Southampton University Falmouth 2015

Group 13

© B Carter

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The community structure of phytoplankton is a valuable resource in assessing estuarine systems. This is due to their rapid and pronounced responses to a range of important factors, such as water mass mixing, light, temperature, turbulence, salinity and nutrients (Brogueira, 2007).

Sample one has a greater diversity, with 17 species being identified compared to 14 in sample two. In sample one, the dominant plankton group is Chaetoceros sp. This is expected as they are the largest genus of marine diatoms. It was not possible to define the individuals seen to species level as distinguishing between the species is notoriously difficult (Von Quillfeldt, 2001). However, in sample two the numbers of Chaetoceros sp are amongst the lowest group seen. It is interesting that Rhizosolenia alata and Guinardia delicatula (Both diatoms) are found in high concentrations in each sample.

Phytoplankton

Zooplankton

The zooplankton net was deployed at site 45G, which was the last site sampled near black rock. 1L of seaweater was collected on the Bill Conway for subsequent analysis of species in the laboratory. 10ml of the sweater samples was poured into a Bogorov chamber and studied under a light microscope. The most dominant taxa observed in the 10 ml sample was Copepoda which accounted for 68% of total taxa observed. Decapoda larvae was the second highest taxa accounting for 13% of zooplankton identified. The other 19% were made up from; Hydromedusae, Mysidacea, Cirripedia, Copepoda nauplii and Barnacles.    

References

Brogueira, M., Oliveira, M. & Cabeçadas, G. Phytoplankton Community Structure Defined By Key Environmental Variables in Tagus Estuary, Portugal. Marine Environmental Research 64, 616-628 (2007).

Von Quillfeldt, C. Identification of Some Easily Confused Common Diatom Species in Arctic Spring Blooms. Botanica Marina 44, (2001).

Stations  39, 40, 41 were the only stations to show high chlorophyll concentrations that showed a notable change with depth.  In station 39, chlorophyll levels decreased at mid depth most probably due to decreased oxygen and nutrients in the water column.  However, station 41 shows the opposite to station 39, which is probably due to increased nutrients in clines moving through the estuary.  The other stations had very little variation in chlorophyll levels, with not very high chlorophyll levels.  There are a number of reasons that may cause this, such as cold temperatures, decreased nutrients, or little sunshine.

Figure 45- Graph showing Flourometry against depth

Figure 46 - Pie Chart showing phtyoplankton present in sample 1

Figure 47 - Pie chart showing phytoplankton present in Sample 2

Figure 48- Pie Chart showing Zooplankton present in sample 1

Chlorophyll

Biological Analysis