The views and opinions expressed in this website are not necessarily those expressed by the National Oceanography Centre or the University of Southampton. The opinions and views expressed are those of the authors of the website

At stations 69A, the most abundant zooplankton population was that of the copepods which had a population of 42.19 indiv./m-3; furthermore, the copepod population was the second most abundant at station 74G and 72E, with a population of 28.19 and 12.53 indiv./m-3. The second most abundant population of station 69A was that of the copepod nauplii, which had a population of 22.34 indiv./m-3; in addition, the copepod nauplii had the most abundant population at station 74G, with a population of  34.45. For station 72E, the most abundant population was that of the hydromedusae, with a population of 28.19 indiv./m-3. Station 69A had the lowest diversity of zooplankton populations as it only contained three different populations, while the other two stations contained five different populations.

The purpose of this survey was to assess the biology of the Fal estuary from the Truro River to Black Rock. This included phytoplankton as well as their predators, zooplankton. By evaluating the plankton in the laboratory more closely,  we could evaluate their distribution along the estuary, as well as the population composition at the time and location of sampling. The chlorophyll levels at changing depth were also investigated

At station 69A, the most abundant phytoplankton population was that of the tintinnid which had a population of 150 indiv./m-3; furthermore, this population was also most abundant at station 75G with a value of 170 indiv./m-3. At station 71D, the most abundant population was that of the skeletonema which had a population of 100 indiv./m-3; whereas, station 72E, the most abundant population was that of the Ciliate which had a population of 40 indiv./m-3. Interestingly, at station 72E, the most abundant populations were recorded in the ciliates and the leptocylindrus which both had populations of 290 indiv./m-3. Station 75G had the most diverse phytoplankton populations, with six different populations being recorded; in comparison, stations 69A and 73F had the least diverse phytoplankton populations, with only three different populations being recorded in each.

Biology of the Estuary

Zooplankton

Phytoplankton

The majority of the stations show that chlorophyll decreases with depth below approximately 10m. The stations also show an increase in chlorophyll from the surface to a maximum at a certain depth; between 5 and 15m. This trend arises because at the surface nutrients are depleted due to biological uptake and increases with depth. The depth of maximum chlorophyll is the point at which there is enough light for photosynthesis and a necessary amount of nutrients for growth. However, stations 71D, 70C, and 75D show a decrease from a maximum at the surface to a minimum at depth.  

Chlorophyll

Figure 4.0  A stacked column chart showing the zooplankton abundances and distribution across three stations from the Fal Estuary

Figure 4.1  A stacked column chart showing the phytoplankton abundances and distribution across five stations from the Fal Estuary

Figure 4.2 Depth Profile of Esturarine Cholorphyll at seven stations