Hou metaalbesoedeling ’n bedreiging in vir die voortbestaan van seesterre in Valsbaai, Suid-Afrika?

Reinecke, Adriaan J. ; Reinecke, Sophie A. (2013-10-09)

CITATION: Reinecke, A. J. & Reinecke, S. A. 2013. Hou metaalbesoedeling ’n bedreiging in vir die voortbestaan van seesterre in Valsbaai, Suid-Afrika? Suid-Afrikaanse Tydksrif vir Natuurwetenskap en Tegnologie 32(1), Art #394, doi:10.4102/satnt.v32i1.394.

The original publication is available at http://www.satnt.ac.za

Article

Verstedeliking en industriële ontwikkeling rondom Valsbaai, Suid-Afrika, neem toe en kommer het ontstaan oor die uitwerking van besoedelende stowwe op die tussengetydiere soos seesterre. Die oogmerke van die huidige studie was om voorlopige, beskrywende basislyninligting gedurende die verloop van die onderskeie seisoene in 2000–2001 in te samel oor die metaalvlakke in sediment, water en in die liggaam van ’n gekose kussingseester naamlik Parvulastra exigua (Lamarck, 1816) wat wydverspreid in die tussengetygebied van Valsbaai voorkom. Konsentrasies van kadmium, koper, lood, nikkel en sink is in die water, sediment en die liggaam van die kussingseester by vyf verskillende lokaliteite bepaal oor ’n periode van een jaar. Die monsters is chemies ontleed vir spesifieke metaalvlakke met behulp van atoomabsorpsie-spektrofotometrie. Die hoogste individuele konsentrasies van kadmium (Cd) in seesterre en sediment is by die noordelike kusstreek tussen Strand en Muizenberg gemeet waar die meeste industriële aktiwiteit voorkom. Groot variasie in konsentrasies van alle metale wat ontleed is, het tussen versamelpunte en tussen seisoene voorgekom. Die gemiddelde konsentrasies in die water en sediment was in enkele gevalle effens hoër as die vlakke wat deur die Suid-Afrikaanse waterkwalitetisriglyne aanbeveel word, maar steeds benede die perke wat in verskeie ontwikkelde lande gestel word. Dit dui daarop dat die baai tans nog relatief onbesoedeld deur metale is. Huidige omgewingskonsentrasies in sekere dele van Valsbaai kan met verloop van tyd in tussengetydiere akkumuleer tot nadelige vlakke vir die spesies self, maar ook vir hulle predatore. Hierdie studie bied getuienis dat die kussingseesterre in Valsbaai aan verskeie metale blootgestel word, waarvan sommige potensieel gevaarlik is omdat hulle neig om met verloop van tyd in diere te akkumuleer. Risiko-assessering vereis egter bykomende inligting oor die samehang tussen blootstelling en biologiese effekte op sowel sellulêre, organismiese en bevolkingsvlak alvorens ingeligte besluite geneem kan word of die seesterre reeds sodanig bedreig word dat tussenbeide getree moet word.

Urbanisation and industrial development in the catchment area of False Bay in South Africa are increasing and concern was raised about the effect of environmental pollutants on intertidal fauna such as starfish. The aim of the present study was to obtain initial descriptive baseline data over several seasons during 2000–2001 of metal concentrations in water, sediment and body samples of the chosen cushion starfish Parvulastra exigua (Lamarck, 1816) that occurs widely in the intertidal zone of False Bay. Concentrations of cadmium, copper, lead, nickel and zinc were measured in samples of the cushion starfish, water and sediment at five localities along the coast of False Bay. The samples were chemically analysed for metals by atomic spectrophotometry. The highest individually measured concentrations of cadmium (Cd) in starfish and sediment were found in the northern coastal region between Strand and Muizenberg where most industrial activity and human settlement occur. Large variation in concentrations of all metals occurred between localities and seasons. The mean concentrations of Cd and Pb in water and sediment were in a few instances slightly higher than the recommended levels or target values of the South African marine water and sediment quality norms but still lower than those in various developed countries. Indications are that the bay was at the time of this study still less contaminated by metals in comparison with the coastal waters of various other countries. The accumulation of nonessential metals such as cadmium and lead in both sediment and bodies of starfish was nevertheless such that it can be assumed that environmental concentrations in some parts of the bay could over time build up to levels that are detrimental to the species as well as their predators. This study provided evidence that the cushion starfish in False Bay is exposed to several metals of which some are potentially hazardous since they tend to gradually accumulate in animal bodies. Risk assessment, however, requires additional information about the causal relationship between exposure and biological effects at the cellular, organismic and population levels before informed decisions can be made whether the threat to starfish is such that intervention is required.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/94923
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