摘要:

Triplicate, 30-litre plastic microcosms containing pasteurized pond water and polyurethane foam substrate sampling devices were placed at 10, 32, and 100 m from an isolated, ephemeral pond near the Virginia Polytechnic Institute & State University campus, Blacksburg, Virginia. A single substrate was collected from each container on days 3, 9, 15, 22, 29, and 36 and sampled for the number and kinds of protozoan species present. The process of species accrual in the pond and the containers was adequately explained by the MacArthur-Wilson equilibrium model. Dummy variable analysis revealed no difference in the rate of colonization among the three distances, but the estimated number of species at equilibrium decreased significantly at 100 m from the pond. The total number of species identified during the experiment decreased with increasing distance from the pond, as did similarity with the pond fauna, also suggesting a distance effect with respect to the pond. Extinction and immigration curves fitted as a function of time suggested that the probability of a species successfully colonizing an island increased as early stages of community development proceeded. Data presented for microbial species accrual in isolated systems appear to be best explained by an interactive model of colonization; the successful colonization of pond species appears to be dependent on the initial arrival of pioneer species, most of which are present in the soil and atmosphere.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665155

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Age distribution of American eel (Anguilla rostrata) populations was compared at sites downstream from each of the first four dams inland from the mouth of the Shetucket/Thames River, CT., and at one site upstream of the fourth dam, during August, 1977. Ages were determined by interpretation of otoliths. The significant differences between age distribution of populations below (1 and 2) and above (3–5) the second dam revealed that dams did impede upstream movement of American eels in the Shetucket/Thames River. Additionally, length-weight relationships reported in other areas of the northeast, and in the entire Thames River Basin, were not significantly different from the pooled sample of American eel in the Shetucket/Thames River.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665156

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An assessment of the resource base for determining dietary preference is obtained by using the pooled stomach content data derived from all fish collected at a study site. The assessment provides a different bias than is obtained by using standard independent environmental sampling methods, in that all food taken by the fish community is included in the preference estimates. An important characteristic of a preference index is its conservativeness.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665157

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Cultures ofNitzschia paleawere grown in a modified Chu 10 medium over a pH range from 4.0 to 9.9. No growth occurred at pH 4.7 or below, but there was increased cell yield at pH 6.4 to 9.9. Cell yield of the diatoms at pH 7 was less than at pH 8.2. Diatoms did not survive in strongly buffered media at 5.0 g/1 or above, but did grow in media buffered at 0.63 g/1 or less.Nitzschia paleaappears to be alkaliphilous.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665158

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Estimates of aquatic community metabolism were made seasonally (1983–1984) at three sites representing an agricultural gradient along the Chippewa River. Annual mean photosynthesis/respiration ratios (P/R), monitored with anin situchamber method, demonstrated an autotrophic-heterotrophic shift consistent with increased farming intensity (P/R=1.31 vs 1.08 vs 0.64). Other productive and consumptive parameters supported those trends summarized in the P/R values. Within-site seasonal measurements indicated summer maxima and winter minima. Particle-sized organic content (AFDW) was determined for chamber sediments in order to locate the source of oxygen metabolism. While productive sections maintained populations of epilithic diatoms and filamentous green algae on relatively large substrates, the most disturbed site was heterotrophically dominated by very small particles.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665159

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Although many limnological surveys have been conducted on major reservoirs in the southcentral United States, little is known about the physicochemical and biotic properties of small impoundments, which constitute the majority of aquatic systems in this part of the country. The major limnological characteristics of Sangre Isle Lake, a small impoundment in northcentral Oklahoma, U.S.A., were evaluated during 1982–1983. Collectively, the data indicate that this lake has limnological features closely resembling those of a typical small, natural eutrophic lake.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665160

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A population of the Asiatic clam,Corbicula fluminea, and eight species of cohabiting unionid mollusks were examined for the presence of the oligochaete,Chaetogaster limnaei. The mollusks were collected in navigation Pool 19, upper Mississippi River. Infestation ofC. limnaeiin the Asiatic clam was significantly greater than in unionids. A decline in occurrence and abundance ofC. limnaeiinfesting the Asiatic clam was found in the winter when the Asiatic clam population also declined. Of the unionid mollusks,Leptodea fragilishad the highest rate of infestation and the highest number ofC. flumineaper individual.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665161

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Ichthyoplankton were sampled in structurally complex shallow-water areas of the Santee River system in South Carolina. The sampling design consisted of a portable push-net apparatus using a 0.5-m diameter plankton net. A resonating reed tachometer was used to maintain a constant towing speed of 1 m/second. The design employed was portable, durable and manuverable in congested shallow-water areas. Statistically similar capture rates obtained between tows demonstrated the precision of this method.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665162

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A portable apparatus was used to filter large quantities of water from streams in California's Sierra Nevada. Samples were processed and examined forGiardiaspp. Cysts ofGiardiawere detected in 22 of 49 (44.9 percent) samples collected at sites downstream from areas of high recreational use and in 5 of 29 (17.2 percent) samples collected at sites downstream from areas of low recreational use. These data indicate that intensity of human use may play a significant role or be a useful indicator inGiardiacontamination of surface water.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665163

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A hand-held benthic corer which uses a plumber's pipe test plug to create suction is described. The test plug excludes water, detritus, aquatic plants, and creates suction that holds substrate in the barrel of the corer. This device is inexpensive, easy to construct, and can be used in shallow water by a person wading, from a boat at depths of about 2 m, or by a diver in deep water.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9665164

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor