NANO ALUMNI IN THE FIELD Kirby Cruise: The influence of de on abundance of zooplankton off Townsville, Australia Gerry Giliant Salamena, Michael J. Kingsford and Tiffany Sih Wikipage: h p://www.nf-pogo-alumni.org/~Gerry+Salamena
Gerry is a first year MSc student in School of Earth and Environmental Science at James Cook University, Australia. His research interests include physical oceanography (ocean circula on by using MOHID model) and an inves ga on of ENSO and monsoons in determining the magnitude of upwelling in the Banda Sea.
T
he characteris cs of the environment off North Queensland are mainly dominated by des (Figure 1). Consequently, this physical regime can play a significant role in influencing biological aspects in this area (Duggan et al., 2008). In Northern Queensland, secondary produc on is dominated by calanoid copepods with remarkable abundance (Duggan et al., 2008). Therefore, the rela onship between de and this secondary produc on becomes an interes ng study not only for fishery management off North Queensland at the large scale but also for gaining knowledge in oceanography studies. A project called the “Kirby Cruise project” was conducted to inves gate influences of the characteris cs of the de-dominated estuary on the calanoid copepod community offshore Townsville (Cleveland Bay). This cruise was led by Professor Michael J. Kingsford, an oceanographer from James Cook University, where I am studying my master degree in Environmental Marine Science. This cruise was held on March, 2 and 5, 2014. I was involved in this cruise as a part of my core subject for the program. Figure 1 shows the three observa onal sta ons which are inner (near), mid and outer (far) sta ons, represen ng posi ons towards coasts where de is prevailing. In this cruise, CTD measurements were used to inves gate water mass movement due to des while the copepods were sampled by using methodology of Kingsford and Murdoch (1998). Furthermore, abundance of copepods was es mated through subsampling process and coun ng process of planktonic cells under microscope. Results of this cruise are given as follows. Figure 2 shows water movement during dal stages (i.e. flood to high, high to ebb, ebb to low and low to flood stages) as represented by salinity profiles. The contour of salinity represents how water enters or moves out the Cleveland Bay. Furthermore, Figure
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3 shows the abundance of the large calanoid copepods a er coun ng process. Overall, abundance of the large calanoid copepods off Cleveland Bay was significant during flood de rather than during ebb de. However, this pa ern did not match with near sta on located close to the coast where freshwater input was dominant. High concentra ons of the large calanoid copepod during flood de are physically caused by ver cal dal migra on behaviors of plankton (Kimmerer, et al., 2014). These ver cal dal migra on behaviors for ver cal distribu on (in water column), as reported by Kimmerer et al. (2014), show that center of mass of par cles floa ng in the seawater (e.g. plankton) tends to be mostly higher during flood de and thus par cles will ascend to the surface layer (Kimmerer et al., 2014). As a result, the calanoid copepods with this dal migra on behavior will be more abundant in the surface layer during flood de. In contrast, the central mass of floa ng plankton is rela vely lower during the ebb de and therefore the zooplankton will sink from the surface layer (Kimmerer et al., 2014). Thus, there will be less abundance of the calanoid copepod in the surface layer during the ebb des. Furthermore, ver cal migra ons of plankton related to dal stages are described by the ini al posi on of plankton which is in the deeper layer at the beginning of flood stage (Kimmerer et al., 2014). Then, it moves to the shallow layer from the late flood to the beginning of the ebb stage and it sinks to the deeper layer again at
Figure 1 wave-do al., 2008 est for th
the late ebb stage ( In conclusion, it ca influence of dal st lanoid copepods, th in ocean systems, o The flood dal stag of the copepods w the opposite effect abundance of cope as reported by Kimm
Figure 3 - The large calanoid copepods distribu on related to de
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