Biogeochemistry: its origins and development

The history of how aspects of biology, geology and chemistry came together over the past three centuries to form a separate discipline known as biogeochemistry is described under four major headings: metabolic aspects, geochemical aspects, biogeochemical cycles, and the origin of life. A brief chronology of major conceptual advances is also presented.     

Seasonal cycles of reserves in relation to reproduction inSebastes

Synopsis Seasonal cycles of reserve deposition and utilization in many fishes, amphibians and reptiles alleviate temporal mismatches of energy supply and demand. Utilization of reserves can be related to maintenance during periods of reduced food supply, to reproduction, particularly during periods of poor food availability, and to migration. Published data on the seasonal cycles of reserves and reproduction inSebastes suggest that reserves are important for maintenance during wintertime periods of low food availability. Unlike many other ectothermic vertebrates, some species ofSebastes deposit fat reserves at the same time as gametogenesis, a pattern consistent with the longevity and iteroparity evident in the genus. Other species ofSebastes have similar seasonal timing of fat cycles, but since reproduction takes place later in the year, the decline in reserves during winter coincides with the main period of reproductive activity. The significance of this is not clear. Interspecific differences in amounts of reserves may be related to geographical differences in the seasonality or abundance of food. Intraspecific variation in reserves, marked most strongly by allometry of reserves with regard to fish legth, bears further study, since it may link the proces of sexual maturation and the responses of repeat spawners to variability in food supply and other environmental factors.     

Life history of a lacustrine ostracod

The ostracod Cypria turneri has one generation per year in Mirror Lake, New Hampshire. Juveniles hatch in January through May and reach maturity by August. The life history of this ostracod suggests that the turnover rate of the population is low.     

Life history,population dynamics and production of Pontoporeia hoyi (Crustacea,Amphipoda) in relation to the trophic gradient of Lake George,New York

The life history characteristics, population dynamics and production of Pontoporeia hoyi in Lake George, New York, were studied from May 1981 through October 1982. P. hoyi, in terms of both density and standing crop, is the most prevalent member of the deep water macrobenthos of Lake George. It reproduces in the winter, with young being released in the late winter-early spring. At the southernmost study site, young released in the spring grew to 6–7 mm in length and bred during their first winter. At the remaining sites, P. hoyi required two years to complete its life cycle. This difference in life history characteristics can be related to food availability and temperature differences. The open waters of the south end of Lake George are not only more productive but are also more closely associated with the littoral zone, providing a wealth of bacteria-rich detritus for benthic deposit feeders. The greater food availability in the south basin of Lake George is reflected in significantly larger brood sizes and smaller size at maturity for P. hoyi populations from the south end of the lake.The southernmost study site has significantly greater P. hoyi density and standing crop than all other sites. The cohort of the year dominated density and standing crop at the southern site while the cohort of the previous year dominated standing crop at the other sites. Peak abundance ranged from 600 · m^–2 at the north site to 2 900 · m^–2 at the south site. Cohort production ranged from 2g · m^–2 at the north site to 15g · m^–2 at the south site.     

Some aspects of the natural history and food selection ofAvahi laniger

Two groups ofAvahi laniger were studied in the Forêt de Analamozoatra near Perinet in the eastern rainforest of Madagascar from August to October 1984. Overlap between the home ranges of neighbouring groups ofA. laniger was minimal. Group size ranged from one to four individuals with a median group size of two. In four out of ten groups a baby was born between August and September.A. laniger were most active after dusk and before dawn. They had an extended resting period around midnight. Their diet consisted mostly of leaves from at least 17 different plant species. They also ate flowers. Fruit eating was recorded twice. Leaves eaten had high contents of protein and sugar but did not contain alkaloids. The concentration of condensed tannins did not differ between food items and non-food items. There was no indication of competition with other prosimians that might explain their nocturnality.     

Age and growth of a colonizing minnow,Barbus anoplus,in a man-made lake in South Africa

Synopsis Aspects of the life history of Barbus anoplus were studied in Lake le Roux, a turbid man-made lake on the Orange River, South Africa. This minnow underwent a population explosion and successfully colonized the shoreline of the newly-formed lake during the early phases of reservoir filling. Male and female B. anoplus reach sexual maturity in one year at about 40 mm fork length. They have a multiple spawning habit with the first spawning in November–January and the second in February–March. The growth of the two resulting cohorts is discussed. It is proposed that the offspring from the second spawning not only acts as a ‘back-up’ but is capable of prolonging the life of that year-class into an additional reproductive season. Most of the minnows die after their second summer, but more offspring from the second spawning, especially females, live into a third summer. Females attain a larger maximum size (73 mm FL) and age (3–4 years) than males (60 mm FL, 2–3 years). B. anoplus is small and short-lived with a high seasonal reproductive potential, which is in contrast to the larger Barbus species in the Orange River system. These life-history traits enable the species to colonize and successfully inhabit unstable environments and probably account for its widespread distribution.