An environmental parasitological approach to marine metal pollution : the endemic South African intertidal klipfish, Clinus superciliosus, as model organism

Abstract

With multiple species, particularly small bodied organisms such as parasites, still undescribed from the marine realm, new studies investigating novel taxa are highly encouraged. Linking this marine biota, such as cryptofauna, to ecosystem functions is of even greater importance. Past parasite studies, specifically in South Africa, have focussed on taxonomic descriptions. Even though their vital contribution to ecosystems have been established in other regions, this information is lacking for local species. In addition, local parasite taxonomists are scarce in South Africa. In contrast to the interactive role of parasites in ecosystems along the South African coast, contamination by metallic elements has received some attention over the last century. The next step to an integrated approach to ecosystem health would be to combine the knowledge of parasites and contamination by using environmental parasitology. The primary aim of the present study was thus to ascertain the role of parasites as effect indicators in the marine environment. This was accomplished by conducting host-specific parasite sampling to obtain parasite species infecting Clinus superciliosus, as well as calculating the effect of elemental concentrations and other factors on the parasite community composition. Due to extensive background information available on multiple aspects of their biology, reproduction and diet, the endemic intertidal klipfish Clinus superciliosus (Clinidae), is an appropriate model organism for ecosystem health studies. Based on previous literature, and the results obtained from the present study, it is evident that Clinus superciliosus is host to a conceivable 43 species of parasites. Two of the previously reported taxa were not collected during these surveys, while one of these species, Elthusa xena, has only been reported from outside the current sampling area. Taxa from all of the parasitic groups (Myxozoa, Digenea, Monogenea, Cestoda, Acanthocephala, Annelida, Nematoda, Copepoda, Isopoda) have now been reported to inflect C. superciliosus. The majority of the taxa collected during the present study are new host records, some even novel species. In addition to the taxa found during the present study, various suggestions of possible intermediate and definitive hosts have been considered, from which future opportunities to complete life cycle studies could follow. Octopus vulgaris are considered as a possible host to Proctoeces (Trematoda: Fellodistomidae), and possibly Acanthobothrium (Cestoda: Onchobothriidae) species. It is recommended that the molecular data from larval species are linked to GenBank, where adults from the definitive hosts can be connected to intermediate or paratenic host species to compare their life cycles. Prevalence (P %), mean intensity (MI) and mean abundance (MA) per host were calculated, as well as various indices on infracommunity and component community level, and compared between the various localities. Other factors affecting parasite community composition, such as host and parasite distribution patterns and species occurrences, were investigated. Condition factor (CF), hepatosomatic index (HSI), fish size (measured in grams), parasite life cycle, as well

as water temperature, host sex, and habitat type were considered. Higher water temperatures at the east coast localities, known to increase transmission of parasites, were associated with generally high abundance and diversity. Habitat availability refers to a habitat for intermediate hosts within the intertidal rocky shore, but also to the habitat within the various hosts for parasite species to thrive. This can in turn be linked to host condition, where a lower condition factor can be indicative of a weakened immune system making it easier for certain parasites to infect. These habitat conditions can also induce easy access for parasites, due to the altered hydro-morphology at the Langebaan marina. Metallic element concentrations (As, Cd, Cu, Fe, Mn, Pb, Sb, Sn, Zn) detected in the selected host species, Clinus superciliosus, were regarded as naturally high, due to upwelling, geogenic weathering and larger scale oceanographic processes. From these results sources such as antifouling paints in harbours and marinas, the nearby naval base, and transport by season water currents within the False Bay area, were identified as hotspots. When compared to other monitoring species, the concentrations from the present study were lower, and were attributed to different exposure routes. The short- and long-term exposure of these organisms were also measured by considering the different tissues (muscle and liver) analysed. Evidently Cu and Sn were shown to be a short- to long-term hotspot at Simons Town marina and Cape Town harbour, which may also be attributed to the antifouling paints used within the harbour, marina and the naval base. During the present study, it was apparent that very little ecotoxicological studies are conducted on intertidal fish species along the South Africa coast, and combined with similar studies, these results can contribute to national marine pollution monitoring programmes. Parasites are herein regarded as effect indicators of natural conditions and anthropogenic pressures. Several parasitic groups are considered as useful monitoring tools in ecosystem health studies. In particular, it was noted that acanthocephalans and cestodes associated with high concentrations of elements at the two east coast localities. This is in accordance with previous studies. Host condition at the various localities reflected these high concentrations. However, the concentrations were not considered as detrimental to these species. The lower condition factor at Tsitsikamma and Chintsa is rather attributed to the highly kinetic nature of these habitats compared to the anthropogenically altered habitat on the west coast. In addition to host condition, it was also evident that the altered habitat conditions caused changes to the ecosystem structure with reduced habitat availability for intermediate host species. The conclusion from these results was that high metallic element concentrations are not always a result from “pollution”, but in some cases due to naturally occurring high background concentrations to which taxa can adapt over time. The term “pollution” should rather be disentangled during future studies to determine the sources of, for example eutrophication, habitat degradation and overexploitation at anthropogenically impacted localities, compared to Marine Protected Areas and areas of

conservation where these activities are banned, causing species population decline and loss of ecosystem function.