Clyde E. Goulden

COMBO : a defined freshwater culture medium for algae and zooplankton

In order to conduct experiments on interactions between animals and food organisms, it is necessary to develop a medium that adequately supports the growth of both algae and zooplankton without the need to alter the medium to accommodate either the algae or the animals. We devised a freshwater medium, named COMBO, that supports excellent growth of both algae and zooplankton. Two types of algae, Ankistrodesmus falcatus and Stephanodiscus hantzschii, were reared in COMBO and their growth rates were not significantly different from those of algae grown in a reference medium (WC). One of these algae, A. falcatus, was then fed to a cladoceran, Daphnia pulicaria, which was also cultured in COMBO, and the resulting fecundities of D. pulicaria were compared to those of animals reared in natural surface water. We also determined whether the value of COMBO as a medium for D. pulicaria was affected by modifications in nitrogen or phosphorus concentration to evaluate whether the new medium will be useful in nutritional research. Lowering the N or P content of COMBO did not affect the reproductive performance of D. pulicaria. Other researchers have also reported excellent growth and reproduction by numerous algae and zooplankton reared in COMBO. Our results suggest that COMBO is an effective artificial, defined culture medium capable of supporting robust growth and reproduction of both freshwater algae and zooplankton.

Body Size, Energy Reserves, and Competitive Ability in Three Species of Cladocera

The purpose of this study was to identify mechanisms of competitive ability among planktonic Clodocera. We used three species (Daphnia magna, Daphnia galeata, and Bosmina longirostris) in life—table and birth—schudle experiments to analyze the effect of low food levels on each population, and in competition experiments. Demographic traits of all species were affected by low food levels, but the smaller species suffered higher death rates. D. magna matured and reproduced well in the lowest food level studied; growth rate of the population was 0.143 d—1. Survivorship for D. galeata cohorts was poor at the lowest food level but many animals did mature and reproduce; population growth rate was 0.082 d—1. Few Bosmina individuals matured and reproduced and all were dead by the third adult instar; the population growth rate was —0.136 d—1. In the competition experiments, D. magna was the numerical dominant in high—food cultures with D. galeata, and D. galeata was the numerical dominant in cultures with Bosmina. ...

Lipid Dietary Dependencies in Zooplankton

Zooplankton accumulate large amounts of lipids, as much as 40-70% of the dry mass of their body (Goulden and Henry, 1985; Lee et al., 1972) ome polyunsaturated fatty acids and sterols are essential but required in trace amounts. By contrast, storage and membrane lipids are generally composed of nonessential lipids and make up an important energy reserve.

The dynamics of age-structured populations with a gestation period: density-independent growth and egg ratio methods for estimating the birth rate

Abstract We pose and analyze a new demographic model which includes embryo abundance and a gestation period. All vital rates are fully age-dependent but do not depend on population density. We demonstrate convergence to a stable age configuration, characterize that configuration, and derive expressions for important population attributes such as the Malthusian parameter and net reproductive rate. We then use the model in two ways. First we examine effects of a gestation period on the population growth rate and the nature of population waves. Then we deduce a variety of simple birth rate estimators which can be applied to field populations. These include nearly all the existing egg ratio methods, and several new ones, as well.

Declines in diversity of crane flies (Diptera: Tipuloidea) indicate impact from grazing by livestock in the Hövsgöl region of Mongolia

Threats to biodiversity are not studied equally amongst taxa leaving some groups like insects typically understudied in conservation and management research. Crane flies (Diptera: Tipuloidea) are diverse and important members of the aquatic and terrestrial biotic communities. These semi-terrestrial larval habitat preferences place crane flies at risk of habitat degradation and loss particularly from grazing by livestock. Increased grazing by livestock in the Hövsgöl region of Mongolia has impacted both terrestrial and aquatic ecosystems. The purpose of this study is to document biodiversity of crane flies along the east shore of Lake Hövsgöl, Mongolia, and to test whether crane fly diversity differs between valleys with different grazing intensity. Ninety-six species of Tipuloidea were found in this study, nine of these new to Mongolia, with 21 new to the Hövsgöl region. Rarefaction curves indicate that predicted diversity is less for moderately and highly grazed valleys than for the lightly grazed valleys and an analysis of variance indicates that Shannon’s diversity index was significantly higher in the lightly grazed valleys. Finally, a parsimonious model based on multiple regression analysis indicates that plant biomass and relative humidity are the strongest significant predicators of variation in crane fly diversity across the grazing gradient. Since crane fly larvae are an important part of the soil and leaf litter community, impaired diversity may affect ecosystem services such as decomposition of leaf litter and bioturbation, potentially exacerbating the impact of grazing.

Spatial heterogeneity in macroinvertebrate density from Lake Hövsgöl, Mongolia

Lake Hovsgol is a large, ancient, asymmetrical grabenlake located in north central Mongolia. The lake is longalong its north/south axis and the west shore of the lake islined by steep mountains with little human activity; where-as the east shore of the lake is lined by shallow hills char-acterized by pastoral land use. Lake Hovsgol is a pristinelake with high concentrations of dissolved oxygen, lowconcentrations of nutrients, and deep blue color(Kozhova