Gerry Salamena, Michael Kingsford and Tiff any Sih

Kirby Cruise: The infl uence of Ɵ de on abundance of zooplankton off Townsville, Australia Gerry Giliant Salamena, Michael J. Kingsford and Tiff any Sih Wikipage: hƩ p://www.nf-pogo-alumni.org/~Gerry+Salamena

Gerry is a fi rst year MSc student in School of Earth and Environmental Science at James Cook University, Australia. His research interests include physical oceanography (ocean circulaƟ on by using MOHID model) and an invesƟ gaƟ on of ENSO and monsoons in determining the magnitude of upwelling in the Banda Sea.

The characterisƟ cs of the environment off North Queensland are mainly dominated by Ɵ des (Figure 1). Consequently, this physical regime can play a signifi cant role in infl uencing biological aspects in this area (Duggan et al., 2008). In Northern Queensland, secondary producƟ on is dominated by calanoid copepods with remarkable abundance (Duggan et al., 2008). Therefore, the relaƟ onship between Ɵ de and this secondary producƟ on becomes an interesƟ ng study not only for fi shery 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 invesƟ gate infl uences of the characterisƟ cs of the Ɵ de-dominated estuary on the calanoid copepod community off shore Townsville (Cleveland Bay). This cruise was led by Professor Michael J. Kingsford, an 3 shows the abundance of the large calanoid cope

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 observaƟ onal staƟ ons which are inner (near), mid and outer (far) staƟ ons, represenƟ ng posiƟ ons towards coasts where Ɵ de is prevailing. In this cruise, CTD measurements were used to invesƟ gate water mass movement due to Ɵ des while the copepods were sampled by using methodology of Kingsford and Murdoch (1998). Furthermore, abundance of copepods was esƟ mated through subsampling process and counƟ ng process of planktonic cells under microscope. Results of this cruise are given as follows. Figure 2 shows water movement during Ɵ dal stages (i.e. fl ood to high, high to ebb, ebb to low and low to contour of salinity represents how water enters or moves out the Cleveland Bay. Furthermore, Figure fl ood stages) as represented by salinity profi les. The pods aŌ er counƟ ng process. Overall, abundance of the large calanoid copepods off Cleveland Bay was signifi cant during fl ood Ɵ de rather than during ebb Ɵ de. However, this paƩ ern did not match with near staƟ on located close to the coast where freshwater input was dominant. High concentraƟ ons of the large calanoid copepod during fl ood Ɵ de are physically caused by verƟ cal Ɵ dal migraƟ on behaviors of plankton (Kimmerer, et al., 2014). These verƟ cal Ɵ dal migraƟ on behaviors for verƟ cal distribuƟ on (in water column), as reported by Kimmerer et al. (2014), show that center of mass of parƟ cles fl oaƟ ng in the seawater (e.g. plankton) tends to be mostly higher during fl ood Ɵ de and thus parƟ cles will ascend to the surface layer (Kimmerer et al., 2014). As a result, the calanoid copepods with this Ɵ dal migraƟ on behavior will be more abundant in the surface layer during fl ood Ɵ de. In contrast, the central mass of fl oaƟ ng plankton is relaƟ vely lower during the ebb Ɵ 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 Ɵ des. Furthermore, verƟ cal migraƟ ons of plankton related to Ɵ dal stages are described by the iniƟ al posiƟ on of plankton which is in the deeper layer at the beginning of fl ood stage (Kimmerer et al., 2014). Then, it moves to the shallow layer from the late fl ood to the beginning of the ebb stage and it sinks to the deeper layer again at the late ebb stage ( In conclusion, it c a infl uence of Ɵ dal st lanoid copepods, t h in ocean systems, o The fl ood Ɵ dal stag of the copepods w the opposite eff ect abundance of cope as reported by Kimm

Figure 3 - The large calanoid copepods distribuƟ on related to Ɵ de

- The region of study: Australian - The region of study: Australian Ɵ de- and Ɵ de- and minated coastal systems (from Duggan et minated coastal systems (from Duggan et ), Queensland region and the area of inter), Queensland region and the area of interhe Kirby Cruise.e Kirby Cruise.

Kimmerer et al., 2014). an be seen that there is a strong ages on the abundance of the cahe secondary level of producƟ on off Cleveland Bay, off Townsville. ge provides signifi cant abundance while the ebb Ɵ dal stage shows t. This contribuƟ on of Ɵ de to the epods is due to verƟ cal migraƟ on merer et al. (2014).

References

Duggan, S.; McKinnon, A.; Carleton, J., 2008. Zooplankton in an Australian tropical estuary. Estuaries and Coasts, 31(2): 455-467. Kimmerer, W.J.; Gross, E.S.; MacWilliams, M.L., 2014. Tidal migraƟ on and retenƟ on of estuarine zooplankton invesƟ gated using a parƟ cle-tracking model. Limnol. Oceanogr. 59(3): 901-916. Kingsford, M.J.; Murdoch, R., 1998. Planktonic Assemblages. In M.J. Kingsford; BaƩ ershill, C. (Eds.), Studying Temperate Marine Environments: A handbook for ecologists (pp.227-268). University of Canterbury, New Zealand: Canterbury University Press. (Reprinted from: 2000, 2003).

Figure 2 - Cross secƟ on of salinity of the observaƟ on staƟ ons on 2 March 2014. This salinity paƩ ern is used to show water movement in each of Ɵ dal stages including, from top leŌ : fl ood to full, full to ebb, ebb to low and low to fl ood.