Southampton University Falmouth 2015

Group 13

© B Carter

Biological Analysis

Figure 11: Group 13 with zooplankton

Figure 10: Zooplankton

© J Tinkler

© B Carter

Zooplankton samples

Figure 13: Zooplankton species in sample 1

Figure 14: Zooplankton species in sample 2

Figure 15: Zooplankton species in sample 3

Phytoplankton samples

Three replicate chlorophyll samples were taken at different depths at three stations.  Each station showed a deep chlorophyll maximum.  The maxima varied with depth and intensity, with the largest maximum at station 68.  Deep chlorophyll maxima are common of vertically stratified waters (Cullen, 1982).  

References

Cullen, J. (1982). The Deep Chlorophyll Maximum: Comparing Vertical Profiles of Chlorophyll a. Canadian Journal of Fisheries and Aquatic Sciences, 39(5), pp.791-803.

Figure 12: Flourometry plot at stations 68, 69 and 71.

The highest levels of diversity were found at stations B and C, with Copepoda and Hydromedusae being common to all stations at a high level of density. Other common groups included polychaete and decapod larvae. All stations show a similar group composition. Stations B and C have the most similar diversity levels. This is due to the nets being taken at similar depths of the chlorophyll maxima (around 35m) to the surface. A lower number of organisms were found at station A, however a significantly greater number of Hydromedusa and Ctenophora were seen. Copepods were consistently high through- out all stations, however, specific diversity cannot be measured as they were not identified to species level. Due to net size of 200um, smaller zooplankton might not have been sampled during the vertical tow.

Figure 16: Graph showing relative abundances of species found at station 68 at  52.6 metres depth.

Figure 17: Graph showing relative abundances of species found at station 68 at  21.8 metres depth.

Figure 18: Graph showing relative abundances of species found at station 68 at  1.4 metres depth.

Figure 19: Graph showing relative abundances of species found at station 69 at  52 metres depth.

Figure 20: Graph showing relative abundances of species found at station 69 at  38.15 metres depth.

Figure 21: Graph showing relative abundances of species found at station 69 at  5 metres depth.

Figure 22: Graph showing relative abundances of species found at station 71 at  47.5 metres depth.

Figure 23: Graph showing relative abundances of species found at station 71 at 13 metres depth.

Figure 24: Graph showing relative abundances of species found at station 71 at  5.31 metres depth.

Disclaimer: The views and opinions expressed are those of the individual and not necessarily those of the University of Southampton or the National Oceanography Centre, Southampton.

The graphs of phytoplankton show a diverse range in species found at the different sites and at different depths. For example, Nitzchia sp. is not recorded in any of the mid-depth samples, but is found in relatively high abundance in both shallow and deep water samples (with the exception of the deep sample for site 68). Highest phytoplankton seems to correspond to the levels of chlorophyll as two of the samples taken at the chlorophyll maxima show highest phytoplanktonic abundance for the station.

The average number of species in each sample is 10.2, station 71 at 13 metres depth has the highest diversity of species (15 unique species), whereas station 69 at 38.15m and station 68 at 1.4m have the lowest with only 7 species each. Chaetoceros sp. is the most ubiquitous phytoplankton found, appearing in all but 2 of the samples taken, however it is not found in particularly high concentrations (an average of 3.3 individuals per sample).