Recent trends in the prevalence of neoplasia in the Baltic clam Macoma balthica (L.) from the Gulf of Gdańsk (Baltic Sea)

This study discusses the occurrence of neoplasia in the Baltic clam Macoma balthica from the Gulf of Gdańsk in recent years and investigates potential relationships between toxic compounds in the environment and the presence of the cancer. The disease was identified at four sampling stations during 1999–2002. Comparison with previous results highlighted the substantial prevalence of the tumour between 1998 and 2002. The prevalence of the cancer was strongly dependent on the sampling location (p < 0.001): it was highest at sampling point H45 (the deepest part of the gulf) and lowest at station PB30 (central part of the gulf). Monthly studies showed a trend towards an increasing prevalence of neoplasia during the warm months. However, over several sampling months no strong statistical correlation between the prevalence of the disease and the sampling time was found. The results of the study suggest that several environmental factors may promote the progress of the cancer in M. balthica from the Gulf of Gdańsk: it is most probably an indirect effect of pollution, although causality cannot be proven at this stage. Seriously polluted and exhibiting a considerable asymmetry of contamination, the ecosystem of the gulf provides an ideal environment for testing potential cause-effect relationships between pollutants and their biological effects.