Rapp. P.-v. Réun. Cons. int. Explor. M er, 187: 108-114. 1987
Exceptional Plankton Blooms
Conclusions of discussions: Convener’s report
M iles Parker
Parker, Miles. 1987. Exceptional Plankton Blooms. Conclusions of discussions: Con­
vener’s report. - Rapp. P.-v. Réun. Cons. int. Explor. Mer, 187: 108—114.
This report draws on the papers presented to the meeting, the records of the session
rapporteurs, and the considerations of discussion groups that met on the two evenings
of the meeting to draw some general conclusions related to the terms of reference of
the special meeting. It reflects as accurately as possible the consensus prevailing
among the active participants.
Miles Parker: Ministry o f Agriculture, Fisheries and Food, Directorate o f Fisheries
Research, Fisheries Laboratory, Remembrance Avenue, Burnham-on-Crouch, Essex
CM08HA, UK.
T h e incidence o f excep tion al blo o m s
There are very few long time-series data on exceptional
bloom incidence. In assessing such data as are available,
distinction needs to be made between oceanic and open
shelf waters (A 6 ‘) on the one hand and on the other,
coastal and estuarine waters where terrestrial influences
may be more marked.
Since the mid-1960s, the dinoflagellate G yrodinium
aureolum has occurred in E uropean coastal and shelf
waters and has given rise to exceptional blooms in many
areas and caused fish kills (A9, B7, B8, D2, D8, D9).
The causes for its recent upsurge are unknown but it
has, however, been suggested (A9) that it is a recently
introduced species to E uropean waters; introduced spe­
cies may thrive excessively in the first years following
their introduction.
Apart from the special case of G. aureolum, it is more
difficult to point to trends in inshore waters of the
Atlantic. There has been a southward extension over a
long time-scale of Paralytic Shellfish Poisoning (PSP)
problems associated with both low and high biomasses
of Gonyaulax tamarensis on the east coast of Canada
and the U SA , apparently for natural climatic reasons.
Fluctuations in the degree of toxicity of shellfish in the
Bay of Fundy have been correlated with long time-scale
oceanographic and meteorological changes and with the
18-year lunar cycle on tidal mixing activity (C2). In
Europe, exhaustive studies failed to identify trends in
blooms in the Oslofjord, though changes in species
composition have been noted (D l). On the east coast of
the United Kingdom, PSP toxin has been recorded each
year since 1968, but no trends in toxicity have been
observed; shellfish toxicity is known to have occurred in
this area earlier in the century. In the Germ an Bight,
where blooms of Ceratium spp. and other species have
caused concern recently (B6), it is also known that such
events have occurred at intervals over the last century.
It is worth comparing results from inshore areas o u t­
side the North Atlantic, such as the Seto Inland Sea of
Japan where clear trends in bloom incidence have been
associated with trends in organic pollution (B13).
Exceptional blooms must be seen against the general
background of the normal cycle of phytoplankton bio­
mass. D ata from the Continuous Plankton Recorder
(CPR) (A6) for the Northeast Atlantic suggest a down­
ward trend in the incidence of periods of higher than
normal biomass of diatoms and Ceratium spp. in the last
20 years with an increase since the mid-1970s of the
more generalized “Phytoplankton Colour” index. These
trends may be superimposed on general downward
trends in zoo- and phytoplankton abundance.
In summary, there is little evidence in Atlantic waters
for any rising trend in bloom incidence, though the data
base is very small. Changes in species composition have
been observed, though the reason for these changes are
unclear.
Causal factors
Physical factors
'References to meeting papers in this text are given as the
programme num ber cited in the Annex to the Introduction
(e.g., A l , C3, etc.).
108
Recent research has notably improved the understand­
ing of the importance of physical factors in bloom in-
cidence (A l). The widespread extent of observed
changes (A6) in the plankton points to the important
role of long-term and widescale climatic and ocean­
ographic changes, though how these changes might be
related to bloom incidence is not well understood.
On a smaller scale, areas of high biomass or produc­
tion are associated with boundaries (pycnoclines and
fronts) and upwelling areas (A7). This is also true of
inshore areas where the effect of river inputs, in addi­
tion to tidal forces and other coastal influences on the
stability of the coastal waters, may be an important
factor, especially in exceptional blooms of diatoms early
in the year (B15). Later in the year, as nutrient levels
decline, dinoflagellate populations, which are a normal
component of the summer plankton, are noticeably high
at boundary systems and the incidence of summer
storms followed by calm weather is related to the in­
cidence of exceptional blooms.
Interaction of weather (C2) (especially wind) with the
sea and sea-sediments are also im portant factors, for
example, with respect to resuspension in the water co­
lumn of resting stages (cysts) of some dinoflagellates
from the sea bed (C6). Coastal transport and smallerscale transport processes (e.g., convergences) also have
a role to play in ensuring that the organisms reach the
correct environment and are not dispersed from it (B l,
A4, A5).
Biological factors
The role of biological factors is clearly important. Full
understanding of exceptional bloom events depends on
a thorough knowledge of the life cycles of the organisms
concerned (B l); such information is often lacking.
Among other relevant biological factors, reduced
grazing pressure, such as occurs particularly in response
to inhibitory properties of some dinoflagellates, may be
im portant to the development of large populations of
algae. The role of vertical migration (A2) in ensuring
both effective nutrient and light utilization and concen­
tration in surface waters aided by physical mechanisms
may be a key to the development of surface “red wa­
te r” . Some bloom species appear to be well adapted to a
changeable light environment.
N utrients
The role of nutrient enrichment is less clear (B l). Cer­
tainly, where nutrient levels are high, production will
occur somewhere, though nutrient-rich coastal waters
are often highly turbid and well mixed, which reduces
the opportunity for exceptional growth (A2). Similarly,
it is clear that in many cases it is the flux of nutrients
rather than their concentration which is important to
the development of algal populations, though relatively
low fluxes may be sufficient to sustain already existing
large populations. Some long-term data sets on inorga­
nic nitrogen and phosphorous nutrient concentrations
are available, but data on fluxes of nutrients are far
more limited and the roles of inputs or of recycling
through grazers, bacteria, or the sediments are poorly
understood. Current understanding suggests that the
physical structure of the water and its relationship to the
distribution and availability of nutrients is a major fac­
tor in bloom development (C l).
A n th ro p o g en ic factors - hypernutrification and
eutrophication
In relation to discussion of the effects of anthropogenic
influences on the incidence of exceptional blooms, it is
also necessary here to define the terms “hypernutrifica­
tion” and “eutrophication” .
Hypernutrification involves substantial and measur­
able increases in concentrations of dissolved nutrients
(which may include inorganic and organic compounds
of nitrogen, phosphorous, silicon, iron, and other trace
metals and vitamins). Current practice is generally to
use measurements of inorganic nitrogen and phospho­
rous because of their relative ease of measurement. It
should be noted, however, that laboratory investiga­
tions of phytoplankton have shown that a wide range of
substances can control growth, including not only sub­
stances which can be considered as nutrients, but also
substances such as toxic metals and materials which
control their availability to phytoplankton (B13).
Hypernutrification can in theory lead to increased
phytoplankton biomass and productivity in regions and
at times in which phytoplankton growth is limited by
nutrient availability. In freshwater ecosystems, this is
referred to as eutrophication and, by analogy, this term
has also come to be used in the marine context.
If high nutrient levels affect algal populations, they
might do so in three ways: (a) by directly increasing
overall annual biomass, perhaps by extension of the
growth season, (b) by leading to sporadic exceptional
outbursts of growth, and/or (c) by changing species
composition. The latter effect would be particularly
hard to distinguish from natural changes in species com­
position which occur all the time, for example, such
as those noted in CPR data throughout the eastern
North Atlantic (A6). As stated earlier, there is little
evidence to suggest that actual increases in exceptional
bloom incidence (other than G. aureolum) have oc­
curred in Atlantic waters. Equally, it is hard to find any
evidence for an overall measurable increase in biomass
in these waters, though the data available are very lim­
ited. If such effects were to occur, they would be most
likely to happen in areas where the spatial and temporal
scales of enrichment were such as to allow time for algal
growth, i.e., in enclosed embayments or estuaries or in
coastal areas affected by major river inputs. Even in
these areas it might be difficult to separate nutrient
109
effects from purely physical ones, (e.g., the effect of
freshwater input on stability). Such areas might include
the New York Bight, the G erm an Bight and southern
North Sea, the Kattegat (B7, B8), parts of the Baltic
(B4, B5), and areas such as the Oslofjord (D l). While
nutrient inputs compared with the available ‘pool’ are
undoubtedly high in these areas, it is still not easy to
point to clear examples of eutrophication. The availabil­
ity of phosphate in summer may allow increased pro­
duction by N-fixing blue-green algae in the Baltic, and
the high level of production of Phaeocystis (D5, DIO) in
the southeastern North Sea may point to a case of
eutrophication. Equally, if elevated nutrient concentra­
tions occur, exceptional meteorological and hydrographic conditions may permit outbursts of growth
(B6).
The case mentioned earlier of the Seto Inland Sea
(B13) raises a further question in relation to eutrophica­
tion and especially the potential role of anthropogenic
influences. T here are many field and laboratory data
that point to the significance on the one hand of vitamin
( D l l ) and growth factors in determining species com po­
sition and on the other, to the role of natural organic
chelating agents in controlling the toxicity and nutri­
tional availability of metals on algae. Recent research
suggests that the metal-complexing compounds in sew­
age effluent may be chemically similar to naturally oc­
curring humic and fulvic acids in natural waters. Since
dinoflagellate growth is often stimulated by the addition
of soil extracts or similar enrichments containing humic
acids, it is possible that pollution of coastal areas could
enhance bloom development due to input of organic
rather than to inorganic compounds. The Seto Inland
Sea experience suggests that bloom incidence there was
at least partially related to organic inputs as well as to
nutrient inputs, but there are few data available on
either the natural levels of such substances or the levels
of inputs and fluxes in Atlantic waters.
In summary, on the basis of data on exceptional
blooms, there is little evidence for the existence of
large-scale eutrophic effects in North Atlantic waters.
However, such effects are more likely to be observed
through study of annual phytoplankton biomass as a
whole, rather than exceptional bloom incidence. Suit­
able data sets are not available for most areas; in partic­
ular, biological data and long time-series data sets are
lacking. A ttention should be addressed especially to the
areas identified above and to other estuarine areas re­
ceiving large natural or anthropogenic inputs of nutri­
ents, w hether organic or inorganic. Further research is
needed on the role played by organic enrichment.
Predictability o f “e x c e p tio n a l” even ts
Understanding of the oceanography of bloom incidence
is now sufficient to identify areas in which there is a high
probability of bloom occurrence, either on the basis of
110
long time-series data o r a knowledge of the physical
structure present (A l, A6). Hydrographic or physical
oceanographic variables and phenom ena associated
with blooms and related events, e.g., hypoxia, have
been modelled in a preliminary m anner in certain re­
gions. These models are capable of predicting condi­
tions which can lead to bloom circumstances and events.
Relatively simple biological models (B l), incorporating
data particularly on grazing rates and the behaviour and
physiology of bloom-forming species and the dominant
nutrient flux, can also be used to predict the probability
of bloom events in given areas. Prediction of the group
of species (diatom, dinoflagellates, flagellates) likely to
dominate the bloom is feasible on the basis of the d e­
gree of turbulence/stability of the water column, though
it is more difficult to make predictions as to particular
species dominance since information on the life histo­
ries and specific growth rates of many species is lacking.
However, these models may be extended to prediction
of harmful effects either through estimation of the ef­
fects of biomass on oxygen consumption or through the
relationships which are beginning to be established be­
tween toxicity and the nutrient status of the cell.
Such predictability is purely probabalistic since the
actual concentrations or values of physical, chemical,
and biological factors that lead to a particular bloom
cannot be predicted absolutely through the application
of such models. Probabalistic prediction, however, is
probably adequate for overall environmental manage­
ment purposes and should be used at this stage as a
means of directing resources to the longer-term mon­
itoring of areas theoretically likely to have a higher
incidence of blooms. O n the other hand, mariculture
and shellfish fishery managers require prediction of ac­
tual events over much shorter time and smaller spatial
scales; this can only come from a system of monitoring
at the areas to be protected (C l).
Predictive capabilities could be im proved by:
(a) an improved knowledge of the biology and life his­
tories of blooming species;
(b) collection of long time-series data on phytoplank­
ton selected species composition and biomass, in
areas identified above. One source of historical
data would be the recent (100 years) sediment rec­
ord of cysts and pigments which could be obtained
from areas of high natural sediment accumulation
and low bioturbation (C6).
Satellite and aircraft remote sensing may provide useful
support for field programmes, especially in synopticity,
but their use in gathering long time-series data needs
further investigation. A utom ated methods for the con­
tinuous collection of biological data also need further
development.
M a n a g e m e n t o f public health problem s
related to e xc ep tion al b loom even ts
Seafood toxicity associated with exceptional blooms (in
the sense defined in the paragraph on “Nutrients”
above) has a long history in the N orth Atlantic area
(C l). Most reports have related to Paralytic Shellfish
Poisoning (PSP) (C5, B9). More recently, Diarrhetic
Shellfish Poisoning (DSP) has been reported in E u ­
ropean waters (C3, C4, C5, D9). However, the defini­
tion and diagnosis of this syndrome are also relatively
recent and there are earlier records which may be attrib­
utable to DSP.
PSP and DSP result from the consumption of shellfish
which have accumulated toxins produced and contained
in certain dinoflagellates. PSP is associated with the
species variously referred to as Gonyaulax tamarensis or
excavata, while there is some uncertainty about the
causative organisms of DSP; D inophysis acuminata ap­
pears to be the most likely candidate, though certain
Prorocentrum spp. have also been brought into question
in the past. It is important that these taxonomic and
biological issues be cleared up for monitoring and man­
agement purposes; in particular, D. acuminata needs to
be cultured so that its toxicity can be assessed.
A t the time of writing, it is clear that PSP is a recur­
rent problem in some areas of the coastal regions of
New Brunswick, Canada (C2, D4) and New England,
and the USA (C l) in the Northwest Atlantic, and N or­
way ( D l), United Kingdom, Spain (C5), and Portugal
(B9) in the Northeast Atlantic. DSP has been reported
primarily in the N ortheast Atlantic, namely in the N eth­
erlands (C3), France (C4), Ireland (D9), and the Iber­
ian Peninsula (C5).
Monitoring is an im portant tool for management
(C l). Traditionally, monitoring has concentrated on the
incidence of toxic shellfish. Different assays for PSP and
DSP are available (C3, C4); both are bioassays and,
while far from satisfactory, are adequate to provide
basic management information on degrees of toxicity.
However, there is an urgent and continuing need to
update assay methods, to reduce their costs and to make
them simpler and quicker to apply. Recent experience
with DSP suggests that toxicity may occur quite sud­
denly and that monitoring of phytoplankton in addition
to toxicity, may give valuable forewarning.
Unfortunately, monitoring programmes in many ar­
eas are non-uniform. Since information on shellfish tox­
icity is often relevant outside the immediate area af­
fected, there is a need for uniformity with respect to:
(a) standardization of criteria for monitoring station
selection;
(b) intercalibration of assay methods between laborato­
ries;
(c) collection of associated data sets with respect to
meteorology, hydrography, and species composi­
tion of phytoplankton present at the time of collec­
tion;
(d) data presentation and analysis, possibly using
agreed com puter formats.
In this respect, a coordinated archiving of data would be
valuable to improve access and assessment.
Faced with toxicity problems, resource managers
have options including blanket closure, seasonal clo­
sure, and closure in response to monitoring results (C l).
Safe application of the latter requires an aggressive
monitoring programme but has cost/benefit advantages
in that it allows maximum resource utilization.
The greatest negative impact is witnessed when a
monitoring programme is used solely to protect public
health (C l, C3, D9). The seafood industry can suffer
near-collapse when public alarm is raised over “toxic
shellfish” . This can be avoided when the sensitivity of
the issue is acknowledged and the public is made aware
of the risks, causes/effects, etc., by the prompt issue of
balanced factual announcements by the controlling au­
thorities.
Negative “halo” effects include:
(a) decline in marketability of seafoods in unaffected
regions;
(b) decline in marketability of unaffected species within
affected regions;
(c) decline in marketability of seafoods beyond the
time scale of toxicity.
At a national and international level, there is a need to
review and agree upon accepted quarantine and safety
levels. There is also a need for the establishment of
rapid communication networks to report on monitoring
data and management action.
M a n a g e m e n t o f e x c ep tio n a l-b lo o m related problem s in mariculture
I n tro d u c tio n
Fish kills and sub-lethal effects in mariculture have been
particularly associated with the spread of Gyrodinium
aureolum in European waters (B7, C5, C6, D2, D8,
D13), though several other species have been impli­
cated, particularly an unidentified ‘flagellate X ’ (B8,
D2, D8, D12) and, in 1984, the PSP-producing species
G onyaulax excavata (D14). So far, these problems have
been limited to the eastern North Atlantic, though G.
aureolum has recently bloomed in Canadian waters.
Wild, caged, and pond fish, shellfish and marine in­
vertebrate mortality, or reduced growth due to excep­
tional blooms have occurred in many E uropean coun­
tries and have caused substantial economic losses, espe­
cially in Ireland (D8, D9, D12), Scotland (D2), the
Faroes (D14), and Norway (D l).
Ill
The time is now ripe for a synthesis to be made of the
experience of these problems in recent years, so that
advice may be formulated for mariculture managers.
The following paragraphs indicate the main headings
under which such advice should be formulated. There is
a need both for fish farmers to be aware of the factors
listed below and for central government expertise to be
available to provide specialist and site-specific advice,
and to train fish farmers in basic techniques. Licence
conditions for fish farms would include provisions con­
cerning the availability of basic equipment and the
training of personnel.
Predictability - site selection and m onitoring
[t is now possible to identify a series of factors which
allow risk assessment of sites otherwise potentially suit­
able for mariculture ( B l, C l , D2). These should be
professionally examined before production commences;
in general, the fish farmer should gather as much in­
formation as possible about the local, physical, chem­
ical, and biological environment. A distinction needs to
be made between risks of exceptional blooms occurring
in situ close to cages or of the transport of exceptional
blooms from offshore areas to cages.
Key factors in site risk assessment include:
(a) water exchange. High exchange rates will reduce
risks of in situ blooms, but may allow transport
inshore of offshore blooms;
(b) the presence of offshore frontal or upwelling sys­
tems, which may be seed areas for offshore blooms.
(In respect of the first two items, the ideal site is
fully mixed and communicates with a fully mixed
sea area);
(c) accumulation of soft sediments, which may indicate
poor circulation;
(d) nutrient status of local waters;
(e) recorded or surveyed phytoplankton community,
including data on PSP or DSP incidence;
(f) cyst occurrence in local sediments (C6).
Inevitably, there will be some conflict between these
factors in individual circumstances. A risk assessment
for Scottish waters based on local application of these
factors has been carried out by the Scottish Marine
Biological Association (D2).
Especially in identified high-risk areas, it is important
that fish farmers monitor the environment of their cages
and any local areas such as fronts which could give rise
to problems. There is a need for training of fish farmers
in basic techniques, including dinoflagellate identifica­
tion; courses in the latter have been held in Ireland,
Norway, and the U nited Kingdom. (It is important that
the cost of such courses should not militate against
attendance.) Monitoring methods must be as simple as
possible.
112
Offshore events may be monitored using local fisher­
men to collect observations of discoloured water and
water samples. Surface w ater samples may be adequate,
though the use of techniques such as the Lund tube to
obtain integrated water column samples, is preferred.
Initial analysis should concentrate on presence or ab­
sence of key species; more detailed identification and
counting should be limited to high biomass samples.
Near-cage monitoring can be simply carried out with
a basic set of tools including oxygen and temperature
probe, secchi disc, a cheap microscope, and suitable
preservatives for algal samples (D8). All fish farmers
should regularly make records of tem perature and oxy­
gen profiles and secchi depth. The latter serves as a
support to phytoplankton sampling by indicating
changes in water clarity which occur, inter alia, as a
result of bloom development. In high-risk areas, farm­
ers must seek and have available specialist advice and
will need to carry out more extensive monitoring. Some
techniques for bioassay of w ater quality (e.g ., the oyster
embryo bioassay) may be useful in such circumstances
(D3), and research to develop other bioassays using
sensitive species (e.g., Arenicola) o r bio-chemical m eth­
ods, is needed.
Prediction o f specific events
Detailed analysis of w eather patterns, associated with
blooms in both offshore and inshore areas, may allow
the development of a w eather warning-system similar to
that used in terrestrial agriculture for Potato Blight
infestation. Small-scale in situ events are inherently
more difficult to predict, though statistical records of
incidence, w eather patterns, and nutrient conditions
will all be relevant.
For effective short time-scale prediction, data are
needed in real time, both in terms of rapid work-up of
samples and of good centralized communication net­
works which should be government based.
Site m anagem ent
The importance of good cage husbandry was stressed.
While it is not very likely that cages can significantly
affect their local environment by inorganic and organic
nutrient input, every effort should be made to reduce
cage impact (e.g., by avoiding wasteful over-feeding)
(D8). Rotation of cage sites allows the seabed beneath
cages to recover from the effects of rain-out. Limitation
on size of farms according to site conditions is impor­
tant.
General fish health is important in so far as diseased
or parasitized fish will more easily succumb to the ef­
fects of blooms. Conditions suitable for disease or parasitization may also be suitable for in situ bloom forma­
tion, so health may also be a monitoring tool.
In high-risk sites, shore-based installations with al­
ternative shallow or deep intake pipes are a sensible
option.
Where young fish are expected to feed on plankton,
care should be taken on the timing of stocking in rela­
tion to the time of development of toxic blooms.
In some areas, adequate growth may be attained be­
tween early winter and the onset of the bloom season.
In this strategy, trout are the most appropriate fish to
use.
M an agem ent options in b lo o m events
Cage movement, especially in in situ blooms may be a
useful option, but is likely to be impracticable in large
farms or in response to large-scale blooms.
Feeding should be stopped during blooms as it only
increases the stress on the fish (D8).
Early slaughtering of fish may allow some recovery of
stock value (D8). For this approach to be effective, the
species of fish should be m arketable as small young fish
(i.e. trout, not salmon) and freezer or processing facil­
ities should be availabe to avoid sudden m arket gluts.
Biological control does not yet appear to be feasible
and the use of algicides should be strongly opposed. In
both cases, the wrong species may be attacked exacer­
bating blooms; algicides may be toxic to fish.
More experimental research is needed on:
(a) deep cages (penetrating the thermocline and allow­
ing fish access to sub-thermocline water);
(b) cage lowering (for the same purpose).
Observations that forced vertical circulation of water
through cages (using pumped air ventouri systems) re­
lieves the symptoms of G. aureolum effects require
corroboration and further experiment (D8). There is no
good theoretical basis for these observations as yet.
Appendix
Proposals and recom m en dation s o f the m eeting
There is an urgent need to improve spatial and temporal
coverage of phytoplankton data. In particular:
(a) Existing data sets should be assembled and re-in­
vestigated, particularly to compile time series.
(b) Cross-calibration of CPR and other instruments
(e.g., fluorimeters) for recording plankton data is
needed.
(c) Examination of recent sediments from non-bioturbated accumulating areas to establish time series of
phytoplankton activity from cyst and pitment records
should be carried out (perhaps in conjunction with cur­
rent ICES sediment pollution studies).
(d) The application of remote sensing to these prob­
lems should be examined in detail, including the use of
existing aircraft surveillance operations and aircraft of
opportunity. ICES should put pressure on the E u­
ropean Space Agency to provide an Ocean Colour In­
strument as soon as possible.
With respect to questions of eutrophication:
(a) A ttention should be focussed not on bloom inci­
dence but on the overall patterns of annual biomass.
(b) A ttention should be focussed on coastal and estuarine areas in which terrestrial inputs are significant in
relation to the “pool” of nutrients in the sea (in partic­
ular to the New York Bight, the Southern and G erm an
Bights of the North Sea, the Kattegat and areas of the
Baltic Sea, and areas such as the Oslofjord, and the
more enclosed estuaries).
(c) Research is needed on the role of organic sub­
stances in phytoplankton production, including organic
nutrients, vitamins, and natural chelating agents, espe­
cially where they may be components of sewage and
other organic wastes.
Research is needed on the biology of species which
cause exceptional blooms:
(a) Knowledge of life cycles, in particular of resting
stages, is lacking in many species.
(b) Taxonomic and related confusion needs to be
cleared up, in particular with respect to Gonyaulax tamarensis! excavata, ‘flagellate X ’, and the causative o r­
ganisms of DSP; ICES is urged to press ahead with
publication of its leaflet series on Plankton Identifica­
tion, which will include phytoplankton species.
(c) More information is needed on growth rates of ex­
ceptional bloom-forming species.
With respect to exceptional blooms posing public health
risks:
(a) D evelopment of improved rapid toxin assays and
cross-calibration of techniques is needed.
(b) Monitoring of phytoplankton as well as toxicity
should be carried out especially in DSP-affected areas.
(c) National action is needed in some countries to har­
monize monitoring programmes and to ensure rapid
information flow to resource managers. Calm and
prompt public statements are essential to limit negative
impact on commercial fisheries, especially molluscan
shellfisheries.
(d) International action is necessary to ensure rapid
flow of information on toxic events and to review and
harmonize safety and quarantine levels.
With respect to problems posed by exceptional blooms
for mariculture, it is proposed that the preliminary
statement in the section on ‘M anagement of excep­
tional-bloom-related problems in mariculture’ should
113
be worked on further by a new ICES Working G roup on
the M anagement of Problems Posed by Exceptional
Blooms for Mariculture with the following terms of
reference:
(a) to establish means to collect and exchange informa­
tion on the incidence of problems due to excep­
tional blooms on mariculture operations;
(b) to consider means of improving the predictability of
bloom events on time - and space - scales relevant
to fish farmers, including analysis of weather p at­
terns in relation to bloom incidence,
(c) to consider proposals for research into management
techniques for overcoming the effects of excep­
tional blooms,
(d) to prepare advice for M em ber G overnments and
for fish farmers on site selection, monitoring and
prediction, and management options for bloom
events.
114
Member States of ICES should be encouraged to con­
tinue to submit data on the incidence of exceptional
blooms and related events to A nnales Biologiques for
publication in the section dealing with this issue, com­
piled by D r J. P. Mommaerts.
Selected papers from this Special Meeting should be
published in the Rapports et Procès-Verbaux series, un­
der the editorship of D r M. M. Parker and D r P. Tett.
A c k n o w le d g e m e n t s
I wish to thank the participants in the evening discussion
groups, and especially Paul Tett and Kathy Richardson,
for valuable discussion and assistance in preparing this
report. My thanks also to the ICES Secretariat for mak­
ing it possible to produce the first draft of this report
during the Statutory Meeting.