Zooplankton effects on dinoflagellates vertical migration

Popular Abstract

Zooplankton effects on dinoflagellates vertical migration
Diel vertical migration (DVM) is the term used to describe the vertical migration of living organisms up and down along the water column and is common in freshwater and marine environments. This movement is associated to, but not limited to organisms such as: phytoplankton, meso-zooplankton and zooplankton (Bollens et al., 2011). This can be driven by biological factors such as: feeding, reproduction and predation and non-biological factors such as light and transparency (Bollens et al., 2011). This is believed to be the main mechanism controlling movement of dinoflagellates to the surface for photosynthesis during light and to the bottom for nutrient uptake during dark period (Eppley et al., 1968, Kimura et al., 1999 and Jephson and Carlsson 2009). Some studies have shown that, temperature and salinity can affect the vertical migration of dinoflagellates (Jephson and Carlsson 2009 & 2011).
Method
A laboratory experiment were performed using a copepod (Acartia tonsa) as the predator and a dinoflagellate (Heterocapsa triquetra) as the prey, using 6 Plexiglas cylinders (2 m high and 0.15 m diameter). The aim was to see how the presence or absence of the copepod influences the distribution of the dinoflagellate along the cylinders during three consecutive light/dark cycles, at 10o C. The experiment were conducted for a period of 4 days with sample collection interval 12hrs beginning from 13:00 on first day and 01:00 mid night on the last day. The control had only empty cages while the treatments consisted of copepods in net cages hanging at the same depths i.e. 70-80 cm. To achieve this, six cages were prepared using 150µm plastic net which was glued onto 160ml plastic culture flask where large parts of the sides had been removed, and immersed in water for several weeks to wash out possible toxic substance from the glue. All dinoflagellate cells sample were counted using and inverted microscope.
Result
The analysis showed that there was a significant treatment and treatment*zone effect in a 3-way ANOVA, and hence I reject the null hypothesis that the presence of copepods do not affect the vertical positioning of dinoflagellates. I observed that presence of copepods in the treatment did hinder the dinoflagellates from swimming to the surface hence high cell concentration from zone 3 and 2. In the control setup with no copepods, only empty cages positioned at the same depth along the water column with a light intensity of 17µmole photons m-2s-1. I observed the vertical distribution of dinoflagellates did not show any difference in zones as showed by the 2-way ANOVA. The Post Hoc test followed by Least Significant Difference (LSD’s) test was performed for the treatment samples since was P<0.001 indicating a variation, as to determine the variation between zone and a vertical distribution ratio of zone 3>2>1 was obtained with 1, 2 and 3 which represents above, at cage and below cage respectively for the experimental setup.
My understanding on how the presence or absence predator may affect the distribution of their prey can be of advantage when dealing with bloom condition trying to keep an aquatic ecosystem from unwanted species by introducing an appropriate predator in the system.
Advisor: Per Carlsson (PhD)
Master´s Degree Project 60 credit in Aquatic Ecology* 2016
Department of Biology, Lund University

• author: Gwe, Jery
• supervisor: Per Carlsson
• organization: Degree Projects in Biology
• course: BIOP35 20142
• year: 2016
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 8835366
• date added to LUP: 2016-03-04 09:44:29
• date last changed: 2016-03-04 09:44:29