Is metal pollution a threat to the continued survival of the starfish in False Bay, South Africa?

Abstract

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.

’n Vergelykende ondersoek na die akkumulering van metale in die mosselkrewel (<i>Tetraclita serrata</i>) en die swartmossel (<i>Choromytilis meridionalis</i>) in Valsbaai, Suid-Afrika

“…Valsbaai is geleë by 34˚15`S, 18˚40`O aan die suidpunt van Afrika (Figuur 1) en is die grootste egte of natuurlike baai in Suid-Afrika (Heinecken, Bickerton & Heydon 1983). Vis en skulpvis word in die baai geoes deur kommersiële en bestaanvissers (Van der Merwe et al 1991) en verskeie watersportsoorte word beoefen (Reinecke & Reinecke 2013;Taljaard et al 2000). Verskeie pypleidings stort steeds stygende volumes riool, visafval of industriёle afval in die mariene omgewing.…”

“…Reinecke en Reinecke (2013) wys daarop dat riglyne soos dié en andere(Fatoki & Mathabahta 2001;Maritz & Swanepoel 1998) baie arbitrêr is en dat basislynmodelle soos deur Newman enWatling (2007) voorgestel, 'n meer verantwoordbare basis bied om metaalverryking in sedimente teenoor basislyndata te beoordeel. Die mate waarin potensiële probleemmetale soos Cd en Pb vanuit die water in die organismes kan akkumuleer, is wel ondersoek deur middel van die biologiese akkumulasiefaktor (BAF), die metaal se konsentrasie in die diereliggaam (Cb) teenoor die konsentrasie in die wateromgewing (Cw) by ekwilibrium (op 'n massa-tot-massa-basis) en weergegee deur BAF = Cb/Cw en uitgedruk as 'n logaritme (sien ookReinecke & Reinecke 2013).…”