Boyle Project 15.pdf

E O S 4 0 3 : F i n a l Y e a r P r o j e c t
Oceanography of Dinophysis blooms in the
Northern Celtic Sea.
Dylan Boyle
January 2016

EOS403: Field Project/Honours Dissertation
2
Table of Contents Page
0.1 Abstract 3
1. Introduction 4
1.1 Plankton. 4
1.2 HABs. (Harmful Algal Blooms). 4
1.3 HAB problems in Ireland. 5
1.4 Coastal Transport.. 5
1.5 Coastal Jets 7
1.6 Project Aims. 8
2. Methods 9
2.1 Study area. 9
2.2 Field Methods. 9
2.3 Lab methods. 12
3. Results 13
4. Significance of Data Set. 19
5. Discussion 23
6. Conclusion 25
Acknowledgements 27
References 28

3
ABSTRACT
An oceanographic survey was carried out off the south east coast of Ireland during July 2015 to
investigate the origin of populations of a toxin producing dinoflagellate genus Dinophysis. They
regularly contaminate the shellfish culture along the south and south west of Ireland. Particular
attention was paid to the region around the vicinity of the Celtic Sea Front where high cell densities of
up to 6,900 L-1
of D. acuta and 2,500L-1
of D. acuminata were observed. Analysis of samples taken
from the same area in June 2015 showed that the population increased significantly, particularly for D.
acuta. Samples were taken at different stations using Niskin bottles in a rosette arrangement. Results
indicated that these populations were transported out of the region with coastal currents where they
would ultimately impact shellfish aquaculture areas more than 200km away from their presumed
source.

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CHAPTER 1: INTRODUCTION
1.1 Plankton
Plankton are a varied group of small aquatic organisms who reside in both fresh and salt
waters around the world. They are unable to swim against ocean currents so they are free-
floating in the water column. It is a very broad group as it includes both aquatic animals
(Zooplankton) and aquatic plants (Phytoplankton). Like any other plants, this algae group are
photosynthetic, using chlorophyll to convert carbon dioxide into oxygen. Phytoplankton can
be divided into bacteria, protists but most are singular celled plants. The major groups within
phytoplankton are diatoms, coccolithophores and dinoflagellates. The main focus of this
report will be on dinoflagellates. These are unicellular biflagellated algae that make up a large
part of phytoplankton community. These organisms are typically less than 1mm, too small to
be seen by the naked eye, but when they start to reproduce whenever conditions are favorable
for them, they can be seen as discoloured patches in the water column due to their chlorophyll
pigments. These organisms only start to bloom when conditions for them are favorable,
usually in the summer months when the ocean surface temperatures are warmer and the
waters begin to stratify.
1.2 HABs (Harmful Algal Blooms)
The blooms themselves are given the name HABs (Harmful Algal Blooms) and there are two
types. The first is called a "High biomass bloom" and can be recognized by discolored water
patches (Karenia mikimotoi) foaming and odours (Phaeocystis globosa). This can also
generate asphyxiation in the water column due to the high biomass leaving dead zones
(eutrophication Mississippi Gulf). Asphyxiation is caused by the high biomass blooming
dinoflagellate species utilizing all the oxygen available in the water column and leaving other
organisms unable to respire. The second type of HABs are toxic blooms. These occur when
biotoxins produced by dinoflagellate species cause a number of problems for both marine
organisms and humans. Some coastal bay areas have HAB species which bloom annually and
impact at a local basis, this is due to a dormant stage in the species life cycle which allows
them to overwinter in sediments and then, when the surrounding conditions are favorable,
they bloom. These populations are retained in the bay if the flushing rate in the bay area is
low compared to the rate of reproduction of the HAB species. (Raine, 2014). Harmful

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phytoplanktonic species can also be carried to areas of impact by currents. Weak physical
forces (i.e. tides, flushing rates, meteorology.) can cause blooms to form in situ due to the
impact these HABs can have on human health, biological resources, tourism, recreation and
seafood cultivation, it is now a regulation for the EU to try to the best of their ability to
monitor these blooms. ASIMUTH was founded as an alert system for Europe. The idea is to
try and predict a coming bloom and take the necessary steps in order to prevent it from doing
damage. Areas in Western Europe are annually hit hard by these toxic blooms where their
shellfish population get contaminated by these toxins, most notably DSP (Diarrheic Shellfish
Poisoning) (van Egmond et al., 1993; Reguera et al., 1993; Palma et al., 1998; Xie et al., 2007;
Raine et al., 2010).
1.3 Harmful Algal Bloom problems in Ireland.
Coastal bays and areas around Ireland are affected each year by HABs. When toxic events
arise, very often contamination is by the Dinoflagellate genera Azadinium (producing AZP
toxins) or Dinophysis (producing DSP toxins). The dinoflagellate Azadinium spinosum
produces these AZP toxins (azaspiracids) which are a group of polycyclic ether. When
shellfish that are contaminated by these toxins are ingested by humans, they can cause
illnesses such as nausea, vomiting, diarrhea and stomach pains. They are monitored very
closely in Ireland due to an episode where several reports of AZP around different European
countries in 1995 due to consumption of Irish mussels. The Marine Institute regularly samples
water in Bays around Ireland for presence of toxic phytoplankton. DSP (Diarrhetic shellfish
poisoning) is caused by Okadaic acid (OA) and Dinophysis toxins (DTXs) released by
Dinophysis species D. acuminata and D. acuta. Eating shellfish contamined by these toxins
causes the same illnesses as AZP (nausea, vomiting and stomach pains). This becomes
problematic as the South West coast of Ireland has a massive shellfish industry which year
after year becomes victim to these blooms. 80% of Irish blue mussel (Mytilus edulis) rope
cultivation and 50% of the national pacific oyster (Crassostrea gigas) production occurs in
this region (Parsons, 2005). This south west region also has many salmon farms and
development sites for European and Japanese species of abalone (Haliotis tuberculata and
H.discus hannai), the queen scallop (Chlamys opercularis) and the purple sea urchin
(Paracentrotus lividus) which highlight the productivity of the industry in this region (Farrell
et al. 2012). Despite the high productivity of the shellfish industry in this region, it is hit hard
every year by HAB events. This results in extended closure of shellfish farms year after year

6
due to the diarrhetic shellfish poisoning toxins contaminating the shellfish rendering it unfit
for human consumption. This is a massive problem for people involved in the shellfish
industry as the closure of these farms proves to be very costly each year due to loss of sales,
around 10,000 tonnes of mussel is rendered unfit for consumption each year and also the cost
involved in disposing of the contaminated shellfish in a proper manner. This poses the
question as to how do these phytoplanktonic toxins arrive in these bays each year.
1.4 Coastal Transport
Harmful algal events caused by Dinophysis and Azadinium, arise through the physical
transport of populations into the coastal bays. This has been generally deduced from the
extremely rapid increase in cell numbers and toxins during a HAB event. For South West
Ireland it is known that the transport mechanism is through wind driven exchanges. High
resolution waters samples taken from bays around the south west of Ireland have shown that
populations of both Karenia and Dinophysis develop very rapidly and coincide with water
exchanges between the bay and adjacent shelf (Raine et al., 1993, 2010). This exchange is a
result of the axial alignment of the bay and with the prevailing southwest wind direction
(Edwards et al., 1996). this wind driven two layer oscillatory flow in the bays has been used
for the forecasting of HAB events within Bantry bay (Raine et al., 2010). In Bantry bay the
DSP events of 1994, 2001, 2002 and 2005 have all been linked directly to Dinophysis being
carried into the bay with warm surface water following water exchanges between the bay and
the adjacent shelf.
There is growing evidence that the HAB populations are transported along the shelf in coastal
currents. The transport of these phytoplankton (and other constituents such as nutrients and
contaminants) occur in so-called jets in the summer month. These provide the principal
thermohaline transport pathways on the northwest European continental shelf (Hill et al.,2008)
which extends along the south and western coast of Ireland. Increasing evidence shows that
these current flows play a big part in the transport of toxin producing phytoplankton to these
bays. Large cell numbers of K. mikimotoi have been found along sections of the current
pathways. Recent data collected also shows the direct transport of a population of Dinophysis
acuta in high density as a thin sub-surface layer within a coastal jet along the south coast of
Ireland (Farrell et al., 2012).

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1.5 Coastal Jets.
Coastal Jets have become a large point of interest since the idea of their involvement in
transporting harmful phytoplankton from bloom areas to areas where they can cause damage
to shellfish farms and other forms of aquaculture. When trying to prevent the damage these
blooms cause and predict them in advance before they migrate, a knowledge of the physical
processes involved in coastal jets is needed. A coastal jet can be described as along shore
flows as a response to the increase in tidal mixing, relative to water depth, as the water
column starts to shallow closer to the coastline. Stratification of the water column is required
for these jets to operate. The jets are narrow (ca. 5km) and run along the coastline. These
flows are fast at their maximum of the order of 20-25 cm s−1
relative to the flow of the sea bed.
There is vertical heterogeneity of the flow and is fastest at the depth of adjacent pycnocline,
concentrations of phytoplankton and other harmful species are often found in high densities at
this depth. Coastal jet locations are indicated by the presence of bottom density fronts, where
the isopycnals are found close together. They not only occur along coasts which are adjacent
to thermally stratified waters but also along the stratified side of tidal fronts (Raine, 2013).
Coastal jets are described by Brown et al. (2003) around the Celtic Sea with clear illustration
that the flows not only along the coast but also along the tidal front (Celtic Sea Front). It
showed that the dynamics of large areas of the European continental shelf are largely
controlled by these dome like density gradients which are associated with dense water which
was isolated by the formation of the seasonal summer thermocline. It showed that these flows
persisted well beyond the depth of which wind driven exchanges would have affect until
convective overturning would bring about the complete breakdown of the dense pool. The
strong nature of these flows is an integral part of how the blooms were transported into areas
of impact. Hill et al. (2008) summarized the distribution of coastal jets around north west
Europe. It solidifies the point that these jets are an important non-tidal mechanism of transport
around the north west European continental shelf in summer time when the water column
starts to stratify.
Brown et al. (2001) also refer to coastal jets as a transport mechanism, although it deals with
coastal jets off the north east coast of England and discusses about the the phytoplankton
Alexandrium it was the first paper to link the two together. It made the connection that
harmful algal blooms may not have originated at the source of impact but that they were

8
transported through these coastal jets. It was hypothesized that the concentrations of
Alexandrium bloom annually in East Scotland and further south there was high concentrations
found along the coastal jet tract so this paper made the link between Harmful Algal Blooms
and coastal jets. Farrell et al. (2007) shows the transport of toxic Dinophysis blooms in the
coastal jet between Cork and the south west. From the knowledge of coastal jets we now
know that these phytoplankton communities would travel around to different bays in Cork
(Dunmanus, Bantry, Castletownbere) This paper is of interest as it shows the damage that
these blooms cause to the bays around Cork each year in the summer. The extended closure of
these shellfish farms due to toxic phytoplankton is one of the main reason for this survey.
Raine (2014) is a general review of the link between harmful algae blooms events and the
physical oceanography which control their transport. This paper highlights that Ireland can be
susceptible to HAB episodes due to its temporal climate and the waters can thermally stratify
in the summer months which provides a favorable environment for harmful phytoplanktonic
species to thrive due to the light and nutrients resources available. It also highlights that the
continental shelf around Ireland is tidally energetic so conditions can fluctuate between
thermally stratified and tidally mixed and the water depth is shallow (<200 m) so the general
thermohaline circulation pattern of currents around the coast is not interrupted by weather.
These thermally stratified water columns can result in the formation of near shore coastal jets
which can transport harmful phytoplanktonic species in very thin sub-surface layers.
1.6 Project Aims.
This project was carried out to try and source the origin of the these Dinophysis populations
by examining their distribution throughout transects off the south east coast of Ireland in the
Celtic Sea front, and also with reference to coastal waters which were known to contain high
densities of Dinophysis in thin over two surveys which were carried out within the first week
in June 2015 and the second week in July 2015.

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CHAPTER 2 : METHODS
2.1 Study Area.
This image shows the route taken by the CV15017 between 13th
-17th
July 2015. Previous
surveys concluded that the precise origins of Dinophysis populations remained unresolved,
they suggested that a likely source was on the northern section of the Nymphe Bank and
towards the area of the Celtic Sea Front. So this survey was to investigate the origins in both
location and depth these phytoplanktonic communities could be found and also how far they
can be found upstream in coastal jets.
Field Methods:
During this survey, station locations were based on a previous survey which was carried out
during June 2015. A CTD (Conductivity, Temperature, Depth ) (Seabird 911) was deployed at
the stations marked in fig.1. The instrument which was also equipped with a transmissometer,
and a fluorescence meter, this lowered into the ocean via winch from the starboard side of the
vessel. The Seabird 911 fed real time information from a large conducting cable connecting
Fig. 1 Areas sampled throughout the CV15017 survey on the Prince Madog. Image was generated from
the Admirably chart series using Maxsea during the cruise.The circular markers on the map show stations
sampled. Each fifth station is marked in blue with a station number and the two fine scale sampler stations
are marked in black.. Red lines represent the route taken by the ship to travel to different stations while no
sampling was done.

10
the CTD to a monitor back in the wet lab to a computer program called sea-save. This model
had 12 niskin bottles (10 L) in a rosette arrangement attached to it which could be
individually fired from the computer in the wet lab at depths of particular interest. Once a
bottle is fired via the wet lab, the instrument records data from the water column from two
seconds before to two seconds after firing. The instrument package was lowered through the
water column and this began to record different profiles on the screen (Depth, density, salinity,
fluorescence, and transmission). Based on the results of these profiles it was decided at which
depth the Dinophysis and other plankton species were most likely to reside and which depths
to collect waters samples to be analysed back in lab. As the instrument package made it’s way
down the water column, the niskin bottles were fired on the up cast at different depths
collecting waters samples of different properties based on the information from the down cast.
This hopefully could give an idea at which depths the plankton were resided in. While firing
the bottles at different depths log sheets were also maintained to supply as much information
on the areas as possible. Longitude, latitude, salinity, hull temperature and the areas sounding
was provided by an underway system on board. The log sheets also had to have depths, UTC
time salinity, temperature V4 and V6 wrote down too. These were provided by the sea save
program. The same process was carried out at all 98 stations, deploying the CTD instrument
package, collecting the water samples, and then cocking the niskin bottles again preparing
them for the next station. Once on board, samples were collected in individual 2 litre sample
containers. Each sample container had a number which matched the number on the niskin
bottles. Care was taken to wash the container with the water sample from the matching bottle
so that any previous water samples from previous stations would not contaminate the sample.
The 2 litres were passed through a filtering disc which had a mesh size of 20 microns so that
the possible Dinophysis and phytoplankton samples were left resided on the filter. The
remained plankton species on the mesh were collected in 50ml tubes which were brought up
to 30ml with pure filtered sea water. Two drops of Lugols iodine was added to the tube to
preserve the sample and were refrigerated at 4°C. When placing the samples to be cooled in
the refrigerator, they were labelled with the date and station number before storage.
In areas of particular interest a fine scale sampler was used, which was set up in much the
same way as the CTD except that the niskin bottles was arranged horizontally on a bracket
instead of vertically. The fine scale sampler gives a more detailed description of the
distribution of plankton layers so it was only used in limited areas where there was suspected
plentiful distribution of plankton. Log sheets were maintained during these plankton samples,

11
with the station number, sample depth, longitude, latitude, hull temperature, salinity, UTC
time and event number to make it easier for future analysis.
Fig. 2 View from above of the CTD being
deployed into the water column at a station
via winch from the starboard side of the
ship.
Fig. 4 Water sample being collected in a
50ml tube after being passed through a
filtering disk of mesh size of 20 microns,
and the volume is brought up to 30ml by
addition of pure filtered sea water.
Fig. 5 Lugols iodine being added to the
sample to preserve it before being
transferred to the refrigerator.
Fig. 3 Water sample being collected from the
niskin bottle after the CTD instrument was
hauled back onboard.

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Lab Methods.
Once all the samples from the Celtic Sea were collected they were transferred back to NUIG
where cell densities were counted in the laboratory. Errors on phytoplankton estimations were
reduced by using a Utermöhl chamber technique (McDermott and Raine, 2010). Samples
were prepared for counting by taking a sample bottle and inverting it gently approximately
10 times, ensuring fair cell distribution throughout the bottle. A pipette was placed in the
bottle roughly around half way and a 3ml sample was taken out and transferred onto a 3ml
well slide chamber where it would be examined under the microscope at a magnification of
X20. For the counting process half the base was counted and from this result it could be
determined cell densities per 2 L, could be determined. A log sheet was kept for each sample,
where the genus and species (if possible) were identified using light microscopy. It was also
noted if the cell was vacuolated and if pairs were present. Once all stations were counted the
data was transferred into an excel file in order to construct graphs of cell distributions. Surfer
7.0, a contouring and surface modeling program was used to construct Dinophysis cell density
graphs and plot their distribution against isopycnals.
Fig. 6 The standard optical Nikon
microscope that was used in the cell
counting process.
Fig. 7 The Utermöhl chamber where
samples were placed.

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CHAPTER 3 : RESULTS
Satellite images of sea surface temperature were obtained from www.neodaas.ac.uk website.
Vertical profiles of water temperature revealed that the water column was well stratified,
density contours indicating a strong pynocline to depths of over 25m. Profiles of the vertical
water column taken on both these trips show that there is a change in temperature not just on
the surface.
The satellite images of sea surface temperature show that the surface waters heated up
substantially over the course of a month, there is a contrast between the warm stratified red
and the cooler tidally mixed water in yellow/orange with temperatures ranging from 13-15°C.
The satellite image taken during the June survey (Fig. 8) highlights the degree of warming
over the course of a month. In the July satellite image the Celtic Sea Front is clearly visible
between thermally stratified water and tidally mixed water between Carnsore point and
Wales ).
Fig. 8 Satellite image of sea surface temperature
taken of the study area during the June(3rd
) cruise
with colour bar indicating temperature (°C)
Fig. 9 Satellite image of the sea surface
temperature (°C) of the study area during the July
(15th
) cruise with colour bar indicating temperature.

14
Figure 12 shows the distribution of temperature along a section from the June cruise between
stations 82 and 110. Surface temperatures ranged between 10-12 °C. Below this at depths of
60-80 m the water column it ranged between 9-10 °C. Figure 13 shows the temperature
distribution in the water column from a similar area to that of the June cruise but the data
were generated over a month later. Surface temperatures had risen to over 15 °C at stations 94-
98 and throughout the water column it is evident that there was a substantial heat influx over
the course of a month creating a healthy stratified water column.
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9.5
10
10.5
11
11.5
12
12.5
13
13.5
14
14.5
15
15.5
Fig. 12 A temperature profile of the
vertical water column throughout a
transect on the June (3rd
) cruise with
colour bar indicating water temperature
°C. Numbers over the top of the figure
represent station number.
Fig. 13 A temperature profile of the vertical
water column throughout a transect on the July
(14th
) cruise with colour bar indicating water
temperature. Numbers over the top of the figure
represent station number.
Fig. 10 The area where the
temperature, salinity and density
profiles were taken during the June
cruise.
Fig. 11 The area where the temperature,
salinity and density profiles were taken during
the July cruise.
Distance (km) Distance (km)

15
Temperature is the dominant influence on density distribution and ultimately the stratification
of the vertical water column but included is Figures 14-17 shows salinity profiles and density
distribution from both the June and July surveys. When comparing the salinity and
temperature profiles, the temperature contours match up better with the density density
contours. Profiles are taken from the same transect areas are the temperature profiles were
taken in figures 12 and 13, the July transect includes stations 83-98 and the June transect
includes stations 82-110.
Fig. 14 Distribution of salinity along a section
on the June (3rd
) cruise. Station
Numbers are the same as Fig. 12 (82-110).
Colour bar represents salinity values.
Fig. 15 Distribution of salinity along a section
on the July cruise (14th). Station numbers are
the same as Fig. 13 (83-98). Colour bar
represents salinity values
Fig. 16 Density contours throughout a
transect on the June (3rd
) cruise. Station
numbers are the same as figures 12 and
14 (82-110).
Figure 17 Density contours throughout a
transect on the July (14th
) cruise. Station
numbers are the same as figures 13 and 15 (83-
98).

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0 5 10 15 20 25 30 35 40 45
Distance (km)
50
40
30
20
10
Depth(m)
82 84 86 88 90 92 94 96 98
0 5 10 15 20 25 30 35 40 45
Distance (km)
50
40
30
20
10
Depth(m)
82 84 86 88 90 92 94 96 98
Figures 18 and 19 show the distribution of Dinophysis acuta and D. acuminata from the June
cruise along a line of stations depicted in Figure 20. As expected the cell counts are quite low,
presumably due to the water column having not yet begun to stratify so the environment was
not yet favorable for the blooms to flourish. Cell counts were generally between 30-300 cells
L-1
. D. acuta concentrations were between 100-300 cells L-1
between stations 82-90 at depths
below 30m while stations 90-98 had concentrations of 30-100 L-1
. The concentrations of D.
acuminata were the same in respect to cell density but the distribution was more constant.
Stations 82-92 had cell concentrations of 100-300 L-1
from below 40m while the rest of the
transect seen cell densities between 30-100 L-1
through the full water column. Although the
Dinophysis were present at these stations, conditions were not yet favorable to initiate a
bloom where cell numbers would be harmful to aquaculture. These stations were sampled
along a similar transect during the July cruise across the Celtic Front region south of Ireland.
Fig. 18 D. acuta densities from the June cruise (6th and
7th
) from area around the Celtic Sea Front. Density
contours (black lines) were extracted from CTD data
and plotted against Dinophysis concentration samples
at stations through the water column (pink dots).
Fig. 20 Location of stations (heavy black line) for data shown in figures 18 and 19.
Station Numbers Station Numbers
Fig. 19 D. acuminata densities from from June cruise (6th
and
7th
) from area around the Celtic Sea Front. Density contours
(black lines) were extracted from CTD data and plotted
against Dinophysis concentration samples at stations through
the water column (pink dots).

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71 72 73 74 75 76 77 78 79 80 81 82 83 71 72 73 74 75 76 77 78 79 80 81 82 83
0 5 10 15 20 25 30 35
Distance (km)
60
50
40
30
20
10
Depth(m)
0 5 10 15 20 25 30 35
Distance (km)
-60
-50
-40
-30
-20
-10
Depth(m)
-1000
0
30
100
300
1000
3000
10000
Figures 21 and 22 represent the results of D. acuta and D. acuminata counts from stations
71-83 from the July cruise going from stratified to mixed waters. Over the course of a month
there has been heating and stratification has developed in this area which will allow an
environment favourable enough for these Dinophysis populations to bloom (as seen by the
temperatures differences in figures 12 and 13). In comparison to the results from the June
cruise the cell densities are much higher (> ten fold) particularly for D. acuta. The density
contours clearly show that the water column has stratified over the course of the month and
there is a well developed pycnocline. The stratified
Fig. 21 D. acuta densities from the July (16th
)
cruise from across the Celtic Sea front
between Ireland and south Wales.
Distributions are plotted with water density
(sigma-theta) which clearly shows
stratification on the west (left) side of the
front. Density contours were extracted from
CTD data and plotted against Dinophysis
concentration samples at stations through
the water column (pink dots).
Fig. 23 Location of stations sampled (heavy black
line) going from stratified to mixed waters for data
in figures 21 and 22.
Fig. 22 D. acuminata densities from the same
area as fig. 21. Distributions are plotted with
water density (sigma-theta) which clearly
shows stratification on the west (left) side of the
front. Density contours were extracted from
CTD data and plotted against Dinophysis
concentration samples at stations through the
water column (pink dots).

18
side of this front sees large densities of cells particularly of D. acuta at stations 71-74
between 10-30m where numbers exceeded 3000 cells per litre. The high D. acuta densities
seemed to follow the density contours to the surface where up to station 81 there was still
recorded values of over 1000 cells L-1
. The rest of the water column did not have cell
densities that high, ranging between 300-1000 cells L-1
. D. acuminata had a constant density
throughout the transect with numbers between 30-1000 cells per litre
0 5 10 15 20 25 30 35 40 45
Distance (km)
50
40
30
20
10
Depth(m)
83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
0 5 10 15 20 25 30 35 40 45
Distance (km)
50
40
30
20
10
Depth(m)
83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
For stations sampled across the Celtic Sea Front in the area marked in Fig. 26 there was quite
high densities so these Dinophysis populations were well developed along the front region.
Numbers were particularly high for D. Acuta (Fig. 24) at stations 83-86 in around the 30m
depth in the front region where they were over 3000 cells L-1
. Outisde this region (stations 86-
98) cell densities were much lower with <1000 cells L-1
. D. acuminata (Fig. 25) densities
were fairly constant throughout the Celtic Sea front transect with cell numbers >1000 cells L-1
and stations 83-84 also around the 30 m depth mark seeing quite high densities of around
3000 cells L-1
. The high cell densities of D. acuta seemed to coincide with the sharp density
contours and follow them to surface waters, where there was still high cell counts at surface
level between stations 88-90.
Fig. 24 D. acuta densities from the July (16th
)
cruise across the Celtic Sea Front south of
Ireland and south Wales.
Fig. 26 Location of stations sampled (heavy black line) going across the
Celtic Sea front for data shown in figures 24 and 25.
Fig. 25 D. acuminata densities from the
same area as fig. 24.

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CHAPTER 4 : SIGNIFICANCE OF THE DATA SET CONCERNING TOXIC
DINOPHYSIS BLOOMS AND THEIR IMPACT ON AQUACULTURE IN
SOUTHWESTERN IRELAND.
The observations of significant high Dinophysis cell densities in July warrants investigation
of how quickly they could arrive off southwestern Ireland in the coastal current, together with
a study of the toxic phytoplankton data from monitoring stations around southwest Ireland.
In areas where the highest cell densities of Dinophysis were found around the frontal area,
current speeds can be estimated from the density distributions. These were obtained by
measuring the dynamic heights of the water column between stations 83-98.
0 5 10 15 20 25 30 35 40 45
Distance (km)
50
40
30
20
10
Depth(m)
83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
Intervals of 20km were taken in both the vertical depth (m) column and the horizontal
distance (km) column and the densities were found to be the following.
Distance (km)
Depth range (m)
0 20 40
0-20 1026.10 Kg/m3
1026.00 Kg/m3
1025.80 Kg/m3
20-40 1026.10 Kg/m3
1026.10 Kg/m3
1026.30 Kg/m3
40-60 1026.10 Kg/m3
1026.20 Kg/m3
1026.80 Kg/m3
Fig. 27 Density distributions along stations 83-98 from July
16th
which were used to calculate current speeds.

20
The dynamic height was calculated at each point by using the equation 1000*dz/ where
dz=depth interval and  is the appropriate density. Units are in dynamic meters and the
results were as following.
Distance (km)
Depth range (m)
0 20 40
0-20 19.491277 19.4931774 19.496978
20-40 19.491277 19.4912777 19.4874793
40-60 19.491277 19.4893783 19.4779899
The following below are values for dynamic heights throughout the water column from
stations 83-98. Units are in dynamic meters and the results are as following.
Distance (km)
Depth range (m)
0 20 40
0-20 58.47383 58.47383 58.46245
20-40 38.98256 38.98066 38.96547
40-60 19.49128 19.48938 19.47799
The current speeds were then found by using the following -g * (sum difference) / 10-4
* dx *
1000 where g=-9.81 and dx= distance interval.
Current speeds (cm s-1
) estimated using dynamic heights along the line of stations between
station numbers 83 and 98.
Distance (km)
Depth range (m)
0-20 20-40
0-20 0.00 -0.06
20-40 -0.01 -0.07
40-60 -0.01 -0.06
So for these current speed values per second the average speed per day was found to be
around 5-6 km.
Sum(1)
Sum(2)
Sum(3)

21
With a distance of over 200 km between the region close to the Celtic Sea Front and the
mouths of the bays of southwestern Ireland, then the time required to travel this distance
within the coastal jet would be 33-34 days, or just over a month.
It is quite clear that the cell densities of D. Acuta in particular rise substantially around the 4th
week in August 2015. This is consistent with the data set generated during this project and
the idea that populations of toxic Dinophysis are growing at the Celtic Sea Front and are then
transported along the south coast of Ireland in the coastal jet to the region of intensive
shellfish aquaculture, southwestern Ireland.
The following data sets were collected from the Marine Institute website which show cell counts
between June 1st 2015 - 31st December 2015 of Dinophysis per litre for bays around the South West
of Ireland, including Dunmanus bay, Castletown bere and Bantry (North Chapel).

22
Where the stations 83-85 were sampled the co-ordinates were 52 lat deg 8.12 lat mins and 6
long deg 7.92 long mins. From this point to the mouths of the bays of Cork is 51 lat deg 3.649
lat mins and 9 long deg 8.2727 long mins it is a distance of 262 km with a further 20km to the
inside of Dunmanus bay. With the current speeds calculated to be around 6km and the
distance being around 282km between Dunmanus and the Celtic sea front it would take the
Dinophysis around 40 days to impact aquaculture in this bay, using time = distance/speed -
time = 282km/6km = 47 days. With the samples at stations 83-85 being taken on the 16th
of
July, then Dummanus would see a increase in Dinophysis numbers by the end of August/start
of September which is exactly what was observed with cells per litre being recorded at 1480
L-1
for D. acuta and 680 L-1
for D. acuminata on August 31st
.
Similarly for Castletownbere, the distance from the stations sampled is around 280km, which
again would point to an increase in Dinophysis numbers in around the start of September
which was observed on the 2nd
of September with D. acuta numbers reaching over 4040 cells
L-1
and D. acuminata reaching 1880 cells L-1
.
Bantry Bay seen an increase in the second week in September with D. acuta being recorded at
4360 cells L-1
and D. acuminata being recorded at 1160 cells L-1
.
When comparing the increase in Dinophysis numbers in coastal bays around South/South
West Cork to the numbers recorded around the Celtic Sea Front in July, it seems feasible that
Coastal jets are the transport pathway for these populations.

23
CHAPTER 5 : DISCUSSION
Dinophysis acuta and D. acuminata produce the highly potent toxins okadaic acid and its
derivatives (DTX 1, DTX2,). The potency is so high that a cell density of only 200 cells L-1
can contaminate a shellfish aquaculture production area (Van Egmond et al., 1993). It is
highly remarkable that cell densities were found to well be in excess of 200 cells L-1
in the
July cruise. Blooms of these harmful dinoflagellates can be transported along the continental
shelf in coastal jets and from there wind driven exchanges can aid these blooms travel into the
bays where they contaminate the product of these aquaculture farms. Coastal jets are
important in relation to the transport of these blooms. These jets have been linked to the
transport of populations of Karenia mikimotoi in the past (Vanhoutte-Brunier et al., 2008)
which have been found at high densities along the coastal jet pathway around the south west
of Ireland with intense densities around the Celtic Sea Front (Raine, 2014). Coastal jets have
also been linked to the transport of Alexandrium spp. along the north eastern coast of England
(Brown et al., 2001) and Karenia to the south west of England (Vanhoutte-Brunier et al.,
2008) and the west of Ireland (O’Boyle and Raine 2007). A recent study of Dinophysis acuta
and their transport along the south coast of Ireland showed a direct link between a high
density population in a thin sub-surface layer within a coastal jet (Farrell et al., 2012). These
Dinophysis species are found in high densities in surface layers in summer but throughout the
rest of the year they have very low cell densities (Xie et al., 2007).
For these blooms to initiate and for the coastal jets to operate, seasonality is very important .Data
collected from the June survey showed very low cell counts, with highest cell densities of around
300 cells L-1
. At this time of year the water column is not yet fully stratified and surface water
temperatures are quite low at 11-13 °C. Over the course of one month the water column was
observed to have heated up substantially. Surface waters were 13-16 °C and the pynocline was
well developed forming a mixing barrier between cool dense bottom water and the warm less
dense surface waters. Cell concentrations of D. acuta were recorded of 6,900 cells L-1
around the
Celtic Sea Front area.

24
The data suggest that in July Dinophysis spp. bloom in areas where there are coastal jets
which then transport them over the continental shelf to location where wind driven exchanges
transport them into bays around the south and south west of Ireland. The tidal currents in
these bays are quite weak (<5cms-1
) so the circulation in these bays is mainly driven by wind
due to the bays being axially aligned to the prevailing wind direction (Raine et al., 2010). As
the water column in these summer months has stratified, variations in the axial wind vector
cause a two layer oscillatory flow, which results in an exchange of water from the continental
shelf accompanied with toxic phytoplankton (Edwards et al., 1996). An influx of warm
surface water into the bays from the shelf is characteristic of Dinophysis species (Raine et al.,
2010). The results would indicate the Celtic Sea Front as the source of D. acuta and D.
acuminata but it is hard to state the exact location of the bloom initiations due to
concentrations of Dinophysis being found in other areas as well as the Celtic Sea Front area.
The data collected from stations 71-83 (July cruise) on the transect which goes from stratified
to mixed waters showed strong populations of D. acuta on the stratified side, and samples
taken away from the frontal area showed lower densities. Samples taken from stations 83-98
(July cruise) also showed high cell counts from the frontal region and the further away from
the front the cell numbers decreased. The data from the June cruise from the same area
showed low cell numbers so it is tempting to indicate that the Celtic Sea Front is the source of
these Dinophysis populations. The high number of Dinophysis cells observed from stations on
the warm stratified side of the Celtic Sea front would indicate that this is the where the
blooms develop. The supply of nutrients and light at this region would at this time of year
favor growth of phytoplankton. It is also tempting to consider the coastal jets as their source
of origin also due to high numbers of cells being observed. It is also possible that the
populations develop as they are being transported within the coastal jets along the coast.
The population of D. acuta in particular was extremely high in areas around stations 83-85.
The cells here were healthy and the frontal regions provide a readily available supply of
food/biomass. Note that these cells should be classified as protists, not plants. HABs arise
through either the existence of an indigenous in bays, or the advection of phytoplankton into
bays. The results strongly suggest that with Dinophysis, blooms develop at the Celtic Sea
front and are then transported into bays of south west Ireland, initially in coastal flows and
then through wind-driven water exchanges.

25
CHAPTER 6 : CONCLUSION
The main aim of this project was to investigate the distribution of toxin producing
phytoplankton Dinophysis and attempt to identify their source in coastal and shelf waters in
the Northern Celtic Sea. With regards to populations of Dinophysis cells it was found that
their distribution was limited tn changing water column temperatures and the development of
density fronts. Cell densities were found to have increased by more than 10 fold between June
and July in the survey region. The highest distribution was concentrated near the Celtic Sea
Front between stations 83-86 at depths of around 30m where they were recorded at 6,900 cells
L-1
in July (16th
). In that same area a month earlier they had a cell density of 300 cells L-
1
.With regards to their source it is difficult to identify exactly the origin of where these
blooms initiated. The Celtic Sea Front is a likely source for the origin of these Dinophysis
blooms but realistically further research would need to carried out in order to confidently
label this region as the source. It is likely that the Celtic Sea Front area helped these
populations flourish once they reached the vicinity due to the availability of light and
nutrients and warm sea temperature promoting phytoplankton blooms.
The implications of the presence of Dinophysis is of great importance for the shellfish
industry, with the rope mussel cultivation in particular is worth over 47 million euro to Irish
aquaculture. It is the largest sector in terms of tonnage and only second in value next to
salmon. Dinophysis, particularly the species D. acuta and D. acuminata are well known to
cause a variety of illnesses in humans once they consume shellfish that has been contaminated
with these biotoxin producing phytoplankton. The most common type of sickness is the
gastrointestinal disorder Diarrheic Shellfish Poisoning (DSP). These HABs have proven to be
problematic for aquaculture bays around the south and south west of Ireland for decades.
Further investigations, perhaps further sampling within the region between June, where
Dinophysis numbers are quite low and July where populations were observed in high numbers.
Sampling along the coastal shelf of Ireland where the coastal jets operate during this time
period would assist in the tracking the origin and transport path. Nutrient sampling within
these regions could help in tracking bloom initiation as it is important to track the availability
of nutrients at different times of the year in relation to population growth. Due to the impact
these blooms have annually around south/southwest Ireland, a prediction model for tracking

26
Dinophysis populations is important in order to prepare these farms for oncoming toxic
phytoplankton.
So to conclude, a significant increase in water temperature over the course of the month
induces stratification allowing the coastal jets to now operate and act as a transport pathway
for Dinophysis populations. They get transported in these jets along the continental shelf
where they get potentially blown into bays around the south and south west of Ireland by
wind driven exchanges. The exact origin of Dinophysis, remains unknown but in areas where
there are coastal jets in operation (Celtic Sea Front) the populations can multiply to large
numbers due to the availability of light, nutrients and the now warm stratified water column.

27
ACKNOWLEDGEMENTS
I would like to thank my supervisor Dr. Robin Raine for his constant assistance throughout
this project, the resources he made available and his guidance through to its completion. Also
many thanks to the captain and crew of the R.V. Prince Madog who without their help this
survey would not have been possible. A big thank you is due to Sheena Fennell for her help
both on the survey and back in NUIG, taking time out of her schedule to answer questions and
proof read this project. I would also like to thank Annette Wilson for her support and advice
throughout this project.

28
REFERENCES
Brown, J., Carrillo, L., Fernand, L., Horsburgh, K. J., Hill, A. E., Young, E. F., & Medler, K.
J. (2003). Observations of the physical structure and seasonal jet-like circulation of the Celtic
Sea and St. George's Channel of the Irish Sea.Continental Shelf Research, 23(6), 533-561.
Edwards, A., Jones, K., Graham, J.M., Griffiths, C.R., MacDougall, N., Patching, J.P.,
Richard, J.M., Raine, R.. 1996. Transient Coastal Upwelling and Water Circulation in Bantry
Bay, a Ria on the South-west Coast of Ireland. Estuar. Coast. Shelf Sci. 42, 213-230.
Farrell, H., Gentien, P., Fernand, L., Lunven, M., Reguera, B., Gonzalez-Gil, S., & Raine, R.
2012. Scales characterising a high density thin layer of Dinophysis acuta Ehrenberg and its
transport within a coastal jet. Harmful Algae, 15, 36-46
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Palma, A. S., Vilarinho, M.G., Moita, M.T., 1998. Interannual trends in the
longshoredistribution of Dinophysis off the Portuguese coast, p. 124–127. In: Reguera, B.,
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range model for the prediction of harmful algal events in the bays of southwestern Ireland. J.
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stratified systems: the case study of Ireland. Deep-Sea Research II. 101, 21-31
Reguera, B., Mariño, J., Campos, M.J., Bravo, I., Fraga, S., Carbonell, A., 1993. Trends in
theoccurrence of Dinophysis spp. in Galician Waters, p. 559–564. In: Smayda, T. J., Shimizu,
Y.,[Eds.], Toxic phytoplankton blooms in the sea. Elsevier Science.
Vanhoutte-Brunier, A., Fernand, L., Menesgun, A., Lyons, S., Gohin, F., Cugier, P.,
2008. Modelling theKarenia mikimotoibloom that occurred in the western
English Channel during summer 2003. J. Ecol. Modelling 210, 351–376.
Wyatt, T., 2014. Margalef's mandala: are view. Deep-Sea Res. II 101, 32–49

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Van Egmond, H. P., Aune, T., Lassus, P., Speijers, G.J.A., Waldock, M., 1993. Paralytic
anddiarrhoeic shellfish poisons: occurrence in Europe, toxicity, analysis and regulation. J.
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