Community structure and food web based on stable isotopes (δN and δC) analysis of a North Eastern Atlantic maerl bed

Maerl beds are highly biodiverse biogenic substrata that have been receiving increasing attention in the last decade. Although maerl beds represent important nursery areas for commercial fishes and molluscs, little is known on the trophic web of their communities. Community structure parameters of maerl bed of the Bay of Brest (species richness, abundance, biomass and dominating species) were studied in parallel with the carbon and nitrogen isotopic composition of their main benthic species (macrofaunal, and megafaunal organisms) in order to assess the trophic levels and differences in the potential food sources of maerl inhabitants. The major potential sources of energy were identified to originate either from epiphytic macroalgae and microphytobenthos both growing on maerl thalli, together with sedimenting (sedimentary) particulate organic matter (POM) originating from the water column. The majority of the macro- and megafaunal organisms investigated were filter feeders, selective-deposit feeders and predators/scavengers. Filter feeders fall into three different groups representing different trophic pathways (i) sponges feeding directly on POM (water column filter feeders I), (ii) ascidians and holothurians feeding on POM and probably captured pelagic preys (water column filter feeders II), and (iii) filter feeding molluscs and crustaceans were hypothesised to feed on microphytobenthos or on decaying sedimented POM (Interface filter feeders). Selective deposit feeders were also divided into two subgroups. Carnivores were also distinguished between those with scavenging habits and true predators. Coupling of the trophic levels observed with the community biomass structure revealed that most of the benthic biomass derives its food from detritic sedimented POM and/or microphytobenthos, with interface filter feeders (23% of the biomass), selective deposit feeders (12%). Carnivores made up to 14% of the total biomass. Generally stable isotopes ratio mean values overlap and cover a large range within feeding types, indicating a strong overlap in food sources and a high degree of complexity of the food web presumably due to the diversity of the potential food sources.     

Trophic structure of macrobenthos in the Tagus estuary and adjacent coastal shelf

The trophic structure of benthic communities in the Tagus estuary and adjacent coastal shelf was characterized according to a functional guild approach, based on sampling surveys conducted between 1987 and 2000. Macrobenthic organisms were assigned to seven distinct trophic groups (herbivorous, filter feeders, surface deposit feeders, subsurface deposit feeders, carnivores, filter feeders/detritivores, carnivores/detritivores) and the dominance of these groups was related to environmental variables using multivariate ordination techniques. Surface-deposit feeders were numerically dominant in the Tagus estuary, making up 52% of the benthic communities, while in the adjacent coastal shelf the assemblage was dominated by both surface-deposit feeders and filter feeders (37% and 33%, respectively). When biomass was considered, filter feeders and filter feeders/detritivores were the dominant groups in the estuary, while for the adjacent coastal shelf filter feeders represented 83% of the total biomass. Salinity, depth and sediment composition were the main factors structuring spatial distribution. Surface-deposit feeders were the most abundant macrobenthos of the upper estuary. Surface deposit feeders also dominated the middle and the lower estuary but the proportion of filter feeders as well as other trophic groups increased with salinity. Generally, a more even distribution of trophic structure was found at stations with high salinity. In the adjacent coastal shelf, the trophic diversity decreased with depth. The trophic structure revealed that filter feeders dominated in abundance and biomass in shallow sandy sediments (<25 m), while in deeper sandy mud and muddy habitats (>50 m to 260 m), deposit feeders and carnivores were the most important groups in abundance and biomass, respectively.     

Effects of Metazoan Predators on Ciliates in Freshwater Plankton Communities1

ABSTRACT. Ciliates are often important members of aquatic communities in terms of their biomass, productivity, trophic roles, or numerical abundance. The interaction of metazoan predators with ciliates will be mediated by a number of biotic factors, including the potential of ciliate populations for growth, the relative size of ciliates and metazooplankton, the species structure of the metazooplankton, and the defenses of ciliates. This paper reviews some of the recent laboratory an field data pertaining to these particular factor. Studies have generally shown that metazoans can reduce ciliate population growth rates, but this impact varies greatly with the ciliate and metazoans involved. Smaller ciliates are generally more vulnerable to metazoan predators than larger species, although this relationship will be affected by the defenses a ciliate may possess. The structure of the metazooplankton community itself will also affect ciliatemetazoan interactions. The suppression of ciliate populations by metazoans has important ecological consequences, and more study is needed to understand the interaction of these groups in aquatic systems.     

Population Dynamics of the Polychaetous Annelids of an Intertidal Habitat in Upper Old Tampa Bay,Florida

Following an extensive red-tide induced mass mortality of the benthic macrofauna of a sandy intertidal habitat, the population dynamics of the polychaete species were studied. Detailed studies of the 12 most abundant species are presented. Data concerning total population levels, reproduction, recruitment, distribution within the intertidal zone, and gut content analyses are integrated in order to explain the observed spatial and temporal patterns of distribution and abundance. Potential competive interactions for food are considered to be the most important factor for explaining the observed ecological patterns. The polychaete species studied are divided into three trophic guilds: an omnivorous guild that feeds predaciously and as non-selective deposit feeders, a surface feeding guild consisting of species usually considered to be selective surface deposit feeders, and a subsurface feeding guild usually considered as non-selective infaunal deposit feeders. Within and between guild interactions are discussed.     

Trends in estuarine fish assemblages facing different environmental conditions: combining diversity with functional attributes

Changes in the Mondego estuary (Portugal) fish assemblage were documented with a long-term monitoring program between June 2003 and March 2010, during which several extreme environmental events occurred, including severe droughts and heavy precipitation. The structure and composition of the fish assemblage was analyzed based on a set of indicators: dominance, diversity, evenness, and composition in functional groups (ecological and feeding guilds). Higher species number, diversity, and evenness were observed in the dry periods. Variations in the relative abundance of the ecological guilds were also observed: in dry years, estuarine residents were the most abundant group, while in typical and rainy years, the marine estuarine-dependent species increased in abundance. Among the feeding guilds, the most abundant group was the invertebrate and fish feeders. Planktivorous and invertebrate feeders occurred in higher abundance in dry years, while the opposite was verified for omnivorous species. The mean trophic level of the fish assemblage increased during the drought period, constantly decreasing afterward, which could be attributed to an increase in predators in dry years. The cumulative responses of estuarine fish assemblages to ongoing climate changes and discrete extreme weather events confirm their importance as indicators of environmental changes.     

Abundance and trophic structure of pine forest nematodes in relation to soil layers and ground cover

In a 15-20 yr old forest of Scots pine, the total number of nematodes under the dominating cover grass Deschampsia flexuosa , reached 4.0–4.7 × 10⁶ ind. m⁻² stone free soil, corresponding to densities of 8770–9090 and 3500–3790 ind. 100 ml⁻¹ in FH and mineral soil, respectively. Root/fungal feeding nematodes formed 53–59% of the total nematode fauna. The majority in this group was potential mycophages. Obligate root feeders formed only 11–17% of the total number of nematodes. Soil layers and ground cover affected the abundance of trophic groups. Bacterial feeders, potential mycophages and miscellaneous feeders reached their maximal abundance in the FH-layer. Obligate root feeders tended to reach higher densities in the mineral soil. Higher abundance values of most trophic groups were found under forest grass. The species Calamagrostis arundinacea had a striking positive effect on the relative and absolute abundance of obligate root feeders. This group may be most numerous in early stages of forest development.     

Ciliate community structure, diversity and trophic role in offshore sediments from the Yellow Sea

We investigated the community structure, diversity and trophic role of ciliates in the sediments from 48 stations in the Yellow Sea using Ludox density centrifugation and quantitative protargol stain. The ciliate abundance ranged from 1 to 221cellscm(-3) and biomass from 0.0001 to 0.47μgCcm(-3) in the upper 8cm of the sediments. On average, 77% of ciliate abundance and 81% of biomass were distributed in the 0-2cm sediment layers, while the respective proportions were only about 6% and 3% in the 5-8-cm layers. Among the 198 morphospecies, Prostomatea was the most dominant group accounting for 45% of the total abundance and 58% of the total biomass. Carnivorous ciliates constituted the primary feeding type, occupying about 64% of the total biomass, followed by bacterivores (21%), algivores (12%) and omnivores (3%). The ciliate abundance and biomass in the upper 5cm of sediments were two orders of magnitude higher than those in the upper 10m of the Yellow Sea water column. The estimated ciliate bacterivory and herbivory indicate that ciliate ingestion had little direct influence on bacterial standing stock but possibly had an important impact on diatoms in the sediments from the Yellow Sea.     

夏季蓝藻水华期间太湖河口区和敞水区纤毛虫群落组成及水平分布

在太湖北部主要河口区及敞水区域采集纤毛虫样品, 并用定量蛋白银法进行分析。河口区设10个采样点, 敞水区设14个采样点。调查中共检出3纲15目60属的105种纤毛虫, 种类最多的是钩刺目（21种）, 其次是寡毛目（20种）。纤毛虫优势种及其在河口区和敞水区占总丰度比例分别为: 寡毛目的双叉弹跳虫Halteria bifurcate Tamar （12.3%、18.1%）、大弹跳虫H. grandinella Dujardin （12.3%、10.9%）、短列裂隙虫Rimostrombidium brachykinetum Krainer （8.0%、13.4%）、圆筒状似铃壳虫Tintinnopsis cylindrata Kofoid Campbell （11.8%、4.5%）、盾纤目的银灰膜袋虫Cyclidium glaucoma Mller （3.1%、10.8%）。其他常见种类还有: 前口目的趣尾毛虫Urotricha farcta Claparde Lachmann、寡毛目的杯铃壳虫Codonella cratera Leidy、小裂隙虫R. humile Penard、奇异急游虫Strombidium mirabile Penard、小筒壳虫Tintinnidium pusillum Entz、缘毛目的水生钟虫复合种Vorticella aquadulcis complex和钟形钟虫V. campanula Ehrenberg。河口区和敞水区纤毛虫平均丰度分别为31407 cells/L（范围1 600-80 900 cells/L）和18618 cells/L（范围1225 -36000 cells/L）, 平均生物量分别为1322.6 g/L（范围44.6-3119.7 g/L）和543.6 g/L（范围44.0-1570.4 g/L）。两个区域的优势类群相似, 均以寡毛目、前口目、盾纤目和缘毛目为主。但河口区纤毛虫生物多样性（种类丰富度、Simpson多样性指数、Margalef多样性指数、Shannon多样性指数）显著高于敞水区的（P0.05）。统计分析发现, 食藻种类与叶绿素a含量之间无显著相关, 而食菌种类的丰度和叶绿素a含量呈显著正相关关系（P0.001）。由此推测, 纤毛虫群落结构的空间差异可能与水华暴发程度有较大关系。       

Aquatic arthropod communities in Nepenthes pitchers: the role of niche differentiation,aggregation, predation and competition in community organization

Summary The structure and organization of aquatic arthropod communities in Nepenthes ampullaria pitchers were studied at two sites (M in Malacca and K in Kuching) in Malaysia. The communities consisted mainly of aquatic dipteran larvae. Community M was dominated by a filter feeder, Tripteroides tenax, which reached a high density despite a strongly aggregated distribution. Community K had five trophic groups: carrion feeders, filter feeders, detritus feeders, nipping predators and hooking predators, each including multiple species. The summed density of filter feeders in Community K remained much below the level attained by filter feeders in Community M. Niche differentiation within each trophic group with regard to pitcher age and feeding behaviour was not sufficient to allow species coexistence through niche separation alone. Aggregated distributions directly reduced interspecific encounters. Nevertheless, species belonging to the same trophic group commonly shared the same pitcher, because of high occurrence probabilities of dominant species and positive associations between some taxa (due mainly to similar occupancies by pitcher age). Predator coexistence in Community K may have been facilitated by self-limitation of the large predators through intraspecific cannibalism strengthened by aggregation. Prey coexistence, on the other hand, may have relied more on population suppression by predation, especially the selective removal of old instar Tripteroides.     

Evaluation of double formalin--Lugol's fixation in assessing number and biomass of ciliates: an example of estimations at mesoscale in NE Atlantic

Ciliated protozoa are potential grazers of primary and bacterial production and act as intermediaries between picoplankton and copepods and other large suspension feeders. Accurate determination of ciliate abundance and feeding mode is crucial in oceanic carbon budget estimations. However, the impact of different fixatives on the abundance and cell volume of ciliates has been investigated in only a few studies using either laboratory cultures or natural populations. Lugol's solution and formalin are the most commonly used fixatives for the preservation of ciliates samples. In the present study, the aim was to compare 0.4% Lugol's solution and 2% borated-formalin fixation and evaluate the need of counting duplicate samples each using a different fixative. For this, a large number of samples (n = 110) from the NE Atlantic was analyzed in the frame of POMME program (Multidisciplinary Mesoscale Ocean Program). We established a statistically significant relationship (p < 0.0001) between Lugol's and formalin fixed samples for both abundance (r2 = 0.50) and biomass (r2 = 0.76) of aloricate ciliates which showed that counts were higher in Lugol's solution by a factor of 2 and a non-taxon specific cell-loss in formalin. However, loricate ciliate abundance in our samples which were represented primarily by Tintinnus spp. did not show any difference between the two treatments. Abundance and biomass of mixotrophic ciliates (chloroplast-bearing cells) were for various reasons underestimated in both treatments. Our results show that unique fixation by formalin may severely underestimate ciliates abundance and biomass although their population may not alter. For this reason, Lugol's solution is best for the estimation of their abundance and biomass. However, for counts of mixotrophs and the evaluation of the ecological role of ciliates in carbon flux, double fixation is essential. Compromises regarding the fixatives have lead to severe underestimations of mixotrophs in studies conducted by now.     

Mosquito control actions affect chironomid diversity in temporary wetlands of the Upper Rhine Valley

The Upper Rhine Valley, a “hotspot of biodiversity” in Germany, has been treated with the biocide Bacillus thuringiensis var. israelensis (Bti) for mosquito control for decades. Previous studies discovered Bti nontarget effects in terms of severe chironomid abundance reductions. In this study, we investigated the impact of Bti on species level and addressed the community composition of the nontarget family Chironomidae by use of community metabarcoding. Chironomid emergence data were collected in three mosquito‐control relevant wetland types in the Upper Rhine Valley. For all three sites the chironomid species composition, based on operational taxonomic units (OTUs), was different to varying degrees in the Bti‐treated samples versus control samples, ranging from a significant 63% OTU reduction to an OTU replacement. We assumed that predatory chironomids are less prone to Bti than filter feeders, as the latter feed on floating particles leading to direct ingestion of Bti. However, a comparable percentage of predators and filter feeders (63% and 65%, respectively) was reduced in the Bti samples, suggesting that the feeding strategy is not the main driver for Bti sensitivity in chironomids. Finally, our data was compared to a three‐year‐old data set, indicating possible chironomid community recovery due to species recolonization a few years after the last Bti application. Considering the currently discussed worldwide insect decline we recommend a rethinking of the usage of the biocide Bti, and to prevent its ongoing application especially in nature protection reserves to enhance ecological resilience and to prevent boosting the current biodiversity loss.     

Distributions and Biomass of Benthic Ciliates,Foraminifera and Amoeboid Protists in Marine,Brackish, and Freshwater Sediments

The quantitative importance of ciliates, foraminifers, and amoebae was investigated in marine, brackish, and freshwater sediments from 15 littoral stations. Total protozoan communities were usually dominated by ciliates in term of abundance, while amoebae often dominated in terms of biomass. Applying the biomass‐metabolic rate equation, ciliates, amoebae, and foraminifera were estimated to contribute 66% of the total abundance and 33% of the biomass, but up to 55% of the combined metabolic rate to the micro‐ and meiobenthos in the 15 sediments. Statistical analyses using ciliate data demonstrated: (1) species composition and community structures represented significant differences between freshwater and marine/brackish sediments, and subsequently between temperate and arctic sampling sites; (2) the occurrence of dominant ciliates and their allocation to feeding types indicated that herbivory was the most common feeding strategy in these sediments; (3) multivariate analyses showed all of the tested environmental factors (temperature, salinity, silt/clay, carbon, nitrogen, and chlorophyll a) to be important to varying degrees, but especially the combination of salinity, temperature, and silt/clay. Multiple factor effects or comprehensive influences might be important in regulating the distribution of protozoa in sediments. The importance of protozoa in sediment systems and the potential ecological significance of cysts are discussed.     

Cascading trophic effects in pampean shallow lakes: results of a mesocosm experiment using two coexisting fish species with different feeding strategies

Planktivorous fish, both visual predators and filter feeders, enhance eutrophication processes in lakes. In pampean shallow lakes several planktivorous species may coexist but often two species dominate: silverside (Odontesthes bonariensis), a visual planktivorous fish when young adult, and sabalito (Cyphocharax voga), an omnivorous filter feeder. To assess the relative strength of the cascading trophic effects of the two species, a mesocosm experiment was conducted using different proportions of both species as treatments. Differences were found in water transparency, phytoplankton biomass, crustacean abundance, individual size and biomass. Our results suggest that visual predators intensify eutrophication effects more strongly than filter feeders do.     

Arthropod community structure along a latitudinal gradient: Implications for future impacts of climate change

Abstract The structure of free‐living arthropod communities on the foliage of Acacia falcata was assessed along an extensive latitudinal gradient in eastern Australia. We hypothesized that abundance and biomass of arthropods within feeding groups would increase from temperate latitudes towards the tropics. We also hypothesized that the ratio of carnivores to herbivores would be consistent along the latitudinal gradient. Three sites at each of four latitudes, spanning 9° and 1150 km (Batemans Bay, Sydney, Grafton, Gympie in Australia), were sampled every season for 2 years, using pyrethrum knockdown. Abundance and biomass (based on dry weight) of arthropods within eight feeding groups were measured. The relative size of the feeding groups, and the ratio of carnivores to herbivores were then compared among latitudes and seasons. We found no consistent north to south (tropical to temperate) change in feeding group structure in terms of abundance. A weak latitudinal trend was evident for predator biomass, consisting of a reduction from north to south, but no significant trends in biomass for other feeding groups were found. Relative abundance and relative biomass of both carnivores and herbivores, as well as the ratio of carnivores to herbivores were consistent among latitudes. Finally, we compared a subset of these data to arthropod communities found on congeneric host species at individual sites along the latitudinal gradient. Overall, 68% of comparisons showed no significant differences in abundance or biomass within different feeding groups between host plants and among latitudes. We conclude that arthropod communities show consistencies among latitudes and between congeneric host species, in terms of feeding group and trophic structure. These results have implications for predicting the impacts of future climate change on arthropod communities.     

The invertebrate fauna on broom,Cytisus scoparius,in two native and two exotic habitats

This study quantifies the invertebrate fauna found on broom, Cytisus scoparius, L. (Link), in two countries where it grows as a native plant (France and England) and two countries where it grows as an alien plant (New Zealand and Australia). The data are used to test three hypotheses concerning the predicted differences in invertebrate community structure in native versus exotic habitats: (1) Are generalist phytophages dominant in exotic habitats and specialist phytophages dominant in native habitats? (2) Are there empty phytophage niches in exotic habitats? (3) As a plant species accumulates phytophages, do these in turn accumulate natural enemies? The broom fauna was sampled at five sites in each country by beating five broom bushes per site. The sampling efficiency of beating was quantified at one field site and it was shown to collect 87 % of invertebrate abundance, 95 % of invertebrate biomass and 100 % of phytophagous species found on the branches. Generalist phytophages were dominant on broom in exotic habitats and specialists dominant on broom in the native habitats. Thus, the two countries where broom grows as a native plant had higher numbers of total phytophage species and a higher abundance of specialist phytophages per bush. There was no significant difference in the average abundance of generalist phytophage species found per bush in native and alien habitats. Phytophages were assigned to seven feeding niches: suckers, root feeders, external chewers, flower feeders, seed feeders, miners and pollen feeders. Empty niches were found in the exotic habitats; species exploiting structurally specific parts of the host plant, such as flowers and seeds, were absent in the countries where broom grows as an alien plant. The pattern of niche occupancy was similar between native and exotic habitats when just the generalist phytophages were considered. As phytophage abundance and biomass increased, there were concomitant increases in natural enemy abundance and biomass. Thus, it appears that as plants accumulate phytophages, the phytophages in turn accumulate natural enemies and a food web develops around the plant. Moreover, in the native countries, the history of association between the natural enemies and their prey has been sufficient for specialist predators and parasitoids, feeding on the specialist phytophages, to have evolved.     

Food webs in tropical Australian streams: shredders are not scarce

1. Macroinvertebrates were collected in dry and wet seasons from riffles and pools in two streams in tropical north Queensland. Total biomass, abundance and species richness were higher in riffles than in pools but did not differ between streams or seasons. 2. Gut contents of all species were identified. Cluster analysis based on gut contents identified five dietary groups: I, generalist collectors; II, generalist shredders and generalist predators; III, generalist scrapers; IV, specialist shredders; and V, specialist predators. Species were allocated to functional feeding groups (FFGs) based on these dietary groups. 3. Many species were generalist in their diets, but specialist predators and shredders were particularly prominent components of the invertebrate assemblages in terms of biomass and species richness. 4. Community composition (proportions of biomass, abundance and species richness of the different FFGs) varied between habitat types, but not between streams or seasons, although differences between riffles and pools varied with season. 5. Comparison of the fauna of 20 streams showed that our study sites were similar to, or not atypical of, low‐order streams in the Queensland wet tropics.     

Analysis of the community structure of planktonic ciliated protozoa relative to trophic state in Florida lakes

The planktonic ciliate populations of 30 Florida lakes constituting a broad trophic gradient were examined to determine the response of protozoan community structure to increasing eutrophication. Both ciliate abundance and biomass were strongly related to lake trophic state. Comparison of the Florida data base with a comparable north temperate lake group indicated that subtropical lakes generally possess higher ciliate abundance and biomass at a given trophic state than temperate lakes. However the equations derived for each data base were not significantly different. Community diversity and species richness increased with increasing lake productivity. Highly acidic lakes displayed significantly reduced diversity and numbers of species when contrasted with nonacidic oligotrophic lakes. Small-bodied (< 30 um) ciliates dominated all lakes but were proportionally less important in oligotrophic lakes. Presence-absence data produced three assemblages: an ubiquitous association of primarily small ciliate taxa, a group of large ciliates mainly restricted to eutrophic-hypereutrophic lakes, and a very large ciliate,Stentor niger, which dominated the protozoan communities of acidic oligotrophic lakes.     

Biotopstruktur und Besiedlungsstruktur

This paper offers a discussion of the following approaches which are considered important for an understanding of the structure of marine benthic communities. 1. Patterns of horizontal distribution. By applying statistical methods, e. g. the calculation of a coefficient of dispersion, the pattern of horizontal distribution of species within a habitat can be represented more realistically than by the usual schematic illustrations. Particularly the distribution patterns of closely related, apparently sympatric, species should yield information concerning the “fragmentation” of a habitat into niches. 2. Meiofauna and Macrofauna. The meiofauna should be included in community classifications. This might conceivably throw some additional light onThorson's “parallel level bottom community” concept. 3. The “specific area of activity”. By calculating for dominant species or feeding types the ratio: surface area of substrate per dry weight of animal, we arrive at an expression which is ecologically a more meaningful measure of population density than, for example, specimens per m². It can be shown that this “specific area of activity” is indirectly related to the weight and probably proportional to the rate of metabolism of the animals. The area of activity also provides a measure of the food potential of the habitat. In the few habitats investigated, predators occupied a weight specific area about four times as large as that occupied by deposit-feeders. 4. Patterns of vertical distribution. By means of core samples which are sectioned and studied quantitatively, it can be shown that different species of nematodes, polychaetes and other small animals may have their zones of maximum abundance in different layers of the substrate. The redox potential of the substrate is likely to be one of the factors governing the total number of specimens in each layer. 5. Physiological investigations, even simple measurements of oxygen consumption, can lead to important conclusions regarding the various modes of feeding and metabolism employed by different, or even seemingly similar, feeding types. Thus, amongst nematodes, deposit feeder species with low, medium and high Q_O2 can be distinguished.     

三环泡湿地浮游动物功能群季节变化及其影响因子

为了研究寒区湿地浮游动物功能群的季节变化以及水环境等因素的影响,对淡水浮游动物进行了功能群划分,以北方寒冷地区沼泽型湿地三环泡国家级自然保护区为例,于2014年春季(5月)、夏季(7月)和秋季(9月)对三环泡国家级自然保护区15个采样点进行了浮游动物采样,系统分析了浮游动物功能群的组成特征。结果表明:三环泡国家级自然保护区浮游动物功能群共划分为7个功能群,春季以功能群RF占优势,为83.82%;夏季以功能群RC、PF、RF和LCC占优势,分别为34.15%,19.58%,18.49%和10.54%;秋季以功能群RC和RF占优势,分别为71.94%和17.86%。浮游动物功能群季节变化表现为RF→RC+PF+RF+LCC→RC+RF的特点,表明春季功能群RF对浮游植物起到了很好的滤食作用,夏季和秋季功能群RC对功能群PF和RF捕食压力较大。通过Pearson相关分析和RDA多元统计分析表明,种间竞争、氯离子(Cl-)、总氮(TN)、总无机碳(IC)和生物耗氧量(BOD5)是影响三环泡国家级自然保护区浮游动物功能群的主要影响因素,除功能群RF外,其它功能群同氯离子(Cl-)、总氮(TN)和总无机碳(IC)显著正相关,同生物耗氧量(BOD5)显著负相关,SCF、MCF、MCC和LCC由于食物竞争和捕食之间的关系表现出极显著的相关性,同为捕食关系的RC和RF、PF则没有表现出明显的相关性。种间竞争、浮游植物上行效应和营养盐是影响寒区沼泽型湿地浮游动物功能群季节变化和生物量的主要因素。     

Feeding ecology of the proboscis monkey (Nasalis larvatus)

Proboscis monkey (Nasalis larvatus) feeding behavior and ecology were studied at the Natai Lengkuas Station, Tanjung Puting National Park, Kalimantan Tengah, Indonesia. Data on feeding behavior were collected using scan sampling during group follows. Three vegetational plots containing 1,732 trees were established and monitored monthly for changes in fruit, flower, and young leaf production. Basal area and canopy cover were calculated and used in estimating food abundance. Proboscis monkeys were found to be folivore/frugivores, specializing in seed consumption. At least 55 different plant species were used as food sources, with a marked preference for Eugenia sp. 3/4,Ganua motleyana and Lophopetalum javanicum. These tree species were among the most frequent and most dominant. However, proboscis monkeys were selective feeders; use of tree species as food sources was not based simply on relative density. During times of low food abundance and/or availability proboscis monkeys switched dietary strategies and increased dietary diversity. The average total home range was estimated to be 130.3 ha, with an average group density of 5.2 groups per km². The average biomass per km² was estimated to be 499.5 kg. Given their high biomass and predilection for consuming seeds of dominant species, proboscis monkeys may help to maintain and increase vegetational diversity.