Karenia mikimotoi

Table 2. Diatoms reported to have had harmful effects on aquaculture and
natural fisheries. From Smayda (2006) where specific effects are detailed. None
of these is known to affect human health due to direct contact or via aerosols.
Cerataulina pelagica Leptocylindrus minimus
Chaetoceros concavicornis Rhizosolenia chunii
Chaetoceros convolutus Skeletonema costatum
Chaetoceros debilis Thalassiosira aestivalis
Chaetoceros socialis Thalassiosira diporocyclus
Chaetoceros wighami Thalassiosira mala
Corethron criophilus Thalassiosira rotula
Coscinodiscus wailesii
Chaetoceros concavicornis and Chaetoceros convolutus have adverse effects on
finfish in the NE Pacific, causing distress or death. These diatoms have serrated setae
(spines), which cause mechanical damage to the gills. For example, in salmonids the
diatoms become retained in the inter-lamellar spaces of the gills, where they irritate the
goblet cells. This stimulates the over-production and accumulation of mucus on the
respiratory epithlium, which in turn reduces the efficiency of oxygen exchange,
resulting in hypoxia. As few as 5 cells mL −1 seawater may impair oxygen uptake
sufficiently in salmonids to cause mortalities and lower concentrations rendered some
species of salmon more susceptible to bacterial pathogens (Yang and Albright, 1992;
Albright et al., 1993). Other incidents related to the effects of other diatoms on fish are
reviewed in Landsberg (2002).
2.2.1 Effects on human health
There is a report of the diatom Fragilaria striatula possibly causing dermatitis in
professional fishermen in Scotland (Fraser and Lyell, 1963). The skin reaction was
associated with handling ropes and nets, which had become coated with a
mucilaginous layer of the diatom. Bacteria were associated with the diatom growth but
their possible involvement was not investigated. There was a subsequent report of
evidence of F. striatula causing dermatitis in lobster fishermen in the Bardsey sound
area of the Lleyn peninsula, N. Wales (Beer et al., 1968) and this diagnosis was
supported in a follow-up note describing work with a unialgal culture of the diatom
(Beer and Jones, 1969).
This could be classified as ‘occupational exposure’, the symptoms occurring after
frequent and prolonged contact. The possible effect of short-term exposure remains
unknown.
As regards reports of other non-toxic diatoms causing symptoms in humans, the
website of the Environmental Protection Authority of the State of Victoria, Australia,
http://www.epa.vic.gov.au/water/coasts/surf_diatoms.asp advises bathers to be on the
lookout for patches of surf zone diatoms on certain beaches:
“The diatoms which usually make up these patches are not toxic, although they may
cause some irritation to the human body. It is advisable to avoid swimming in dense
patches or at least shower after swimming or surfing”.
4 A Literature review of the potential health effects of marine microalgae and macroalgae