March to May. According to their maturity stages, gonad weight and the gonadosomatic index, males began to spawn one month earlier (April) than females (May). The mean batch fecundity of garfish was 1,242.46 ± 843.64 of matured oocytes per ovary. Matured oocyte diameters ranged from 1.223 to 4.283 mm with the mean value of 2.269 ± 0.332 mm.     

Assessment of optimal depth and photon irradiance for cultivation of the brown alga, <Emphasis Type="Italic">Sargassum fulvellum</Emphasis> (Turner) C. Agardh

This study was aimed at determining the optimal depth and photon irradiance for growth of Sargassum fulvellum. Sampling and measurement of underwater irradiance were carried out at farms cultivating S. fulvellum at Wando, southwestern coast of Korea, from May 2004 to April 2005. Growth of thalli, underwater irradiance and photosynthetic quantum yield were measured over a range of depths for three culture stages. During their nursery cultivation stage (Stage I), length increase was greatest at 1.5 m depth (2.5 ± 0.2 cm), where the average midday irradiance over 28 days was 488 ± 58 μmol photons m⁻² s⁻¹. During the pre-main cultivation stage (Stage II), the greatest length increase occurred at 1 m depth (10.9 ± 0.1 cm) with an average irradiance of 845 ± 169 μmol photons m⁻² s⁻¹. For the main cultivation stage (Stage III) of the alga, thalli showed maximal length growth in March and early April at depths of 1–2 m and 3 m. These results suggest that growth at each cultivation stage of S. fulvellum could be controlled by depth of cultivation rope. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Studies of Growth and Flowering in Picea sitchensis (Bong.) Carr. 2. Initiation and Development of Male, Female and Vegetative Buds

Vegetative shoots from the base of the crown, and from partsof the tree likely to form male or female buds, were collectedfrom 40–years–old trees of Picea sitchensis (Bong.)Carr. throughout the 1973–4 annual growth cycle. The morphologyand growth rates of the terminal buds on these shoots were assessed. Bud scale primordia were formed most quickly in the female position,at an intermediate rate in the male position and most slowlyin the basal vegetative position during April, May and June.In July and early August the apical meristems swelled to formdomes and continued to grow at the same relative rates in themale, female and basal vegetative positions. Reproductive budswere first morphologically distinct in late August and sporangiaappeared in October. Dormancy, defined by the pause in apicalvolume increase, extended from mid-October to mid–March.Young strobili grew much faster than basal vegetative shootsof the same age between mid–March and bud burst in lateApril. Throughout the growth cycle, external changes in budsize reflected changes in size of the apical meristem, youngstrobihis or young vegetative shoot inside the bud. It is proposed that the rate of growth of an apical meristemmay be causally related to the type of bud which subsequentlydevelops from it. Sitka spruce, Picea sitchensis, bud development, morphology, growth of apical dome, flowering     

Reproductive Strategies of <Emphasis Type="Italic">Trachypithecus pileatus</Emphasis> in Arunachal Pradesh,India

We studied reproductive behavior of free-ranging capped langurs (Trachypithecus pileatus) in the Pakhui Wildlife Sanctuary, Arunachal Pradesh, India. Four species of primates —Trachypithecus pileatus, Macaca mulatta, M. assamensis, and Nycticebus bengalensis— live there. We studied the mating seasons, mating frequency, copulatory attempts, time spent in copulation, and interval between 2 successive copulations, gestation length, and interbirth interval of 4 groups of capped langurs during 2001–2003. We observed 2 mating seasons in a year. The first was larger, comprising 5 months (September–January), and the second was short, April and May. Mating was intensive in the morning session (0600–1000 h); 57% of total mating events occurred then. The average gestation period was 200 d. November was the most favorable month for breeding. In a year, 107 mating events occurred involving 5 adult females. Average time per mounting attempt is 12 s. Duration of mounting was the maximum in November. Interbirth interval was 23 months and 10 d. The birth season was 129 days, December–April; 53% of births occurred in February and March. Average birth rate is 0.386 birth/female/yr.     

Growth and development of Neocalanus flemingeri/plumchrus in the northern Gulf of Alaska: validation of the artificial-cohort method in cold waters

In situ growth and development of Neocalanus flemingeri/plumchrusstage C1–C4 copepodites were estimated by both the artificial-cohortand the single-stage incubation methods in March, April andMay of 2001–2005 at 5–6°C. Results from thesetwo methods were comparable and consistent. In the field, C1–C4stage durations ranged from 7 to >100 days, dependent ontemperature and chlorophyll a (Chl a) concentration. Averagestage durations were 12.4–14.1 days, yielding an averageof 56 days to reach C5, but under optimal conditions stage durationswere closer to 10 days, shortening the time to reach C5 (fromC1) to 46 days. Generally, growth rates decreased with increasingstage, ranging from 0.28 day^–1 to close to zero but weretypically between 0.20 and 0.05 day^–1, averaging 0.110± 0.006 day^–1 (mean ± SE) for single-stageand 0.107 ± 0.005 day^–1 (mean ± SE) forartificial-cohort methods. Growth was well described by equationsof Michaelis–Menten form, with maximum growth rates (G_max)of 0.17–0.18 day^–1 and half saturation Chl a concentrations(K_chl) of 0.45–0.46 mg m^–3 for combined C1–3,while G_max dropped to 0.08–0.09 day^–1 but K_chl remainedat 0.38–0.93 mg m^–3 for C4. In this study, in situgrowth of N. flemingeri/plumchrus was frequently food limitedto some degree, particularly during March. A comparison withglobal models of copepod growth rates suggests that these modelsstill require considerable refinement. We suggest that the artificial-cohortmethod is the most practical approach to generating the multispeciesdata required to address these deficiencies.     

Increasing nitrogen limitation during summer in the List Tidal Basin (Northern Wadden Sea)

The European Wadden Sea is characterized by high nutrient loads and turbid waters. Riverine nutrient input showed a gradual decrease since the mid 1980s. In the List Tidal Basin (Northern Wadden Sea) the frequency of low NO₃ values in summer has increased and decreasing mean annual suspended matter concentrations indicate an increasing underwater irradiance. We used an approach developed by Cloern (Aquat Ecol 33:3–16, 1999) to analyze resource limitation of nitrogen (DIN) and underwater irradiance for phytoplankton growth in the List Tidal Basin between 1985 and 2005. Comparing our results to other studies suggests that the List Tidal Basin is one of the most nitrogen sensitive areas of the European Wadden Sea. In 2005, phytoplankton growth was light limited from January to May and in November and December, co-limited by both resources in June, July and October, and nitrogen limited in August and September. Comparing phytoplankton growth limitation in the periods 1985–1991 and 1999–2005, the duration of nitrogen limitation during summer is significantly longer in the second period (2.1 ± 0.9 months) than in the first (0.7 ± 0.5). Moreover, light limitation in September and October has decreased in the second period. A decreasing phytoplankton growth during summer is in line with former studies from the List Tidal Basin, which showed that summer chlorophyll concentrations have decreased since the mid 1980s. We suggest that nowadays less food is available for higher pelagic and benthic trophic levels due an increased nitrogen limitation during summer.     

A snail's space sets a snail's pace: movement rates of lavigeria gastropods in lake tanganyika, East africa

Endemic Lavigeria gastropods are diverse and common in the benthosof Lake Tanganyika. We used in situ studies of marked individualsto quantify rates of daily movement by three species, and testthe effects of size, sex, reproductive status and parasitismon movement. Average net travel distance was 50 cm day^–1,which corresponds to about 20 times shell length. Male L. coronatamoved significantly farther than L. coronata females or L. grandis,and L. nassa of either sex. There were also significant differencesamong individuals within each group; however, these differenceswere not predicted by size, reproductive status or parasitism.We interpret greater movement of L. coronata males as a reflectionof mate searching; the ratio of males to non-brooding, non-parasitizedfemales was three times as high in L. coronata (21:1) as inthe other species (6:1). Our results indicate that these snailsare capable of moving considerable distances, and that the highlylocalized distribution of L. coronata populations is not simplya reflection of limited movement by individual snails. (Received 20 September 2006; accepted 1 March 2007)     

Ecological investigations on the zooplankton community of Balsfjorden, northern Norway: population dynamics of the euphausiids Thysanoessa inermis (Kroyer), Thysanoessa raschii (M.Sars) and Meganyctiphanes norvegica (M.Sars) in 1976 and 1977

The population dynamics of the euphausiids Thysanoessa inermis(Kröyer), T. raschii (M.Sars), and Meganyctiphanes norvegica(M.Sars) have been followed in Balsfjorden in 1976 and 1977.Seasonal variations in length-frequency distributions, growthin carapace length, sex-ratio, and spermatophore productionand attachment are presented and discussed in relation to changesin hydrography and phytoplanlcton standing-crop. An annual generationof T. inermis and T. raschii was spawned in April and May. Eggsand larvae of M. norvegica were not found in Balsfjorden, indicatingthat recruitment occurs from outside the fjord. T. inermis andT. raschii reached maximum carapace lengths of 7–8 mmand 6–7 mm respectively and had life-spans of c. 2 years3 months. M. norvegica had a life-span of c. 2 years 6 monthsand reached a maximum carapace length of c. 12.5 mm. In bothT. inermis and T. raschii 0-group underwent the greatest lengthincreases from May to October, I-group from March to Augustand II-group from April to June. The population structure, growthpatterns and growth periods of M. norvegica were difficult todiscern. The phytoplanlcton cycle appears to be the dominantfactor regulating both growth and spawning of the Thysanoessaspp in Balsfjorden, while temperature has no obvious influence.     

Seasonal variability and inter-specific differences in hatching of calanoid copepod resting eggs from sediments of the German Bight (North Sea)

Hatching experiments were conducted on sediment samples collectedon seven cruises between March 2002 and February 2003, at fourstations near Helgoland (54°11'N, 7°53'E). Samples wereincubated for up to 12 months and examined weekly for calanoidcopepod nauplii. 12807 nauplii hatched in total. Of these 36.43%were stage N1 (pooled), 44.08% were Temora longicornis (stageN2 and older), and 17.96% were Centropages hamatus (stage N2and older). Some Acartia spp. and an unidentified species werefound, too. Hatching varied significantly between sampling dates.At three stations, counts of all nauplii peaked in samples takenin April, while at one station the maximum was recorded in thesample collected in October. The seasonal pattern of hatchingwas similar in T. longicornis and C. hamatus. In March, April,October and February numbers of all nauplii were initially low,but increased over the following 2–3 weeks. In June, Augustand December, however, average numbers were comparatively highat first, but declined thereafter. In three of the four samplesthat were incubated for 12 months nauplii hatched from the sedimentfor the entire experimental period. Temora longicornis and C.hamatus displayed clearly distinct patterns of hatching in theselong-term incubations.     

Species composition and seasonal variations of ichthyoplankton of the coastal zone of Vostok Bay (Peter the great bay,sea of Japan) collected at light stations

We summarize the results of a study of the taxonomic composition and seasonal variations of ichthyoplankton in Vostok Bay. Samples were collected during 2003–2008 at a stationary light station located on the mooring module of the experimental biological station Vostok (Institute of Marine Biology). Within the observation period, larval and juvenile fish of 67 species belonging to 11 orders and 30 families were found in 412 samples. The seasonal dynamics of species composition of ichthyoplankton were examined over the period from March to November. The number of species in the samples changed from 40–36 in April–May, respectively, to 6 species in October. The contribution of resident species and southern migrants to the ichthyoplankton samples was estimated. The light station sampling has proven to be most effective in studying the species diversity of the ichthyofauna in Vostok Bay. Using light station sampling, 18 fish species were found that were not recorded using other sampling techniques.     

A field study on the growth and development ofDumontia contorta

Young, crustose plants ofDumontia contorta grown in the laboratory from carpospores were transferred in September 1983 to their natural habitat in Lake Grevelingen (SW Netherlands). The number of upright fronds per crust, length of upright fronds, and diameter of crusts were determined monthly until October 1984 and the presence of tetrasporangia was noted. Although fronds were initiated from crusts throughout the period of short daylengths (<13 h light per day, i.e. from September to March), the majority of the fronds was initiated in October and November when short daylengths coincided with optimum temperatures for frond initiation (ca 10–20°C). By April, i.e. within 5–6 months, these plants had reached maximum sizes and had become fertile; subsequently, the plants decayed. The successively smaller numbers of fronds that were formed in December and January also reached maximum sizes after ca 5–6 months, i.e. by May and June, but these fronds remained much smaller than the fronds initiated in October–November, possibly because of lower temperatures and light levels at the start of their growth. It is suggested that the fronds have a fixed maturation period (ca 5–6 months) irrespective of their size and the moment of their initiation. Crusts were shown to “oversummer” and to produce new fronds at the onset of shortday conditions in September 1984. Dedicated to Dr. Dr. h. c. Peter Kornmann on the occasion of his eightieth birthday.     

Reproduction of plateau pika (<Emphasis Type="BoldItalic">Ochotona curzoniae</Emphasis>) on the Qinghai–Tibetan plateau

The reproduction of the plateau pika (Ochotona curzoniae) was investigated in Guoluo District at an elevation of 4,000 m on the Qinghai–Tibetan plateau, China, from April 2007 to August 2008. Reproduction was seasonal, and the breeding season lasted from April to late June/early July. Adults produced two litters in each year, and the mean litter size, estimated by counting the number of embryos in utero, was 3.3 ± 0.1 (n = 52) in 2007 and 3.2 ± 0.1 (n = 66) in 2008. The timing of reproduction showed high inter-annual variation; lower precipitation and the concomitant delay in spring vegetation phenology may have retarded the onset of the breeding season in 2007 compared with 2008. The most frequent litter sizes were 3 and 4, which together comprised 71.2% and 83.3% of litters in May and June of 2007 and 2008, respectively. Compared with previous studies, reproduction was highly variable between geographic areas. Pikas produced between one and five litters per year in different regions of the plateau over different breeding seasons. This geographic and inter-annual variation appeared to be associated with the duration of plant growth at each site, suggesting that plateau pikas adjust the length of their breeding season to match the period when sufficient energy is available to support the high energy demands of reproduction.     

AGE AND GROWTH OF LITHOPHAGA LITHOPHAGA (LINNAEUS, 1758) (BIVALVIA: MYTILIDAE), BASED ON ANNUAL GROWTH LINES IN THE SHELL

The life span of Lithophaga lithophaga was found to be >54 years when the annual growth lines in longitudinal shellsections were counted. The age determination was confirmed bya) length frequency histograms, b) the time taken for the formationof annual and reproduction rings and c) by determining the agein different parts of the shell. The age of individuals of thesame length varies, for example, individuals with a length of5.0 ± 0.2 cm range in age from 18–36 years. Theoldest individuals were found at depths of 1–5 m. Maximumgrowth (75%) was observed from the end of spring to the beginningof summer. The increase in length of the borehole, which was1.5 times greater than the length of L. lithophaga, was continuousand occurred at a faster rate in winter. Parameters, such as,shell length, age, axes, the occurrence of abnormal, white andpearlcontaining forms and wetflesh weight varied significantlywith depth. There was no variation in the ratio of boreholevolume/shell volume. On the basis of the above parameters, andalso the population density, each depth at which samples werecollected, was graded. Depths of 2–4 m were found to bethe most suitable for growth and habitation. Depths of 0–1m were most inhospitable due to strong wave action and the directeffect of the atmosphere. (Received 15 August 1994; accepted 17 March 1995)     

Techniques of EMG signal analysis: detection, processing, classification and applications (Correction)

This paper was originally published in Biological Procedures Online (BPO) on March 23, 2006. It was brought to the attention of the journal and authors that reference 74 was incorrect. The original citation for reference 74, “Stanford V. Biosignals offer potential for direct interfaces and health monitoring. Pervasive Computing, IEEE 2004; 3(1):99–103.” should read “Costanza E, Inverso SA, Allen R. ‘Toward Subtle Intimate Interfaces for Mobile Devices Using an EMG Controller’ in Proc CHI2005, April 2005, Portland, OR, USA.”     

Food web interactions in a Calanus finmarchicus dominated pelagic ecosystem--a mesocosm study

The significance of nauplii versus copepodite stage V of Calanusfinmarchicus grazing and their effects on the structure of thefood web were investigated during two sampling periods of 7–8days in March and April in experimental mesocosms held in aNorwegian fjord over a 2 month period. The mesocosms were manipulatedby the addition of two different levels of inorganic nutrients(control versus enriched). During the ‘naupliar’period in March, the phytoplankton was characterized by a diatombloom while during the ‘copepodite’ period in April,it was in a post-bloom phase characterized by small-celled species,mainly Phaeocystis pouchetii. Phytoplankton, bacterial and protozooanbiomass and production rates were measured in addition to copepodbiomass. Copepod grazing was estimated by three different methods:(i) gut fluorescence; (ii) chlorophyll clearance from the water;and (iii) growth method measured as body carbon increase. Thetwo latter methods gave similar results for nauplii, but allthree gave different results for the copepodites. Independentsomatic growth, based on changes in abundance and individualcarbon content, and grazing estimates revealed an overall growthefficiency of 0.66 ± 0.20 (mean ± S.E.) for copepodites.Empirical carbon flow models were constructed, which indicatedthat the nauplii could not control either phytoplankton or protozoangrowth in either the control or in the enriched system. Ignoringrecycling and sedimentation, the fate of the primary productionfor the nauplii-dominated community was to be grazed by a diverseand abundant protozooplankton community. In the copepodite-dominatedcommunity, the copepods grazed >100% of the daily primaryproduction, and also grazed heavily on a protozooplankton communityof low biomass and diversity and presumably on detritus. Thefate of the primary production in the two different copepodscenarios followed predicted routes for ‘low meso-zooplankton’and for ‘high meso-zooplankton’ biomass systems,as suggested by Wassmann (Wassmann, 1998).     

Ecological studies on the phytoplankton of Korsfjorden, western Norway. The dynamics of a spring bloom seen in relation to hydrographical conditions and light regime

The investigation was carried out at one station in Korsfjorden,a typical deep silled fjord of western Norway. During 14 cruisesfrom 4 February to 30 June 1977 ATP, chlorophll a, phaeopigmenta, and in situ ¹⁴C-assimilation were measured in the net (>30µm), nano and ultraplankton (<5 µm). Sampleswere collected from five light depths within euphotic zone.The impact of hydrographical conditions and light regime onthe bloom dynamics was also studied. In the periods 4 February-7 March and 13 April-30 June, ultraplankton contributed >60%to the total primary production while net and nanoplankton dominatedfrom 7 March to 13 April. The diatoms Skeletonema costatum,Chaetoceros compressits and C. debilis, and Rhizosolenia hebetatavar. semispina made up the main part of the biomass on 21 March,28 March and 4 April respectively. A shade adapted diatom societywas located at the top of the nutricline in late June with S.costatum, Chaetoceros spp., and Thalassiosira spp. as the dominantspecies. The highest assimilation number of eight for the netplankton and four for the ultraplankton were found at the depthof 32% light intensity on 28 March and 24 May respectively.Linear relationships were found between chlorophyll a and ATPfor the different size fractions with regression slopes rangingfrom 4.3 to 5.8. The total primary production for the periodof investigation was calculated to 74 g C m^–2. Light regimeand water column stability were decisive factors for the outburstof the first diatom bloom in late March. Grazing on net planktondiatoms increased during late March-early April. Changes inthe longshore wind-stress component were found to be essentialfor the understanding of the bloom dynamics.