Seasonal Changes In Biomass Research Articles

Seasonal succession of phototrophic biofilms in an Italian wastewater treatment plant: biovolume, spatial structure and exopolysaccharides

A multiphasic approach was applied to investigate the structural features of phototrophic biofilms that grow in a wastewater treatment plant (WWTP) at Fiumicino Airport (Rome, Italy). Seasonal variations in species composition, biomass and exopolysaccharides produced were analyzed by light (LM) and electron microscopy (SEM), high performance liquid chromatography (HPLC) and circular dichroism (CD). Phototroph contribution to the 3-dimensional structure of the biofilm and its development was assessed by confocal laser scanning microscopy. Analysis of biofilms grown on polypropylene slides showed a stable species composition; seasonal changes in biomass were mostly due to changes of major cyanobacterial and algal taxonomic groups. Extensive growth was evident on the range of artificial substrata that were implanted in the treatment plant. CD spectra and HPLC analyses of 2 operationally defined exopolysaccharide fractions extracted from samples scraped off the tank walls revealed that negatively charged heteropolysaccharides comprised most of the matrix and capsular components of the biofilms. Cytochemical staining distinguished between acidic and sulphated residues in the samples observed by LM. The data provide a new insight into the structural integrity and development of phototrophic biofilms in this hyper-eutrophic environment, indicating a potential use of autochthonous consortia in an environmentally sound tertiary water treatment alternative to conventional chemico-physical technologies.

Nutrient Uptake and Distribution in a Mature `Pinot noir' Vineyard

The nutrient uptake and distribution patterns for N, P, K, Ca, and Mg were determined in mature (23 to 24 year old), field-grown, rainfed grapevines (Vitis vinifera L. `Pinot noir') growing in a red hill soil in Oregon in 2001 and 2002. Biomass, nutrient concentrations, and nutrient contents of all plant organs, including roots, were determined on 14 sampling dates over 2 years. There was no seasonal change in the standing biomass of primary roots (fine feeder roots), small woody (<4 mm diameter) or large woody (>4 mm diameter) roots. Trunk biomass also did not change during the 2 years, but all other vine organs showed significant seasonal changes in biomass. The rate of N uptake was greatest at bloom, when remobilization from reserves was also high. Nitrogen was also taken up after leaf fall in 2001, but not in 2002, when an early frost occurred before soil moisture recovery by fall rains. Uptake of N, K, and Ca from soil was similar between years, even though canopy demand for N and K was greater in 2002 (significantly larger crop). Phosphorus uptake from soil was lower in 2002 than in 2001, which was most likely due to the drier conditions in 2002. A greater quantity of canopy N, K, and especially P was supplied from stored reserves in the drier 2002 growing season. About 50% of canopy requirements for N and P were remobilized from reserves in the trunk and roots by the time of fruit maturity in 2002. Only 15% of canopy K and <5% of canopy Ca or Mg came from stored reserves in 2002. Our findings indicate that nonirrigated grapevines grown in Oregon acquire nutrients from soil earlier in the growing season and have a greater reliance on stored reserves of N and P than reported in previous studies from other growing regions. Replenishment of nutrient reserves occurred to large extent during the postharvest period. Rainfed vineyards in Oregon may require different nutrient management practices than irrigated vineyards, since low soil moisture may limit summer uptake of P.

Life cycle of Dilophus okamurae (Phaeophyceae) and its associated invertebrate fauna in Onagawa Bay, Japan

The life cycle of Dilophus okamurae and the associated benthic invertebrate fauna were studied monthly or bimonthly from June 1998 to September 1999 at a depth of 4–7 m in Onagawa Bay along the Pacific coast of north-eastern Honshu, Japan (38o 28′N, 149o29′E). Dry biomass ranged from 230 g/m2 in June to 10g/m2 in October. Sporophytes with tetrasporangia appeared during July to September 1998. Gametophytes with oogonia or antheridia were observed for the first time in May 1999 during observation. The absence of mature sporophytes in 1999 suggests that the life cycle is completed over two years. The sympatric gastropods Lirularia iridescens, Homalopoma sangrarense, Conotalopia minima and Cantharidus callichroa synchronized with seasonal changes in biomass of this algae. In contrast, Barleeia angustata and B. trifasciata fluctuated independently. The juvenile sea urchin Strongylocentrotus nudus appeared in the algal population starting in October at 0.7 mm mean test diameter at high density, and disappeared after March.

郊外に移転した大学キャンパスにおける生物群集(17)ヤママユガ科ガ類の生態：特にバイオマスの季節的変化と被食

郊外に移転した大学キャンパスにおける生物群集(17)ヤママユガ科ガ類の生態：特にバイオマスの季節的変化と被食

Zooplankton variability and climatic anomalies from 1994 to 2001 in the Balearic Sea (Western Mediterranean)

Abstract The long-term and seasonal changes in biomass and zooplankton abundance at a station off Mallorca Island (Balearic Sea) were studied in relation to the main physical and chemical conditions. The results are based on a total of 276 samples collected every 10 days during 8 years by means of oblique hauls from bottom to surface. At this neritic station (77-m depth) located in a hydrographic area between northern Mediterranean and Atlantic southern waters, salinity ranged from 37 to 38.4 psu and temperature from 13.4°C (February 1996) to 27.4°C (August 1998). With the exception of salinity, the other environmental parameters and the most abundant zooplankton groups showed irregular but seasonal cycles. Interannual variability was also observed, with higher zooplankton abundance during the cooler and more saline years when the influence of northern water was stronger. Zooplankton abundance decreased during a warm period in 1998. Copepods were the most abundant group (54%) and their abundance was significantly correlated with temperature (negatively) and salinity (positively). Here, we summarize the changes in the zooplankton community abundance and how hydrographic forcing and other climatic factors have changed during the period from 1994 to 2001 in the Balearic Sea (Western Mediterranean).

Seasonal changes in biomass, growth rates and production of subantarctic calanoid copepods in the Bay of Morbihan, Kerguelen Islands

The present study addresses the ecology of two dominant copepod species in the Bay of Morbihan, Kerguelen Archipelago. The biomass of the herbivore Drepanopus pectinatus (from 2 mg m )3 in winter up to 500 mg m )3 in summer) is tightly coupled to seasonal changes in chlorophyll a concentration in the region, whereas the biomass of the predatory euchaetiid Para- euchaeta antarctica increases during two distinct periods over the year: 250 mg m )3 in early summer, with the recruitment of the annual generation, and 100 mg m )3 in autumn, with the deposition of lipids as energy reserves in C5 stages and adults. The juvenile growth rates pre- dicted by temperature-dependent models (0.09 day )1 ) closely approximate those observed in D. pectinatusin summer, but are much greater than those observed in P. antarctica (from 0.001 to 0.04 day )1 depending on developmental stages). This difference can be explained by the reproductive strategies and trophic positions of the two species and may also result from the dependence of larval growth on energy reserves in P. antarctica. The production rates are five- and tenfold greater in juvenile stages than in adults, respectively, for D. pectinatus and P. antarctica. The secondary production by D. pectina- tusis insufficient to support P. antarctica during winter, when the predatory species probably shifts to alternate prey. In summer the predation by P. antarctica accounts for only a minor part of the mortality estimated for D. pectinatus (from 20% to 60% depending on the examined station). At two of the three stations examined in the Bay of Morbihan, the production of P. antarctica could potentially support the dietary requirements of planktivorous seabirds in the region (� 2,000 kg prey day )1 for common diving petrels, Pelecanoides urinatrix, and � 90 kg prey day )1 for rockhopper penguins, Eudyptes chysocome filholi).

Distribution, annual cycle, and vertical migration of acoustically derived biomass in the Arabian Sea during 1994–1995

The distinguishing characteristic that sets the Arabian Sea apart from other oceanic regions is the regular oscillation of monsoonal atmospheric conditions that produces predictable periods of upwelling or convective mixing, with associated biological response, during the Southwest and Northeast monsoons, respectively. This oscillation is also evident in cycles of standing stocks of zooplankton and micronekton. The vertical distribution and spatial pattern of zooplankton and micronekton biomass were estimated using an acoustic Doppler current profiler along a 1000-km transect extending from the continental shelf of Oman to the central Arabian Sea during ten cruises on the R/V Thomas G. Thompson (November 1994–December 1995). The influence of the Southwest Monsoon, and accompanying upwelling and enhanced acoustically derived biomass, was the dominant feature in the spatial-temporal distributions of both zooplankton and micronekton near the Omani coast. The diel vertical migration of predators (myctophids, pelagic crabs), and the seasonal changes in the strength of this signal, was the most significant pattern observed in the vertical distribution of biomass and imparted a strong day–night signal to the integrated upper water-column biomass. Significant differences in the magnitude of integrated upper water-column biomass, both zooplankton (day) and migrator-zooplankton (night), were seen between inshore and offshore of the atmospheric Findlater Jet. A station located in the central Arabian Sea demonstrated seasonal changes in biomass over the year, despite being quite far from the influence of the monsoonal oscillations. Predation pressure was greater offshore of the Findlater Jet than in the region inshore of the Jet or in the central Arabian Sea. The pelagic community of the Arabian Sea may have evolved life history strategies to coincide with the predictable monsoonal cycle. r 2002 Elsevier Science Ltd. All rights reserved.

Seasonal changes in biomass of charophytes in shallow lakes in the northwest of Spain

Seasonal changes in aboveground biomass of submerged macrophytes were recorded in three shallow lakes in northwest Spain from May 1996 to June 1997. The biomass of a monospecific community ( Chara globularis) and of several communities with high charophyte coverage ( C. globularis–Myriophyllum alterniflorum, C. globularis–Potamogeton gramineus and Nitella translucens–Potamogeton natans) were studied monthly. The weather and hydrological regime had a strong influence on the seasonal biomass patterns and on between-the-year differences in the biomass of macrophytes. The biomass in the monospecific C. globularis community showed a bimodal pattern, with maximum in mid-July (128 g DW m −2) and late autumn (165 g DW m −2). Chara overwintered as a green plant and during the subsequent growth period, characterised by high temperature and low rainfall, reached a maximum of 305 g DW m −2 (June 1997). The highest biomass of C. globularis in the Chara–Myriophyllum community was reached in July (Sentiz: 160 g m −2, Redos: 204 g m −2), while the minimum (Sentiz: 10 g m −2; Redos: 3 g m −2) was recorded in February or March. M. alterniflorum (average biomass: 95 g m −2) was a better competitor than C. globularis in Redos lake and appeared to be favoured by the early beginning of the growing season in 1997 and by the later increase in the water level. The biomass of N. translucens (average biomass: 64 g m −2) showed a high stability during the study period, but lacked a well-defined seasonal biomass pattern. P. natans had a marked maximum biomass in August (426 g m −2). Although the stability of the Potamogeton population was low, shading did not have a significant influence on the development of Nitella biomass.

Biomass, growth, and secondary production of Arcitalitrus dorrieni (Crustacea: Amphipoda: Talitridae) at two sites in Co. Galway, IrelandS

Growth rates, podomere addition, and secondary production of Arcilalitrus dorrieni (Hunt, 1925) populations inhabiting two neighbouring woodland sites at Kylemore, Co. Galway, Ireland, were investigated. One site was a mixed deciduous woodland infested with Rhododendron ponticum. The other a pure coniferous stand of Pinus contorta var. latifolia S. Wats. Seasonal changes in biomass were recorded at the two sites. In both years of the study, maximum biomass was recorded in September. Females had a higher growth rate than males, but growth rates of both males and females were higher at the mixed deciduous site. The number of podomeres on the second antenna was correlated with the size of the animal. The average length of A. dorrieni at each podomere number appeared to change seasonally. Comparisons of mean spring values with mean summer values showed a statistically significant decrease in mean amphipod length for a given podomere number, though this was more marked at the mixed deciduous site. Annual secondary production rates ranged from 5.06 g dry wt m‐2 year‐1at the coniferous site to 14.55 g dry wt m‐2 year‐1 at the mixed deciduous site. P:B values ranged from 2.41 at the coniferous site to 3.01 at the mixed deciduous site. Results are compared between sites and with data from other relevant crustacean species.

Temperature and Copepod Production in the Sea: A Reply

Previous articleNext article No AccessNotes and CommentsTemperature and Copepod Production in the Sea: A ReplyMark HuntleyMark Huntley Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 148, Number 2Aug., 1996 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/285933 Views: 3Total views on this site Citations: 8Citations are reported from Crossref Copyright 1996 The University of ChicagoPDF download Crossref reports the following articles citing this article:Robert O. Megard, Elise Ralph, Michelle Marko Effects of wind and temperature on Lake Superior copepods, SIL Proceedings, 1922-2010 30, no.55 (Dec 2017): 801–808.https://doi.org/10.1080/03680770.2009.11902242Xabier Irigoien, Roger P. Harris Comparative population structure, abundance and vertical distribution of six copepod species in the North Atlantic: Evidence for intraguild predation?, Marine Biology Research 2, no.44 (Aug 2006): 276–290.https://doi.org/10.1080/17451000600865321Catherine Rey-Rassat, Delphine Bonnet, Xabier Irigoien, Roger Harris, Robert Head, François Carlotti Secondary production of Calanus helgolandicus in the Western English Channel, Journal of Experimental Marine Biology and Ecology 313, no.11 (Dec 2004): 29–46.https://doi.org/10.1016/j.jembe.2004.07.015Meng Zhou, Yiwu Zhu, Jay O. Peterson In situ growth and mortality of mesozooplankton during the austral fall and winter in Marguerite Bay and its vicinity, Deep Sea Research Part II: Topical Studies in Oceanography 51, no.17-1917-19 (Aug 2004): 2099–2118.https://doi.org/10.1016/j.dsr2.2004.07.008S. McClatchie, G. J. Macaulay, R. F. Coombs Acoustic backscatter and copepod secondary production across the Subtropical Front to the east of New Zealand, Journal of Geophysical Research: Oceans 109, no.C3C3 (Mar 2004).https://doi.org/10.1029/2000JC000751Michael Krause, Heino Fock, Wulf Greve, Gesche Winkler North sea zooplankton: a review, Senckenbergiana maritima 33, no.1-21-2 (Dec 2003): 71–204.https://doi.org/10.1007/BF03043048F. Alonzo, P. Mayzaud, S. Razouls, P. Bocher, Y. Cherel Seasonal changes in biomass, growth rates and production of subantarctic calanoid copepods in the Bay of Morbihan, Kerguelen Islands, Marine Biology 142, no.33 (Dec 2002): 525–536.https://doi.org/10.1007/s00227-002-0976-5J.A. Runge, J.C. Roff The measurement of growth and reproductive rates, (Jan 2000): 401–454.https://doi.org/10.1016/B978-012327645-2/50010-4

Seasonal variation in biomass and primary productivity of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open area in northern India

Seasonal changes in biomass, net primary productivity and turnover of dry matter of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open stand in northern India are presented. Both stands attained peak values of live shoot biomass in September with a higher value under mixed tree stand (665 g m−2) than in the open stand (522 g m−2). The net aboveground production was 590 and 527 g m−2 yr−1 under mixed tree stand and in the open, respectively. The belowground net primary production was also greater under mixed tree stand (100 g m−2 yr−1) than in the open (76 g m−2 yr−1). Maximum aboveground and belowground net primary productions in both stands were obtained during the rainy season. The total net primary production for para grass was about 15% higher under mixed tree stand than in the open. The turnover rates of total plant biomass were greatest in the rainy season and the least during the summer season. The system transfer functions showed that the production of para grass on both stands was aboveground-oriented, accounting for 85–87% of annual total net primary production.

Efficient nitrogen economy: Key to the success ofPolygonum bistorta in an abandoned mountain meadow

The dominance ofPolygonum bistorta in abandoned mountain meadows was studied. Successional and seasonal changes in biomass, nitrogen concentration and content were studied at the community level. During the successionP. bistorta increases its biomass both in absolute and mainly in relative values compared to the surrounding species. Nitrogen stored in its rhizomes seems to be quickly translocated into above-ground parts at the beginning of the growing season. High amounts of nitrogen allow rapid growth of both vegetative and generative plant parts. The success ofP. bistorta is probably the result of efficient use of stored nitrogen, suppression of surrounding vegetation by above-ground cover of leaves and by decrease in the level of soil nitrogen, and the effect of a large amount of litter. Management consisting in the combination of mowing and fertilization is proposed.

Seagrass distribution and seasonal biomass changes in relation to dugong grazing in the Moluccas, East Indonesia

Seagrass distribution and seasonal changes in biomass and total organic C were studied in relation to dugong grazing, in intertidal meadows dominated by Halodule uninervis (Forsskål) Ascherson between December 1990 and December 1992 in Nang Bay on the east coast of Ambon. Both below-ground and above-ground biomass of Halodule uninervis significantly increased during the transition period from the dry season to the wet season between February and May. Above-ground biomass of Halodule uninervis decreased significantly during the wet season (between May and August), when low tide occurred in day time, and only slow recovery took place until November. Below-ground biomass remained high until November, resulting in a significant decrease of the ratio of above-ground to below-ground biomass during the period between May and August, and in a ‘sparse’ visible seagrass meadow, with a non-visible high below-ground biomass between August and November. Total organic carbon level in the below-ground plant parts gradually increased between May and August with a peak value in August. Dugong grazing removed 93% of the shoots and 75% of the below-ground biomass of the upper 4 cm deep layer of sediment. Seagrass biomass in freshly grazed feeding tracks was restored to levels of the nearby seagrass bed after 5 months during the onset of the wet season. No significant restoration took place during the dry season. The frequency of dugong grazing showed a strong positive correlation with total organic C level in the below-ground plant parts, indicating that the dugongs preference for the Halodule uninervis seems to be based on a strategy of a high net rate of energy intake.

Seasonal changes in biomass and shoot characteristics of a Zostera capricorni Aschers. Dominant meadow in Cairns Harbour, northern Queensland

Spatial and temporal variability of Z. capricorni biomass, shoot characteristics (canopy height, surface area, flowering), distribution and detrital content were examined from December 1988 to December 1990. Between August 1987 and August 1991, 15% (2.0 ha) of the meadow was lost. Biomass of above- and below-ground structures showed a unimodal seasonal pattern with maxima in late spring (mean 194.92 g dry weight m-2 and 426.67 g DW m-2 respectively) and minima in winter (mean 28.72 g DW m-2 and 56.98 g DW m-2 respectively). Mean above-ground biomass (95.53 � 2.21 g DW m-2) was approximately half the mean below-ground biomass (177.28 � 4.49 g DW m-2). Leaf canopy heights were greatest between October and February (maximum 53.4 cm) and lowest around mid year (minimum 4.4 cm). Leaf surface area per square metre of seagrass meadow ranged from 10.28 to 1.39 m2 (mean 3,692 � 0.104 m2), and flowering occurred during September and October. Detrital biomass ranged from 339.73g DW m-2 to 11.83 g DW m-2 (mean 77.39 � 2.36 g DW m-2). Detrital biomass was higher during July-October and lower during February-May. The climate during the study was typical for the area, and all trials displayed similar seasonal patterns, although the amplitudes differed among some trials. The environmental parameters that may influence seagrass and detrital biomass were investigated. The best models explained only 14% of the variation in above-ground biomass, 15% of the variation in below-ground biomass, and 21% of the variation in detrital biomass. These models suggest that fluctuations in seagrass and detrital biomass in Cairns Harbour were influenced by changes in light availability, temperature, salinity and exposure.

Diurnal Photosynthesis Cycle in Cam and Non‐Cam Seasonal‐Pool Aquatic Macrophytes

Seasonal pools undergo marked diurnal changes in pH, free carbon dioxide, and oxygen levels. Previous studies showed that Isoetes howellii utilized crassulacean acid metabolism (CAM) photosynthesis as a means of assimilating carbon at night when ambient carbon dioxide levels are high. However, much of the pool flora is not CAM. We hypothesized that coexistence under extreme carbon—limiting conditions would select for other photosynthetic characteristics in these non—CAM species. Quantitative carbon uptake measurements wee made in the field on the CAM Isoetes howellii and the non—CAM Eleocharis acicularis, Downingia bella, and Plagiobothrys undulatus. Despite wide phylogenetic separation, thee species are structurally convergent in that they all produce aquatic stage with an isoetid growth form. They are functionally similar in that none appear to utilize bicarbonate, and all are carbon limited through much of the day, as indicated by a marked midday depression in carbon uptake that last through the afternoon. All four species were capable of carbon fixation at night, although only in Isoetes howellii was this accompanied by an overnight accumulation of acid. It was estimated that dark fixation in I. howelli contributed up to 40% of its total carbon gain under submerged conditions, but was <1% under aerial conditions. The role of dark fixation in the other three, non—CAM, species is unknown. Short—term (1 s) steady—term (1 s) steady—state 14C tracer studies in the laboratory revealed that, under submerged conditions in the light, all species assimilated carbon into the C3 photosynthetic product phosphoglycerate (PGA) and the C4 photosynthetic products of malate, citrate, and aspartate. The proportion of label fixed into C4 organic acids was greatest in E. acicularis. The ratio of RuBP carboxylase/PEP carboxylase was broadly similar in all species, ranging from 8.8 to 11.5. When the pools dried down and the plants became aerial, photosynthetic rates increased and a midday depression such as occurred under submergence was not observed. Carbon fixation in the dark became negligible, and the RuBP carboxylase/PEP carboxylase ratio increased. Seasonal changes in biomass showed I. howellii and E. acicularis dominated the pools early in the season, and the biomass of the other two species increased later when the pools dried. The latter species, D. bella and P. undulatus, also had higher rates of photosynthesis under aerial conditions.

Growth and reproduction ofPorphyra columbina Mont. (Bangiales, Rhodophyceae) from southern New Zealand

Changes in biomass and chemical composition, and the reproductive phenology ofPorphyra columbina Mont. were monitored at three sites in southern New Zealand over two growing seasons. Both temporal and spatial variations were found. Seasonal changes in biomass and chemical components were correlated with seawater nitrate concentrations and temperature. The summer decline in biomass was a result of the onset of unsuitable environmental conditions and the release of reproductive tissue. Under more suitable conditions, the decline in biomass was delayed. There was an inverse relationship between vegetative growth and reproduction. Reproductive plants first appeared in August at a time of increasing temperature, irradiance and daylength. Only larger plants which were mainly found in subsites low on the shore became reproductive. Plants sampled from high subsites had a shorter growth season, were generally smaller, had lower nitrogen and pigment content and were non-reproductive.

Planktonic Protozoa in Lakes Huron and Michigan: Seasonal Abundance and Composition of Ciliates and Dinoflagellates

The abundance and biomass of surface (5 m) and deep (30–45 m) ciliate and dinoflagellate protozoa in the offshore waters of Lakes Huron and Michigan were determined from December 1986 to November 1987. Protozoan (ciliates and dinoflagellates) abundance (4 to 15 cells·mL −1) and biomass (13–140 μg·L −1, wet wt.) were comparable between lakes and similar to those reported from other oligotrophic environments. On average, ciliates comprised the majority of protozoan abundance (80%) and biomass (73%). The mean size (ESD) of these communities was small (20.6 μm) due to the numerical dominance of small choreotrichs, oligotrichs, and species of Gymnodinium. Total biomass in both lakes peaked during late June-July and again during the October-November period. These seasonal changes in biomass were accompanied by species replacements: tintinnids, strobilids, oligotrichs, and Gymnodinium species were abundant in the spring isothermal period, shifting to oligotrich dominance during summer stratification (May–July); a more diverse assemblage followed during late stratification (October–November) in which haptorids, prorodontids, and Peridinium species became more important. Deep and surface communities were comparable in terms of abundance and biomass, although deep community biomass decreased as stratification intensified. Because the biomass of ciliates alone represents approximately 30% of crustacean zooplankton biomass, protozoa may be more important grazers than once thought.

Seasonal changes in biomass and production of periphyton growing upon reed in Lake Maarsseveen I

Seasonal changes in biomass and production of periphyton growing upon reed in Lake Maarsseveen I

Phytoplankton dynamics in the central Great Barrier Reef—I. Seasonal changes in biomass and community structure and their relation to intrusive activity

Phytoplankton dynamics in the central Great Barrier Reef and the relation of these dynamics to the seasonal upwelling of nutrient-enriched Coral Sea water onto the outer continental shelf were followed over an annual cycle. Event scale changes were sampled by frequent (2-day to 2-week) re-occupations of a cross-shelf transect during the latter half of the summer. Intrusive activity between November and April episodically injects nitrate-N enriched water into oligotrophic shelf waters. Persistent mid-shelf and intermittent outer shelf mid-water phytoplankton accumulations were observed from late-January to March. The 10, 10to2and<2μm phytoplankton size fractions were, respectively, dominated by diatoms, microflagellates + unarmored dinoflagellates and unicellular cyanobacteria + coccoid eukaryotes + very small flagellates. In the absence of intrusive activity, nanoplankton (10 to 2 μm) and picoplankton (<2μm) dominated biomass. These two size fractions dominated biomass on the outer shelf and in the Coral Sea throughout the year. Picoplankton frequently made up50% of the chlorophyll standing crop. Mid-shelf blooms, in which the highest chlorophyll levels (2μg 1 −1) were found, were largely due to increases of the 10μm fraction. In contrast to marked summer fluctuations of mid-shelf diatom populations, nano- and picoplankton standing crop varied little with time, cross-shelf location or depth. Low water column DIN levels and DIN:Chla ratios suggest phytoplankton populations were nitrogen-limited. In open waters of the central GBR, phytoplankton apparently convert most of the intruded nitrogen into particulate form.

Seasonal studies on the phytoplankton and primary production in the inner Firth of Clyde

SynopsisAnalysis of the factors influencing the seasonal changes in biomass of the ‘net’ phytoplankton in 1972– 73 snowed that the dynamics of the spring waxing of the diatom populations were controlled by narrow ‘windows’ of climatic events, and that subsequent fluctuations in cell numbers were linked with the interplay between zooplankton grazing and wind induced dispersion. Data for 1976–77, set against a similar background of events with the ‘net’ plankton, showed that the nanophytoplankton constituted a less variable biomass through the seasons and, on an annual basis, contributed some 50% of the total carbon fixed.