Distribution of Cu, Zn, Pb and Cd in some recent molluscan shells from Lake Mariut sediment

Shells and shell fragments were the principal constituents of the core sediment taken from LakeMariut. Their trace metals were studied to assess their contribution to environmental adjustment. The results indicated that the shells of Biomphalaria alexandrina, Mercierella enigmatica and Melanoida tuberculate contain higher amounts of Cu and Zn than the widely distributed shells of Lucina sp. and Cerastoderma edule. The Pb contents found in different types of shells were higher than the other metals. The Cd contents found in different shell types were the most important fraction in comparison to the total Cd in the sediments of the lake. The relationship between the concentrations of trace metals and mineralogical analysis revealed that lead tended to be more concentrated in aragonite than in calcite.

Synecology in soft sediment bivalves: the influence of parasites, physiological processes, and environmental stressors on health and disease

Ecosystem goods and services provided by estuarine and near coastal regions are being increasingly recognised for their immense value, as is the biodiversity in these areas and these near coastal communities have been identified as sentinels of climate change also. Population structure and reproductive biology of two bivalve molluscs, Cerastoderma edule and, Mytilus edulis were assessed at two study sites over a 16-month study period. Following an anomalously harsh winter, advancement of spawning time was observed in both species. Throughout Ireland and Europe the cockle has experienced mass surfacings in geographically distinct regions, and a concurrent study of cockles was undertaken to explore this phenomenon. Surfaced and buried cockles were collected on a monthly basis and their health compared. Age was highlighted as a source of variation between dying and healthy animals with a parasite threshold being reached possibly around age three. Local factors dominated when looking at the cause of surfacing at each site. The health of mussels was explored too on a temporal and seasonal basis in an attempt to assess what constitutes a healthy organism. In essence external drivers can tip the balance between “acceptable” levels of infection where the mussel can still function physiologically and “unacceptable” where prevalence and intensity of infection can result in physiological impairment at the individual and population level. Synecological studies of intertidal ecosystems are lacking, so all bivalves encountered during the sampling were assessed in terms of population structure, reproduction, and health. It became clear, that some parasites might specialize on one host species while others are not so specific in host choice. Furthermore the population genetics of the cockle, its parasite Meiogymnophallus minutus, and its hyperparasite Unikaryon legeri were examined too. A small nucleotide polymorphism was detected upon comparison of Ireland and Morocco.