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1.
Zooplankton samples from the North Arabian Sea Environment and Ecosystem Research (NASEER) cruises were analyzed to determine
the basic taxonomic composition, biomass (standing stock) and the total and copepod numeric abundance; these characteristics
are discussed with reference to the different monsoon periods. Cruises carried out during March 1993 and May 1994, categorized
as pre-southwest monsoon periods, and a cruise in December 1994, categorized as a northeast monsoon period, are discussed
in detail. The biomass of January 1992 versus August 1992 and August 1992 versus March 1993 differed significantly (F = 6.44, P≤ 0.05). Ranges of highest and lowest biomass from each cruise are also given. Distinct “high” and “low” production areas
of statistically significant difference (F = 12.67, P≤ 0.05) were observed. The “high” and “low” production areas were mobile and followed the surface wind circulation patterns
(wind reversal pattern) during the northeast and southwest monsoon periods. Overall zooplankton showed a patchy distribution.
The overall zooplankton abundance and total copepod counts differed significantly between the Cruises 3 versus 4 and 4 versus
5 (F = 15.67, P≤ 0.05 and F = 34.39, P≤ 0.05, respectively). There was no significant difference (P≥ 0.05) in biomass, between eutrophic and oligotrophic stations, suggesting no difference between near shore and offshore
waters. Thirty-eight taxonomic groups were identified from the samples, with copepods being the most dominant group, followed
by chaetognaths and siphonophores. Copepods constitute an average of 52.50 to 74.93% of the total zooplankton count and reach
maxima of 92.14% of the total zooplankton count at the outset of the southwest monsoon (March 1993) and 91.39% at the outset
of the active northeast monsoon (December 1994).
Received: 27 February 1998 / Accepted: 8 October 1999 相似文献
2.
Effects of ultraviolet-B enhancement on marine trophic levels in a stratified coastal system 总被引:3,自引:0,他引:3
A. A. Keller P. Hargraves H. Jeon G. Klein-MacPhee E. Klos C. Oviatt J. Zhang 《Marine Biology》1997,130(2):277-287
We examined the effects of enhanced UV-B radiation (relative to ambient) on marine trophic levels inhabiting a stratified
coastal ecosystem, using living models (13 000 liter marine enclosures) of a temperate estuarine water column. The experiment
was carried out in June and July 1994 on a plankton community drawn from lower Narragansett Bay, Rhode Island, USA. The effects
of altered UV-B radiation (elevated 50% over ambient, tenfold DNA-weighted) on three trophic strata: the primary producers
(photosynthetic algae), primary herbivores (copepods), and fish eggs and larvae (Anchoa mitchilli Cuvier and Valenciennes) were examined. The goal was to determine if UV-B–induced alterations at the base of the food chain
had impacts on other elements of the trophic web. Phytoplankton abundance (P=0.02) and biomass (P=0.007) were significantly reduced in UV-B–enhanced treatments, above but not below the thermocline (2.25 m), during the second
week of the study. Copepod nauplii were significantly less abundant in UV-B–enhanced mesocosms than in control treatments
during the third and fourth weeks of the study (P=0.01). A portion of the impact on nauplii may be a result of alterations at the base of the food web. The greater mortality
of nauplii in UV-B–enhanced systems did not translate to reduced abundance of copepodite (P=0.83) or adult (P=0.29) copepods. No significant effects were observed for microzooplankton (P=0.15). Neither the mortality rates nor the growth rates of larval anchovy were significantly affected by the experimental
increase in UV-B (P>0.05). Despite the tenfold increase in biologically damaging UV-B, effects were not seen at higher trophic levels, most likely
because of the rapid extinction of UV-B in the highly colored coastal water.
Received: 13 November 1996 / Accepted: 18 July 1997 相似文献
3.
Along the mid-Atlantic coast of the US, the ctenophore Mnemiopsis leidyi (Agassiz) appears to be increasing in abundance and undergoing shifts in its historical seasonal distribution. We provide
new data on shifting ctenophore abundance in Long Island estuaries and its implications for top-down control of the plankton
community. Peak mean biovolume estimates of M. leidyi in Long Island estuaries in 2006 revealed ctenophore abundance values that were a factor of two to five times greater than
previous studies conducted two decades ago. Furthermore, peak M. leidyi densities in 2006 occurred 2–3 months earlier than previously documented, suggesting a shift in the seasonal maxima of M. leidyi. Application of daily ingestion rates to zooplankton abundance indicates that, at its highest densities M. leidyi can remove an overall average of 20–89% per day of bivalve veligers and other zooplankton taxa, including adult copepods,
nauplii, and tintinnids. Increasing ctenophore abundance, especially during a period when they were not historically abundant
(i.e., June) may have significant consequences for species which spawn at this time. For example, current populations of M. leidyi represent a major source of larval mortality for bivalves which may inhibit recovery of shellfish populations and reinforce
their low abundance state in Long Island estuaries. 相似文献
4.
Phytoplankton blooms are strongly impacted by microzooplankton grazing in coastal North Pacific waters 总被引:1,自引:0,他引:1
Phytoplankton growth and microzooplankton grazing were measured in two productive coastal regions of the North Pacific: northern
Puget Sound and the coastal Gulf of Alaska. Rates of phytoplankton growth (range: 0.09–2.69 day−1) and microzooplankton grazing (range: 0.00–2.10 day−1) varied seasonally, with lowest values in late fall and winter, and highest values in spring and summer. Chlorophyll concentrations
also varied widely (0.19–13.65 μg l−1). Large (>8 μm) phytoplankton cells consistently dominated phytoplankton communities under bloom conditions, contributing
on average 65% of total chlorophyll biomass when chlorophyll exceeded 2 μg l−1. Microzooplankton grazing was an important loss process affecting phytoplankton, with grazing rates equivalent to nearly
two-thirds (64%) of growth rates on average. Both small and large phytoplankton cells were consumed, with the ratio of grazing
to growth (g:μ) for the two size classes averaging 0.80 and 0.42, respectively. Perhaps surprisingly, the coupling between microzooplankton
grazing and phytoplankton growth was tighter during phytoplankton blooms than during low biomass periods, with g:μ averaging 0.78 during blooms and 0.49 at other times. This tight coupling may be a result of the high potential growth
and ingestion rates of protist grazers, some of which feed on bloom-forming diatoms and other large phytoplankton. Large ciliates
and Gyrodinium-like dinoflagellates contributed substantially to microzooplankton biomass at diatom bloom stations in the Gulf of Alaska,
and microzooplankton biomass overall was strongly correlated with >8 μm chlorophyll concentrations. Because grazing tended
to be proportionally greater when phytoplankton biomass was high, the absolute amount of chlorophyll consumed by microzooplankton
was often substantial. In nearly two-thirds of the experiments (14/23), more chlorophyll was ingested by microzooplankton
than was available for all other biological and physical loss processes combined. Microzooplankton were important intermediaries
in the transfer of primary production to higher trophic levels in these coastal marine food webs.
Received: 12 November 1999 / Accepted: 4 October 2000 相似文献
5.
M. K. S. Lilley S. E. Beggs T. K. Doyle V. J. Hobson K. H. P. Stromberg G. C. Hays 《Marine Biology》2011,158(11):2429-2436
There is concern that overfishing may lead to a proliferation of jellyfish through a process known as fishing down the food
web. However, there has been no global synthesis of patterns of gelatinous zooplankton biomass (GZB), an important first step
in determining any future trends. A meta-analysis of epipelagic-GZB patterns was undertaken, encompassing 58 locations on
a global scale, and spanning the years 1967–2009. Epipelagic-GZB decreased strongly with increasing total water column depth
(r
2 = 0.543, p < 0.001, n = 58): in shallow (<50 m) coastal waters, epipelagic-GZB was typically 742× the levels in deep ocean (>2,000 m) sites. However,
the ratio of GZB to primary productivity showed high values across a range of depths, i.e. this measure of the relative abundance
of gelatinous zooplankton did not co-vary with depth. 相似文献
6.
A. Sakka Hlaili B. Grami Hassine Hadj Mabrouk M. Gosselin D. Hamel 《Marine Biology》2007,151(2):767-783
Phytoplankton growth and microzooplankton grazing were investigated in the restricted Bizerte Lagoon in 2002 and 2004. The
2002 study, carried out at one station from January to October, showed significant seasonal variations in phytoplankton dynamics.
High growth rates (0.9–1.04 day−1), chlorophyll a (Chl a) concentrations (6.6–6.8 μg l−1) and carbon biomass (392–398 μg C l−1) were recorded in summer (July), when several chain-forming diatoms had intensively proliferated and dominated the carbon
biomass (74%). In 2004, four stations were studied during July, a period also characterized by the high proliferation of several
diatoms that made up 70% of the algal carbon biomass. In 2004, growth rates (0.34–0.45 day−1) and biomass of algae (2.9–5.4 μg Chl a l−1 and 209–260 μg C l−1) were low, which may be related to the lower nutrient concentrations recorded in 2004. Microzooplankton >5 μm were mainly
composed of heterotrophic dinoflagellates and ciliates. Microzooplankton biomass peaked during summer (2002 320–329, 2004
246–361 μg C l−1), in response to the enhanced phytoplankton biomass and production. The grazer biomass was dominated by ciliates (71–76%)
in July 2002 and by heterotrophic dinoflagellates (52–67%) in July 2004. Throughout the year and at different stations, microzooplankton
grazed actively on phytoplankton, removing 26–58% of the Chl a and 57-84% of the primary production. In 2002, the highest grazing impact was observed on the large algae (>10 μm) during
the period of diatom dominance. These results have a significant implication for carbon export to depth. Indeed, the recycling
of most of the diatom production by the microbial food web in the upper water column would reduce the flux of material to
the seafloor. This should be considered when modeling the carbon cycling in coastal environments and under conditions of diatom
dominance. During both studies, ciliates had higher growth rates (0.5–1.5 day−1) and a higher carbon demand (165–470 μg C l−1 day−1) than dinoflagellates (0.1–0.5 day−1, 33–290 μg C l−1 day−1). Moreover, when grazer biomass was dominated by ciliates (in July 2002), herbivory accounted for 71–80% of the C ingested
by microzooplankton while it accounted only for 14–23% when dinoflagellates dominated the grazer biomass (in July 2004). These
results suggest that, in contrast to findings from open coastal waters, ciliate species of the restricted Bizerte Lagoon were
more vigorous grazers of the large algae (diatoms) than were dinoflagellates. 相似文献
7.
The spatial, diel and tidal variability in the abundance of piscivorous fishes and their teleost prey, and the dietary composition
of predatory fishes were investigated in beds of Heterozostera tasmanica within Port Phillip Bay, Australia, from September 1997 to February 1998. Predatory and prey fish assemblages were sampled
from beds of H. tasmanica at three locations during each combination of diel (day and night) and tidal (high and low) cycles. Pelagic and benthic crustaceans
represented >60% by abundance of the diets of all predatory fishes. Seven species, 54% of all predatory fishes, were piscivorous.
These piscivores consumed individuals from seven families, 36.8% of the fish families being associated with seagrass. Western
Australian salmon, Arripis truttacea (Arripidae) (n = 174) and yank flathead, Platycephalus speculator (Platycephalidae) (n = 46) were the most abundant piscivores. A. truttacea consumed larval/post-larval atherinids, gobiids and sillaginids. P. speculator consumed late-juvenile/adult atherinids, clinids and gobiids. While the abundances of piscivores varied between locations
(P < 0.001) and diel periods (P = 0.028), the relative differences in piscivore abundance between sites and diel periods were not consistent between tides.
The abundances of A. truttacea varied in a complex way amongst sites, diel period and tidal cycle, as shown by a three-way interaction between these factors
(P = 0.026). Only during diurnal periods at St. Leonards was the abundance of A. truttacea significantly higher during high than low tides (P < 0.001). During the other diel periods at each site, the abundance of A. truttacea did not vary. P. speculator was significantly more abundant nocturnally (P = 0.017). The abundance of small (prey) fishes varied significantly amongst sites (P < 0.001). During the day, the abundance of small fishes did not vary between high and low tides (P = 0.185), but their nocturnal abundance was greater during low tide (P < 0.001). Atherinids (n = 1732) and sillaginids (n = 1623) were the most abundant families of small fishes. Atherinids were significantly more abundant nocturnally (P = 0.005) and during low tides (P = 0.029), and varied significantly amongst sites (P < 0.001). Sillaginids varied significantly only amongst sites (P < 0.001). Seagrass beds provide a foraging habitat for a diverse assemblage of predatory fishes, many of which are piscivorous.
Anti-predator behaviour and amongst-location variability in abundances of piscivorous fishes may explain some of the diel
and tidal, and broad-scale spatial patterns in small-fish abundances.
Received: 23 July 1999 / Accepted: 18 January 2000 相似文献
8.
A. A. Keller C. Taylor C. Oviatt T. Dorrington G. Holcombe L. Reed 《Marine Biology》2001,138(5):1051-1062
The seasonal productivity cycle and factors controlling annual variation in the timing and magnitude of the winter–spring
bloom were examined for several locations (range: 42°20.35′–42°26.63′N; 70°44.19′–70°56.52′W) in Boston Harbor and Massachusetts
Bay, USA, from 1995 to 1999, and compared with earlier published data (1992–1994). Primary productivity (mg C m−2 day−1) in Massachusetts Bay from 1995 to 1999 was generally characterized by a well-developed winter–spring bloom of several weeks
duration, high but variable production during the summer, and a prominent fall bloom. The bulk of production (mg C m−3 day−1) typically occurred in the upper 15 m of the water column. At a nearby Boston Harbor station a gradual pattern of increasing
areal production from winter through summer was more typical, with the bulk of production restricted to the upper 5 m. Annual
productivity in Massachusetts Bay and Boston Harbor ranged from a low of 160 g C m−2 year−1 to a high of 787 g C m−2 year−1 from 1992 to 1999. Mean annual productivity was higher (mean=525 g C m−2 year−1) and more variable near the harbor entrance than in western Massachusetts Bay. At the harbor station productivity varied
more than 3.5-fold (CV=40%) over an 8 year sampling period. Average annual productivity (305–419 g C m−2 year−1) and variability around the means (CV=25–27%) were lower at both the outer nearfield and central nearfield regions of Massachusetts
Bay. Annual productivity in 1998 was unusually low at all three sites (<220 g C m−2 year−1) due to the absence of a winter–spring phytoplankton bloom. Potential factors influencing the occurrence of a spring bloom
were investigated. Incident irradiance during the winter–spring period was not significantly different (P > 0.05) among years (1995–1999). The mean photic depth during the bloom period was significantly deeper (P < 0.05) in 1998, signifying greater light availability with depth. Nutrients were also in abundance during the winter–spring
of 1998 with stratified conditions not observed until May. In general, the magnitude of the winter–spring bloom in Massachusetts
Bay from 1995 to 1999 was significantly correlated with winter water temperature (r
2=0.78) and zooplankton abundance (r
2=0.74) over the bloom period (typically February–April). The absence of the 1998 bloom was associated with higher than average
water temperature and elevated levels of zooplankton abundance just prior to, and during, the peak winter–spring bloom period.
Received: 3 July 2000 / Accepted: 6 December 2000 相似文献
9.
Dorte Krause-Jensen Anne Lise Middelboe Jacob Carstensen Karsten Dahl 《Marine Biology》2007,152(1):25-36
Based on a large monitoring data set from Danish coastal waters we tested the hypotheses: (1) The vertical pattern of algal
abundance is regulated by exposure in shallow water and by light limitation towards deeper water, resulting in a bell-shaped
abundance curve, with peak abundance located deeper at more exposed sites, (2) in deeper water, total algal abundance and
abundance of perennial algae decrease along a eutrophication gradient while (3) abundance and relative abundance of opportunists
increase. The vertical pattern of algal abundance showed a peak at intermediate water depths which was located deeper in more
exposed areas and thus confirmed our first hypothesis. For algae growing from depths of peak abundance and deeper, the study
demonstrated that total algal abundance and abundance of perennials and opportunists at given depths decreased significantly
along a eutrophication gradient and the relationships had high explanatory power (R
2 = 0.53–0.73). These results confirmed our second hypothesis. By contrast, the relative abundance of opportunists responded solely
to salinity and was largest in the most brackish areas, in contradiction to hypothesis three. The lack of coupling between
eutrophication and relative abundance of opportunists arises because both opportunists and the entire algal community were
light limited and their ratio therefore relatively insensitive to changing water clarity. The analyses indicated that algal
abundance initially responded slowly to increasing eutrophication but showed a more marked response at TN concentrations of
35–40 μM. However, the existence of possible threshold nutrient levels demands further analyses. 相似文献
10.
The predation impact of the two chaetognaths Eukrohnia hamata and Sagitta gazellae on mesozooplankton standing stock were investigated in three depth layers during two 24 h stations occupied in the vicinity
of Marion Island in late austral summer (April/May) 1986. The zooplankton community at both stations was dominated by small
copepods (Oithona spp., Microcalanus spp.), which accounted for >95% of total zooplankton abundance. Chaetognaths comprised <2% of total zooplankton abundance.
E. hamata constituted >95% of the total chaetognath stock. The general trend in both species was decreasing abundance with increasing
depth, which appeared to be correlated to the distribution of copepods (r
2 = 0.45; P <0.05). Gut-content analysis showed that copepods (mainly Oithona spp., Calanus spp. and Rhincalanus gigas) and ostracods were the main prey of both species, accounting for 87 and 61% of the total number of prey in E. hamata and S.␣gazellae stomachs, respectively. In the guts of S.␣gazellae, pteropods (Limacina spp.) and chaetognaths were also well represented. The mean number of prey items (NPC) for E. hamata ranged from 0.02 to 0.06 prey individual−1 which corresponds to an individual feeding rate (Fr) of between 0.05 and 0.12 prey d−1. For S.␣gazellae, the NPC values were higher, varying between 0.04␣and 0.20 prey individual−1, or between 0.15 and 0.76 prey d−1. The daily predation impact of the two chaetognaths was estimated at between 0.3 and 1.2% of the copepod standing stock or
between 7 and 16% of the daily copepod production. Predation by S. gazellae on chaetognaths accounted for up to 1.6% of the chaetognath standing stock per day.
Received: 26 November 1996 / Accepted: 31 October 1997 相似文献
11.
Zooplankton community structure across an eddy-generated upwelling band close to a tropical bay-mangrove ecosystem 总被引:2,自引:0,他引:2
M. Rakhesh A. V. Raman C. Kalavati B. R. Subramanian V. S. Sharma E. Sunitha Babu Nanduri Sateesh 《Marine Biology》2008,154(6):953-972
Mesoscale eddies in the world’s oceans are ubiquitous and bring about episodic pulses of nutrients into the photic zone. Transient
in nature, the role of eddy pumping in coastal enrichment via plankton production, and subsequent organic flux is not yet
fully realised. In the context of a cyclonic cold-core eddy that propagates annually under the influence of the East India
Coastal Current and enriches coastal waters in the western Bay of Bengal north of 16°N, a detailed study on zooplankton community
structure along with phytoplankton composition and associated water quality was undertaken during April–May 2002 coinciding
with the spring intermonsoon. Zooplankton samples were collected at 32 hydrographically different (salinity 24.5–35.6 PSU)
GPS fixed locations representing bay-mangrove areas and nearshore waters (30 m) close to the River Godavari, which is one
of India’s largest estuarine systems. During the study, the bay-coastal waters were typified by elevated nutrient levels (nitrate
10.73–22.04 μM), high salinity (27.98–35.52 PSU), and relatively low temperatures (30.63–31.40°C). Altogether, 95 zooplankton
taxa were encountered with copepods forming the predominant population. Agglomerative Hierarchical Cluster Analysis (AHCA)
and Non-metric Multidimensional Scaling (NMDS) based on Bray–Curtis similarity (PRIMER) analysis revealed appreciable alterations
in zooplankton structure across bay-mangrove locations and coastal waters (Stress 0.11; ANOSIM test Global R: 0.94, P = 0.1%). Similarity Percentage (SIMPER) analysis revealed zooplankton associations through “discriminating species” for each
location (Kakinada Bay, Cluster I, 27.9 ± 3.0 PSU; upwelling band, cluster II, 35.5 ± 0.2 PSU; offshore waters, cluster III,
34.2 ± 0.4 PSU; mangrove outlets, cluster IV, 32.7 ± 1.3 PSU and mangrove creeks, cluster V, 33.5 ± 0.6 PSU). The index of
multivariate dispersion (IMD) illustrated high variability in zooplankton standing stock for mangrove/sea locations relative
to the bay. Concurrent observations on phytoplankton revealed the importance of diatoms (r: 0.640, P ≤ 0.05). Within the eddy-generated band of upwelled water, a significant top-down control of diatoms by herbivorous zooplankton
resulted in a comparative increase in abundance of dinophyceans. Based on zooplankton abundance data and species association
patterns, it was possible to distinguish different zooplankton/copepod communities in accordance with mesoscale variability
in physical, chemical and biological processes under tropical conditions. This was confirmed through canonical correspondence
analysis (CCA) that represented coastal-offshore waters and the Bay environment in this area. 相似文献
12.
Martin G. J. Löder Cédric Meunier Karen H. Wiltshire Maarten Boersma Nicole Aberle 《Marine Biology》2011,158(7):1551-1580
Mesocosm experiments coupled with dilution grazing experiments were carried out during the phytoplankton spring bloom 2009.
The interactions between phytoplankton, microzooplankton and copepods were investigated using natural plankton communities
obtained from Helgoland Roads (54°11.3′N; 7°54.0′E), North Sea. In the absence of mesozooplankton grazers, the microzooplankton
rapidly responded to different prey availabilities; this was most pronounced for ciliates such as strombidiids and strobilids.
The occurrence of ciliates was strongly dependent on specific prey and abrupt losses in their relative importance with the
disappearance of their prey were observed. Thecate and athecate dinoflagellates had a broader food spectrum and slower reaction
times compared with ciliates. In general, high microzooplankton potential grazing impacts with an average consumption of 120%
of the phytoplankton production (P
p
) were measured. Thus, the decline in phytoplankton biomass could be mainly attributed to an intense grazing by microzooplankton.
Copepods were less important phytoplankton grazers consuming on average only 47% of P
p
. Microzooplankton in turn contributed a substantial part to the copepods’ diets especially with decreasing quality of phytoplankton
food due to nutrient limitation over the course of the bloom. Copepod grazing rates exceeded microzooplankton growth, suggesting
their strong top-down control potential on microzooplankton in the field. Selective grazing by microzooplankton was an important
factor for stabilising a bloom of less-preferred diatom species in our mesocosms with specific species (Thalassiosira spp., Rhizosolenia spp. and Chaetoceros spp.) dominating the bloom. This study demonstrates the importance of microzooplankton grazers for structuring and controlling
phytoplankton spring blooms in temperate waters and the important role of copepods as top-down regulators of microzooplankton. 相似文献
13.
In the shrimp Crangon crangon, an important fishery resource and key species in the southern North Sea, we studied temporal variations in size, biomass
(dry weight, W) and chemical composition (C, N, protein and lipid) of eggs in an initial embryonic stage. Data from 2 years, 1996 and 2009,
consistently revealed that egg size and biomass varied seasonally, with maxima at the beginning of the reproductive season
(January), decreasing values throughout spring, minima in June–July, and a slight increase thereafter. This cyclic pattern
explains why “Winter eggs” are on average larger and heavier than “summer eggs”. Using a modelling approach, we estimated
the duration of oogenesis in relation to seasonally changing seawater temperatures. According to an additive model of multiple
explanatory variables, the C content per newly laid egg showed in both years a highly significant negative relationship with
day length (r2 = 0.38 and 0.40, respectively; P < 0.0001), a weak positive relationship with temperature (r2 = 0.08 and 0.09; P < 0.05), and a weak negative relationship with phytoplankton biomass (r2 = 0.11 and 0.12; P < 0.05) at the estimated time of beginning oogenesis. Phenotypic plasticity in initial egg size and biomass is interpreted
as an adaptive reproductive trait that has evolved in regions with strong seasonality in plankton production and periods of
larval food limitation. In contrast to biomass per egg, the percentage chemical composition remained similar throughout the
reproductive period. Both the absolute and percentage values also showed significant interannual variations, which caution
against generalizations based on short-term studies of reproductive traits of C. crangon and other species of shrimp. 相似文献
14.
We experimentally investigated the effect of different densities of the burrowing, deposit-feeding amphipod Monoporeia affinis on the recruitment of zooplankton from benthic resting eggs. Intact sediment cores with in situ density and species composition
of zooplankton resting eggs and benthic fauna were collected in the northern Bothnian Sea, part of the Baltic Sea. We removed
as many M. affinis as possible from the cores and then added different numbers of M. affinis to the cores to generate a range of densities. The cores were exposed to different densities of M. affinis for either 3 or 40 days, after which the hatched zooplankton was registered. One subset of the cores were initially incubated
under low temperature (2–3 °C, to prevent hatching) for 37 days (the resting phase), to allow for effects of M. affinis on unhatched resting eggs. These cores were then incubated under higher temperature (13 °C) for 3 days (the hatching phase),
to induce hatching and allow for effects on hatching or hatched specimens. In a second subset of cores with the same time
and temperature schedule, the M. affinis density was experimentally reduced at the start of the hatching phase, to evaluate the effect of M. affinis during the hatching phase. To a third subset of cores, we immediately initiated the hatching phase, without an experimental
resting phase, to evaluate the effects induced during the resting phase. The most common zooplankton species that hatched
was Eurytemora affinis (Copepoda), followed by Bosmina longispina maritima (Cladocera). In all cores that were subjected to a resting phase, the numbers of hatched E. affinis were log-linearly negatively related to density of M. affinis. An increase of M. affinis density from 1,000 to 5,000 individuals m−2, normal field densities, reduced the hatching by 60–70%. The negative impact was mainly exerted during the hatching phase,
suggesting predation on, burial of or physical injury of hatching nauplii or eggs in a late development stage as likely mechanisms.
Also, the number of B. longispina maritima that hatched was reduced by M. affinis during the hatching phase, but no clear relation to density of M. affinis could be identified. The results show that M. affinis can reduce recruitment to zooplankton from benthic resting eggs. Such impact by the benthos on resting stages of zooplankton
is therefore a potentially significant link between the benthic and pelagic systems.
Received: 10 August 2000 / Accepted: 13 November 2000 相似文献
15.
Coupled bio-physical models of larval dispersal predict that the Costa Rica–Panama (CR–PAN) reefs should constitute a demographically
isolated region in the western Caribbean. We tested the hypothesis that CR–PAN coral reef fish populations would be isolated
from Mesoamerican Barrier Reef System (MBRS) populations. To test that, we assessed population genetic structure in bicolor
damselfish (Stegastes partitus) from both regions. Adult fish were genotyped from five reefs in CR–PAN and from four reefs along the MBRS at 12 microsatellite
loci. Between-region F
ST (F
ST = 0.0030, P < 0.005) and exact test (x
2 = 74.34, df = 18, P < 0.0001) results indicated that there is weak but significant genetic differentiation between regions, suggesting some restriction
in connectivity along the Central American coastline, as predicted by bio-oceanographic models. Additionally, there is among-site
genetic structure in the CR–PAN region, relative to the MBRS and between regions, suggesting higher self-recruitment within
CR–PAN. This finding may be explained by differences in habitat characteristics. 相似文献
16.
Weight-specific contents of asorbic acid, thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, biotin, folate and vitamin B12 were analysed in natural zooplankton collected from a sea water lagoon in a halibut fry production plant. The samples of
natural zooplankton were collected from April/May to the end of June during two consecutive spring blooms. For comparison,
the same vitamins were measured in nauplii of Artemia franciscana, just after hatching and after enrichment for 24 and 48 h with a commercial diet. The changes in vitamin content in zooplankton,
which consisted mainly of Temora longicornis, during the two spring blooms were <2.5-fold for each specific vitamin. The large number of high quality halibut fry produced
using the plankton as a dietary source suggests that the plankton contained sufficient amounts of all water-soluble vitamins.
With the exception of thiamin and ascorbic acid, Artemia– both newly hatched and enriched for 24 and 48 h – contained higher levels of water-soluble vitamins than natural zooplankton.
Enrichment feeding of Artemia for 48 h stabilised or increased the level of the water-soluble vitamins.
Received: 8 March 1999 / Accepted: 21 February 2000 相似文献
17.
Natasha Henschke Jason D. Everett Martina A. Doblin Kylie A. Pitt Anthony J. Richardson Iain M. Suthers 《Marine Biology》2014,161(1):149-163
Swarms of the pelagic tunicate, Thalia democratica, form during spring, but the causes of the large interannual variability in the magnitude of salp swarms are unclear. Changes in asexual reproduction (buds per chain) of T. democratica populations in the coastal waters of south-east Australia (32–35°S) were observed in three austral springs (October 2008–2010). T. democratica abundance was significantly higher in 2008 (1,312 individuals m?3) than 2009 and 2010 (210 and 92 individuals m?3, respectively). There was a significant negative relationship (linear regression, r 2 = 0.61, F 1,22 = 33.83, P < 0.001) between abundance and asexual reproduction. Similarly, relative growth rates declined with decreasing abundance. Generalised additive mixed modelling showed that T. democratica abundance was significantly positively related to preferred food >2 μm in size (P < 0.05) and negatively related to the proportion of non-salp zooplankton (P < 0.001). Salp swarm magnitude, growth, and asexual reproduction may depend on the abundance of larger phytoplankton (prymnesiophytes and diatoms) and competition with other zooplankton. 相似文献
18.
A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine calanoid copepod Acartia tonsa from southern Europe (Portugal). Development was followed from egg to adult in the laboratory at four temperatures (10, 15, 18 and 22°C) and under saturating food conditions (>1,000 μg C l−1). Development times versus incubation temperature were fitted to a Belehradek’s function, showing that development times decreased with increasing incubation temperature: at 10°C, A. tonsa need 40.3 days to reach adult stage, decreasing to 8.9 days when reared at 22°C. ANCOVA (homogeneity of slopes) showed that temperature (P<0.001) and growth phase (P<0.01) had a significant effect on the growth rate. Over the range of temperatures tested in this study, highest weight-specific growth rates were found during naupliar development (NI–NVI) and varied from 0.185 day−1 (10°C) to 0.880 day−1 (22°C) with a Q
10 equal to 3.66. During copepodite growth (CI–CV), the weight-specific growth rates ranged from 0.125 day−1 (10°C) to 0.488 day−1 (22°C) with a Q
10 equal to 3.12. The weight-specific growth rates (g) followed temperature (T) by a linear relationship and described as ln g=−2.962+0.130 T (r
2=0.99, P<0.001) for naupliar stages and ln g=−3.134+0.114T (r
2=0.97, P<0.001) for copepodite stages. By comparing in situ growth rates (juvenile growth and fecundity) for A. tonsa taken from the literature with the temperature-dependent growth model defined here we suggest that the adult females of A. tonsa are more frequently food limited than juveniles. 相似文献
19.
Copepod grazing impact on planktonic communities has commonly been underestimated due to the lack of information on naupliar
feeding behaviour and ingestion rates. That is particularly true for small cyclopoid copepods, whose nauplii are mainly in
the microzooplankton size range (<200 μm). The trophic role of Oithona spp. nauplii was investigated off Concepción (central Chile, ~36°S) during the highly productive upwelling season, when maximum
abundances of these nauplii were expected. Diet composition, ingestion rates, and food-type preferences were assessed through
grazing experiments with different size fractions of natural planktonic assemblages (<3, <20, <100, and <125 μm) and cultures
of the nanoflagellate Isochrysis galbana. When the Oithona spp. nauplii were offered a wide range of size fractions as food (pico- to microplankton), they mostly ingested small (2–5 μm)
nanoflagellates (5–63 × 103 cells nauplius−1 day−1). No ingestion on microplankton was detected, and picoplankton was mainly ingested when it was the only food available. Daily
carbon (C) uptake by the nauplii ranged between 28 and 775 ng C nauplius−1, representing an overall mean of 378% of their body C. Our relatively high ingestion rate estimates can be explained by methodological
constraints in previous studies on naupliar feeding, including those dealing with “over-crowding” and “edge” effects. Overall,
the grazing impact of the Oithona spp. nauplii on the prey C standing stocks amounts up to 21% (average = 13%) for picoplankton and 54% (average = 28%) for
nanoplankton. These estimates imply that the nauplii of the most dominant cyclopoid copepods exert a significant control on
the abundances of nanoplankton assemblages and, thereby, represent an important trophic link between the classical and microbial
food webs in this coastal upwelling system. 相似文献
20.
Effects of mussel (Perna canaliculus) biodeposit decomposition on benthic respiration and nutrient fluxes 总被引:1,自引:0,他引:1
Suspension-feeding bivalves increase the quantity and quality of sedimenting organic matter through the production of faeces and pseudofaeces that are remineralised in coastal sediments and thus increase sediment oxygen demand and nutrient regeneration. Bivalves are intensively cultivated worldwide; however, no bivalve biodeposit decay rates are available to parameterise models describing the environmental effects of bivalve culture. We examined sediment biogeochemical changes as bivalve biodeposits age by incubating coastal sediments to which we added fresh mussel (Perna canaliculus) biodeposits and measured O2 and nutrient fluxes as well as sediment characteristics over an 11-day period. Biodeposits elevated organic matter, chlorophyll a, phaeophytin a, organic carbon and nitrogen concentrations in the surface sediments. Sediment oxygen consumption (SOC) increased significantly (P=0.016) by ∼1.5 times to 1,010 μmol m−2 h−1 immediately after biodeposit addition and remained elevated compared to control cores without additions for the incubation period. This increase is in the range of observed in situ oxygen demand enhancements under mussel farms. To calculate a decay rate for biodeposits in sediments we fitted a first-order G model to the observed increase in SOC. The significant model fit (P=0.001, r
2=0.72) generated a decay rate of 0.16 day−1 (P=0.033, SE=0.05) that corresponds to a half-life time of 4.3 day. This decay rate is 1–2 orders of magnitude higher than published decay rates of coastal sediments without organic enrichment but similar to rates of decaying zooplankton faecal pellets. NH4+ release increased rapidly on the day of biodeposit addition (P=0.013) and reached a maximum of 144 μmol m−2 h−1 after 5 days which was 3.6 times higher compared to control cores. During this period NH4+ release was significantly (P<0.001 to P=0.043) higher in the cores with biodeposit additions than in control cores. 相似文献