The current situation and potential effects of climate change on the microbial load of marine bivalves of the Greek coastlines: an integrative review

Abstract

Global warming affects the aquatic ecosystems, accelerating pathogenic microorganisms' and toxic microalgae's growth and spread in marine habitats, and in bivalve molluscs. New parasite invasions are directly linked to oceanic warming. Consumption of pathogen-infected molluscs impacts human health at different rates, depending, inter alia, on the bacteria taxa. It is therefore necessary to monitor microbiological and chemical contamination of food. Many global cases of poisoning from bivalve consumption can be traced back to Mediterranean regions. This article aims to examine the marine bivalve's infestation rate within the scope of climate change, as well as to evaluate the risk posed by climate change to bivalve welfare and public health. Biological and climatic data literature review was performed from international scientific sources, Greek authorities and State organizations. Focusing on Greek aquaculture and bivalve fisheries, high-risk index pathogenic parasites and microalgae were observed during summer months, particularly in Thermaikos Gulf. Considering the climate models that predict further temperature increases, it seems that marine organisms will be subjected in the long term to higher temperatures. Due to the positive linkage between temperature and microbial load, the marine areas most affected by this phenomenon are characterized as 'high risk' for consumer health.

How Safe to Eat Are Raw Bivalves? Host Pathogenic and Public Health Concern Microbes within Mussels, Oysters, and Clams in Greek Markets

“…In particular, with very few exceptions, the major microbial load within marine bivalves in Greece consists of host pathogenic bacteria, protozoans or other parasites, and a far lesser extent of public health harmful microorganisms. Hence, despite the microbial load detected that is in line with a recently published review paper [137], our data suggest that Greek bivalves are microbiologically safe for raw consumption, and the sector of marine bivalve farming and fisheries, when proper depuration takes place in combination with systematic surveillance, shall continue to constitute a considerable primary sector. In this context, the findings of the present study are expected to contribute to defining the safety status of seafood products, in terms of microbial load, in the second largest city in Greece.…”

“…M. refringens is a protozoan parasite of the phylum cercozoan and order Paramyxida causing infection of the digestive gland of the marine bivalves and downregulation of the physiological processes, resulting lower growth rates and even losses in farms and in natural beds [20,133,134]. Detection rates of this parasite are higher in summer months, where temperatures demonstrate higher values in comparison with the winter months, and this phenomenon is amplified due to global climate warming [135][136][137]. Nevertheless, the Aber disease is not yet fully understood [136].…”

Are Marine Heatwaves Responsible for Mortalities of Farmed Mytilus galloprovincialis? A Pathophysiological Analysis of Marteilia Infected Mussels from Thermaikos Gulf, Greece

“…Particularly, bivalve farming represents an important marine aquaculture activity worldwide, raising production from nearly 1 million tons in 1950 to 14.54 million tons in 2013, with an annual value of more than USD 15 billion [ 4 , 5 ]. In Greece, although oyster and clam farming have been recently licensed, bivalve cultivation is still represented exclusively by the Mediterranean mussel Mytilus galloprovincialis (Lamarck, 1819) farming [ 6 , 7 , 8 ]. Mussel culture is depending on wild stocks since in the process of mussel farming, spat (juveniles) is collected from collector ropes or traps and transferred to neighboring mussel farming areas for cultivation, or occasionally to longer distances [ 9 ].…”

The Impact of Climate Change on Bivalve Farming: Combined Effect of Temperature and Salinity on Survival and Feeding Behavior of Clams Ruditapes decussatus

“…Moreover, warming and hyposalinity caused by changes in climate will promote the emergence, growth, and distribution of pathogenic microorganisms (e.g., viruses, bacteria, protozoans) and toxic microalgae (Zgouridou et al, 2022), therefore negatively impacting the immune and metabolic systems of bivalves (Matozzo and Marin, 2011;Turner et al, 2016), leading to severe mortalities. In fact, Reverter et al (2020) reported that most of the infected marine organisms showed higher mortalities at warmer temperatures.…”