Thesis record

Volume 21/Number 8/August 1990 disease, and thereby indicate whether fish disease is an effective monitor of pollution. When the different elements of the Benthic Triad (community structure, sediment bioassay and sediment chemistry) come together it will be possible to say how effective each one is as an indicator of benthic environmental quality, or whether some integrated index is preferable. The first results show considerable coherence in indicating a progressive improvement in sediment and water quality offshore, demonstrating that not only are many of the techniques sensitive enough to detect the contamination gradient, but that they are apparently responding to the same set of factors. An unexpected finding was that several of the techniques indicated a

decline in water quality at the most offshore stations over the Dogger Bank. Although there exist some chemical data (e.g. lead associated with particulate matter) indicating elevated concentrations of contaminants in the central southern North Sea, interpretation requires the Workshop chemical data, and will probably require further study of the processes involved. A preliminary report for the Workshop is available, and the full account will be published in Marine Ecology Progress Series in Spring 1992. A Workshop Symposium, at which all those involved will present an account of their findings, will be held at ICES in Copenhagen in September 1991. A. R. D. S T E B B I N G

Edited by D. V Ellis Marine Pollution Bulletin will publish records of university theses relevant to marine pollution in the format shown below. Theses can be from any relevant discipline such as Biology, Chemistry, Engineering, Medicine, Economics, etc. Contributions should be 50-100 word descriptions of thesis content, with emphasis on the marine pollution aspects. They should be sent to the Thesis Record editor (Dr. D. V. Ellis, Biology Department, University of Victoria, Victoria, B.C., Canada V8W 2Y2), with a copy of the officially endorsed thesis title page and abstract. Copy of a title page alone may be submitted (by any interested person) in which case the record will consist of author, year, title, degree, university and supervisor. Contributions should be for theses accepted for M.Sc. or Ph.D. degrees during the past five years, although in exceptional circumstances a contribution recording an older thesis will be accepted for publication. M~CALLEF, S. 1988. Aspects of mercury/selenium interaction in the bivalve Mytilus edulis. Ph.D. University College of Swansea. (Supervisor: Dr. P. A. Tyler). A series of laboratory experiments have been conducted to study the interactive effect of mercury and selenium on some functional responses of the adult mussel, Mytilus edulis. A survey has also been undertaken to investigate whether any relation exists between the levels of mercury and selenium in mussels found in natural populations exposed to different types of pollution. The chemical analysis in the survey was also extended to include the other G r o u p IIB metals. Acute lethal toxicity tests showed the simultaneous addition of selenium on an equimolar basis with mercury provided best protection but the result could not be considered true evidence of an antagonism. Simultaneous addition of a high concentration of selenium proved to be more toxic than the mercury treatment alone. Analysis of the mercury in the soft tissues in the mussels showed that some form of mercury-selenium interaction did take place. Simultaneous addition of a low concentration of selenium on an equimolar basis with mercury did not produce a redistribution of mercury in the three tissues analysed for mercury accumulation.

Under short-term sublethal exposure, the filtration rate of mussels was reduced drastically in the presence of mercury. Selenium in an equimolar or equidosal concentration did not counter this reduction. Of the three processes measured associated with feeding and respiration, the filtration rate was the most sensitive to chemical stress. Long term chronic exposure of mussels to mercury, selenium and an equidosal combined treatment provoked degenerative changes in the reproductive follicles. Quantitative cytological measurements demonstrated that the delay of gametogenesis took place upon exposure to mercury or selenium whilst the combined treatment reduced this delay. The results indicated a lack of agreement between the cytological changes and the anticipated impact based on the metal levels in the mantle tissue. Analysis of the whole soft tissue of mussels under field conditions showed a lack of correlation between cadmium:mercury, mercury:zinc and zinc:selenium but a significant correlation between cadmium:zinc, cadmium:selenium with best correlation between selenium:mercury. Correspondence to."S. Micallef, I.N.R.S.--Eau, C.P. 7500, Sainte Foy. Qurbec, Canada GIV 4C7.

ALAGARSAMY,R. 1989. A Study on Some Metals in the Mandovi Estuary Sediments. Goa. M.Sc. University of Bombay, India. (Supervisor: Dr. R. Sen Gupta) Distribution and seasonal changes of few heavy metals and Total Organic C a r b o n have been studied in the sediments collected from six stations in the Mandovi estuary, Goa, India, Elevated concentration of Fe and Mn in sediments at upstream regions of the estuary indicate dissolution and readsorption of the material resulting from spillage of surrounding ore bearing landmass. The increasing concentration of Cu from the marine to the riverine zone is due to settling of trace metals at the confluence zone. No elevated concentration of Co was observed. Higher concentration of Zn 405

Marine PollutionBulletin and Pb were observed at the mouth region which is due complex, a transect in the southern portion of the Gulf to the input of organic wastes into the estuary through of Mexico and two isolated cores in the western part of the municipal and industrial sewage. High organic the Gulf of Mexico. The results obtained were in good agreement with carbon in the sediments at the marine zone of the estuary is perhaps due to higher plankton and benthic previous estimates of trace metal contents in sediproduction. The low organic carbon content at the mentary pyrite. In order to account for the trace metal upstream regions is due to the probable high oxidation partitioning among the different reactive phases, the of the organic matter and reduction of photosynthetic operationally-defined term degree of trace metal pyritiproductivity caused by mining rejects. The metal con- zation (DTMP) was introduced. This term, used in concentrations are, however, below the levels observed in junction with the degree of pyritization (DOP) was a useful parameter for assessing the transformation of polluted estuaries. Correspondence to: Mr. R. Alagarsamy,ChemicalOceanographyDivi- reactive trace metals to the pyrite phase. Results sion, National Instituteof Oceanography,Dona Paula, Goa-403 004, indicate that all the trace metals considered increased in India. DTMP with increasing DOE However, As, Hg and Mo exhibited a rapid and almost complete incorporation into the pyrite fraction. Several transition metals HUERTA-DIAz, M. A. 1989. Geochemistry of Trace displayed a close to linear increase in DTMP and Metals Associated with Sedimentary Pyrite from moderate pyrite incorporation. Chromium and class B Anoxic Marine Environments. M.S., University of the metals were also gradually incorporated into the pyrite Pacific. (Chair of Advisory Committee: Dr. John W. phase but without reaching the DTMP levels exhibited by the rest of the trace elements. These results indicate Morse). A new method for the quantitative extraction of trace that transition and class B metals exhibit distinctly metals from sedimentary pyrite, derived from the tech- different behaviour that is characteristic of the chemical nique of Lord (1982) for pyrite-Fe measurement, was attributes of these different classes of trace elements. developed. Application of this new method to As, Cd, Analysis of piston core and marsh sediments showed Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb and Zn diagenesis in that high DOP and DTMP values are not a characdifferent sedimentary environments from the Gulf of teristic restricted to Fe-poor, H2S-rich sediments. HowMexico area is presented. The region covered included ever, availability of dissolved trace metals and high sediment cores from a Fe-poor, H2S-rich coastal lagoon organic matter content are apparently important factors on the coast of Texas (Baffin Bay), the Fe-rich, H2S- controlling the incorporation of Co, Cr, Cu, and Ni in poor sediments from the Mississippi-Atchafalaya delta these environments.

Bubble Barrier Worcester company OPD Ltd is now producing its range of anti-pollution 'bubble' barriers in a range of four sizes. The barrier consists of a length of polyethylene tube anchored beneath the water. Non-corrodible nozzles are fed with a supply of compressed air, generating a dense, upward-flowing stream of bubbles which form an impenetrable barrier to floating oil, debris, silt, and other waterborne pollutants, whilst at the same time allowing free passage to shipping and river traffic. The barrier sizes range from 25-100 mm internal diameter and are available in three or six metre lengths. The total length of the barriers may extend beyond 250 m. Air supply can be from existing sources or a compressor, electrically or diesel-driven and sized in accordance with the length of barrier, operational depth and nature of the duty. An optional flotation tube enables the barrier to be brought to the surface for maintenance. The bubble barriers can also be used for a number of other specialized applications, such as the prevention of seawater and freshwater stratification. 406

Hydraulic Motors for New Offshore Booms Environmental control system specialists, Hoyle Marine Ltd have incorporated hydrostatic motors in their new offshore boom systems for the control of oil pollution. The motors are manufactured by Poclain Hydraulics Ltd of Marlow, UK. The unit used is one of a range 'S' Series motors, available in 36 displacements from 175 cc/rev to 1000 cc/rev, the motors are suitable for a wide variety of applications. They have particularly impressive power/weight and power/size ratios-features which ensure their suitability for applications that call for high power and simple operation such as the Ocean range of offshore booms. The booms are designed to enable operators to bring oil spiUages under control in as short a time as possible. (The sooner pollution can be trapped in one place for treatment, the less will be the cost to both the environment and the specialists employed to disperse the contamination.) The result is the Ocean range of lightweight easily handled offshore booms, which are both light and