共查询到20条相似文献,搜索用时 0 毫秒
1.
Cary B. Lopez James E. Cloern Tara S. Schraga Amy J. Little Lisa V. Lucas Janet K. Thompson Jon R. Burau 《Ecosystems》2006,9(3):422-440
A presumed value of shallow-habitat enhanced pelagic productivity derives from the principle that in nutrient-rich aquatic
systems phytoplankton growth rate is controlled by light availability, which varies inversely with habitat depth. We measured
a set of biological indicators across the gradient of habitat depth within the Sacramento–San Joaquin River Delta (California)
to test the hypothesis that plankton biomass, production, and pelagic energy flow also vary systematically with habitat depth.
Results showed that phytoplankton biomass and production were only weakly related to phytoplankton growth rates whereas other
processes (transport, consumption) were important controls. Distribution of the invasive clam Corbicula fluminea was patchy, and heavily colonized habitats all supported low phytoplankton biomass and production and functioned as food
sinks. Surplus primary production in shallow, uncolonized habitats provided potential subsidies to neighboring recipient habitats.
Zooplankton in deeper habitats, where grazing exceeded phytoplankton production, were likely supported by significant fluxes
of phytoplankton biomass from connected donor habitats. Our results provide three important lessons for ecosystem science:
(a) in the absence of process measurements, derived indices provide valuable information to improve our mechanistic understanding
of ecosystem function and to benefit adaptive management strategies; (b) the benefits of some ecosystem functions are displaced
by water movements, so the value of individual habitat types can only be revealed through a regional perspective that includes
connectedness among habitats; and (c) invasive species can act as overriding controls of habitat function, adding to the uncertainty
of management outcomes. 相似文献
2.
Microzooplankton grazing can have significant impacts on the distribution and abundance of phytoplankton, thereby influencing
the frequency and duration of algae blooms. Observations of high ciliate abundances in the Suwannee River estuary, Florida,
suggest a significant potential for top-down pressure on the phytoplankton community by microzooplankton. We examined the
composition of the microzooplankton and determined grazing mortality losses for phytoplankton within the Suwannee River estuary
from 2001 to 2002. Our results indicated grazing mortality rates of 1.4 d−1, equivalent to a loss of up to 76% of phytoplankton standing crop and up to 83% of total daily primary production. The microzooplankton
community was primarily composed of ciliates, dinoflagellates, and copepod nauplii. The densities of ciliates in the estuary
were comparable to densities reported in highly eutrophic ecosystems (9,400–72,800 ciliates l−1). Grazing pressure on small phytoplankton may be further enhanced because ciliates and small dinoflagellates have growth
rates similar to those of phytoplankton, and therefore can keep up with surges in abundance.
Handling editor: Judit Padisak 相似文献
3.
Liu Zhensheng Wang Chunsheng Zhang Zhinan Cai Yuming Zhang Dongsheng 《Frontiers of Biology in China》2006,1(4):434-442
The species composition, biomass, abundance, and species diversity of zooplankton were determined for samples collected from
August 2002 to May 2003 from 14 stations in Yueqing Bay, China. Phytoplankton growth rate and microzooplankton grazing rate
were obtained by using the dilution method developed by Landry and Hassett. The spatial and temporal variations of zooplankton
and its relationship with environmental factors were also analyzed. The results showed that the zooplankton in the Yueqing
Bay could be divided into four ecotypes, namely coastal low saline species, estuary brackish water species, offshore warm
water species, and eurytopic species. A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic
larva were identified in the Yueqing Bay. The coastal low saline species was the dominant ecotype in the study area, and the
dominant species were Labidocera euchaeta, Acartia pacifica, Acrocalanus gibber, Pseudeuphausia sinica, and Sagitta bedoti among others.
There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas. The peak biomass appeared
in August, descending in November and in May, and the lowest biomass appeared in February. Similarly, the highest abundance
of zooplankton was observed in August, with the abundance descending in the following months: May, November, and February.
There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton. They both increased
from the upper to the lower bay in February and May, but decreased from the upper to the lower bay in August. Biomass and
abundance were evenly distributed in the Yueqing Bay in November. Moreover, there was marked seasonal variation in the species
diversity of zooplankton, which conformed to the abundance of zooplankton. Results of the dilution experiments indicated that
there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of
microzooplankton grazing on phytoplankton varied seasonally. Phytoplanktons were growing at 0.26–2.07/d and grazed by microzooplankton
at a rate of 0.15–0.48/d in different seasons.
__________
Translated from Acta Ecologica Sinica, 2005, 25(8): 1853–1862 [译自: 生态学报, 2005, 25(8): 1853–1862] 相似文献
4.
James E. Cloern Brian E. Cole Raymond L. J. Wong Andrea E. Alpine 《Hydrobiologia》1985,129(1):153-176
Detailed surveys throughout San Francisco Bay over an annual cycle (1980) show that seasonal variations of phytoplankton biomass, community composition, and productivity can differ markedly among estuarine habitat types. For example, in the river-dominated northern reach (Suisun Bay) phytoplankton seasonality is characterized by a prolonged summer bloom of netplanktonic diatoms that results from the accumulation of suspended particulates at the convergence of nontidal currents (i.e. where residence time is long). Here turbidity is persistently high such that phytoplankton growth and productivity are severely limited by light availability, the phytoplankton population turns over slowly, and biological processes appear to be less important mechanisms of temporal change than physical processes associated with freshwater inflow and turbulent mixing. The South Bay, in contrast, is a lagoon-type estuary less directly coupled to the influence of river discharge. Residence time is long (months) in this estuary, turbidity is lower and estimated rates of population growth are high (up to 1–2 doublings d–1), but the rapid production of phytoplankton biomass is presumably balanced by grazing losses to benthic herbivores. Exceptions occur for brief intervals (days to weeks) during spring when the water column stratifies so that algae retained in the surface layer are uncoupled from benthic grazing, and phytoplankton blooms develop. The degree of stratification varies over the neap-spring tidal cycle, so the South Bay represents an estuary where (1) biological processes (growth, grazing) and a physical process (vertical mixing) interact to cause temporal variability of phytoplankton biomass, and (2) temporal variability is highly dynamic because of the short-term variability of tides. Other mechanisms of temporal variability in estuarine phytoplankton include: zooplankton grazing, exchanges of microalgae between the sediment and water column, and horizontal dispersion which transports phytoplankton from regions of high productivity (shallows) to regions of low productivity (deep channels).Multi-year records of phytoplankton biomass show that large deviations from the typical annual cycles observed in 1980 can occur, and that interannual variability is driven by variability of annual precipitation and river discharge. Here, too, the nature of this variability differs among estuary types. Blooms occur only in the northern reach when river discharge falls within a narrow range, and the summer biomass increase was absent during years of extreme drought (1977) or years of exceptionally high discharge (1982). In South Bay, however, there is a direct relationship between phytoplankton biomass and river discharge. As discharge increases so does the buoyancy input required for density stratification, and wet years are characterized by persistent and intense spring blooms. 相似文献
5.
David F. Millie Gary L. Fahnenstiel Julianne Dyble Bressie Ryan J. Pigg Richard R. Rediske David M. Klarer Patricia A. Tester R. Wayne Litaker 《Aquatic Ecology》2009,43(4):915-934
Phytoplankton abundance and composition and the cyanotoxin, microcystin, were examined relative to environmental parameters
in western Lake Erie during late-summer (2003–2005). Spatially explicit distributions of phytoplankton occurred on an annual
basis, with the greatest chlorophyll (Chl) a concentrations occurring in waters impacted by Maumee River inflows and in Sandusky Bay. Chlorophytes, bacillariophytes,
and cyanobacteria contributed the majority of phylogenetic-group Chl a basin-wide in 2003, 2004, and 2005, respectively. Water clarity, pH, and specific conductance delineated patterns of group
Chl a, signifying that water mass movements and mixing were primary determinants of phytoplankton accumulations and distributions.
Water temperature, irradiance, and phosphorus availability delineated patterns of cyanobacterial biovolumes, suggesting that
biotic processes (most likely, resource-based competition) controlled cyanobacterial abundance and composition. Intracellular
microcystin concentrations corresponded to Microcystis abundance and environmental parameters indicative of conditions coincident with biomass accumulations. It appears that environmental
parameters regulate microcystin indirectly, via control of cyanobacterial abundance and distribution. 相似文献
6.
Dilution experiments were performed to examine the growth and grazing mortality rates of picophytoplankton (<2 μm), nanophytoplankton
(2–20 μm), and microphytoplankton (>20 μm) at stations in the Chesapeake Bay (CB), the Delaware Inland Bays (DIB) and the
Delaware Bay (DB), in early spring 2005. At station CB microphytoplankton, including chain-forming diatoms were dominant,
and the microzooplankton assemblage was mainly composed of the tintinnid Tintinnopsis beroidea. At station DIB, the dominant species were microphytoplanktonic dinoflagellates, while the microzooplankton community was
mainly composed of copepod nauplii and the oligotrich ciliate Strombidium sp. At station DB, nanophytoplankton were dominant components, and Strombidium and Tintinnopsis beroidea were the co-dominant microzooplankton. The growth rate and grazing mortality rate were 0.13–3.43 and 0.09–1.92 d−1 for the different size fractionated phytoplankton. The microzooplankton ingested 73, 171, and 49% of standing stocks, and
95, 70, and 48% of potential primary productivity for total phytoplankton at station CB, DIB, and DB respectively. The carbon
flux for total phytoplankton consumed by microzooplankton was 1224.11, 100.76, and 85.85 μg C l−1 d−1 at station CB, DIB, and DB, respectively. According to the grazing mortality rate, carbon consumption rate and carbon flux
turn over rates, microzooplankton in study area mostly preferred to graze on picophytoplankton, which was faster growing but
was lowest biomass component of the phytoplankton. The faster grazing on Fast-Growing-Low-Biomass (FGLB) phenomenon in coastal
regions is explained as a resource partitioning strategy. This quite likely argues that although microzooplankton grazes strongly
on phytoplankton in these regions, these microzooplankton grazers are passive.
Handling editor: K. Martens 相似文献
7.
Short-term changes in the photosynthetic carbon metabolism and physiological state of phytoplankton were studied over a summer fortnight-long period in the Urdaibai estuary (Bay of Biscay) and related to observed environmental patterns. Day-to-day variability in the hydrographical and biological features of the estuary during the study period was due to changes in meteorological and tidal conditions. Phytoplankton biomass and primary production increased with the improvement of weather, i.e., light conditions, during neap tides. Thus a mixed bloom of cryptophyceans, Euglena sp., and the dinoflagellate Peridinium foliaceum developed in the middle and upper estuary. Photosynthetic responses of phytoplankton were related to the time-scale of changes in light regime. Allocation of photosynthate to major macromolecular classes (LMWM, lipid, polysaccharide, and protein), like phytoplankton biomass and primary production, showed strong spatio-temporal variability. High carbon fixation into low molecular weight metabolites was associated with growth limitation by low light. The relative incorporation of photosynthetic carbon into proteins increased at the beginning of the phytoplankton bloom but overall, it was rather constant. However, carbon allocation into storage products such us lipid or polysaccharide increased when carbon and energy produced under optimal growth conditions exceeded what could be assimilated into protein. These patterns are explained by both spatio-temporal changes in the environmental conditions and species-specific differences. In general, daily variability appeared to be more important than diurnal periodicity in the physiological responses of phytoplankton. Results from this study show that phytoplankton photosynthesis and carbon metabolism are simultaneously affected by biotic and abiotic factors, although short-term light fluctuations may have a major influence on the physiological state of phytoplankton in the Urdaibai estuary. 相似文献
8.
This paper quantifies the impacts of two invasive species, Rapana venosa (Gastropoda, Muricidae) and Corbicula fluminea (Bivalvia, Corbiculidae), in the food web of the Río de la Plata estuary and adjacent nearshore oceanic ecosystem. We analyzed
certain functional traits of these mollusks assessed by a mass balance trophic model previously constructed for the years
2005–2007. This model incorporates 37 functional groups: three marine mammals species, one coastal bird, 17 fishes, 12 invertebrates,
two zooplankton, one phytoplankton, and detritus. The model also includes 5 fishing fleets operating in the area. The results
showed that the two invasive species affect multiple ecosystem components both directly and indirectly. R. venosa and the whitemouth croaker, Micropogonias furnieri, exhibited a high level of niche overlap (91%), while C. fluminea exhibited a high level of niche overlap with Mytilidae (94%), which suggests in both cases high levels of competition for
similar resources. R. venosa had mixed trophic impacts but exhibited a predominantly top down effect on most bivalves. R. venosa could be a threat to natural resources in the area including to the fishing fleets. C. fluminea negatively influenced phytoplankton and detritus biomass and its positive effects on higher trophic level groups suggest
a central bottom-up role in the food web as a bentho-pelagic coupler. Both species had negative impacts on the five fleets
modeled, showing that the effects of these invasive species could extend to the socio-economic sector. 相似文献
9.
Van Geest GJ Hessen DO Spierenburg P Dahl-Hansen GA Christensen G Faerovig PJ Brehm M Loonen MJ Van Donk E 《Oecologia》2007,153(3):653-662
A dramatic increase in the breeding population of geese has occurred over the past few decades at Svalbard. This may strongly
impact the fragile ecosystems of the Arctic tundra because many of the ultra-oligotrophic freshwater systems experience enrichment
from goose feces. We surveyed 21 shallow tundra ponds along a gradient of nutrient enrichment based on exposure to geese.
Concentrations of total phosphorus (P) and dissolved inorganic nitrogen (DIN) in the tundra ponds ranged from 2–76 to 2–23 μg l−1 respectively, yet there was no significant increase in phytoplankton biomass (measured as chlorophyll a; range: 0.6–7.3 μg l−1) along the nutrient gradient. This lack of response may be the result of the trophic structure of these ecosystems, which
consists of only a two-trophic level food chain with high biomasses of the efficient zooplankton grazer Daphnia in the absence of fish and scarcity of invertebrate predators. Our results indicate that this may cause a highly efficient
grazing control of phytoplankton in all ponds, supported by the fact that large fractions of the nutrient pools were bound
in zooplankton biomass. The median percentage of Daphnia–N and Daphnia–P content to particulate (sestonic) N and P was 338 and 3009%, respectively, which is extremely high compared to temperate
lakes. Our data suggest that Daphnia in shallow arctic ponds is heavily subsidized by major inputs of energy from other food sources (bacteria, benthic biofilm),
which may be crucial to the persistence of strong top–down control of pelagic algae by Daphnia. 相似文献
10.
Primary productivity, community respiration, chlorophyll a concentration, phytoplankton species composition, and environmental factors were compared in the Yolo Bypass floodplain and
adjacent Sacramento River in order to determine if passage of Sacramento River through floodplain habitat enhanced the quantity
and quality of phytoplankton carbon available to the aquatic food web and how primary productivity and phytoplankton species
composition in these habitats were affected by environmental conditions during the flood season. Greater net primary productivity
of Sacramento River water in the floodplain than the main river channel was associated with more frequent autotrophy and a
higher P:R ratio, chlorophyll a concentration, and phytoplankton growth efficiency (αB). Total irradiance and water temperature in the euphotic zone were positively correlated with net primary productivity in
winter and early spring but negatively correlated with net primary productivity in the late spring and early summer in the
floodplain. In contrast, net primary productivity was correlated with chlorophyll a concentration and streamflow in the Sacramento River. The flood pulse cycle was important for floodplain production because
it facilitated the accumulation of chlorophyll a and wide diameter diatom and green algal cells during the drain phase. High chlorophyll a concentration and diatom and green algal biomass enabled the floodplain to export 14–37% of the combined floodplain plus
river load of total, diatom and green algal biomass and wide diameter cells to the estuary downstream, even though it had
only 3% of the river streamflow. The study suggested the quantity and quality of riverine phytoplankton biomass available
to the aquatic food web could be enhanced by passing river water through a floodplain during the flood season. 相似文献
11.
Tadesse Dejenie Tsehaye Asmelash Luc De Meester Afework Mulugeta Abreha Gebrekidan Sarah Risch Annemie Pals Katleen Van der Gucht Wim Vyverman Jan Nyssen Jozef Deckers Steven Declerck 《Hydrobiologia》2008,610(1):193-209
The semi-arid highlands of Northern Ethiopia (Tigray) have numerous small reservoirs that have been created by microdams in
an attempt to provide water supply for irrigation and livestock drinking. Although the reservoirs have substantial added value
to residents, their use as water resource is jeopardized by eutrophication and a high occurrence of blooms of toxic cyanobacteria.
So far, there is no systematic information available on the limnological and aquatic ecological characteristics of these dams.
We carried out a standardized survey of 32 reservoirs and assessed a wide set of morphometric, abiotic and biotic variables.
The sampling was performed during two seasons, September–October 2004 (end of the wet season/start of the dry season) and
April–May 2005 (towards the end of the dry season). Using multivariate analysis, we revealed dominating patterns of variable
associations and compared the variability in these patterns among seasons. According to standardized PCA and RDA analyses,
the most important axis of variation was mainly represented by a gradient in nutrients and altitude that was also positively
associated with phytoplankton biomass, suspended matter and oxygen concentration, and negatively with water transparency.
For most variables, correlations between the wet and dry season were weak, which suggests that individual reservoirs behaved
rather differently in their response to seasonal changes. Nevertheless, a Mantel correlation (r = 0.32; P = 0.035) showed a weak but significant overall concordance in the variable association patterns among seasons. A number of
reservoirs became very shallow or fell dry in the dry season, a process that was associated with an increase in suspended
matter and conductivity and a decrease in transparency. These reservoirs contained lower amounts of fish and tended to be
less eutrophic than the deeper, permanent systems, as they had lower levels of phosphorus and chlorophyll-a. With multiple regression analysis, we constructed most parsimonious models in an attempt to explain the variation in key
biotic variables: phytoplankton and cyanobacteria biomass, cladoceran biomass, fish biomass and the abundance of submerged
vegetation. Phytoplankton and fish biomass tended to be positively related with the concentration of total phosphorus, whereas
cladoceran biomass was not associated with nutrient concentrations. The positive association of fish and phytoplankton with
nutrient concentrations suggests a bottom-up control, whereas the absence of an association between zooplankton and nutrient
concentrations may be indicative for top-down control. The biomass of cyanobacteria was negatively related to the biomass
of cladocerans (Daphnia), which likely reflects a top-down effect. Most reservoirs were turbid. The occurrence and abundance of macrophytes tended
to be positively related to water transparency and was negatively associated to TP and the amount of livestock frequenting
the reservoirs. However, macrophytes were not limited to clear-water reservoirs.
Handling editor: L. M. Bini 相似文献
12.
We investigated phytoplankton biomass, assemblage structure and production along an environmental gradient to evaluate if
chlorophyll-a (as proxy for biomass) and primary production peaked under conditions hypothesised to favour phytoplankton growth. During
Spring 2003, a wide area from shallow estuarine waters to the shelf slope off the Río de la Plata was sampled and routine
measurements included CTD profiles, nutrients, chlorophyll-a, phytoplankton composition and abundance, seston and organic matter loads, downwelling light and, at selected stations, production
versus irradiance experiments. Spatial differences in abiotic variables suggested distinct hydrographic zones that differed
in phytoplankton biomass and productivity. Chlorophyll-a was highest under estuarine influence and peaked at low salinity when strong stratification developed in the outer estuary,
and was minimum at the shelf break and slope. In that area, however, relatively high chlorophyll-a was associated to oceanographic fronts and to the occurrence of Sub Antarctic water within the photic depth range. Productivity
was maximum in shallow waters, but biomass-specific productivity peaked at the outer shelf in oceanographic fronts or in upwelled
Sub Antarctic waters. Over shelf and slope waters productivity and biomass were not tightly coupled, as indicated by situations
of high biomass and low productivity (Station 9), low biomass and high productivity (Station 10), or both high biomass and
productivity (Station 22). Ordination analysis of phytoplankton taxa suggested that assemblages changed gradually along the
environmental gradient and correlated to abiotic variables defining geographic zones. Overall results were consistent with
an interpretation that phytoplankton biomass and growth were modulated by light in estuarine and coastal waters, and by hydrographic
processes on the continental shelf and slope.
Handling editor: Luigi Naselli-Flores 相似文献
13.
Low algal biomasses and high water transparencies are a feature of the storage reservoirs that supply most of London's treated
water. This is a result of knowledgeable limnological management and biomanipulation and despite the eutrophic nature of the
River Thames with its high nutrients (7 gN m−3; 1 gP m−3) and particulate organic carbon (2 gC m−3). Built-in possibilities of jetting input water are managed to prevent stratification, to ensure isothermy, to mix chemicals
and plankton vertically and horizontally and to manipulate the mixed-depth of the algal populations such that their potential
for biomass growth is reduced by light-energy limitation. Spring algal growth is delayed and the spring peak is reduced and
curtailed by the grazing impact of considerable biomasses of large-bodied daphnid populations (Daphnia magna, pulicaria & hyalina) whose development is also supported by the continuous input of high riverine algal crops. The existence of a large-bodied
daphnid zooplankton in the reservoirs is associated with low levels of fish predation since the late 1960s. Variations in
the intensity and nature of this vertebrate predation during the subsequent twenty years (1968–88) are illustrated by the
changes that have occurred in the relationship between the phytoplankton and zooplankton biomasses of the April-May-June quarter
of the year. This example of the London reservoirs serves to illustrate biomanipulation in deep water bodies by bottom-up
as well as top-down effects. 相似文献
14.
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
15.
The phytoplankton community of the River Meuse,Belgium: seasonal dynamics (year 1992) and the possible incidence of zooplankton grazing 总被引:7,自引:7,他引:0
Qualitative and quantitative aspects of the phytoplankton of the River Meuse were studied during 1992, at a point 537 km from the source. The phytoplankton was dominated by diatoms and green algae. The Stephanodiscus hantzschii-group was especially prominent. Other important taxa were Cyclotella meneghiniana, small Cyclotella and Thalassiosira, Aulacoseira ambigua and Nitzschia acicularis. Cell abundances varied from less than 1000 units ml–1 to about 25 000 – 30 000 units ml–1 during the blooms. The Stephanodiscus hantzchii-group constituted almost entirely the first spring bloom. During the summer period, small Thalassiosiraceae developed markedly and large Thalassiosira weissflogii appeared. During this period, green algae dominated diatoms as expressed in cell abundances. The main Chlorococcales were Scenedesmus quadricauda, Scenedesmus div. sp., Dictyosphaerium ehrenbergianum and Pediastrum duplex. Dinophyceae contributed a significant biomass during the summer period. Total biomass varied between 100 and 3 650 µg Cl–1. As previously observed (Descy, 1987), the factors regulating the phytoplankton growth were clearly physical variables: discharge, temperature and irradiance. However, in the summer period, low abundances might indicate a regulation by biotic factors. The impact of grazing by zooplankton is discussed, on the basis of observations of zooplankton development in the River Meuse and on the basis of simulation by a mathematical model. A comparison is carried out with recent data of phytoplankton in large European rivers. 相似文献
16.
Climatic and biotic extreme events moderate long‐term responses of above‐ and belowground sub‐Arctic heathland communities to climate change
下载免费PDF全文
![点击此处可从《Global Change Biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stef Bokhorst Gareth K. Phoenix Matty P. Berg Terry V. Callaghan Christopher Kirby‐Lambert Jarle W. Bjerke 《Global Change Biology》2015,21(11):4063-4075
Climate change impacts are not uniform across the Arctic region because interacting factors causes large variations in local ecosystem change. Extreme climatic events and population cycles of herbivores occur simultaneously against a background of gradual climate warming trends and can redirect ecosystem change along routes that are difficult to predict. Here, we present the results from sub‐Arctic heath vegetation and its belowground micro‐arthropod community in response to the two main drivers of vegetation damage in this region: extreme winter warming events and subsequent outbreaks of the defoliating autumnal moth caterpillar (Epirrita autumnata). Evergreen dwarf shrub biomass decreased (30%) following extreme winter warming events and again by moth caterpillar grazing. Deciduous shrubs that were previously exposed to an extreme winter warming event were not affected by the moth caterpillar grazing, while those that were not exposed to warming events (control plots) showed reduced (23%) biomass from grazing. Cryptogam cover increased irrespective of grazing or winter warming events. Micro‐arthropods declined (46%) following winter warming but did not respond to changes in plant community. Extreme winter warming and caterpillar grazing suppressed the CO2 fluxes of the ecosystem. Evergreen dwarf shrubs are disadvantaged in a future sub‐Arctic with more stochastic climatic and biotic events. Given that summer warming may further benefit deciduous over evergreen shrubs, event and trend climate change may both act against evergreen shrubs and the ecosystem functions they provide. This is of particular concern given that Arctic heath vegetation is typically dominated by evergreen shrubs. Other components of the vegetation showed variable responses to abiotic and biotic events, and their interaction indicates that sub‐Arctic vegetation response to multiple pressures is not easy to predict from single‐factor responses. Therefore, while biotic and climatic events may have clear impacts, more work is needed to understand their net effect on Arctic ecosystems. 相似文献
17.
Rayanne Barros Setubal Ana Cristina Petry Cláudia Costa Bonecker Thiago Martins Clarice Casa Nova Marcos Paulo Figueiredo-Barros Reinaldo Luiz Bozelli 《Freshwater Biology》2020,65(8):1376-1391
- The interest in understanding ecosystem functioning has grown in recent years due to the effects of species loss on ecosystem processes. Even though biotic and abiotic factors control ecosystem processes, their relative influence may vary according to ecosystem dynamics. In flood and coastal plains, these dynamics are mainly represented by flood pulses and hydroregime, respectively. The objective of this study was to investigate the importance of abiotic and biotic factors for the ecosystem processes represented by zooplankton secondary production (SP), biomass (ZB), and resource use efficiency (RUE) in lentic waterbodies subjected to different hydrological regimes. We hypothesised that abiotic factors would more strongly determine the ecosystem processes in temporary waterbodies and floodplain lakes, given their greater susceptibility to environmental changes. Biotic factors would be more relevant in coastal lagoons due to their greater temporal stability.
- Sampling was undertaken quarterly over 1 year in eight coastal lagoons, 10 temporary ponds and five floodplain lakes. The environments were characterised in relation to limnological variables, and zooplankton functional divergence, functional dispersion (FDis), functional evenness, functional richness, and taxonomic richness were measured. Analysis of variance (ANOVA) was used to verify seasonal changes in SP, ZB, RUE, functional diversity, richness, and abiotic factors. Linear mixed models were used to determine which abiotic and biotic factors were the most important for ZB, SP, and RUE.
- In the coastal lagoons, RUE differed over time. In the temporary ponds and floodplain lakes, no seasonal significant differences were observed for any of the zooplankton production variables. The linear mixed model analyses showed that models composed mainly of biotic factors were better fitted to the production variables. For coastal lagoons, phytoplankton density affected ZB, SP, and RUE increasing them by 9.9 mg DW/m3, 12.4 mg DW/m3, and 1.23, respectively. For temporary ponds, FDis lowered ZB by 6.9 mg DW/m3 and taxonomic richness increased SP and RUE by 14.2 mg DW/m3 and 1.17, respectively. For floodplain lakes, FDis lowered ZB it by 9.9 mg DW/m3 and functional divergence lowered RUE by 0.81.
- The present study demonstrates that biotic factors are the main determinants of ecosystem processes in neotropical lentic waterbodies, irrespective of their annual hydrological regimes. Complementarity effects and high functional diversity are more important in more stable environments, whereas redundancy and low functional diversity prevail in environments subject to more frequent environmental changes. Biotic factors play a major role in ensuring the functioning of aquatic ecosystems and indicate the important role of biodiversity in enabling ecosystem states to be maintained after disturbances and to prevent changes in ecosystem processes.
18.
Effects of saltmarsh invasion by Spartina alterniflora on arthropod community structure and diets 总被引:1,自引:0,他引:1
Yu-Tong Wu Cheng-Huan Wang Xiao-Dong Zhang Bin Zhao Li-Fen Jiang Jia-Kuan Chen Bo Li 《Biological invasions》2009,11(3):635-649
Invasive plants strongly affect physical and biotic environments of native ecosystems. Insects and other arthropods as one
of the major components of many ecosystems are very sensitive to subtle changes in abiotic and biotic environments. We examined
the effects of exotic Spartina alterniflora invasion on community structure and diets of arthropods in a saltmarsh previously dominated by native Phragmites australis in Yangtze River estuary through net sweeping and plant harvesting methods and stable isotope analysis. Our results showed
that diversity indices were not significantly different between exotic and native plant communities, but the total abundance
of insects estimated through plant harvesting method was found to be lower in Spartina monoculture than that in Phragmites monoculture. Community structure of insects in Spartina monoculture was dissimilar to that in Phragmites monoculture and Phragmites–Spartina mixture. Moreover, stable carbon isotope patterns of arthropods were significantly different between Phragmites and Spartina monocultures. Although some native arthropods (perhaps generalists) shifted their diets, many native taxa did prefer Phragmites to Spartina even in Spartina monoculture. Spartina invasions resulted in reduced abundances of some arthropds, and increased dominance of others feeding preferably on Spartina. This study provides evidence that invasive plants can change the community structure and diets of native arthropods, which
will eventually alter the arthropod food web, and affect the integrity and functioning of native ecosystems within a nature
reserve that has been set aside for conserving the native biodiversity and maintaining the ecosystem integrity. In this sense,
Spartina invasions in the Yangtze River estuary need to be managed appropriately. 相似文献
19.
Yoko Nishimura Taisuke Ohtsuka Kohei Yoshiyama Daisuke Nakai Fujiyoshi Shibahara Masayoshi Maehata 《Ecological Research》2011,26(3):615-626
Effects of fish predation propagate through aquatic food webs, where the classical grazing food chain and microbial loop are
interwoven by trophic interactions. The overall impact on aquatic food webs is further complicated because fish may also exert
bottom-up controls through nutrient regeneration. Yet, we still have limited information about cascading effects among fish,
zooplankton, phytoplankton, and microbes. In this study, we performed a mesocosm experiment to evaluate effects of fish introduction
on plankton communities. Six plots were set in factorial combination with fish introduction and rice straw plowing in a paddy
field, and the experiment was continued for 4 weeks. Introduction of fish significantly increased chlorophyll a concentrations in smaller size fractions (<15 μm) and abundances of filamentous bacteria (>5 μm in length) and heterotrophic
nanoflagellates in 3–15 μm fraction. Microbes in 0.8–3 μm fraction showed increasing but not significant trends in response
to fish introduction. These results indicate cascading effects of fish predation operating via two pathways, one through grazing
food chain and the other through microbial food web. Phytoplankton community compositions shifted in similar fashion in all
plots until 1 week after fish introduction, and then diverged between plots with and without fish thereafter. Bottom-up effects
of fish introduction were suggested by increases of total chlorophyll a and inedible phytoplankton species in response to fish introduction. This study provides an example of how fish predation
regulates biomass and structure of phytoplankton and microbial communities. 相似文献
20.
Julian D. Olden 《Hydrobiologia》2000,436(1-3):131-143
Artificial neural networks are used to model phytoplankton succession and gain insight into the relative strengths of bottom-up and top-down forces shaping seasonal patterns in phytoplankton biomass and community composition. Model comparisons indicate that patterns in chlorophyll aconcentrations response instantaneously to patterns in nutrient concentrations (phosphorous (P), nitrite and nitrate (NO2/NO3–N) and ammonium (NH4–H) concentrations) and zooplankton biomass (daphnid cladocera and copepoda biomass); whereas lagged responses in an index of algal community composition are evident. A randomization approach to neural networks is employed to reveal individual and interacting contributions of nutrient concentrations and zooplankton biomass to predictions of phytoplankton biomass and community composition. The results show that patterns in chlorophyll aconcentrations are directly associated with P, NO2/NO3–N and daphnid cladocera biomass, as well as related to interactions between daphnid cladocera biomass, and NO2/NO3–N and P. Similarly, patterns in phytoplankton community composition are associated with NO2/NO3–N and daphnid cladocera biomass; however show contrasting patterns in nutrient– zooplankton and zooplankton–zooplankton interactions. Together, the results provide correlative evidence for the importance of nutrient limitation, zooplankton grazing and nutrient regeneration in shaping phytoplankton community dynamics. This study shows that artificial neural networks can provide a powerful tool for studying phytoplankton succession by aiding in the quantification and interpretation of the individual and interacting contributions of nutrient limitation and zooplankton herbivory on phytoplankton biomass and community composition under natural conditions. 相似文献