The Ecotoxicological Effects of Microplastics on Primary Producers in the Marine Environment

Plastic debris is an emerging environmental threat all over the world. But its effect and distribution in the marine ecosystem is barely known. Microplastics abundance in the marine vegetated area is about 2 to 3 times higher than the bare site in the ocean. Although seagrass meadows trap huge amount of microplastics over the ocean floor, a considerable amount of microplastics are also sink incorporating with the marine aggregates from the epipelagic zone of the ocean. Scavenging of microplastics by diatom aggregation decreases the sinking rate of them rather than cryptophyte. As we know, marine snow is the leading carbon source for zoobenthos, but the ubiquitous presence of microplastics damages cell of different microalgae which may alter the food webs of marine ecosystems. Additionally, microplastics releases immense amount of dissolved organic carbons (DOC) in the surrounding seawater that stimulates the growth of heterotrophic microorganisms as well as their functional activity. Plastic debris result in outbreaks of disease in the marine environment and coral reefs are highly affected by it. When coral reef comes in contact with microplastics, the disease infestation rate of the reef increases massively. Three major disease viz., skeletal eroding band, white syndrome and black band of coral reef causes approximately 46% of reef mortality due to microplastics consumption. Due to complex structure and size, the corals accumulates huge amount of microplastics that increases growth of pathogens by hampering the coral immune system. Existing scientific evidence presents that exposure of microplastics in aquatic environments triggers a wide variety of toxic insult from feeding disruption to reproductive performance, disturbances in energy metabolism throughout the ocean. The present review focused on the ecotoxicological effect of microplastics on primary producers of ocean, its uptake, accumulation, and excretion, and its probable toxicity with risk assessment approaches

FISH BIODIVERSITY, THREAT STATUS AND CONSERVATION SIGNIFICANCE OF THE JAMUNA RIVER, BANGLADESH

Ovo istraživanje provedeno je kako bi se istražila raznolikost, brojnost i status zaštite riblje faune u rijeci Jamuna, pritoku rijeke Brahmaputra u Bangladešu. Ukupno je zabilježeno 55 ribljih vrsta koje pripadaju u 6 redova, 20 porodica i 41 rod, a koje su prikupljene s pet odabranih lokacija u blizini rijeke tijekom razdoblja istraživanja od studenog 2018. do listopada 2019. godine. Red Cypriniformes i Siluriformes zabilježeni su kao dominantne skupine u ribljoj fauni, a koje čine 34,55% i 30,91% od ukupno uočenih vrsta. Tijekom razdoblja ispitivanja zabilježene su različite vrste manjih autohtonih vrsta (SIS) i ukupno 26 vrsta s crvene liste Međunarodne unije za zaštitu prirode (IUCN). Shannon – Weaverov indeks (H), Simpsonov indeks dominacije (D), Simpsonov indeks raznolikosti (1-D), Margalefov indeks (d) i ravnomjernost (E) izračunati su kako bi se pokazala raznolikost vrsta, bogatstvo i ravnomjernost riba. Tijekom ispitivanog razdoblja i vrijednosti tih parametara su se kretale između 1,28-1,48, 0,26-0,33, 0,67-0,74, 1,22-1,46 i 0,77-0,86. Ovo istraživanje preporučuje akcijski plan gospodarenja i očuvanja ribe, posebno uspostavljajući i održavajući skloništa za ribe, zabranjujući neselektivni ribolov i upotrebu destruktivnih ribolovnih alata radi zaštite rastilišta i mrijestilišta riba kako bi se održala perspektiva biološke raznolikosti ribarstva u rijeci Jamuna.The present survey aimed to explore the fish fauna diversity, abundance and conservation status in the Jamuna River, a tributary of the River Brahmaputra, Bangladesh. During the study period from November 2018 to October 2019, a total of 55 species of fish were recorded, belonging to 6 orders, 20 families and 41 genera from the five selected stations near the river. Orders Cypriniformes and Siluriformes were recorded as the dominant group in the fish fauna community that comprises 34.55% and 30.91% of total species, respectively. Various types of Small Indigenous Species (SIS) and a total of 26 International Union for Conservation of Nature (IUCN) red-listed species were recorded. Population indices, viz. Shannon–Weaver index (H), Simpson’s dominance index (D), Simpson’s index of diversity (1-D), Margalef’s index (d) and Evenness (E), were applied to demonstrate the species diversity, richness and evenness of fish, and their overall values were 1.28-1.48, 0.26-0.33, 0.67-0.74, 1.22-1.46 and 0.77-0.86, respectively. To sustain the prospect of fisheries biodiversity in the Jamuna River of Bangladesh, different fish management and conservation plan of action specifically establishing and maintaining fish sanctuaries, banning indiscriminate fishing and the use of destructive fishing gears for the protection of the breeding and nursery grounds of fish should be taken into consideration with utmost priority

Antimicrobial Resistant Bacteria in Shrimp and Shrimp Farms of Bangladesh

The purpose of this study was to investigate the presence of pathogenic bacteria, specifically Escherichia coli and Salmonella and Vibrio species, and their antimicrobial resistance in shrimp aquaculture facilities of Bagerhat (Bangladesh). Sediment samples were collected from both Penaeus monodon and Macrobrachium rosenbergii farms and shrimp samples from the Macrobrachium rosenbergii facility. The abovementioned bacteria were not found, but five Enterobacterales (Proteus penneri, Proteus alimentorum, Morganella morganii, Enterobacter hormaechei subsp. xiangfangensis and Plesiomonas shigelloides) were detected. This is the first documented case of Enterobacter hormaechei subsp. xiangfangensis in a shrimp farm. Nine antibiotics—ampicillin, gentamicin, chloramphenicol, oxytetracycline, nitrofurantoin, levofloxacin, ciprofloxacin, azithromycin, and co-trimoxazole—were selected for antibiotic resistance testing, and the majority (88.9%) had at least one isolate that was resistant. Across sources, 78.0% of isolates were resistant to at least one antimicrobial, and multidrug resistance was also detected in 29.3% of all isolates. Despite the low number of samples analyzed, nine in total, the results of this experiment emphasize that shrimp farms in Bagerhat may have a problem with antimicrobial-resistant bacteria. This could have negative impacts on shrimp quality and consumers’ health

Domestication technique of commercially important freshwater mud eel, Monopterus cuchia (Hamilton, 1822)

The research was conducted to develop the domestication technique of Monopterus cuchia collected from Sherpur district, Bangladesh. A total of 300 young M. cuchia (average 95±6.4 g) was reared under nine treatments as earthen pond with dead fish (EpDf), earthen pond with live fish (EpLf), earthen pond with formulated feeds (EpFf), mud treated plastic tank with dead fish (PmDf), mud treated plastic tank with live fish (PmLf), mud treated plastic tank with formulated feeds (PmFf), plastic tank with dead fish (PtDf), plastic tank with live fish (PtLf), and plastic tank with formulated feeds (PtFf) with three replicates each. Size of each earthen pond was 1m3 and plastic circular tank was 0.322m3. Stocking density was maintained at 10 fish in each replicate by random selection. Survival, weight gain (WG), specific growth rate (SGR%/day), feed conversion ratio (FCR), feed conversion efficiency (FCE), and protein efficiency ratio (PER) were measured. The best survival (100±0), WG (61.17±1.83), SGR (0.118±0.026), FCR (2.44±0.17), FCE (35.75%±2.90), and PER (1.75±0.14) were obtained in EpLf, which was significantly higher (P<0.05) than others. This is the first report of domestication of M. cuchia and indicates that earthen pond with live fish might be suitable for domestication of M. cuchia

Development of formalin killed vaccine candidate against streptococcosis caused by Enterococcus sp. in Nile tilapia

Multiple bacteria under Streptococcus, Enterococcus and Lactococcus genera are considered to be associated with Streptococcosis. This study was conducted to develop and evaluate the effectiveness of whole cell formalin killed vaccine prepared from E. faecalis, E. hirae and E. faecium against the streptococcosis in Nile tilapia. To develop the candidate vaccine, efficacy of whole cell killed E. faecalis (strains BFF1B1 &amp; BFTS22), E. hirae (strain BFTS29) and E. faecium (strain BFTS31) were evaluated. The vaccine prepared by mixing 3 % formalin and left for 24 h to kill the bacterial cells. Physiological saline (0.85 %) was mixed to the harvested formalin free killed cells to make final suspension for vaccine. This vaccine was administered to the fingerling tilapia (average weight 30 ± 5 g) by interperitoneal injection (IP) and bath immersion (BI) methods. The vaccinated group was monitored for 28 days to assess the developed immunity and vaccine safety into the fish. Post vaccination in vivo challenge test were performed against the pathogens. The hematological parameters (RBC, WBC, platelets and hemoglobin) and specific IgM were found significantly higher (p  0.05) between IP and BI vaccination method. Formalin killed vaccine showed an excellent efficacy against Enterococcus sp. infection in Nile tilapia by IP method although bath immersion could also be an alternative

Assessment of Heavy Metals in the Sediments of Chalan Beel Wetland Area in Bangladesh

This study aimed to determine the levels and possible sources of heavy metals (HMs) in the sediments of Chalan beel (a large lake-like aquatic ecosystem) area located in the northwestern part of Bangladesh. The mean concentrations (mg kg−1) of two HMs, Cd (6.22) and Pb (51.39) exceeded the world normal averages (WNA), whereas the mean concentrations (mg kg−1) of Ni (60.46), Zn (10.75), Mn (8.64) and Cu (4.71) were below the WNA. The sediments showed significant enrichment with Cd, Pb and Ni in the studied area. The geo-accumulation index values of Cd (3.72) and Pb (0.76) were significantly higher in the sediments. The contamination factor and potential ecological risk index values of Cd and Pb revealed that Chalan beel was extremely and moderately contaminated by these heavy metals, respectively. Analysis of dye complexes used in handlooms around the Chalan beel areas revealed that mean concentrations of Cd and Pb exceeded the WNA. Furthermore, analyses of principal component, cluster and correlation matrix indicated that the presence of the higher levels of Cd and Pb in the sediments might be linked to various anthropogenic activities like discharged dyes into the beel water from the nearby handloom dyeing factories