A Novel Formulation for Designing a Monitoring Strategy: Application to the Design of a River Quality Monitoring System

In this work, we propose a technique to automatically optimize the monitoring of any distributed indicator (concentration of a substance along a river, blood pressure of a patient over time, etc.) for which a reliable estimate is previously available. From a mathematical point of view, the problem is based on obtaining a reliable estimate of the chosen indicator (e.g., by numerical simulation), and then solving a multi-objective optimization problem (with mixed real and integer variables) whose solution must provide an efficient and satisfactory monitoring strategy. As an illustrative case, we show the steps to follow in order to implement that strategy when designing a system for monitoring water quality in a river. Finally, we present and analyze the results when applying the proposed technique to study a real case in the Neuse River (North Carolina, USA).     

The rock oyster Saccostrea glomerata as an indicator of trace metals in Hong Kong

An urgent need for a sub-tropical and tropical indicator organism for use in the biological monitoring of pollutants is recognised. To this end, preliminary studies have been undertaken to test the indicator ability of the rock oyster Saccostrea glomerata (=Crassostrea glomerata Gould) for monitoring the trace metals cadmium, copper, iron and zinc. A survey of these trace metals in rock oysters from 54 sites in Hong Kong waters revealed elevated levels of metals in several areas. Profiles of metal abundance in S. glomerata agreed substantially with the distribution of industrial and domestic discharges in Hong Kong, and also with patterns of contamination found in studies of the Pacific oyster Crassostrea gigas and of sediments. Application of POLYDIV statistical analysis to these data has aided their interpretation and confirmed the relationship between known areas of contamination and elevated metal levels in S. glomerata. This oyster, which exhibits an unusually great capacity to accumulate a range of elements from the ambient environment, thus appears to be a reliable indicator organism, and may be of great value in global monitoring studies.     

Discussion of methods of investigating the food of fishes,with reference to a preliminary study of the prey of Gobiusculus flavescens (Gobiidae)

The validity, reliability and practicability of different methods for the investigation of stomach contents of a small, plankton-eating fish are discussed. Tests demonstrated the problems related to mass and volume measurements of planktonic food. Several nutrition indices, particularly Hynes's frequency of occurrence are criticized. A logarithmic version of Shorigin's index is proposed as a replacement for Ivlev's food selection index. A preliminary study on the food of Gobiusculus flavescens (Fabricius), sampled in July, 1975 at Helgoland, provides some numerical information on the composition of its stomach contents and food preference.     

Toxic effects of heavy metals upon cultures of Uronema marinum (Ciliophora: Uronematidae)

The lethal levels of mercuric, lead and zinc chlorides were determined for the marine ciliated protozoan Uronema marinum Dujardin; the 24 h LC₅₀ values were 0.006, 60 and 400 mg l^-1, respectively. A factorial experiment was used to study the inhibition of cell division in U. marinum cultures by mixtures of mercury, lead and zinc. The three metals were found to interact in their effects. A regression model was fitted to the experimental results and the response surface was plotted. The addition of mercury, lead or zinc at concentrations which inhibited cell division did not appear to affect the duration of the lag phase or the yield of cells. A culture of U. marinum was maintained for 18 weeks in a medium containing mercury, lead and zinc in an attempt to acclimatise the ciliates to heavy metals. A subsequent factorial experiment which examined the cell division rate indicated that a prolonged exposure did not induce in the ciliates a measurable tolerance to the metals.     

Immunological methods for food web analysis in a soft-bottom benthic community

Basic to nearly any prediction concerning the behavior and structure of entire communities or of their components is knowledge of trophic connections among species. A major impediment to such understanding of soft-bottom benthos is methodological. Because none of the routinely available methods of food web analysis (e.g. visual gut content analysis, direct observation of feeding, tracer techniques) is generally suitable for examining all trophic interactions of benthic infauna, we rought to evaluate the potential of immunological methods for identifying predatorprey relationships in one typical, estuarine, intertidal sand flat. Whole-organism extracts of individual macro- and meiofaunal taxa were injected into rabbits to produce antisera of varying specificity. Double immunodiffusion precipitin tests of antiserum specificity revealed both phyletic and trophic relationships among 20 taxa. Using relatively unspecific antisera, preliminary analysis of the stomach contents of a few surface deposit-feeders and particle browsers was successful, giving positive identification of several trophic links which would otherwise have gone undetected. The production of taxon-specific antisera is expected to provide the methodological tool necessary to document the breadth of trophic connections in a marine benthic food web.     

Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. I. Accumulation from seawater and a food source

The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, 1 and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and 0.0412 mg Cd g^-1 dry weight after 40 days exposure to 0.1 and 1 ppm Cd, respectively, and 0.1115 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of obsorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.     

Some features of the bioluminescence of the radiolarianThalassicolla sp.

The luminescence of the solitary radiolarianThalassicolla sp. has a spectral emission maximum at 446±4 nm and the luminescence of crude homogenates can be activated by calcium ions. Electrical stimulation of single individuals frequently causes them to produce repetitive post-stimulus flashing akin to that reported in a number of other marine animals. The possible relationships between the luminescent system ofThalassicolla sp. and of certain coelenterates are discussed.     

Temporal persistence of biological patch structure in an abyssal benthic community

An analysis of living and dead components of a population of deep-sea agglutinated Foraminifera reveals that both segments of the fauna are dispersed nonrandomly on a scale of centimeters. Significant positive correlations between the distribution of living and dead individuals in several species imply that small-scale patch structure in this environment may persist for more than one generation. Mechanisms maintaining such structure may include habitat selection and reproductive patterns and suggest that dispersion pattern is the result of an active interaction between amimals and a heterogeneous physical and biotic environment.     

Hydrocarbons in benthic algae from the eastern Gulf of Mexico

Thirty-six samples of benthic algae were collected from the continental shelf along the eastern Gulf of Mexico. The algae contain 82.8±143 ppm aliphatic hydrocarbons by dry weight and 11.8±22.7 ppm aromatic and polyolefinic hydrocarbons. The aliphatic constituents of red algae are composed almost entirely of n-C₁₇ (70 to 95% of aliphatic weight); green algae have varying amounts of n-alkanes in the range of n-C₁₅ to n-C₁₉, with homologous series of odd carbon number n-alkenes. Phytadienes occur as high as 740 ppm dry weight in the green algae and do not appear to be related to time or place of collection or to presence of any petroleum pollutants. The single brown algal species contains predominantly n-C₁₅. About 30% of the samples have hydrocarbons resembling degraded petroleum residues, but no petroleum pollution of recent origin was detected in any specimen.