offshore

							Intro

The offshore boat work was carried out to investigate the chemical, physical and biological processes
occurring spatially within the water column from the mouth of the Fowey estuary along the south
coast of Cornwall to the mouth of the Fal estuary. Coastal regions are diverse areas with complex
habitats and environments which are also influenced by the proximity to human populations along
the coastline (Jahnke et al., 2008). The aim of the offshore investigation is to use a combination of
instruments to observe the vertical mixing processes affecting the planktonic communities occurring
within the water column. From previous studies it is known that there is summer thermal
stratification in the English Channel (Smyth et al., 2010). Looking at the stratification of the water
column gives the physical properties, which can be linked to the distribution of phytoplankton which
are expected to be in high abundance around the thermocline (Smyth et al., 2010) as at this depth
there is a compromise between high solar radiation and the availability of nutrients which decrease
in the upper water column over the summer months due to the thermal stratification and being
depleted during the spring phytoplankton bloom (Obata et al., 1996). The zooplankton populations
are expected to occur in the highest abundance below the phytoplankton, avoiding prey from above
as well as feeding on the phytoplankton. Dissolved oxygen gives an indication of the balance
between autotrophy and heterotrophy whilst phosphate and silicon were also collected to observe
the vertical mixing of the chemical processes occurring along the Cornwall coastine.

Method

The investigation took place from RV Callista on 05 July 2011. Cast off from Prince of Wales Pier was
at 0735 GMT and the ADCP was started at 0804 GMT. There was then travel time of approximately 2
hours to the first station which was along the coast to the east of Falmouth. The weather began as
overcast with occasional drizzle and improved to sunshine with intermittent cloud cover after 1200
GMT. The wind in the morning was 12-15 mph with gusts up to 22mph dropping to 10-12 mph with
gusts of 15mph in the afternoon.

The ADCP was continually run between stations and at stations throughout the investigation. Five
CTD stations were taken between Fowey and Falmouth. Zooplankton was collected at station 1, 2, 3
and 5 using a zooplankton net and a Bongo net at station 3. Phytoplankton, dissolved oxygen,
phosphate and chlorophyll were collected by a Niskin bottle at each station.

Station Location (Lat and Long) Time (GMT) Depth (m)
   1         50° 17.700 N          1040      23.3
            004° 37.639 W                     0.0
   2         50° 19.172 N          1050      15.0
            004° 38.593 W                     0.0
   3         50° 15.520 N          1204      28.0
            004° 41.775 W                     0.0
   4         50° 13.571 N          1337      19.0
            004° 47.002 W                     0.0
   5         50° 13.016 N          1341      20.0
            004° 47.124 W                     0.0
   6         50° 08.705 N          1549      23.0
            005° 01.450 W                     0.0
References

Smyth, T.J., Fishwick, J.R., Al-Moosawi, L., Cummings, D.G., Harris, C., Kitidis, V., Rees, A.,
Martinez-Vincente, V. and Woodward, E.M.S. 2010, ‘A broad spatio-temporal view of the
Western English Channel observatory’, Journal of Plankton Research, 32, 585-601

Obata, A., Ishizaka, J. and Endoh, M. 1996, ‘Global veification of critical depth theory for
phytoplankton bloom with climatological in situ temperature and satellite ocean color data’,
Journal of Geophysical Research, 101, 20657-20667.

Jahnke, R.A., Roman, M.R. and Brink, K.H. 2008, ‘Coastal Ocean Processes Program’,
Oceanography, 21, 18-21.




 Time                                                   Depth
 GMT                           LAT N       LONG W        (m)
 07:35           cast off
 08:04       start ADCP 000   50 08.164   005 00.104
 10:40          station 1     50 17.700   004 37.639    23.3
 10:40                                                   0
 10:50       end ADCP 001     50 17.871   004 37.643
 10:50       start ADCP 002   50 17.871   004 37.643
 10:50          station 2     50 19.172   004 38.593     15
 10:50                                                    0
             end 002 start
 11:04            003         50 19.172   004 38.593
             end 003 start
 11:34            004         50 19.092   004 38.730
 12:04         station 3      50 15.520   004 41.775     28
 12:04                          start        stop         0
 12:04          bongo          31100        31715
 12:04         (100um)          1251        1257
             end 005 start
 13:08            006         50 14.827   004 42.046
             end 006 start
 13:32            007         50 13.571   004 47.002
 13:37         Station 4      50 13.571   004 47.002     19
 13:41         Station 5      50 13.016   004 47.124     20
                end 007 start
 13:41               008           50 13.016    004 47.124          0
                end 008 start
 13:56               009           50 12.859    004 49.054
                end 009 start
 14:34               010           50 12.423    004 48.968
                end 010 start
 15:37               011           50 08.705    005 01.450
 15:49            station 6        50 08.705    005 01.450         23
 15:49                                                              0
 16:15             end 11          50 08.998    005 01.715




http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/21_4/21.4_jahnke_intro.pdf



JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 101, NO. C9, PAGES 20,657-20,667, SEPTEMBER 15, 1996
Global verification of critical depth theory for phytoplankton
bloom with climatological in situ temperature
and satellite ocean color data
Atsushi Obata


JOURNAL OF PLANKTON RESEARCH    j VOLUME 32 j NUMBER 5 j PAGES 585–601 j 2010
A broad spatio-temporal view of the
Western English Channel observatory
TIMOTHY J. SMYTH*, JAMES R. FISHWICK, LISA AL-MOOSAWI, DENISE G. CUMMINGS, CAROLYN HARRIS,
VASILLIS KITIDIS, ANDREW REES, VICTOR MARTINEZ-VICENTE AND ERNEST M. S. WOODWARD