B. Hansen et al., PHYSIOLOGICAL-EFFECTS OF THE DETERGENT LINEAR ALKYLBENZENE SULFONATE ON BLUE MUSSEL LARVAE (MYTILUS-EDULIS) IN LABORATORY AND MESOCOSM EXPERIMENTS, Marine Biology, 128(4), 1997, pp. 627-637
A series of laboratory (short-term exposure in small beakers) studies
and a 19 d mesocosm (6 m(3) polyethylene bags filled with fjord water)
study were conducted on blue mussel, Mytilus edulis, larvae and plant
igrades exposed to a concentration gradient of the detergent linear al
kylbenzene sulphonate (LAS, 0 to 39 mg l(-1)). LAS is increasingly fou
nd in nearshore environments receiving wastewater from urban treatment
plants. The aims were to observe physiological effects on swimming, g
razing and growth in the laboratory and effects on settling and popula
tion development at in situ conditions (in field mesocosms) in order t
o evaluate the damages on ciliated meroplankton caused by LAS. In the
laboratory the larvae showed a 50% mortality at 3.8 mg LAS l(-1) after
96 h exposure whether or not food was provided. Additionally the swim
ming behaviour was affected at 0.8 mg LAS l(-1) (i.e. a more compact s
wimming track, a smaller diameter of the swimming tracks, and reduced
swimming speed). The larval particle grazing was reduced 50% at 1.4 mg
LAS l(-1). The specific growth rate of the larvae was reduced to half
at 0.82 mg LAS l(-1) over 9 d. During the mesocosm experiment, the la
rval population showed a dramatic decrease in abundance within 2 d at
concentrations as low as 0.08 mg LAS l(-1), both due to a significantl
y increased mortality, but also due to settling. The settling success
was reduced at the same LAS concentration as that at which mortality w
as observed to increase significantly. In addition to reduced settling
rate, the larvae showed delayed metamorphosis and reduced shell growt
h as a response to LAS. Our hypothesis that the larval ciliary apparat
us, crucial for normal swimming, orientation, and settling behaviours
and for particle uptake, was damaged due to LAS exposure is supported
by our results. This is confirmed by the physiological data (grazing,
growth) and in the direct video-based observations of larval performan
ce (swimming) and provides a reasonable explanation for what was obser
ved in the bags (abundance, settling, mortality). These physiological
effects on blue mussel larvae/plantigrades occurred at LAS concentrati
ons reported to occur in estuarine waters.