viously, sample sites should be chosen
to avoid such areas if possible.
Clearly, there is room for questions
or criticism when this dynamic system is modelled from the assumption
that bottom sediments, for example in
Anderson s work in The Gulf of Maine,
are in a static stable condition whereby
a sample taken in the fall one year is
considered representative of the seed
bed the following spring. The fall sample
may well contain many freshly formed
cysts from that summer s bloom, but by
next spring these would be expected to
be at least partially disseminated into
deeper sediment and possibly replaced
by some older cysts of more questionable viability by the processes mentioned
above. The crucial question for modelers of how many viable cysts germinate
from the proposed seed bed to initiate
the next bloom will always be difficult/
practically impossible to demonstrate.
How can one know which cysts from
the variety of seed beds in shallower to
deeper water, potentially excysting at
different times, produce which motiles
in the water column in coastal regions
with a complex interconnected hydrographic system offering different ecological opportunities? Modelers promising long-term forecasting of HAB from
cysts in sediment should be expected to
take account of the basic factors affecting the sediments, and they are obliged
to check simple assumptions made
about sediments where possible. For
example, if modelers of HAB in the Gulf
of Maine had calculated cyst concentrations in the postulated seed bed closer to the postulated time of excystment
in the spring, and checked cyst concentrations again soon after excystment,
they could see if cyst concentrations
were reduced by the amounts required
to support the excystment rates assumed in the models. One of the often
stated justifications for modeling is that
it can expose aspects of science needing
further study. I hope the modelers will
accept the explanations presented here
as an example of this: that inadequate
consideration of the dynamics in the
sedimentary system contributes to the
high level of uncertainty in the models.
Behind Andersons complaint about
unjust criticism from geologists lies an
important principle that is fundamental to how science progresses: scientists have a responsibility to question/
criticize each others work. This is particularly valuable where different disciplines overlap (in this case biology and
geology). Geologists know that water
content varies between sediment samples, and biologists were made aware of
this only when they were not accounting for it in their work. There are simple, standard methods for checking water content, and these were eventually
employed by biologists to account for
this factor surely a positive response
to valuable criticism.
From working with both geological
and biological aspects of dinoflagellate
cysts, I have benefitted greatly from
being exposed to and learning from expertise in both fields. I know that HAB
science will only benefit from a better
understanding of the dynamics of the
sedimentary system.
References
1. Anderson DM 2018. HAN 59: 4-8
2. Dale B 2001. Sci Total Environ 264: 235240
3. Dale B & M Murphy 2014. Harmful Algae
40: 23-33
Author
Barrie Dale, Geosciences Department,
University of Oslo, P.O. Box 1047, Blindern,
NO-0316 Oslo, Norway
Corresponding author:
barrie.dale@geo.uio.no
HAN contributors follow an honorable tradition of disputation; differences instead of differentials. Figure shows
Isaac Newton and Leibniz, protagonists of the most famous intellectual dispute in history.
HARMFUL ALGAE NEWS NO. 60 / 2018
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