The Negative Relationship between Fouling Organisms and the Content of Eicosapentaenoic Acid and Docosahexaenoic Acid in Cultivated Pacific Oysters,Crassostrea gigas

Bivalves serve as an important aquaculture product, as they are the source of essential fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in our diet. However, their cultivation in the wild can be affected by fouling organisms that, in turn, affect their EPA and DHA content. The effects of fouling organisms on the EPA and DHA contents of cultivated bivalves have not been well documented. We examined the effects of fouling organisms on the EPA and DHA contents and condition index of cultured oysters, Crassostrea gigas, in an aquaculture system. We sampled two-year-old oysters from five sites in Shizugawa Bay, Japan, in August 2014. Most of the fouling organisms were sponges, macroalgae, and Mytilus galloprovincialis. A significant negative relationship existed between the DHA content in C. gigas and the presence of sponges and macroalgae. A lower C. gigas EPA content corresponded to a higher M. galloprovincialis fouling mass and a lower C. gigas condition index. This can be explained by dietary competition between C. gigas and M. galloprovincialis for diatoms, which were the main producer of EPA in our study sites. Our findings indicate that fouling organisms likely reduce the EPA and DHA content in cultivated oysters. Therefore, our results suggest that the current efforts to remove fouling organisms from oyster clusters is an effective strategy to enhance the content of EPA and DHA in oysters.     

Efficacy of Netminder® silicone release coating for biofouling reduction in bay scallop grow‐out and comparative effects on scallop survival,growth and reproduction

Netminder^®, a water‐based silicone barrier release coating, was highly effective in reducing biofouling of lantern nets during grow‐out/overwintering of bay scallops, Argopecten irradians irradians, in a large‐scale restoration programme in New York, USA. Compared with untreated nets, scallops held in Netminder^®‐coated nets experienced reduced survival after 8 months, probably due to higher loads of epibionts on their shells. However, this was countered by higher reproductive and overall condition of scallops in treated vs. untreated nets; there were no consistent differences in shell growth in different net treatments. Although further testing is recommended under a wider range of conditions, we conclude that for the purposes of our scallop restoration work, coating nets with Netminder^® would eliminate the need for a gear change in spring, thus reducing labour costs; the coating process should be refined so that Velcro closures of nets do not become sealed shut.     

The effectiveness of several commercial antifouling treatments at reducing biofouling on finfish aquaculture cages in British Columbia

Biofouling in finfish aquaculture is an important issue because copper based antifoulants contribute to marine pollution and biofouling management incurs heavy costs to the industry. The purpose of this study was to assess the effectiveness five treatments (non‐biocidal: Dyneema, Netpolish, Aquacoating and ThornD; biocidal using cuprous oxide: Netrex) as compared with an untreated nylon net. After 8 months, effectiveness was determined by quantifying changes in: per cent net occlusion, per cent cover of major fouling groups, and biomass. Only one non‐biocidal treatment performed better than the control in one performance index (Dyneema had lower biomass), and overall, the copper treatment was most effective. The results from this study demonstrated that the effectiveness of copper treatments will continue to be a barrier to the implementation of non‐biocidal antifoulants, and that more research is needed to develop effective, non‐biocidal antifoulant coatings for aquaculture operations.     

Quantitative quality evaluation of Eastern oyster (Crassostrea virginica) cultured by two different methods

In order to evaluate the quality of oysters and whether a production method affects quality or not, a set of objective quantitative quality measures was developed. Eastern oysters (Crassostrea virginica) were cultured using two different treatments (never desiccated or desiccated daily with tidal exposure) and the meats were tested by textural, physico‐chemical and chemical analyses over a 25‐day cold storage period. Texture analyses parameters (cutting force and chewiness on oyster adductor muscles) were strongly correlated with storage time before the death of oysters and could be used as a quality indicator for oyster. Total volatile basic nitrogen (TVBN) could be used as freshness indicator for raw Eastern oysters, with the acceptability of 11 mg/100 g. Models for evaluating the quality of oysters were established that reflect the impact of a biofouling treatment on oyster's shelf life and texture attributes. The methods and quality indicators developed in this study were effective in evaluating the quality and freshness of Eastern oysters objectively, and could serve as routine quality check of oyster meat for the industry.     

Inhibition of Bacterial Quorum Sensing by Extracts from Aquatic Fungi: First Report from Marine Endophytes

In our search for quorum-sensing (QS) disrupting molecules, 75 fungal isolates were recovered from reef organisms (endophytes), saline lakes and mangrove rhizosphere. Their QS inhibitory activity was evaluated in Chromobacterium violaceum CVO26. Four strains of endophytic fungi stood out for their potent activity at concentrations from 500 to 50 μg mL⁻¹. The molecular characterization, based on the internal transcribed spacer (ITS) region sequences (ITS1, 5.8S and ITS2) between the rRNA of 18S and 28S, identified these strains as belonging to four genera: Sarocladium (LAEE06), Fusarium (LAEE13), Epicoccum (LAEE14), and Khuskia (LAEE21). Interestingly, three came from coral species and two of them came from the same organism, the coral Diploria strigosa. Metabolic profiles obtained by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) suggest that a combination of fungal secondary metabolites and fatty acids could be the responsible for the observed activities. The LC-HRMS analysis also revealed the presence of potentially new secondary metabolites. This is, to the best of our knowledge, the first report of QS inhibition by marine endophytic fungi.     

Anti-Larval and Anti-Algal Natural Products from Marine Microorganisms as Sources of Anti-Biofilm Agents

Bacteria growing inside biofilms are more resistant to hostile environments, conventional antibiotics, and mechanical stresses than their planktonic counterparts. It is estimated that more than 80% of microbial infections in human patients are biofilm-based, and biofouling induced by the biofilms of some bacteria causes serious ecological and economic problems throughout the world. Therefore, exploring highly effective anti-biofilm compounds has become an urgent demand for the medical and marine industries. Marine microorganisms, a well-documented and prolific source of natural products, provide an array of structurally distinct secondary metabolites with diverse biological activities. However, up to date, only a handful of anti-biofilm natural products derived from marine microorganisms have been reported. Meanwhile, it is worth noting that some promising antifouling (AF) compounds from marine microbes, particularly those that inhibit settlement of fouling invertebrate larvae and algal spores, can be considered as potential anti-biofilm agents owing to the well-known knowledge of the correlations between biofilm formation and the biofouling process of fouling organisms. In this review, a total of 112 anti-biofilm, anti-larval, and anti-algal natural products from marine microbes and 26 of their synthetic analogues are highlighted from 2000 to 2021. These compounds are introduced based on their microbial origins, and then categorized into the following different structural groups: fatty acids, butenolides, terpenoids, steroids, phenols, phenyl ethers, polyketides, alkaloids, flavonoids, amines, nucleosides, and peptides. The preliminary structure-activity relationships (SAR) of some important compounds are also briefly discussed. Finally, current challenges and future research perspectives are proposed based on opinions from many previous reviews.     

海水贝类养殖中污损生物的防除研究进展

据2002年统计，我国贝类养殖产量占海水养殖总量的79．4％，贝类养殖面积占海水养殖面积的66．9％，贝类养殖种类已发展到了30余种，其中主要为贻贝、扇贝、蛤、蚶、牡蛎等。贝类养殖已成为我国海水养殖业的重要组成部分。目前广泛采用的贝类养殖方式是网笼养殖，但是贝类在笼内放养一定时间后，一些海生动物、植物和微生物会在贝壳表面和养殖网笼的表面附着从而影响养殖贝类的正常生长。污损生物的大量出现严重影响了贝类养殖业的生产效率。如何有效地防止和减少污损生物对养殖贝类和养殖器具的危害，已成为水产养殖业的重要研究课题之一。