University of Southampton OES Undergraduate Falmouth Field Course 2016 - Group 3 databank and initial findings.
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Phytoplankton
As has been described previously, 24 different species of phytoplankton were observed across 4 data collection sites along the Fal estuary. However, the only species’ to be observed at all 4 sites were of the genus’ Chaetoceros and Leptocylindrus. These genus’ are centric diatoms, and as a result possess silicon frustules to provide protection against predation, which may allow them to dominate estuarine waters (Phyto’pedia, 2012). The genus Chaetoceros is tolerant of an extremely large range of salinities (19-38) and temperatures (2°C-29°C), whereas the genus Leptocylindrus prefers a narrower range of temperatures (15°C-20°C) (Phyto’pedia, 2012). Physical data suggests that both species were able to tolerate the Fal estuarine waters around the date of data collection, and with defensive mechanisms present these species are suited to dominating phytoplankton populations in the Fal estuary, albeit only in warmer months in the case of Leptocylindrus. This would explain the presence of these genus’ at all 4 sites. The highest concentrations of phytoplankton were present at site D28, which was in close proximity to a large barge. A possible explanation of this is the leach of some nutrients from the barge into the surrounding water column, driving photosynthesis and allowing higher concentrations of phytoplankton.
Zooplankton
Copepods and their larvae (Nauplii) were
found to be the dominant zooplankton genus’
within the Fal estuary across all 3 zooplankton trawls. Copepods are advantaged in
their motility, allowing them to actively hunt in estuarine waters. Copepods are
also able to hunt phytoplankton with silicon frustules, such as the centric diatoms
identified above as dominant in the estuary. These adaptations will enable copepods
to thrive in the waters of the Fal estuary, and this may thus explain their dominance.
A significantly higher proportion of echinoderm larvae were present compared to total
zooplankton concentrations using samples from the third trawl, from the mouth of
the Fal estuary back into Falmouth harbour past “Black Rock”. A possible theory for
this increased echinoderm larvae concentration is the utilisation of the hard structures
of “Black Rock” and the harbour as habitat by Echinoderm species, which would increase
their concentrations in these regions. An increased presence of Echinoderm individuals
should also result in an increased concentration of Echinoderm larvae, which may
explain this observation.
Estuary sampling - Biological Data
References
ERA Biotech, (2016). [online] Marinebiotech.eu. Available at: http://www.marinebiotech.eu/c/images/thumb/1/15/Calanus_finmarchicus.jpg/250px-Calanus_finmarchicus.jpg [Accessed 1 Jul. 2016].
Phyto’pedia (2012). “Genus-Chaetocero”. Department of Earth, Ocean and Atmospheric Sciences [Online]. Available at:https://www.eoas.ubc.ca/research/phytoplankton/diatoms/centric/chaetoceros/chaetoceros_ genus.html
Phyto’pedia (2012). “Leptocylindrus danicus”. Department of Earth, Ocean and Atmospheric Sciences [Online]. Available at: https://www.eoas.ubc.ca/research/phytoplankton/diatoms/centric/leptocylindrus/l_danicus.html
Fig 16. Chaetoceros spp (Phyto’pedia 2012) [Click to englarge]
Fig 17. Leptocylindrus spp (Phyto’pedia 2012) [Click to enlarge]
Fig 28. Copepod zooplankton (ERA Biotech 2016)