Trophic Categories Research Articles

The Significance of Zooplankton in the Cycling of Phosphorus in Lakes of Different Trophic Categories

AbstractThe species composition, number, biomass and phosphorus excretion rate (PER) of zooplankton (Crustacea and Rotatoria) in 8 mesotrophic and eutrophic lakes were studied. PER were calculated using specific expenditures on metabolism estimated from the oxygen uptake, phosphorus content in zooplankton and field observations of number and biomass of planktonic Rotatoria and Crustacea. The zooplankton biomass and PER increased from mesotrophic to eutrophic lakes. The values of PER were compared with primary production and spring phosphorus concentration. The relative significance of zooplankton in phosphorus cycling declined with increasing trophic category of lakes.

The soil fauna of a beech forest on limestone: trophic structure and energy budget.

The soil fauna of a mull beech forest on lime-stone in southern Lower Saxony (West Germany) was sampled quantitatively. Biomass estimates, trophic characteristics, and measurement and calculation of the energetic parameters of the constituent animal populations were used to construct an energy budget of the total heterotrophic subsystem of the forest. Mean annual zoomass amounted to about 15 g d wt m-2; earthworms (about 10 g d wt m-2) and other groups of the macrofauna were dominant. Protozoa constituted about 1.5 g d wt m-2. Relative distribution of zoomass among the trophic categories was 50% macrosaprophages, 30% microsaprophages, 12% microphytophages, and 4% zoophages. Total annual consumption rate of the saprophagous and microphytophagous soil fauna (6328 and 4096 kJ m-2 yr-1, respectively) was of the same order of magnitude as annual litter fall (canopy leaves 6124 kJ m-2 yr-1, flowers and fruits 944 kJ m-2 yr-1, herbs 1839 kJ m-2 yr-1, fine woody material 870 kJ m-2 yr-1, tree roots 3404 kJ m-2 yr-1, without coarse woody litter). Primary decomposers (macrosaprophages) were the key group for litter comminution and translocation onto and into the soil, thus contributing to the high decomposition rate (k=0.8) for leaf litter. Consumption rates of the other trophic groups were (values as kJ m-2 yr-1): bacteriophages 2954, micromycophages 416, zoophages 153. Grazing pressure of macrophytophages (including rhizophages) was low. Faeces input from the canopy layer was not significant. Grazing pressure on soil microflora almost equalled microbial biomass; hence, a large fraction of microbial production is channelled into the animal component. Predator pressure on soil animals is high, as a comparison between consumption rates by zoophages and production by potential prey - mainly microsaprophages, microphytophages and zoophages - demonstrated. Soil animals contributed only about 11% to heterotrophic respiration. However, there is evidence that animals are important driving variables for matter and energy transfer: key processes are the transformation of dead organic material and grazing on the microflora. It is hypothesized that the soil macrosaprophages are donor-limited.

Estimation of the interval between feeding and capture in peridomestic Glossina tachinoides

From successive 24-hourly dissections of non-teneral field-caught Glossina tachinoides Westwood which had fed on a guinea-pig in the laboratory, the progressive movement of a bloodmeal through the midgut was monitored and five stages (categories) in the trophic cycle identified. The frequency distribution in these trophic categories of G.tachinoides subsequently caught in the peridomestic agro-ecosystem at Orie-Orba near Nsukka by means of the biconical trap revealed that males and females had fed 2.8 +/- 0.4 and 2.4 +/- 0.4 days respectively preceding their capture.

Trophic Structure of Benthic Macroinvertebrates in Kings Creek

Trophic Structure of Benthic Macroinvertebrates in Kings Creek

Diets of fishes of the upper continental slope of eastern Tasmania: content, calorific values, dietary overlap and trophic relationships

Diets of 15 species of demersal and pelagic fishes on the upper continental slope (420 to 550 m) were determined, based on samples taken every two months over 13 mo (April 1984 to April 1985) off eastern Tasmania. The calorific contribution of each prey item to the diets was determined. The fish could be divided into four trophic categories: pelagic piscivores, epibenthic piscivores, epibenthic invertebrate feeders and benthopelagic omnivores. Dietary overlap between the groups was low. The pelagic piscivores Apogonops anomalus, Trachurus declivis, Brama brama, Lepidopus caudatus and Macruronus novaezelandiae primarily consume the shelf-break myctophid Lampanyctodes hectoris; their diet is narrow, with a large overlap between species. The epibenthic piscivores Deania calcea and Genypterus blacodes both take a greater variety of prey, but have little dietary overlap. The fish feeding on epibenthic invertebrates, Coelorinchus sp. 2 and Centriscops humerosus, obtain most of their energy from benthic Crustacea and Ophiuroidea, supplemented with Lampanyctodes hectoris; the diet is broad, with little overlap. Among the benthopelagic omnivores (Cyttus traversi, Coelorinchus sp. 4, Lepidorhynchus denticulatus, Neocyttus rhomboidalis, Helicolenus percoides, Epigonus denticulatus and E. lenimen), most diets are broad and show slight overlap. All but E. denticulatus consume significant quantities of Lampanyctodes hectoris as well as Crustacea, particularly Polychaeta, Euphausiacea and Pyrosoma atlanticum. Seasonal changes in diet occurred in G. blacodes, T. declivis, Lepidopus caudatus, Coelorinchus sp. 4, Lepidorhynchus denticulatus, H. percoides, E. denticulatus and E. lenimen; these were related to changes in abundance of particular prey species, not to alterations in feeding habits. Only three species, Lepidopus caudatus, Coelorinchus sp. 2 and H. percoides, showed significant diel feeding periodicity. Ontogenetic dietary changes were evident in Cyttus traversi, Coelorinchus sp. 2, Lepidorhynchus denticulatus and H. percoides. Cyttus traversi and H. percoides progressively changed from crustaceans to fish as their size increased. The diets of size classes within species showed little overlap, except for Lepidorhynchus denticulatus, which eats chiefly euphausiids and Lampanyctodes hectoris at all sizes. In addition to describing the diets and trophic relationships of 90% of the fish biomass, the results emphasize the importance to the entire fish community of mesopelagic food resources, particularly Lampanyctodes hectoris. Many benthopelagic species undertake extensive vertical migrations in search of prey, thus playing a major role in the transport of energy from midwater regions to the benthos of the continental slope.

Food Habits of Species of Ephemerellid Mayflies (Ephemeroptera: Insecta) in Streams of Oregon

Data on food habits were obtained for 20 species in the mayfly family Ephemerellidae. Diet of a species often varied with site, habitat and size, but such variation did not completely mask differences among species. Adaptive radiation in diet is relatively great in this family, but species showed no distinct groupings when classified either on a functional basis or by traditional trophic categories.

Morphological and dietary variations in a riverine population ofPycnopsyche guttifer(trichoptera: Limnephilidae)

Abstract P. guttifer is typically found associated with allochthonous debris in slow‐water areas of streams where it is said to function as a classical shredder. A population of 5th instar larvae from a large Quebec river appears to depart from this ideal in that many were found in areas of the river where current speeds exceed 30 cm/ s, and many were eating predominantly algae thus exhibiting features of the scraper trophic category. Considerable variations in larval and case dimensions were noted, some of which are related to features of the microhabitat. The need for more data, from a variety of field conditions and localities, on so‐called well‐known species is discussed.

Trophic variety and abundance of hoverflies (Diptera, Syrphidae) in an English suburban garden

28924 hoverflies of 85 species were caught in a Malaise trap in an English suburban garden during the eight‐year period 1972–79, and three additional species were hand‐netted. Hoverfly larvae fall into five trophic categories all of which were represented by adults in the trap sample. 82.71% of the hoverflies trapped have larvae that feed on aphids, 12.04% feed on decaying organic material, 5.14% eat living plants, 0.09% scavenge in Hymcnoptera nests, and 0.02% are associated with tree sap or rotting wood. The relative frequency of the different trophic groups varied annually and seasonally although the aphid‐feeders were nearly always the most abundant. 22 species are believed to breed in the garden, and a further 29 in the surrounding area; 15 species are regarded as casual and 22 as chance visitors. It is suggested that the high plant diversity and spatial heterogeneity of gardens result in them supporting more species than would be found in a natural area.

Associations of lake-living Chironomidae. A cluster analysis of Brundin's and recent data from Swedish lakes

Three major lake clusters, corresponding to different trophic categories of lakes, were identified in a group average cluster analysis of 34 lakes and 33 profundal chironomid taxa. The classification of chironomids was not as distinct as that of lakes, presumably because of the incomplete identification of species. Groups of chironomid taxa associated with different lakes types could be more sharply delineated in a post-clustering analysis after reallocation of some lakes and taxa.

Study of the fauna inhabiting the holdfasts of Laminaria hyperborea (gunn.) fosl. along some environmental and geographical gradients

A survey of the holdfast fauna of Laminaria hyperborea was carried out at thirty-five sites around the UK, mostly along the North Sea and south coasts. Data from different age classes of holdfast from a polluted and unpolluted site indicate that volume of holdfast space is a most important measurement of sample size, a minimum size of sample being one litre and, preferably, three. Gradients of increased heavy metals were defined down the North Sea and west coasts and, by utilising measurements of kelp penetration, water clarity gradients were determined as increasing northwards on the west coast and both north and southwards on the North Sea coast from a point near Tyne and Wear county. Analysis of holdfast fauna showed numerous gradients of total numbers, species and diversity which correlate closely with the heavy metal and water clarity gradients, or with undetermined parameters analogous to latitude and longitude. Where there were increases of heavy metals or decreases of water clarity, various reciprocal relationships between suspension feeders and all other trophic groups were commonly observed. In the North Sea numbers of suspension feeders increased while numbers of all other trophic groups declined. On the west coast a heavy metal increase correlated with a decreasing species richness of all trophic categories except suspension feeders, while with total numbers only suspension feeders showed an increase. On the south coast transect neither gradient existed, and only here did all trophic categories covary, except at one very polluted site where the same reciprocal relationship was again indicated. In terms of species similarity the North Sea showed a greater pool of common species than occurred between sites of other regions and between North Sea sites with other regions, despite the widest range of heavy metal levels and wate clarity that existed there. Between-site similarity appeared to be much more dependent on geographical proximity than on the two measured environmental factors. It is suggested that effects of clarity-reduction can be measured by trophic analysis more successfully than by species presence or absence, and that changes of holdfast fauna along the North Sea coast are due largely to pollution.

Some Relationships between Systematics and Trophic Ecology in Nearctic Aquatic Insects, with Special Reference to Trichoptera

Based on the general premise that the genus represents an ecological, as well as a morphological type, a number of generalizations are developed concerning the use of food resources in fresh waters by Trichoptera and some other aquatic orders of the Nearctic fauna. There are more genera of the Nearctic order Trichoptera (144) than in the orders Ephemeroptera (59), Odonata (84), or Plecoptera (88). Trichoptera have a wide range of habitats and a broader range of trophic categories than any of these other wholly aquatic orders. This relatively high ecological diversity is attributed to the many uses of silk by trichopteran larvae. Genera of 3 families of filter—feeding Trichoptera show differences in distribution which are correlated with the type of food particle. Most of these genera are found in the eastern deciduous forest biome and all sizes of organic particles are filtered. In the western montane forest biome, generalist filter feeders are absent or underrepresented; predacious genera or those filtering very fine particles have been more successful. Possibly there are differences in the quality and quantity of fine particulate detritus between eastern and western forest which account for the above distributions. In the trichopteran family Limnephilidae, genera of the detritivorous shredders have exploited lotic, lentic, and even terrestrial habitats; grazer genera are mostly confined to cool lotic habitat. Grazers in other families of Trichoptera are also more diverse in upstream areas, and grazer genera are particularly well—represented in the western montane forest biome. In streams of the eastern deciduous forest biome, the relative proportions of feeding categories shown by trichopteran genera appear to agree with a general trophic model of benthic invertebrate communities in that dominance of shredder—collector genera in upstream sections gives way to grazer—collector dominance downstream. In western montane streams, trichopteran generic distributions conform to the model downstream, but show relatively more grazers than the model would predict for upstream areas. Periphyton growth, and thus food for grazers, may be more abundant in the western coniferous forest than in the shaded streams of the eastern deciduous forest. In general, an ecological analysis of Nearctic Trichoptera at the generic level appears to provide a reasonable indication of the energy resources available in aquatic habitats.

Bird Species Diversity on an Andean Elevational Gradient

This paper analyzes patterns of bird species diversity on an elevational transect of the Cordillera Vilcabamba, Peru. Major changes in climate and vegetation are encompassed by the transect which extended from the Apurimac Valley floor at 500 m to the summit ridge of the range at >3,500 m. Four vegetation zones are easily discerned–lowland rain forest, montane rain forest, cloud forest, and elfin forest. In progressing upwards there is a monotonic trend toward decreasing canopy stature and reduced number of plant strata. The vegetation gradient provided the opportunity to examine the relation between bird species diversity and habitat complexity in an entirely natural setting. The decrease in forest stature with elevation was closely paralleled by decreasing avian syntopy (the total number of bird species cohabiting the forest at a given elevation). Bird species diversity was shown to be highly correlated with foliage height diversity, using either four or five layers in the foliage height diversity calculation (r = .97), and less well correlated using three layers, as defined previously by MacArthur (r = .84). At this superficial level the trend in bird species diversity seemed to be adequately explained as a response to the vegetation gradient. This preliminary conclusion was found to be illusory when the elevational trend in syntopy was reexamined separately for three major trophic subdivisions of the fauna. The number of insectivores decreased 5.2—fold from the bottom to the top of the gradient, frugivores decreased by a factor of 2.3, and nectarivores showed no change. It was now clear that the diversity in each of these trophic categories was responsive to environmental influences other than, or in addition to, the gradient in habitat structure. Additional factors implicated by the available evidence are competitive interactions with other taxa at the same trophic level, changing composition of the resource base as a function of elevation, and declining productivity at high elevations. Analysis of netted bird samples revealed an unexpected diversity maximum in the lower cloud forest zone. The immediate cause of this was a relaxation of the vertical stratification of foraging zones, such that an anomalously large fraction of the species present entered the nets. The excess diversity was found to consist almost entirely of insectivores. Several factors appear to contribute to the ultimate causes of the diversity maximum: greater patchiness of the montane forest due to the rugged topography, a higher density of foliage near the ground, and possibly increased resource productivity. A correlation between diversity and density in the netting results suggested a causal connection mediated via resource levels. The conclusion in that diversity is a complex property that is responsive to many types of influences beyond simply the structure of the habitat.

Régimes et comportements alimentaires de quelques poissons des récifs coralliens de Tuléar, Madagascar

The diet and feeding behaviour of coral reef fishes living in the inner reef flat have been studied near Tulear, Madagascar. 231 species belonging to 52 families have been observed in this habitat. The diet of the 31 most common and representative species have been studied quantitatively, using a modification of Hureau’s technique. Underwater observations have been conducted both by day and by night. The fish community of the inner reef flat comprises resident populations living permanently in this part of the reef and visiting populations temporarily invading the area at high tide. In both cases, certain species feed only by day while others by night ; some feed equally well at any time, others by contrast feed only at dusk. The diet and feeding habits of the 12 most important fish families are summarized. Three main trophic categories are recognized : herbivores, omnivores and carnivores, each of them beeing in turn subdivided into sub-categories. Broadly speaking, herbivorous and omnivo¬ rous fishes feed only during day time, whereas most of carnivorous fishes hunt by night. Diurnal carnivorous species are adapted for the capture of sheltered or protected preys.

Aquatic macrophytes as limnological indicators

SummarySpecies of submersed and floating‐leaved aquatic macrophytes have been place in a series based on their patterns of occurrence in an ordination of floristic lists. Two chemical parameters from lake water analyses are correlated with the species assemblage in individual lakes and trophic categories are defined on the quantitative chemical characteristics of lake waters. The range and limiting tolerance of solute content for many aquatic species are described and related to these trophic categories. Restiction towards eutrophic conditions is considered as an obligate relatinship reflecting physiological demands. Some dystrophic and oligotrophic species are shown to have wide tolerance and are thought to be excluded from sites of higher trophic status by competition rather than physiological limitation.

Relations écologiques des avifaunes sédentaire et migratrice dans une savane sahélienne du bas Sénégal

Monthly censuses were made of an area of 25 hec¬ tares (±62 acres) in the sahelian savannah of the lower Senegal valley, from February 1960 to May 1962. All the birds seen were counted, palearctic and african migrants as well as breeding pairs and nomadic individuals, to estimate the monthly biomasses of the avian consumers. The average adult weigt, the migratory status, the staple food, the layer at which the birds ordinarily live, and the seasons of reproduction of the 97 species recorded (66 sedentary species and 31 palearctic migrants) are given in table 1. Among the sedentary species, only very few live all the year round in the actual census area, most of them being nomadic. Table 2 gives, month by month for the three consecutive years, the number of individuals counted, the number of species and the biomasses in grams, both for sedentary birds and for migrants. Tables 3 to 5 give the same data for the three main trophic categories of our avian population : vegetarian, polyphagous and insectivorous. Eight months out of twelve, palearctic migrants were present in this area ; for most of that period they form an appreciable part of the total population. The highest densities and the greatest biomasses occur at the same time of the year in african species and in migrants. The maximum population density of african birds reached 4,2 birds per hectare in September 1960 and 8,2 birds