A retrospective Markovian model for ecosystem resource flow

Historic ecosystem resource flow is modeled as a retrospective discrete Markov chain to obtain the expected values and variances of compartmental residence times and numbers of intercompartmental transfers that compartmental standing crops have experienced since their latest entry into the ecosystem. The transition probabilities of the proposed retrospective Markovian model are either stationary or time inhomogeneous according to whether a steady state or non-steady state ecosystem, respectively, is analyzed.     

Correlation between bioassay-derived P4501A1 induction activity and chemical analysis of clam (Laternula elliptica) extracts from McMurdo Sound, Antarctica

Variable levels of halogenated aromatic hydrocarbons were measured in clams (Laternula elliptica) collected from McMurdo Sound, Antarctica. Clams collected in and near Winter Quarters Bay contained high levels of organochlorine compounds, particularly polychlorinated biphenyls (PCBs). A strong gradient has been documented in Winter Quarters Bay that been linked to human activities at McMurdo Station. The activity of clam extracts as inducers of P4501A1-dependent ethoxyresorufin O-deethylase (EROD) activity was determined using in vitro bioassays utilizing rat hepatoma H4IIE cells. The extracts which exhibited the highest induction activities were those derived from clams collected in contaminated areas. Additionally, there was an excellent linear correlation between induced EROD activity versus total PCB levels (r²=0.96). The complimentary nature of both the analytical and bioanalytical data confirms the utility of the latter assay and provides a method for estimating the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents in extracts from marine biota.     

Volatile organic inputs from an ocean outfall near Barceloneta,Puerto Rico

Volatile organic compounds (VOCs) discharged from an ocean outfall near Barceloneta, Puerto Rico were found to be present at significant levels (μg/L) in a large area of the Atlantic Ocean north of Puerto Rico. The VOCs in the waste treatment plant effluent, which receives mainly industrial wastes, consisted predominantly of a series of straight and highly branched alkanes between n-C₁₄ and n-C₁₈.     

A note concerning time parameterization of Markovian models of ecosystem flow analysis

A continuous Markovian model of resource flow in a steady state ecosystem model is developed. This model calculates the mean and variance of the frequency of intercompartmental cyclings and duration of compartmental residence times. This model is compared with an analogous discrete Markovian flow model to demonstrate the sensitivity of discrete and continuous ecosystem flow analyses. Appropriate time parameterization of of discrete Markovian flow models is then discussed with special reference to Shannon's theorem of dynamic system sampling.     

A Markovian model for ecosystem flow analysis

Nutrient flow through ecosystems is modeled as a discrete Markov chain whose transition probabilities are stationary or time inhomogenous according to whether a steady state or dynamic ecosystem is modeled, respectively. Expected residence time and number of intercompartmental transfers for a nutrient within a set of compartments are derived. Variances of these random variables are also considered. A measure for ecosystem resource recycling is given as a weighted sum of probabilities.     

THE DETERMINATION OF PRIMARY PRODUCTION IN A STREAM USING AN EXACT SOLUTION TO THE OXYGEN BALANCE EQUATION1

ABSTRACT. A promising technique for recognition of early stages of cultural eutrophication relies on determining production and respiration in streams. The most successful and most widely used method of estimating production of a segment of a stream is the upstream-downstream, diurnal curve method introduced by Odum [1956]. This technique is equivalent to obtaining an approximate solution to the oxygen balance equation. We report here an exact solution of the balance equation as a method for calculating primary production. Data presented by Owens [1966] are analyzed; effects of depth and oxygen saturation are studied. A major advantage of the method described here is that continuous temporal variation of net production may be rigorously handled. The method is shown to be well suited to our ultimate goal of studying energy budgets of streams, and thereby the eutrophication process.     

A NEW METHOD FOR ESTIMATING PRODUCTIVITY IN STANDING WATERS USING FREE OXYGEN MEASUREMENTS1

ABSTRACT: Continuous measures of net productivity at discrete depths in standing waters may be obtained using diurnal free oxygen measurements and estimates of the vertical mixing. If oxygen concentration and vertical mixing are known in a laterally homogeneous water body, the only unknown term in the oxygen mass-balance equation is net productivity. If this is represented by a Fourier series, the equation may be solved and Fourier coefficients selected so that the sum of square errors between the oxygen measurements and predictions of the equation is minimized; the Fourier series then describes the diurnal variation of net productivity.     

Evaporites and continental drift

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