Bài giảng Quản lý chất lượng môi trường trong nuôi trồng thủy sản: Phần 2

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Bài giảng Quản lý chất lượng môi trường trong nuôi trồng thủy sản: Phần 2 gồm có 3 chương trình bày về khái niệm về vi sinh vật trong nguồn nước; ảnh hưởng của chất lượng nước ao đến môi trường xung quanh và chất lượng sản phẩm; tiến trình quan trắc chất lượng môi trường nước phục vụ nuôi trồng thủy sản.

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Nội dung Text: Bài giảng Quản lý chất lượng môi trường trong nuôi trồng thủy sản: Phần 2

QUẢN LÝ CHẤT LƯỢNG MÔI TRƯỜNG TRONG NUÔI TRỒNG THỦY SẢN
Chương 3: Khái niệm về vi sinh vật trong nguồn nước
Microbial Interactions with Macroorganisms Aquatic environment is relatively rich in microorganisms Up to 105 to 106 cells / mL Cilliates, other protists, and viruses Macroorganisms in aquatic environment Constantly exposed to microorganisms
Historical perspectives Changes during storage Effects on spoilage Relationship between environmental and fish microflora Basis for monitoring changes in fish farms Disease causing bacteria Human Fish & Shellfish Increasingly, more focus on normal microflora and their interactions with the host organisms
Microbiology of bivalve mollusks Microorganisms as food Natural microflora Filter feeders and the ecosystem Hansen and Olafsen, 1999; Maeda, 2002
Microorganisms as food Filter feeders Deposit feeders (Suspension feeders) Feed on microorganisms that Feed on microorganisms that coats the surface of sediments they filter out of the and soil particles environment Clams, oysters, barnacles, Worms, fiddler crab sponge Larval forms of animals may require smaller microorganisms such as bacteria, while an adult may prefer larger microorganisms such as flagellated protists and algae
Oyster anatomy Labial palps Draw water in over its gills through the beating of cilia Suspended food (plankton) and Visceral mass particles are trapped in the mucus of the gills Sort by labial palps and transport Lower intestines to the mouth, eaten, digested, and feces expelled Pseudofeces = particles which are not sorted as food and are rejected through the mouth Affect by temperature Rectum and anus Greatest when water temperature > 50°F (~10°C) Oyster anatomy lab http://www.mdsg.umd.edu/oysters/anatlab/index.htm
Oyster filtering mechanism lab http://www.mdsg.umd.edu/oysters/oysfilt.htm
Natural microflora of mussels and oysters A majority of isolates are gram-negative (68%) and aerobic (76%) bacteria Predominant flora: Vibrio, Pseudomonas, Shewanella, Aeromonas, Acinetobacter, and Flavobacterium Gram-positive bacteria: Staphylococcus, Bacillus, Streptococcus Predominant Vibrio species includes: V. alginolyticus, V. splendidus, and V. (Listonella) anguillarum* Not always reflect external environment Suggests selective process to sequester and maintain certain species Kueh and Chan, 1985 ;Hariharan et al., 1995
Filter feeders and the ecosystems An adult oyster can filter as much as 60 gallon per day Oysters can filter out sediments and nutrients (nitrogen) and deposit them on the bottom “Top-down" grazer control on phytoplankton Reduce turbidity, increasing the amount of light reaching the sediment surface Extending the depth to which ecologically important benthic plants (seagrasses and benthic microalgae) can grow Newell, 2004 ;Chesapeake Bay Foundation http://www.cbf.org/
Filter feeders bivalves removing inorganic and organic particles from water column and transferring undigested particulate material to the sediment in the form of their biodeposits Newell, 2004
Microbiology of Fish Eggs, skin, gills microflora Intestinal microflora
Bacteria on mucosal surface (1) Host-parasite relationship Host = an organism which harbors parasite (microorganisms) Parasite = an organism that lives on or in a second organism Surfaces such as eggs, skin, gills, and intestinal tract Mucus layer as an adhesion site and protective layer Indigenous vs. transient (autochthonous vs. allochthonous) Indigenous = able to grow and multiply on the surface of the host animal Transient = not able to grow or multiply on the surface of the host animal; does not persist for a long period of time
Bacteria on mucosal surface (2) Loose association Adhesion Invasion
Eggs microflora Fish embryos secret inorganic and low molecular weight organic compound, which can diffuse out through the shells Attract bacteria utilizing these compounds and colonize egg surface Normal healthy eggs flora: Cytophaga, Pseudomonas Dead eggs: fluorescent Pseudomonas Not the cause of dead, but rather attracting to nutrient leaching Overgrown of bacteria can hamper eggs development Leucothrix mucor on cod eggs Flavobacterium ovolyticus on halibut eggs Cahill, 1990; Hansen and Olafsen, 1999
Skin Microflora Reflect that of surrounding water May have from 102 to 104 bacteria/ cm2 Unit of measurement per area Surface sampled by using a sterile swab Muscle tissue should be sterile Gram negative: Pseudomonas, Moraxella, Vibrio, Flavobacterium, Acinetobacter, Aeromonas Gram positive: Micrococcus, Bacillus Cahill, 1990
Gill Microflora May contain 102 to 106 bacteria/ g The number is quite low considering its high surface area and being continual flushed by water Extensive colonization of certain types of bacteria (Flavobacterium) Gram negative: Pseudomonas, Flavobacterium, Vibrio, Moraxella, Cytophaga Gram positive: Micrococcus, Bacillus (in warmer water) Cahill, 1990
Intestinal microflora (1) Established at the larval stage Developed into a persistent flora at the juvenile stage Population of microorganisms tends to increase along the length of the GI tract Largest number of bacteria in the intestines (up to 10 8 CFU/g) Gram negative: Pseudomonas, Vibrio, Achromobacter, Flavobacterium, Corynebacterium, Aeromonas Gram positive: Bacillus, Micrococcus Influenced by stages of life, diets, feeding, water temperature, habitat Large number when feeding, very few when not feeding Organic content of the environment Vibrio dominates in seawater, Aeromonas dominates in freshwater Cahill, 1990; Hansen and Olafsen, 1999
Intestinal microflora (2) Microvilli of the epithelial cells of common wolffish (A. lupus L.) Bacteria SEM of the enterocytes in the midgut of Artic charr Ringo et al., 2003
Intestinal microflora (3) Endocytosis of bacteria in the hindgut of spotted wolffish fry Bacteria TEM of Atlantic salmon gut epithelium Ringo et al., 2003