Jacob Verduin

Energy Fixation and Utilization by Natural Communities in Western Lake Erie

From 1951 to 1955, the rates of energy fixation and utilization by natural aquatic communities in western Lake Erie were studied under nearnatural conditions at all seasons of the year. The photosynthesis and respiration rates exhibited by communities concentrated by screening water through No. 25 silk bolting cloth, and by communities studied at their natural population density, are presented below. Measurements of respiration of bottom fauna are included. These are related to environmental variables and the energy flow is estimated for (1) the total community, (2) the fraction retained by bolting cloth, and (3) the bottom fauna.

Phytoplankton and Turbidity in Western Lake Erie

31 species were found in the lotic environment. 6. Anatopynia sp., Prodiamesa olivacea, and Calopsectra sp. appear to be restricted to a bottom containing some proportion of sand. Paratenidipes albimanus and Tendipes tuxis were restricted to deposits of muck-detritus. 7. The genera Anatopynia, Procladius, Prodiamesa, Calopsectra, Cryptochironomus, and Tendipes were distributed throughout the sections of the stream investigated.

Caloric Content and Available Energy in Plant Matter

Caloric content of plant matter, as indicated by bomb calorimetry, includes energy which is not available to metabolic processes of the plant. Consequently such data have limited nutritional significance. See full-text article at JSTOR

Principles of Primary Productivity: Photosynthesis Under Completely Natural Conditions

The photosynthetic process under completely natural conditions is highly variable from time to time and place to place. The same can be said for practically all other processes occurring in nature. The variations are such that samples collected a few moments or a few meters apart will routinely differ by 20% and not at all unroutinely by 50% or more. The most important consequence of this variation is that an individual sample is poorly representative of the larger population from which it is drawn. To obtain valid averages representing that population one must draw numerous samples. Moreover, because the individual sample is so poorly representative there is usually no virtue in determining the characteristics of the individual sample with a certainty of 95-98%. An investigator who selects methods which measure the characteristics of the individual sample with a certainty of 80% and which permit him to study five times more samples than methods achieving a certainty of 98% would permit, has made a wise choice. This is perhaps the most valuable idea to be presented in this paper. Consequently it has been placed at the beginning. It is also appropriate here because the methods and results of investigation of photosynthesis under completely natural conditions exemplify this principle.

Photosynthesis and Growth Rates of Two Diatom Communities in Western Lake Erie

During 1949 a year-round study weas made of the photosynthetic activity exhibited by phytoplankton communities inhabiting the waters of the western Lake Erie island region. One conclusion from that study (Verduin 1951b) was that the different species which have become adapted to a particular aquatic habitat show remarkable similarity in photosynthetic rates. In the spring months of 1950 an Asterionella-Cyclotella community was observed in the. waters around Pelee Island and at the same time a Stephanodiscus community was found about 20 mi. east of Pelee Island. The presence of these distinctly different communities afforded. an excellent opportunity to study them simultaneously, using samples collected from each community on the same dates. Their photosynthetic rates, growth rates, and related characteristics are described and discussed below.

Maximal Photosynthetic Rates in Nature

It seems likely that turbulence under natural conditions, both aquatic and terrestrial, is higher than it is in the bottles or leaf chambers used when photosynthesis is measured experimentally. Most of the maximal photosynthetic rates reported in the literature are probably lower than those which occur in nature.

Phytoplankton Energetics in a Sewage-Treatment Lagoon

Metabolic rates in a sewage-treatment lagoon system near Deshler, Ohio, were investigated between March 21 and June 10, 1964. The ponds were well mixed vertically, exhibiting daytime average eddy diffusivities of about 1 cm2 /sec. The waters had a high titratable base, ranging from 3 to 10 meq/1 during the period of study. Low oxygen levels were encountered for only a short period in the second stage of the two-pond system. Light absorption averaged about 99%/m. The phytoplankton communities, dominated by Scenedesmus, rose to values near 50 (mu)1/1. Rates of CO_2-uptake in the order of one mole-m( -3) day( -1) were observed, but O_2 production averaged only one-fifth as high. A graph of CO2 -uptake vs. light intensity revealed a curve closely similar in shape to the typical photosynthesis vs. light curve, but a separate set of data, based on the ( 14)C uptake, showed anomalously high values at surface light intensities. CO_2 uptake by a photosynthetic metabolic process that does not produce oxygen is postulated to explain the imbalance between CO_2 and O_2 budgets.

Separation Rate and Neighbor Diffusivit

Separation rates of neighboring pieces of orange peel floating on the sea were measured under fresh breeze conditions. When Stommels equation for neighbor diffusivity (F) was applied to the data it became apparent that the F value increased by an order of magnitude whenever the time adrift increased by this amount. This is a result of the fact that the increase in spacing distance is squared while the time adrift is not. It is recommended that a standard time of 1 second be used whenever Stommels equation is applied in neighbor diffusivity problems. Recomputation of data from the literature showed that neighbor diffusivity varied between 0.08 and 1 cm2/sec while time adrift varied between 10 and 108 seconds. Further study of separation rates, as parameters of surface turbulence, is recommended.