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1.
Copepod grazing impact on the trophic structure of the microbial assemblage of the San Pedro Channel, California 总被引:3,自引:0,他引:3
In August 2002 and March 2003 the trophic structure of the microbialassemblage from the San Pedro Channel, California was studiedfollowing the experimental alteration of the number of copepods.Changes in the abundance/biomass of microorganisms <80 µmduring 3-day incubations were monitored in (i) the absence ofmetazoa >80 µm, (ii) the presence of natural abundancesof metazoa and (iii) the presence of an elevated number of copepods.Prokaryotes and small-sized eukaryotes (<4 µm) dominatedplankton biomass during both experimental months. Diatoms numericallydominated the 1080 µm plankton in August 2002,but ciliate and heterotrophic dinoflagellate biomass generallyexceeded diatom biomass on both dates. Ingestion of protozooplankton(predominantly ciliates) contributed substantially to copepoddaily carbon rations. The adult copepod assemblage removed 4.6and 36% per day of the microzooplankton standing stocks (1080µm size fraction) in August and March, respectively. Elevatedcopepod grazing pressure on protozooplankton resulted in increasedbiomass of nanoplankton (<5 µm) presumably via a trophiccascade. Accordingly, the copepodprotozoan trophic linkappears to be a key factor structuring the planktonic microbialassemblage in the San Pedro Channel.
This paper is one of six on the subject of the role of zooplanktonpredatorprey interactions in structuring plankton communities. 相似文献
2.
Delphine Benoit Yvan Simard Jacques Gagné Maxime Geoffroy Louis Fortier 《Polar Biology》2010,33(11):1505-1520
The winter/spring vertical distributions of polar cod, copepods, and ringed seal were monitored at a 230-m station in ice-covered
Franklin Bay. In daytime, polar cod of all sizes (7–95 g) formed a dense aggregation in the deep inverse thermocline (160–230 m,
−1.0 to 0°C). From December (polar night) to April (18-h daylight), small polar cod <25 g migrated into the isothermal cold
intermediate layer (90–150 m, −1.4°C) at night to avoid visual predation by shallow-diving immature seals. By contrast, large
polar cod (25–95 g), with large livers, remained below 180 m at all times, presumably to minimize predation by deep-diving
mature seals. The diel vertical migration (DVM) of small polar cod was precisely synchronized with the light/dark cycle and
its duration tracked the seasonal lengthening of the photoperiod. The DVM stopped in May coincident with the midnight sun
and increased schooling and feeding. We propose that foraging interference and a limited prey supply in the deep aggregation
drove the upward re-distribution of small polar cod at night. The bioluminescent copepod Metridia longa could have provided the light needed by polar cod to feed on copepods in the deep aphotic layers. 相似文献
3.
Trophodynamics of the plankton community at Dogger Bank: predatory impact by larval fish 总被引:2,自引:1,他引:1
The trophodynamics of a coastal plankton community were studied,focusing on fish larvae and their copepod prey. The major objectiveswere to describe distributional overlap and evaluate the predatoryimpact by larval fish. The study was carried out across DoggerBank in the North Sea, August-September 1991. Sampling transectscrossed tidal fronts off the Bank and plankton at all trophiclevels showed peak abundance within frontal zones. Also Verticallythere was a significant overlap in distributional patterns ofthe plankton. Seven species of fish larvae were abundant, ofthese sprat (Sprattus sprattus) dominated. The abundance ofone group of fish larvae peaked in the shallow water close tothe Bank, whereas other species, including sprat, were foundin deeper water. Prey preference and predation pressure of fishlarvae were assessed using information on prey sizes and growthrates of larvae and the copepod prey. We estimated larval removalof preferred prey sizes to 34% day1, counterbalancedby a 37% day1' replenishment from copepod productionand growth. Additional predation pressure on copepods by aninvertebrate predator was estimated to 13%day1.In conclusion, the dynamics of fish larvae and other zooplankterswere closely linked. At peak abundances of fish larvae (>35mg dry weight m2), the accumulated predation on specificsize ranges of copepods, exerted by larvae and other predators,could exceed the ability of copepod replenishment and intra-/interspecificcompetition among predators might take place. 相似文献
4.
Trophodynamics and predation impact of the 2 dominant chaetognaths Eukrohnia hamata and Sagitta gazellae were investigated at 19 stations in the vicinity of the Prince Edward Islands and at a 24-h station occupied at the sub-Antarctic
Front in late summer (April/May) 1996. During the entire investigation, the zooplankton assemblages were numerically dominated
by copepods with densities ranging from 21 to 170 ind. m−3. Amongst the copepods, Clausocalanus brevipes, Metridia gerlachei and M. lucens dominated accounting for >90% of the total. Generally, chaetognaths were identified as the second most important group composing
at times up to 30% (mean = 14.7%) of total zooplankton abundance. Of the two chaetognath species, E.␣hamata was generally numerically dominant. Gut content analysis showed that both chaetognath species are opportunistic predators
generally feeding on the most abundant prey, copepods. No feeding patterns were evident during the 24-h station, suggesting
that both species feed continuously. The feeding rates of E. hamata ranged from 0 to 0.50 prey ind. day−1 and between 0 and 0.90 prey ind. day−1 for S. gazellae. The maximum total predation impact of E. hamata was equivalent to 5.2% of the copepod standing stock or up to 103% of copepod production per day. For S. gazellae the predation impact was lower, reaching a level of 3.2% of the copepod standing stock or 63% of the daily copepod production.
Chaetognaths can, therefore, be regarded as an important pelagic predator of the Prince Edward Islands subsystem.
Received: 27 March 1997 / Accepted: 11 September 1997 相似文献
5.
Copepods are considered to be the main component of the Arctic marine zooplankton. We examined the copepod distribution and
diversity off Franz Josef Land (northern Barents Sea) in August 2006 and 2007. A total of 18 and 14 copepod taxa were identified
from the sampling layers (100–0 m or bottom–0 m) in 2006 and in 2007, respectively. There were no significant differences
in the total copepod abundance between the years (means ± SE: 118,503 ± 24,115 individuals m−2 in 2006 vs. 113,932 ± 28,564 individuals m−2 in 2007). However, the copepod biomass in 2006 (4,518 ± 1,091 mg C m−2) exceeded clearly the value in 2007 (1,253 ± 217 mg C m−2). The copepod community showed low species richness and diversity in both years (Simpson index D: 0.34 and 0.38, respectively).
Biomass of the large and small copepod species strongly decreased from 2006 to 2007. The total abundance of copepods was negatively
correlated with water temperature in 2006 and positively correlated with salinity in 2007. The patchiness in copepod distribution
was associated with local hydrography and temperature conditions. 相似文献
6.
To estimate the predation effect of the predominant ctenophorePleurobrachia bachei on the small-copepod community in the upwellingarea off Mejillones (23°S), northern Chile, a series ofoceanographic cruises and predation experiments were conductedin the austral springs 2000, 2001 and 2002. The daily consumptionrates and predatory effect of P. bachei on the small copepods(in terms of % of standing stock and biomass removed daily)were determined at three stations located in relation to theshelf-break (coastal, shelf-break and oceanic) reaching valuesup to 4.5% per day of the <1500 µm copepod standingstock. Our results indicate that the ctenophores were most abundantat the coastal station, that small copepods dominated the copepodcommunity (being more abundant nearshore), and that the relativefrequency of ctenophores with copepods in their guts was alsohigher near the coast. The predatory effect of P. bachei onthe small-copepod community was also higher in the coastal zone.However, the effect of this predation on the copepod biomassin terms of carbon did not decrease steadily seawards, whichmay be due to the larger sized copepods consumed at the offshorestations. Determinations of predatory effect on the secondaryproduction of the more abundant small-copepod populations (i.e26% daily in 2000) suggest that this single species of Pleurobrachiais modulating the population growth rate of the small copepods,the copepod community size structure, and maybe even the alternanceof key species in the Mejillones coastal upwelling zone. 相似文献
7.
Attenuation of the vertical flux of copepod fecal pellets under Arctic sea ice: evidence for an active detrital food web in winter 总被引:1,自引:0,他引:1
Makoto Sampei Alexandre Forest Hiroshi Sasaki Hiroshi Hattori Ryosuke Makabe Mitsuo Fukuchi Louis Fortier 《Polar Biology》2009,32(2):225-232
A variable fraction of fecal pellets produced in the epipelagic layer is intercepted and retained before reaching the bottom.
We assessed fecal pellet retention in the ice-covered Beaufort Sea in early February by comparing the shape and size-frequency
distribution of pellets collected by a sediment trap moored at 210 m to that produced in vitro. Appendicularian ellipsoidal
and copepod cylindrical pellets made up 75 and 24% of the flux (165 μg C m−2 day−1). In contrast, production (135 μg C m−2 day−1) was dominated by cylindrical pellets (93%). The vertical flux of cylindrical pellets at 210 m was attenuated by 70%. Pellets
>120 μm in width, represented 42% of the production, but were not detected in the trap. Retention most likely resulted from
coprorhexic feeding by copepods such as Metridia longa. Our observations suggest that the detritivore food web prevailing under the ice of the Arctic Ocean in winter is dominated
by appendicularians feeding on pellets fragmented by copepods. 相似文献
8.
The aim of this paper is to contribute to the knowledge on the feeding habits of larvae and juvenile Pleuragramma antarcticum in the western Ross Sea. In summer, the diet of P. antarcticum postlarvae (8–17 mm) was dominated by calanoid eggs (35.5%), Limacina (32.1%) and tintinnids (17.6%), while the principal food of juveniles consisted mainly of copepods (98.2%), with Oncaea curvata being the most abundant (85.1%) and the most frequently consumed prey. The food composition of P. antarcticum postlarvae (24–29 mm), collected in spring, suggest that they fed actively under the sea ice. Stephos longipes, Harpacticus furcifer and Paralabidocera antarctica sea ice copepods represent, in all their different developmental stages, the most abundant biomass food in Terra Nova Bay
in this period. Our results therefore suggest that the diet of younger Pleuragramma specimens shifted in prey composition from the first summer to the following spring. This study draws attention to the key
role of the copepod, P. antarctica, in the food web of Terra Nova Bay.
This article belongs to a special topic: Five articles coordinated by L. Guglielmo and V. Saggiomo appear in this issue of
Polar Biology and are a result of a workshop on Sea-ice communities in Terra Nova Bay (Ross Sea) held in August 2007 in Capo
Calavà, Messina, Italy. 相似文献
9.
Li-Chun Tseng Hans-Uwe Dahms Qing-Chao Chen Jiang-Shiou Hwang 《Helgoland Marine Research》2009,63(4):327-337
The South China Sea (SCS) is the world’s largest marginal sea being notable for vertical mixing at various scales resulting
in a sequence of chemical and biological dynamics in surface waters. We investigated the ingestion, gut content, evacuation
and clearance rates of copepods collected from six stations (including a South East Asia Time Series station) along a transect
line in the tropical of a SCS cruise during September 27, 1999 to October 2, 1999. The goal of the present study was to understand
the feeding ecology of copepods in the upper water layers (0–5 m) of the northern SCS during autumn. We measured the gut pigment
contents of 33 copepod species by the gut fluorescence method. The gut chlorophyll a values of most small size copepods (<1 mm) were lower than 1.00 ng Chl a individual−1. The highest gut pigment content was recorded in Scolecithrix danae (7.07 ng Chl a individual−1). The gut pigment contents of 33 copepod species (including 70 samples and 1,290 individuals) estimated is negatively correlated
with seawater temperature (Pearson correlation r = −0.292, P = 0.014) and is positively correlated with the chlorophyll a concentration of ambient waters (Pearson correlation r = 0.243, P = 0.043). Mean gut pigment content, ingestion and clearance rates (from 80 samples and 1,468 individuals) show that larger
copepods (>2 mm) had significantly higher values than medium sized copepods (1–2 mm) and smaller sized copepods. The present
study shows that the performance of feeding on phytoplankton was variable in different sized copepod groups, suggesting that
copepods obtained in the tropical area of the southeastern Taiwan Strait might be opportunistic feeders. 相似文献
10.
Gustavo A. Thompson Estela O. Dinofrio Viviana A. Alder 《Helgoland Marine Research》2012,66(2):127-138
The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200?C300-??m mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (<300???m and >300???m), in superficial waters (9?m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind L?1 and 28,300???g C m?3. The <300-??m fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the 3?years; it accounted for more than 77% of the total number and for between 40 and 63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the >300-??m fraction showed no changes among the 3?years, both in Antarctic (density and biomass) and in Subantarctic waters (density), whereas the <300-??m fraction showed higher (density and biomass) values in 2001 both in Subantarctic and in Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the <300-??m fraction. 相似文献
11.
E. A. Pakhomov H. M. Verheye A. Atkinson R. K. Laubscher J. Taunton-Clark 《Polar Biology》1997,18(3):180-192
Mesozooplankton abundance, community structure and grazing impact were determined during late austral summer (February/March)
1994 at eight oceanic stations near South Georgia using samples collected with a Bongo and WP-2 nets in the upper 200-m and
100-m layer, respectively. The zooplankton abundance was generally dominated by copepodite stages C3–C5 of six copepod species:
Rhincalanus gigas, Calanus simillimus, Calanoides acutus, Metridia spp., Clausocalanus laticeps and Ctenocalanus vanus. Most copepods had large lipid sacs. All copepods accounted for 41–98% of total zooplankton abundance. Juvenile euphausiids
were the second most important component contributing between 1 and 20% of total abundance. Pteropods, mainly Limacina inflata, were important members of the pelagic community at two sites, accounting for 44 and 53% of total abundance. Average mesozooplankton
biomass in the upper 200 m was 8.0 g dry weight m−2, ranging from 4.3 to 11.5 g dry weight m−2. With the exception of Calanussimillimus, gut pigment contents and feeding activity of copepod species were low, suggesting that some species, after having stored
large lipid reserves, had probably started undergoing developmental arrest. Daily mesozooplankton grazing impact, measured
using in situ gut fluorescence techniques and in vitro incubations, varied widely from <1 to 8% (mean 3.5%) of phytoplankton
standing stock, and from 5 to 102% (mean 36%) of primary production. The highest grazing impact was found northeast of the
island co-incident with the lowest phytoplankton biomass and primary production levels.
Received: 30 October 1996 / Accepted: 23 February 1997 相似文献
12.
The composition and ecological role of ciliates and dinoflagellates were investigated at one station in Kongsfjorden, Svalbard,
during six consecutive field campaigns between March and December 2006. Total ciliate and dinoflagellate abundance mirrored
the seasonal progression of phytoplankton, peaking with 5.8 × 104 cells l−1 in April at an average chlorophyll a concentration of 10 μg l−1. Dinoflagellates were more abundant than ciliates, dominated by small athecates. Among ciliates, aloricate oligotrichs dominated
the assemblage. A large fraction (>60%) of ciliates and dinoflagellates contained chloroplasts in spring and summer. The biomass
of the purely heterotrophic fraction of the ciliate and dinoflagellate community (protozooplankton) was with 14 μg C l−1 highest in conjunction with the phytoplankton spring bloom in April. Growth experiments revealed similar specific growth
rates for heterotrophic ciliates and dinoflagellates (<0–0.8 d−1). Food availability may have controlled the protozooplankton assemblage in winter, while copepods may have exerted a strong
control during the post-bloom period. Calculations of the potential grazing rates of the protozooplankton indicated its ability
to control or heavily impact the phytoplankton stocks at most times. The results show that ciliates and dinoflagellates were
an important component of the pelagic food web in Kongsfjorden and need to be taken into account when discussing the fate
of phytoplankton and biogeochemical cycling in Arctic marine ecosystems. 相似文献
13.
Zervoudaki S.; Christou E. D.; Nielsen T. G.; Siokou-Frangou I.; Assimakopoulou G.; Giannakourou A.; Maar M.; Pagou K.; Krasakopoulou E.; Christaki U.; Moraitou-Apostolopoulou M. 《Journal of plankton research》2007,29(4):317-338
Distribution, production and grazing of the copepod communitywere investigated in the northern Aegean Sea, which is characterizedby a permanent thermohaline front. Cruises were conducted alonga transect crossing the frontal area during spring and latesummer. Biomass and production of autotrophs were measured bysize fractionation and heterotrophic nanoflagellates and ciliateswere also studied. Copepod biomass, production and grazing impacton the phytoplankton and ciliate populations were estimated.The copepod community was sampled with a 45 µm net toinclude the smallest species and their developmental stages.The size, structure and distribution of the phytoplankton implythat most carbon was fixed by picoplankton during both seasonsand throughout the study area. The partitioning of carbon amongthe different plankton compartments was not a broad-based pyramidand the biomass of heterotrophs was higher than that of autotrophs,except in the non-frontal region during spring. Copepod biomasswas substantially higher in the frontal area. Our results showedthat the small-sized copepods (calanoids and cyclopoids) dominatedin terms of biomass and production, but also had a greater influenceon the efficiency of the trophic coupling between the primaryproducers and the protozooplankton than the larger species,stressing their importance in the northern Aegean Sea and theEastern Mediterranean in general. 相似文献
14.
Inspection of two female colonies of the monopodial black coral Cirrhipathes cfr. anguina from the coral reef of the Marine Park of Bunaken (Indonesia) revealed the occurrence of crustacean developing eggs within
the mesenterial filaments of the polyps. Egg diameter, which in the smallest gametes was about 50–60 μm, increased in tandem
with embryo development, reaching the value of 170 μm, at the nauplius stage. The attribution to the crustacean taxon was
derived from morphological investigations carried out in light and electron microscopy (TEM, SEM) on the eggs and on the embryos
removed from them. The final stage of nauplius was characterised by three pairs of appendages: uniramouse antennulae, biramouse
antennae and manidibulae. In addition, naupliar eye and caudal setae were also evident. These nauplii were ascribed to the
larval stage of an unidentified species. Coral/copepod association could represent a reproductive strategy, put into action
by some marine copepods. Incubation within an appropriate host prevents predation by planktotrophic organisms, thus reducing
population depletion. 相似文献
15.
Distribution of 0-group cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in August–September 2005 and 2006 was mainly restricted to the Atlantic waters of the western and central areas of the Barents
Sea. The main distribution of 0-group fish overlapped largely with areas of high biomass (>7 gm−2 dry weight) of zooplankton. The copepod Calanus finmarchicus and krill Thysanoessa inermis, which are dominant zooplankton species in both Atlantic and boreal waters of the Barents Sea, were the main prey of 0-group
cod and haddock. The main distribution, feeding areas and prey of 0-group cod and haddock overlapped, implying that competition
for food may occur between the two species. However, though their diet coincided to a certain degree, haddock seems to prefer
smaller and less mobile prey, such as Limacina and appendicularians. As 0-group fish increased in size, there seems to be a shift in diet, from small copepods and towards
larger prey such as krill and fish. Overall, a largely pelagic feeding behaviour of 0-group cod and haddock was evident from
this study. 相似文献
16.
Mesozooplankton biomass and abundance were evaluated in epipelagic waters at 59 stations covering the Italian sector of the
Ligurian Sea (north-western Mediterranean) in December 1990. This region is characterised by a cyclonic circulation which
encloses a central divergence zone and is associated with a main thermohaline front offshore the western Ligurian coast. At
the end of autumn, mesozooplankton biomass (range: 0.80–4.24 mg DW m−3) and the abundance (range: 83.8–932 ind. m−3) were lower in the divergence zone. On the contrary, in the Ligurian frontal zone at the periphery of the divergence and
on the eastern continental shelf the greatest values of biomass and abundance were recorded. Copepods and appendicularians
dominated the mesozooplankton community, the main taxa being the copepods Clausocalanus spp. (46% of total zooplankton) and Oithona spp. (15%) and the appendicularian Fritillaria spp. (12%). Three hydrological sub-regions, i.e. the divergence, the eastern continental shelf and the periphery of the divergence,
were characterised by different zooplankton communities and characteristic species. Environmental differences between the
three zones were mainly related to changes in bottom topography, sea surface temperatures and quantity of particulate organic
matter. Vertical mesozooplankton abundance and taxa distribution from the surface to 1,900 m depth were also examined in one
station. The results showed that the bulk of the community was concentrated in the upper 200 m, small copepods being dominant
particularly in the upper 50 m. The copepod community was more diversified in sub-superficial waters, with a maximum observed
in the 200–400 m layer. The distributions of main zooplankton taxa described in epipelagic waters in the eastern Ligurian
Sea in autumn were compared with their distribution at surface in the north-western Mediterranean obtained by sampling performed
with the Continuous Plankton Recorder in 1997–1999. The analysis of the zooplankton community in CPR samples confirms the
dominance of small copepods (Paracalanus spp., Clausocalanus spp., Oithona spp.) and appendicularians in the north-western Mediterranean in late autumn-winter and shows that their distribution is
mainly related to the main mesoscale hydrographic features characterising this basin.
Guest editors: S. Souissi & G. A. Boxshall
Copepoda in the Mediterranean: Papers from the 9th International Conference on Copepoda, Hammamet, Tunisia 相似文献
17.
Data was collected on the population structure and fecundity of the mysidNeomysis integer and the calanoid copepodEurytemora affinis in Hickling Broad, a shallow and eutrophic brackish lake, over a two-year period 1988/89. Standing biomass and production
rate estimates were made using estimates of size-specific dry weights and development times obtained from laboratory measurements,
field observations and information found in the literature. Both mysid and copepod are capable of a rapid response to favourable
conditions and have high rates of birth, growth and production.E. affinis reproduces throughout the year with an estimated annual (May 1988–May 1989) production of 20 g dry wt m−2. Copepod standing biomass was less in 1989 compared with 1988 owing to an overall reduction in copepod body-size and a reduction
of size at maturity. There was a suggestion from the data that this was caused by predation from a greater number of large
(>9 mm body-length) mysids in 1989 compared with 1988.N. integer is highly seasonal in its growth with distinct peaks of recruitment in May and July. Annual (May 1988–May 1989) production
of the mysid was estimated as 5.8 g dry wt m−2. AlthoughE. affinis is the only available prey ofN. integer in the lake, the mysid population appears independent of changes in that of the copepod and probably avoids negative predator-prey
feedback mechanisms owing to an ability to feed on epiphytic algae. 相似文献
18.
Omnivory and predation impact of the calanoid copepod Boeckella poppei in a maritime Antarctic lake 总被引:1,自引:0,他引:1
The copepod Boeckella poppei is a major species in high latitude lakes of the Southern Hemisphere. In such lakes the reduced diversity of metazoans contrasts
with a rich microbial assemblage, making these systems amenable to the study of predation controls on the microbial food web.
However, the diet of B. poppei is subject to conflicting reports, with little information on feeding rates. We incubated this species in water from Sombre
Lake, a much-studied maritime Antarctic Lake on the South Orkney Islands, in order to quantify its feeding rates and potential
impact on the microbial assemblage. Overall, clearance rates were similar across 4 experiments spanning November 1999–March
2000, but increased with prey size over the range of 2.7–18 μm equivalent spherical diameter (esd). B. poppei fed omnivorously, although small phototrophic flagellates comprised the bulk of the diet because of their overwhelming dominance
in the incubation water. Larger motile preys—heterotrophic ciliates of ~18 μm esd—were cleared fastest (mean 555 ml mg−1 dry mass day−1) and at equivalent rates to those found for freshwater and marine copepods of similar size and at similar temperatures. Estimated
predation impact on the microbial food web varied with the abundance of copepods; these were ~30-fold greater in March than
in December. In March even the relatively abundant B. poppei (1.7 adults l−1) had a negligible impact on nanoflagellates, due to the low clearance rate on these small cells. However, in March, B. poppei adults were estimated to clear 24% of the lake water of ciliates daily. Given the generation time of ciliates (1.6 days measured
in a previous summer study), and the fact that other larval stages of B. poppei were not assessed, this species has the potential to control this part of the microbial assemblage in Sombre Lake. 相似文献
19.
Tolo Harbour is a poorly flushed bay in the northeastern corner of Hong Kong. Eutrophication caused by discharge of untreated
and secondarily treated sewage into the bay was first detected during the 1970s. Increased nutrient input led to a noticeable
increase in algal biomass and algal bloom occurrences. Nutrient reduction measures, including the construction of a pipeline
to export all sewage effluents from Tolo Harbour, were introduced during the late 1980s. Decline in nutrient levels and decrease
in the number of algal blooms have been recorded since 1998 when all nutrient reduction measures became fully operational.
Zooplankton samples collected during 2003–2004 revealed that Tolo Harbour still contained a higher density and lower diversity
of planktonic copepods compared to Mirs Bay, a less-polluted sea area outside Tolo Harbour. A comparison between data collected
in this study to those collected during 1988–1990, several years before nutrient reduction measures were to be fully implemented,
showed a decrease in copepod densities and an increase in copepod diversity. Small copepods, notably species of Paracalanus and Oithona, dominated the copepod communities in both periods, but there was an increase in species evenness during 2003–2004, caused
by an increase in the number of dominant species. These observations confirm that eutrophication may lead to increases in
copepod densities accompanied by increased dominance of small species. 相似文献
20.
Copepod abundance in the western Irish Sea: relationship to physical regime, phytoplankton production and standing stock 总被引:1,自引:0,他引:1
Gowen R.J.; McCullough G.; Dickey-Collas M.; Kleppel G.S. 《Journal of plankton research》1998,20(2):315-330
The distinct patterns of stratification in the North Channeland stratified region of the western Irish Sea influence theseasonal abundance of phytoplankton. The 34 month productionseason in the stratified region was characterized by productionand biomass peaks in the spring (up to 2378 mg C m2 day1and 178.4 mg chlorophyll m2) and autumn (up to 1280 mgC m2 day1 and 101.9 mg chlorophyll m2).Phytoplankton in the North Channel exhibited a short, late productionseason with a single summer (June/July) peak in production (4483mg Cm2 day1) and biomass (160.6 mg chlorophyllm2). These differences have little influence on copepoddynamics. Both regions supported recurrent annual cycles ofcopepod abundance with similar seasonal maxima (182.8241.8103ind. m2) and dominant species (Pseudocalanus elongatusand Acartia clausi). Specific rates of population increase inthe spring were 0.071 and 0.048 day1 for the North Channel andstratified region, respectively. Increased copepod abundancein the stratified region coincided with the spring bloom, andwas significantly correlated with chlorophyll standing stock.Increased copepod abundance preceded the summer production peakin the North Channel. This increase was not correlated withchlorophyll standing crop, suggesting that a food resource otherthan phytoplankton may be responsible for the onset of copepodproduction prior to the spring bloom. Hetero-trophic microplanktonas an alternative food source, and advection of copepods fromthe stratified region, are proposed as possible explanationsfor copepod abundance increasing in advance of the summer peakin primary production. 相似文献