Carole A. Lembi

The Effects of Vegetation Removal by Grass Carp on Water Chemistry and Phytoplankton in Indiana Ponds

Abstract Water quality parameters and phytoplankton in ponds stocked with grass carp, Ctenopharyngodon idella (test ponds) and in control ponds were compared during the summers of 1975 and 1976. Grass carp rapidly consumed available aquatic vascular plants. Dissolved oxygen levels in test ponds remained high as long as bottom growths of the filamentous green alga, Spirogyra sp. were present, but consumption of this alga in addition to vascular vegetation led to significantly lower dissolved oxygen concentrations in the water directly above the sediments. The most consistently affected parameters were turbidity and potassium concentrations, both of which were significantly higher in test ponds. Phytoplankton populations consisting primarily of dinoflagellates were not affected by grass carp introduction. As much as 54% of the phosphorus and 42% of the nitrogen released by consumption of plants were incorporated into new fish tissue. Most of the phosphorus not taken up by the fish was sequestered into compo...

PHYSIOLOGICAL RESPONSES TO TEMPERATURE AND IRRADIANCE IN SPIROGYRA (ZYGNEMATALES, CHAROPHYCEAE)1

Spirogyra Link (1820) is an anabranched filamentous green alga that forms free‐floating mats in shallow waters. It occurs widely in static waters such as ponds and ditches, sheltered littoral areas of lakes, and stow‐flowing streams. Field observations of its seasonal distribution suggest that the 70‐μm‐wide filament form of Spirogyra should have a cool temperature and high irradiance optimum for net photosynthesis. Measurements of net photosynthesis and respiration were marie at 58 combinations of tight and temperature in a controlled environment facility. Optimum conditions were 25°C and 1500 μmol photons m−2 s−1, at which net photosynthesis averaged 75.7 mg O2 gdm−1 h−1. Net photosynthesis was positive at temperatures from 5° to 35°C at most irradiances except at combinations of extremely low irradiances and high temperatures (7 and 23 μmol photons m−2 s−1 at 30°C and 7, 23, and 35 μmol photons m−2 s−1 at 35°C). Respiration rates increased with both temperature and prior irradiance. Light‐enhanced respiration rates were significantly greater than dark respiration rates following irradiances of 750 μmol photons m−2 s−1 or greater. Polynomials were fitted to the data to generate response surfaces; such response surfaces can be used to represent net photosynthesis and respiration in ecological models. The data indicate that the alga can tolerate the cool water and high irradiances characteristic of early spring but cannot maintain positive net photosynthesis under conditions of high temperature and low light (e.g. when exposed to self‐shading).

EFFECTS OF TEMPERATURE AND IRRADIANCE ON THE SEASONAL VARIATION OF A SPIROGYRA (CHLOROPHYTA) POPULATION IN A MIDWESTERN LAKE (U.S.A.)

Although Spirogyra Link (1820) is a common mat‐forming filamentous alga in fresh waters, little is known of its ecology. A 2‐year field study in Surrey Lake, Indiana, showed that it grew primarily in the spring of each year. The population consisted of four morphologically distinct filamentous forms, each exhibiting its own seasonal distribution. A 45‐μm‐wide filament was present from February to late April or early May, a 70‐μm‐wide form was present from late April to mid‐June, a 100‐μm‐wide form was present from February to mid‐June, and a 130‐μm‐wide form appeared only in February of 1 of 2 study years. The 70‐ and 100‐μm‐wide forms contributed to the peak amount of biomass observed in late May and early June. Multiple regression analysis indicated that the presence of the 45‐, 70‐, and 100‐μm‐wide forms was negatively correlated with temperature. Presence of the 130‐μm‐wide form was negatively correlated with irradiance. Isolates of these filament forms were exposed to temperature (15, 25, and 35° C)/irradiance (0, 60, 200, 400, 900, and 1500 μmol·m−2·s−1) combinations in the laboratory. Growth rates of the 45‐μm‐wide form were negative at all irradiances at 35° C, suggesting that this form is susceptible to high water temperatures. However, growth rates of the other forms did not vary at the different temperatures or at irradiances of 60 μmol·m−2·s−1 or above. Net photosynthesis was negative at 35° C and 1500 μmol·m−2·s−1 for the 100‐ and 130‐μm‐wide forms but positive for the 70‐μm‐wide form. All forms lost mat cohesiveness in the dark, and the 100‐ and 130‐μm‐wide forms lost mat cohesiveness under high irradiances and temperature. Thus, the morphological forms differed in their responses to irradiance and temperature. We hypothesize that the rapid disappearance of Spirogyra populations in the field is due to loss of mat cohesiveness under conditions of reduced net photosynthesis, for example, at no to low light for all forms or at high light and high temperatures for the 100‐ and 130‐μm‐wide forms. Low light conditions can occur in the interior of mats as they grow and thicken or under shade produced by other algae.

THE FINE STRUCTURE OF THE FLAGELLAR APPARATUS OF CARTERIA1,2

The fine structure of the flagellar apparatus of 5 species of the green quadriflagellate alga Carteria is described. The 5 species can be morphologically separated into 2 groups on the bases of cell shape and ultrastructure of the pyrenoid and flagellar apparatus. Group I cells are spherical, possess many pyrenoid thylakoids, and retain a flagellar apparatus similar to that of Chlamydomonas reinhardi. The flagellar bases are oriented at approximately 90° to one another, have distal and proximal fibers, and are associated with 4 cruciately arranged microtubule bands. Cells of group II are ellipsoid, possess few pyrenoid thylakoids, and show a complex system of microtubule bands and sigmoid‐shaped, electron dense rods which extend between opposite pairs of basal bodies. The basal bodies of group II cells are directed inward in a circular pattern rather than outward as in group I cells. Unlike Chlamydomonas, the distal fiber of the Carteria species is nonstriated. The proximal fiber is striated, and both distal and proximal fibers are composed of 60–80 Å diameter microfibrils.

The fine structure of the flagellar apparatus of Carteria

The fine structure of the flagellar apparatus of 5 species of the green quadriflagellate alga Carteria is described. The 5 species can be morphologically separated into 2 groups on the bases of cell shape and ultrastructure of the pyrenoid and flagellar apparatus. Group I cells are spherical, possess many pyrenoid thylakoids, and retain a flagellar apparatus similar to that of Chlamydomonas reinhardi. The flagellar bases are oriented at approximately 90° to one another, have distal and proximal fibers, and are associated with 4 cruciately arranged microtubule bands. Cells of group II are ellipsoid, possess few pyrenoid thylakoids, and show a complex system of microtubule bands and sigmoid‐shaped, electron dense rods which extend between opposite pairs of basal bodies. The basal bodies of group II cells are directed inward in a circular pattern rather than outward as in group I cells. Unlike Chlamydomonas, the distal fiber of the Carteria species is nonstriated. The proximal fiber is striated, and both distal and proximal fibers are composed of 60–80 Å diameter microfibrils.

The effect of small-scale fluid motion on the green alga Scenedesmus quadricauda

The effect of shear flow on the green alga Scenedesmus quadricauda grown in Bristols medium wastested. The shear flow was generated using a Couettetype rotating cylinder apparatus. Growth of Scenedesmus quadricauda, measured in terms ofchlorophyll a concentration, was inhibited underdifferent fluid motions. Inhibition was mostpronounced at high Reynolds number (Re) and thecorresponding mean rate of energy dissipation(ε). Algal growth was maximum during thestagnant fluid flow experiment. The flocs comprised of dead and living cells of algae formed as a resultof shear flow. Cell morphometry did not changeconsistently under different flow conditions but celldestruction was evident. A two step model isproposed, relating algal growth as a function of Re,and ε. The attenuation factor, φF for growth limiting conditions underdifferent fluid motions, was defined as the ratio of the algal growth rate constant to the maximum algalgrowth constant under stagnant fluid flowconditions.

FACTORS REGULATING THE SPATIAL DISTRIBUTION OF THE FILAMENTOUS ALGA PITHOPHORA OEDOGONIA (CHLOROPHYCEAE) IN AN INDIANA LAKE1

Pithophora oedogonia (Mont.) Wittr. biomass in Surrey Lake, Indiana was greater in the littoral than in the pelagial region. Although mean soluble reactive phosphorus concentrations did not differ between the two areas, nitrate concentrations were almost six times higher in the cove than in the open water. Using laboratory cultures of Pithophora, the half saturation constant (Ks at 20° C relating filament growth to external concentrations of nitrate‐nitrogen was determined to be 1.23 mg L−1 (=88 μM)and for phosphate‐phosphorus, 0.1 mg L−1 (=3.22 μM). These values were used to calculate a NO3‐N/PO4‐P atomic ratio of 27.6. Comparison of this value with NO3‐N/PO4‐P ratios in Surrey Lake showed that nitrogen limiting conditions were prevalent in the open water section of the lake. Alkaline phosphatase and dark ammonia uptake analyses on field collected filaments from the shallow and deep water sections confirmed the hypothesis that nitrate is the major factor limiting growth of Pithophora in Surrey Lake.

A RHIZOPLAST IN CARTERIA RADIOSA (CHLOROPHYCEAE)12

A rhizoplast or rhizoplast‐like structure was observed with the electron microscope in Carteria radiosa. The cross‐banded structure extends from the proximal end of each of at least 2 of the basal bodies and extends toward, although does not make contact with, the nucleus. The rhizoplast terminates in a ribosome‐free area composed of fine granules and microfibrils. This is the first ultrastructural verification of a rhizoplast in a volvocalean alga.

STRUCTURE AND COMPOSITION OF PITHOPHORA OEDOGONIA (CHLOROPHYTA) CELL WALLS1

Carbohydrates, amino acids and other cell wall components of Pithophora oedogonia (Montagne) Wittrock were identified by physical, biochemical, and cytochemical techniques as well as by light and electron microscopy. The major polysaccharides of P. oedogonia cell walls were cellulose and chitin. In addition to N‐acetylglucosamine and glucose, N‐acetylgalactosamine, galactose, arabinose, fucose, mannose, xylose, and galacturonic acid were the other sugars, amino sugars, and sugar derivatives detected. The carbohydrate content of the cell walls was estimated to be 65% non‐nitrogenous hexose and 6% chitin. Chitin was present in the crosswall disks and outer wall, whereas cellulose was confined to the inner wall. Protein and N‐ acetylgalactosamine were concentrated in the chitin‐rich wall fraction. The location of chitin in P. oedogonia cell walk is suggested as a basis for morphological differences between the two genera, Cladophora and Pithophora.

PHOSPHOTUNGSTIC ACID‐CHROMIC ACID: A SELECTIVE STAIN FOR ALGAL PLASMA MEMBRANES1,2

A phosphotungstic acid‐chromic acid mixture selectively stains the plasma membrane of whole cells of selected members of the Chlorophyceae, Charophyceae, Euglenophyceae, Xanthophyceae, Bacillariophyceae, Chrysophyceae, and Rhodophyceae, and the plasma membrane in cell‐free fractions of Mougeotia (Chlorophyceae). The procedure is not effective on the plasma membrane of the cyanophycean Scytonema or the cyanophycean endosymbiont of Glaucocystis. Staining of the cell walls of Chlamydomonas, Bangia, and Scytonema and the pellicle and sliding junction of Euglena and Astasia suggest that PTA‐CrO3 reactivity may be associated with glycoproteins in the cell walls and plasma membranes.