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ESTUARY - BIOTIC

The phytoplankton community is dominated by Chaetoceros, which account for about 50% of total abundance. This is a predictable result as diatoms bloom in spring months when the water column is well-mixed time as they can tolerate turbulent water unlike many dinoflagellates (Widdecombe, et al., 2010). Moving southwards through Carrick Roads into an increasingly saline and variable environment, there was a reduction in species abundance (Fig. 3, 4, 5). These findings are representative of a classic estuarine model in which few specialized phytoplankton species dominate. A species of interest with a significantly high percentage was Alexandrium minutum. There is a history of toxic algal blooms in the Fal due to hypernutrification. A. minutum produces SXT, which through bioaccumulation can cause Paralytic Shellfish Poisoning (Perez-Blanco, et al., 2008).

Figure 1: Total phytoplankton abundance as percentage across all 7 stations

Figure 2: Phytoplankton abundance as percentage at Station 2

Figure 3: Phytoplankton abundance as percentage at Station 5

Figure 4: Phytoplankton abundance as percentage at Station 7.

ZOOPLANKTON

Figure 5: Total zooplankton abundance as percentage across stations 1, 4 and 7.

The zooplankton community is dominated by Copepoda nauplii and Copepoda. This could be because they are temperature dependant, hence why there are so many at the surface. The recent warm air temperatures could also be leading to a slightly earlier population peak in July. They are very motile within the viscous layers they live in, this is because they are small and live in a low Reynolds number environment. They are also capable of a “burst” movement, their motility is key to their success as planktivorous zooplankton (Mallin, 1991).

PHYTOPLANKTON

References

Mallin, M., 1991. Zooplankton Community Structure and Abundance in a Mesohaline North Carolina Estuary. Estuaries, 14(4), pp. 481-488.

Perez-Blanco, E., Lewis, J. & Aldridge, J., 2009. The germination characteristics of Alexandrium minutum, a toxic dinoflagellate from the Fal estuary (UK). Harmful Algae, February, 8(3), pp. 518-522

Widdecombe, C. et al., 2010. Long-term phytoplankton community dynamics in the Western English Channel.. Journal of Plankton Research, May, 32(5), pp. 643-655