Trace Metal Residues in Marine Mussels: A Global Survey

The Status of Marine Mussel Pollution Research in South Africa (2012-2022)

The growing human population requires more food each year, and seafood products can help meet this demand if clean water resources are available for their growth. Farmed and wild mussels are environmentally friendly seafood with many health benefits to human consumers, but they can also pose a health risk if they are harvested from areas where marine anthropogenic pollution is uncontrolled or unmonitored. While the coastline in South Africa has long been assumed to be pristine, a growing number of recent studies are raising contamination concerns. Baseline studies establish a wide range of anthropogenic pollutants to be present in the marine environment, specifically in urbanised or industrialised areas like major cities or harbours. This review summarises how mussels could pose health risks to human consumers and the current research that is being conducted by private researchers and institutions in South Africa. The review emphasises the need for more research in the field and for governmental pollution monitoring data to be released to the public.

Spatial variation of cadmium concentration in the bivalve Beguina semiorbiculata (Linnaeus, 1758) from coastal coral reefs of Vietnam

The spatial distribution of trace metals (Fe, Zn, Cu, Cd, Mn, Pb and Ni) in the soft tissues of Beguina semiorbiculata from coastal reefs of Vietnam was studied. Bivalves were collected in May 2013 from 22 sites along the south-eastern coast from Gulf of Thailand to Ha Long Bay. The most increased concentrations of studied metals (excluding Cd) were shown in the B. semiorbiculata living in Ha Long Bay characterized by terrestrial runoff and anthropogenic effects. In contrast, the maximal Cd concentrations were found in the bivalves from coastal reefs of central Vietnam and Gulf of Thailand. Apparently, Cd concentration depends on seasonal upwellings (central part of Vietnam coast) and composition of suspended matter (Gulf of Thailand). Consequently, Cd distribution in the coastal waters of Vietnam should be strongly controlled in relation with predicted risk of climate change that may further significantly increased Cd bioavailability for habitants of coral reefs.

Natural heavy metal concentrations in seawater as a possible cause of low survival of larval mussels

BACKGROUND

A period of seismic activity starting in 2010 coincided with a decline in commercial catches of wild seed mussels in a major aquaculture production region of New Zealand. Analyses of over 40 years of mussel seed catch data from in the Pelorus and Kenepuru Sounds, confirmed a marked decline since 2010 in catches of the preferred, green-lipped mussel (Perna canaliculus), the larvae of which is known to have low tolerance of heavy metals in seawater.

METHODS

Heavy metal mean concentrations were measured throughout the Pelorus and Kenepuru Sounds. The concentrations ranged from < 0.60-3.24, < 16.94-74.35, < 1.47-4.00, 2.23-19.02, 1.86-3.29 and 0.12-0.52 µg L^-1 for Cr, Fe, Cu, Zn, As, and Cd, respectively. Seawater from six locations in the Sounds, historically associated with high commercial catches of settling mussel larvae, was used for experimental rearing of green-lipped mussel larvae.

RESULTS

No mussel embryos survived when incubated in these seawater samples. The mean concentrations of Cr, Fe, As, and Cd were significantly higher in the seawater from the Sounds than in the hatchery seawater. A higher concentration of one or a combination of these heavy metals could be the cause of the poor larval survival. These findings could be crucial for the sustainability of mussel farming in the area.

Use of limpets as alternative to mussels in metal pollution monitoring; application in the Canary Islands

Metal pollution monitoring programs make use of organisms, such as mussels, as biomonitors to evaluate and compare the metal pollution status of coastal areas worldwide. Despite the widespread distribution of mussels of the genus Mytilus, there are places where these organisms are absent or where their abundance is insufficient for biomonitoring purposes, such as in the Canary Islands (Spain). This study considers the use of limpets of the genus Patella as alternative/complementary species in metal pollution monitoring, and compares the bioaccumulation capacity of mussels and limpets collected simultaneously during several sampling campaigns at 11 sampling sites along the continental Spanish Atlantic coastline. Results show that there are some differences in bioaccumulation capacity between limpets and mussels, with limpets showing in average higher concentrations of Cd, Cr, Ni, As and Cu, and lower concentrations of Zn, while concentrations of Hg and Pb were similar for both types of organisms. Significant correlations between metal concentration in mussels and limpets were found for most metals, with the notable exception of Cd, that showed a very different bioaccumulation pattern in both types of organisms. Limpet to mussel metal concentration ratios were derived that can be used to compare the results of metal biomonitoring using either limpets or mussels, and limpets were successfully used in a monitoring survey in the Canary Islands.