Lethality of microalgae to farmed Atlantic salmon ( Salmo salar)

• Published in: Aquaculture Vol. 308; no. 3; pp. 101 - 105
• Main Authors: Burridge, L.E., Martin, J.L., Lyons, M.C., LeGresley, M.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 21-10-2010; Amsterdam: Elsevier Science; Elsevier; Elsevier Sequoia S.A
• Subjects: adverse effects; Alexandrium fundyense; Algae; algal blooms; Animal aquaculture; Animal populations; Animal productions; Aquaculture; Atlantic salmon; Bay of Fundy; Biological and medical sciences; Chaetoceros socialis; Ditylum brightwellii; Eucampia zodiacus; farmed fish; fish farms; Fish production; Fundamental and applied biological sciences. Psychology; General aspects; lethal dose; Lethality; Marine; microalgae; mortality; phytoplankton; Plankton; Salmo salar; Salmon; Canada; named bodies of water; Bay of Fundy; ANW, Canada, Fundy Bay; Atlantic salmon; Lethality; Ditylum brightwellii; Eucampia zodiacus; Chaetoceros socialis; Alexandrium fundyense; Salmonidae; Farming animal; Algae; Salmo salar; Heterokontophyta; Vertebrata; Bacillariophyta; Dinophyta; Pisces; Aquaculture
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2010.07.034

Phytoplankton blooms in the Bay of Fundy have been implicated in the deaths of farmed Atlantic salmon (
Salmo salar). To establish whether or not elevated concentrations of some phytoplankton species can cause harmful effects or mortality, monocultures of three species,
Alexandrium fundyense,
Ditylum brightwellii, and
Chaetoceros socialis were grown in large quantities. Atlantic salmon smolts were exposed to a range of concentrations of each of these cultures for 24
h and, when mortality occurred, an LC50 was calculated (cells DEL id="del2" orig="•"; L
−1).
Eucampia zodiacus was collected by plankton tow and used in bioassays as well. Exposure of Atlantic salmon to
D. brightwellii,
C. socialis or
E. zodiacus at concentrations as high as 1.0
×
10
6
cells L
−1, 4.0
×
10
6
cells L
−1 or 9.0
×
10
5
cells L
−1, respectively resulted in no apparent deleterious effect. These concentrations are equal to or greater than concentrations of these species observed in the field.
A. fundyense was the only species of the 4 examined that was shown to be lethal to Atlantic salmon smolts. The 6
h LC50 was estimated as 7.24
×
10
5
cells L
−1 and the 24
h LC50 was estimated as 6.14
×
10
5
cells L
−1 indicating effects occur quickly and longer exposures do not change the LC50 estimates significantly. The LC50 concentrations represent cell counts similar to those observed in the field. The no observable (lethal) effect level for
A. fundyense and Atlantic salmon is estimated as approximately 2.0
×
10
5
cells L
−1 over 6
h and 1.0
×
10
5
cells L
−1 over 24
h. Cell counts do not reflect the toxicity of individual cultures but may be valuable for aquaculture site management. Chemical analyses of the cultured
A. fundyense cells in this study show a mean concentration of 33
pg saxitoxin equivalents ⋅ cell
−1.