摘要:

A new approach that couples the study of biological and hydrodynamic processes has progressively emerged in the biological oceanographic and limnological literature. A review of a large number of papers on phytoplankton, zooplankton, and fish larvae published in the last decade brings out the major characteristics of a new discipline, termed by the authors "dynamic biological oceanography" or "dynamic biological limnology." These studies recognize hydrodynamics as the driving force of aquatic ecosystems, so that the various physical, chemical, and biological factors of the environment are considered as the proximal agents through which hydrodynamic variability is transmitted to living organisms. A central idea to dynamic biological oceanography and limnology is that different hydrodynamic processes and different biological responses occur on different spatial and temporal scales. This leads to a discussion of spatial and temporal scales on both the horizontal and vertical axes and of the relationships between the physical and biological scales, on the one hand, and the sampling scale, on the other. Anticipated forthcoming developments concern the eventual merging of horizontal and vertical studies in an integrated approach to aquatic ecosystems and the design of new sampling techniques and schemes to probe the significant scales of variation in dynamic biological oceanography and limnology. Common lines of research are suggested for the coming years.

ISSN:0706-652X    

DOI:10.1139/f84-001

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Based on chemical criteria such as excess sulfate and low bicarbonate relative to cation, 50 lakes in the Wawa area show some degree of acidification. We conclude that the observed perturbations of lake chemistry and fish populations were primarily the result of smelting operations in the Wawa area. Six lakes have acidified to pH 3.1–4.1 and had high concentrations of metals such as Al, Mn, and Fe. Most of the lakes were in contact with felsic and mafic metavolcanic rocks containing minerals such as siderite, and only a few lakes had granitic basins. The six most acidic lakes contained no fishes and some lakes in the fume-kill area had known losses of brook trout (Salvelinus fontinalis) and lake trout (Salvelinus namaycush) populations. Based on a regression of number of species on lake area for 34 lakes, it was estimated that 83 fish populations have been lost from 16 lakes. Fish community changes were difficult to assess due to the distributions of species in the four watersheds. The northern pike (Esox lucius)–walleye (Stizostedion vitreumvitreum)–yellow perch (Perca flavescens) community was found now to be present only in lakes distant from the source of emissions. The fish community with brook and/or lake trout as the top predator was the most affected.

ISSN:0706-652X    

DOI:10.1139/f84-002

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

We found the nitrate to phosphate ratio of nutrients regenerated in Baffin Bay to be lower than is typical of most other ocean regions. The conservative tracers NO and PO are constant for water below 500 m providing NO and PO are redefined to account for this different nitrogen to phosphate ratio in the decaying organic matter of Baffin Bay. A modified stoichiometric model for decaying organic material in Baffin Bay was constructed based on measured values of carbonate, nitrate, and phosphate. A major difficulty in assessing the amount of fossil fuel CO2in the ocean is the determination of the amount of inorganic carbon produced during the decay of biogenic material. Using the modified stoichiometric model for decaying biogenic material, we show how regional and seasonal variations in the amount of carbon released and oxygen consumed during decay could be sufficiently different from what is predicted by the Redfield–Ketchum–Richards model to cause major differences in the assessment of the amount of fossil fuel CO2present in the water. The modified stoichiometric model offers the opportunity to determine the oxygen–carbon relationships more accurately and to obtain better estimates of fossil fuel CO2in the ocean.

ISSN:0706-652X    

DOI:10.1139/f84-003

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Exposure to acid-treated water (H2SO4, pH 6.0–4.2) for 21 d altered interrenal and thyroid function in immature rainbow trout,Salmo gairdneri. At a pH < 5.2 plasma Cortisol increased, implying sustained interrenai Cortisol release. Interrenal histology showed hyperplasia and elevated nuclear diameter at pH 4.7. Eight days of acid exposure (pH 4.7) were required to raise plasma Cortisol significantly. At a pH < 4.7 the ratio of plasma T4(L-thyroxine) to T3(3,5,3′-triiodo-L-thyronine) tended to increase in relation to the controls. Depending on the experiment, this was due to either a significant elevation in plasma T4or a decrease in plasma T3. No histological changes were evident in the thyroid of acid-treated trout. Eight days of acid exposure (pH 4.7) were required to depress plasma T3. Coincidental with higher interrenal activity, plasma glucose was elevated in acid-treated fish (pH < 5.2) after 4 d of exposure. The possible relationships of the endocrinde changes to accompanying acid-induced elevations in plasma glucose and protein and hepatocyte histochemistry are considered, and their possible roles as indices of acid stress are discussed.

ISSN:0706-652X    

DOI:10.1139/f84-004

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

In 20 softwater Florida lakes (pH range 4.7–6.8), phytoplankton diversity was significantly higher in the less acidic lakes; mean numbers of species in two groups (1, pH < 5.3; 2, pH > 5.6), each consisting of 10 lakes, was 10.8 and 16.5, respectively. Blue-green algae were dominant in less acidic lakes, while green algae were the most common group in acidic lakes. Phytoplankton abundance also was lower in acidic lakes, but covariation of phosphorus concentrations with pH confounded interpretation. Trends in zooplankton communities along the pH gradient were less pronounced. More acidic lakes had more species than the less acidic lakes, but three measures of species diversity showed no significant differences between the two groups. Zooplankton abundance was lower in the acidic lakes, but the relationship between abundance and pH showed much scatter. Lake productivity probably affects zooplankton abundance more than pH does in the sample group. No clear trends were observed in relative abundance of major zooplankton groups across the pH gradient. Six acid-tolerant species (includingDiaptomus floridanus,Eubosmina tubicen, andDaphnia ambigua) were dominant in all 20 lakes.

ISSN:0706-652X    

DOI:10.1139/f84-005

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Using thermometry, the mixing regime was intensively studied in each of the two principal basins of Shagawa Lake. After the thermocline had migrated past the interbasin sill depth (6 m), it migrated more rapidly in the larger, windswept western basin than in the smaller, sheltered eastern basin. The metalimnetic eddy conductivities (Kz) were also larger in the west basin, ranging from 0.025 cm2∙s−1during intervals of low wind energy up to 0.25 cm2∙s−1during intervals bracketing powerful cold fronts. The bottom temperature increased rapidly in the west basin in response to mixing, reducing total water column stability and increasing susceptibility to a sudden "turnover." Because of these warm bottom temperatures and drainage basin influence, density currents sometimes carry cold water into the benthic zone of the west basin following heavy, cold rains in midsummer. Epilimnetic phosphorus concentrations in Shagawa Lake depend on linkages among weather, basin morphometry, and water column redox. Time series analysis of 8 yr of record reveals the special importance of two factors. First, the anoxic zone below the mixed layer must include an important fraction of the metalimnetic shelf sediments in the western basin (6–10 m zone). Second, the mixed layer must migrate downward and directly entrain water overlying the anoxic sediments. Time series analysis excludes the possibility of sediment release of phosphorus within the epilimnetic zone as the principal control on phosphorus in the pelagic mixed layer. For lakes with similar morphometry and climatic setting, and a previous history of sewage inputs, lake mixing complicates the trophic adjustment of the lake to a reduction in external phosphorus load

ISSN:0706-652X    

DOI:10.1139/f84-006

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The objective of the Babine Lake sockeye salmon (Oncorhynchus nerka) enhancement project was to increase fry outputs (and thus, smolt outputs and adult returns) by expanding and improving available spawning beds through the use of artificial spawning channels and related water flow control facilities. The project proceeded on four basic assumptions: (1) the artificial spawning channels would prove an effective means of producing sockeye fry, (2) the fry produced would be as viable as those produced from natural spawning beds, (3) the lake nursery area had the capacity to support larger juvenile populations, and (4) increased smolt outputs would result in increased adult returns. A before and after study has allowed these assumptions to be tested. Egg-to-fry survival in the channels was close to 40%, as expected. Comparisons of wild and channel-produced fry did not reveal any substantial difference in their distribution, growth, and survival in the lake. Increases in the abundance of fry were followed by corresponding increases in the abundance of underyearlings in the lake and seaward migrating smolts. No significant change in the average size of the juveniles or their survival in the lake could be detected when population size increased. While the assumptions regarding juvenile production were found to be generally valid, adult returns did not meet expectations. This was due largely to the lack of response to increased smolt outputs from even-numbered brood years. Some options for future management are offered.

ISSN:0706-652X    

DOI:10.1139/f84-007

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Red king crab (Paralithodes camtschatica), a prohibited species, are incidentally caught by United States trawl fisheries for yellowfin sole (Limanda aspera) and other groundfish in the eastern Bering Sea. To reduce this incidental catch, we propose a method for determining a king crab conservation zone where trawling would be prohibited. This method considers the gross revenue potentially gained by the yellowfin sole fishery and lost by the king crab fishery by allowing trawling in each of a number of equal-size areas. Utilizing exvessel prices and research survey estimates of species densities, areas are assigned relative values equal to the value of groundfish minus the value of king crab. By including all areas with negative relative values in the conservation zone, the potential gross revenue that could be obtained from the groundfish and king crab resource is maximized.

ISSN:0706-652X    

DOI:10.1139/f84-008

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Cycles in the northern California Dungeness crab (Cancer magister) fishery may be caused by density-dependent recruitment or a cyclic environmental variable. Investigation of these potential causes requires knowledge of the age(s) at which crabs enter the fishery. Behavior of this fishery has previously been analyzed using mathematical models that include density-dependent recruitment and describe changes in age structure with time. From data available on the northern California crab population and a review of previous studies elsewhere it appears that a single year-class of crabs enters this fishery over several years rather than in one year as described by models with only age structure. The realism of models of this fishery can therefore be increased by including size structure. Behavior of size-specific models is in general different from that of age-specific models. However, it is shown here that an effective survival rate can be derived from a size-specific model that enables interpretation as an age-specific model. This is used to demonstrate that inclusion of size dispersion in a population model increases stability, but if the mean age of the population is not changed, it will not substantially change the period of cycles. Because the growth pattern developed here changes the mean age of entry into the fishery it results in cycles with a longer period than determined in previous analyses. With regard to environmental causes, this growth pattern implies time lags of 4 and 5 yr between an environmental factor affecting recruitment and its effect on the catch record.

ISSN:0706-652X    

DOI:10.1139/f84-009

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

An extensive tagging program was carried out on the herring populations along the east coast of Newfoundland during the 1970s as a basis for defining stock management units. The resulting tag recapture data have been examined in relation to the hypothesis that the majority of Atlantic herring (Clupea harengus harengus) return to the same area to spawn in successive years. Our analyses support this hypothesis and indicate that homing rates for Atlantic herring are high (approximately 90%). We concluded that herring fisheries restricted to spawning fish would allow a more rational distribution of fishing effort such that individual spawning stocks could be exploited in varying fashion according to the desired management objectives.

ISSN:0706-652X    

DOI:10.1139/f84-010

出版商:NRC Research Press    

年代:1984

数据来源: NRC