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n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Sellulêre biomerkerresponse as maatstaf van gevoeligheid van klipmossels (Mollusca) vir kadmiumbesoedeling

Volume 27, Issue 2
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173

Abstract


Due to the availability and chemical nature of some heavy metals, sub-lethal toxicant levels may persist in the ocean waters and may cause physiological problems and toxicity in invertebrates and other marine organisms. Although studies of metal concentrations in False Bay showed relatively low mean concentrations of Cd, invertebrates such as molluscs, crustaceans and many other groups are able to accumulate high levels of heavy metals in their tissues and still survive in the heaviest polluted areas. They can accumulate numerous pollutants from natural waters in quantities that are many orders of magnitude higher than background levels. Bioaccumulation of cadmium in intertidal species could cause stress which may be measurable at the cellular level. A variety of limpet species that may serve as suitable ecotoxicological monitoring species occur in abundance on rocky shores along the South African coastline. The aim of this study was to obtain sensitivity data which could contribute to the selection of a suitable monitoring species and the eventual establishment of a species sensitivity distribution model (SSD) with a biomarker response as endpoint. The limpets and as well as water samples were collected at two localities in False Bay, South Africa. Analysis of water and biological samples were done by atomic absorption spectrometry. Exposures were done to three different sublethal concentrations of cadmium in the laboratory in static flow tanks over three days. There was a moderate increase in cadmium body concentrations over time. Results obtained at three exposure concentrations showed no significant differences in metal concentrations between the different samples. Significant differences were obtained between the control and the exposure groups for each exposure time except between the control and the 1mg/L CdCl exposure group after 24 and 72 hours of exposure. Cd body concentrations (soft tissue) varied between 4.56 and 21.41µg/g (wet mass).
Mean Cd concentrations in soft tissue of was considerably lower (varying between 1.18 and 19.58 µg/g Cd ) than in the tissues of . The control group differed significantly from the 0.8 and 1 mg/L CdCl exposures after 48 and 72 hours.
Mean Cd body concentrations in were the highest of all exposed species, reaching a level of 148 µg/g Cd at the highest exposure concentration and differed significantly from the means of the other samples of the 0.8 mg/L CdCl exposure group after 72 hours and from the 1 mg/L CdCl group after 24 hours. Significant differences were also obtained between the Cd body concentrations of for the three exposure concentrations and three exposure times.
Lysosomal membrane integrity was determined for both exposed and control animals, using the neutral red retention assay. Three of the four species showed a significant decrease in retention times with an increase in Cd concentration. Inter-species differences in sensitivity to environmentally relevant cadmium concentrations were reflected in the biomarker responses. Based on reduction of NRR times, the order of relative sensitivity to cadmium was .

Die bioakkumulasie van kadmium in tussengetyspesies kan stres veroorsaak wat op sellulêre vlak meetbaar is. Verskeie klipmosselspesies kom volop op rotse aan die Suid-Afrikaanse kuslyn voor en kan moontlik vir ekotokiskologiese monitering gebruik word. Die oogmerk van die studie was om sensitiwiteitsdata te verkry wat kan bydrae tot die kies van 'n geskikte spesie vir monitering en die uiteindelike daarstelling van 'n model vir spesie sensitiwiteitsverspreiding (SSV) wat 'n biomerkerrespons as eindpunt gebruik. Die klipmossels en en watermonsters is in Valsbaai versamel. Analises van kadmium in water en biologiese monsters is met behulp van atoomabsorpsiespektrofotometrie uitgevoer. Blootstellings van organismes aan subletale vlakke van kadmium is uitgevoer in statiese vloeitenks oor 'n periode van drie dae. Daar was 'n matige toename in liggaamskonsentrasies van kadmium oor tyd. Resultate wat by drie blootstellingskonsentrasies gekry is, het geen betekenisvolle verskille in metaalkonsentrasies tussen die verskillende monsters uitgewys nie. Betekenisvolle verskille tussen die kontrole en die blootstellingsgroepe vir elke individuele blootstellingstyd is vir die spesie verkry behalwe tussen die kontrole en die 1mg/L CdCl blootstellingsgroep na 24 en 72 uur van blootstelling. Cd liggaamskonsentrasies (sagteweefsel) het tussen 4.56 en 21.41µg/g (nat massa) gevarieer.


Gemiddelde Cd konsentrasies in sagteweefsel van was aansienlik laer (variërend tussen 1.18 en 19.58 µg/g Cd ) as in weefsel van . Die kontrolegroep van hierdie spesie het betekenisvol verskil van die 0.8 en 1 mg/L CdCl blootstellings na 48 en 72 uur.
Gemiddelde Cd liggaamskonsentrasies in was die hoogste van al die blootgestelde spesies en het 'n vlak van 148 µg/g Cd by die hoogste blootstellingskonsentrasie bereik en het betekenisvol verskil van die ander monsters se gemiddeldes met die uitsondering van die 0.8 mg/ L CdCl blootstellingsgroep by 72 uur en die 1 mg/L CdCl groep by 24 uur. Betekenisvolle verskille is ook verkry vir die liggaamskonsentrasies van Cd van tussen die drie verskillende blootstellingskonsentrasies en drie blootstellingstye.
Integriteit van lisosoommembrane is bepaal met behulp van die neutraalrooi retensiemetode. Drie van die vier spesies het 'n betekenisvolle afname in retentsietye getoon met 'n toename in Cd konsentrasie. Tussenspesieverskille in gevoelighede vir omgewingsrelevante kadmiumkonsentrasies is deur die biomerkerresponse uitgewys. Gebaseer op die verlaging in NRR tye, is die volgorde van relatiewe gevoeligheid vir kadmium as volg: .

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/content/aknat/27/2/EJC20425
2008-06-01
2019-12-09

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