Lotic Waters Research Articles

Rates of Protozoan Bacterivory in Three Habitats of a Southeastern Blackwater River

Although protozoa have been largely disregarded in the trophic structure of lotic systems, they have been shown to be important in lentic and marine environments. As part of a larger study concerning the basis of secondary production in the Ogeechee River, GA, preliminary experiments were done using fluorescently-labelled bacteria to directly measure bacterial grazing by protozoa. Protozoan grazing rates can be as high in moving lotic waters as in still waters as demonstrated by comparing a main channel site, a backwater, and a floodplain pond. In the main channel site during April and May 1988, flagellates and ciliates ingested an average of 17 and 320 bacteria/individual/hr, respectively. When this is multiplied by the high protozoan densities present, an average of 47% of the water-column in the main channel is estimated to be cleared of bacteria by protists each day. Protozoan bacterivory could facilitate carbon flow to higher trophic levels by turning bacteria into larger parcels of carbon and nutrients which are available to a greater portion of the filter-feeding members of communities.

SPATIAL–TEMPORAL VARIABILITY AND THE STUDY OF AQUATIC INSECTS,

AbstractSpatial and temporal variability are essential considerations in the study of aquatic insects. Traditionally, these two sources of variability are treated separately; however, they should be considered together because they occur concurrently in natural systems. To illustrate this interaction, we constructed two-way variability tables in which spatial (habitat, reach or zone, system, intersystem) and temporal (within a day, within a season, within a year, year to year) scales were ordered on separate axes, and examples of concurrent spatial and temporal variability were entered at the intersects of the scales. We examined three aspects of aquatic insect life histories in lotic and lentic waters using such tables: emergence, feeding and growth, and movements and migrations. It proved easier to find examples for the stream tables than for the lake tables, perhaps because of greater spatial and temporal variability in lotic than lentic waters. Also, more papers have been published on stream than on lake insects over the last decade or so. Spatial and temporal scales at which lotic and lentic research is done were determined by examining the recent contents of five key aquatic journals (≈ 500 articles). Research on aquatic insects appears generally to be done at relatively long temporal scales, but at smaller spatial and shorter temporal scales in lotic than lentic systems. Perusal of the literature to find examples of concurrent spatial and temporal variability revealed the prevalence of a “mean-values” appproach to data analysis, in which investigators “homogenize” data to reduce spatial and temporal variability. However, it is this spatial and temporal variability that often provides an explanation of factors causing the patterns observed. A “variance” approach, in which data are disaggregated and fluctuations or extremes are considered, may be far more informative and may elucidate underlying mechanisms.

Phylogeny of Pupation in Trichoptera, with Proposals on the Origin and Higher Classification of the Order

Analysis of modes of pupation in Trichoptera reveals two fundamental types of pupal enclosures and concomitant systems for water circulation. In one (Rhyacophilidae, Hydrobiosidae, Glossosomatidae, Hydroptilidae-infraorder Spicipalpia Weaver), pupating larvae construct a closed cocoon of parchment-like silk, usually discrete from the pupal enclosure of small stones; water currents bathe the external surface of the cocoon during metamorphosis. In the other type (most families in the suborders Annulipalpia Martynov s.s. and Integripalpia Martynov s.s.), larvae con- struct a pupal cell with open meshes or holes at each end, permitting water currents to bathe the surface of the pupa directly during metamorphosis. Exceptions in the Philopotamidae, Stenopsy- chidae, Ecnomidae, and Phryganopsychidae are considered. The function of trichopteran cocoons during metamorphosis is considered, indicating that osmotic relations in closed cocoons of parchment-like silk in the Rhyacophilidae and allied families impede the efficiency of respiration mediated solely by diffusion of oxygen across the semipermeable wall of the cocoon. Because ovoid, closed cocoons of parchment-like silk also occur in primitive Lepidoptera, the sister group of Trichoptera, cocoons of this type are proposed as part of the groundplan of Tri- choptera. Consequently, the open pupal cells of Annulipalpia (retreat-makers) and Integripalpia (case-makers) are interpreted as derived. It follows that the habitat common to the families con- structing closed cocoons-cool, flowing waters-would likely have been the habitat in which Tri- choptera originated. The hypothesis proposed for the phylogeny of pupation in Trichoptera is that the closed cocoon of semipermeable silk in the ordinal groundplan required Trichoptera to become aquatic in cool, lotic waters; and that evolutionary innovation through subsequent derivation of cocoons of perme- able silk with ventilatory openings enhanced the efficiency of respiration, enabling Trichoptera to invade warmer waters of reduced current, and opening the way for radiation of the major lineages now extant-the retreat-making (Annulipalpia s.s.) and the case-making (Integripalpia s.s.) families. An alternative form of the higher classification of Trichoptera is proposed and discussed, elevating the Spicipalpia, termed the cocoon-making Trichoptera, to the rank of a third suborder, co-ordinate with the Annulipalpia and Integripalpia.

Archaeochlus Brundin: a midge out of time (Diptera: Chironomidae)

Abstract. Archaeochlus, a plesiomorphic genus of Podonominae (Chironomidae), is revised and two new species (biko from Namibia and brundini from southwestern Australia) described. The systematic status of the genus and the tribe Boreochlini is reassessed. Biogeographic evidence, sustained by a fossil record, dates the genus at least to the Upper Jurassic. The ecology of early Chironomidae is suggested to be eurythermic and hygropetric rather than cold stenothermic in lotic waters.

Review Article: Rearing and Colonization of Black Flies (Diptera: Simuliidae)1

Black flies are serious pests and important disease vectors in many parts of the world. Efforts to control simuliids and their associated diseases have been hampered by research limitations related to our previous inability to establish permanent colonies of any species or to even successfully rear large numbers of healthy adults from field-collected eggs. Major difficulties have involved providing in the laboratory suitable lotic waters for larval growth and development, and adult environments that promote survival, mating, blood feeding, and egg laying. Recently much progress has been made in developing methods for mass rearing and colonizing black flies. In just the past 3 years, 8 different species, including important vectors of human onchocerciasis, have been successfully maintained for multiple generations in the laboratory. In this review, we discuss the recent methodologies that have been employed in these efforts, provide useful hints for rearing, and point out potential advantages, disadvantages, and problems associated with the various techniques currently used in culturing black flies.

A Method for Measuring Oxygen in Aquatic Microzones

Abstract A method to obtain accurate dissolved oxygen concentration (DO) measurements within a 16-mm microzone was developed using oxygen-permeable dialysis tubing with a 12-ml water sample and a modification of the micro-Winkler technique. Controlled experiments showed that W within tubes reached 99% equilibrium with ambient water in less than 3 hours in lotic waters and in less than 5 hours in lentic waters with experimental error of 0.05 mg/liter. A kit to perform the DO measures can be assembled for about $150, and samples can be run in less than 10 minutes.

The sexuality of Corbicula fluminea (Müller) in lentic and lotic waters in Hong Kong

The sexuality of Corbicula fluminea (Müller) in lentic and lotic waters in Hong Kong

Algal bioassay of the portage lakes, summit County, Ohio

The Portage Lakes are a series of natural lakes and man-made reservoirs in the upper Tuscarawas River of northeastern Ohio. Algal assays with Selenastrum capriconutum Printz suggested that the temporal pattern of water fertility differed between the more lentic water bodies and those with more lotic characteristics, probably reflecting differences in nutrient availability. Algal growth rates in the lentic water bodies ranged from approximately 0·6 doublings a day in early summer to <0·2 doublings a day in late summer. In contrast, algal growth rates in the lotic water bodies increased from 0·2–0·3 doublings a day in June to 0·3–0·5 doublings a day in July, and then declined in August to <0·3 doublings a day. Nutrient enrichments with PO 4-P and NO 3-N indicated that P was usually the major limiting nutrient in both groups of lakes. NO 3-N additions sometimes stimulated algal growth in the lotic water bodies.

A description of the larva and pupa of Eurycnemus crassipes (Panzer) (Diptera: Chironomidae)

AbstractThe larva and pupa of Eurycnemus crassipes (Panzer) are described for the first time. Larval and pupal diagnoses are given for the genus Eurycnemus van der Wulp. — E. crassipes is found in lotic waters where they may be associated with Hydropsyche pellucidula or H. siltalai (Trichoptera). The species appears to be univoltine with main emergence between late June and beginning of September. The species is known from Europe while the genus is reported from the Holarctic Region.

AN EXPERIMENTAL GRADIENT ANALYSIS : HYPOSALINITY AS AN "UPSTRESS" DISTRIBUTIONAL DETERMINANT FOR CARIBBEAN PORTUNID CRABS

This study examines ecological distributions in a guild of Caribbean demersal crabs (family Portunidae) on a gradient in terrestrial influence on aquatic climate, along which the major monotonic physicochemical variable is salinity. Distributions were established by sampling in fresh lotic waters and bays with highly restricted exchange with the sea, which, for marine groups, are constantly and unpredictably climatically severe, respectively, through climatically equable waters around coral reefs. The 16 demersal portunid species collected in Jamaica (the main study area), the Florida Keys, Colombia and Curaçao all occur in undiluted seawater, but progressively fewer are found as salinity decreases. Hyposaline biotopes are virtually monopolized by members of the genus Callinectes, while Arenaeus, Portunus and Cronius spp. were found only in higher salinities. Callinectes spp. display serial replacement along the gradient; crab stages of C. maracaiboensis, C. bocourti and C. sapidus occur mainly in fresh waters, while dominance peaks occur in progressively higher salinities for C. exasperatus, C. danae, C. marginatus and C. ornatus. Acute hyposalinity tolerances of the common species were determined experimentally, and follow the same order as upstress limits and dominance peaks. The species composition of the guild changes from domination by the most to the least euryhaline species as likelihood of severe dilution decreases. In biotopes with temporarily ameliorated weather, less euryhaline species invade and may replace more euryhaline species at a rate proportional to the biotope's remoteness from the immigrants' source area. Freshwater Callinectes are catadromous, storing energy in hyposaline ecosystems, but reproducing in higher salinities.

Wave-Zone Macrobenthos of the Exposed Canadian Shores of the St. Lawrence Great Lakes

Two series of qualitative collections of the benthic macroinvertebrates inhabiting the wave-zone (0-2m) along the exposed Canadian shores of the St. Lawrence Great Lakes were made in the summer of 1974. This fauna consisted largely of typically lotic water forms, including Heptageniidae (Ephemeroptera) and Hydropsychidae (Trichoptera). The variety and relative abundance of invertebrates was directly related to substrate stability. Insects other than chironomids were rare in Lake Ontario and hypotheses to explain this different fauna are presented.

Competitive Exclusion Along a Habitat Gradient Between Two Species of Salamanders (Desmognathus) in Western Florida

The geographic distributions of two congeneric salamanders interdigitate in western Florida. A Coastal Plain endemic species (Desmognathus auriculatus) occurs throughout coastal swamps in ana between major drainages; it disperses upstream into drainages from population centres near drainage mouths. Desmognathus fuscus is a northern species (at its southern distributional limits in Florida) that disperses downstream in drainages from headwater population centres. Florida habitats occupied by either species can be ordered along a gradient ranging from lotic waters of first order streams (including the unique 'steepheads') to lentic conditions of swamps, sloughs, and lake margins. When allopatric, D. auriculatus occurs over the entire range of habitats and especially in steepheads; but where sympatric with D. fuscus, D. auriculatus occurs only in stream habitats greater than order 2. In several adjacent

The Life History of Procambarus hayi

The- life history of Procambarus hayi (Faxon) was studied for 2 years near State College, Miss. Seasonal and temporal changes within the populations were determined from periodic field samples and laboratory observations. The known geographic range of the species was defined and its preference for lentic and sluggish lotic waters was in- dicated. P. hayi bred in spring and summer and oviposited and hatched from late summer to autumn. A study of monthly ovarian egg development confirmed the period of oviposition. Oviposition and the first juvenile molts occurred within the burrow. Upon reaching the 3rd instar, juveniles became independent of the female and entered the open water from mid-September through Novem- ber. Most became adults during May and June of the following year after attaining a carapace length of 36.0 to 45.0 mm. Most crawfish reproduced 8 to 10 months after hatching, lived to reproduce again the following summer at 18 to 20 months, then died during the following autumn at approximately 24 months. A few apparently reproduced a third time and died after 36 months.

Benthic Macroinvertebrates of the Otter Creek Drainage Basin, Northcentral, Oklahoma

Distribution, seasonal abundance, and ecological notes on 122 taxa of benthic macroinvertebrates collected in the Otter Creek Drainage system are discussed. The freshwater nemertean, Prostoma rubrum (Leidy), and the oligochaetes, Tubifex templetoni Southern, Dero digitata (Muller), Nais variabilis Piguet, Pristina breviseta Bourne, P. longiseta Leidyi Smith, P. longidentata Harman, and two species of Pristina new to science are reported from Oklahoma for the first time. Benthic macroinvertebrate studies have recently become of increased importance to aquatic biologists because of their use in evaluating effects of pollutional effluents, and recognition of their central position in aquatic food chains. Benthic macroinvertebrates of southwestern lotic waters are poorly known. The only major contributions in this area are by Hornuff (1957) and Wilhm and Dorris (1966). This situation is further complicated by the draeth of taxonomic studies on immature stages of many aquatic invertebrates. These points can be emphasized by pointing out that eight of the 11 species of oligochaetes collected during this study represent new state records, two of these are new to science. Furthermore, only 65 of the 122 taxa collected could be identified to species. This report consists of information concerning distribution, seasonal abundance, and ecological notes on species collected during a one year study of the Otter Creek Drainage system. Distribution is discussed in terms of Horton's (1945) stream order classification, as modified by Strahler (1954; 1957) and redescribed by Kuehne (1962) and Leopold (1962). Kuehne (1962), Harrel et al., (1967) and Harrel and Dorris (1968) showed the usefulness of stream order classification in successional studies. Detailed evaluations of drainage basin geomorphology, physicochemical conditions, and species diversity of benthic macroinvertebrates and fishes have been published elsewhere (Harrel et al., 1967;

Environmental Modification of Habitat Selection in Adult Damselflies

The adult habitat preferences of four damselfly species were analysed to determine whether their choices could be modified by environmental conditions at the site of adult emergence. Four species occurring in southwestern New Mexico were studies. Hetaerina americana, Hyponeura lugens, and Ischnura demorsa prefer lotic waters while I. damula favors lentic conditions. Last instar larvae of each species were transferred from their favored habitat so upon emergence the adult would be initially confronted with an environment unlike that preferred by the species. Such larvae composed the experimental group for each species. Control groups provided observations on habitat preference from individuals known to have emerged from the favored habitats. Chi—square analysis indicates a significant modification of behavior occurred in all four experimental groups. Heritability of habitat selection is not sufficiently understood for use in evolutionary studies.

An Evaluation of Some Techniques for the Collection and Analysis of Benthic Samples with Special Emphasis on Lotic Waters

A consideration of a large number of procedures for the collection and analysis of benthic samples, with particular emphasis on stream investigations and the importance of substrate particle size as a common denominator in benthic ecology, reveals that only certain techniques are suitable. Although either systematic or stratified random samplings are appropriate for faunal surveys, the careful selection of sample sites in singlespecies studies can provide maximum information per unit sampling effort. In order to adequately describe the micro-distribution of benthic organisms, investigations must be conducted on a year-round basis. Only bottom samplers, such as the core-type, which retain the entire sediment sample for analysis are desirable. Measurements of current velocity should be made close to the substrate-water interface. The removal of the fauna by elutriation and hand sorting allows for further physical and chemical analyses. Physical analysis of stream sediments can be accomplished through the decantation of silt and clay followed by dry sieving of the coarser material. In addition, a new photographic technique for substrate analysis, described in detail, can provide information on the surface sediments. Indications of the organic content of sediments can be obtained by the dry combustion carbon train method or, when clay content is low, from loss of weight on ignition values. However, new techniques are called for, especially those directed toward the food habits of particular species. The Wentworth classification, modified to include a gravel category, should be followed, and the size classes converted to the phi scale in graphic presentations of sediment data. Since Shelford (1914) became interested in the ecology of benthic macro-invertebrates, Needham (1928) conducted surveys of New York streams, and Shelford and Eddy (1929) formulated some fundamental approaches for the study of stream communities, a great many benthic investigations have appeared in the literature. The facts accumulated to date show that the orientation of aquatic invertebrates to various environmental parameters results in nonuniform distributions in which given animal groups are associated with measurable ranges of environmental conditions. Benithic ecologists have spent considerable effort measuring the most obvious parameters in the aquatic environment to determine their effects on the distribution of various groups of animals. Substrate, current velocity, and food materials have been shown to -be of primary importance, although the way in which these interrelated parameters determine distribution remains to be completely delineated. Undoubtedly, some parameters are more critical than others, but it may be that all physical Present address, Department of Biological Sciences, Northwestern University.