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1.
Micronekton and macrozooplankton were collected during the austral spring of 1993 in the NW Weddell Sea. Sampling was done
in three areas of the marginal ice zone: pack ice, ice edge, and open water, to examine the short-term effects of the spring
phytoplankton bloom on the distribution and abundance of dominant fish and invertebrate species. Significant differences were
observed for several common species, including Salpa thompsoni,Euphausia superba, Electrona antarctica, Gymnoscopelus braueri,and G. opisthopterus. Increased abundance seaward of the pack ice for these species is attributed to elevated phytoplankton and zooplankton biomass
at the ice edge and in the open water areas. Distribution of the hyperiid amphipods, Cyllopus lucasii and Vibilia stebbingi mirrored that of S. thompsoni. No distributional trends between the areas were observed for Thysanoessa macrura, the amphipods Cyphocaris richardi and Primno macropa, the decapod shrimp Pasiphaea scotiae, the scyphomedusae Atolla wyvilli and Periphylla periphylla, and chaetognaths, indicating a trophic independence from the ice-edge bloom for these species. Lower occurrence of the mesopelagic
fish Bathylagus antarcticus and Cyclothone microdon under the ice suggested that trophic repercussions of the spring bloom can also extend to deeper living species. 相似文献
2.
Scott E. Burghart Thomas L. Hopkins Gabriel A. Vargo José J. Torres 《Polar Biology》1999,22(4):279-288
Open-water, marginal-ice and in-ice zones were sampled in the Weddell Sea during November and December, 1993 in an effort
to examine the influence of the early spring bloom on the diet and population structure of the three biomass dominant copepods:
Metridia gerlachei, Calanus propinquus, and Calanoides acutus. The abundance of all three species in the upper 200 m was highest at stations in the open water, but individually, each
species displayed a unique trend. M. gerlachei, which showed the least variability, was significantly more abundant in open water than in the marginal-ice zone. The abundance
of Calanus propinquus was higher in open water than in the marginal-ice zone or in the ice. Calanoides acutus displayed the highest variability, with significant differences between all three ice-cover zones. Diet analysis revealed
no significant differences in the number of food items within each ice-cover zone and diatoms were the most numerous item
identified in the guts of all three species. However, M. gerlachei and Calanus propinquus also contained metazoan material, while Calanoides acutus did not. There were dramatic differences in the age composition of the species between the zones. Early copepodite stages
of all three species predominated at the ice edge and in open water. Numbers of M. gerlachei adult females were roughly equivalent in all three zones while Calanoides acutus and Calanus propinquus adult females composed a higher fraction of the total population within the ice. These results compare well with life-history
data compiled by other authors and reinforce the importance of the ice edge to bloom-dependent Antarctic zooplankton.
Accepted: 5 April 1999 相似文献
3.
Climate-induced variability in Calanus marshallae populations 总被引:1,自引:0,他引:1
Calanus marshallae is the dominant mesozooplankton copepod speciesover the south-eastern Bering Sea middle shelf. Climate-inducedchanges in the magnitude and timing of production by C. marshallaemay affect the living marine resources of the Bering Sea shelfecosystem. We examined springtime abundance, gonadal maturityand stage distributions of C. marshallae copepodites duringfive consecutive years (19951999) that spanned the rangeof variability observed over the past 34 years in terms of watertemperature and ice cover. We compared our results with previouswork conducted during cool (1980) and warm (1981) years [
Smith,S. L. and Vidal, J. (1986) Cont. Shelf Res., 5, 215239].The spring phytoplankton bloom began relatively early in associationwith ice (1995, 1997, 1999), but began late when ice was absentor retreated early (1996, 1998). Egg production began well beforethe bloom and continued over a long duration. Copepodites, however,were recruited during a relatively short period, coincidentwith the spring phytoplankton bloom. The relationship betweenbrood stock and spring-generation copepodite abundances wasweak. Copepodite concentrations during May were greatest inyears of most southerly ice extent. Copepodite populations werehighly variable among years, reflecting interannual variabilityin the atmosphereiceocean system. 相似文献
4.
Anette Wold G��rald Darnis Janne E. S?reide Eva Leu Benoit Philippe Louis Fortier Michel Poulin Gerhard Kattner Martin Graeve Stig Falk-Petersen 《Polar Biology》2011,34(12):1929-1946
The copepod Calanus glacialis plays a key role in the lipid-based energy flux in Arctic shelf seas. By utilizing both ice algae and phytoplankton, this
species is able to extend its growth season considerably in these seasonally ice-covered seas. This study investigated the
impacts of the variability in timing and extent of the ice algal bloom on the reproduction and population success of C. glacialis. The vertical distribution, reproduction, amount of storage lipids, stable isotopes, fatty acid and fatty alcohol composition
of C. glacialis were assessed during the Circumpolar Flaw Lead System Study. Data were collected in the Amundsen Gulf, south-eastern Beaufort
Sea, from January to July 2008 with the core-sampling from March to April. The reduction in sea ice thickness and coverage
observed in the Amundsen Gulf in 2007 and 2008 affected the life strategy and reproduction of C. glacialis. Developmental stages CIII and CIV dominated the overwintering population, which resulted in the presence of very few CV
and females during spring 2008. Spawning began at the peak of the ice algal bloom that preceded the precocious May ice break-up.
Although the main recruitment may have occurred later in the season, low abundance of females combined with a potential mismatch
between egg production/development to the first feeding stage and phytoplankton bloom resulted in low recruitment of C. glacialis in the early summer of 2008. 相似文献
5.
Letterio Guglielmo Giacomo Zagami Vincenzo Saggiomo Giulio Catalano Antonia Granata 《Polar Biology》2007,30(6):747-758
The aim of this study was to investigate patterns of abundance, distribution, temporal changes and species composition of
the dominant ice-associated copepods in the spring annual pack ice, platelet ice and water column at Terra Nova Bay, Ross
Sea, during late spring 1997. Ice cores were drilled for temporal and spatial scales. Stephos longipes and Harpacticus furcifer dominated the sea ice meiofauna in terms of numbers in the lower few centimeters of the bottom ice associated with high chlorophyll
a and phaeopigment levels. Nauplii dominated the S. longipes population (91.6%) and occurred in extremely high concentrations. In contrast, copepodids were the dominant stages in H. furcifer. How H. furcifer carries out its entire life cycle and how it differs from ecologically similar species such as Drescheriella glacialis should be examined in more detail. 相似文献
6.
We compared six biochemical measures of nutritional condition: citrate synthase activity (CS), malate and lactate dehydrogenase activity (MDH and LDH), RNA:DNA ratio, and percent body protein and lipid. Adult females of five species of calanoid copepod (Calanoides acutus, Calanus propinquus, Metridia gerlachei, Rhincalanus gigas and Paraeuchaeta antarctica) were collected in the marginal ice zone of the northwestern Weddell Sea at the time of the annual phytoplankton bloom that occurs in association with the receding ice edge during austral spring. Three zones within the marginal ice zone were sampled: heavy-ice-cover pre-bloom, ice-edge bloom and low-ice-cover post-bloom. Lipid generally increased greatly from ice-covered to open water zones, and its importance in the life of polar copepods cannot be overstated. Increases in protein from ice-covered to open water were also observed, but were of less significance. Each species exhibited significant changes in at least one enzyme activity level. Citrate synthase activity in C. acutus, C. propinquus and R. gigas, all herbivores, increased between pre- and post-bloom stations. C. propinquus and M. gerlachei, which feed during winter, had large increases in LDH activity between pre- and post-bloom stations. Rhincalanus gigas and P. antarctica, the two largest species studied, showed variations in MDH activity, with peak enzyme activity occurring in post-bloom stations. RNA:DNA ratio did not change in any species. The effects of size, shipboard handling and freezer storage were easily corrected statistically, and did not alter any conclusions. The patterns observed in copepod nutrition at the Antarctic ice edge were consistent with existing models of life history for each species. The observations reported here, in conjunction with previously reported data, suggested that measurement of metabolic enzyme activity, especially in concert with lipid, enables estimation of nutritional condition in adult copepods. Additional studies comparing metabolic activity and ecology of common species should yield more information on the ecology of rarer species. 相似文献
7.
Stephen I. C. Hsiao 《Polar Biology》1987,7(4):245-251
Summary Sedimentation of phytoplankton provides food and energy for zoobenthic communities. In this study the rates, species composition and biomass of phytoplankton input to Frobisher Bay sediments were examined during ice (late November to July) and open water (late July to October) periods from 1982 to 1985. The rates were higher on the sea bed than at 20 m. The minimum rate (3x105 cells·m-2·day-1) of sedimentation occurred during the early part of the ice period. It increased as the ice thickened and reached a maximum of 2.8x108 cells·m-2·day-1 after the phytoplankton bloom at the beginning of the open water period in the first two weeks of August. The sedimented phytoplankton was dominated by diatoms, with a great majority of pennate species during the spring (April to June) and centric forms during the summer (July to August). Green flagellates, dinoflagellates and chrysophytes occurred as a low percentage of the total population in all seasons. Other indicators (chlorophyll a and phaeopigments) showed highest biomass levels in the deepest traps. They were consistently low during the winter (December to March) and reached their maxima during the open-water period of summer. Their abundance was correlated with the seasonal cycle of the phytoplankton in the water column. 相似文献
8.
This study documents, for the first time, the abundance and species composition of protist assemblages in Arctic sea ice during
the dark winter period. Lack of knowledge of sea-ice assemblages during the dark period has left questions about the retention
and survival of protist species that initiate the ice algal bloom. Sea-ice and surface water samples were collected between
December 27, 2007 and January 31, 2008 within the Cape Bathurst flaw lead, Canadian Beaufort Sea. Samples were analyzed for
protist identification and counts, chlorophyll (chl) a, and total particulate carbon and nitrogen concentrations. Sea-ice chl a concentrations (max. 0.27 μg l−1) and total protist abundances (max. 4 × 103 cells l−1) were very low, indicating minimal retention of protists in the ice during winter. The diversity of winter ice protists (134
taxa) was comparable to spring ice assemblages. Pennate diatoms dominated the winter protist assemblage numerically (averaging
77% of total protist abundances), with Nitzschia frigida being the most abundant species. Only 56 taxa were identified in surface waters, where dinoflagellates were the dominant
group. Our results indicate that differences in the timing of ice formation may have a greater impact on the abundance than
structure of protist assemblages present in winter sea ice and at the onset of the spring ice algal bloom. 相似文献
9.
Inter-annual variations in zooplankton community structure in Prydz Bay were investigated using multivariate analysis based
on samples collected with a 330-μm mesh, 0.5-m2 Norpac net during the austral summer from 1999 to 2006. Two distinct communities, an oceanic and a neritic community, were
consistently identified in all surveys. Oceanic communities had higher diversity and were indicated by species such as Haloptilus ocellatus, Heterorhabdus austrinus, Thysanoessa macrura, Rhincalanus gigas, Scolecithricella minor and Oikopleura sp.. Neritic communities were indicated by Euphausia crystallorophias and Stephos longipes and were characterized by fewer but more abundant species. In 1999 and 2006, a transitional community was also distinguished near the continental shelf edge, where ice coverage was
more extensive than either the oceanic or neritic regions. Significant inter-annual variations in community structure (mainly
involving species abundance rather than species composition) were found in both oceanic and neritic communities, being more
obvious in the latter. The timing and amplitude of sea ice retreat (polynya appearance), and its effect on food availability,
had strong influences on zooplankton community structure. In oceanic communities during years with earlier ice retreat, the
extra time available for phytoplankton blooms to accumulate resulted in a higher proportion of large copepods (Calanoides acutus, Calanus propinquus, Metridia gerlachei) (especially the younger copepodites) in the zooplankton assemblage. In neritic communities, zooplankton such as the ice
krill E. crystallorophias, and large copepods (C. acutus, C. propinquus, M. gerlachei), also showed higher abundance and earlier developmental stages in years with larger polynya. On the other hand, in years
with later ice retreat, smaller polynya, and less time for phytoplankton blooms to form, the abundance of large copepods was
lower and older age classes were more common. 相似文献
10.
Influence of sea ice on the composition of the spring phytoplankton bloom in the northern Baltic Sea 总被引:5,自引:2,他引:3
During the late winter and spring of 1994, the influence of sea ice on phytoplankton succession in the water was studied
at a coastal station in the northern Baltic Sea. Ice cores were taken together with water samples from the underlying water
and analysed for algal composition, chlorophyll a and nutrients. Sediment traps were placed under the ice and near the bottom, and the sedimented material was analysed for
algal composition. The highest concentration of ice algae (4.1 mmol C m−2) was found shortly before ice break-up in the middle of April, coincidental with the onset of an under-ice phytoplankton
bloom. The ice algae were dominated by the diatoms Chaetoceros wighamii Brightwell, Melosira arctica (Ehrenberg) Dickie and Nitzschia frigida Grunow. Under the ice the diatom Achnanthes taeniata Grunow and the dinoflagellate Peridiniella catenata (Levander) Balech were dominant. Calculations of sinking rates and residence times of the dominant ice algal species in the
photic water column indicated that only one ice algal species (Chaetoceros wighamii) had a seeding effect on the water column: this diatom dominated the spring phytoplankton bloom in the water together with
Achnanthes taeniata and Peridiniella catenata.
Received: 9 May 1997 / Accepted: 15 February 1998 相似文献
11.
Are copepods important grazers of the spring phytoplankton bloom in the western Irish Sea? 总被引:3,自引:0,他引:3
Gowen R; McCullough G; Kleppel G; Houchin L; Elliott P 《Journal of plankton research》1999,21(3):465-483
The spring phytoplankton bloom and copepod grazing were studied at a
coastal and offshore station in the western Irish Sea during 1997. Maximum
chlorophyll standing stocks of 132.8 mg m-2 inshore
and 199.4 mg m-2 offshore were measured in late
April. At that time, mean water column temperatures were 10 and 8C at the coastal and offshore station, respectively.
Spring bloom production at the coastal station was estimated as 31.2 g C
m-2 and was dominated by the diatom
Guinardia delicatula. Offshore, production was 28.2 g
C m-2 and the bloom was composed of small (10 m) phytoflagellates
and the silicoflagellate Dictyocha speculum. Maximum
copepod abundance (189 and 544 x 103 individuals
m-2, inshore and offshore, respectively) coincided
with the spring bloom. Pseudocalanus and
Temora ingestion rates were derived from measurements
of gut pigment fluorescence, and were found to vary during the course of
the spring bloom as a result of changes in gut content. Grazing by late
copepodite and adult Pseudocalanus and
Temora was variable inshore, but overall accounted for
17% of bloom production. Offshore, 22% of bloom production was grazed with
maximum grazing (76% of daily production) occurring at the end of the
bloom. Large copepod species were not major grazers of the spring bloom.
Greater utilization of spring bloom production by copepods in the western
Irish Sea compared to regions of the North Sea is attributed to differences
in population size at the time of the bloom.
相似文献
12.
Daria M. Martynova Natalia A. Kazus Ulrich V. Bathmann Martin Graeve Alexey A. Sukhotin 《Polar Biology》2011,34(8):1175-1195
We have studied the seasonal dynamics of abundance and feeding characteristics of three species of calanoid copepods (Acartia spp., Centropages hamatus and Temora longicornis) in the White Sea from the surface water layer (0–10 m), in order to assess their role in the pelagic food web and to determine
the major factors governing their population dynamics during the productive season. These species dominated in the upper water
layer (0–10 m) from June through September, producing up to 3 generations per year. Data on the food spectra revealed all
species to be omnivorous; but some inter- and intraspecific differences were observed. Generally, copepods consumed diatoms,
dinoflagellates and microzooplankton. The omnivory index ‘UC’ (i.e., fatty acid unsaturation coefficient) varied from 0.2
to 0.6, which implied ingestion of phytoplankton. The different degree of selectivity on the same food items by the studied
species was observed, and therefore, successful surviving strategy with minimal overlapping could be assumed. In total, the
populations of the three studied copepod species grazed up to 2.15 g C m−2 day−1 and released up to 0.68 g C m−2 day−1 in faecal pellets. They consumed up to 50% of particulate organic carbon, or up to 85% of phytoplankton standing stock (in
terms of Chl. a), and thus played a significant role in the transformation of particulate organic matter. Seasonal changes in abundance of
the studied species depended mostly on water temperature in the early summer, but were also affected by food availability
(Chl. a concentration) during the productive season. 相似文献
13.
Spatial distribution and life-cycle timing of zooplankton in the marginal ice zone of the Barents Sea during the summer melt season in 1995 总被引:7,自引:0,他引:7
Falk-Petersen S; Pedersen G; Kwasniewski S; Hegseth E; Hop H 《Journal of plankton research》1999,21(7):1249-1264
The marginal ice zone (MIZ) in the northern Barents Sea is ecologically
important because it represents a highly productive area in Arctic water
masses north of the Polar Front. During a multi-disciplinary cruise in
1995, ecological and oceanographic processes were investigated at four
stations located in a north-south transect in the MIZ. This study was
carried out in Arctic water masses north of the Polar Front where ice
conditions varied from dense first-year pack ice to open water. Also, the
phytoplankton development varied along the transect from a pre-bloom
situation at the northern-most station to a post-bloom situation in the
open water. This paper includes a study of the zooplankton community and
population structure of some of the dominant copepod species. Numerically,
the most important mesozooplankton components were the copepods
Calanus glacialis, Pseudocalanus minutus and
Oithona similis. Copepods of Atlantic origin, such as
Calanus finmarchicus and Oithona
atlantica, gave evidence of an advection of Atlantic water
masses into the area. It is concluded that the occurrence of new cohorts of
Arctic copepods coincides with the onset of the phytoplankton bloom in the
MIZ, and, that therefore, the spawning relies on stored energy.
相似文献
14.
Calanoid copepod grazing on phytoplankton: seasonal experiments on natural communities 总被引:3,自引:2,他引:1
Calanoid copepods are major components of most lacustrine ecosystems and their grazing activities may influence both phytoplankton biomass and species composition. To assess this we conducted four seasonal, in situ, grazing experiments in eutrophic Lake Rotomanuka, New Zealand. Ambient concentrations of late stage copepodites and adults of calanoid copepods (predominantly Calamoecia lucasi, but with small numbers of Boeckella delicata) were allowed to feed for nine days on natural phytoplankton assemblages suspended in the lake within 1160 litre polyethylene enclosures. The copepods reduced the total phytoplankton biomass of the dominant species in all experiments but were most effective in summer (the time of highest grazer biomass) followed by spring and autumn. In response to grazing pressure the density of individual algal species showed either no change or a decline. There were no taxa which increased in density in the presence of the copepods. The calanoid copepods suppressed the smallest phytoplankton species (especially those with GALD (Greatest Axial Linear Dimension) < µm) and there appeared to be no selection of algae on the basis of biovolume. Algal taxa which showed strong declines in abundance in the presence of the copepods include Cyclotella stelligera, Coelastrum spp., Trachelomonas spp., Cryptomonas spp., and Mallomonas akrokomos. Calanoid copepods are considered important grazers of phytoplankton biomass in this lake. The study supports the view that high phytoplankton:zooplankton biomass ratios and large average algal sizes characteristic of New Zealand lake plankton may, at least partly, be caused by year round grazing pressure on small algae shifting the competitive balance in favour of larger algal species. 相似文献
15.
Different approaches to the study of life cycle strategies of Antarctic copepods are described in an attempt to shed new light on our present knowledge. To date, most studies were carried out on abundance, horizontal and vertical distribution and stage composition during different seasons and in various regions. Hence, the seasonal pictures had to be compiled from different years and sampling regions. The physiological method includes measurements on e.g. egg production, feeding, respiration and excretion rates, C:N and O:N ratios, lipid and protein contents. However, both physiological and biochemical data are still rare. Results of field observations are given in this paper for investigations conducted within the last 15 years in the eastern Weddell Sea, while data of physiological parameters are based on a broader geographical region. In the eastern Weddell Sea, eight copepod species account for about 95% of copepod abundance and for more than 80% of copepod biomass. Within the calanoids, the small species Microcalanus pygmaeus dominates by numbers with 66%, while the large species Calanoides acutus and Calanus propinquus comprise together 52% of the biomass. Species abundance is lowest in winter and highest in summer/autumn, however, seasonal changes in the abundance of M. pygmaeus are small and this species occurs in similar quantities throughout the year. All copepod species show a distinct seasonal vertical distribution pattern and they occur in upper water layers in summer, in contrast to the other seasons. However, the depth layers of maximum concentration differ between species. The ontogenetic vertical migration is most pronounced in C. acutus and relatively weak in C. propinquus. The age structure also shows seasonal differences with the youngest population observed in summer for C. acutus, C. propinquus, Ctenocalanus citer or autumn for Metridia gerlachei, whereas the M. pygmaeus population is oldest during summer. The youngest copepodite stage and the males are not always present in C. acutus and C. propinquus. In contrast, all developmental stages and both sexes occur throughout the year in M. gerlachei, M. pygmaeus and C. citer. Gonad maturation in the dominant calanoid species proceeds well before the onset of phytoplankton production in the eastern Weddell Sea. However, the highest portion of females with ripe gonads and hence highest egg production rates coincide with the productive period in spring and summer. In autumn, ovaries of the three larger species C. acutus, C. propinquus and M. gerlacheiare all spent. In contrast, the percentage of ripe females of the two smaller species, C. citer and M. pygmaeus, stays high in autumn. Egg production rates are highly variable within one region and species. Many copepods accumulate large depots of lipid, mainly wax esters. In contrast, five species (C. propinquus, C. simillimus, Euchirella rostromagna, Stephos longipes and Paralabidocera antarctica) almost exclusively synthesise triacylglycerols and not wax esters. The lipid content exhibits distinct seasonal patterns, and is highest in autumn. A seasonal difference is also obvious in metabolic activities with lowest rates during the dark season. The adaptation to the pronounced seasonality in the Southern Ocean differs greatly between copepod species, and most Antarctic copepods stay active during the dark season. Calanoides acutus seems to be the only true diapause species. Calculations of summer developmental rates and winter mortality rates of the large species C. acutus and C. propinquus suggest that both species have a 1-year life cycle with few females overwintering and probably spawning a second time. In contrast, a 2-year life cycle is more likely in R. gigas. However, life cycle durations of all species studied are still uncertain and regional differences are very probable. 相似文献
16.
Plankton ecology in an ice-covered bay of Lake Michigan: utilization of a winter phytoplankton bloom by reproducing copepods 总被引:2,自引:2,他引:0
Vanderploeg Henry A. Bolsenga Stanley J. Fahnenstiel Gary L. Liebig James R. Gardner Wayne S. 《Hydrobiologia》1992,(1):175-183
Plankton ecology was examined during the 1986 winter in Grand Traverse Bay, a 190 m deep, fjordlike bay on Lake Michigan. Before ice cover, algal concentration was low and uniformly distributed with depth, as it is in open Lake Michigan. During ice cover (February and March), a bloom of a typical winter-spring phytoplankton community developed in the upper 40 m, resulting in a 4 to 7-fold increase in feeding rate of adult Diaptomus spp. High algal concentration and zooplankton feeding persisted after ice melt (April). During and after ice cover, lipid concentrations of Diaptomus dropped rapidly from 34% of dry weight to 17 % because of egg production. High incident photosynthetically active radiation (PAR), high (45–50%) PAR transmittance of the ice due to little snow on the ice, and water column stability were probably responsible for the bloom. High ice transparency may be a common feature of large lakes and bays, where strong winds blow snow cover off the ice, or at low latitudes where snowmelt due to occasional rains and warm temperature is common. Winter reproducing calanoid copepods use these blooms to increase their reproductive output. 相似文献
17.
The abundance and species composition of phytoplankton were investigated at stations in a permanently ice-free (61°S) and
seasonally ice-covered area (64°S and 66°30′S) in the eastern Indian sector of the Southern Ocean between November 2001 and
March 2002. Although a phytoplankton bloom occurred just after retreat of the sea ice at both stations in the seasonally ice-covered
area, vertical stability of the water column during the bloom was weak at the most southerly station. This shows that a bloom
can form even under weak vertical stability. In the bloom, diatoms dominated under weak vertical stability and Phaeocystis under strong vertical stability. In the latter case, ice algae largely contributed to development of the bloom. In the later
observation period, a subsurface chlorophyll maximum (SCM) was observed at 61°S and 64°S. Species composition was different
between the mixed layer and SCM at 64°S, but was uniform with depth at 61°S, indicating that the SCM is formed by different
mechanisms. 相似文献
18.
P. W. Lehman S. J. Teh G. L. Boyer M. L. Nobriga E. Bass C. Hogle 《Hydrobiologia》2010,637(1):229-248
The impact of the toxic cyanobacterium Microcystis
aeruginosa on estuarine food web production in San Francisco Estuary is unknown. It is hypothesized that Microcystis contributed to a recent decline in pelagic organisms directly through its toxicity or indirectly through its impact on the
food web after 1999. In order to evaluate this hypothesis, phytoplankton, cyanobacteria, zooplankton, and fish were collected
biweekly at stations throughout the estuary in 2005. Concentrations of the tumor-promoting Microcystis toxin, microcystin, were measured in water, plankton, zooplankton, and fish by a protein phosphatase inhibition assay, and
fish health was assessed by histopathology. Microcystis abundance was elevated in the surface layer of the western and central delta and reached a maximum of 32 × 109 cells l−1 at Old River in August. Its distribution across the estuary was correlated with a suite of phytoplankton and cyanobacteria
species in the surface layer and 1 m depth including Aphanizomenon spp., Aulacoseira granulata, Bacillaria paradoxa, Rhodomonas spp., and Cryptomonas spp. Shifts in the phytoplankton community composition coincided with a decrease in the percentage of diatom and green algal
carbon and increase in the percentage of cryptophyte carbon at 1 m depth. Maximum calanoid and cyclopoid copepod carbon coincided
with elevated Microcystis abundance, but it was accompanied by a low cladocera to calanoid copepod ratio. Total microcystins were present at all levels
of the food web and the greater total microcystins concentration in striped bass than their prey suggested toxins accumulated
at higher trophic levels. Histopathology of fish liver tissue suggested the health of two common fish in the estuary, striped
bass (Morone saxatilis), and Mississippi silversides (Menidia audens), was impacted by tumor-promoting substances, particularly at stations where total microcystins concentration was elevated.
This study suggests that even at low abundance, Microcystis may impact estuarine fishery production through toxic and food web impacts at multiple trophic levels. 相似文献
19.
Anna Pasternak Wilhelm Hagen Gerhard Kattner Jan Michels Martin Graeve Sigrid B. Schnack-Schiel 《Polar Biology》2009,32(11):1597-1606
Lipid content, fatty acid composition, and feeding activity of the dominant Antarctic copepods, Calanoides acutus, Calanus propinquus, and Metridia gerlachei, were studied at a quasi-permanent station in the eastern Weddell Sea in December 2003. During 3 weeks of the spring phytoplankton
development, total lipid levels of females and copepodite stages V (CVs) of C. acutus were almost doubled. Meanwhile, only a slight increase in total lipid content occurred in M. gerlachei, and no clear trend was observed in lipids of C. propinquus females. The pronounced increase of lipids in C. acutus was due to an accumulation of wax esters. The proportion of wax esters in the lipids of M. gerlachei was clearly lower, while triacylglycerols played a more important role. In C. propinquus, triacylglycerols were the only neutral lipid class. There were no pronounced changes in the feeding activity of M. gerlachei, whereas the feeding activity of C. acutus had rapidly increased with the development of the phytoplankton bloom in December, which explains its rapid lipid accumulation.
The combination of gut content and fatty acid trophic marker analyses showed that C. acutus was feeding predominantly on diatoms. The typical diatom fatty acid marker, 16:1(n-7), slightly decreased and the tracer
for flagellates, 18:4(n-3), increased in females and CVs of C. acutus. This shift indicates the time, when the significance of flagellates started to increase. The three copepod species exhibited
different patterns of lipid accumulation in relation to their trophic niches and different duration of their active phases.
The investigations filled a crucial data gap in the seasonal lipid dynamics of dominant calanoid copepods in the Weddell Sea
in December and support earlier hypotheses on their energetic adaptations and life cycle strategies. 相似文献
20.
Lincoln MacKenzie 《Journal of applied phycology》1991,3(1):19-34
Diurnal vertical profile sampling of the water column, during a fish killing bloom of the raphidophycean alga Heterosigma akashiwo, revealed a phytoplankton population otherwise composed almost entirely of a variety of dinoflagellates. Of these Glenodinium danicum, Dinophysis acuta, Polykrikos schwartzii, Ceratium furca and Gyrodinium spirale were predominant. The distribution of the major species within the phytoplankton were documented and evidence of synchronous
vertical migration of H. akashiwo, G. danicum and P. schwartzii was observed. Extracts of shellfish obtained during the bloom and tested by mouse bioassay showed no PSP toxicity but a marginal
degree of DSP toxicity. During a subsequent one year phytoplankton monitoring programme another potentially noxious species
(Chaetoceros convolutus) appeared and the seasonal reoccurrence of species present during the bloom (e.g. H. akashiwo) was observed. Important year to year differences in the summer phytoplankton (diatom versus flagellate dominated populations)
were apparent and analysis of climate data showed that these differences related to different weather conditions prevailing
during the two summer periods sampled. The data suggest the fish killing bloom was giving a chance to develop by a prolonged
period of warm, calm weather (during which several heavy rainfall events occurred) leading to stable hydrographic conditions
(i.e. stratification) and an increase in the retention time of water within the bay. 相似文献